FERMENTS, ENZYMES, TOXINS AND PTOMAINS 47 



tions of bacteria that is easily disturbed by external condi- 

 tions, for instance, long-continued cultivation on media 

 in which the exercise of this function is not required may 

 lead to its marked deterioration, while prolonged cultivation 

 under conditions demanding it may result in its accentua- 

 tion. 



The addition of carbohydrates and of glycerine to culture- 

 media interferes with production of the proteolytic enzyme 

 by many species of bacteria, as shown by Auerbach.^ 



Diastolic enzymes convert starch into sugar. This func- 

 tion is best studied on media containing starch, as potato 

 infusion or solutions of starch. By appropriate tests the 

 intermediate steps in the conversion of the starch into 

 sugar may be traced by testing a portion of the culture- 

 medium from time to time. Fermi^ found this function 

 in a -large number of bacteria studied, especially in organisms 

 of the subtilis group and in the microspira of the cholera 

 group. 



Inverting enzymes convert saccharose into dextrose and 

 levulose. These enzymes are produced by comparatively 

 few bacteria. Fermi found this function manifested by 

 bacillus megatherium, pseudomonas fluorescens, bacillus 

 vulgaris, microspira comma, microspira Metchnikovi, and 

 others. 



Coagulating enzymes are those which coagulate milk. 

 Rennet may be taken as the typical form. This alteration 

 is quite common in association with an acid reaction, but 

 in such instances it is not always certain that the coagulation 

 has not been induced by the acid formed. Gorini' found 



• Archiv filr Hygiene, Bd. xxxi, p. 311. 



^ Ibid., Bd. xi, and Centralblatt filr Baoteriologie, Bd. xii. 



' Centralblatt fiir Bacteriologie, Bd. xii, p. 666, ' 



