34 BACTERIA 



in other spheres, it is also due in part to the inimical in- 

 fluence of the chemical products of the one species upon the 

 life of the bacteria of the other species. Moreover, in one 

 culture medium, as Cast has pointed out, two species will 

 often not grow. When Pasteur found that exposure to air 

 attenuated his cultures, he pointed out that it was not the air 

 per se that hindered his growth, but it was the introduction 

 of other species which competed with the original. The 

 growth of the spirillum of cholera is opposed by Bacillus 

 pyogenes fcetidus. B. anthracis is, in the body, opposed by 

 either B.pyocyaneus or Streptococcus erysipelatis, and yet it is 

 aided in its growth by B. prodigiosus. B. aceti is, under 

 certain circumstances, antagonistic to B. coli commums. 



In several of the most recent of the admirable reports of 

 Sir Richard Thorne issued from the Medical Department of 

 the Local Government Board, we have the record of a series 

 of experiments performed by Dr. Klein into this question of 

 the antagonism of microbes. From this work it is clearly 

 demonstrated that whatever opposition one species affords to 

 another it is able to exercise by means of its poisonous pro- 

 perties. These are of two kinds. There is, as is now widely 

 known, the poisonous product named the toxin, into which 

 we shall have to inquire more in detail at a later stage. 

 There is also in many species, as Dr. Klein has pointed out, 

 a poisonous constituent or constituents included in the body 

 protoplasm of the bacillus, and which he therefore terms the 

 intracellular poison. Now, whilst the former is different in 

 every species, the latter may be a property common to 

 several species. Hence those having a similar intracellular 

 poison are antagonistic to each other, each member of such 

 a group being unable to live in an environment of its own 

 intracellular poison. Further, it has been suggested that 

 there are organisms possessing only one poisonous property, 

 namely, their toxin for example, the bacilli of tetanus and 

 diphtheria whilst there are other species, as above, possess- 



