ZOOLOGICAL GARDENS, 
33 
The Equidae, or Family of Horses, belong to the ungu¬ 
late or hoofed division of Mammalia, and to that section 
known as the Perissodactyla , or those possessing an odd 
number of toes on the hind foot, in contradistinction to the 
Artiodactyla , which have an even number. 
The Perissodactyle mammals are the Horses, including 
the Asses, the Rhinoceroses, and the Tapirs. The foot of 
the horse and ass corresponds to the terminal bone of 
the middle finger or toe of man, on which the nail is 
placed, the nail becoming the hoof in the horse, hence 
horses and asses walk on the tips of the nails of their 
third or middle finger and toe, the other fingers or toes 
not being developed except as mere rudiments of the se¬ 
cond and fourth, known as splint-bones. The so-called 
knee of the horse is thus its wrist in the foreleg, and the 
hock is the equivalent of the heel. The little round or 
oval horny plate found on the inner surface of the fore¬ 
arm and hind-leg of the horse is known as the chestnut, 
whilst the little corneous mass growing on the fetlock is 
known as the ergot. The chestnuts and ergots are always 
less developed in the finer breeds of horses. Chestnuts are 
absent from the hind limbs of asses. 
In connection with the teeth of horses and asses, the 
incisors or front teeth give only an approximate indica¬ 
tion of age. These teeth have a deep valley of irregular 
outline, which becomes filled up with masticated matter, 
and this gives rise to what is called the dark . mark. As 
the tooth wears away, the form of the valley changes and 
it becomes more shallow, and ultimately, by friction, the 
whole of the valley disappears. The degree to which this 
change has proceeded gives the indication of age. 
Horses, unlike the majority of animals, are unable to 
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