ii6 PASTEUR 



whence they enter the silkworm by the mouth ; and 

 that the sick inoculate the healthy by crawling 

 over them and piercing the skin with their pointed 

 claws. He therefore emphasized the importance of 

 segregating the sound caterpillars. 



The above account conveys no impression of the 

 difficulties under which Pasteur worked. His re- 

 searches were not only new to himself but to the 

 world. Processes which at the present day are 

 carried out by every medical student had to be devised 

 for the first time. He had to combat the criticism of 

 scientific men, and to overcome the almost invincible 

 ignorance of the agriculturist, an ignorance which at 

 one time advocated the desperate remedy of asperging 

 with absinthe the leaves of the mulberry on which 

 the silkworms fed. 



Perhaps Pasteur's greatest difficulty was the fact 

 that the silkworms did not suffer from Pebrine alone; 

 and it was some time before he recognized that he 

 had to deal, not with one disease, but with two. The 

 second disease, known as the ' Flacherie,' is a disease 

 of the digestive system caused by overcrowding and 

 insanitary conditions in the silkworm nurseries. Like 

 Pebrine, it is caused by a micrococcus, Micrococcus 

 bombycis. It was whilst investigating this creature 

 that Pasteur discovered that, although the germ itself 

 cannot survive a lengthy period of desiccation, it does 

 in certain circumstances form spores which can survive 

 conditions fatal to the mature organism. This is the 

 first case recorded of a pathogenic organism pro- 

 ducing spores, the existence of which has explained 

 so many problems in the spread of disease. 



During the period from 1865 to 1870 Pasteur was by 

 no means occupied solely by the silkworm epidemic. 

 In many respects it was a sad epoch in his life. Only 

 nine days after his first arrival at Alais he was sum- 

 moned to Arbois to see his dying father, but arrived 



