THE VOLATILE PART OF PLANTS. 123 



imperfectly crystallizable, similar to protagon in their 

 deportment toward water, and readily decomposed into 

 cholin, glycerophosphoric acid, and one or more fatty 

 acids. Three lecithins appear to have been identified, 

 yielding respectively, on decomposition, stearic, palmitic, 

 and oleic acids. 



The formula C 44 H 90 NP0 9 is that of distearic lecithin, 

 which is composed of glyceryl, C 3 H 5 , united to two 

 stearic acid radicals, and also to phosphoric acid, which 

 again is joined to cholin, as represented by the formula 



\OPO 



Lecithin is believed to be a constant and essential in- 

 gredient of plants and animals. 



Protagon, CieoHgosXePOss, discovered by Liebreich in 

 the brain of animals, has been further studied by Gam- 

 gee & Blankenhorn. It is a white substance that swells 

 up with water to a gelatinous mass and finally forms an 

 opake solution. From solution in ether or alcohol it can 

 be easily obtained in needle-shaped crystals, whose com- 

 position is given below. Alkalies decompose protagon 

 into glycero-phosphoric acid, stearic and other fatty 

 acids, and cholin or neurin. Protagon was formerly 

 confounded with lecithin and thought to exist in plants, 

 but its presence in the latter has not been established. 



Protagon. Lecithin. 



Carbon ......................... 66.39 65.43 



Hydrogen ...................... 10.69 11.16 



Nitrogen ........................ 2.39 1.73 



Phosphorus .................... 1.07 3.84 



Oxygen ......................... 19.46 17.&i 



100.00 100.00 



Knop was the first to show that the crude fat which is 

 extracted from plants by ether contains an admixture of 

 some substance of which phosphorus is an ingredient. 

 In the oil obtained from the sugar-pea he found 1.25 per 

 cent, of phosphorus, Topler afterwards examined the 



