138 PRODUCTS OF VITAL ACTIVITY. 



A micrococcus producing viscous fermentation in milk has also 

 been described by Schmidt-Miihlheim, and a bacillus by Loffler. 

 Bacillus mesentericns vnlgatus also produces a similar change in 

 milk. 



Mai'fth f/^.s-, CH 4 , is produced by the fermentation of cellulose, 

 through the action of microorganisms the exact characters of which 

 have not yet been determined. According to Tappeiner, there are 

 two different fermentations of cellulose. The first occurs in a neu- 

 tral one-per-cent flesh extract solution to which cotton or paper pulp 

 has been added. The gases given off are CO, and CH 4 and small 

 quantities of H 3 S. The second fermentation occurs when an alkaline 

 solution of flesh extract containing cellulose in suspension is used. 

 The gases formed are CO, and H. In both cases small quantities of 

 aldehyde, isobutyric acid, and acetic acid are produced. 



Hydrosulphuric acid, H 2 S. This gas is produced during the 

 growth of certain bacteria. The conditions governing its develop- 

 ment have been studied by Holschewnikoff, who experimented with 

 two species, one isolated by himself and one by Lindeiiborn, named 

 respectively Bacterium sulfureum and Proteus sulfureus. The first- 

 mentioned bacterium, when inoculated into eggs, produced within 

 three or four days an abundant quantity of H 2 S ; the other did not. 

 Upon raw albumin both species produced but little, and 011 the yolk 

 of egg a considerable amount of this gas. Upon cooked egg the 

 action was the reverse. In peptone-bouillon the evolution of H 2 S 

 was abundant ; in the absence of peptone, very slight. 



Putrefactive fermentation. The putrefactive decomposition 

 of albuminous material of animal and vegetable origin is effected 

 by a great variety of microorganisms and gives rise to the forma- 

 tion of a great variety of products, some of which are volatile and 

 are characterized by their offensive odors. According to Flugge, the 

 first change which occurs consists in the transformation of the albu- 

 mins into peptone, and this may be effected by a large number of 

 different bacteria. Among the products of putrefactive fermenta- 

 tion known to chemists are the following substances : Carbon diox- 

 ide, hydrogen, nitrogen, hydroBulphuric acid (H 2 S), phosphoretted 

 hydrogen (PHJ, methane, formic acid, acetic acid, butyric acid. 

 valerianic acid, palmitic acid, crotonic acid, glycolic acid, oxalic 

 acid, succinic acid, propionic acid, lactic acid, amidostearic acid, 

 leucin, ammonia, ammonium carbonate, ammonium sulphide, tri- 

 methylamine, propylamine, indol, skatol, tyrosin.neuridin, cadaverin. 

 putrescin, cholin, neurin, peptotoxin. and various other volatile 

 acids, ptomaines, etc. 



The special products of putrefaction vary according to the nature 

 of the material, the conditions in which it is placed, and the micro- 



