NUTRITION 99 



of two kinds of material the organic matter, which consists 

 mainly of collagen and fat (pp. 40, 77), and the so-called 

 mineral matter, which consists mainly of tricalcic-ortho- 

 phosphate (p. n). These two kinds of matter are intimately 

 associated. It is the phosphate of lime which gives rigidity 

 to the bones. The collagen acts as a kind of cement and 

 holds the particles of mineral matter together. 



The relative proportions of mineral and organic matter 

 vary considerably according to the age of the animal. When 

 the animals are young, the percentage of phosphate of lime is 

 comparatively small, but it increases rapidly as they approach 

 maturity. In general, the proportions of mineral and organic 

 matter are roughly about five of the former to four of the latter. 

 The following analysis shows the average composition of 

 mamalian bones in the fresh or green state. 



AVERAGE COMPOSITION OF BONES PER CENT. 



Water .... 67 67 



Organic matter . Wg^ * = ^ Q% nitrogen 



P 2 5 22-3 = 487 %Ca 3 (P0 4 ) 2 



Ash .... 53-3 < CaO 29-2 



( MgO.F, etc. r8 



lOO'O lOO'O 



The red flesh or muscular tissue, the skin, organs, nerves 

 and vessels, all consist mainly of protein compounds. Even 

 cartilage and the horny matter of hoofs, etc., are of this nature 

 (p. 78). In the soft parts, the protein is associated with 

 a large amount of water and, usually, with a small amount of 

 fat. It is commonly believed that the flesh of lambs, calves, 

 and young animals generally is of a more watery character than 

 that of the corresponding animals, sheep, oxen, etc., in the 

 mature condition. According to the analyses of Atwater and 

 Bryant l the ratio of water to protein is very much the same in 

 the corresponding parts of various animals ; and it does not 

 differ very widely even in the different organs and parts of 



1 Bui. 28 of Exper. Stations, U.S. Dept. of Agriculture. 



