EXAMINATION OF WATER FOR MICRO-ORGANISMS 69 s 



wort to which J c.c. of water respectively was added to 

 represent in all 2*5 c.c. of water, and supposing only 

 4 of these 10 flasks became turbid, whilst the remaining 

 6 remained clear, the presumption would obviously be 

 that each of the 4 turbid flasks had been rendered 

 turbid by the multiplication of a single microbe intro- 

 duced in the water added. If this supposition be 

 granted, it follows that the 2 '5 c.c. of water employed 

 contained 4 microbes only capable of developing in the 

 malt-wort or 1'6 microbe per 1 c.c. Should all the 10 

 flasks have become turbid, it would of course prevent 

 any exact numerical deduction being made beyond the 

 obvious one that each J c.c. of water contained at least 

 1 developable microbe. 



In this case, however, the 15 flasks, into each of 

 which one drop of water had been introduced, would 

 come into requisition, as in all probability only some of 

 these would have become turbid, and in that case a 

 numerical estimate of the developable micro-organisms 

 in a given volume of water could be made on the same 

 principles as indicated above. Of course, the exact 

 volumes of water employed in this method of examin- 

 ation will have to be varied according to circumstances. 

 A microscopic examination should also be made of 

 the contents of those flasks which have become turbid, 

 and if necessary further experiments conducted to 

 ascertain whether the particular micro-organisms thus 

 discovered may exert a deleterious effect on the wort 

 or beer. 



A large number of investigations have been made 

 by Hansen and his pupils to compare the numbers of 

 bacteria in brewing waters revealed by ordinary 

 gelatine-peptone and wort-gelatine plates respectively, 

 as well as by means of the wort and beer method 

 described above. 



