142 LOUIS PASTEUR, 



influence. Pasteur soon succeeded, by accurate ex- 

 periments, in proving absolutely that the evil was 

 contagious. 



One of the first experiments was as follows. After 

 their first moulting, he took some very sound worms 

 free from corpuscles, and fed them with corpusculous 

 matter, which he prepared in the following simple 

 manner. He pounded up a silkworm in a little water, 

 and passed a paint-brush dipped in this liquid over 

 the whole surface of the leaves. During several days 

 there was not the least appearance of disease in the 

 worms fed on those leaves ; they reached their second 

 moulting at the same time as the standard worms 

 which had not been infected. The second moulting 

 was accomplished without any drawback. This was 

 a proof that all the worms, those infected as well as 

 the standard lot, had taken the same amount of 

 nourishment. The parasite was apparently not pre- 

 sent. Matters remained in this state for some days 

 longer. Even the third moulting was got through 

 without any marked difference between the two groups 

 of worms. But soon important changes set in. The 

 corpuscles, which had hitherto only showed themselves 

 in the integuments of the intestines, began to appear 

 in the other organs. From the second day follow- 

 ing the third moulting that is to say, the twelfth 

 after the infection a visible inequality distinguished 

 the infected from the non-infected worms. Those 



