60 OHKilNATION OF LIVING BEINGS 



a ;< \v viars after lliis, the. question began to be 

 vrry hotly discussed in France. There was M. Pouchet, a 

 professor at Rouen, a very learned man, but certainly not 

 a \- ! experimentalist. He published a number of 



experiments of his own, some of which were very ingenious, 

 to show that if you went to work in a proper way, there 

 was a truth in the doctrine of spontaneous generation. 

 Well, it was one of the most fortunate things in the world 

 that M. Powhet took up this question, because it induced 

 a distinguished French chemist, M. Pasteur, to take up the 

 question on the other side ; and he has certainly worked 

 it out in the most perfect manner. I am glad to say, too, 

 that he has published his researches in time to enable me 

 to give you an account of them. He verified all the experi- 

 ments which I have just mentioned to you and then 

 finding those extraordinary anomalies, as in the case of 

 the mercury bath and the milk, he set himself to work to 

 discover their nature. In the case of milk he found it to 

 DC a question of temperature. Milk in a fresh state is 



htly alkaline ; and it is a very curious circumstance, 

 but this very slight degree of alkalinity seems to have the 

 effect of preserving the organisms which fall into it from 

 the air from being destroyed at a temperature of 212, 

 which is the boiling point. But if you raise the temperature 

 10 when you boil it, the milk behaves like everything else ; 

 and if the air with which it comes in contact, after being 

 boiled at this temperature, is passed through a red-hot 

 tube, you will not get a trace of organisms. 



He then turned his attention to the mercury bath, and 

 found on examination that the surface of the mercury was 

 almost iil\\ays covered with a very fine dust. He found 

 that even the mercury itself was positively full of organic 

 matters; that from being constantly exposed to the air, 

 it had collected an immense number of these infusorial 

 organisms from the air. Well, under these circumstances 

 he felt that the case was quite clear, and that the mercury 

 was not what it had appeared to M. Schwann to be, a bar 

 to the admission of these organisms ; but that, in reality, 



led as a MtCTVOir from which the infusion was imme- 

 diately supplied with the large quantity that had so 

 pu//lrd him. 



Hut not content with explaining the experiments of 

 others, M. Pasteur went to work to satisfy himself com- 

 pletely. He said to himself : " If my view is right, and 



