240 THE POPULAR SCIENCE MONTHLY. 



own, which was a triumph for his position. Having shown, by means 

 of bottles of air collectsd from different heights in a mountain-region, 

 that the number of germs in the air diminishes with the elevation above 

 the earth, and that air can be got free from germs and unproductive, 

 M. Pasteur asserted decisively : " There is no circumstance now 

 known that permits us to affirm that microscopic beings have come into 

 the world without germs, without parents like themselves. Those who 

 affirm it have been victims of illusions, of experiments badly made, and 

 infected with errors which they have not been able to perceive or avoid. 

 Spontaneous generation is a chimera." M. Flourens, Perpetual Secre- 

 tary of the Academy, said : " The experiments are decisive. To have 

 animalcules, what is necessary, if spontaneous generation is real ? Air 

 and putrescible liquids. Now, M. Pasteur brings air and putrescible 

 liquids together, and nothing comes of it. Spontaneous generation, 

 then, is not. To doubt still is not to comprehend the question." There 

 were, however, some who still doubted, and to satisfy them M. Pasteur 

 offered, as a final test, to show that it was possible to secure, at 

 any point, a bottle of air containing no germs, which would, conse- 

 quently, give no life. The Academy's committee approved the propo- 

 sition ; but M. Pouchet and his friends pleaded for delay, and finally 

 retired from the contest. 



The silk-raising industry of the south of France was threatened 

 with ruin by a disease that was destroying the silk- worms, killing them 

 in the Oi^'g^ or at a later stage of growth. Eggs, free from the disease, 

 were imported from other countries. The first brood flourished, but 

 the next one usually fell victims to the infection, and the malady 

 spread. All usual efforts to prevent it or detect its cause having failed, 

 a commission was appointed to make special investigations, and M. 

 Pasteur was asked to direct them personally. He did not wish to un- 

 dertake the work, because it would withdraw him from his studies of 

 the ferments. He, moreover, had never had anything to do with silk- 

 worms. " So much the better," said Dumas. " You know nothing about 

 the matter, and have no ideas to interfere with those which your obser- 

 vations will suggest." Theories were abundant, but the most recent 

 and best authorities agreed that the diseased worms were beset by cor- 

 puscles, visible only under the microscope. He began his investigations 

 with the idea that these corpuscles were connected with the disease, 

 although assurances were not wanting that they also existed in a normal 

 condition of the silk-worm. M. Pasteur's wife and daughters, and his 

 assistants in the normal school, associated themselves with him in the 

 studies, and became, for the time, amateur silk-raisers. He studied 

 the worms in every condition, and the corpuscles in every relation, for 

 five years. He found that there were two diseases— ^the contagious, 

 deadly pebrine, the work of the corpuscles, and flachery, produced by 

 an internal organism ; and "became so well acquainted with the causes 

 of the trouble and their different manifestations that he could, at will, 



