PUTREFACTION l0 i 



In anaerobic decomposition (putrefaction proper), as in anaerobic fer- 

 mentation, the organic molecules are at first only partly disintegrated, inter- 

 mediate products such as leucine, tyrosine, skatol, and indol being formed. 

 In the absence of air these accumulate, and hence it is that the putrefaction 

 going on in the mud of ponds or ditches, or inside carcases, is accompanied 

 by such evil odours. 



Although the details of the process vary considerably according to the 

 presence or absence of air, the ultimate products of putrefaction are in both 

 cases the same : namely, free nitrogen, free hydrogen, ammonia, methane, 

 carbonic acid, and sulphuretted hydrogen. These also are the end-results of 

 the disintegration of the human body. 



The decomposition of plant tissues, poor in nitrogen but containing 

 large quantities of cellulose, gives rise to humin compounds. There can be 

 no doubt that it is a biochemical process, but the nature and functions of 

 the bacteria concerned in it have not yet been carefully studied (69). 



One of the bacteria which was formerly looked upon as a putrefactive 

 organism par excellence was the Bacterium termo. Cohn described under this 

 name a short, oval, actively motile bacillus, slightly fluorescent in cultures 

 (Fig. 22, a). The species is, however, no longer to be identified, for his 

 description would apply to several common forms. As a matter of fact there 

 are many bacteria going by this name which is properly only applicable as 

 a collective designation for motile bacteria in putrescible substrata. 



In the rich bacterial flora of a putrescent fluid (70) two distinct biological 

 groups must be distinguished, the saprogenic and the saprophile. To desig- 

 nate all bacteria living upon dead organic matter as saprophytes is insuffi- 

 cient. As we have already seen, the saprogenic bacteria are able, by the 

 chemical ferments they secrete, to break up the molecules of proteids. The 

 saprophile organisms cannot do this, but they find a rich supply of nutri- 

 ment in the products thus formed. A large number of metatrophic species 

 are endowed with this fapujty, including some pathogenic forms (cholera and 

 typhoid), and water bacteria like Spirillum undula. The sulphur bacteria 

 too must be called saprophile where they form a coating over the rotting 

 vegetation under water, and the nitrifying organisms also when they oxidize 

 the NH 3 evolved from decaying organic matter. 



The bacteria of the other division, the true saprogenic organisms, 

 include very numerous species, some of which are much better known than 

 others (e.g. Hauser's B. (Proteus vulgaris\ but all of which possess the 

 power of breaking up the complex proteid molecule more or less quickly 

 into simpler groups. With the exception of certain toxines in a few cases, 

 specific products which would serve as classificatory characters are not 

 known. Indol, for example, the production of which was once thought to 

 be characteristic of the cholera germ, is produced by all the cholera-like 

 vibrios, as well as by the B. coli and other forms (Fig. 22, b\ Near to 



