BIOLOGIC AND CHEMIC ACTIVITIES 2p 



changes are destructive to the bacteria themselves, as when 

 lactic and butyric acids are formed in the media. 



Oxidation and reduction are carried on by some bacteria. 

 Ammonia, hydrogen sulphid, and trimethylamin are a few of 

 the chemic products produced by bacteria. Nitrites in the 

 soil are reduced to ammonia. 



Nitrification. Albuminoids changed into indol, skatol, 

 leucin, etc. ; then these into ammonia, ammonia into nitrites, 

 nitrites into nitrates. 



Ptomains. Brieger found a number of complex alkaloids 

 closely resembling those found in ordinary plants, and which 

 he named ptomains, from Trrw/za, corpse, because obtained 

 from putrefying objects. These were at one time held to be 

 the chief causes of bacterial disease, but are no longer con- 

 sidered of much importance. 



Chemic Products. Secretions, as, for instance, enzymes, 

 toxins. Excretions, pigments, indol, cell proteins, bacterins. 



Proteins. The protein contents of the bacterial cell may 

 cause inflammation and fever. 



Producers of Disease. Various pathologic processes 

 are caused by bacteria, the name given to such diseases being 

 infectious diseases, and the germs themselves called disease- 

 producing or pathogenic bacteria. Those which do 'not form 

 any pathologic process are called non-pathogenic bacteria. 



Fermentation. This is an important property of bac- 

 terial activity. 



Enzymes. An enzyme or ferment is a substance capable 

 of inaugurating a chemic reaction without entering into the 

 reaction, and is a product of living cells. 



Bacterial enzymes are closely related to the ferments of 

 special cells of higher animals and plants, like ptyalin and 

 diastase. 



Ferments may be diastatic, changing starch into sugar, or 

 proteolytic, transforming albumins into more soluble sub- 

 stances, of which gelatin liquefaction is an example. Invert- 

 ing, changing a sugar from one that does not undergo fermen- 

 tation into one that does. 



