144 LOUIS PASTEUR. 



the effect of the corpuscles developed in the interior ; 

 they were but a sign, already removed from the true 

 seat of the evil. ' If these spots of pebrine,' thought 

 Pasteur, ' were considered in conjunction with certain 

 human maladies in which spots and irruptions appear 

 on the body, what interesting inductions might pre- 

 sent themselves to minds prepared to receive them ! ' 



Pasteur was never tired of repeating this curious 

 experiment, or of varying its conditions. Sometimes 

 he introduced the corpusculous food into healthy 

 worms at their birth, sometimes at the second or 

 third moulting. Occasionally, when the worms were 

 about to spin their cocoons, the corpusculous food was 

 given them. All the disasters that were known to 

 have happened in the silkworm nurseries, their extent 

 and then* varied forms, were faithfully reproduced. 

 Pasteur created at will any required manifestation of 

 pebrine. When he infected quite healthy worms, after 

 their fourth moulting, with fresh corpusculous matter, 

 these worms, even after several meals of corpusculous 

 leaves alternated with meals of wholesome leaves, 

 made their cocoons. It might have been supposed 

 that in this case the contagion had not taken effect. 

 This was but a deceptive appearance. The communi- 

 cation of the disease exhibited itself in a marked de- 

 gree in the chrysalides and in the moths. Many of 

 the chrysalides died before they turned into moths, 

 and their bodies might be said to be entirely composed 



