BRAIN AND NERVES. 275 



the brain. The latter is also a physiological constituent of the 

 brain of cartilaginous fishes. 



Of the above-mentioned constituents of the nerve-substance, 

 protagon and its decomposition product, cerebrin, must be specially 

 described. 



Protagon. This body, which was discovered by LIEBREICH, is a 

 nitrogenized and phosphorized substance whose elementary compo- 

 sition, according to GAMGEE and BLANKENHOKN", is C 66.39, H 

 10.69, N 2.39, and P 1.068 per cent, and whose empirical formula is 

 CieoHsogNgPOsg. On boiling with baryta-water, protagon yields the 

 decomposition products of lecithin, namely, fatty acids, glycero- 

 phosphoric acid, and cholin (neurin?), and also cerebrin. On boil- 

 ing with dilute mineral acids, it yields among other products a 

 substance which is laevo-gyrate, reducible, and fermentable. 



Protagon appears, when dry, as a white loose powder. It dis- 

 solves in alcohol of 85 vols. per cent at -f- 45 C., but separates on 

 cooling as a snow-white, flaky precipitate, consisting of balls or 

 groups of fine crystalline needles. It decomposes on heating even 

 below 100 C. It is hardly soluble in cold alcohol or ether, but 

 dissolves on warming. It swells in little water, decomposes partly, 

 and gives myaline forms. With more water it swells to a gelatinous 

 or pasty mass, which with much water yields an opalescent liquid. 

 On fusing with saltpetre and soda, alkali phosphates are obtained. 



Protagon is prepared in the following way : An ox-brain as 

 fresh as possible, with the blood and membranes carefully removed, 

 is ground fine and then extracted for several hours with alcohol of 

 85 vols. per cent at -f- 45 C., filtered at the same temperature, 

 and the residue extracted with warm alcohol until the filtrate does 

 not yield a precipitate at C. The several alcoholic extracts are 

 cooled to C. and the precipitates united and completely extracted 

 with cold ether, which dissolves the cholesterin and lecithin-like 

 bodies. The residue is now strongly pressed between filter-paper 

 and allowed to dry over sulphuric acid or phosphoric anhydride. 

 It is now pulverized, digested with alcohol at -}- 45 C., filtered and 

 slowly cooled to C. The crystals which separate may be purified 

 when necessary by recrystallization. 



The same steps are taken when we wish to detect the presence 

 of protagon. 



Cerebrin. Under this name W. MULLER first described a ni- 

 trogenized substance, free from phosphorus, which he obtained by 



