132 The North American Cervidce. 



men side-bones or splints, which lie hidden beneath the skin, close to 

 the large third digit, metacarpal or metatarsal. 



Now the ox is an artiodactyle. His weight is supported on the 

 tips of two toes, which represent the third and fourth digits of the 

 human hand, or foot, as the case may be. The first has been wholly 

 lost, but the second and fifth are represented by the two little supple- 

 mentary hooflets behind and above the main hoofs. The functional 

 hoofs are symmetrical in pairs, the third and fourth digits being 

 equally developed, and taking an equal part in the constitution of 

 the foot and in performing its work. The metacarpals and metatar- 

 sals of the third and fourth digits are equally developed, but are 

 anchylosed together, so that they appear like a single bone, with, how- 

 ever, two distinct articular surfaces at their lower ends to support the 

 phalanges of the digits. The Cervidce belong to the Artiodactyla, 

 and their feet are constructed upon the same plan as those of the ox. 

 They are also ruminants, and belong in a subdivision of the Artio- 

 dactyla styled Pecora, to which belong the Camelopardidce (giraffes) 

 and Bovidce (cattle, sheep, and antelopes). 



All the Cervidce have horns, and these alone are enough to distin- 

 guish this family from any other. The horns of the Bovidce are per- 

 manent osseous outgrowths from the frontal bone of the skull, and are 

 enclosed in a horny epidermic sheath, which is usually persistent, a 

 single species — our prong-horn antelope — being the only exception 

 to the rule. These bony outgrowths, which form the core of the horn, 

 are usually permeated by large air sinuses, and from this fact the 

 group have been called Cavicornia (hollow-horned). In the deer 

 family, however, the horns are constructed on quite a different plan. 

 They are still outgrowths of bone from the frontals, but the outer 

 epidermic sheath encloses them for a short time only, and, as soon as 

 their growth is completed, is shed. The perfect horn is now mere 

 dead bone. It remains firmly attached to the skull for a few months, 

 and then drops off, to be renewed again the following year. These 

 horns are, in fact, true bones, and in their constitution do not differ 

 materially from the other bones of the body. 



Their method of growth is as follows : From each of the frontal 

 bones there arises a short, stout process, growing outward and up- 

 ward, forming what is called the pedicel. This pedicel is covered 



