53° MICRO-ORGANISMS AND DISEASE [chap. 



serving the growth of some bacteria : bacilhis of Friedlander, 

 typhoid bacillus, pink torula, staphylococcus pyogenes 

 aureus ; while others are capable of growing in such gelatine, 

 though slightly retarded : cholera spirillum ; and still others 

 grew normally : Finkler's spirilla, bacillus anthracis. To- 

 wards the former, therefore, the bacillus putidus has a 

 decided antagonistic action, while with the latter it is sym- 

 biotic. But this antagonism, when existing, is not neces- 

 sarily mutual, for while the typhoid bacillus renders the 

 gelatine also unfit for the growth of the bacillus fluorescens 

 putidus — these two species being mutually antagonistic — it 

 is not so with the bacillus of Friedlander or the staphylo- 

 coccus aureus. Diphtheria bacilli grow well in broth pre- 

 viously exhausted by proteus vulgaris. 



To the same category belong the observations of Soyka 

 and Bandler, who studied the manner in which certain bac- 

 teria are capable of growing in media previously exhausted 

 by other bacteria (Fortschritte der Med. 1888, p. 76). 



Cash has made similar observations with bacillus anthracis 

 and certain micrococci when growing simultaneously. He 

 found that the growth of the bacillus anthracis does go on 

 to a certain extent, but that the virulence of it is impaired 

 by the growth of the micrococci. This subject deserves a 

 more exhaustive study than it has hitherto received ; it is 

 mainly of importance to ascertain whether and to what 

 extent an inimical influence is exerted by one species on the 

 other capable of growing simultaneously in the same me- 

 dium. There is good reason for supposing that hereby, in 

 some cases at any rate, one species is capable of attenuating 

 the virulence of another. Thus in the cultures which Pasteur 

 used as attenuated cultures for producing protective inocu- 

 lation in fowl cholera it was not, as Pasteur believed, the 

 prolonged exposure to air that produced the attenuation of 



