Page:Popular Science Monthly Volume 20.djvu/257

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245
DISEASE-GERMS.

new direction he has given to scientific inquiry, the number of new paths of research he has opened out, and of new clews he has afforded to those who will follow them up, and, last but by no means least, by the admirable example he has afforded, in the strictness and severity of his own methods (which have made him almost unerring in his predictions, and have given his conclusions the force of demonstrations), to those who would carry on the same lines of inquiry.

And here I would stop to note, as honorable to the disinterested character of a profession which has been lately the object of violent abuse for its (alleged) selfish and mercenary spirit, that this unique welcome was given, not to a great physician who had discovered a cure for gout, cancer, or consumption, by the use of which it would be enriched—not to a bold surgeon who had brought into vogue some wonderful operation, the success of which would tend to its renown—but to the scientific investigator of the causes of disease, whose work belongs altogether to the domain or preventive medicine, and thus, so far from being likely to benefit its members pecuniarily, tends only to diminish their remunerative employment. I never felt so proud of belonging to the body which still does me the honor to recognize me as one of its members as I did when Sir James Paget, the President of the Congress, paused in his opening address to point out on the platform behind him the greatest living exemplar of the truths he was so admirably enforcing, and when the whole of his vast audience—the like of which had never before been gathered in St. James's Hall, and perhaps never will be again—enthusiastically cheered, not once only, but again and again, the scientific veteran whose renown has spread from his quiet Parisian laboratory over the whole civilized world.

In order that the last of Pasteur's great achievements—which, with some of the ideas it suggests, it is my object now to bring before the readers of "The Nineteenth Century"—may be properly appreciated, it will be well for me to sketch out briefly what has been the nature of his life-work from the time when the singular beauty of some of his chemico-physical researches (which obtained for him in 1856 the Rumford Medal of the Royal Society) marked him out as one likely to attain further distinction.

It seems to have been by his special interest in the chemistry of organic substances that he was early led to examine into the question of fermentation, which had come to present an entirely new aspect through the discovery of Cagniard de la Tour that yeast is really a plant belonging to one of the lowest types of fungi, which grows and reproduces itself in the fermentable fluid, and whose vegetative action is presumably the cause of that fermentation, just as the development of mold in a jam-pot occasions a like change in the upper stratum of the jam, on whose surface and at whose expense it lives and reproduces itself. Chemists generally—especially Liebig, who