THE EFFECTS OF BACTERIA. 115 



3. THERMIC EFFECTS. 



The development of heat during the metabolism 

 of bacteria is not noticeable in our ordinary cultures 

 on account of its slight amount. Even luxuriantly 

 growing, fermenting fluid cultures do not reveal to the 

 hand any noticeable production of heat. 



But there is no doubt, on the other hand, that the 

 heat given out by moist decomposing organic matters, 

 such as beds of tobacco, hay, manure, etc., depends, 

 at least in part, on bacterial activity. In view of the 

 high temperature produced, it is very probable, ac- 

 cording to Lydia Kabinowitsch, that the thermophilic 

 bacteria take part in the process. Careful investiga- 

 tions concerning the producers of these high temper- 

 atures are still wanting (vide Rabinowitsch : Z. H., 

 XX., 163). 



4. CHEMICAL EFFECTS. 



The chemical actions of bacteria, which are accom- 

 panied in part by the production of light, and always 

 by the production of heat, are known only in their 

 main outlines, despite the extremely numerous and 

 successful investigations of the last twenty-five years. 

 In many cases we know only the final products, and 

 have no accurate information concerning the mechan- 

 ism of their development, the intermediate pro- 

 ducts, and the substances which appear in small 

 quantities. 



We may distinguish the following three principal 

 varieties of chemical effects : 



1. The bacteria store up their cell substance. 



