Page:Popular Science Monthly Volume 5.djvu/567

Rh to the germs suspended in the air, or deposited on the surface of the grapes and stems. M. Pasteur draws blood from an animal's veins by a similar process, and introduces it into a glass vessel in contact with pure air. The blood continues fresh for years. M. Pasteur asserts and proves by experiment that grape-juice, milk, blood, and all liquids that most readily undergo change in ordinary conditions, are incapable of fermentation in air which is pure, that is to say, deprived of the corpuscles it contained.

M. Pasteur has made still another set of experiments. He has obtained development of fermentation in liquids freed from albuminoid substances. It was supposed, before his researches, that the cells remarked in the fermentation of grape-juice proceed from the conversion of the albuminoid substances which this fluid contains in its natural state. M. Pasteur prepares a solution of sugar, tartrate of ammonia, and some other salts, and sprinkles a few yeast-globules in it. They swell, develop, and propagate in this artificial medium quite as well as in the grape-juice. So it was supposed that in the acid fermentation of milk the ferment is a product of the conversion of casein. M. Pasteur proves that supposition to be unfounded, by artificially producing the lactic ferment in a compounded liquid containing not a trace of casein. These very delicate experiments have not only increased the vogue of the panspermic theory, but they have been of great value also to vegetable physiology.

Many objections have been raised to these theories on the origin of ferments, to which M. Pasteur has almost always replied by unquestionable facts and solid reasonings, though he has sometimes done himself the injustice to be rough and contemptuous in discussion toward his opponents. Truth is strong enough to indulge charity for error. The gravest of these objections, it must be said, have applied to problems which do not concern the very foundation of the dispute between the panspermist system and its opposite. For instance, M. Trécul, the skillful and noted micrographer, M. Béchamp, and others, have proved that M. Pasteur mistakes with regard to the evolutions and transformations undergone by microscopic beings in fermenting media. M. Pasteur has certainly made more than one mistake on this subject, and there probably does exist between certain ferment-corpuscles a closer relationship than is supposed at the laboratory of the Normal School; but that does not in the least alter the fundamental character of the theory. Attention is also called to the fact that corpuscles with a determinate structure can be produced complete, without germs, in some liquids. No doubt this is true, but only on condition that the liquids are living ones. No doubt the cambium of vegetables, the blastema of animals, and generally all protoplasmic fluids, are fertile hatching-fields for the spontaneous development of the cells and fibres of living tissues. It is thus that the first elements of the embryo show themselves in the animal ovule. And in this respect the