CHEMICAL BASIS OF TU K ANIMAL BODY. 1,;7 



It was first described as a product of the decomposition of pro- 

 tagon by caustic baryta, 1 and until recently the names cholin and 

 neurin were applied interchangeably to the basic product of the 

 action of baryta on lecithin or protagoii first described under the 

 name choliu. 2 The researches of Brieger have however shown 

 that neurin differs distinctly both in composition and properties 

 from tlu- older cholin, and have further identified it as one of the 

 most commonly occurring and actively toxic of tin- alkaloidal basic 

 products of the putrefactive decomposition of animal tissues known 

 under the name of the ptomaines 8 (see below). Like cholin it 

 is in the pure state a sirupy fluid, with strongly alkaline reaction 

 and is extremely soluble in water. It forms with hydrochloric 

 acid and platinum chloride characteristic double salts which crys- 

 tallise readily. The double salt which neurin forms with gold 

 chloride crystallises in yellow needles ; it is but slightly soluble 

 in cold water, though soluble in hot water 



Frotagon. C 16 oH 808 N 6 PO 85 (?). 



A crystalline substance, containing nitrogen and phosphorus, 

 obtained by Liebreich* from the brain and regarded by him as its 

 principal constituent. The researches of Hoppe-Seyler and I)iak- 

 onow tended to show that protagon was merely a mixture of leci- 

 thin and cerebriu. A repetition of Liebreich's experiments has 

 however led Gamgee and Blankenhorn 6 to confirm the truth of 

 his results, and further confirmation has been afforded still mon- 

 recently. 6 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 ex- 

 tracted with ether to get rid of all cholesterin and other bodies 

 sol ul tie in ether, and finally purified by repeated crystallisation 

 from warm ale,, hoi. 



By treatment with boiling solution of caustic baryta protagon is 



J Lichrei.-h, II. r. ,L ,1. ch.m. (fftrll. .Tahrtf. II. (lSf,'.n. S. 1-J 



liMinrti.m i" made between rholin and neurin in the latest edition (1883) 



of H|p[x--Sr\ It-r's I/itnilliiK/, il. /i/ii/*.-/Hlt/i. rh. ill. Allill. 



8 Brieffe^ li>r. </. <l. chem. Getell. Jahrg. xvi. (1883), Sn. 1190, 1406; xvn. Sn. 

 516, 11.-17. 



4 .\nn. //. r/,,m. . />///;. M. . \\xiv. (If 



6 Jl. of Phi/si,,!. Vol. n. (IHT'.i). j, ll.! AN., in /.i. f. f>hi/tiol. Chem. B<1. in. 

 (1879), S'. 260.' (iivf-s hi>t<.rv :in<l literatim- "f Tin- Miliji-rt to date. 



6 Baumstark. ZLf.pkytUL Chan. I5d. i\. (1885), S i 



