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AMERICAN MUSEUM OF NATURAL HISTORY
Evolution of the Horse
EOHIPPUS, THE FOUR-TOED HORSE
Restoration of the earitest known Ancestor of the nodern Horse, discovered
in the bad lands of Wyoming
NO. 36 OF THE OUIDE LEAFLET SERIES —SEPTEMBER, 1913
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Alter Osborn
SKELETON OF HORSE AND MAN
Mounted for oomparative study. Gift of the late William C. Whitney to the American
Museum of Natural History
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V /> S. fUD
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Evolution of the Horse
No. 1 of the Series to Illustrate
EVOLUTION AMONÜ FOSSIL MAMMALS
AMERICAN MUSEUM OF NATURAL HISTORY
IN TWO PARTS
Evolution of the Horse in Nature
By W. D. MATTHEW
The Horse under Domestication: lts Origin and the
Structure and Qrowth of the Teeth
By S. H. CHUBB
QUIDB LEAFLET SERIES, NO. 36
NEW YORK, riARCH, 1913
PUBLISHED BY THE MUSEUM
Bibiioihcck der
fcjjkiuniversiteit te UtreeH
Afd. Dicrpcnreïkimtfe
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N
NO. 36
OF THE
CUIDE LEAFLET SERIES
O? THE
AMERICAN MUSEUM OF NATURAL HISTORY
THIRD EDITION, REVISED AND ENLARCED
Published under the direction of Henry Fairfield Osborn, President of the Board
of Trustees of the Museum. Curator Emeritus of Fossil Vertebrates
MARY CYNTHIA DICKERSON, Editor
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CONTENTS
Part I. Evolution of the Horse in Nature
Introduction         . .
fossil horses of the aoe of man
evolution of the horse
Four-toed Horses .
Three-toed Horses
One-toed Horses
Conclusions
Meaning of the Change in Feet and Teeth
Cause of the Evoltjtion ....
Parallel Evolution in Other Racer
Part II. The Horse under Domestication
Origin of the Domestic Horse
comparison of the skeleton of horse and man
The Draft Horse......
Development of Great Size in the Draft Horse
The Shetland Pony
The Arabian Horse
The Race Horse
The Teeth of the Horse
Structure of the Teeth
Wear and Compensating Movement of the Ineisors
Designation of the Teeth .....
Wolf Tooth of the Horse . . . . .
Premolars and Molars of the Horse
Eruption of the Teeth of the Horse
Shedding the Teeth .......
Principal Literature on the 'Evoltjtion of the Horse
Index ...........
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LIST OF ILLUSTRATIONS
mg.
Page
Fronlispiece
Skeleton of Horse and Man
Evolution of the Horse           ....
Evolution of the Fore Foot. Principal Stages
Evolution of the Hind Foot. Principal Stages
Upper Teeth, Eohippus           .
Upper Teeth, Orohippus         . . . .
Upper Teeth, Epihippus         . .
Upper Teeth, Mesohippus               .
Little Three-toed Horse (Mesohippus hairdi) and Four-toed Horse
(Eohippus venticolus)
10
11
15
16
16
17
18
19
20
20
21
22
23
24
25
26
27
28
30
32
33
34,35
36
38
38
40
45
47
47
51
53
54
55
56
57
59
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Skeleton of Three-toed Desert Horse (Hipparion whüneyi)
Upper Teeth, Parahippus
Upper Teeth, Meryehippus
Upper Teeth, Hipparion
Upper Teeth, Equus
Skeleton of Extinct American Horse (Equus scoüi)
Skeleton of Short-limbed Horse, Hippidium
Geological and Geographical Range of Ancestors of Horse
Evolution of the Fore Leg. Principal Stages
Evolution of the Hind Leg. Principal Stages
19, 20. Evolution of the Teeth ....
21.     Evolution of the Hind Foot of the Horse .
22.    Fore and Hind Feet. Three-toed Pseudo-horse
23.     Fore and Hind Feet. One-toed Pseudo-horse
24.     Evolution of the Horse .....
25.     Giant Draft Horse and Shetland Pony
26.     Draft Horse Puiling Heavy Load (Skeleton)
27.     Arabian stallion "Nimr" (Skeleton)
28.    Draft Horse. Rear view showing action of pelvis and backbone
29.    Famous American Race Horse "Sysonby'
30.     Incisor Teeth showing different degrees of specializat
31.     Incisor Teeth showing w'ear and movement
32.     Designation of Teeth ....
33.    Wearing Surface of Upper Grinding Teeth
34.     Sections of Upper Grinder of Horse
35.    Lower Premolar of Horse
36.     Deeiduous Molar of Colt
37.    Dental Battery of Adult Horse
38.    Dentition of the Colt .
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PREFACE
Among all the animals of past and present there is none so deserving of our
interest and affection as the horse. It is the most useful of the domestic animals,
and bas played the largest part in the development of civilization. Since the dawn
of recorded history the man with the horse has been in the forefront of progress,
Whether leading the military civilizations of the past or breaking ground for the
industrial civilization of the present the pioneers and leaders of progress have always
made large use of this noble animal. It is not too much to say that without his help
our ancestors in the Old World might have advanced but little further on the road to
civilization than did the inhabitants of the ancient semi-civilized states of Peru and
Mexico, where the horse was unknown, and travel, agriculture and military succcss
were limited by the capacity of unaided human strength.
From another point of view the horse is of pcculiar interest. It is one of the
most perfect machines for swift running that exists among living animals and displays
throughout its organization the most exact and finished mechanism adapted to this
purpose. It is perhaps the finest example of what nature acting through millions
of years, has been able to accomplish in the way of adapting a large quadruped to
speed over long distanees, and likewise of the extent to which man, during the few
thousand years that he has controlled its development, has been able to improve
upon nature, in the sense of adapting it to serve more exactly his own purpose.
The history of this adaptation, continued over millions of years, constitutes the
evolution of the horse. Its records consist of the actual skeletons of the successive
stages in the development of the race. Buried in ancient river deposits, petrified
and preserved to our day in the successive geological strata, they have been discov-
ered and disinterred through the diligent search of scientists during the last fifty
years.
This Museum has taken especial interest in the evolution of the horse. The
records of this history are most completely preserved in the western United States,
and through the liberality of the trustees of the American Museum, and in particular
through special funds provided by the late William C. Whitney, by Professor Henry
Fairfieid Osborn and by other trustees and friends of the Museum, Messrs. James R.
Keene, Randolph Huntington, F. K. Sturgis and others, we have obtained, from
expeditions, gifts and purchases, many thousand specimens of fossil species, illus-
trating numerous successive stages in horse ancestry; and a unique series illustrat-
ing the diverse breeds of the domesticated animal and the structure and growth of
its teeth and skeleton, so marvelously suited to its requirements.
Such parts of the collection as might best serve to illustrate the subject have been
placed on exhibition in the hall of fossil mammals. These exhibits show
1.     The Evolution op the Horse in Nature
2.     The Evolution of the Horse under Domestication
The collections have been gathered together and arranged under the direction
and supervision of Professor Henry Fairfieid Osborn. Scientific deseriptions of parts
of the materiaï have been published from time to time by Professor Osborn and his
assistants and an extensive monograph on the evolution of the horse is now in
preparation.
W. D. Matthew
American Museum of Natuhal HiaTOHY, March, 1913
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THE EVOLUTION OF THE HORSE.
Fore Foot
Formations in Western United States and CharacteristicTypeof HorseinEach
Hind Foot
Recent
Pleistoccno
Quatemary
or
Age of Man
. One Toe
Splints of
2^and f-h<Ii{il3
One Toe
5piinis of
Equus
Pliocenc
louf. êbbk^'
Zz^==^i
H I8K3K
?~3ë
■JOHN DAY
WHiTF. RtVER
= £T |^-3T J3^ =
l-mkïi '•■
Th ree Toes
5ide toes
nol toudiiné ihc óroinid
Th ree Toes
Side foes
i not tOHchinf the^round
Protohippus
Miocene
Tertiary
or
A§e of
Mammals
Th ree Toes
Sitie toes
toMching theground;
«plint «f S'^dijil
Meson ippus
Oli^ocenc
Th ree Toes
.Side toes
touching the grownd
Four Toes
Frotorohippus
m%8 riv f
Eocenc
Four Toes
Splinl of i- digif
'; Th ree Toes
M 5Plint of 5*di#t.
Hyracolherium
(Eohippus)
_,VASATCH_' -
P_ÜERCO".ANi> TQKRFj_0>:
Hypothetical Anceslors with Five Toes on Each Foot
and Teeth like those of Motïkeys etc.
, Crefaceoiis
Jurassic
Triassi^:
Ageof
Rept i les
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Part I. EVOLUTION OF THE HORSE IN NATURE
By W. D. Matthew, Ph.D.
Curator, Department of Vertebrate PalEeontology
INTRODUCTION
A. S a domestic animal the horse is to be found almost evcrywhere that
man can live. He is spread all over the world — from torrid to
arctic climates, in all the continents, in remote oceanic islands —
he is completely cosmopolitan. But as a wild animal the horse is at present
limited to the Old World, and is found there only in the open arid or desert
plains of Central Asia and Africa. There are two species in Asia, the Asiatie
wild ass (Equus hemionus) and the little known Przewalsky horse (Equus
przewalskii), while in Africa there are the African wild ass (Equus asinus) and
the several species of zebra (Equus zebra, Equus burchelli, Equus grevyï).
In the Americas and Australia there are no true wild horses, the mustangs
and broncos of the Western Plains and South America being feral (domesti-
cated animals run wild) and descended from the horses brought over from
Europe by the early white settlers. When the Spaniards first explored the
New World they found no horses on either continent. The Indians were
quite unfamiliar with them and at first regarded the strange animal which
the newcomers rode, with wonder and terror, like that of the ancient Romans
when Pyrrhus and his Greeks brought elephants — " the huge earth-shaking
beasts" — to fight against them.
The horse is distinguished from all other animals now living by the fact
that he has but one toe on each foot. Comparison with other animals shows
that this toe is the third or middle digit of the foot. The hoof corresponds
to the nail of a man or the claw of a dog or cat, and is broadened out to afford
a firm, strong support on which the whole weight of the animal rests. Be-
land the "cannon bone" of the foot are two slender little bones, one on each
side, called "splint bones." These represent the second and fourth digits
of other animals, but they do not show on the surface and there is nothing
like a separate toe. So that the horse may be said to be an animal that walks
on its middle finger nail, all the other fingers having disappeared.
The teeth of the horse are almost equally peculiar. The molars are long,
square prisms which grow up from the gums as fast as they wear off on the
crowns. Their grinding surface exhibits a peculiar and complicated pattern
of edges of hard enamel between which are softer spaces composed of
dentine and of a material called "cement," much like the dentine in quality
but formed in a different way. The dentine is formed on the inside surfaces
of the enamel while the tooth is still within the jawbone; the cement is
deposited on the outside surfaces of the enamel af ter the tooth has broken
through the jawbone and beiore it appears above the gums.
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AMERICAN MUSEUM GUIDE LEAFLETS
Various other
peculiarities dis-
tinguish the horse
from most other
animals; some of
these are shared
by other hoofed
animals. The two
long bones of the
forearm (radius
and ulna) are
separate in the
greater number of
animals, but in
the horse and
in many other
hoofed animals,
they are Consoli-
dated into a sin-
gle bone (See Fig.
17, p. 26). The
same consolidation is seen in the
bones of the lower leg (tibia and
fibula) (See Fig. 18, p. 27). The
lengthening of the foot and step-
ping on the end of the toe raises
the heel in the horse, as in many
other animals, to a considerable
height above the ground, where
it forms the hoek joint, bending
backward, as the knee bends for-
ward. In these as in various
other ways the legs
of the horse are
especially fitted for
swift running over
hard and level
ground, just as its
teeth are fitted for
grinding the wiry
grasses which grow
on the open plain.
FIG. 2. EVOLUTION OF THE FORE FOOT. PRINCIPAL STAGES
(Right to Left)
1.    Four-toed horse Eohippus. Eocene Epoch
2.    Early three-toed horse Mesohippus. Olürocene Epoch
3.    Later three-toed horse Merychippus. Miocene Epoch
4.    One-toed horse Equus. Pleistocene Epoch and Modern
All outside views showing the middle and outer digits of the fore foot. In
Eohippus the two outer toes (digits IV and V) are complete. In Mesohippus, digit V
is reduced to a small splint and digit IV is notably smaller than the middle digit.
In Merychippus, digit V is a tiny nodule of bone and digit IV has become very slender
in comparison with the middle digit. In Equus digit IV is reduced to a long splint,
while of the fifth digit no tracé remains
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FIG. 3. EVOLUTION OF THE HIND FOOT. PRINCIPAL STAGES
(Right to Left) 1. Eohippus, Eocene Epoch; 2. Mesohippus, Oligocene; 3.
