ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 685 



Experiment 7. (June 1886.) Duration 5 hours. 

 Primary colonies = 35 



Secondary „ = 981,792 

 «= 14-8 

 Period of development = 20-3 minutes. 



It may be noted that either the period of development of each brood 

 varied considerably, or the method of experimentation or of calculation 

 was at fault. 



Analysis of Water used for Brewing as regards Micro-organisms.* 



The examination of drinking-water, remarks Dr. E. C. Hansen, is 



made by means of Koch's plate-cultivation method, by means of meat- 

 peptone gelatin; and this method is also employed in zymotechnical 

 laboratories. But for the analysis of water used in brewing another 

 method must be adopted. The question at issue is not so much to find 

 out what and how many micro-organisms exist in the water, nor what 

 will develope in gelatin with or without the addition of meat and 

 peptone, but rather how the water behaves towards the wort and the 

 beer, to what degree it is rich in micro-organisms which can develope 

 in these media, and if among them there be any kinds capable of exerting 

 a detrimental action. The analysis, in short, must be carried out under 

 conditions obtaining in the brewery itself. 



The nutrient solutions, the beer and the wort, are placed in small 

 flasks plugged with cotton-wool. Each flask, fifteen filled with beer and 

 fifteen with wort, was inoculated with • 02 cm. of cold tap-water. The 

 water was inserted by means of a pipette, the upper end of which was 

 fixed to a rubber tube, in order to prevent any germs entering from the 

 air. The number of drops was regulated by means of a stopcock. It 

 need hardly be remarked that the apparatus and the media were carefully 

 sterilized. Also, the amount of water placed in each bulb was accurately 

 measured, in order that the result could be calculated up to 1 ccm. 



For the sake of comparison, an analysis was made by Koch's method 

 from the same water, and also on another plate ; but instead of meat- 

 peptone gelatin, wort-gelatin (wort with about 5 per cent, gelatin) was 

 used here. The cultivations were placed in a thermostat at 24°-25° C, 

 and the experiment was suspended after fourteen days. None of the 

 beer- or wort-flasks contained a trace of vegetation. In Koch's gelatin 

 there were 111 spots of vegetation, that is 222 for 1 ccm. water ; all 

 contained bacteria, but only a few fluidified the gelatin. The wort 

 gelatin showed fifteen vegetations, or thirty to 1 ccm. water. Other 

 experiments gave analogous results, and on the whole showed that while 

 the hygienic method put the total too high, the estimates from the wort- 

 gelatin cultivations were too low, and that very few of the bacteria 

 present in the water had any effect on the wort, and none at all on the 

 beer. Yet, when both of these fluids were much diluted, they lost their 

 original power of resistance, but then of course they were neither what 

 is usually understood by beer and wort. 



Some further experiments established the fact that bacteria from 

 water, even though introduced in large quantity, were unable to develope 

 in beer, but hyphomycetes of water occasionally did so. 



Based on these observations, the author made an analysis of the 



* Centralbl. f. Backteriol. u. Parasitenk, iii. (1888) pp. 377-9, from Zeitschr. f. d. 

 Gesell. Brauwesen, 1888, No. 1. 



