THE SKELETON. 



The number of bones in the skeleton of the cat varies 

 with its age, since two or more bones separate in the young 

 may form one mass in the old animal. The three portions 

 of the innominate bone which are distinct (Fig. 38) in the 

 young, become fused in the adult. In very old age many 

 sutures of the skull become partially or wholly obliterated. 

 In the young adult cat the number of bones, exclusive of the 

 teeth, ear bones, chevron bones, and sesamoid bones, is 

 about 233. The sacrum is reckoned as one bone, though 

 composed of three coalesced vertebrae. The structure and 

 embryology of the teeth show that they belong to a different 

 category from the bones. The ossicula auditus, or ear 

 bones, are the malleus, incus, and stapes of the middle ear. 

 The chevron bones are eight in number, attached to the 

 ventral side of the vertebrae of the tail. The sesamoid bones 

 number about forty, of which the patella, or knee-cap, is the 

 largest. They are formed in the tendons where there is 

 much pressure or friction, as upon the volar surface of the 

 metacarpus. The outline on page 22 gives the classifica- 

 tion, names, and number of the different bones of the 

 skeleton. 



GENERAL TERMS USED IN DESCRIPTION OF 



BONES. 



In reference to shape the bones are spoken of as long, 

 short, flat, and irregular. Long bones are those having a 

 shaft or diaphysis in which is a cavity filled with marrow, 

 and two enlarged extremities or epiphyses (Fig. 13) : 

 femur, fibula, metacarpals, and phalanges. Short bones 



21 