Merychippus, Miocene; 4. Equus, Pleistocene and Modern
Outer views showing middle and outer digits. Note progressive reduction of
side toe (digit IV) from a well developed digit to a splint bone                                     11
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POSSIL HORSES OF THE AGE OF MAN
THE Age of Man, or Quaternary Period, is the last and by far the short-
est of the great divisions of geological time. It includes the Great
Ice Age or Glacial Epoch (Pleistocene), when heavy Continental
glaciers covered the northern parts of Europe and North America, and the
Recent Epoch, of more moderate climate during which civilization has arisen.
In the early part of the Quaternary Period, wild species of horse were to
be found on every continent except Australia. Remains of these true native
horses have been found buried in strata of this age in all parts of the United
States, in Alaska, in Mexico, in Ecuador, Brazil and Argentina, as well
as in Europe, Asia and Africa. All these horses were much like the living
species and most of them are included in the genus Equus. Mr. J. W.
Gidley, in charge of the American Museum expedition in northern Texas,
discovered in 1899 a number of more or Iess complete skeletons of a species
of fossil horse, Flquvs scotti, in an old river deposit on Rock Creek in Donley
County. These are the most complete specimens known of the extinct
horses which inhabited this country at the beginning of the Ice Age. A
mounted skeleton and several skulls have been placcd on exhibition, and
their near resemblance to the modern animal appears at a glance. The
differenee from the domestic horse is chiefly in proportions: the skull is
shorter with deeper jaws, the legs rather short and the feet small in pro-
portion to the body. In these charaeters this fossil horse resembles an
overgrown zebra rather than a domestic horse. We know nothing of its
coloring. It may have been striped, and in this case would have been very
zebra-like; but there are some reasons for believing that it was not promi-
nently striped. The bones are petrified, brittle and heavy, the animal
matter of the bone having entirely disappeared and having been partij'
replaced by mineral matter. They are not much changed in color how-
ever, and are so perfectly preserved that they look almost like recent bone.
All the remains of these native horses which have been found in America
have been petrified more or less completely. This means that they have
been buried for many thousands of years, for true petrifaction is an
exceedingly slow process. This condition serves as an easy means of dis-
tinguishing them from bones of the domestic horse, found buried in the
earth. These cannot in any case have been buried for more than three or
four centuries, and have not had time to petrify.
Remains of these fossil horses from various parts of the United States
are shown in the counter cases. One very rich locality is on the Niobrara
River in Nebraska, another is in central Oregon. Many separate teeth and
bones have been found in the phosphate mines near Charleston, South
Carolina; other specimens have come from central Florida, from southern
Texas, Arizona, Kansas, Louisiana and even from Alaska. They are, in
fact, so often found in deposits of rivers and lakes of the latest geological
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EVOLUTION OF THE HORSE IN NATURE                 13
epoch (the Pleistocene) that the formation in the western United States lias
received the name of " Equus Beds."
In South America, in strata of the Pleistocene Epoch, there occurs,
besides several extinct species of the genus Equus, the Hippidium, a pecidiar
kind of horse charactcrized by very short legs and feet, and some peculiari-
ties about the muzzle and the grinding teeth. The legs were hardly as long
as those of a cow, while the head was as large as that of a race horse or other
small breed of the domestic horse.
All these horses became extinct, both in North and South America.
Why, we do not know. It is very probable that man — the early tribes of
prehistorie hunters — played a considerable part in their disappearance,
not indeed by killing them all off directly, but by continual hunting and
chasing, driving them from the best feeding-grounds and interfering with
their habits and opportunities for grazing. This persecution would tend to
reduce their numbers and vigor, and be the prelude to their extinction. ïhe
competition with the bison and the antelope, which had recently migrated
to America, may also have made it more difncult than formerly for the
American horse to get a living. And finally, some epidemie disease or
prolonged season of drought may have exterminated the race. Whatever
the cause, the horse had disappeared from the New World when the white
man invaded it (unless a few individuals still lingered on the remote plains
of South America), and in his place the bison had come and spread over the
prairies of the North.
Fossil horses are equally common in the Pleistocene formations of the
Old World. They have been found in all parts of Europe and Asia, in
North and South Africa, but not in Australasia, the East Indies or Madagas-
car. In Central Asia, two wild races persist to the present day; others were
domesticated by man in the earliest times, and their use in Chaldea and
Egypt for draft and riding is depicted in the ancient mural paintings. In
Africa the larger species became extinct in prehistorie times, as in America
but the smaller zebras still survive in the southern part of the continent
(One species, the quagga, abundant fifty years ago, is now extinct), and the
African wild ass is found in the fauna of the northêrn part. The wild horse
of prehistorie Europe, a small race, short-legged and shaggy-haired, was
domesticated by man, a fact that is known from the rude drawings scratched
on bone or ivory by men of the Neolithic or Polished Stone Age. But the
domesticated horses now in use are derived chiefly from the Asiatic and
African species * although it is probable that in some breeds there is a
considerable strain of this shaggy, short-legged European race. The
domesticated ass is a descendant of the wild ass (Equus asinus) of North
Africa.
1 They are probably derived from three different wild sources which Professor Cossar
Ewart has called the Forest Type of Northern Europe, the Steppe Type of Northern Asia,
resembling the Przewaisky horse, and the Plateau or Desert Type of Northern Africa,
resembling the Arabian.— Henry Fair-field Osborn.
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THE EVOLUTION OF THE HORSE
THE history of the evolution of the horse through the Tertiary Period
or Age of Mammals affords the best known illustration of the
doctrine of evolution by means of natural selection and the adapta-
tion of a race of animals to its environment. The ancestry of this family
has been traced back to near the beginning of the Tertiary without a
single important break. During this long period of time, estimated at
nearly three millions of years, these animals passed through important
ehanges in all parts of the body, but espeeially in the teeth and feet, adapting
thern more and more perfectly to their particular environment, namely the
open plains of a great plateau region with their scanty stunted herbage,
which is the natural habitat of the horse.
In the series of ancestors of the horse we can tracé every step in the
evolution of those marked peculiarities of teeth and feet which distinguish
the modern animal from an ancestor which so little suggests a horse that
when its remains were first found forty years ago, it was named by the great
palajontologist, Richard Owen, the Hyracotherium or "coney-like beast."
Its relation to the horse was not at that time suspected by Professor Owen,
and was reeognized by scientific men only when several of the intermediate
stages between it and its modern descendant had been discovered. On the
other hand this first ancestor of the horse line is very difficult to distinguish
from the contemporary ancestors of tapirs and rhinoeeroses, and indicates
how all the modern quadrupeds have diverged from a single type, each
becoming adapted to the needs of its especial mode of life.
FOUB-TOED HORSES
THE earliest known ancestors of the horse were small animals not
larger than the domestic cat, with four complete toes on each fore
foot and three on each hind foot. There is reason to believe that
the still more ancient ancestors of this and all other mammals had five toes
on each foot. In the fore foot of the earliest known stage there may have
been a small, slender rudiment representing the missing first digit or
thumb, which no longer appeared on the surfaee of the foot,1 while in the
hind foot there is a similar rudiment representing the outer or fifth digit,
and also a tiny remnant of the innermost or first digit. The proportions of
the skull, the short neck and arched back and the limbs of moderate length,
were very little horselike — recalling on the contrary, some modern car-
nivorous animals, espeeially the civets (Vivcrridm). The teeth were short-
crowned and covered with low rounded knobs of enamel, suggesting those
of monkeys and of pigs or other omnivorous animals, but not at all like
the long-crowned complicated grinders of the horse.
1 It is shown in Marsh's well known diagram; but there is no conciusive evidence of its
presence on any specimen yet found.
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EVOLUTION OF THE NORSE IN NATURE                 15
Commencing with the Hyracotherium, twelve stages have been recog-
nized from as many successive formations, showing the gradual evolution
of the race into its modern form, and each stage is characteristic of its
particular geological horizon. Some of the stages have been found in
several parts of the world, but by far the most complete and best known
series comes from the Tertiary Badlands of the western United States.
Besides the main line of descent which led into the modern horses, asses and
zebras, there were several collateral branches which have left no descend-
ants. Of some stages all parts of the skeleton have been found; of others
only the jaws, or jaws and feet, are known. We can mention only the
more important stages.
1 and 2.1 Hyracotherium and Eohippus. Lower Eocene. The
Hyracotherium is the most primitive stage known, but only the skull has
been found, so that it has not been determined exactly what the feet were
like. The teeth display six rounded knobs or cusps on the upper molars
and four on the lower ones, and these are just beginning to show signs of
fusing into eross-crests. The premolar teeth have only one main cusp,
except the third and fourth premolars (next the molars) in each jaw, which
have two and three, respectively.
The only specimens which have been
found were in the London Clay or
Lower Eocene of England and are
preserved in the British Museum.             „. . „ ,.           T         _
r                                                                   rig. 4. Eohippus. Lower Eocene.
The Eohippus is much better Tjpper teeth> natural size, short.
known. It comes from the Lower crowned teeth, no cement, premolars
Eocene of Wyoming and New Mexico, simpler and smaller than molars
and is very like the Hyracotherium 2
except that in some species the molar teeth have the cusps more clearly
fusing into cross-crests; the last premolar is beginning to look like one of
the true molars. The fore foot of this animal has four complete toes. The
hind foot has three complete toes and the splint of another.3 A skeleton of
Eohippus was found by Dr. J. L. Wortman in 1880 in the Wind River
Badlands of Wyoming, and was described by Professor Cope in 1885. It
was until recently the only skeleton known of a four-toed horse, and is well
known to the scientific world. It was purchased by the trustees of the
American Museum in 1894 and is now on exhibition.
A seeond skeleton found by the Museum expedition of 1910, is of a larger
species, but not advanced in any other respect. It is mounted in a grazing
attitude, and probably represents the general appearance of Eohippus
more truly than the Cope skeleton. A third imperfect skeleton secured in
1911 is interesting as it shows the tiny splint bone of the inner digit of the
1  These numbers refer to the stages in the direct line of descent of the modern horse.
2 It is doubtful whether it is a distinct genus.
* See preceding page.
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16
AMERICAN MUSEUM GUIDE LEAFLETS
hind foot, indieated by facets in other specimens but not actually found
before. Crushed skulls, jaws and fragments of skeleton bones of thousands
of individuals have been found in the Lower Eocene formations.
3. Orohippus. Middle Eocene. In this animal the splint of the
fifth digit of the hind foot has disappeared, but there are still four complete
and usable toes in the fore and three in the hind foot. The crests on the
molars are a little clearer and the last premolar has become ahnost like the
molars, while the next to the last premolar is partially molariform. A skele-
ton of Orohippus, discovered by Mr. Walter Granger of the Museum expedi-
tion of 190G, in the Bridger Badlands of southwestern Wyoming, is exhibited
next to the Eohippus skeleton. It shows an animal of the size of a small
dog and proportioncd much like the breed known as the whippet.
The Orohippus was of about the same size and proportions as some of the
pigmy antelopes or duikerboks
(Cephnhphus), which live in the
<é& (»'
open forests and brush country of
East and South Africa, and have
Fig. 5. Orohippus. Middle Eocene.
Upper teeth, natura! size. Short-crowned
teeth, no cement, fonrth premolar like
molars
gained thcir name from the quick-
ness with which they can dive or
"duck" into the tall grass and
jungle on the approach of danger.
4. Epihippus. Upper Eocene.
Of this stage of the evolution of the
horse only incomplete specimens
Fig. 6. Epihippus. Upper Eocene.
Upper teeth, natura! size. Short-crowned
teeth, no cement, third and fourth pre-
molars like molars
have been found. The molar teeth
have the once round cusps almost
completely converted into crescents
and crests, while another tooth of
the premolar series has become like
the molars. The toes are still four in the fore foot and three in the hind
foot, but the central toe in each foot is becoming much larger than the side
toes.
Palceothcrium and Plagiolophus of the Upper Eocene of Europe form a
side branch of the horse line. They were very abundant in Europe, but
have not been found in the New World. One of these animals was thought
by Professor Huxley to be a direct ancestor of the horse, but it is now con-
sidered to be merely a collateral relative. Some species of Palmotherium
were of large size, equal to a tapir. They were first described in the year
1804 by the celebrated Baron Cuvier from remains found in the gypsum
quarries of Montmartre, Paris.
