CHAPTER XIX. 



VITAL PHENOMENA OF PATHOGENIC ORGANISMS. 



As has been stated in the preceding chapter, the specific 

 micro-organisms have the great differential character that they 

 are capable of existing and propagating themselves in healthy 

 living tissues. In those species in which the complete series 

 of proofs has been furnished to establish the fact that the 

 micro-organisms are intimately associated with the cause of 

 the malady (e.g. malignant anthrax, tuberculosis, swine-plague 

 erysipelas), in which it has been shown beyond doubt : (a) that 

 "an animal suffering from the malady contains in definite dis- 

 tribution the particular micro-organism, (b) that the micro- 

 organisms, cleared by successive artificial cultures from any 

 adhering hypothetical chemical virus, when introduced into a 

 suitable animal produce the malady, (c) that every such 

 affected animal contains the micro-organism, in the same dis- 

 tribution and relation to the diseased organs as the original 

 animal dead after disease in those instances, I say, the only 

 way of understanding the effect of the micro-organisms is to 

 assume, what is actually the case, that the micro-organisms in- 

 troduced into the living tissue go on multiplying, and directly 

 or indirectly, i.e. themselves or by their products, as will 

 be stated below, produce certain definite disorders in the 

 different parts. In the most favourable cases (anthrax, tuber- 

 culosis), a single organism introduced into a suitable locality 

 in the animal body will be capable of starting readily a new 

 brood. But in other cases it is necessary that an appreciable 

 number of the organisms be introduced in order to start a 

 brood. This was the case in some of the septicaemic processes 

 in rodents studied by Koch. 1 The period between the time 

 of introduction of the organism into the body (blood, skin, 



1 In/ectionskrankheiten, loc. cit. 



