342 STUDIES ON FERMENTATIOX. 



ratus have proved that, by adopting such an arrangement, beer, 

 a liquid peculiarly liable to change, may be kept as long as we 

 wish, for weeks or months, in contact with air, since the tube g 

 is open, without evincing the least symptom of disease. It 

 matters litcle whether the leaves and strobiles of the hops are 

 introduced with the hot wort or strained off ; the result is the 

 same. On the other hand, a leak in the apparatus from which 

 the wort gets mixed with ordinary water from outside during 

 cooling, will speedily effect a change in the wort and cause it 

 to swarm with vibrios, or butyric ferment, lactic ferment, and 

 other germs of disease, whilst its taste will be rendered extremely 

 naiiseous. It can only be through one's own fault, that is, from 

 want of skill in carrj'ing out the operation, that any change 

 can be brought about by the water in the gutter not being 

 kept out of the fermenting vessel. That water may even 

 become putrid without the organisms contained in it being able 

 to reach the wort in the fermenting vessel. The apparatus 

 may be of any size whatever; we have worked with vessels 

 containing 12 hectolitres with as much ease and certainty as 

 when we used an apparatus of 1 hectolitre (22 gallons). 



It is eas}" to carry out the process of cooling in the presence 

 of carbonic acid gas if we fit a bent tube, similar to a c d e/g, to 

 the second tubulure D. Through this tube, or its companion, 

 the gas can be passed as it issues from an apparatus in which it 

 is generated, or from a gasometer filled with it, or from a vessel 

 of beer undergoing fermentation. 



However, there is no necessity that the cooling should take 

 place in the fermenting vessel. It may be effected scparatelj-, 

 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 imder the same conditions. Jets 

 of steam, which are already extensivel}' 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 