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THREE TOED HORSES
5, 6 and 7. Mesohippus and Miohippus. Oligocene. In this stage
there are three toes on each foot, and a splint representing the fifth digit of
the fore foot of the Eocene ancestors. The iniddle toe is now much larger
than the side toes, which bear very little of the weight of the animal. Three
of the premolars have now become entirely like the molar teeth, the crests
on the crown are completely formed, and the outside crest in the upper
molars has taken the shape of two crescents. In the Lower and Middle
Oligocene are found several species of Mesohippus mostlv of the size of a
coyote, represented by two mounted skeletons, and various skulls, jaws and
feet. In the Upper Oligocene occurs Miohippus mtermcdius as large as a
sheep, of which a fine skeleton is exhibited in the pavilion case. Several
other species of larger or smaller size are represented by skulls and jaws.
The series of skeletons in the pavilion case shows in a very striking
way the steady increase in size from the Lower Eocene to the Upper Oligo-
cene, and the reduc-
tion of the side toes
with concentration
of the weight upon
the middle toe.
. c                     .            Fig. 7. Mesohippus. Middle Oligocene. Upper teeth,
num and Hyponip- natural size. Short-erowned teeth, no cement, second,
pus. MlOCENE. An- third and fourth premolars like molars
chitherium has been
found only in Europe, and is still very incompletely known. It is much
like Mesohippus, but is larger and has the crests of the teeth somewhat
higher and more complete. Hypohippus is off the direct line of descent;
its teeth are like those of AnchUherium, by which name it has been generally
called, but the animal was much larger, equalling a Shetland pony in size.
A complete skeleton of the Hypohippus (shown in wall case) was found near
Pawnee Buttes, Colorado, in 1901 by Mr. Barnum Brown, of the Whitney
expedition.
Hypohippus first appears in the Middle Miocene, and survives along
with more advanced stages of the three-toed horses. It is a larger and more
heavily proportioned animal; the wide flat hoofs and strong side toes
enabled it to tread on soft ground, and the teeth are fitted for browsing
rather than grazing. Hence Professor Osborn considers it as adapted for a
forest life, and has named it the " three-toed forest horse." The restoration
illustrates this supposed habitat and adaptation.
8 and 9. Parahippus. Miocene. In Parahippus the tooth-crests are
somewhat higher, and the transverse ridges on the upper molars are begin-
ning to change shape so as to become a second pair of crescents inside the
17
-ocr page 18-
Fig. 8. Little three-toed horse (Mesohippus bairdi) from the Middle Oligocene of
South Dakota. American Museum. No. 1492
Four-toed Horse {Eohippus renticolus) from the Lower Eocene of Wyoming. American
Museum, No. 4832
,
-ocr page 19-
After Osborn
19
FIG. 9. SKELETON OF THREE-TOED DESERT HORSE {Hipparion whüneyi)
From the Upper Miocene of South Dakota. American Museum No. 9815
-ocr page 20-
20                 AMERICAN MUSEUM GUIDE LEAFLETS
outer pair. In the valleys between the eross-crests and on the sides and
base of the crown, a deposit of cement appears on the surface of the enamel.
In some species there is a considerable amount, but nsually it is a very thin
coat, There is no cement on the milk teeth. The feet show a decided
advance over the preceding stages, the side toes are very blender, and no
longer touch the ground. The fifth digit of the fore foot is in some species a
very short small splint, in others it is still further reduced to a little irregular
nodule of bone. This stage first appears in the Lower Miocene, and several
skulls and incomplete skeletons haverecently been obtained from formations
of this age. It survived however, although rare, as a contemporary of the
later three-toed horses.
10.     Merychippus. Middi.e Miocene. This stage marks the transi-
tion between the older
short-crowned teeth with-
out cement, and the long
crowned heavily cemented
teeth of the later stages.
Fig. 10. Parahippus. Lower Miocene. Upper
teeth, one-half natural size. Short-crowned teeth,
traces of cement. The teeth are larger than in
Mesohippus [the drawing is on a smaller scalel, the
erowns a little longer, and the inner "crests"
begin to show the change to "crescents"
The permanent molars are
intermediate in length of
crown, and quite heavily
cemented, but the milk
molars are short crowned
and have little or no ce-
ment; they are not easily
distinguishable from those
of Parahippus. The side
toes are slender and no
Fig. 11. Merychippus. Middle Miocene. Upper
teeth, one-half natural size. Moderately long-
crowned teeth, well cemented
longer reach the ground; in
some species they are al-
most reduced to splints.
Merychippus is common in
the Middle and later Miocene, and many skulls, jaws and incomplete
skeletons are contained in our collections, some of' which are placed on
exhibition. These very perfect specimens show a vestige of the fifth digit
in the fore foot still preserved as a tiny nodule of bone at the back of the
wrist.
11.     Hipparion, Protohippus and Pliohippus. Upper Miocene
and Pliocene. These three closely related genera represent the latest stage
of three-toed horses, before the side toes were reduced to splints. The teeth
are long-crowned, both milk and permanent teeth being heavily cemented,
and the side toes are extremely slender. They first appear in the Upper
i Miocene, probably directly descended from Middle Miocene species of
Merychippus, and are best represented by the beautifully preserved skeleton
-ocr page 21-
EVOLUTION OF THE HORS E IN NATURE                21
of Hipparion whitneyi from Little White River, South Dakota, found by Mr.
H. F. Wells of the Whitney expedition of 1902. This species, except for the
very largo head, had the graceful and slender proportions of the antelopes,
but in Protohippus and especially in Ptiohippus the skeleton approached
more nearly the stockier proportions of the modern horses. The Hipparion
whitneyi is regarded by Professor Osborn as fitted to live in a semi-desert
country, and in contrast to the Hypohippus, is called the " three-toed desert
horse." The restoration depicts this adaptation and environment.
In this stage the crowns of the upper molars have become much longer,
the two pairs of crescents on the upper molars are complete, with two half-
separated cusps within the inner pair. And the valleys between the crests
are completely filled with cement, so that with the wear of the teeth the
edges of hard enamel are backed inside by dentine and outside by cement.
In this way the surface of the tooth has a series of enamel ridges always pro-
jecting a little above the grinding surface, because the softer material on each
side wears down into hollows, yet never breaking off, because they are braced
so thoroughly on each side. This is a very efficiënt instrument for grinding
hard grasses. The crowns of the teeth in these Miocene horses are byno-
means as long as in the modern horses; they must therefore have worn
more slowly or worn out at an earlier age.
The feet in these genera have but one toe touching the ground. The
side toes (second and fourth digits) are complete, but much more slender
than in the earlier stages and are apparently useless, as they cannot reach
the ground. In some species they have almost disappeared. The fore feet
of these Upper Miocene horses still retain the tiny nodule of bone at the
back of the " knee" (the joint that corresponds to the wrist of a man), which
is the last remnant of the fifth digit possessed b3' their remote ancestors.
Hipparion is com-
mon in Europe and
Asia as well as in
North America, but
Protohippus and Pli-
ohippus are not
found in the Old         Fig. 12. Hipparion. Upper Miocene. Upper teeth
World.                        one-half natural size. Long-crowned teeth, heavily cemented
ONE TOED HORSES
12a. Equus. Pi.eistocene and Recent. In this stage, that of the
modern horse, the side toes have entirely disappeared and are represented
by splints on the fore and hind foot. No tracé remains on the fore foot of
the little nodule which in previous stages represented the fifth digit, while on
the inner side of the wrist the " trapezium," always present in the earlier
-ocr page 22-
22                 AMERICAN MUSEUM GUIDE LEAFLETS
stages, but progressively smaller, is now generally absent entirely. The
crowns of the teeth are much longer, and of the two half-separated inner
columns on the upper molars, one has disappeared, the other has increased
in size and changed in form. The skull has lengthened and the animal is
much larger.
It is well represented among the fossil horses by the skeleton and skulls
of Equus scotti already noticed.
Fig. 13. Equus. Pleistocene. Upper teeth, one-half natural size. Very
long-crowned teeth, heavily cemented
126. Hippidium. Pleistocene. South America. The feet are like
those of Equus, except that they are short and stout. The teeth are like
those of Pliohippus, from which it is supposed to be descended. The skull
is large and long with very long slender nasal bones. A cast of the skeleton
presented by the Museo Nacional of Buenos Ayres, Argentine Republic,
is on exhibition.
CONCLUSIONS
THESE are the principal stages in the evolution of the modern horse
from the little four-toed Eohippus. Intermediate between them
are numerous minor stages, the earlier species of each genus being
more primitive, the later species more advanced. The series of upper molar
teeth shown in Figs. 19-20 show no wide differences from one stage to the
next. But between most of them several intermediate species are known.
This gradual change is seen not merely in one or a few selected parts, but in
every bone, every tooth, every portion of the skeleton. Elsewhere in the
hall may be found similar although less complete series leading up from
animals very close to Eohippus into the modern tapir and rhinoceros.
The conclusion is unavoidable that horse, rhinoceros and tapir, three races
widely different to-day, are derived through progressive changes from a
common ancestral type. New species may have appeared suddenly, but
the race in its broader lines is the product of gradual evolution, and diverse
races may be traeed back to a more ancient common stock.1
1 Scientiflc criticisms of " Darwinism" are concerned with the way in which new
species have appeared, whether by inftnitesimal gradations or by finite "mutations,"
appreciable although usually small steps. The broader lines of evolution are not affected
by these criticisms.
-ocr page 23-
A/ter Osborn
FIG. 14. SKELETON OF EXTINCT AMERICAN HORSE (£guus scotti)
From Lower Pleistocene of Texas. American Museum, No. 10608
-ocr page 24-
24
FIG. 15. SKELETON OF SHORT-LIMBED HORSE Hippidium
From Pleistocene of Argentine Republic. From a cast in the American Museum
-ocr page 25-
Smali 4-Toed Jforses \Small 3-Toed \ Large 3-Tued \ Largc f-Toe.d
ACE or Al Ah
MAMMALS
ACE
Oltaocene\ M toe e nc YPlioctne. Plftstocaie yfecen f
E o c e n e. E p och
E.oAippu.1
Orohippus
Epihippu
Mtsohippus
Anchithertam
Hypohippu,
Parahippus
Meryc&ippus
Protonippus
Pliohippa
Hipptdiu- r.
Onokippidiut
Jlipparion.
E qua
-(iVorirt A,m t r ! ,* « ) |
(Nortfi \Am erica.)
I
-(E/trope ai<i NortA America)--^- -
-(NoTtli America,Asia and\Europe)-'^
!
-----------------(Hort/i Amchca)--------
---------------------------(Nortk America.)- \ --*-
----------------------------(ncfi America)- -I— - -!->'*«
/                     i IX
---------_--------------{NoKth America)- '- - ~r ~'
--------------------------------(SÏatA America}-------•* -
-----------—----------------(S^out/i America)------V-
-(Nortft America,Asia.,Eurvpc and Mcrth A/r/caJ- -v-
(Nart/i and Soafli America \Asia, Europt and Afnca)_\ I~^,
Fig. 16. Gcological and geographieal range of ancestors of the horse. The
position and length of the heavy black lines show the occurrence and range of each
genus in the successive geologie epochs, while the thickness of the lines indicates
relative abundance. The dotted connecting lines with arrows indicate the genealogy
MEANING OF THE CHANGE IN FEET AND TEETH
ALONG with the disappearance of the side toes in the evolution of
the horse there is a considerable increase in the proportionate
length of the limbs, and especially of the lower part of the leg and
foot. The surfaces of the joints, at first more or less of the ball-and-socket
kind which allows free motion of the limb in all direetions, beeome keeled
and grooved like a pulley-wheel, permitting free motion forward and back-
ward, but limiting the motion in all other direetions and increasing con-
siderably the strength of the joint. By this means the foot is made more
efficiënt for loeomotion over a smooth regular surface, but less so for travel-
ing over very rough ground, and it becomes of little use for striking or
grasping or the varied purposes for which the feet of polydactyl animals are
used.
The increased length in the lower leg and foot increases the length of the
stride without decreasing its quickness. The heavy muscles of the leg are
chiefly in the upper part, and to increase the length of the lower part changes
the centre of gravity of the limb very little. Consequently the leg swings
to and fro from the socket nearly as fast as before, since in an ordinary step
the action of the leg is like that of ü pendulum, and the speed of the swing
-ocr page 26-
20
AMERICAN MUSEUM GUIDE LEAFLETS
is regulated by the distance of the centre of gravity from the point of
attaohmcnt, as that of a pendulum is by the height of the bob. To increase
the length of lower leg and foot therefore gives the animal greater speed;
but it puts an inereased strain on the ankles and toe-joints, and these
must be strengthened correspondingly by converting
them from ball-and-soeket joints to "ginglymoid"
or pulley joints. Additional strength, likewise
at the expense of flexibility, is obtained by the
consolidation of the two bones of the f ore-
arm (ulna and radius) and of the leg
(tibia and fibula) into one, the shaft
of the smaller bone practically dis-
appearing, while its ends become
fused solidly to its larger
neighbor.
