130 LOUIS PASTEUR. 



When the worms of a cultivation have all spun 

 their cocoons, they are smothered in a steam stove, 

 and, after being dried in the sun, they are handed 

 over to the spinners. If it is desired to reserve some 

 of the cocoons for seed, instead of being smothered, 

 they are strung together in chaplets. After about 

 three weeks, the moth comes out of its chrysalis. It 

 pierces the cocoon by means of a liquid which issues 

 from its mouth, and which has the property of so 

 softening the silk that the moth is able to pass through 

 the cocoon. It has hardly dried itself and developed 

 its wings when the males and females pair for several 

 hours. Then the females lay their eggs, of which they 

 can produce from four to six hundred. These are all 

 the phases through which silkworms pass in the space 

 of two months. 



In the epidemic which ravaged the silkworm nur- 

 series in 1849 the symptoms were numerous and 

 changeable. Sometimes the disease exhibited itself 

 immediately. Many of the eggs were sterile, or the 

 worms died during the first days of their existence. 

 Often the hatching was excellent, and the worms ar- 

 rived at their first moulting, but that moulting was a 

 failure. A great number of the worms, taking little 

 nourishment at each repast, remained smaller than 

 the others, having a rather shining appearance and a 

 blackish tint. Instead of all the worms going through 



