AIR AND WATER FOR MICRO-ORGANISMS. 129 



fluctuations at different times of the year, and even at different 

 hours of the day ; and where, as in most breweries, it is 

 pumped into large tanks, its condition will also depend 

 largely upon whether the sample has been taken shortly 

 before or after the tank has been cleaned. Consequently, if 

 we desire any more accurate knowledge of the condition of a 

 water, it is necessary to carry out a large number of analyses 

 which must extend over a considerable period of time. 



My zymotechnic investigations on the micro-organisms of 

 air and water were carried out with special reference to the 

 conditions obtaining in low-fermentation breweries, but in 

 the main the results will also apply to high-fermentation 

 breweries. 



Since my investigations on brewing water were published 

 in 1887-89, several treatises on the same subject, and based 

 on my method, have appeared in various journals ; amongst 

 the latter may be mentioned Holm's " Analyses biologiques 

 et zymotechniques de Teau destinee aux brasseries," in the 

 * Compte-rendu des travaux du laboratoire de Carlsberg/ 

 3 vol. 2 livr., 1892. There is, indeed, now scarcely a zymo- 

 technologist who would recommend the employment of meat 

 extract and peptone gelatine for the analysis of water when 

 the question to be decided is whether it is suitable or not for 

 brewery purposes. My work referred to has thus far, 

 therefore, served its purpose.* 



* After the above had been for some considerable time in the hands of the 

 printer, Dr. Wichmann's "Biologische Untersuchungen des Wassers fur Brauerei- 

 zwecke" appeared in the ' Mitteilungen der oesterr. Versuchs-Station, V. Heft,' 

 Vienna, 1892. Wichmann points out the importance of noting the time when 

 the decomposition of the test liquid commences. In my first publication in 1888 

 this factor was not introduced in the analysis, this was, however, done sub- 

 sequently. Statements to this effect occur not only in my treatise mentioned 

 above, but likewise in Jorgensen's ' Micro-organisms and fermentation,' also 

 in Holm's treatise mentioned above. Thus the same idea occurred to Dr. 

 Wichmann as to myself, and he likewise worked it out independently. I gladly 

 take this opportunity to draw attention to his meritorious investigations. 



K 



