SPONTANEOUS GENERATION. 569 
the flasks thus supplied with glacier air showed signs of life 
afterward, while eight out of twenty of the same infusions, 
supplied with the air of the plains, became crowded with 
life. He took his flasks into the caves under the Obser- 
vatory of Paris, and found the still air in these caves 
devoid of generative power. These and other experiments, 
carried out with a severity perfectly obvious to the instructed 
scientific reader, and accompanied by a logic equally 
severe, restored the conviction that, even in these lower 
readies of the scale of being, life does not appear without 
the operation of antecedent life. 
The main position of Pasteur has been strengthened by 
practical researches of the most momentous kind. He has 
applied the knowledge won from his inquiries to the 
preservation of wine and beer, to the manufacture of 
vinegar, to the staying of the plague which threatened 
utter destruction of the silk husbandry of France, and to 
the examination of other formidable diseases which assail 
the higher animals, including man. His relation to the 
improvements which Professor Lister has introduced into 
surgery, is shown by a letter quoted in his Etudes sur la 
Biere.* Professor Lister there expressly thanks Pasteur 
for having given him the only principle which could have 
conducted the antiseptic system to a successful issue. The 
strictures regarding defects of reasoning, to which we have 
been lately accustomed, throw abundant light upon their 
author, but no shade upon Pasteur. 
Eedi, as we have seen, proved the maggots of putrefying 
flesh to be derived from the eggs of flies; Schwann proved 
putrefaction itself to be the concomitant of far lower forms 
of life than those dealt with by Redi. Our knowledge 
here, as elsewhere in connection with this subject, has been 
vastly extended by Professor Cohn, of Breslau. " No 
putrefaction," he says, " can occur in a nitrogenous sub- 
stance if its bacteria be destroyed and new ones prevented 
from entering it. Putrefaction begins as soon as bacteria, 
even in the smallest numbers, are admitted either accident- 
ally or purposely. It progresses in direct proportion to the 
multiplication of the bacteria, it is retarded when they 
exhibit low vitality, and is stopped by all influences which 
either hinder their development or kill them. All bacte- 
* P. 43, 
