392 BACTERIA IN INFECTIOUS DISEASES. 



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published in various journals, and states that in 

 2,509 cases reported, the bacilli were found in 

 2,417- Koch, himself, recognizes, however, that 

 this kind of evidence cannot be taken as proof of 

 the causal relation of the bacillus to the morbid 

 process which results in the formation of tubercles 

 in various parts of the body. For it may be that 

 the bacillus is present in tuberculous material 

 simply because this furnishes the pabulum neces- 

 sary for its development, and is absent from the 

 sputum of bronchitis, for example, because this 

 does not constitute a suitable culture-medium ; or 

 because, being secreted from the surface of an 

 inflamed mucous membrane, and quickly removed 

 by expectoration, there is no time for the develop, 

 ment of this bacillus, which Koch has shown re- 

 quires at least a week before any evidence of 

 multiplication is seen upon the surface of sterilized 

 blood-serum. This time would, however, be af- 

 forded in the cheesy contents of a tubercular 

 nodule, or in a cavity where necrotic products 

 were retained for a considerable time. 



A recent French writer, Cochez, claims that the 

 sputum of phthisical patients constitutes a favora- 

 ble culture-medium for the tubercle bacillus. The 

 writer, also, has been inclined to believe that the 

 bacilli are more numerous in sputum which has 

 been kept for a day or two than in the same 

 material when first obtained. This, if true, is not 

 very favorable to the view that they are the cause 

 of the morbid process which results in the forma- 



