584 VITAL ACTIONS OF THE LOWER FUNGI. 



Action of be mentioned the reaction of the medium. Excess of 

 alkali is injurious to most of the ferments. A slight 

 degree of acidity is very well home hy some ferments- 

 diastase, invertin and their action is, in fact, increased 

 hy a slightly acid reaction; the pepsin-like ferments 

 absolutely require a certain excess of acid for the develop- 

 ment of their action. Other ferments, such as emulsin, 

 are hindered in their action even hy '15 per thousand of 

 hydrochloric acid (Falk*). Larger amounts of acid are 

 always injurious. The salts of the heavy metals, and 

 other substances which precipitate albumen, act of course 



Carbolic acid, after the manner of poisons. Carbolic acid interferes 

 with the fermentative action of emulsin and ptyalin; 

 other ferments, and more especially diastase, are, on the 

 contrary, scarcely affected; according to Kjeldahl (loc. 

 cit.) the addition of '2 and '4 per cent, causes a scarcely 

 noticeable diminution. On the contrary, on the addition 

 of '03 per cent, of salicylic acid a marked diminution of 

 the diastatic effect is observed, and on the adition of '1 

 per cent, the action entirely ceases. Peroxide of hydro- 

 gen, which hinders all the fermentations dependent on 

 the presence of living organisms (Bert and Regnardf), 

 and also hydrocyanic acid, chloroform, ether, benzole, 

 and oil of turpentine, scarcely injure the isolated ferment 

 at all ; and, for example, by the salts of ammonia (up 

 to 10 per cent.) and by alkaloids, such as veratrin and 

 curare, the inversion of cane-sugar is much favoured. 



Most of the ferments act only on a certain class of 

 chemical bodies; it is only combinations which are 

 closely allied to each other which are, as a rule, broken 

 up by the same ferments. Thus emulsin splits up 

 several glucosides; but, on the other hand, invertin, for 

 example, does not act on dextrine, maltose, or starch ; 

 nor does diastase act on cane-sugar, or on glucosides. 

 If several chemical ferments are present in the same 

 solution they may destroy each other ; thus pepsin 

 digests trypsin and ptyalin. This, however, does 

 not hold good in the case of all ferments, for diastase 



* Talk, Virckow's Arch., vol. 93. 



t P. Bert und Eegnard, Compt. rend., vol. 94. 



