AIR AND WATER FOR MICRO-ORGANISMS. 115 



it had, in the course of years, also become customary 

 to employ the hygienic method, without examining whether 

 questions relating to brewing could be solved in this manner. 

 I do not intend to again enter into these disputes, as they 

 are no longer of interest. Moreover, during the last few 

 years my method has been adopted in several laboratories 

 in various countries. My object now is to give an account 

 of my treatises mentioned above, and with this I hope to 

 bring this work to a conclusion. 



According to Koch's method for the bacteriological 

 analysis of potable water, I cc. of the latter is mixed with 

 10 cc. of melted (at 30 C.) nutritive gelatine (meat decoction 

 peptone gelatine). This mixture is poured on to a plate, 

 and is protected against infection by means of a moist bell- 

 jar. Under certain circumstanq.es only 0*5 cc. or even only 

 one drop of the water is employed. The plates are kept 

 at the ordinary room-temperature, and are examined after 

 3-4 days. The number of vegetative specks developed is 

 calculated, for practical reasons, for I cc. of the water under 

 examination. 



When a brewer desires to have a bacteriological analysis 

 made of the water which he proposes to employ in his 

 brewery, the point to be determined is not which and how 

 many micro-organisms are present in the water, nor which 

 growths develop in gelatine or other solid substrata, with or 

 without meat extract peptone ; all this is of no interest in the 

 case under discussion, for neither the one nor the other of 

 these substances is employed in the brewery. The simple 

 question with which we have to deal is this : How does the 

 water behave with the wort and with the beer ; in what 

 degree are such micro-organisms present which are able to 

 develop in the above liqttids, and are there amongst them such 

 species which are capable of producing ill effects ? Briefly 

 stated, our analysis must be carried out as far as possible 

 under the conditions obtaining in the brewery ; we must, 



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