ZYMOLOGY — FERMENTS AND FERMENTATIONS 217 



ment takes up the moisture and again gives it up is as yet not explained. 

 Ferments are variously influenced in their activities by physical and chem- 

 ical agents. It is known that certain chemicals which are not normally 

 present in living cells or organisms and which are not component parts 

 thereof, appear to have a stimulating effect upon the life processes of these 

 cells or organisms. For example the spores of Aspergillus repens will not 

 germinate in pure water or in inorganic nutrient solutions, or even in 

 peptone solutions, unless some inorganic salt, such as saltpeter, is added. 

 Recent tests made show that radium exerts a very marked influence upon 

 plant growth as well as upon the functional activities of animal cells and 

 organs. 



Minute doses of certain toxic agents have a stimulating effect upon the 

 vital processes of lower as well as higher organisms. 1-500,000 parts of 

 mercuric chloride, or the merest trace of iodine, of potassium iodide, of 

 chromic acid or of salicylic acid, have a very beneficial effect upon pro- 

 cesses of fermentation. In a general way ferments are less susceptible 

 to the influence of poisonous agents than are the microbes or other organ- 

 isms which form the enzymes. It is possible through the judicious use of 

 certain antiseptics to kill bacteria and other objectionable organisms with- 

 out in any way hindering the fermentation induced by associated organ- 

 isms. This discovery proved of great value in experimenting with and 

 isolating enzymes. The following substances may be used for this pur- 

 pose — alcohol, ether, etheral oils, dilute acids, sahcyhc acid, thymol, 

 chloroform, calomel, corrosive sublimate, etc. Many of these germ 

 destroying agents are however not without some checking influence upon 

 the action of the ferments themselves, notably salicylic acid, phenol, 

 thymol and chloroform. Toluol appears to have the least injurious 

 effect upon enzymes. 



Ferments influence each other. Pepsin inhibits the action of nearly 

 all other ferments, notably that of trypsin and of diastase. Trypsin 

 again destroys zymase. Pepsin has however only a slight check upon 

 lactic acid fermentation. Weak acids and occasionally also weak alkalies, 

 have the power of converting the inactive proferments into active fer- 

 ments, which substances Oppenheimer designates as zymoplastic. Other 

 agents as warmth, dilute acids and alkahes, increase the activity of fer- 

 ments. Still other agencies, as cold, most alkalies, alcohol, etc., inhibit 

 their action while the socalled zymolytic agents (strong acids, heat, etc.) 

 kill them. Other more specific properties of ferments wfll be given under 

 the description of the ferments themselves. The foUowing classifica- 

 tion of the more common ferments wiU make dear their relationship 

 and will also serve as an introduction to the specific descriptions which 

 follow: 



