294 FRAGMENTS OF SCIENCE. 



of infection. He inoculated healthy worms with the cor- 

 pusculous matter, and watched the consequent growth of 

 the disease. He showed how the worms inoculate each 

 other by the infliction of visible wounds with their claws. 

 In various cases he washed the claws, and found corpuscles 

 in the water. He demonstrated the spread of infection by 

 the simple association of healthy and diseased worms. The 

 diseased Avorms sullied the leaves by their dejections, they 

 also used their claws, and spread infection in both ways. 

 It was no hypothetical infected medium that killed the 

 worms, but a definitely-organized and isolated thing. He 

 examined the question of contagion at a distance, and de- 

 monstrated its existence. In fact, as might be expected 

 from Pasteur's antecedents, the investigation was exhaus- 

 tive, the skill and beauty of his manipulation finding fitting 

 correlatives in the strength and clearness of his thought. 



. The following quotation from Pasteur's work clearly 

 shows the relation in which his researches stand to this 

 great question : 



" Place," he says, " the most skilful educator, even the most expert 

 microscopist, in presence of large educations which present the symp- 

 toms described in our experiments ; his judgment will necessarily be er- 

 roneous if he confines himself to the knowledge which preceded my re- 

 searches. The worms will not present to him the slightest spot of 

 pebrine ; the microscope will not reveal the existence of corpuscles ; the 

 mortality of the worms will be null or insignificant ; and the cocoons 

 leave nothing to be desired. Our observer would, therefore, conclude 

 without hesitation that the eggs produced will be good for incubation. 

 The truth is, on the contrary, that all the worms of these fine crops have 

 been poisoned ; that, from the beginning, they carried in them the germ 

 of the malady ; ready to multiply itself beyond measure in the chrysa- 

 lides and the moths, thence to pass into the eggs and smite with sterility 

 the next generation. And what is the first cause of the evil concealed 

 under so deceitful an exterior ? In our experiments we can, so to speak, 

 touch it with our fingers. It is entirely the effect of a single corpuscu- 

 lous repast ; an effect more or less prompt according to the epoch of life 

 of the worm that has eaten the poisoned food." 



