ANALYSIS OF PI TIIK1 YIXG SUBSTANCES 173 



organisms here described, a large number of others have 

 been found which also occur in water or air and have been 

 described under those heads, e.g. litn-ilhis raim^-ux, 7 >'m /'////. s- 



subtilis, Staphylococcus j>i/<></cn<'x aiircus, and brown mould. 

 Karlinski also found the typhoid Innllns in the ground, 

 but these bacilji soon perish on the surface of the soil, 

 although they can maintain themselves in its deeper strata. 



ANALYSIS OF PUTREFYING SUBSTANCES 



Differences in putrefactive processes. When the condi- 

 tions determining the decomposition of organic substances 

 5ir- investigated, it is possible to recognise the presence of 

 micro-organisms in the products which result. Decompo- 

 sition must be looked on as including two distinct pro- 

 cesses, for if the conditions necessary for the formation of 

 its products be sought for in the mode of life of micro- 

 organisms, it can very readily be ascertained that one 

 variety of the process is caused by those microbes which 

 thrive in the absence of oxygen, that is, is dependent on 

 the vital activity of anaerobes; whereas the remaining 

 variety is essentially a process of oxidation set up by 

 aerobic micro-organisms. 1 In the latter, highly complex 

 combinations are reduced to the very simplest, as happens 

 with the manure used in agriculture ; and this can take place 

 only when oxygen has free access, and in the presence of 

 the proper amount of water. When there is too much 

 water the necessary quantity of oxygen cannot gain ad- 

 mission, and the process reverts to the first-mentioned 

 (anaerobic) form. 



During decomposition the chemical reaction very fre- 

 quently changes, and there is also a formation of 



1 'These processes have distinct names in German, for which there are 

 no English equivalents, the anaerobic variety being known as Faulnis, 

 the aerobic as 



