However, there is no necessity that the cooling should take place in the fermenting vessel. It may be effected separately, in vessels of greater or less depth, in spiral coils surrounded with cold water, or in any kind of refrigerator, provided always that the conditions of purity are satisfied, and that the flow of the cooled wort takes place under the same conditions. Jets of steam, which are already extensively used for the cleansing of pipes in breweries, may be employed here with great advantage. The pitching may be effected in various ways. A two-necked flask of a capacity of from 200 to 300 cc. (about 7 to 10 fl. ozs.), in which not more than 100 cc. (3-½ fl. ozs.) of wort has been fermented, will be sufficient for an apparatus of 1 hectolitre (22 gallons), although the flask may not contain more than 1 or 2 decigrammes (1-½ to 3 grains) of yeast. In the manufacture of beer, as at present conducted, the employment of so minute a quantity of yeast would lead to most disastrous results. The fermentation would unfailingly become lactic and butyric, since the foreign germs with which commercial worts and yeasts are always contaminated would have ample time to develop during the first twenty-four or forty-eight hours, whilst the small quantity of yeast used in the pitching could scarcely do more than begin to develop during that time. It is simply with the object of avoiding these secondary fermentations that the brewer uses large quantities of yeast for pitching. After the wort and yeast have been _pulled up_,[163] a process which every practical brewer adopts after pitching, every part of the liquid is occupied by a multitude of yeast-cells, which seize upon the oxygen in solution, germinate with activity, turn to their own account the food-supplies most easily assimilated, and prevent the growth of the germs of disease-ferments. In the new process which we are now explaining, things happen quite differently. Our wort is pure, and our yeast is pure, and if only a single cell of yeast were introduced into the wort, the vital activity of this would be sufficient to bring about alcoholic fermentation, and to transform the wort into beer, without our having the least reason to apprehend the simultaneous development of any other organisms whatsoever. In short, the new process enables us to pitch with as small a quantity of yeast as we like. It is, nevertheless, inexpedient to employ too minute a quantity, since by doing so we should retard the commencement of fermentation. [Illustration: Fig. 78.] [Illustration: Fig. 79.]