THE SILKWORM-DISEASE. 151 



sufficient to crush up a moth in a little water, and to 

 put a drop of this mixture under the microscope, to 

 see the corpuscles clearly, if they existed. It seemed, 

 then, that the plague was got rid of. But Pasteur was 

 not slow in recognising that the general belief in a 

 single malady could not be justified. If the experi- 

 ments of 1866 had demonstrated to him the full ex- 

 tent of the corpusculous malady, and had established 

 the principles of a treatment proper for its prevention, 

 the method he had adopted had also shown him that 

 pebrine was far from being the only cause from which 

 the silk culture suffered. 



It was in 1867 that this result was obtained. 

 From an experimental point of view, that year counted 

 double for Pasteur. Influenced by a profound sym- 

 pathy for the misery which he had witnessed during 

 two successive years, and, at the same time, impatient 

 to find the cause of the scourge, Pasteur, in the 

 months of February, March, and April, in advance of 

 the great industrial cultivations, commenced a series 

 of experiments on worms hatched by artificial heat, 

 and fed with mulberry leaves from a hothouse. 



During these forced experiments Pasteur observed 

 that out of sixteen broods derived from non-corpus- 

 culous parents, fifteen succeeded, while the sixteenth 

 perished almost entirely between the fourth moulting 

 and the climbing on to the brambles. After having 

 exhibited a most healthful appearance, the worms died 

 9 



