202 ON THE CALLOSITIES ON THE LIMBS OF THE EQUIDA. | Mar. 3, 
bristles in the Dassies (Procavia) is very important. Mr. Beddard 
states that these are the only ungulates in which he has found 
these bristles. Carpal callosities are, however, described by 
Dr. W. Leche’ as occurring in Wart- Hogs (Phacocherus); although 
they are stated by their deseriber to be acquired, and not primitive 
structures. Whether the latter statement is calculated to modify 
Mr. Beddard’s opinion with regard to the nature of the carpal 
bristles in the Dassies, I am, of course, unable to say. Of special 
importance is the occurrence of bristles in these structures, since, 
even if hairs be found to exist on the callosities of foetal Hquide, 
this would be no bar to the supposition of their glandular nature. 
As regards the structure of the callosities themselves, it may be 
noted that in the Horse both pads are of a distinctly warty nature, 
and that the hind pair are certainly in a more decadent condition 
than the other, being in fact on the verge of disappearing. In 
the Zebras, on the other hand (in which the hind one has been 
lost), the fore-callosity is larger and much less warty and also 
situated higher up. In dried skins it is, in fact, much more like 
the pale glandular patch of skin below the ear of a Reedbuck’. 
In this connection we have to bear in mind not only Mr. Beddard’s 
observations alluded to above, but likewise others by Mr. Bland 
Sutton’, in which it is pointed out that in certain Lemurs decadent 
glands are actually converted into bunches of spines, which are 
practically almost the same as warts; that is to say, they are 
hypertrophied growths of somewhat abnormal dermal tissue. 
Hence there seems no primd facie reason why the callosities of 
the Hquide should not be decadent glandular structures, the 
decadence being more marked in the two pairs of callosities of the 
Horse than in the single pair of the Asses and Zebras. 
There is, however, another point which may have an important 
bearing on the subject. From the presence of a depression in 
the skulls of Wipparion, Hippidiwm, &e., it is evident that 
primitive Horses were furnished with face-glands comparable to 
those of Deer; such glands probably having a function somewhat 
analogous to that of the scent-glands on the limbs of the latter. 
If, then, the existing Hquwide have got rid of their face-glands, as 
being (perhaps on account of change of habit) useless, it is con- 
ceivable that, for the same reason, they may have also discarded 
their limb-glands. 
If these suppositions (and they are but suppositions) be well 
founded, it follows that a tarsal and a carpal gland must have 
existed in the common ancestors of the Horses and Deer ; that is 
to say, in the common stock of all modern Ungulates save the 
Elephants and perhaps the Dassies. And it may be urged that if 
this were the case, traces of such glands ought to be met with in 
Tapirs, Rhinoceroses, Pigs, Hippopotamus, &. So far as I am 
1 Biol. Centralblatt, vol. xxii. p. 79 (1902). 
2 It would be important to examine the histological structure of .the callosity in a 
Zebra. 
3 Proc. Zool. Soc. 1887, p. 369. 
