CHAP. X.] THE NERVOUS TISSUES. 429 



elusions. Pure protagon is remarkably rebellious to the action of even 

 boiling alcohol, though that action be continued for hours: and the most 

 persistent attempts to separate lecithin from it have failed. At the 

 same time there can be no doubt that protagon when treated with 

 certain reagents which decompose it, especially when digested with 

 alkalies, yields, amongst other bodies, certain of the most characteristic 

 of the products of decomposition of lecithin. But to conclude from 

 the presence of these, the presence of lecithin, is obviously unphiloso- 

 phical. 



There can be no doubt that protagon is accompanied in the brain 

 by large quantities of a body or bodies which may provisionally be 

 conveniently classed under the term of cerebrin, and likewise by 

 smaller quantities of other phosphorized bodies, containing a per- 

 centage of phosphorus very close to that found in lecithin, yielding 

 the same products of decomposition, and the separation of which 

 presents extraordinary difficulties. Yet, the Author is convinced that 

 unquestionably the only well characterized phosphorized proximate 

 principle, which can with our present methods be separated with 

 certainty and whose existence will be confirmed by future researches, 

 is Protagon. 



1. Action of Alkalies. Liebreich discovered that 



re^earchlfon wlien P rota g on is boi ! ed for 24 hours with . a satu ~ 

 tfce products rated solution of barium hydrate, the solution con- 

 ofdecompo- tains the barium salt of glycerin-phosphoric acid, 

 sition of pro- (C 3 H 5 ) (OH) 2 . . PO (OH) 2 ; a base called N eurine, which 

 was afterwards shewn to be identical with a base pre- 

 viously obtained by Strecker from ox bile and termed by him Choline 

 (C S H 15 N0 2 ) ; and barium salts of several fatty acids, especially of 

 stearic acid. 



There can be no doubt that there is formed, in addition, a certain 

 quantity of a cerebrin-like body or a mixture of such bodies, i.e. a 

 substance is obtained which is not soluble in ether, which dissolves 

 in boiling alcohol and is deposited from it in a nodular form on 

 cooling : which contains nitrogen but no phosphorus. The experiments 

 of the Author have shewn him that the quantity of this body which 

 is formed is very much smaller than would be the case on the 

 hypothesis that protagon is a mixture or even a conjugated compound 

 of lecithin and cerebrin. 



2. Action of acids. When protagon is boiled with hydrochloric 

 acid in the absence of light, a yellowish liquid is obtained, which 

 deposits flocculi of a body free from phosphorus ; and which becomes 

 coloured when exposed to light. In this process there is set free a 

 laevogyrous, non-fermentable sugar. 



The chief products of decomposition of protagon will be de- 

 scribed at length under the head of lecithin and cerebrin; under the 

 latter the cerebrin body which accompanies protagon will be dis- 

 cussed. 



