190 PUTREFACTION, FERMENTATION, AND DECAY 



fermentation a true chemical process. This was overthrown by 

 Pasteur, who proved fermentation to be due to living microscopic 

 organisms, and it came to be generally believed that putrefaction 

 was due to a certain microorganism Bacterium termo. Cohn 

 wrote in 1872 that through his own experiments, as well as through 

 those of other investigators, he was convinced that Bad. termo was 

 the ferment of putrefaction in the same w r ay that yeast is the alcoholic 

 ferment. He considered that other bacteria may play a secondary 

 role, but that Bad. termo is the primary cause of putrefaction. How- 

 ever, bacteriologists soon came to realize that Bad. termo was only 

 a general name given to the many species of rod-shaped organisms 

 occurring in decaying substances. In 1884 and 1885 Hauser 

 isolated three distinct species of bacteria capable of causing putre- 

 faction Proteus vulgaris (B. proteus, B. vulgaris, B. zopfi), Proteus 

 mirabilis, and Proteus zenkeri. The first two are capable of liquefy- 

 ing gelatin, while the last is not. Many different bacteria are 

 encountered in a spontaneously putrefying substance. Among the 

 most active which have been studied are, according to Effront: 

 the family of Proteus, B. putrificus coli (Bienstock), B. perfringens 

 (Veillon and Zuber), Micrococcus flavus liquefaciens (Fluegge), 

 B. gracilis putidus (Tissier and Martelly), B. bifermentans sporo- 

 genes B. diplococcus griseus non-li^uefaciens (Tissier and Martelly), 

 B. coli communis (Escherich), Streptococcus pyogenes (Doleris and 

 Pasteur), and Staphylococcus pyogenes albus (Rosenbach). These 

 bacteria are very widely distributed, B. proteus being especially apt 

 to occur in substances undergoing decomposition. Its presence is 

 constant in rotten meat, is very frequent in manure, and is met with 

 in large numbers even in normal dejecta. The putrefying bacteria 

 are usually anaerobic, but there are often very active aerobes. 



H. Martelly made a careful study of the bacterial flora of putrefy- 

 ing material and found that it changed from period to period. He 

 found at first Micrococcus flavus, Staphylococcus albus, B. coli, and 

 Diplococcus griseus. Then at the end of three or four days B. 

 perfringens, B. sporogenes appeared, at the end of eight to ten days 

 he detected the presence of B. putidus, B. putrificus, and Proteus 

 zenkeri, and after three months there remained only B. putrificus, 

 B. putidus, and Diplococcus griseus. 



Products of Putrefaction and Decay. Due to the trypsin and 

 erepsin secreted by the bacteria the proteins are broken into albu- 

 moses, peptones, proteoses, and amino-acids, and even in very 

 advanced putrefaction nitrogenous substances are always found 

 which give the protein reactions. The amidases secreted by 

 bacteria give rise to volatile acids, amins, phenol and indol deriva- 

 tives. Effront summarizes the products formed as follows: (1) 

 Ammonia and amins ethylamin, propylamin, and trimethylamin; 

 (2) volatile acids, comprising all the members of the fatty series up 

 to caproic acid; (3) aromatic a.ciqls and oxyacids, like phenylpro- 



