THE DISEASES OF SILK WORMS 133 



eggs were called, to the growers. The method he 

 recommended, however, sometimes failed, and Pas- 

 teur was led to conclude that diseased progeny 

 might arise from moths possessing no corpuscles. 

 Often worms sickened and died from what he con- 

 sidered pebrine, without having any corpuscles at 

 all. He was therefore led to regard the corpuscles 

 as a sort of product of the disease instead of its 

 cause, — a product, like certain other symptoms of 

 diseases, which might or might not appear accord- 

 ing to various circumstances which are little under- 

 stood. He believed that the disease preceded the 

 existence of the corpuscles, and that feeding worms 

 with corpuscular matter would sometimes give them 

 the disease without the appearance of corpuscles in 

 the infected worms. He was also unable to find 

 evidence that the corpuscles reproduced themselves 

 like the bacteria and the yeasts by either fission 

 or budding. 



Thus far, in spite of some success, the disease 

 proved to be baffling. Duclaux, one of his co- 

 workers in the silk worm investigation, remarks, 

 "In 1867 Pasteur had distributed by small lots the 

 healthy eggs prepared in 1866, and the success, we 

 knew, had been general. Meanwhile, as the letters 

 came announcing the results of the cultures, we 



