FATS, PHOSPHATIDS, ETC. 89 







II 



CH 2 C--R 







CHO C R 

 CH 2 . 



CH 2 CH 2 N (CH 3 ) 3 OH 



\ / 



P 



/ \ 

 OH 



The functions of lecithin in the body are not perfectly under- 

 stood. Recent studies have made it seem probable that much 

 of the "fat" of the tissues, and the blood is in reality lecithin. 

 It appears that the body easily synthesizes lecithin, so that it is 

 not a necessary constituent of the diet. In fact the lecithin of 

 the food probably is hydrolyzed by the lipase in the intestine 

 into its constituent parts. Undoubtedly the lecithin in the cells 

 aids them in holding water. Various other functions have been 

 suggested, but in most cases the evidence is not conclusive. 



Cholesterol. Cholesterol is a substance which resembles the 

 fats in some of its physical properties, but has little relation 

 to them chemically. It is widely distributed in nature, and is 

 found in large amounts in the brain and nerve tissue. It oc- 

 curs also in small amounts in the blood, and in the bile, from 

 which it is occasionally deposited in gall stones, whence it is 

 most easily obtained. Cholesterol is insoluble in water, acids, 

 or alkalies. It is readily soluble in hot alcohol, in ether, chloro- 

 form, benzol, etc. Cholesterol crystallizes from hot alcohol or 

 other solvents, forming large colorless plates. It gives many 

 color reactions. If a chloroform solution of cholesterol is care- 

 fully treated with concentrated sulphuric acid so as to form a 

 layer of acid at the bottom of the test tube, the chloroform solu- 

 tion becomes a brilliant red, and the acid layer dark red with a 



