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 verte- 

 brae. 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 w r hich 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 37 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): 



36 