The increase in length
of limb renders it neces-
sary for the grazing
animal that the
head and neck
sho
in-
crease in
length
FIG. 17. EVOLUTION OF THE FORE LEG. PRINCIPAL STAGES
In the four-toed horses the radius and ulna are separate and their shafts of
about equal size. In the earlier three-toed horses the ulna is separate but its shaft
considerably reduced. In the later three-toed horses the ulna is partly Consoli-
dated with the radius and its shaft is reduced to a thin thread. In the one-toed
horses the ulna is more eompletely consohdated with the radius and its shaft h^s
entirely disappeared
-ocr page 27-
EVOLUTION OF THE HORSE IN NATURE
27
order to enable the mouth to reach the ground. An example of these
changes is the modern horse, in which we find the neck and head much
elongated when compared with the little Hyracotherium and this elongation
has taken place pari passu with the elongation of the legs. The reduction
and disappearance of the side toes and the concentration of the step on
the single central toe serve likewise to increase the speed over smooth
ground. The soft yielding surface of the polydactyl (several-toed) foot is
able to accommodate itself to a rough irregular surface, but on smooth
ground the yielding step entails a certain loss of speed. A somewhat sim-
ilar case is seen in the
pneumatic tire of a bicycle;
a "soft" tire accommo-
dates itself to a rough road
-JülffA and makes easier riding,
but a "hard" tire is faster,
especially on a smooth
road. Similarly, the hard,
firm step from the single
toe allows of more speed
over a smooth surface, al-
IAl
FIG. 18. EVOLUTION OF THE HIND LEG. PRINCIPAL STAGES
In the four-toed horses the fibula is complete and separate from the tibia. In
the earlier three-toed horse it is very slender, and fused with the tibia from about
the middle of the shaft down. In the later three-toed horses the shaft of the fibula
is incomplete and both ends are fused with the tibia. In the one-toed horses the
lower end is more thoroughly united so as to be indistinguishable from the tibia
-ocr page 28-
28
AMERICAN MUSEUM GUIDE LEAFLETS
Fig. 20. Evolution of the Teeth. Later
Stages. Second Upper Molar (Read up).
(8) Merychip-
pus, Middle
Miocene; (9)
Hipparion, Up-
per Miocene;
(10)   Equus ste-
nonis, Pliocene;
(11)  Equus com-
plicaties, Pleisto-
cene; (12) Equus
caballus,         the
modern horse
Fig. 19. Evolu-
tion of the Teeth.
Earüer Stages. Sec-
ond Upper Molar
(Read up). (1)
Eohippus, Lower
Eocene; (2) Orohip-
pus, Middle Eo-
cene; (3) Epihip-
pus, Upper Eocene;
(4)         Mesohippus
montanensis, Lower
Oligocene; (5) Meso-
hippus bairdi, Mid-
dle Oligocene; (6)
Miohippus, Upper Oligocene; (7)
Parahippus, Lower Miocene
-ocr page 29-
EVOLUTION OF THE HORSE IN NATURE                29
though it compels the anhual to piek its way slowlv and with care on
rough, irregular ground.
The change in the character of the teeth from brachydont or short-
crowned to hvpsodont or long-crowned, enables the animal to subsist on
the hard, comparatively innutritious grasses of the dry plains, which require
much more thorough mastication before they can be of any use as food
than do the softer green foods of the swamps and forests.
All these changes in the evolution of the horse are adaptations to a life
in a region of level, smooth and open grassy plains sueh as are now its
natura! habitat. At first the race was better fltted for a forest life, but it
has become more and more completely adapted to live and compete with
its enemieS or rivals under the conditions which prevail in the high dry
plains of the interior of the great continents. The great increase in size,
which has occurred in almost all races of animals whose evolution we can
tracé, is dependent on abundance of food. A large animal, as may be
shown on ordinary principles of mechanics, requires more food in propor-
tion to its size than does a small one, in order to keep up a proper amount
of activity. On the other hand a large animal is better able than a small
one to defend itself against its enemies and rivals. Consequently as long
as food is abundant, the larger animals have the advantage over their
smaller brethren, and by the laws of natural selection the race tends to
become continually larger until a limit is reached, when sufficiënt food
becomes difficult to obtain, the animal being compelled to devote nearly
all its time to getting enough to eat.
-ocr page 30-
A/ter Osborn
FIG. 21. EVOLUTION OF THE HIND FOOT OF THE HORSE
Side views of six stages, Eohippus, Mesohippus, Miohippus, Merycfiippus, Hipparion,
Equus
-ocr page 31-
CAUSE OF THE EVOLUTION
THE evolution of the horse, adapting it to live on the dry plains,
probably went hand in hand with the evolution of the plains them-
selves. At the commencement of the Age of Mammals the western
part of the North American continent was by no means as high above sea
level as it now is. Great parts of it had but recently emerged, and the Gulf
of Mexico still stretched far up the valley of the Mississippi. The climate
at that time was probably very moist, warm and tropical, as is shown by the
tropical forest trees, found fossil even as far as Greenland. Such a climate,
with the low elevation of the land, would favor the growth of dense forests
all over the country, and to such conditions of life the animals of the be-
ginning of the mammalian period must have been adapted. During the
Tertiary the continent was steadily rising above the ocean level, and at the
same time other influences were at work to make the climate continually
colder and drier. The coming on of a cold, dry climate restricted and
thinned the forests and caused the appearance and extension of open,
grassy plains. The ancient forest inhabitants were forced either to retreat
and disappear with the forests, or to adapt themselves to the new conditions
of life. The ancestors of the horse, following the latter course, changed with
the changing conditions, and the race became finally as we see it to-day, one
of the most highly specialized of animals in its adaptation to its peculiar
environment. At the end of the Age of Mammals the continents stood at a
higher elevation than at present, and there was a broad land connection
between Asia and North America, as wcll as those now existing. At this
time the horse became cosmopolitan, and inhabited the plains of all the
great continents, excepting Australia.
It is a question whether the direct ancestry of the modern horse is to be
searched for in western America or in the little known interior plains of
eastern Asia. It is also unknown why the various species which inhabited
North and South America and Europe during the early part of the Age of
Man should have become extinct, wdiile those of Asia (horse and wild ass)
and of Africa (wild ass and zebra) still survive. Man, since his appearance,
has played an important part in the extermination of the larger animals;
but there is nothing to show how far he is responsible for the disappearance
of the native American species of horse.
31
-ocr page 32-
PARALLEL EVOLUTION IN OTHER RACES
IT is interesting to observe that while the evolution of the horse was
progressing during the Tertiary period in North America another
group of hoofed animals, the Litopterna. now extinct, in South America
evolved a race adapted to the broad plains of Argentina and Patagonia and
singularlv like the horse in many ways. These animals likewise lost the
lateral toes one after another, and concentrated the step on the central toe;
they also changed the form of the joint-surfaces from ball-and-socket to
FIG. 22. THREE-TOED PSEUDO-HORSE
Fore and hind feet, one-half natural size. Diadiaphorus of the Miooene of South
America, although so closely like the three-toed horses in the feet, has a wholly
different skull and teeth, and belongs to a different order, the Litopterna, peeuliar to
South America and now extinct. From specimens in the American Museum
32
-ocr page 33-
EVOLUTION OF THE HORSE IN NATURE                33
pulley-wheel joints; they also lengthened the limbs and the neck; and they
also lengthened the teeth, and coraplicated their pattern. Unlike the
true horse, they did not form cement on the tooth, so that it was by no
means so efficiënt a grinder. This group of animals native to South America
became totally extinct, and were succeeded by the horses, immigrants from
North America, which in their turn became extinct before the appearance
of civilized man.
Many of the contemporaries of the horse in the northern hemisphere
were likewise lengthening the limbs, lightening and strengthening the feet,
elongating the tooth-crowns to adapt themselves to the changing conditions
around them, but none paralleled the horse evolution quite so closely as did
the pseudo-horses of South America. But the camels in America, the deer,
antelope, sheep and cattle in the Old World, progressed on much the same
lines of evolution, although their adaptation was not to just the same con-
ditions of life.
FIG. 23 ONÏ-TOEP PSEUDO-HORSE
F Fore and hind feet, one-half natural size. The Thoatherium has gone even further
than the modern horse in reducing the side toes to tiny rudiments instead of splints.
The skull and teeth show the animal to be closely related to Diadiaphorus (Fig. 22)
and widely different from true horses. Thoatherium was a little larger than a
fox terriër and lived in South America during the Miocene Epoch. From specimens
in the Princeton Museum and the American Museum of Natural History
-ocr page 34-
£ V O ■ L U T
-ocr page 35-
vtjOCENE;
ÉPOChT
ƒ -....., ' .... " ■■
j
/ OLIGOCENE ï
' EPOCH ;
ƒ .
EOCENE
. '. EPOCH
i
s
E
■ %-èï
HIND TOOT                   SKUU
HORS
THE
-ocr page 36-
FIG. 25. GlANT DRAFT HORSE AND DIMINUTIVE BUT FULLY ADULT SHETLAND PONY
____j
.....
-ocr page 37-
Part II. THE HORSE UNDER DOMESTICATION
ITS ORIGIN AND THE STRUCTURE AND GROWTH OF THE TEETH
By S. H. Chubb
WHEN animals are living under perfectly natural eonditions, their
physical structure is slowly modified by climate, topography
of habitats and food supply as well as by many other forces.
In the struggle for self-preservation among the competitors by which they
are surrounded, they develop weapons of defence, or acquire speed mechan-
ism or other means of escape. Thus what we may call natural, as opposed
to artificial evolution, is controlled by a great variety of forces, while in a
condition of domestication wTe have development directed in certain lines
by man's intelligence.
ORIGIN OF THE DOMESTIC HORSE
IN the light of researches made by Professors Ridgeway, Osborn and
Ewart, there seems to be little doubt that the domestic horse has been
derived from several wild types which have since become extinct as
wild species. Of two at least we may be reasonably sure: one of Europe
or northwestern Asia, which has been called the Norseman's horse; the
other from northern Africa, which Professor Ridgeway has called Equus
libycus.
There is abundant evidence to prove that in the late Quaternary, during
and after the Glacial Period, but nevertheless many thousands of years ago,
prehistorie man chased and killed wild horses, using their flesh for food and
possibly their skins for raiment. This period was foliowed by a second,
during which wild horses were captured, broken to rude harness and driven.
The rearing action of the horse skeleton in the group on exhibition in the
Museum (Frontispiece) is designed to express unwilling subjection, and the
position of the man, as if holding a bridle, intellectual control. The
period of domestication passed insensibly into a third, that of artificial
development, during which the horse was modified, and is stil! being modi-
fied in various directions.
Under man's protection and management, changes are brought about in
domestic animals with considerable control and much more rapidly than
under perfectly natural eonditions. Through training and careful selec-
tion in breeding, speed has been greatly increased in the race horse, weight
and strength have been developed in the draft horse, while the Shetland
pony has been reduced to a most diminutive size.
37
-ocr page 38-
Fig. 26. The draft horse pulling a heavy load. Gift of the late William C. Whitney.
The subject from which the skeleton was prepared was presented by Mr. George Ehret
Fig. 27. Arabian stallion 'Nimr." Mounted in the position of watching a herd. Subject
presented by Mr. Randolph Huntington
-ocr page 39-
THE HORSE VN DER DOMESTICATION
:!9
The intimate relations which have thus existed between the horse and
man have influenced both, and it is generally acknowledged by students
of mankind that the subjugation of the horse and his adoption, both as a
rneans of transportation and as an aid in agriculture, have been factors of
the greatest importance in the later development of the human race.
COMPARISON OF THE SKELETON OF HORSE AND MAN
WHILE considering these two skeletons (Frontispiece), it will be
worth while to look for a moment into their structure. They
are so placed as to facilitate comparison. The one representing
a typical or average type of horse, the other a man of about six feet in
height and proportionately heavy. The limbs of the horse, moving only
forward and backward, have much less freedom of motion than have those of
man. Note the ball-and-socket joint of man at the shoulder and hip, the
rotary motion of the forearm and the flexibility at the wrist and ankle, and
compare with the restricted movement at the shoulder of the horse, the
hingelike joint at the elbow, and the limited movement at the wrist (knee)
and ankle (hoek). The most pronounced differences however, are found in
the head and feet. Compare the skull of man, which has an enormously
developed brain and reduced facial portion, with that of the horse which
has a comparatively small brain, the face, mouth, and teeth monopolizing
almost the whole skull. The feet, instead of having five toes as in man, are
reduced to a single digitl and they are very much elongated as a striking
speed specialization. And yet a careful «tudy will reveal a most striking
similarity between the two subjects in general structure, the differences
being simply modifications of a common plan.
