PRODUCTS OF BACTERIAL ACTIVITY. 35 



way. The farmer turns under with the plow a few crops of 

 clover, which decompose and liberate nitrogen. This free 

 nitrogen is acted upon by the nitrifying bacteria, especially 

 the nitromonas, an organism isolated and described by Wino- 

 gradsky. Most of the nitrifying bacteria are non-pathogenic 

 saprophytes. 



Enzymes : Bacteria produce certain substances known as 

 enzymes, which, according to some authorities, play a very 

 important part in the production of immunity. They have a 

 decided bacteriolytic action, and are perhaps responsible for 

 the phenomenon of agglutination. The limited course run 

 by every infectious disease is supposed to be due to the bac- 

 teriolytic action of these enzymes. They are called nucleases. 

 For instance, typhoid nuclease would be referred to as typhase, 

 for short, etc. 



Peptonization of milk : Milk may be said never to be free 

 from bacteria, and it is nearly always impossible to detect 

 their presence by simple inspection, as the appearance of the 

 milk may not be changed. Some bacteria digest the casein 

 without altering the appearance of the milk. Others produce 

 coagulation ; others, gelatinization. The milk may be trans- 

 formed into a watery fluid. Ptomaines may be formed, which 

 give rise to poisoning, e. g., that due to tyrotoxicon. 



