EXAMINATION OF WATER FOR MICRO-ORGANISMS 71 



of primary importance to detect, do not develop at all 

 in the gelatine media, and, if the latter only were 

 employed, would therefore be entirely overlooked. 

 Hansen states that he has frequently found that many 

 saccharomycetes and other alcoholic ferments are in 

 such a weakened condition in air, earth, and water that 

 they are quite incapable of growing in gelatine, or, if 

 they grow at all, develop very feebly, whilst when in- 

 troduced into wort and beer they grow most luxu- 

 riantly. 



In order to ascertain the value of a water for brew- 

 ing purposes, it is of great importance to note whether 

 the development of the organisms is slow or rapid. If 

 the organisms present only commence to develop four 

 or five days after inoculation, it may be taken that 

 when exposed to the far more unfavourable conditions 

 prevalent during brewing operations they would only de- 

 velop with great difficulty, or possibly not at all. For 

 in the experimental flasks they are present under very 

 favourable conditions, no competing forms in the shape 

 of the yeast cells disturbing their development, whilst the 

 temperature, at any rate for the majority of the forms, 

 is very suitable for their growth and multiplication. 



Holm states as a result of a large number of investi- 

 gations that, if, at the end of seven days, no growths 

 make their appearance in the wort or beer, the exami- 

 nation may, for practical purposes, be closed, although 

 it is quite possible that growths may yet develop 

 subsequently. To still further simplify the investi- 

 gation, it is proposed to employ sterilised wort only, 

 as all organisms which develop in beer will also develop 

 in the wort. In spite of the frequent presence of 

 moulds, Holm statas that they are only of secondary 

 importance. The most dangerous organisms are the 

 bacteria, and more especially those which are present 



