THE ANTAGONISM OF MICRO-ORGANISMS 27 



reich and Sirotinin. When several organisms are asso- 

 ciated in a liquid culture, one species may take precedence, 

 and the other may develop later ; or two or more species 

 may develop at the same time ; or the growth of one species 

 may prevent the growth of another by either {a) exhausting 

 the food material by its rapid growth, or (6) by producing 

 products which retard or prevent the growth of another. 

 The following are some of the results of Freudenreich's 

 investigations. Bacillus pyogenes foetidus prevents the 

 growth of the Spirillum cholerce Asiaticce ; Micrococcus 

 roseus prevents the growth of Micrococcus tetragenus. The 

 following organisms cause a change in broth which prevents 

 the growth of other species : Bacillus pyocyaneus, Bacillus 

 phosphor escens, Bacillus prodigiosus, Spirillum cholerce 

 Asiaticce. The following do not cause any change in 

 broth which unfits it for the growth of other organisms : 

 Bacillus typhosus, Bacillus anthracis, Spirillum tyrogenum. 



