138 CEREBRIK 



further confirmation has been afforded still more recently 1 . Protagon 

 appears to separate out from warm alcohol on gradual cooling in the 

 form of very small needles, often arranged in groups : it is slightly 

 soluble in cold, more soluble in hot alcohol, and in ether. It is insoluble 

 in water, but swells up and forms a gelatinous mass. It melts at 200 

 and forms a brown sirupy fluid. 



Preparation. Finely divided brain substance, freed from blood- 

 vessels and connective tissue, is digested at 45 C. with alcohol 

 (85 p. c.) as long as the alcohol extracts anything from it. The united 

 extracts are filtered while hot and the protagon separates out from the 

 filtrate on cooling to 0. It is next thoroughly extracted with ether to 

 get rid of all cholesterin and other bodies soluble in ether, and finally 

 purified by repeated crystallisation from warm alcohol. 



By treatment with boiling solution of caustic baryta protagon is 

 decomposed, yielding the several products which result from the de- 

 composition of lecithin under the same conditions, together with an 

 additional product known as cerebrin. 



Cerebrin 2 . 17 H 33 



Is found in nerves, in pus corpuscles, and largely in the brain. 

 In former times many names were given to the substance when in an 

 impure state, ex.gr. cerebric acid, cerebrote, &c. It was first prepared 

 by W. Miiller 3 who constructed the above formula from his analysis ; 

 the mean of these is C, 68-45. H, 11-2. ' N, 4-5. O, 15-85. Great 

 doubts are however thrown upon the purity of Miiller's preparations by 

 the researches of later observers. From a later investigation it appears 

 to contain less nitrogen than is stated above, the carbon and hydrogen 

 being the same (C, 68'74. H, 10-91. N, 1-44. O, 18-91) 4 . 



It is prepared from brain substance by extraction with alcohol and 

 purified by recrystallisation from this solvent ; its complete separation 

 however from lecithin &c. is difficult, but is attained by treating the 

 mixture with boiling barium hydrate : this while it has no effect on 

 the cerebrin decomposes the lecithin. 



It is a light, colourless, exceedingly hygroscopic powder, which 

 swells up strongly in water, slowly in the cold, rapidly on heating. 

 When heated to 80 it turns brown, and at a somewhat higher tem- 

 perature melts, bubbles up and finally burns away. It is insoluble in 

 cold alcohol, or ether ; warm alcohol dissolves it readily. Heated with 



1 Baumstark, Zt.f. physiol. Chem. Bd. ix. (1885), S. 145. 



2 See Gamgee, Physiol. Chem. Vol. i. p. 439. 



3 Ann. d. Chem. u. Pharm. Bd. cv. (1858), S. 361. 



4 Geoghegan, Zt. f. physiol. Chem. Bd. in. (1879), S. 332. See also Parcus, Jn. 

 f. Drakt. Chem. (N.F.\ Bd. xxiv. (18811. S. 310. 



