62 THE GERM THEORY OF DISEASE. 



this bacillus entirely pure, and succeeded in causing the dis- 

 ease in animals by inoculating them with it, after the fiftieth, 

 on to the one hundred and fiftieth generation, grown pure in 

 his flasks. The whole life history of the organism has been 

 made out, and is now substantially confirmed by a large 

 number of separate observers. Indeed, this bacillus is re- 

 cognized on sight by observers in this field of work every- 

 where. It can be bottled up and sent to any part of the world, 

 like vaccine virus, and produces the disease in regions where 

 it was unknown, just as readily as at home. This would 

 seem to be a complete demonstration of the germ theory. 

 Yet strangely enough its acceptance as such has been received 

 with extreme caution. That M. Pasteur had the virus of 

 anthrax, no one could doubt, but was it the bacillus, or was 

 it contained in some other form in the culture medium, and 

 thus carried from flask to flask. It was still claimed that 

 the molecular motion described by Liebig had not been 

 eliminated. 



KOCH. 



We have now to notice a class of experiments still more 

 conclusive than any preceding ones, and which are as yet 

 unexcelled. But it is first necessary to notice the manner in 

 which they were approached. These are by Dr. Koch, of 

 Berlin, working under the auspices of the Prussian govern- 

 ment. 



This brilliant experimentalist has been very fortunate in 

 his endeavors to devise more perfect means of recognizing 

 very minute organisms with certainty ; and of isolating them 

 by pure cultures. One of his first and most important feats 

 was the devising of a plan of staining these organisms, by 

 which he was enabled to practically isolate them from the 

 animal tissues. By his plan of aniline staining he succeeded 

 in obtaining the organisms colored a dark blue, while the 



