318 



PRACTICAL PHYSIOLOGY 



products. For example, when they are saponified, as above described, 

 they yield fatty acid, glycerinphosphoric acid and cholin. G-lycerine- 

 phosphoric acid is readily formed by bringing together glycerine and 

 phosphoric acid. 



CHOLESTEROL. 



Although soluble in the same solvents as fats and the lecithins, 

 cholesterol is not a fat, but belongs to an entirely different 



FIG. 22(5. Crystals of cholesterol magnified 300 diameters. 



chemical group, namely, that of the terpenes. The terpenes are 

 common in plants, examples of them being camphor and turpentine. 

 By its reactions, cholesterol can be shown to contain a double linking 

 and an alcohol-hydroxyl group. The following formula has been sug- 

 for it : 



(CH 3 ) 2 = CH - CH 2 - CH 2 - C 17 H 26 - CH = CH 2 



CH 2 CH 2 

 CH(OH). 



