120 BACTERIOLOGY. 



which the peculiar poisonous effect of bacteria 

 is to be ascribed. 



Over fifty such ptomains are known already, 

 and the empirical formula of each made out, 

 and among them are some whose exact chem- 

 ical composition is established. The first of 

 these bodies to be separated was collidin 

 (CsHuN), obtained by Nencki. Trimethyla- 

 min (C 3 H 9 N = (CH 8 ) 8 N), gives an odor like 

 herring brine. Especially interesting is the 

 substance cadaverin, which was separated by 

 Brieger from portions of decomposing dead 

 bodies and from cholera cultures, by reason of 

 the fact that Ladenburg prepared it syntheti- 

 cally and showed it to be pentamethylenedia- 

 min ( (NH 2 ) 2 (CH 2 ) 5 ). The substance methyl- 

 guanidin (C 2 H 7 N 3 = (NH) 24 C(NH 8 )CH 8 ), al- 

 ready known as an oxidation product of creatin, 

 was also isolated from decomposing fluids and 

 from bacterial cultures. The cholin group is 

 particularly interesting. Cholin itself (C 5 H 15 

 NO 2 ), arises from the hydrolytic breaking-up 

 of lecithin, the fatty substance found in brain 

 tissue and other nervous tissue (p. 87). The 

 constitution of cholin is trimethylethoxy-am- 

 monium hydroxide == (CH 2 ) 2 .OH.N(CH 3 ) 3 .OH. 

 From the brain also Liebreich and Bayer sep- 

 arated neurin (C 5 H 13 NO), and Bayer showed 

 this to be trimethylvinyl-ammonium hydroxide 



