250 PHYSIOLOGICAL CHEMISTRY. 



over which there has been much discussion. Upon decomposition 

 it is said by some investigators to yield cerebrin and the decomposi- 

 tion products of lecithin. It has recently been shown by Posner 

 and Gies as well as by Rosenheirn and Tebb that protagon is a 

 mixture and has no existence as a chemical individual. 



Kephalin is the third member of the group of phosphorized fats. 

 It is precipitated from its acetone-ether extract by alcohol. It 

 contains about 4 per cent of phosphorus and has been given the 

 formula C 42 H 79 NPO 13 . Kephalin may be a stage in lecithin meta- 

 bolism. 



Cerebrin, a substance containing nitrogen but no phosphorus, 

 is an important constituent of the white matter of nervous tissue. 

 It has also been found in the spleen, pus and in egg yolk. It may 

 be extracted from the tissue by boiling alcohol and is insoluble in 

 cold alcohol, cold and hot ether and in water and dilute alkalis. 

 Cerebrin is a mixture containing phrenosin (pseudo-cerebrin or 

 cerebron), a body yielding the carbohydrate galactose on decom- 

 position. 



Cholesterol, one of the primary cell constituents, is present in 

 fairly large amount in nervous tissue. It is a mon-atomic alcohol 

 with the formula C 27 H 45 OH. It was formerly called a "non-sap- 

 onifiable fat " but since it is not changed in any way by boiling al- 

 kalis it is not a fat. It is soluble in ether, chloroform, benzene and 

 hot alcohol. It crystallizes in the form of thin, colorless, transparent 

 plates (Fig. 42, p. 159). Cholesterol occurs abundantly in one form 

 of biliary calculus. It has also been found in feces, wool fat, egg 

 yolk, and milk, frequently in the form of its esters of higher fatty 

 acids. 



Paranucleoprotagon is a phosphorized substance originally iso- 

 lated from brain tissue by Ulpiani and Lelli and recently reinvesti- 

 gated by Steel and Gies. It is said to possess lecithoprotein char- 

 acteristics. 



Nervous tissue yields about i per cent of ash which is made up 

 in great part of alkaline phosphates and chlorides. 



EXPERIMENTS ON THE LIPOIDS OF NERVOUS TissuE. 1 



i. Preparation of Lecithin. Treat the macerated brain of a 

 sheep with ether and allow it to stand in the cold for 4872 



1 Preparation of So-called Protagon. Macerate the brain of a sheep, treat 

 with 85 per cent alcohol and warm on a water-bath at 45 C. for two hours. 

 Filter hot into a bottle or strong flask and cool to o C. for one-half hour by 



