BACTERIA IX INFECTIOUS DISEASES. 237 



and even where we do not doubt the scientific 

 accuracy of an observer, we may differ from him 

 as to the interpretation of the facts which he has 

 recorded. Those who have had the most experi- 

 ence in this difficult field of investigation, are 

 commonly the most critical and exacting with 

 reference to the alleged discoveries of others. 

 And it is now generally admitted that the only 

 satisfactory proof that a certain micro-organism 

 bears a causal relation to a disease with which it 

 is associated is that which is obtained by a series 

 of culture experiments, in which the organism is 

 completely isolated from the non-living constitu- 

 ents of the infective material containing it, and 

 in the production of the disease in question by 

 inoculation experiments with such a " pure-cul- 

 ture." The unimpeachable nature of this proof, 

 when the experiment is properly made and fre- 

 quently repeated with the same result, is made 

 apparent in the following quotation from a paper 

 by the writer relating to " a fatal form of septi- 

 caemia in the rabbit." l 



" In my previous paper I related a series of experi- 

 ments commenced July 6th, to which I must refer the 

 reader as properly introducing the following : - 



" The culture-fluid (No. 6) used in Experiment No. 3 

 (July 26th) was laid aside in an hermetically-sealed 

 culture-flask until September 12th, when a minute drop 

 was used to inoculate sterilized bouillon in culture-tube 

 No. 7, This, placed in a culture-oven at 100 Fahr. for 

 twenty-four hours, became clouded, and upon micro- 

 i Med. Times, Phila., Nov. 4th, 1882, p. 81. 



