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Bones of a Pig's foot. (See also [Appendix C].) |
We now come to the second division, and a very large one, of the UNGULATA, which in itself is again subdivided into non-ruminants and ruminants. The former comprises the pigs of the Old and the peccaries of the New World and the hippopotami; the latter contains the camels, llamas, deerlets, oxen, antelope, and deer. In the Artiodactyla the toes are even on all feet, being normally four (perfect and rudimentary) with the exception of the camel, giraffe and a few antelope, in which two only are present. To understand the subject thoroughly one must compare the fore-foot of a deer or pig with our own hand; what we call the knee of the former is merely our wrist. The bones which run through the palm of the hand to the knuckles are the metacarpals; they are five in number, corresponding with the thumb and four fingers. In the Artiodactyla—or, I should say, in the Ungulata generally—the thumb is entirely wanting; in the Artiodactyla the fore and little fingers are shorter, rudimentary, or entirely wanting, and the two centre metacarpals, the middle and ring fingers are prolonged into what we call the leg below the knee in these animals, which consist of separate or fused bones terminated by the usual three joints of the finger, on the last of which is placed the hoof.
The two halves are always symmetrical, and from this we may affirm that it is the thumb and not the little finger which is absent, for we know that, counting from the knuckles, our fingers have three joints, whereas the thumb has only two; so in the digits of the Artiodactyla are three joints at the end of each metacarpal. In the pig the metacarpals of the fore and little fingers are produced from the carpus or wrist, or, as is popularly termed in the case of these animals, the knee. They are more attenuated in the chevrotians or deerlets, of which our Indian mouse-deer is an example; in the Cervidæ they are more rudimentary, detached from the carpus, and are suspended free and low down, forming the little hoof-points behind; and a little above the proper hoofs in these the two large metacarpals are more or less joined or fused into one bone, and they are still more so in the camel, in which the fore and little finger bones are entirely absent. In the giraffe and prong-horn antelope they are also wanting. The hind feet are similarly constructed.[32]
32 See notes in [Appendix C].
Of the non-ruminantia we have only the Suidæ—the peccaries belonging to America, and the hippopotami to Africa.
These have incisors in both jaws, which vary in number, the lower ones slanting forward. Their canines are very large and directed outwards and upwards in a curve, grinding against each other to a sharp edge and fine point. Their metacarpal bones are four in number, and are all distinct, in which respect they differ from the peccaries, in which the central metacarpals and metatarsals are fused into a solid bone. The hogs have a prolonged snout, flexible at the end, with a firm cartilaginous tip, with which they are enabled to plough up the ground in search of roots. They have also a very keen sense of smell. The normal dentition of the true hogs is as follows:—
Inc., 6/6; can., 1—1/1—1; premolars, 4—4/4—4; molars, 3—3/3—3 = 44.