MANUAL OF EQUINE MEDICINE. 



The sub-order Perissodactyla com^Drises three living 

 families : the Tapiridse, or Tapirs ; the Equidse, or Horses ; 

 and the Khinocerotidse, or Ehinoceroses. There are also 

 several extinct families : the Macraucheniadse {iMaxpog, long, 

 and au-)(7iv, neck) ; the Palaeotheres {'TraXaiog, old, and ^fi^iov, 

 beast); and the Lophodontia {'ko(pog, a crest, and Ihoug, 

 a tooth). 



The Perissodactyles have no fewer than twenty-two dorsi- 

 lumbar vertebrse. They have a third trochanter on the 

 femur, and the third digit of each foot is symmetrical. 

 Horns, when present on the head, are only skin deep, are 

 always placed on the middle line of the skull, as in the 

 Ehinoceros, and have no bony core. 



The number of toes in the Perissodactyles is reduced to 

 a minimum. 



The hind-foot of the Tapir has three well-developed toes, 

 and these are homologous with the second, third, and fourth 

 digits of man. 



In the Ehinoceros all the feet are provided with three 

 toes formed of the same three digits. 



In the Horse there are further reductions ; for that digit 

 which corresponds with the third or middle digit of man is 

 the only one which remains intact. There are, however, 

 two rudimentary digits in addition, and these are called 

 the splint-bones. They are homologous with the second 

 and fourth digits of man. 



The Perissodactyles are first represented in geological 

 strata of the Old World by the Lophodontia. These ex- 

 tinct forms, which are found in the Eocene strata of France 

 and England, were closely allied to the Artiodactyles. 

 As in the latter, their pre-molar teeth were simpler and 

 longer than the molar teeth. The feet of the Lophodons, 

 however, were of the Perissodactyle type. 



Of all existing Ungulate animals, the Lophodon comes 