THE DRAFT HORSE
THE Norseman's horse of Europe seems to have been an animal with
large head, convex forehead and rough coat, of rather clumsy
appearance, and of little speed. It may have been a near relative
of the Przewalsky horse which still lives as a wild species in northwestern
Mongolia, the only true wild horse known at the present time. Among
other evidences of this prehistorie type, are the many sketches found in the
south of France and elsewhere, made by the very primitive cave-dwellers,
which seem clearly to depict this type of horse, and it is no doubt this strain
which predominates in our heavy draft horse of to-day although of course
this horse has been greatly increased in size and strength by long and careful
breeding.
1 See page 21.
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AMERICAN MUSEUM GUIDE LEAFLETS
An attempt has been made to
express the strength acquired in
this breed in the mounted skele-
ton of the draft horse (Fig. 26).
This skeleton has been so mount-
ed as to show the action of the
bones when the animal is draw-
ing a heavy load. We must
imagine that the shoulders rest
against a collar upon which the
horse is exerting its energy. Note
that the head and body are low-
ered, the hind legs are doing the
greater amount of work, the fore
legs acting as supports, though a
portion of the weight of the body
has been thrown against the col-
lar. From the rear view (Fig. 28)
note that the right hip joint is
much nearer the median line
than is the left. The joint is
also lower, and indeed, the entire
right side of the pelvis has been
lowered and thrown well to the
left, so that when at the moment
of greatest strain the right leg is
extended, the pressure upon the
anterior part of the body, and
thence upon the collar, is applied
in a line which coincides with
the main axis of the body. At
the next moment the left leg is
supposed to be exerted, the right is
released, the pelvis then swings
to the right, the curve in the
backbone becomes reversed and
the pressure is again applied (this
time from the left) along the
main axis of the body as before;
and so on from step to step.
Fig. 28. The draft horse. Rear view
phowing action of pelvis and backbone
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DEVELOPMENT OF GREAT SIZE IN THE DRAFT HORSE
THE skeleton of a very large draft horse is exhibited to show the
extreme development of size in this breed. It has been photo-
graphed with that of a Shetland pony to show two extremes in
domestie horses (Fig. 25). The following is a table of measurements of the
two specimens.
Giant Draft Horse           Shetland Pony i
Height at shoulders..........6 ft. 1 in. (181 hands) 2 ft. 9| in. (81 hands)
Weight in life...........................2370 lbs. 170 lbs.
Bulk of humerus......................118J cu. in. 91 cu. in.
Bulk of femur.........................188 cu. in. 131 cu. in.
The pose chosen for the mounting of this specimen is one of inaction,
designed to express quiet restfulness, in contrast to the running action of
the race horse, to be mentioned later. It shows also a habit peculiar to
horses, that of alternately resting the hind legs. Almost the entire weight
of the hind quarters is supported on the extended left leg, while the right
hind leg rests in a more flexed position and hangs perfectly lax. The pelvis
also seems to hang, as it were, from the left hip joint, tilting very much to
the right and slightly twisting the vertebral column.
A peculiar function of the patella (kneecap) in the horse is shown in the
left knee joint or stifle. While the limb is extended and supports the ani-
mal's weight, the patella rests on a projecting articulation of the femur, so
that the knee is locked in an extended position by a very strong ligament
which holds the patella at a fixed distance from the tibia below, thus sus-
taining the weight required of it with comparatively little muscular exertion.
An abnormal peculiarity of this specimen is a pair of supernumerary
molar teeth, which appear at the posterior end of the upper set. Having no
opposing teeth in the lower jaw upon which to wear, they have protruded
down into the gum and must have caused the animal considerable discom-
fort.
THE SHETLAND PONY
IT is highly probably that the Shetland pony is derived from practically
the same wild stock as the very much larger draft horse, but has been
reduced in size by ad verse conditions to which it was subjected in the
cold and barren Shetland Islands with their limited area, and also by
having been systematically bred for the smallest possible size.
Figure 25 shows the skeleton of ar exceptionally small pony which was
secured through the Whitney fund. This pony was bred in Scotland and
obtained through the kindness of Professor J. C. Ewart of the University
of Edinburgh. The skeleton represents the grazing action. It will be seen
that the downward reach of the head and the slow, lax step modify the posi-
tion of almost every bone in the body.
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42                  AMERICAN MUSEUM GUIDE LEAFLETS
The vertebral column is considerably arched in the dorsal region, thus
assisting in the downward curve of the neck and at the same time tilting the
angle of the pelvis a few degrees toward the perpendicular, increasing the
length of the hind limbs and tilting the body toward the head. The head
being turned well to the right, there is a very slight curve toward the left
in the anterior portion of the dorsal vertebrse, and a slight curve to the right
in the lumbar vertebrae owing to the backward position of the right hind foot.
The weight of the body falls on the right front and the left hind foot,
bringing them both very near the median line, and also modifying the posi-
tion of the scapula and elevating the left side of the pelvis. A little below
the knee a very small hairlike bone may be seen, which represents the
shaft of the almost extinct fibula, a bone which was well developed in the
ancestors of the horse.
THE ARABIAN HORSE
OF all the many types of horses probably the one most universally
admired and loved is the Arabian, with its marvelous grace and
beauty, great intelligence, perfection of anatomical mechanism,
fleetness and endurance. The question may well be asked, whence comes
this superiority?
The great fondness and care with which the Arabs have bred their horses
for many hundreds of years have undoubtedly done much for the elevation
of the stock; but more than this it is shown almost conclusively that the
Arab was blessed with a wonderfully fine natural species on which to exer-
cise his care. On this point Professor William Ridgeway of Cambridge Uni-
versity, has given us an immense mass of most convincing evidence.1
There are many reasons, traditional and historical, as well as zoölogical,
for believing that the Arabian horse, or as Professor Ridgeway has called it,
the Libyan horse, is in origin entirely separate from the very much inferior
northern or Norseman's horse, and that its native home was not in Arabia
but northern Africa, where it was domesticated by the ancient Libyans, in
all probability as early as 2000 b. c.
The Egyptians also knew f uil well the value of domestic horses. " Egypt
was, in fact, famous for its breed of horses which were not less excellent than
numerous, and we find that they were even exported to other countries,
Judea, Syria, and to the Kings of the Hittites."2 It is very clear too, from
Egyptian art, that these horses were also of the North African, or as we would
say to-day, Arabian type. It has been the constant infusion of this Libyan
blood which has tended to improve our commoner horses for these many
centuries.
1 Ridgeway, William. Origin and Influence of the Thoroughbred Horse. Cambridge:
Univ. Press, 1905.
» Wilkinson, I. G. Ancient Egyptians.
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THE HORSE UNDER DOMESTICATION                    43
The skeleton of "Nimr" (See Fig. 27, p. 38), a pure-blooded Arabian
stallion, has been mounted to show some of the conspicuous characteristics
of this species, which are as follows:
1.    Head and tail carried high when the animal is animated;
2.    Skull short, but broad between the eye sockets;
3.    Eye sockets high and prominent, giving the eyes a wide range of vision;
4.    Facial profile, or forehead, concave:
5.    Muzzle slender, but jaw deep and wide-set above the throat;
6.    Round thorax, well ''ribbed up" and short back with only five ribless, or
lumbar vertebrae;
7.    Horizontally placed pelvis (a speed character) and very high tail region, few
tail vertebrae;
8.    A complete shaft of the ulna, or small bone of the f orearm;
9.    Long and slender cannon bones and long sloping pasterns.1
"Nimr" was sired by the desert-bred Arabian "Kismet," famous for an
unbroken series of victories as a race horse in India. After his death at
Oyster Bay, Long Island, in 1904, the subject was presented to the Museum
by the owner, Mr. Randolph Huntington.
THE RACE HORSE
AS for the earliest domestication of the horse in Britain, where the
race horse or thoroughbred has since been developed, no definite
statement can be made. We read that horsemen in large num-
bers opposed the landing of the Romans, and also that in 631 A. d. the
English first began to saddle their horses. Again we find mention of
"running" horses in the ninth century. But it is not until about 1689,
when the famous "Byerley Turk" was brought to England, that we learn
anything definite concerning the origin of the present English stock, though
horses of undoubted North African blood had been imported from Turkey
a century or more earlier.
The Darley Arabian, bred in the desert of Palmyra, was imported into
England by Mr. Darley in 1705. About twenty years later the Godolphin
Arabian,2 arrived on the scène, continuing to improve the English stock
with infusion of North African or Libyan blood (page 42) to which the
quality of the race horse is chiefly due.
Touchstone states, " The thoroughbred, as soon as he ceases to be sub-
jected to the special régime of training reverts to the Arab type with
such extraordinary rapidity that we cannot be blind to the fact that he
descends, for at least seven parts out of eight, from the pure Arab,3 which
' Osbohn, H. F. Points of the Skeleton of the Arab Horse. Buil. Amer. Mus. Nat.
Hist., vol. xxiii, art. 13, pp. 259-263, 1907.
1 Richard Berenger, however, denies that this horse was an Arab, though his view is not
generally accepted. History and Art of Horsemanship, 1771.
• Touchstone, S. F. Race Horses and Thoroughbred Stallions.
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44                  AMERICAN MUSEUM GUIDE LEAFLETS
we would consider of Libyan origin, and indeed many admirers of the
Arab would gladly eliminate the remaining eighth of non-Arabian blood.
However the race horse of to-day is a very highly specialized animal,
certainly vastly different in appearance from the Arab and yet still more
widely separated from the draft-horse type.
In July, 1906, we were particularly fortunate in the gift from the late
Mr. James R. Keene, of the remains of one of America's most famous race
horses, together with sufficiënt funds for the preparation of the skeleton.
This remarkable horse, "Sysonby" was foaled February 7, 1902, at Mr.
Keene's Castleton stud in Kentucky, a few months after the importation
from England of his dam "Optime," his sire being the English bred "Mei-
ton." His record is one of the most brilliant in the history of American
horse-racing. He won a remarkable series of victories between his first
race at Brighton Beach, July 14, 1904, as a two-year-old, and his untimely
death at four years (July 17, 1906).
The skeleton (Fig. 29) has been mounted to show a phase in the stride
of the running horse, and is based on studies made from direct observation
and instantaneous photographs. The position is that of the moment after
the right fore foot has left the ground, and the right " knee" or carpus, is
beginning to bend; the succeeding footfalls in order are the left hind, the
right hind, the left fore and the right fore, the full length of one complete
stride being about twenty-six feet.
At this instant the hind quarters are lifted perceptibly higher than the
shoulders and from a rear view it will be seen that while the hind feet are
thrust forward at this greater height from the ground, they are widely
separated so as to avoid striking the fore legs. A moment later the shoulders
will be lifted by the push of the fore feet higher than the hind quarters, then
the hind feet will move toward the median line and strike the ground, and
the fore feet will have moved forward out of the way of the hind.
The backbone is slightly arched to help draw together the fore and hind
limbs and feet, and thus lengthen the stride and bring the back muscles
into play. When viewed from above, the backbone is also observed to be
curved a little to the right, owing to the forward position of the left side of
the pelvis and of the left hind limb; this also lengthens and gives power
to the stride as the backbone is straightened.
THE TEETH OF THE HORSE
[COLLECTION IN WALL CASe]
THE dental apparatus of the horse is one of the most interesting and
highly specialized organs we find in nature. During the course of
evolution through many ages, the teeth have gradually grown more
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FIG. 29. THE FAMOUS AMERICAN RACE HORSE "SYSONBY." SHOWING ACTION IN THE HARD RUN
45
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40
AMERICAN MUSEUM GUIDE LEAFLETS
and more complex, becoming constantly more perfectly adapted to the
cropping and grinding of coarse hard grasses. They are in fact of such
great size and importance that the whole skull seems constructed chiefly for
their lodgment and operation, the custody of the brain, eyes and ears being,
as it were, of secondary consideration; hence the skull must of necessity be
very bulky, and in order that the weight may not be unnecessarily great,
large air spaces (sinuses) are provided, aggregating between two and three
times the amount of space occupied by the braki (specimens 51 and 5, on
exhibition in wall case). Indeed the skull of the horse is a beautiful design
in arches and braces, resulting in a structure of the greatest possible strength
and utility with a minimum of weight and material.
The ethmoids, the bony framework of the organ of smell, are also highly
developed, with a complicated system of scrolls presenting an immense
amount of surface to the air that is drawn into the nostrils (specimens 5,
10 and 51).
