CHEMICAL BASIS OF THE ANIMAL BODY. 137 



By oxidation with concentrated nitric acid it yields the extremely 

 poisonous alkaloid muscarin CgH^NOg 1 . Cholin is itself possessed 

 of poisonous properties, and arising as it does from the decomposition 

 of lecithin and protagon is now recognised as one of the alkaloidal 

 products or ptomaines (see below) which occur in putrefying animal 

 tissues 2 . 



Neurin. C 5 H 13 NO. [(CH 3 ) 3 E N <QH = CH ], trimethylvinyl-am- 

 monium hydroxide. 



This substance is closely related to cholin both in composition and 

 origin, but is much more powerfully toxic than that body. It was first 

 described as a product of the decomposition of protagon by caustic 

 baryta 3 , and until recently the names cholin and neurin were applied 

 interchangeably to the basic product of the action of baryta on lecithin 

 or protagon first described under the name cholin 4 . The researches of 

 Brieger have however shown that neurin differs distinctly both in com- 

 position and properties from the older cholin, and have further identified 

 it as one of the most commonly occurring and actively toxic of the al- 

 kaloidal basic products of the putrefactive decomposition of animal 

 tissues known under the name of the ptomaines 5 (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 hydro- 

 chloric acid and platinum chloride characteristic double salts which 

 crystallise readily. The double salt which neurin forms with gold 

 chloride crystallizes in yellow needles ; it is but slightly soluble in cold 

 water, though soluble in hot water. 



Protagon. C 160 H^ N 5 PO 35 (]). 



A crystalline substance, containing nitrogen and phosphorus, ob- 

 tained by Liebreich 6 from the brain and regarded by him as its 

 principal constituent. The researches of Hoppe-Seyler and Diakonow 

 tended to show that protagon was merely a mixture of lecithin and 

 cerebrin. A repetition of Liebreich's experiments has however led 

 Gamgee and Blankenhorn 7 to confirm the truth of his results, and 



1 Schmiedeberg u. Harnack, Arch. f. exp. Path. u. Pharm. Bd. vi. (1876), S. 101. 

 Cf. Berlinerblau, Ber. d. d. diem. Gesell. Jahrg. xvn. (1884), S. 1139. But see 

 also Bohm, Arch. f. exp. Path. u. Pharm. Bd. xix. (1885), S. 87. 



2 Brieger, Zt. f. klin. Med. Bd. x. (1885), S. 268. See also Brieger's works 

 referred to below, sub Ptomaines. 



3 Liebreich, Ber. d. d. chem. Gesell. Jahrg. n. (1869), S. 12. 



4 No distinction is made between cholin and neurin in the latest edition (1883) 

 of Hoppe-Seyler's Handbuch d. phys.-path. chem. Anal. 



5 Brieger, Ber. d. d. chem. Gesell. Jahrg. xvi. (1883), Sn. 1190, 1406; xvn. Sn. 

 516, 1137. 



6 Ann. d. Chem. u. Pharm. Bd. cxxxiv. (1865), S. 29. 



7 Jl. of Physiol. Vol. u. (1879), p. 113. Also in Zt. f. physiol. Chem. Bd. in. 

 (1879), S. 260. Gives history and literature of the subject to date. 



