THE SILKWORM-DISEASE. 153 



tions, Pasteur discerned that what had passed in his 

 own laboratory was of very general occurrence, and 

 that, contrary to the received opinion, two distinct 

 maladies divided between them the cause of all the 

 misfortunes. Pebrine was evidently the most widely 

 spread, but flaclierie had also its share, and a very 

 large share, in the calamity. 



Here, once more, the microscope came to Pasteur's 

 assistance. If, at the period of the rearing of the 

 silkworms, when the mean temperature is always 

 rather high, some mulberry leaves are crushed in a 

 mortar and mixed with a little water, the liquid being 

 left to itself, in twenty-four hours it will be found 

 filled with microscopic organisms; some motionless, 

 resembling little rods or spores joined end to end, 

 like strings of beads, others more or less active, 

 flexible, endowed with a sinuous movement like that 

 of the vibrios found in nearly all organic infusions in 

 process of decomposition. Whence come these micro- 

 scopic organisms ? The facts relating to spontaneous 

 generation indicate that the germs of these organisms 

 were on the surface of the pounded leaf, spread in the 

 form of dust over the instruments used to triturate 

 the leaf, possibly on the mortar, the pestle, or in the 

 water added to the pounded leaves. 



It is a curious fact, that if the intestinal canal of 

 a worm in full process of digestion be opened, the 

 pounded leaf which fills it from one end to the other 



