182 PASTEUR: THE HISTORY OF A MIND 



Davaine was at this moment occupied in studying in 

 anthrax, was also apparent to Pasteur through the com- 

 parison which he had made of the results of inoculation 

 by pricks and by contamination of the digestive tract. 

 We see what an excellent preparation these studies on 

 flacherie gave him, and with what good reason he ad- 

 vised young medical students, who later learned the 

 path to his laboratory, to read these two volumes on the 

 disease of silkworms: the great teachings of microbial 

 pathology are already found there. 



This is not all. We have seen that the germ of the 

 corpuscle is not common, and must be acquired from a 

 living worm, or from one just dead, in order to preserve 

 its vitality. Pasteur even believed, as we have seen, 

 that it had no other habitat than the silkworm, and 

 that man could make pe*brine disappear by making the 

 production of sound eggs universal. On the contrary, 

 the appearance of flacherie is sometimes spontaneous, 

 and may result from an accident or from some error 

 during the breeding. Whence, then, come the germs? 

 The germ is common, replies Pasteur. It suffices to 

 leave in a flask, at summer temperature, a bit of bruised 

 mulberry-leaf, in order to see appear in the maceration 

 microscopic organisms in every way similar to those 

 which one encounters in the digestive tract of the 

 flatulent worms, a canal which, in fact, seems to have 

 become an inert receptacle. In a healthy worm the 

 tract arrests or prevents all development of microbes; 

 in a flatulent worm, it opens the way for the germs which 

 the leaf introduces, and, with approximately the same 

 virulence, the germs of the flasks and the germs of the in- 

 testinal tract behave the same. That explains to us how 

 the disease can appear sometimes without having been 

 introduced from a distance, a thing which did not happen, 

 at least so Pasteur thought, in the corpuscular disease? 



