EXAMINATION OF AIR AND WATEE. 49 



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

 the result of many years' experience, that brewery water 

 receives its most dangerous contaminations in the brewery 

 itself. 



Biological analyses of natural and artificial ice have shown 

 that in both sorts of ice organisms can exist capable of 

 developing in wort and beer. Sarcina-like bacteria can also be 

 introduced along with ice into these liquids and may develop 

 freely in them. 



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 gave the following method for the zymotechnical 

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

 comparative trials. 



The principle of this method of air and water analysis 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 leer. This cannot, as was formerly assumed, be 

 ascertained by means of the meat decoction peptone gelatine 

 employed in hygienic air and water analysis. The zymo- 

 technologist has this great advantage over the hygienist, that 

 lie 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 com- 

 parative investigations have proved beyond dispute 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 nutritive gelatine: 100, 222, 1000, 750, and 1500 

 growths were obtained from 1 c.cm. of water; in wort 0, 0, 6*6, 

 3, and 9 growths ; whereas, in beer, none of these water- 

 samples gave any growth. In another series, KOCH'S gelatine 

 gave for 1 c.cm. of water 222 growths, wort-gelatine 30 ; but 

 none of the flasks containing wort or beer, after infection with 

 the water, showed any development of organisms. Thus, only 

 very few of the great number of germs living in the water 

 developed in wort or beer. 



D 



