186 
ON THE ERGOT OE EQUIDAE 
inti) fiiur classes as I have ahead)' described. 
hi the hoof, lu)\ve\'cr, at the earl)- enibr)'ological stage, the Papillae are 
(jiiite simple. 
The above results of my own observations show that the Callosity and 
Ergot which the present Equidae carry must be rudimentary toes. 
I now wish to write of the frog, which, found in the hind })art of the 
hoof, of Equidae, is a rudimentary pad which belongs to the toe, in order to 
ascertain its morphological connection with the Callosity and Ergot. 
I have measured the frogs of various kinds of Equidae with the follow- 
ing results : 
Race Name 
Fore Hoof 
Hind Hoof 
a. b. 
c. d. 
e. f. 
g. h. 
a. b. 
c. d. 
e. f. 
S 
h. 
Equus Burchelli 
Sh cm 
1 1 cm 
6,2cm 
1 i cm 
7-I cm 
10 cm 
6h cm 
2 
cm 
Equus Grevj'i 
3,2cm 
8,2cm 
6,2cm 
1 ,5cm 
4 cm 
8 cm 
7 cm 
2 
cm 
Equus Cha])nani 
(a) left side 
61 cm 
1 1 Icm 
6 cm 
2I cm 
7 cm 
10 cm 
6 cm 
3 
cm 
Equus Chapnani 
(b) right side 
6 cm 
io,2cm 
6,4cm 
1 ,4cm 
5,8cm 
1 0 cm 
7 cm 
2 
cm 
a. b distance of two bases of bulbar expansion of periopilic ring, which 
is seen to be continuous with the sensitive frog 
c. d ...distance between middle point of frog base and point of hoof 
e. f length of frog 
g. h breadth of frog 
As these show, with most Equidae, the frog of the hind foot is always 
larger than that of the fore foot, especially in the Kiang and Grev\''s zebra, 
where the frog of the hind foot touches the ground. It is clear that this has 
come from the fact that the angle which the hind foot makes with the ground 
is always smaller than that of the fore foot. We can tell that the present 
frog is still useful as a i)ad to the hoof. For the same reason we may infer 
that the Ergot formerly served as a support to the foot and was used at a later 
period b)- the hind foot than by the fore, and is therefore more rudimented on 
