FAT — BONE. 231 



nature to vegetable oil : some kinds of fat are solid, 

 others fluid, at common temperature ; but they all 

 become fluid when made sufficiently hot ; animal oils, 

 like those of vegetable origin, contain no nitrogen — 

 they consist of carbon, oxygen, and hydrogen, and 

 when burnt form carbonic acid and water ; like ve- 

 getable oils, also, they consist of margarine, stearine, 

 and oleine, united to a peculiar base (513), and con- 

 sequently they form soap when boiled with alkalies. 



595. The bones of animals contain a very large 

 proportion of earthy matters ; and, indeed, derive 

 their strength and solidity principally from the quan- 

 tity of those substances which they contain. When 

 bones are burnt, there remains, after the combustion 

 of all the organic matter which they contain, about 

 three quarters of their weight of earthy substances ; 

 this is phosphate of lime, together with a small por- 

 tion of carbonate of lime ; bones consist of phosphate 

 and carbonate of lime, cemented together as it were 

 with gelatine and a little albumen ; they also contain 

 a small quantity of oil. Ivory and the teeth of ani- 

 mals are composed of the same substances as bone. 

 Hoofs and horn likewise contain phosphate and car- 

 bonate of lime, but in far less quantity ; they consist 

 principally of gelatine (589). 



596. The same remarkable similarity of chemical 

 composition which is found amongst vegetable sub- 

 stances, is likewise observed amongst those of animal 

 origin ; the various proximate elements which consti- 

 tute the bodies of animals, are, for the most part, 