STRUCTURE OF THE TEETH
AVERY simple form of tooth is that commonly found among the
reptiles, a mere peglike structure composed of dentine with a very
much harder covering of enamel on the crown, and a nerve canal in
the center. We have selected three incisor teeth (Fig. 30) to show examples
of different degrees of specialization. A, the tooth of a young cow, is of
comparatively simple form, being somewhat flattened and having a clearly
defined line or neck between the crown which is completely covèred with
enamel and the dentine root which is without enamel. The neck, or base of
the crown, as in most simple teeth, coincides with the line of the gum. In
the horse the composition of the teeth is the same except that we have a
third element known as cement, which begins to be deposited on the surface
some time before the eruption of the young tooth, covering the enamel
almost completely. In design it is more complicated. Instead of the plain
upper border (Fig. 30^4) there is a very deep indentation or folding in of the
enamel, somewhat like the inverted finger of a glove, forming an enamel lined
cup or cul-de-sac, running far down into the tooth (Figs. 30C and D), becom-
ing more or less completely filled, particularly toward the bottom, with a
deposit of cement. It is usually observed that highly specialized organs
are more primitive in the young individual than in the adult. This is very
noticeable in one specimen (Fig. 30B), which represents the deciduous or
milk incisor of a colt about four days old. This tooth has just cut through
the gum, and does not as yet show any wear from use. The enamel cup is
very shallow as compared with that of the permanent tooth (C and D). It
also shows a clearly defined line at the base of the crown, which when the
tooth is fully grown, will coincide with the line of the gum as in the teeth
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Fig. 30. Incisor teeth showing different degrees of specialization. Natural size.
A.     Permanent tooth of young cow. a, crown; 6, base of crown; c, root
B.     Deciduous tooth of colt 4 days old. o, crown; b, base of crown; c, incomplete root;
d, bottom of shallow cul-de-sac; e, enamel; ƒ, cement deposited on enamel
C.     Permanent tooth of colt 2 years old. a, crown; d, bottom of very deep cul-de-sac: e,
enamel; ƒ, cement
D.     Side view of C. (A, B, and C inner views)
Fig. 31. Incisor teeth of the permaneat set (i. -) showing wear and movement.
Inner view. Natural size.
A.     Tooth of a colt 2 years old before it nas erupted. e, folded edge of enamel, unworn
B.     Tooth of horse 4 years old. a, crown; 6, base of crown; c, incompleted root; d, bottom
of cul-de-sac; e, worn edges of enamel; g, gum line
C.     Tooth of horse 12 years old. c, root fully grown- ƒ, internal and external cement;
h, nerve foramen; i, natural cavity in cement
D.     Tooth of horse 17 years old. j, "dental star"
E.     Tooth of horse 33 years old
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AMERICAN MUSEUM GUIDE LEAFLETS
of the cow and other simple teeth. The root of B is not as yet fully grown,
but presents a large pulp cavity which will be reduced to a narrow nerve
canal as the root grows longer, and tapers to a point, leaving only a very
small foramen for the passage of the nerve. Figure 30C shows the perma-
nent incisor of a colt two years old, which erupts and replaces its deciduous
predecessor at about three and a half years. The cul-de             mentioned
above, is very deep, running down almost the full length of the crown, the
root not yet ha ving begun to develop. There is already considerable cement
in the cul-de-sac, and a very slight deposit beginning on the external surface
about the upper end of the crown. A series of lower incisor sections and
also vertical sections of incisor teeth, exhibited in the wall case, will explain
the structure more clearly.
WEAR AND COMPENSATING MOVEMENT OF THE INCISORS
WHAT is frequently spoken of as " growth" in the horse's teeth is
not growth, but rather movement. It is true that growth does
continue in some few of the teeth until the horse is ten or
twelve years old, but only in the completion and closing of the roots
(see above), the crowns being all fully developed, including grinders as well
as incisors, at about five and one-half years. From the time the tooth begins
its service it continues to move out of the alveolar cavity, which fills with
new bone, this movement counteracting the rather rapid wear of the cutting
or grinding surface, so that in extreme old age some of the teeth may be
worn down to the very points of the roots. One of their most remarkable
specializations is the extremely long crown which instead of being entirely
above the gum line, as with the more simple teeth, human for instance,
extends far down into the alveolar cavity, as much as 3f inches in the
large premolars, as a reservoir of grinding material. Figure 31 shows a
series of upper incisors to explain the manner in which the tooth is worn as
it proceeds from the alveolar cavity, the wearing surface altering in con-
tour as it progresses along the crown of the tooth which constantly changes
in shape toward the root.
A is the permanent tooth of a colt two years old, before it has replaced
its deciduous predecessor or has received any wear, so that the external
enamel is continuous with that of the cul-de-sac or internal enamel. 'The
cement now lines the cul-de-sac and is beginning to be deposited on the
external enamel. As yet the tooth has no root, but presents a wide-open
pulp cavity at the base.
B is the tooth of a horse about four years old. It has recently replaced
its deciduous predecessor, being in use only about six months. The folded
edge of enamel is worn through, exposing the dentine beneath, and sepa-
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THE HORSE UNDER DOMESTICATION
V.)
rating the enamel of the cul-de-sac from that of the exterior, with the
exception of a very slight connection at the left-hand border. Internal as
well as external enamel is covered with cement except on the wearing sur-
face. The base of the crown is not clearly defined but can readily be
located as it coincides with the lower border of enamel. It will be seen
that this point, instead of being at the surface of the gum as in more primi-
tive teeth, is planted about an inch and three-eighths deep, g indicating
the gum line.
C, the tooth of a horse about twelve years old, shows a more triangular
wearing surface, having been worn down a distance of perhaps three-eighths
or one-half inch. The cul-de-sac is greatly reduced in surface diameter,
as well as in depth. The root is fully developed and shows the nerve foramen
(h) at the point. With the advance of age the wearing surface of the
tooth, molar as well as incisor, must necessarily approach the nerve, which
would subject it to exposure. This is provided for by the recession of the
nerve and a new growth of dentine, reducing the nerve or pulp cavity and
sometimes in extreme old age completely filling it.1 As the tooth wears down
this new dentine can be detected in the incisor by a slightly lighter shade in
color, and is known among horsemen as the "dental star." It is indicated
in Figure 31Z) and E.
In Figure 31Z>, showing the tooth of a horse about seventeen years old,
the wearing surface is still more triangular. The cul-de-sac is almost worn
away; the base of the crown is approaching the gum line. Not only the
crown as in the younger teeth, but the root as well, is becoming thickly cov-
ered with cement, so that the base line of the crown is obliterated, but can
readily be located b\ sectioning. On the more exposed ridges however,
particularly the anterior surface, not shown in the sketch, the cement has
been worn through in places by friction of the tongue and lips.
E shows the condition in extreme old age, this specimen being the tooth
of a horse thirty-three years old. The cul-de-sac has long since disappeared
and the only enamel remaining is a very narrow strip on the anterior
border. The wearing surface has become elliptical, and the "dental star"
has changed from a trans verse line to a rounded spot. The deposit of
cement has increased to almost an eighth of an inch in thickness, reënforc-
ing the old declining root, as it were, to prolong its service to the very last.
The base of the crown has passed beyond the gum line, and at best the
tooth could not last many years longer.
It is by the examination of these ihdications that horsemen ascertain
the age, although it. is impossible to judge accurately in the more ad vaneed
stages. Especial attention is given to the size and shape, presence or
absence of the cul-de-sac, known among horsemen as the "mark." It
1 See specimen No. 132 under "Teeth sectioned to show reduction of pulp cavity" on
exhibition in wall case.
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50                  AMERICAN MUSEUM GUIDE LEAFLETS
should be explained however, that the lower incisors which are more easily
examined in the living horse, being somewhat smaller and ha ving a shallower
cul-de-sac than the uppers just described, will acquire a certain appearance s
of wear at an earlier age. For instance, if C and D were lower teeth they
would have a similar appearance at the ages of eight and twelve years.
Considering the incisor set as a whole, it shows other marked changes with
the advance of age. To render effective service the teeth must be in close
contact; therefore, as each tooth is reduced in diameter it moves slightly
toward the median line, reducing the total transverse measurement of the
set. The meeting angle of upper and lower teeth becomes much more acute
in old age. An exhibit labeled "Series of Horse Muzzles" in the wall case
shows the general appearance of the incisor teeth at various ages.
The canine tooth, which is rarely found in the female except in a very
abortive form, is of comparatively simple structure and has no apparent
function at the present time, but may have been of service as a weapon at a
very early stage of evolution. It receives almost no wear, has little or none
of the compensating movement of the incisors and is, in fact, of no very
great interest.
DESIGNATION OF THE TEETH
THE deciduous or milk teeth, which are shed and replaced by perma-
nent ones, are divided into three classes: in front, the deciduous
incisors, back of these, the very small deciduous canines, and still
farther back, the deciduous molars.
In the permanent set the incisors and canines have replaced the de-
eidtwus ones, and the deciduous molars have been replaced by the premolars.
Still back of the premolars comes a fourth class, the permanent or true
molars, which have no deciduous predecessors.
In works on comparative anatomy and zoölogy the teeth are expressed
by initial letters and numbers in fractional form; the numerator denotes
the number of upper teeth, and the denominator the number of lower teeth
of each class, running back from the median line in front, and considering
only one side of the skull. For instance the typical mammalian milk
dentition is as follows, all being deciduous teeth: incisors three, canine
one, molars four, which would be expressed d.i. §, d.c. \ d.m. f. The per-
manent dentition would be *. §, c. j, p.m. |, and m. § — forty-four teeth in
all. The human subject having only thirty-two permanent teeth, would
be expressed ?'. f, c. \, p.m. f, and m. §,
The teeth are numbered from the median line, hence when indicating a
certain tooth i. 3 would be read, lower incisor three; p.m. * upper pre-
molar four; lower deciduous canine is expressed d.c. —. Figure 32 shows
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Fig. 32. Designation of teeth
A.    Lower jaw of colt 9 months and 12 days old, marked to show designation of deciduous
teeth
B.    Lower jaw of horse 5 years old marked to show designation of permanent teeth
the designation of deciduous and permanent teeth. A is the lower jaw of
a colt nine months and twelve days old, in which the deciduous dentition
is all in use, and though the eruption of the molars has not yet begun, the
development of one at least is well under way. In B, a horse about five
years old, the permanent teeth are all in place. It must be borne in mind
that when a subject has a reduced dentition the teeth are numbered not
necessarily as they appear in the jaw, but according to what is believed
to be their true relation in the typical dentition, having forty-four teeth.
For instance, in the human subject where there are but two premolars
known among dentists as bicuspids, the first one in the lower jaw would be
expressed p.m. 3. The second would be p.m.\, assuming that p.m. y and
p.m. 2 are the missing teeth. The teeth of specimens on exhibition, Nos.
10 and 36, are labeled in the manner described.
THE WOLF TOOTH OF THE HORSE
IN the horse we may say that p.m. j (Fig. 37B) is now in the last stage
of elimination. Just in front of the upper premolars there is fre-
quently found a very small abortive tooth commonly known as the
si
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52                  AMERICAN MUSEUM GUIDE LEAFLETS
"wolf tooth." It does also occur in the lower jaw but is very rare. It is
absolutely non-functional, and is in f act rather detrimental, as it sometimes
gives rise to more or less irritation. So that in the horse the first functional
premolar is p.m. f. The wolf tooth, though interesting, is rather hard
to study owing to its irregularity. When speaking of the permanent teeth
it is generally designated as p.m. -, which would be correct if it really be-
longed to the permanent set; this however, I am inclined to doubt, although
it is frequently found long after the shedding period is over. Nevertheless,
it seems highly probable that it is a deciduous tooth, which ha ving no suc-
cessor, is not shed. In this case it would seem that the permanent tooth
had been eliminated earlier in the course of evolution than the deciduous
one. But until we have more conclusive evidence on this point probably
it will be as well to include the wolf tooth among the teeth with which we
find it. In figure 32^4 there is shown the unusual occurrence of the wolf
tooth in the lower jaw. In looking over the fossil ancestors it seems this
tooth began to show signs of elimination in the late Oligocene Period,
which is estimated to be about two million years ago. At this rate we may
reasonably hope for some few social reform» before the horse is entirely rid
of this rather undesirable appendix.
PREMOLARS AND MOLARS OF THE HORSE
WHEN we compare the molar tooth with its most intricate struc-
ture, with the incisor, the latter seems perfect simplicity.
Without here discussing the evolutionary history of the tooth,
it is extremely interesting to consider these special adaptations, which are
merely gradual modifications of a simple form brought about without any
radical or sudden changes, but slowly developed in an orderly and shall
we say, orthodox manner.
The molar of the horse as we find it to-day, is a wonderful structure,
presenting on its grinding surface a most complicated system of sharp
enamel edges almost as hard as glass, supported on one side by dentine
and on the other by cement. These materials being somewhat softer than
enamel, wear down slightly in advance, leaving the enamel edges sufficiently
exposed to give a perfect self-sharpening, grinding surface, but at the same
time not projecting so far beyond the general plane as to be in danger of
chipping off.
