142 FRAGMENTS OF SCIENCE. 



the last moulting the worm climbs the brambles 

 placed to receive it, and spins among them its cocoon. 

 It passes thus into a chrysalis ; the chrysalis becomes 

 a moth, and the moth, when liberated, lays the eggs 

 which form the starting-point of a new cycle. Now 

 Pasteur proved that the plague- corpuscles might be 

 incipient in the egg, and escape detection ; they might 

 also be germinal in the worm, and still baffle the 

 microscope. But as the worm grows, the corpuscles 

 grow also, becoming larger and more defined. In the 

 aged chrysalis they are more pronounced than in the 

 worm ; while in the moth, if either the egg or the 

 worm from which it comes should have been at all 

 stricken, the corpuscles infallibly appear, offering no 

 difficulty of detection. This was the first great point 

 made out in 1865 by Pasteur. The Italian naturalists, 

 as aforesaid, recommended the examination of the eggs 

 before risking their incubation. Pasteur showed that 

 both eggs and worms might be smitten, and still pass 

 muster, the culture of such eggs or such worms being 

 sure to entail disaster. He made the moth his starting- 

 point in seeking to regenerate the race. 



Pasteur made his first communication on this sub- 

 ject to the Academy of Sciences in September, 1865. 

 It raised a cloud of criticism. Here, forsooth, was a 

 chemist rashly quitting his proper metier and pre- 

 suming to lay down the law for the physician and 

 biologist on a subject which was eminently theirs. 

 ' On trouva etrange que je fusse si peu au courant de 

 la question ; on m'opposa des travaux qui avaient paru 

 depuis longtemps en Italic, dont les resultats montraient 

 Finutilite de mes efforts, et Fimpossibilite d'arriver a 

 un vesultat pratique dans la direction que je m'etais 

 engage. Que mon ignorance fut grande au sujet des 

 recherches sans nombre qui avaient paru depuis quinze 



