STUDIES OF 1868, 1869, 1870 181 



once: Is the disease contagious? Can it be carried 

 from a diseased worm to a sound worm, its neighbor? 

 It happens exactly in this disease that the excrements are 

 ordinarily viscid and smear the leaves which the worms 

 eat in common. If we imitate this natural contagion by 

 making worms eat leaves smeared with the excrement of 

 a diseased worm, we shall see them become sick in their 

 turn, as in the case of the corpuscular disease. The 

 flacherie is therefore contagious, like the pebrine. 



But here is a difference: all the worms which had 

 eaten the fresh corpuscles became sick at nearly the same 

 time. The ingested corpuscle undergoes a regular evolu- 

 tion, and it is not in the digestive tract that it develops. 

 It is not the same with the flacherie. Its stronghold is 

 in the intestine, and the time which separates the moment 

 of contagion from that of death may vary from 12 hours 

 to 3 weeks, and even more, for invariably some of 

 the worms escape death. Therefore, worms which re- 

 semble each other in regard to the corpuscle, no longer 

 do so when exposed to the germs of flacherie. Thus it is 

 that Pasteur encountered for the first time this question, 

 then so new, of receptivity to germs, differing in different 

 individuals of the same species. 



He discovered a second question just as new to him, 

 although it was a little less so to science, when he sought 

 to learn whether the germs of flacherie from different 

 sources were equivalent from the point of view of the 

 production of the disease. Some bacilli taken from an 

 artificial fermentation of mulberry leaves, for example, 

 caused death in from 8 to 15 days. If we inoculate 

 fresh worms with the substance taken from the digestive 

 tract of the former, death follows in from 6 to 8 days. 

 The virus is, therefore, augmented in intensity as the 

 result of its passage through the organism. 



Finally, the influence of the port of entry, which 