When we compare such a tooth as this with a perfectly simple one,
composed of dentine and having a short, either cone-shaped or flattened
crown, covered merely with a smooth shell of enamel without cement, it is
difficult at first sight to see any relation or similarity between them, or to
realize that the highly specialized organ is simply a development of the
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53
THE HORSE UNDER DOMESTWATIOX
primitive one. But let us by way of illustration imagine for a moment a
tooth with a crown in form somewhat like a pillar or post, composed of
dentine with two deep depressions in the top, the dentine being every-
where covered with enamel, and a thick deposit of cement on the surface
of the enamel.
When the cement and enamel are worn through on the grinding surface
we would have the exposed edge of an enamel cylinder filled with dentine,
reënfbrced with cement on the outer surface, and
two enamel rings, or rather pockets with the                      i
edges exposed, lined, or completely filled as the
case might be, with cement imbedded in the
dentine. This would be a construction similar
to that we have already seen in the incisor, ex-
cept that we have two instead of the single eul-
de-sac. Now let us imagine the enamel walls of
these culs-de-sac, and also the enamel cylinder,
deeply crenated or folded and doubled, in some
places the latter coming almost in contact with
the former, thus increasing greatly the exposed
enamel edges, and we will have the design of the
grinding surface of an upper deciduous molar
aft er it is somewhat worn (Fig. 33/1). And
here it must be borne in mind that the horse's
teeth are not fully functional until the folded
edges of enamel on the grinding surface are
worn through to the dentine.
Figure 335 shows the deciduous upper molar
(d.m. -) of a colt about three months before
birth. The enamel of the culs-de-sac is con-
tinuous with that of the exterior, the folded
:..i
'"'}
edges on the grinding surface being unworn. It
is as yet entirely without cement so that we
de-n-tme-
ce-me-n t
natwral cavity
have an unobstructed view of the enamel.
When the colt is six months old, however, the
culs-de-sac will be practically filled with cement
and also the deep folds of the exterior (Fig.
33/1), the deposit of cement beginning about a
month before birth.
We have seen that the permanent incisors
are much more highly specialized than are the
deciduous ones (Page 46). This is quite as
noticeable in the grinding teeth. Observe the
wonderful development of enamel edges in
Fig. 33. Wearing surface
of upper grinding teeth.
Natural size
A.     Worn surface of decidu-
ous molar (d. m. *} of colt
about 6 months old. e, ex-
posed enamel edges; i, nat-
ural cavity in cement
B.     Unworn surface of decid-
uous molar (d. m. *) of colt
about 3 months before birth,
showing only enamel. d, cul-
de-sac to be filled later with
cement; e, apex of folded
edge of enamel
C.     Premolar (p. m.?) of norse
8 or 9 years old
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54
AMERICAN MUSEUM GUIDE LEAFLETS
figure 33C. This is a premolar of a horse eight
or nine years old. A careful measurement of the
exposed enamel in this tooth reveals the interest-
ing fact that if these edges were straightened out
in a continuous line, it would be fourteen inches
in length. In a tooth of this size on the simple
"cylinder" plan, it is obvious we would have
only about four inches of enamel, hence we can
willingly concede nature's wisdom in this com-
paratively "modern improvement."
This enamel pattern however, presents a more
simple aspect as the tooth wears down toward the
base of the crown, so that in old age when the
grinding surface is near the root, there is less
enamel, and the self-sharpening surface is much
less perfect. The antero-posterior diameter of
the crown is also reduced toward its base.
Figure 34 shows an upper right grinder (p.m. -)
of a horse ten or eleven years old. The tooth is
cut in five sections, and reveals on each cut sur-
face, the pattern of enamel which will be presented
on the naturally worn grinding surface at various
ages.
Section A is a diagram of the natural grinding
surface as it appeared in life, and shows a very
complicated pattern of enamel, and large culs-de-
sac almost completely filled with cement.
Section C which is cut one and one-fourth
inches farther along the crown, shows great sim-
plification of enamel pattern, and the culs-de-sac
are much smaller. The five branches of the pulp
cavity (h) are open, but would have been filled
with new dentine before the natural grinding sur-
face reached this point (Page 49) which takes
place when the horse is approximately twenty-
five years old.
Section E. The lower border of enamel which
marks the base of the crown where this section
D
enamel
dentine
cement
ttaiurfal cavity
Fig. 34. Upper grinder (p. m. -) of horse 10 or 11
years old cut in 5 sections; showing pattern of enamel
at various ages
Branches of the pulp cavity
Pulp cavity
C,
E,
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THE HORSE UNDER DOMESTICATIOX
55
is cut, is somewhat irregular, so that the enamel line is incomplete. This
explains the three spaces which can be seen in the external enamel. The
culs-de-sac are entirely eliminated and the enamel edges are redueed to a
minimum. The antero-posterior diameter is also greatly redueed. The
branches of the pulp cavity are united at this point (h), where the roots
begin to diverge. This tooth, p.m. -, being the yóungest tooth in the
grinding set, would not be worn down to the base of the crown until the
horse reached thirty-five or more years, an age very rarely attained. Sec-
tions of grinding teeth on exhibition, particularly specimen No. 95, will be
of interest as illustrating structure and wear.
The lower molars in their construction are quite similar to the uppers,
one of the most striking differences being the absence of the culs-de-sac.
Much the same result is acquired however, by the very deep folding in of
the external enamel, which at various points almost meets toward the center
(Fig. 35). The lower molars are also narrower in their transverse measure-
ment.
There are several points which sometimes lead to a little confusion in
observing the grinding surface of the molars.
For example, at the bottom of the deeper con-
cave surfaces of dentine between the enamel lines,
there is a dark brown mark which is sometimes
mistaken for a fourth material, bu't is merely a
coloration of the dentine.
In the upper molars we generally find two
small cavities (Fig. 33^1 and C), one in each cul- moiar (p_ TO, 3) 0f horse 8
de-sac, which sometimes gives rise to question- 0r 9 years old
ings, and indeed there have been swindlers mas-
querading as veterinary dentists, who would gladly "fill" your horse's teeth
for a reasonable consideration. These cavities however are perfectly nor-
mal, and we have precisely the condition here as in the incisors except that
in the molar the cement is very much thicker, and the presenee or absence
of the cavity depends simply upon the thickness of the cement.
It will be seen that where the tooth comes in close contact with its next
neighbor, the cement is missing, and indeed, sometimes the conthraous line
of external enamel is broken (Fig. 35). This is due to a slight wear on the
side of the tooth. There is a strong tendency to crowd toward each other,
thus preventing the forcing of food material between them. The slight
vibration when in use, of each tooth ;n its alveolar socket, affords sufficiënt
wear to keep them perfectly fitted together, and also explains the apparent
break in the external enamel wall, which we frequently see. This crowding
together, as well as many other features, can best be observed from the side
view. On exhibition are a number of skulls having the bone cut away in
order to exposé to view the full length of the tooth.
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56                  AMERICAN MUSEUM GUIDE LEAFLETS
The three posterior teeth or molars, incline very considerably to the
front, while the other three, the premolars, lean slightly toward them (Fig.
37), so that when pressure is applied on their grinding surfaces they are
forced together like stones in the arch of a building. And as the teeth wear
down to a point of smaller diameter, the last molar in extreme old age
assumes an almost horizontal position (Fig. 37C).
The grinders from a lateral view present a most formidable looking
dental battery. It gives some idea of their development when we find that
a full set of premolars and molars, taken from a fair-sized horse of four or
five years, will weigh about four pounds, the premolars being a little larger
than the molars, a fact which is quite unusual, as in the great majority of
mammals the premolars are very much inferior in size and development, as
was also the case in the ancestral horse.1
We see from the lateral view as well as from the grinding surface, the
more highly specialized characters of the permanent tooth. Compare the
very long crowns of figure 37^4 with the deciduous molar (Fig. 36), with
its short crown, clearly defined base line and flaring roots.
Wear and movement of premolars and molars can be studied very
readily from the skulls on exhibition, three of which are shown in figure 37.
For the present we will consider only the lower teeth, which will apply
in a general way to the upper as well. The growth of the tooth begins at
the grinding surface, inside the alveolar cavity, and proeeeds toward the
root, the tooth constantly moving upward, erupting and beginning to wear
off before even the crown is complete.
Figure 37/1 shows the skull of a horse about five years old. The decidu-
ous set has been shed and the permanent teeth are all in use, though the
wolf tooth (p.m. j) is not present in this specimen.
The crown of p.m. 3, the last tooth in the
grinding set to reach the wearing line, is now
fully grown, having already lost about half an
inch from wear. It now measures three and
a half inches, makirig a total length of four
inches to be slowly moved upward and worn
away. The roots are just beginning to develop
at the base of the crown. The next tooth back
of this, m. j, is the first permanent tooth to
appear, hence the oldest one in the mouth.
The crown is worn down much shorter than
Fig. 36. Deciduous molar
that of p.m. 5, and the roots are quite evident,
(d. m. 3) of colt 11 months though still incomplete,
In figure 37B, showing a specimen about
old. Natural size. a, crown;
b, base of crown; c, root
1 See page 15.
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Fig. 37. Dental battery of adult horse
A.    SkuU 5 years old. Permanent teeth all in use
B.    SkuU 8 years old. Crowns reduced in length by wear and roots grown longer. Vestigial
p. m.i present in this individual
C.    SkuU 39 years old. Crowns almost worn away. Lower molars incline forward (The
canines are absent in the female)
57
-ocr page 58-
58                  AMERICAN MUSEUM GUIDE LEAFLETS
eight years old, the crowns have all been perceptibly reduced by wear, and
the roots are all more or less developed, those of m. y being almost com-
pletely grown.
The oldest skull' in our exhibit is a specimen from a horse thirty-
nine years old, figure 37C. The crowns are almost entirely worn away.
Some of the roots are very much elongated, while others are thickened by
an extreme reënforcement of cement. The molars are very much inclined
forward, particularly m. 3, which is so worn as to almost separate the two
roots. In the upper set, p.m. ~ is represented only by irregularly shaped
lumps of cement which surround the last fragments of roots, prolonging to
the utmost their very much impaired service.2
ERUPTION OF THE TEETH OF THE HORSE
THE calcification of all the deciduous teeth and also m. \ begins before
birth. When the colt is born, d.i. j and d.m. f and 3 are very near
the surface of the gum, and generally erupt within two or three
days; d.m. | is apt to follow during the first mönth; d.i. §, the last deciduous
tooth to erupt, makes its appearance as late as the eighth or tenth month.
The three deciduous molars seem very large for the size of the young skull,
their antero-posterior measurement being a little greater than that of their
successors, the premolars, and occupy the entire space in the skull which
will finally accommodate the whole grinding set, so that ra. % is crowded f ar
back, beginning its development in the alveolar cavity directly below the
eye socket, as shown in figure 38/4, a colt two days old. This discrepancy,
however, is nicely adjusted. As fast as the increasing size of the skull will
permit, the teeth are crowded forward with a horizontal movement, making
room at the back for the development of the molars, each one resigning its
birth-place below the eye, and moving forward to make room for the next
one to fall in line, the operation being about the same in the lower set as in
the upper teeth.
The incisors also encroach upon the region of the very small d.c. -5-,
particularly d.i. 3, which begins its development well back of the d.c. —
(Fig. 38^4). As the jaw grows, d.i. 3- passes forward and assumes its final
position in front of the d.c. —.
At eleven months (Fig. 38.B) the deciduous teeth are all in use and most
of them considerably worn. ra. -, which is due to erupt within about a
month, has increased wonderfully in length and has moved forward, giving
up the place under the eye to m. -, which has already attained considerable
size, and has advanced somewhat in its forward movement. Between the
1  Since writing, a skull 42j years old has been obtained, Specimen No. 138, on exhi-
bition.
2 Specimen No. 132 in wall case shows interesting examples of reënforcement by cement
in extreme old age.
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d.™.*
Fig. 38. Dentition of the colt
A. Colt 2 days old showing deciduous teeth and beginning of m. \.
a. XAeven months old. Deciduous teeth somewhat worn and permanent set developing
v>- 1 wo years old. Deciduous teeth very mucb worn and permanent set partly in use
59
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60                  AMERICAN MUSEUM GUIDE LEAFLETS
roots of d.m. -, which are flattened and widely spread apart, thus making
room for the new tooth, the calcification of p.m. 2 is just beginning. i. \
is developing, and can be seen in specimen No. 38 l f ar back in the alveo-
lar cavity under the root of d.i. \, but is not visible in the figure.
In figure 38C, a colt of two years, calcification has begun in all the
permanent teeth except i. -. The crowns of the deciduous molars are
nearly worn away, while the roots are being absorbed by the growth of
the premolars which have now attained a considerable size. m. -, the first
permanent tooth to erupt, has been in wearing about a year and is just
beginning to develop roots. m. 2- has cut through the gum and is very
slightly worn. The alveolar cavity below the eye, is now lodging its last
young tenant, m. -, which by the time it is full grown will have moved
nearly two inches anterior to its present position.
