SYMBIOSIS, 29 



vasion of the subcutaneous and connective tissues 

 caused by the streptococcus can often be distin- 

 guished clinically from the slower, more circum- 

 scribed process caused by the staphylococcus. The 

 conditions induced by the Bacillus aerogenes cap- 

 sulatus, the bacillus of malignant edema, are, in 

 turn, different from those of the streptococcus and 

 staphylococcus. The pneumococcus commonly 

 causes the consolidation of rather extensive areas 

 of the lung, whereas the streptococcus and the 

 bacillus of Friedlander are more often found in 

 the lobular consolidations. The membranous in- 

 flammation of diphtheria may in favorable cases 

 be distinguished from that of the pyogenic organ- 

 isms without bacteriologic aids ; in this possibility, 

 however, there lies no justification for neglect of 

 the bacteriologic examination. 



In nature pathogenic micro-organisms are often symbiosis. 

 found side by side with saprophytes or with other 

 pathogenic bacteria, and at times their viability is 

 profoundly influenced by their associates. Thus 

 it is found that the bacilli of plague and typhoid 

 and the vibrio of cholera do not live long in the 

 presence of many saprophytic organisms. In some 

 instances this may be due to the exhaustion of the 

 nutrient material by the more rapidly growing 

 saprophytes, whereas in others it may be referable 

 to an antagonistic action of one organism on the 

 other. On the other hand, the relationship may be 

 a favorable one. The existence of anaerobic or- 

 ganisms in nature, such as the tetanus bacillus or 

 the bacillus of malignant edema, may be favored 

 by a luxuriant growth of aerobic organisms in 

 their immediate vicinitv. 



