38 BACTERIOLOGY. 



media in which the exercise of this function is not re- 

 quired may lead to its marked deterioration, while pro- 

 longed cultivation under conditions demanding it may 

 result in its accentuation. 



The addition of carbohydrates and of glycerine to 

 culture-media interferes with production of the proteo- 

 lytic enzyme by many species of bacteria, as shown by 

 Auerbach. 1 



Diastatic enzymes convert starch into sugar. This 

 function 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 2 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. 

 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 altera- 

 tion is quite common in association with an acid reac- 

 tion, but in such instances it is not always certain that 

 the coagulation has not been induced by the acid formed. 

 Gorini 3 found that cultures of bacillus prodigiosus, ster- 



1 Auerbach : Archiv fur Hygiene, Bd. xxxi. p. 311. 



2 Fermi : Archiv fur Hygiene, Bd. xi., and Centralblatt fur Bacte- 

 riologie, Bd. xii. 



3 Gorini : Centralblatt fur Bacteriologie, Bd. xii. p. 666. 



