-^-^6 CLASSICS OF MODERN SCIENCE 

 the parasitic organisms could be only imperfectly demonstrated by 

 the earlier methods of investigation ; not till an improved method of 

 procedure was introduced was it possible to obtain complete proof that 

 they were parasitic diseases. We are therefore justified in assuming 

 that human traumatic infective diseases will in all probability be 

 proved to be parasitic when investigated by these improved methods. 



On the other hand, it follows from the fact that a definite patho- 

 genic bacterium, e. g., the septicsemic bacillus, cannot be inoculated on 

 every variety of animal (a similar fact is also true with regard to the 

 bacillus anthracis) ; that the septicsemia of mice, rabbits, and man are 

 not under all circumstances produced by the same bacterial form. It 

 is of course possible that one or other of the bacteric forms found 

 in animals also play a part in such diseases in the human subject. 

 That, however, must be especially demonstrated for each case ; a priori 

 one need only expect that bacteria are present ; as regards form, size 

 and conditions of grov/th, they may be similar, but not always the 

 same, even in what appear to be similar diseases in different animals. 



Besides the pathogenic bacteria already found in animals there are 

 no doubt many others. My experiments refer only to those diseases 

 which ended fatally. Even these are in all probability not exhausted 

 in the six forms mentioned. Further experiments on many different 

 species of animals, with the most putrid substances and with every 

 possible modification in the method of application, will doubtless bring 

 to light a num.ber of other infective diseases, which will lead to further 

 conclusions regarding infective diseases and pathogenic bacteria. 



But even in the small series of experiments which I was able to 

 carry out, one fact was so prominent that I must regard it as constant, 

 and, as it helps to remove most of the obstacles to the admission of 

 the existence of a centagium vivum for traumatic infective diseases, 

 I look on it as the most important result of my work. I refer to the 

 differences which exist between pathogenic bacteria and to the con- 

 stancy of their characters. A distinct bacteric form corresponds, as 

 we have seen, to each disease, and this form always remains the same, 

 however often the disease is transmitted from one animal to another. 

 Further, when we succeed in reproducing the same disease de novo 

 by the injection of putrid substances, only the same bacteric form 

 occurs which was before found to be specific for that disease. 



Further, the differences between these bacteria are as great as could. 



