Since the publication of the author’s “Studies on the Diseases of Wine, and the Dangers resulting to Wine and Beer from the Microscopic Parasites found therein,” some intelligent brewers have derived considerable profit from the application of the theories laid down in that work. Footnote 19: If we put a handful of germinating barley from a maltster’s cistern into a little water, and examine drops of the liquid, after it has become turbid, under a microscope, we shall be amazed at the wonderful number of strange microscopic organisms that swarm on the surface of the grains and on the sides of the cistern. There is no doubt that their presence is injurious to germination, inasmuch as they absorb much oxygen; moreover, they acidify the grain and cause it to deteriorate. Footnote 20: In these experiments the asbestos is only introduced by way of extra precaution. Originally, in his early experiments in connection with the subject of spontaneous generation, the results of which were published in 1860-62, the author did not use it, and he observed no ill effects resulting from the omission; now, however, he constantly makes use of it. In studies of this kind novel precautions are never thrown away; moreover, the presence of this asbestos is a sure bar to the entrance of insects. The author has preserved for a long time a flask, in the slender neck of which an insect is contained; he killed it with a flame just as it was approaching the liquid. Quite recently, M. Calmettes, a young engineer from the École Centrale, when engaged, at Tantonville, in Tourtel’s brewery, in carrying out certain practical experiments in connection with the process that will he described in one of the later chapters of this work, wrote complaining that his flasks had been suddenly invaded by a swarm of aphides, scarcely larger than phylloxeras, and that many of them had even penetrated into the inside of the curved tubes. CHAPTER III. On the Origin of Ferments properly so called. The new process of brewing, which it is the principal object of this work to explain, and which will follow as an immediate and inevitable deduction from the novel facts herein demonstrated, cannot be fully understood without a knowledge of all the principles upon which it is founded. One of the most essential of these has reference to the purity of our fermentation. We should gain but little from the use of a yeast uncontaminated by any foreign germs if natural organic substances had the power of organizing themselves by means of spontaneous generation, or by some transformation which took place amongst them, or even by a conversion of certain microscopic beings into certain others. Theories of this kind are still warmly advocated, but, to our thinking, rather from sentimental considerations or prejudice than from any basis of serious experimental proofs.