274 DISCOVERY CH. 



it first discovers exactly what has to be done, and then 

 seeks the most efficient way of doing it. 



In 1865, Pasteur was urged by Dumas to undertake 

 the investigation of a disease of silkworms, called 

 pebrine, which had for several years been ruinously 

 prevalent in the south of France. The loss was estimated 

 at four millions sterling ; and the disease had spread to 

 many other countries from which silkworms' eggs had 

 been brought to France. Pasteur had no intimate 

 knowledge of silkworms, and he hesitated to take up the 

 study of the causes of the epidemic. Writing to Dumas 

 he said : 



Your proposition throws me into a great perplexity ; it is 

 indeed most flattering, and the object is a high one ; but it 

 troubles and embarrasses me ! Remember, if you please, that 

 I have never even touched a silkworm. If I had some of your 

 knowledge on the subject I should not hesitate ; it may even 

 come within the range of my present studies. However, the 

 recollection of your many kindnesses to me would leave me 

 bitter regrets if I were to decline your pressing invitation. Do 

 as you like with me. Pasteur. 



Many silkworm cultivators expressed regret that the 

 Government should choose a " mere chemist " for 

 the investigation of the disease instead of a zoologist 

 or silkworm cultivator. Pasteur only said, " Have 

 patience " ; and he began his attack of the problem 

 with the precision and acuteness of observation 

 characteristic of him. He suspected that certain 

 " corpuscles " found in the bodies of diseased silkworms 

 and in the moths and their eggs were disease-producing 

 organisms, and directed his chief studies to them, while 

 making also a careful investigation of the whole disease. 

 He proved that the disease was not only contagious, 

 but hereditary diseased moths laying diseased eggs 



