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Updated: June 9, 2025
I have never been able to trace the development of Torula into a true mould; but it is quite easy to prove that species of true mould, such as Penicillium, when sown in an appropriate nidus, such as a solution of tartrate of ammonia and yeast-ash, in water, with or without sugar, give rise to Torulae, similar in all respects to T. cerevisiae, except that they are, on the average, smaller.
If M. Pasteur will persist in keeping his yeast in media which are incompatible with the desired modification, it is clear that the results which he obtains must always be negative." Contrary to this perfectly gratuitous assertion of M. Trecul's we do not keep our yeast in media which are calculated to prevent its transformation into penicillium.
Moreover, Bail has observed the development of a Torula larger than T. cerevisiae, from a Mucor, a mould allied to Penicillium. It follows, therefore, that the Torulae, or organisms of yeast, are veritable plants; and conclusive experiments have proved that the power which causes the rearrangement of the molecules of the sugar is intimately connected with the life and growth of the plant.
If at any time during fermentation we pour off the fermenting liquid, the deposit of yeast remaining in the vessel may continue there, in contact with air, without our ever being able to discover the least formation of penicillium glaucum in it. We may keep a current of pure air constantly passing through the flask; the experiment will give the same result.
It even happened that the fermentations with the perfectly pure sugar instead of being slow were very active, when compared with those which we had conducted with, the commercial sugar-candy. We may here add a few words on the non-transformation of yeast into penicillium glaucum.
In structure, however, the Peronospora is as much a mould as the common Penicillium; and just as the Penicillium multiplies by the breaking up of its hyphoe into separate rounded bodies, the spores; so, in the Peronospora, certain of the hyphoe grow out into the air through the interstices of the superficial cells of the potato plant, and develop spores.
It was very soon made out that these yeast organisms, to which Turpin gave the name of Torula cerevisioe, were more nearly allied to the lower Fungi than to anything else. Indeed Turpin, and subsequently Berkeley and Hoffmann, believed that they had traced the development of the Torula into the well-known and very common mould the Penicillium glaucum.
Tartaric acid is such a substance; and if a single spore of the commonest and most troublesome of moulds Penicillium be sown in a saucerful of water, in which tartrate of ammonia, with a small percentage of phosphates and sulphates is contained, and kept warm, whether in the dark or exposed to light, it will, in a short time, give rise to a thick crust of mould, which contains many million times the weight of the original spore, in protein compounds and cellulose.
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