Emil Chr. Hansen 5 Særtryk 1901-1909

592 HANSEN: CONSIDERATIONS ON TECHNICAL MYCOLOGY. laid on the intimate connection between this laboratory and the New and Old Carlsberg Breweries, and on the circumstance that just then devastating diseases, produced by wild yeasts, had shown themselves in some of the great Copenhagen breweries. By this I had an opportunity of demonstrating the practical importance of my pure-culture system in a striking manner. Had this not been the case, the adoption of so radical a reform as the introduction into breweries of yeast originating from one single cell would scarcely have been effected so rapidly as it was. In short, a whole series of fortunate circumstances occurred. The reform made its way from bottom-fermentation to top-fermenta- tion breweries; only, however, on the Continent, for in the British Isles it has to this very day met with no real acceptance. Of the reason of this I am going to speak later. The reform has also, little by little, been adopted by the other branches of the colossal industry in which the cultivation of alcoholic ferments plays an important part, including distilleries, pressed yeast factories, and the wine industry. Previously these industries had worked on in a haphazard fashion and quite in the dark, whereas after the reform they not only acquired a degree of certainty hitherto unknown, but also in many cases obtained a better product. This movement has, as might be expected, also necessitated the construction of pure culture apparatus and other apparatus required by a fermentation carried on according to exact scientific principles. In bottom-fermentation breweries, where it has been possible to carry out the pure-culture system to the greatest extent, on account of the nature of the processes, it is now in many cases worked with almost the same certainty as in the laboratory. I stated that the pure-culture system had not been accepted in the top-fermentation breweries in the British Isles. When I made that statement I thought of the typical English and Scotch beers, as porter and the other sorts of stock beers. These beers are distin- guished by a peculiar taste and flavour, which it has not been possible to obtain when only one species of Saccharomyces is used. Hjelte Claussen has of late shown that this taste and this flavour are due to other forms of yeast, namely, to some Torulæ, and that in the said beers these also are active in the formation of the rich froth-head, upon which so much stress is laid. The pure-culture system is then also capable of being employed here, but in a more complicated form than in the other breweries. At the primary fermentation a