HANDS AND FEET. 291 



and surrounding a dense cushion on which the limb and super- 

 incumbent weight of the body reposes. 



In the Pig we have an animal each extremity of which is 

 furnished with but four digits, both the pollex and the hallux 

 being absent. These four digits are arranged in two pairs both 

 on the hand and on the foot, there being a large strong pair of 

 digits in the middle, on which the animal walks, with a small 

 digit placed external to and behind each of the two large ones. 

 The nails are represented by strong horny structures which 

 encase and enclose the terminal phalanx. Such a massive 

 sheathing nail is called a "hoof." The digits on which a Pig 

 walks correspond with our third and fourth fingers and our third 

 and fourth toes. 



In ruminating animals, such as oxen, sheep and deer, the 

 number of digits is reduced to two, which are the same two as 

 as those which support the Pig in locomotion ; whereas in the 

 Pig, however, each of the metacarpals and metatarsals remains 

 distinct. In ruminants the third and fourth metacarpals and 

 the third and fourth metatarsals unite together to form one 

 single bone called a " cannon bone." 



In a small animal called the Jerboa (Dijms), which has no re- 

 lation to cattle, but is allied to the rats, a still further coalescence 

 of metatarsals takes place. This little animal has three toes 

 (the second, third, and fourth) to each foot, and these three 

 digits are supported by a long single metatarsal bone which really 

 consists of the second, third, and fourth metatarsal bones united 

 into one. 



In the Ehinoceros there are also three digits to each extremity, 

 but the metacarpals and metatarsals remain distinct. 



In the Horse we meet with the extreme of reduction in regard 

 to the number of digits, but with a great development of them in 

 size. The popular notion is, or at all events was, that the foot 

 of a Horse was an undivided one, that it answered to that of the 

 Ox " uncleft." If so, the metacarpal and metatarsal bones, each 

 of which is manifestly single, must be a " cannon " bone, and 

 made up of more than one such bone forced, as it were, together. 

 Such, however, is not the case ; each foot of a Horse consists of 

 but a single digit only, answering respectively to our middle 

 finger and our middle toe, the enormously enlarged nail of such 

 finger, or toe, having become the Horse's hoof. The Horse 



