18(551870 121 



This idea was like a searchlight flashed into the darkness. 

 Pasteur thus formulated his hypothesis: "Every moth con- 

 taining corpuscles must give birth to diseased seed. If a 

 moth only has a few corpuscles, its eggs will provide worms 

 without any, or which will only develop them towards the end 

 of their life. If the moth is much infected, the disease will 

 show itself in the earliest stages of the worm, either by 

 corpuscles or by other unhealthy symptoms." 



Pasteur studied hundreds of moths under the microscope. 

 Nearly all, two or three couples excepted, were corpuscled, but 

 that restricted quantity was increased by a precious gift. Two 

 people, who had heard Pasteur ventilate his theories, brought 

 him five moths born of a local race of silkworms and nurtured 

 in the small neighbouring town of Anduze in the Turkish 

 fashion, i.e. without any of the usual precautions consisting in 

 keeping the worms in nurseries heated at an equal temperature. 

 Everything having been tried, this system had also had its 

 turn, without any appreciable success. By a fortunate cir- 

 cumstance, four out of those five moths were healthy. 



Pasteur looked forward to the study in comparisons that 

 the following spring would bring when worms were hatched 

 both from the healthy and the diseased seed. In the mean- 

 while, only a few of the Alaisians, including M. Pages, the 

 Mayor, and M. de Lachadenede, really felt any confidence in 

 these results. Most of the other silkworm cultivators were dis- 

 posed to criticize everything, without having the patience to 

 wait for results. They expressed much regret that the Govern- 

 ment should choose a " mere chemist " for those investigations 

 instead of some zoologist or silkworm cultivator. Pasteur only 

 said, "Have patience." 



He returned to Paris, where fresh sorrow awaited him : 

 Camille, his youngest child, only two years old, was seriously 

 ill. He watched over her night after night, spending his days 

 at his task in the laboratory, and returning in the evening to 

 the bedside of his dying child. During that same period he 

 was asked for an article on Lavoisier by J. B. Dumas, who 

 had been requested by the Government to publish his works. 



" No one," wrote Dumas to Pasteur " has read Lavoisier 

 with more attention than you have ; no one can judge of him 

 better. . . . The chance which caused me to be born before 

 you has placed me in communication with surroundings and 

 with men in whom I have found the ideas and feelings which 



