THE SILKWOEM-DISEASE. 149 



presence of corpusculous parasites in the egg ? The 

 egg comes into existence during that marvellous phase 

 of the life of a silkworm when, after having spun its 

 cocoon, it sleeps within it as a chrysalis, resolving itself, 

 so to speak, into those kinds of albumen and yelk 

 from which the fully-formed moth will emerge, as a 

 chick emerges from its egg. Let anyone imagine 

 this origin of an approaching life, no longer in its 

 normal purity, but associated with a parasite which 

 will find in the materials surrounding it, so adapted 

 to life and transformation, the elements of its own 

 nourishment and multiplication. This parasite will be 

 present when the eggs of the female moth, tender and 

 soft as albumen, begin to define their outlines. Woe 

 betide those eggs if they then enclose any particles of 

 corpuscle, or of its original matrix. In vain will the 

 envelope of those eggs become by degrees hard and 

 horny ; the enemy is within, and later on he will be 

 discovered in the embryo of the silkworm. 



Thus this terrible plague is at the same time con- 

 tagious and hereditary, helping us to understand the 

 evolution of this double character in certain maladies 

 both of men and animals. 



II. 



The first time Pasteur went to Alais the silkworm 

 epidemic was universally attributed to a single cause 

 pebrine. Pebrine was called the disease. This 



