120 THE LIFE OF PASTEUR 



In spite of your reserve— which is a part of your talent— I see 

 that you are on the track, as M. Biot would have said, and 

 that you will have your prey. Your name will stand next to 

 that of Olivier de Serres in the annals of sericiculture." 



On his return to Alais Pasteur went back to his observations 

 with his scientific ardour and his customary generous eagerness 

 to lighten the burden of others. He wrote in the introduction 

 to his Studies on Silkworm Disease the following heartfelt 

 lines — 



" A traveller coming back to the CeVennes mountains after 

 an absence of fifteen years would be saddened to see the change 

 wrought in that countryside within such a short time. For- 

 merly he might have seen robust men breaking up the rock 

 to build terraces against the side and up to the summit of each 

 mountain ; then planting mulberry trees on these terraces. 

 These men, in spite of their hard work, were then bright and 

 happy, for ease and contentment reigned in their homes. 



" Now the mulberry plantations are abandoned, the ' golden 

 tree ' no longer enriches the country, faces once beaming with 

 health and good humour are now sad and drawn. Distress 

 and hunger have succeeded to comfort and happiness." 



Pasteur thought with sorrow of the sufferings of the C£venol 

 populations. The scientific problem was narrowing itself 

 down. Faced by the contradictory facts that one successful 

 set of cocoons had produced corpuscled moths, while an ap- 

 parently unsuccessful set of worms showed neither corpuscles 

 nor spots, he had awaited the last period of these worms with 

 an impatient curiosity. He saw, amongst those which had 

 started spinning, some which as yet showed no spots and no 

 corpuscles. But corpuscles were abundant in the chrysalides, 

 those especially which were in full maturity, on the eve of be- 

 coming moths ; and none of the moths were free from them. 

 Perhaps the fact that the disease appeared in the chrysalis and 

 moth only explained the failures of succeeding series. ' It 

 was a mistake," wrote Pasteur (June 26, 1865), "to look for 

 the symptom, the corpuscle, exclusively in the eggs or the 

 worms; either might carry in themselves the germ of the 

 disease, without presenting distinct and microscopically visible 

 corpuscles. The evil developed itself chiefly in the chrysalides 

 and the moths, it was there that it should chiefly be sought. 

 There should be an infallible means of procuring healthy seed 

 by having recourse to moths free from corpuscles. 



