142 PRODUCTS OF VITAL ACTIVITY. 



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

 are characterized by their offensive odors. According to Fliigge, 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, hydrosulphuric acid (H,S), phosphoretted 

 hydrogen (PH 3 ), 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- 

 organisms present. One or the other of the bacteria concerned will 

 take the precedence when circumstances favor its growth. Thus the 

 aerobic bacteria cannot grow unless the putrefying material is freely 

 exposed to atmospheric oxygen ; the anaerobic species require its 

 exclusion. Some saprophytic bacteria grow at a comparatively low 

 temperature, others take the precedence when the temperature is 

 high ; some, no doubt, thrive only in presence of products evolved 

 by other species, and are consequently associated with and depend- 

 ent upon these species ; some are restrained in their growth sooner 

 than others by the products evolved as a result of their own vital 

 activity or that of associated organisms ; some grow in the presence 

 of acids and give rise to an acid fermentation which wholly prevents 

 the development of other species. 



At the outset putrefaction is often attended with the presence 

 of several species of micrococci and certain large bacilli, which are 

 displaced later by short motile bacteria belonging to a group which 

 includes several bacilli formerly described under the common name 

 of Bacterium termo. 



The malodorous volatile products of putrefaction are to a consid- 

 erable extent produced by anaerobic species. For this reason these 

 odors are more pronounced when masses of albuminous material 

 undergo putrefaction in situations where the oxygen of the air has 

 not free access, or where it is displaced by carbon dioxide. The 

 body of a dead animal, although freely exposed to the air, furnishes 

 in its interior a suitable nidus for these anaerobic gas-forming spe- 

 cies, and they may give rise to products of one kind, while aerobic 

 species upon the surface of the mass induce different forms of putre- 

 factive fermentation. In the bodies of living animals these anaero- 



