ANIMAL CHEMISTRY. 407 



acid. More than one fifth of the solid matter of the brain 

 is fat, and this substance constitutes more than a sixth 

 part of the solid matter of muscle. It is present in con- 

 siderable quantity, also, in other structures. It must, then, 

 have other uses besides heat-making. Besides its useful- 

 ness in the textures of organs, it is of some local benefit as 

 deposited in masses. Thus the eyeball rests in its socket 

 upon a cushion of fat. 



577. Phosphorus and Sulphur. Phosphorus does not ex- 

 ist as such in animals, but is in combination with soda and 

 lime. The phosphate of lime is present in large quantity 

 in the bones. In the body of an adult man there is in the 

 bones from 2 to 3 kilogrammes of this salt, and the phos- 

 phorus in it amounts to from 500 to 800 grammes. Phos- 

 phorus forms one of the most important constituents of cer- 

 tain complex fatty bodies in the brain. It is extensively 

 provided for animals in their articles of food, mostly in 

 the form of phosphate of lime. Phosphorus exists in eggs, 

 and in all animal food. It is one of the components of 

 milk, the universal and sole food of the mammalia in their 

 infancy. It is also present in many seeds. So abundant is 

 it in oats that the horse is liable to an earthy concretion 

 in the bowels, of which phosphorus is a chief ingredient. 

 Sulphur also occurs in combination in animals, chiefly in 

 the albuminous or protein substances, and in some of the 

 tissues. It comes from both animal and vegetable sources. 

 Like phosphorus, it exists in flesh, eggs, and milk. It is also 

 in the nitrogenous compounds of plants, gluten, albumen, 

 and casein ; and, combined with lime in the form of a sul- 

 phate, it is in most of the water that we drink. 



578. Lime. This is one of the most widely diffused min- 

 eral substances both in the animal and vegetable kingdoms. 

 It exists largely in the seeds of most grasses, especially in 

 the grains of wheat. Beans and pease have more nitroge- 



