Pasteur and his work : from an agricultural and veterinary point of view / by George Fleming.

  • George Fleming
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Pasteur and his work : from an agricultural and veterinary point of view / by George Fleming. Source: Wellcome Collection.

    9/80 page 7
    to abandon his hitherto congenial and highly successful line of research in the domain of chemistry and molecular physics, and enter upon a new but not very dissimilar course, in which his great natural gifts and previous training were to confer such advantages. This was the very important study of fermenta¬ tion, to which his mind was attracted by an almost casual incident while he was at Strasburg. The observations of a manufacturer of chemicals in Germany had long made it known that the impure tartrate of lime of commerce, if contaminated with organic matters, and allowed to remain dissolved in water during warm weather, fermented, and yielded various products. This excited Pasteurs curiosity, and he prepared some pure right-handed tartrate of ammonia, to which he added some albuminous matter, and placed the liquid in a warm chamber, where it fermented. During the process of fermentation, the previously limpid mixture gradually became turbid, and the turbidity was found to be due to the presence and multiplication of a microscopic fungus, which, obtaining its sustenance in the liquid, acted as a living ferment. To the paratartrate of ammonia this mode of fermentation was also applied successfully, the same organism appearing, though there was a wide difference between the results of the two fermentations, so far as the products were concerned ; and the important fact was established, that the molecular dissym¬ metry proper to organic matters intervened in a phenomenon of the physiological order, and did so as a modifier of chemical affinity. The little fungus was able to assimilate the right- handed tartrate more readily than the left, though there was no chemical difference between them—only a difference in mole¬ cular constitution. Pasteur was, in this way, the first to introduce into physiological consideration the fact of the influence of the molecular dissymmetry of natural organic products, and in de¬ monstrating that the common mould or mildew could live and multiply on a purely mineral soil, such as the phosphates of potash, of magnesia, and an ammoniacal salt of an organic acid. Sowing the seeds of this mould—Penicillium glaucum—in a solution of pure paratartrate of ammonia, it was seen that in germination the left-handed acid appeared in piopoition as the right-handed disappeared, the only aliment the plant obtained for its growth being the carbon in the tartaric acid. These remarkable experiments led Pasteur to infer that fer¬ ments were always living organisms, what had previously been looked upon as ferments being merely their food. The yeast- plant had been previously discovered by Leuwenhoeck in PIol- * A salt which turns the plane of polarised light to the right; there is also a left-handed tartrate of ammonia.
    digitised image 1
    digitised image 2
    digitised image 3