180 MICKU-OKGANISLiS AND DISEASE. [CHAP. 



substances, present only during life, and a result of the life of 

 the tissue, the organisms in a particular case cannot thrive and 

 produce the disease. And further, that for each particular 

 species of organism there is a particular chemical substance 

 required to exert this inhibitory power, for, as we have seen, 

 while the anthrax -bacillus is not capable of thriving in the pig, 

 it does well in the guinea-pig, while the bacillus of swine - 

 plague thrives well in the pig, it does not in the guinea-pig. 

 The incapability of non -pathogenic organisms to thrive in 

 healthy living tissues would on this theory be explained 

 by the assumption that these chemical substances present in 

 ,every healthy living tissue are inimical to all putrefactive 

 organisms. 



What we have said hitherto refers only to the healthy living 

 tissues. It is quite possible to imagine that, owing to the 

 presence of a particular chemical substance in the healthy 

 living tissue, a pathogenic organism is not able to thrive in a 

 particular animal ; but under certain abnormal conditions, 

 -when for instance owing to a diseased or altered state of the 

 tissue that substance is absent, the organism might be enabled 

 to exist and multiply and to produce the disease. Supposing 

 it to be true that a person so long as he is healthy and well is 

 able to successfully withstand the growth of a particular 

 pathogenic organism, he is then unsusceptible to the disease ; 

 but we can understand that if the alimentary canal or the 

 lungs be diseased, then the organism passing into the bowels 

 by ingestion or into the lungs by inspiration would find there 

 a tissue in which the necessary inhibitory substance, present in 

 the healthy state, might be absent, and the organism would be 

 capable of thriving and of producing the disease. 



The ne:xt point to consider is the relation of the specific 

 micro-organism to the essence of the disease, or in other words 

 the question whether the organism itself is the virus or whether 

 this latter is the product of the former, something in the same 

 way as the septic ferment is the product of the putrefactive 

 organisms ? 



That the virus in the infectious diseases is intimately con- 

 nected with the organisms is proved by the fact, that the virus 

 introduced into the body multiplies ad infinitum / for instance, 

 in anthrax or tuberculosis after the introduction of an infini- 

 tesimal dose, we find the disease (maligant anthrax or general 

 tuberculosis respectively) sets in in its virulent form ; in the 

 first case every drop of blood teems with the bacillus anthracis ; 

 in the second (tuberculosis) every tuberculous caseous particle 



