486 THE WAR WITH THE MICROBES. 



the " principle vegetoauiinal." For nearly forty years afterwards this 

 theory was applied by chemists to all fermentations. It was supposed 

 that the albuminoid substance present exposed to the oxygen of the air 

 experienced a progressively variable alteration, that diverse modifica- 

 tions of matter were produced which constituted the ferments of diverse 

 nature. The fermentation was the result of the molecular movement 

 thus communicated. These theories were based upon an erroneous 

 interpretation of what occurred under certain conditions. There exists 

 in wine, when it is being converted into vinegar, a substance which acts 

 to bring about this modification, but this is not dead albuminoid matter, 

 but a living plant. This fact the lamented chemist, Pasteur, demon- 

 strated in his careful studies upon the production of wine and its con 

 version into vinegar. Before this time, it is true, there were many who 

 failed to accept the theory of spontaneous oxidation, and endeavored to 

 show that if fermentable liquids were boiled in flasks which were then 

 immediately sealed, the fermentation could not take place. But this 

 did not fulfill the demands of one school of chemists, viz, that plenty of 

 oxygen gas should always be present. When the liquid was boiled in 

 contact with air which had previously been drawn through sulphuric 

 acid, it was claimed that the air had undergone some chemical change, 

 so it was not until 1854 that this objection was overcome by previously 

 passing the air in the presence of which boiling took place through 

 cotton, and it was then that this school of chemists found their theories 

 in danger. Pasteur demonstrated that the plant present in the prepa- 

 ration of vinegar was the simplest form of life, a cell which could be 

 easily destroyed by heat. Its presence was absolutely necessary for 

 fermentation, and without the living cell no amount of dead vegetable 

 matter could cause the peculiar molecular disarrangement which had 

 been claimed. Liebig had contended that as long as the juice of the 

 grape remained away from contact with the oxygen of the air the nec- 

 essary motion could not be imparted to the molecules, which move- 

 ment subsequently caused the phenomena of fermentation. Thus was 

 brought to an end the strife between the two schools of vitalists and 

 chemists ; the one school of chemists demanding the presence of oxygen 

 only, the other the presence of a living plant cell in addition to oxygen. 

 From this strife of the two schools was evolved in reality a new science 

 and new theories, which have made the past thirty years marvelous in 

 giving explanations of many of the simplest phenomena of plant and 

 animal life and death, placed the practice of medicine upon a scientific 

 basis, and rendered possible an intelligent system of agriculture and 

 animal husbandry. 



Pasteur's discoveries also served to explain the true cause of the 

 poisonous properties of spoiled meats and other foods, stagnant water, 

 and water from marshy countries. For more than half a century before 

 this time a number of investigators had proved the dangerous charac- 

 ter of old sausage, meats, bread, and the like. Kerrier concluded that 

 they contained a fatty acid to which the poisonous action was due; 



