ORIGIN OF BACTERIA. 25 



Oxidation and reduction are carried on by some bacteria. Am- 

 monia, hydrogen sulphide, and trimethylamin are a few of the 

 chemical products produced by bacteria. Nitrites in the soil 

 are reduced to ammonia. 



Nitrification. Albuminoids changed into indol, skatol, leticin, 

 etc. ; then these into ammonia. Ammonia into nitrites. Ni- 

 trites into nitrates. 



Ptomaines. Brieger found a number of complex alkaloids, 

 closely resembling those found in ordinary plants, and which 

 he named ptomaines, from Trru/na (corpse), because obtained 

 from putrefying objects. 



Proteins. The components of the bacterial cell may cause 

 inflammation and fever. 



Putrefaction. When fermentation is accompanied by devel- 

 opment of offensive gases a decomposition occurs, which is 

 called putrefaction, and this, in organic substances, is due 

 entirely to bacteria. 



Producers of Disease. Various pathological processes are 

 caused by bacteria, the name given to such diseases being in- 

 fectious diseases, and the germs themselves called disease-pro- 

 ducing or pathogenic bacteria. Those which do not form any 

 pathological process are called non-pathogenic bacteria. 



Ferments are diastatic, changing starch into sugar ; proteolytic, 

 transforming albumins into more soluble substances; gelatin 

 liquefaction is an example. 



Inverting, changing a sugar from one that does not undergo 

 fermentation into one that does. 



Coagulating, fat-splitting, hydrolytic ferments are some of the 

 other varieties. 



Toxins and Toxalbumins are various albuminoids produced 

 in the animal organism and in culture-media which are very 

 poisonous, and are considered the prime cause of disease. 



Pigmentation. Some bacteria are endowed with the property 

 of forming pigments either in themselves, or producing a chro- 

 mogenic body which, when set free, gives rise to the pigment. 

 In some cases the pigments have been isolated and many of the 

 properties of the aniline dyes discovered in them. 



Phosphorescence. Many bacteria have the power to form 



