308 THE CHEMISTRY OF ANIMAL PHYSIOLOGY 



cent, oxygen, 9 per cent, hydrogen, 6 per cent, nitrogen, and 

 11 per cent. ash. This analysis may be taken as fairly 

 representative. It shows (cf. Section 14) that there is a 

 much larger proporton of carbon to oxygen in animals than 



Fig. 74. — Farm animals. 



in plants, and more nitrogen. This is because the dry 

 matter of animals consists mostly of fats and proteins, 

 whereas the dry matter of plants consists largely of carbo- 

 hydrates and crude fiber. The cell walls of plants are made 

 of cellulose, but the cell walls of animals are made of protein. 



