CLASSIFICATION OF ANAEROBIC BACTERIA 535 



hesitate to attribute to a parasitic or intestinal saprophytic 

 history the anaerobic habit of the rods found commonly in soil. 

 These rods are abundant in unmanured soil, their species are 

 very numerous, their metaboHc processes exceedingly varied. 

 They may grow under aerobic conditions in company with aero- 

 bes and may grow in the presence of oxygen in pasty or solid 

 material or in Uquids containing soap or other substances which 

 alter surface tension. But they retain their anaerobic habit 

 on clear liquid or agar media. The commonest intestinal organ- 

 isms, those of the colon group, have not assimaed a sensitiveness 

 to oxygen. Many of the anaerobes, such as those of putrificus, 

 sporogenes, and bifermentans affinities, are the common agents 

 of putrefaction outside the animal body, while others described 

 by Omeliansky are the common cause of the decay of cellulose. 

 When parasitic outside the intestine, these organisms usually 

 show little of the character of true parasites, but cause fulminat- 

 ing fermentative processes which do not pass from affected 

 individuals to healthy ones. B. abortus, the anaerobic strepto- 

 cocci, fusiform bacilli, and certain types of B. coli, when they 

 invade the tissue may establish chronic infections, characteristic 

 of highly developed parasites, but the anaerobic rods common 

 in soil do not, so far as we know, behave in this manner. They 

 are apparently unable to establish themselves as chronic para- 

 sites in tissues which are well vascularized. Had they a history 

 of intestinal saprophytism, we should probably find highly 

 adapted parasites among them, and should find it easy to educate 

 them to an aerobic habit. 



No one has, of course, suggested that the nitrogen-fixing 

 anaerobes described by Winogradsky developed their anaerobic 

 habit through parasitism. These organisms are active splitters 

 of carbohydrates. They are usually regarded as primitive. It 

 is more probable that the anaerobes of higher metabolism had 

 an evolution of the following type rather than one from the 

 sporulating aerobes or from intestinal saprophytes of large 

 animals which appeared at a comparatively late geological 

 period. 



