AIR AND WATER. 71 



parallel series of experiments with sterile beer. They rendered 

 the wort turbid, and imparted a peculiar smell to it. Among 

 the moulds the following were the most frequent : Asper- 

 gillus, Mucor stolonifer, M. mucedo, Oidium lactis and Dematium- 

 like forms. In the water conduits of the breweries a coherent 

 layer of Crenothrix was not infrequently found. 



In many cases it has been proved that water received a 

 very considerable contingent of its wort and beer organisms 

 in the reservoirs or conduits, and it may safely be asserted, as 

 the result of many years' experience, that brewery water is 

 most seriously contaminated in the brewery itself. 



Biological analyses of natural and artificial ice have shown 

 that in both, organisms can exist capable of developing in 

 wort and beer. Sarcina-like bacteria can also be introduced 

 along with ice into these li quids, and may develop freely in 

 them. In artificial ice, the inner snowy layer of the ice-block 

 appears to be particularly rich in micro-organisms. 



If large quantities of water are to be analysed, it is of the 

 utmost importance to take due care that real average samples 

 are obtained. 



Hansen gives the following method for the zymotechnical 

 analysis of air and water, a method based upon a long series 

 of comparative trials. 



The principle underlying it is as follows : For brewing 

 purposes it is only necessary to know whether the water and 

 the air contain germs capable of developing in wort and beer. 

 This cannot, as was formerly assumed, be ascertained by means 

 of the meat decoction peptone gelatine employed in hygienic 

 air and water analysis. The zymotechnologist has this great 

 advantage over the hygienist, that he is in a position to make 

 direct experiments with the same kind of liquid as that employed 

 in practice namely, wort. All disease germs that have hitherto 

 been shown with certainty to occur in beer are also capable of 

 developing in wort. Hansen's comparative investigations have 

 proved that the use of gelatines introduces great sources of error. 

 Thus, for instance, in a series of comparative experiments with 

 corresponding samples of water, the following numbers were 

 obtained : In Koch's nutrient gelatine 100, 222, 1,000, 750, 

 and 1,500 growths obtained from 1 c.c. of water ; in wort 



