1896.] MICROSCOPICAL JOURNAL. 121 



to a bacterial ferment [Pasteur's Mycodenna aeeti), etc. 

 Subsequent researches show that alcoholic fermentation 

 may be induced by several species of torula, and even by 

 certain bacteria; while the number of bacterial ferments 

 now known to science is very considerable and is con- 

 stantly being added to. Among the most important of 

 these we may mention the Bacillus acidi lactici, which is 

 the usual cause of the acid fermentation of milk; the 

 various anaerobic bacilli which gives rise to the formation 

 of butyric acid in solutions containing starch, dextrin 

 sugar, or salts of lactic acid; the bacteria which cause the 

 alkaline fermentation of urine; those which produce marsh 

 gas by the fermentation of cellulose; those which effect 

 the decomposition of albumen, with an evolution of hy- 

 drosulphuric acid; those which give rise to the putrefac- 

 tive decomposition of organic material, the number of 

 which is very large; the bacteria in the soil which reduce 

 nitrates with liberation of ammonia and free nitrogen, 

 and those which oxidize ammonia. The study of these 

 bacterial ferments is still being vigorously prosecuted, 

 and practical results of importance in agriculture and the 

 arts have already been attained. In the future we may 

 look for numerous additions to these practical applica- 

 tions of our knowledge. The use of pure cultures for 

 producing useful fermentations must give the best re- 

 sult with the least liability to loss of material from the 

 presence of undesirable species. It is known that the 

 flavor of butter and of different kinds of cheese is due to 

 various bacterial ferments, and there is good reason to 

 suppose that a better product and greater uniformity 

 would be attained by the use of pure cultures of the 

 species upon which special flavors depend. I under- 

 stand that in this country quite a number of dairies are 

 now using pure cultures of a certain bacillus (Bacillus 41 

 of Conn) for giving flavor to their product. It is prob- 



