Physiology of Microbes. 33 



phoretted hydrogen ; ammonia, carbonic, formic, acetic, 

 butyric, and lactic acids, etc.; amines, trimethylamin, 

 propylamin, etc.; indol, scatol, tyrosin, ptomaines, etc. 

 The term saprogenic is apphed more particularly to 

 those microbes which excite putrefaction with disen- 

 gagement of a peculiarly fetid odor. 



2. EOLE OF BACTERIA EST THE NORMAL ORGANISM. 



In a general way the microbes which live within or 

 upon healthy individuals behave as commensals with- 

 out giving rise to the slightest disturbance in their 

 host. 



Nevertheless, as there are almost always, among the 

 germs distributed on the normal organism, a certain 

 number which are pathogenic, we can understand that 

 their presence constitutes a permanent source of dan- 

 ger for the economy. This danger exists upon all 

 contaminated surfaces the germs being able to invade 

 the organism when an accidental abrasion occurs. 



Digestive action. — The germs lodged within the di- 

 gestive canal have a more interesting role, for they seem 

 to place themselves at the service of their host in 

 order to assist in the preparation of his foods, in his 

 digestion. Bienstock has isolated from faeces a bacil- 

 lus which converts albumen into peptones; the bacil- 

 lus amylobacter, which is found in the stomach of 

 ruminants, secretes a soluble ferment which acts upon 

 starch and cellulose. 



M. Abelous has collected from the stomach sixteen 

 species of microbes whose resistance to the action of 

 the gastric juice he has verified. The study of their 

 digestive action gave very interesting results. Albu- 

 men, casein, fibrin and gluten were rapidly and com- 