SHEDDING THE TEETH
BEFORE the deciduous molars are shed the crowns are almost en-
tirely worn away on the one side, while the roots are absorbed by
the new teeth on the other, so that there is only a small fragment
of tooth really lost. The time of shedding may vary a number of months:
At three years approximately, d.m. f and f are shed, exposing the grinding
surface of p.m. § and §. m. I and § are in use and somewhat worn. At
about three and one-half years d.i. j will be shed. At four years the shed-
ding of d.m. | follows very closely after, or sometimes during the eruption of
ni. I. A little later d.i. § is shed. At about fivê or a little before, the canines
will erupt and d.i. § are shed, and the permanent dentition is all in use.
There are a number of specimens on exhibition in the wall case, not figured
in this description, which it would be well to consult in connection with the
shedding of teeth.
1 On exhibition in wall case.
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PRINCIPAL LITERATURE ON THE EVOLUTION OF THE HORSE
1826. Mitchill, S. L. Catal. Org. Rem., New York. pp. 7, 8. (First
record of fossil horses in America)
1841. Owen, Richard. On Hyracotherium leporinum. Trans. Geol. Soc.
(2), vol. vi, pp. 203-208. (Earliest record of the four-toed horse,
not then recognized as ancestral to the horse family)
1860. Hensel, R. Ueber Hipparion mediterraneum. Abhandlung. Akad.
Wiss., Berlin. (Description of the three-toed horse of southern
Europe, Pliocene epoch)
1863. Rütimeyer, L. Beitrage zur Kenntniss der fossilen Pferde. Ver-
hand, der naturforsch. Gesellsch. Basel, vol. iii, pp. 558-696.
(Extinct horses of Europe, chiefly Quaternary)
1869 Leidy, Joseph. Extinct Mammalian Fauna of Dakota and Ne-
braska. Journ. Acad. Nat. Sci. Phila., vol. vii. (Numerous
American species of three-toed horses described in this volume)
1873.     Kowalevskt, W. Sur VAnchithcrium aurdianense et sur l'Histoire
Paléontologique des Chevaux. Mem. Acad. Imp. Sci. St. Peters-
bourg, (7), vol. xx, pp. 1-73. (First attempt at reconstructing
the ancestry of the horse from fossil specimens)
1874.     Marsh, O. C. Notice of New Equine Mammals from the Tertiary
Formations. Am. Journ. of Sci. (3), vol. vii, pp. 247-258. (First
reconstruction of the ancestry of the horse from American fossils)
1875.     Burmetster, H. Los Caballos Fósiles de la Pampa Argentina.
Published for the Provincial Government of Buenos Aires Exhibit
at the Centennial Exhibition, Philadelphia, 1876. (Description
and illustration of Hippidium and other extinct horses of South
America)
1879. Marsh, O. C. Polydactyle Horses, Recent and Extinct. Am.
Journ. Sci. (3), vol. xvii, pp. 499-505. (American ancestry of the
horse, with diagrams showing the evolutionary stages)
1885. Cope, E. D. "Hyracotherium" (Eohippus), in "Tertiary Verte-
brata," Report U. S. Geol. Sur. Terrs., vol. iii, book 1, pp. 624-652,
pil. xlixa, xlixft, xlixc. (Description and figures of the skeleton
of the four-toed horse)
1887-90. Pavlow, Marie. Etudes sur l'Histoire Paléontolog'que des
Ongulés. Buil. Soc. Imp. Nater., Moscow
1891. Scott, W. B. Osteology of Mcsohippus. Journ. Morphology,
vol. v, pp. 3-73. (Description and figures of the skeleton of the
three-toed horse of the American Oligocene)
1891. Flower, W. H. The Horse. London: Kegan Paul, Trübner
61
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1896. Wortman, J. L. Species of Hymeotherium, etc. Buil. A. M. N. H.,
vol. viii, pp. 81-110. (Revision of the species of four-toed horses
from the Lower Eocene of North America)
1900.     Lucas, F. A. The Ancestry of the Horse. McClure's, vol. 15, pp.
511-517, October. (Popular account with diagrams, etc.)
1901.     Gidley, J. W. Tooth Characters and Revision of the North Ameri-
can Species of the Genus Equus. Buil. A. M. N. H., vol. xiv,
pp. 91-142. (Revision of the prehistorie wild horses of the
United States)
1903.     Maïthew, W. D. Evolution of the Horse. Guide Leaflet, No. 9,
Am. Mus. Journ., vol. iii, No. 1 (Jan.). Second edition, 1905.
(Popular guide to fossil horse specimens in American Museum)
1904.    Ewart, J. C. The Multiple Origin of Horses and Ponies. Wash-
ington: Smithsonian Report [1905] pp. 437-455
1904. Hayes, M. H. Points on the Horse New York: Scribners
1904. Osborn, H. F. New Oligocene Horses. Buil. A. M. N. H., vol. xx,
pp. 167-179. (Species of three-toed horses from the American
Oligocene)
1904.     Osborn, H. F. The Evolution of the Horse in America. Century
Magazine, vol. lxix, pp. 1-17, November. (Popular account of
the ancestry of the horse and of the origin of the several modern
breeds)
1905.     Clarke, W. H. Horses' Teeth. (4th ed.). New York: Jenkins.
1905. Osborn, H. F. Origin and History of the Horse. Address before
the New York Farmers, Metropolitan Club, Dec. 19. (Popular
account of the origin of the modern breeds of horses and of the
horse family in general)
1907. Lull, R. S. The Evolution of the Horse Family. Am. Journ.
Sci. (4), vol. xxiii, pp. 161-182. (Popular guide to fossil horse
specimens in Yale Museum)
1907.     Gidley, J. W. Revision of the Miocene and Pliocene Equidse of
North America. Buil. A. M. N. H., vol. xxiii, pp. 865-934.
(Revision of species of later three-toed horses, with observations
on the phylogeny)
1908.     Granger, Walter. A Revision of the American Eocene Horses.
Buil. A. M. N. H„ vol. xxiv, pp. 221-264. (Revision of species
of four-toed horses)
1910. Sisson, Septimus. Text-Book of Veterinary Anatomy. Phila-
delphia: Saunders
1912. Liautard, A. F. A. How to Teil the Age of the Domestic Animal.
New York: Jenkins
1912. Lydekker, R. The Horse and its Relatives. New York: Mac-
millan
62
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INDEX
Page numbers of illustralionfs are set in heavy face type
Meaning of change in f eet and teeth,
25-29
Merychippus, 10, 11, 20, 29, 30
Mesohippus, 10, 11, 17, 31; intermedius,
17; bairdi, 18, 28
Miohippus, 17, 28, 30
Molars, 9, 52, 56
" Nimr," 38, 43
Norseman's horse, 37, 39, 42
One-toed horses, 21-22
Orohippus, 16, 28
Osborn, H. F., 13, 17, 21, 37, 43
Owen, Richard, 14
Palmotherium, 16
Parahippus, 17, 20, 28
Plagiolophus, 16
Plateau type, 13
PUohippus, 20-21, 22
Prehistorie man, 13, 37, 39
Premolars, 52, 55
Prolohippus, 20-21
Pseudo-horses, 32, 33
Quagga, 13
Race horse, 37, 43-44, 45
Ridgeway, William, 37, 42
Shetland pony, 36, 37, 41-42; com-
pared with draft horse, 36, 41
Skeleton of horse and man, 2, 39
Steppe type, 13
"Sysonby," 44, 45
Teeth of colt, 59
Teeth of horse, 9, 44-60, 57; designa-
tion, 50-51; eruption of, 58-60;
evolution of, 28; pattern of enamel,
54; shedding, 60, specialization, 47,
structure, 46-48; wearing of, 47,48,53
Teeth of Equus, 22, of Eohippus, 15, of
Epihippus, 16, of Hipparion, 21; of
Merychippus, 20, of Mesohippus, 17;
of Orohippus, 16; of Parahippus, 20
Thoatherium, 33
Three-toed horses, 17-21
Touchstone, S. F., 43
Whitney, William C., 2, 38
Wolf tooth, 51-52
Wortman, J. L., 15
Zebra, 11, 13, 31
Adaptation to environment, 28, 31
Age determination by teeth, 49
Anchitherium, 17
Arabian horse, 13, 38, 42-43
Ass, 11: African wild, 13, 31
"Byerley Turk," 43
Cuvier, Baron, 16
Darley Arabian, 43
Dental battery of adult horse, 57
Dental star, 47, 49
Desert type, 13
Diadiaphorus, 32, 33
Domestic horse, Origin of, 37
Draft horse, 36, 37, 38, 39-41, 40
Eohippus, 10, 11, 15-16, 28, 30; venti-
colus, 18
Epihippus, 16, 28
Equus, 10, 11, 12, 13, 21-22, 30; asinus,
9, 13; burchelli, 9; caballus, 29; com-
plicalus, 29; grevyi, 9; hemionus, 9;
libycus, 37; przewalskii, 13, 39; scotti,
12, 22, 23; sterwnis, 29; zebra, 9
Equus Beds, 13
Evolution, Cause of, 31; Parallel, 32-33
Evolution of the Horse, 8, 14, 34-35;
of fore foot, 10; of fore leg, 26; of
hind foot, 11, 30; of hind leg, 27
Ewart, J. C, 37, 41
Foot, Evolution of, 10, 11
Forest type, 13
Fossil horses, 12-13
Four-toed horses, 14-16
Geological range of ancestors of horse,
25
Gidley, J. W., 12
Godolphin Arabian, 43
Granger, Walter, 16
Hipparion, 20, 29, 30; whitneyi, 19, 21
Hippidium, 13, 22, 24
Huntington, Randolph, 38, 43
Hypohippus, 17
Hyracotherium, 14, 15, 27
Keene, James R., 44
"Kismet," 43
Leg, Evolution of, 26, 27
Libyan horse, 42-43
Litopterna, 32
83
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POPULAR PUBLICATIONS
OF THE
AMERICAN MUSEUM OF NATURAL HISTORY
ILLUSTRATED GUIDE LEAFLETS
These describe some exhibit, or series of exhibits, of special interest or im-
portance, or may deal with the contents of an entire hall.
Many of the earlier leaflets are out of print, but new editions of those most
in demand are in course of preparation.
THE COLLECTION OF MINERALS. By Louis P. Gratacap, A.M., Curator
of Mineralogy. February, 1902. Price, 5 cents.
The minerals have been moved since this leaflet was issued, but it contains
much information about the collection and a number of figures of interesting
specimens.
NORTH AMERICAN RUMINANTS. By J. A. Allen, Ph.D., Curator of Mam-
malogy and Ornithology. Revised edition, February, 1904. Price, 10 cents.
Describes the rapidly disappearing large game of North America, such as the
bison, elk and mountain sheep.
THE ANCIENT BASKET MAKERS OF SOUTHEASTERN UTAH. By
George H. Pepper, Assistant in Anthropology. April, 1902. Second edition,
May, 1909. Price, 10 cents.
PRIMITIVE ART. July, 1904. Price, 15 cents.
THE BATRACHIANS OF THE VICINITY OF NEW YORK CITY, By Ray-
mond L. Ditmars, Curator of Reptiles, New York Zoölogical Park. October,
1905. Price, 15 cents.
THE BIRDS OF THE VICINITY OF NEW YORK CITY. By Frank M.
Chapman, Curator of Ornithology. April-July, 1906. Price, 15 cents.
PERUVIAN MUMMIES. By Charles W. Mead, Assistant Curator, Depart-
ment of Anthropology. March, 1907. Price, 10 cents.
THE METEORITES IN THE FOYER OF THE AMERICAN MUSEUM OF
NATURAL HISTORY. By Edmund Otis Hovey, Ph.D., Curator, Depart-
ment of Geology and Invertebrate Palaeontology. December, 1907. Price,
10 cents.
The collection, which represents about 500 falls, numbering some 2,000 speci-
mens, includes the great "Ahnighito" meteorite, weighing 36| tons, brought
from Greenland by Peary, the strange "Willamette" meteorite and the "Canyon
Diablo" which contains minute diamonds.
THE HABITAT GROUPS OF NORTH AMERICAN BIRDS. By Frank M.
Chapman, Curator of Ornithology. February, 1909. Price, 15 cents.
These celebrated groups are design ed to illustrate not only the habits but also
the haunts, or habitats, of the species shown. The backgrounds are careful
studies from nature and each represents some definite locality. Twenty-two
of these groups are shown in this leaflet.
THE INDIANS OF MANHATTAN ISLAND AND VICINITY. By Alanson
Skinner, Assistant Curator, Department of Anthropology. September, 1909.
Price, 10 cents.