548 MICRO-ORGANISMS AND DISEASE [chap. 



pathogenic microbes is a limited one, and the number of 

 such microbes known is less extensive than the number 

 of known infectious diseases, since of some of them the 

 specific microbe has not been discovered yet, e.g., hydro- 

 phobia, syphilis, measles, whooping cough, &c., &c. ; if, 

 however, under a pathogenic microbe is understood one 

 that is capable of living, under one condition or another, 

 parasitic in the animal body and causing therein disease or 

 a diseased condition, then their number is practically un- 

 limited and no line of demarcation can be drawn between 

 specific or parasitic and non-specific or saprophytic microbes. 

 It is well established that microbes like bacillus prodigiosus, 

 bacillus subtilis, proteus vulgaris, bacillus coli, and others, 

 i.e. microbes living generally as saprophytes, when injected 

 subcutaneously into the guinea-pig in small quantities, such 

 as in the case of specific microbes capable of producing 

 a specific disease, cause no disturbance, because they are 

 not capable of living and multiplying in the subcutaneous 

 tissue. I have shown that if these same saprophytes be 

 injected in considerable quantities into the peritoneal cavity 

 of a guinea-pig {see a former chapter) they are capable of 

 living herein, of multiplying and causing acute peritonitis and 

 death ; after death the peritoneal exudation is found teeming 

 with the living microbe, and they can be demonstrated in a 

 living state in the blood and in the cavity of the inflamed 

 intestine. Under this aspect of pathogenicity many a 

 species occurring in nature ordinarily as saprophytes and 

 connected with no infectious disease does cause acute fatal 

 peritonitis and is capable of multiplying within the peritoneal 

 fluid, whereas I have likewise shown that a notoriously 

 specific microbe, like the diphtheria bacillus (from a gelatine 

 culture), while virulent in the subcutaneous tissue of the 

 guinea-pig, when injected in large doses into the peritoneum 



