158 LOUIS PASTEUR. 



these germs of vibrios are carried into the intestinal 

 canal of the worm, develop and multiply themselves, 

 and completely disturb the digestive functions, unless 

 the digestion is so strong that the germs are imme- 

 diately arrested, and disposed of like the food itself. 

 This is what happens when the worms are in full 

 vigour. It is a struggle for life, in which the worms 

 often gain the victory. 



Giving to some very healthy worms a meal of 

 leaves covered with the dry dust of a silkworm 

 nursery, infected the year before by pelrine and 

 flaclierie, Pasteur reproduced flaclierie, and not pebrine. 

 Still more readily did he produce the first of these 

 maladies, when he gave, as food, leaves polluted by 

 the contents of the intestinal canal of worms which 

 had died of the disease. As in the case of pelrine, 

 the excreta of the worms attacked by flaclierie, de- 

 filing the leaves, carry .the mischief to the healthy 

 worms, or add to the dangerous fermentation in the 

 intestines of those which are already in part attacked. 



To preserve silkworms from accidental flaclierie, 

 hygienic precautions are sufficient. As regards here- 

 ditary flaclierie, or, to speak more correctly, that which 

 develops itself easily on any diminution of vigour in 

 the eggs and in the embryo, Pasteur again found a 

 remedy by having recourse to the microscope. By 

 means of the microscope it is possible to obtain in- 

 formation as to the health of the worms, the chry- 



