364 BACTERIA IN INFECTIOUS DISEASES. 



end of six weeks ; and, very conclusively, that the viru- 

 lence of the culture-fluid is due to the presence in it of 

 the micrococcus, and not to a hypothetical chemical 

 virus found in the first instance in the saliva, and sub- 

 sequently in the blood of a rabbit inoculated with this 

 fluid. For the benefit of those who have not calculated 

 the degree of dilution which such a hypothetical chemi- 

 cal virus would undergo in such a series of culture 

 experiments, I submit the following simple calculation : 

 My culture-tubes contain about a fluidrachm of steril- 

 ized bouillon. The amount of blood introduced into 

 culture No. 1, as seed, was considerably less than a 

 minim, but for convenience I will suppose that one 

 minim is used each time to start a new culture, that 

 is, the original material is diluted 60 times in the first 

 culture, 3600 times in the second, 216,000 times in the 

 third, and in the eighth culture it will be present in the 

 proportion of one part in 167,961,600,000,000. Yet a 

 few minims of this eighth culture possess all the viru- 

 lence of the first. . . . 



41 To convince those who still question the etiological 

 role of the micrococcus in the infectious disease of rabbits 

 at present under consideration, it would hardly be worth 

 while to carry our culture experiments further, as has 

 been done by Pasteur and other pioneers in this field of 

 investigation, e. g., in anthrax and in fowl-cholera. I 

 therefore turn to another line of proof. 



44 1 have fixed very definitely the thermal death-point 

 of this septic micrococcus. It is killed by exposure for 

 ten minutes to a temperature of 140 Fahr. It survives 

 exposure to 130 for the same time. This is the result 

 of a considerable number of experiments, and is estab- 

 lished by the simple method of exposing a culture-fluid 

 containing the micrococcus, and enclosed in a hermeti- 

 cally-sealed tube, to a given temperature for the time 



