1 74 ON THE ERGOT OF EQUIDAE 
In the British Museum I have observed the following different equine 
breeds : 
Equus grevyi (?). Ergot on fore and hind feet, very large on hind feet. 
Equus samalicus. Ergot on fore feet i i mm. broad, 2^ mm. long, on hind 
feet, 2h mm. broad, 3 mm. long. 
]^urchell's Zebra (Eq. burchelli selousi). Ergot on fore foot smaller 
tlian on hind foot. 
Grey's Zebra. (Eq. grevyi). Ergot on fore and hind foot, that on hind 
very large. 
As these specimens are stuffed the skin has shrunk somewhat causing 
the Callosity and Ergot to become smaller, but as I only desire to compare 
the relative sizes of fore and hind Callosities and Ergots this shrinking is of 
no account. Professor Zietzmann's research in the case of the Ergot has 
been very thorough. He says that among hinnics the Ergot grows as with 
horses to a considerable thickness (over 2 cm.), that those on the hind feet 
have the larger surf;ice, the greatest diameter of which sometimes exceeds 
2 cm. In the case of mules he had made no observations. 
As I have said above, from the microscopic studies, the Ergot, in contra- 
distinction to the Callosity which is of the same size on fore and hind feet, 
is always larger on the hind feet. 
In my conclusion I wish to give an explanation of this. 
In the first place, to examine the theory of many histologists that the 
Ergot is a rudimentary pad, I have compared it with the toe pad and central 
pad of dogs and cats, and in particular with the carpal pad which, at the pre- 
sent time, is not used by its possessor. 
If the Ergot is a rudimentary pad it was formerly used by its possessor 
as a pad, and in my opinion its histological structure should be similar to, or 
the same as, that of the pads of dogs and cats. I have, therefore, first made 
histological studies of the pads of domestic cats and dogs as follows : 
