136 PRODUCTS OF VITAL ACTIVITY. 



laboratory of the Hygienic Institute of Munich (1891), the following 

 results were obtained : 



The enzymes were not obtained pure, and their isolation from 

 other proteids present in the cultures was found to be attended with 

 great difficulties, but their ferment action was studied and was found 

 to be influenced by various conditions. 



All were destroyed by a temperature of 70 C. , but the enzymes 

 produced by various liquefying bacteria differed considerably as to 

 the temperature which they were able to withstand. Some were de- 

 stroyed by a temperature of 50 to 55 C. Bacillus megatherium, 

 Bacillus ramosus, Staphylococcus pyogenes aureus ; some by a tem- 

 perature of 55 to 60 C. Bacillus subtilis, Bacillus pyocyaneus, Ba- 

 cillus fluorescens liquefacieris, Sarcina aurantiaca; some by 65 to 

 70 C. Bacillus anthracis, Spirillum choleras Asiatics, Spirillum of 

 Finkler and Prioi\ Spirillum tyrogenum. 



These enzymes, like the previously known pepsin, trypsin, and 

 invertin, do not dialyze. 



Only a few of these bacteria enzymes acted upon fibrin, and no 

 action was observed upon casein or upon egg albumen. 



Their liquefying action upon gelatin was prevented by the action 

 of sulphuric acid, and to a less degree by nitric acid, but was not in- 

 terfered with by acetic acid. 



The liquefying bacteria, as a rule, only produce enzymes when 

 cultivated in a medium containing albumen. 



These enzymes are not produced by a solution of the protoplasm 

 of dead bacterial cells, but are a product of the vital activity of liv- 

 ing cells. 



Among the numerous liquefying bacteria known to bacteriolo- 

 gists we may mention the following species as deserving the student's 

 special attention: Staphylococcus pyogenes aureus, Staphylococcus 

 pyogenes albus, Sarcina lutea, Sarcina aurantiaca, Bacillus anthra- 

 cis, Bacillus pyocyaneus, Bacillus subtilis, Bacillus indicus, Bacillus 

 prodigiosus, Spirillum cholerse Asiaticse, Spirillum of Finkler and 

 Prior, Proteus vulgaris. 



Fermentation. The fermentation produced by various species of 

 bacteria in culture solutions containing saccharose, glucose, or lac- 

 tose constitutes a valuable character for the differentiation of species. 

 While some bacteria give rise to fermentation in solutions contain- 

 ing either of the carbohydrates above mentioned, others break up lac- 

 tose, but have no effect upon glucose or saccharose, and others again 

 are without any ferment action. The gases evolved are chiefly car- 

 bon dioxide and hydrogen. Ferment action may be tested by adding 

 one to two per cent of glucose to a solid culture medium preferably 

 agar-agar. This is liquefied by heat in the test tube containing it and 



