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These changes in the vegetative forms are scarcely perceptible, in the case of penicillium and mycoderma vini, but they are very evident in the case of aspergillus, consisting of a marked tendency on the part of the submerged mycelial filaments to increase in diameter, and to develop cross partitions at short intervals, so that they sometimes bear a resemblance to chains of conidia.
Moreover, Bail has observed the development of a Torula larger than T. cerevisioe, from a Mucor, a mould allied to Penicillium. It follows, therefore, that the Toruloe, 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.
Turpin, Hoffmann, and Trecul have, therefore, been based on one of these illusions which we meet with so frequently in microscopical observations. To bring about the transformation of the yeast of beer into mycoderma cerevisiae or into penicillium glaucum we must accept the conditions under which these two forms are obtained.
Nevertheless, this is a medium peculiarly adapted to the development of this mould, inasmuch as if we were to introduce merely a few spores of penicillium an abundant vegetation of that growth will afterwards appear on the deposit. The descriptions of Messrs.
What we have said of Penicillium glaucum will apply equally to Mycoderma cerevisiae. Notwithstanding that Turpin and Trecul may assert to the contrary, yeast, in contact with air as it was under the conditions of the experiment just described, will not yield Mycoderma vini or Mycoderma cerevisiae any more than it will Penicillium.
It was very soon made out that these yeast organisms, to which Turpin gave the name of Torula cerevisiae, 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.
The phenomena are as massive and wide-spread as is anything in Nature, and the study of them is as tedious, repellent and undignified. To reject it for its unromantic character is like rejecting bacteriology because penicillium glaucum grows on horse-dung and bacterium termo lives in putrefaction. Scientific men have long ago ceased to think of the dignity of the materials they work in.
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 Toruloe, similar in all respects to T. cerevisioe, except that they are, on the average, smaller.
Put the substance to be tested into a flask with some small pieces of bread, sterilize for half an hour at 120° C. When cold, inoculate with a culture of Penicillium brevicaule, and keep at a temperature of 37° C. If arsenic is present, a garlic-like odour is noticed in twenty four hours, due to arseniuretted hydrogen or an organic combination of arsenic.
As we have just seen, the principal aim and object of our experiment was to bring this minute plant into contact with air, and under conditions that would allow the penicillium to develop with perfect freedom.
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