18 



bacteria, yeasts, moulds, etc. ; unorganized or soluble fer- 

 ments (enzymes) produced by bacteria. 



Alcoholic, acetic, butyric acid, etc., fermentations. 



Ferment changes in the mouth dental caries. 



Abnormal fermentation in the stomach in the intes- 

 tines, Summer diarrhoea of infants. 



Ammoniacal fermentation of urine Hydrothionuria. 



Putrefaction is putrid fermentation Proteids acted 

 upon whereas in true fermentations, starches, sugars, and 

 cellulose are acted upon. 



Poisonous foods. 



Liquefaction of albumin, gelatin, etc., by bacteria due 

 to soluble peptonizing ferments. 



Liquefying and non-liquefying bacteria. 



Inversion of starch by bacteria coagulation of milk. 



Nitrification in the soil. 



Production of pigment, as a rule, is a secondary process, 

 taking place outside of the cell. The oxygen of the air 

 acts on a colorless or leuco-product. 



Sometimes the pigment may be formed directly by 

 the cell primary product. 



Phosphorescence the result of intracellular activities. 



In fermentation and putrefaction more or less com- 

 plex, dead animal and vegetable substances are acted 

 upon by microorganisms; transformed into relatively simp- 

 ler compounds, and eventually into inorganic forms, as 

 carbonic acid, ammonia, nitrates, nitrites, etc., which are 

 now utilizable by living plants. Thus, lifeless remains 

 become indispensable to new life, and bacteria, in their 

 role of scavengers of nature, prove beneficial. 



Certain bacteria may live on living matter in the ani- 

 mal body, and in plants, not only at their expense, but 

 even to their injury, producing changes which may result 

 in disease and death. 



Division of bacteria into pathogenic and non-patho- 

 genic, toxicogenic and non-toxicogenic. 



