fi UNIVERSITY 1 

 VITAL PHE^^mCfpTERIA 91 



occur side by side in one plate culture, as, for example, the staphylo- 

 coccus pyogenes. 



Alkaline Products and the Fermentation of Urea. Aerobic bacteria 

 always produce alkaline products from albuminous substances in cul- 

 ture media free from sugar. Many species of bacteria produce acids 

 in the presence of sugars, which explains the fact that neutral or slightly 

 alkaline broth often becomes acid at first from the fermentation of the 

 sugar contained in the meat used for making the media. When the 

 sugar is used up the reaction often becomes alkaline, as the production 

 of alkalies continues. The substances producing the alkalinity in cul- 

 tures are chiefly ammonia, amine, and the ammonium bases. 



The conversion of urea into carbonate of ammonia affords an 

 example of the production of alkaline substances by bacteria: 



CO(NH,) 2 + 2H 2 00 S (XH 4 ), 



Urea. 2 Water. Ammonium carbonate. 



The power of decomposing urea is not widespread among bacteria. 

 Of sixty species investigated by Lehman, three only developed the odor 

 of ammonia from sterilized human urine. 



Ptomains. Nencki, and then later Brieger, Vaughan, and others, suc- 

 ceeded in preparing organic bases of a definite chemical composition out 

 of putrefying fluids meat, fish, old cheese, and milk as well as from 

 pure bacterial cultures. Some of these were found to exert a poisonous 

 effect, while others were harmless. The poisons may be present in 

 the decomposing cadaver (hence the name ptomain, from --wfjia., 

 putrefaction), and, in consequence, have to be taken into considera- 

 tion in questions of legal medicine. They may be formed also in the 

 living human body, and, if not made harmless by oxidation, may come 

 to act therein as self-poisons or leucomains. They are now known 

 not to be the substances which excite the specific poisonous effects of 

 bacteria. The latter are easily destroyed by heat, and have entirely 

 different characteristics. 



Many ptomains are known already and the elementary composition 

 of each made out, and among them are some whose exact chemical con- 

 stitution is established. Especially interesting is the substance cada- 

 verin, which was separated by Brieger from portions of decomposing 

 dead bodies and from cholera cultures, by reason of the fact that 

 Ladenburg prepared it synthetically and showed it to be pentame- 

 thylenediamin [(NH 2 ) 2 (CH 2 ) 5 ]. The cholin group is particularly inter- 

 esting. Cholin itself (C 5 H, 5 NO 2 ) arises from the hydrolytic breaking-up 

 of lecithin, the fat-like substance found in the brain and other nervous 

 tissue. By the oxidation of cholin there can be produced the highly 

 toxic muscarin, found by Schmiedeberg in a poisonous toadstool and 

 by Brieger in certain decomposing substances: 



C 5 H 15 N0 2 + O = C 5 H 15 N0 3 

 Cholin. Muscarin. 



The ptomain tyrotoxicon was obtained from cheese, milk, and ice- 

 cream by Vaughan. 



