2/0 SOLID-HOOFED PIGS 



of these, and that which has given its name to the group, 

 concerns the arrangement of the digits. Instead of there being 

 but one prevailing digit — the third, in the hand and foot, 

 tlirough which the axis of the foot passes, there are two, numbers 

 tliree and four, between which the same axis passes, and which 

 are perfectly symmetrical with each other. This type of foot has 

 been termed " paraxonic," as opposed to the " mesaxonic " Perisso- 

 dactyle foot (see Fig. 121 B, p. 235). It has been attempted 

 to prove that the single prevailing digit of the Horse's foot is a 

 fused pair of digits, and the state of affairs which characterises 

 the Camel, where the two metacarpals or metatarsals are to an 

 almost complete extent united, has been urged in proof; so, 

 too, certain abnormalities, such as those called " solid-hoofed 

 pigs." ^ These latter are simply Pigs in which the two central 

 metacarpals and the terminal hoofs are completely fused with one 

 another. In some of such cases there is not the slightest trace of 

 the union of the separate metacarpals and phalanges. Even the 

 sesamoid bones, attached behind to the toes, are two in number 

 instead of four. And, furthermore, the tendon supplying the 

 bones is single, though showing traces of its double origin. 

 Such Pigs often show the abnormality from generation to genera- 

 tion, and they proved convenient for those whose scruples would 

 not allow them to eat the flesh of a beast " dividing the hoof " 

 and not chewing the cud. More singular still, as showing a 

 pathological approach from another side to the Perissodactyle 

 condition in an Artiodactyle, is a calf, where the foot ended in 

 three equi-sized digits, of which the middle one lay in the longi- 

 tudinal axis of the limb. Prom the opposite side cases are 

 known of a Horse with a split hoof and phalanges, thus present- 

 ing the most striking likeness to a <Jamel. 



There is, furthermore, in certain groups of Artiodactyles 

 (e.g. the Tragulidae) a tendency for the two middle metacarpals to 

 unite, quite apart from such " sports " as those illustrated by the 

 cases just set forth. And, as already mentioned, the union of the 

 two middle metacarpals culminates in the Camel, Ox, etc. There 

 is, however, absolutely no trace of such a fusion in the series of 

 Perissodactyle animals known to us ; and it would be by fusion 

 rather than dismemberment that, as it would appear on this 

 theory, the modern Ungulate foot has been arrived at. Of course 



' See Bate.son, Materials for the Study of Variation, London, 1894, p. 387. 



