AIR AND WATER FOR MICRO-ORGANISMS. 119 



wort in the remaining 13 flasks, and the beer in all the 15 

 flasks, were still bright after 15 days, and in none of these 

 was there a sign of growth. The number of growths calcu- 

 lated for i cc. of the water was, therefore, 6 6 in the case of 

 the wort flasks, whilst it was 1000 for Koch's gelatine, and 34 

 for wort gelatine. As in the first series, all the drops sown on 

 pure gelatine developed growths. The micro-organisms found 

 were the same as in the first series. 



Some analyses which were made in September, October, 

 and November, 1887, and which were carried out under my 

 supervision by Messrs. Karneef, Kukla, Terry, and Wich- 

 mann, also yielded, in the main, the same result. 



It will be seen from all these experiments that the 

 hygienic method always gives too high a result, and that the 

 employment of wort gelatine is equally unsatisfactory. 

 Whilst no growths were obtained in the beer, and in the case 

 of wort the numbers obtained in different experiments were 

 o, o, 6 *6, 3, and 9, calculated on i cc. of the water, those 

 representing the growths in Koch's nutrient gelatine obtained 

 under otherwise similar conditions and for the same samples 

 of water were 100, 222, 1000, 750, and in one case even 1500. 



It is unnecessary to point out that the last numbers must 

 be regarded as valueless for brewery purposes. The analysis 

 is somewhat more satisfactory when wort gelatine is em- 

 ployed instead of meat extract peptone gelatine, but even in 

 this case the numbers obtained are too high, and give no 

 serviceable information. The majority of the bacteria which 

 developed in the gelatine were unable to grow either in the beer or 

 in tfie wort, and are, consequently ', of no importance for our 

 purpose. 



For the sake of comparison, all the cultures in the above 

 series of experiments were exposed to the same temperature 

 namely, 24-25 C. It is customary, however, in the 

 hygienic method to expose the cultures to the ordinary room- 

 temperature, and to examine them after three or four days. 



