INTRODUCTION. 9 



organic origin which are products of the chemical work within 

 the cell, and which, after they are separated from the cell, are 

 capable in the smallest quantities of causing a decomposition or 

 splitting in very considerable quantities of other substances with- 

 out entering into combination with the decomposed body or with 

 any of its products of splitting or decomposition. Such ferments 

 are, for example, the diastase of malt and the ferments secreted by 

 the different glands participating in the process of digestion. 

 These non-organized or formless ferments are generally called, ac- 

 cording to KUHNE, enzymes. 



A ferment in a more restricted sense is therefore a living being, 

 while an enzyme is a product of chemical processes in the cell, a 

 product which has an individuality even without the cell, and 

 which may be active when separated from the cell. The splitting 

 of glucose or invert-sugar into carbon dioxide and alcohol by fer- 

 mentation is a fermentative process closely connected with the life 

 of the yeast. The inversion of cane-sugar is, on the contrary, an 

 enzymotic process caused by one of the bodies or mixture of bodies 

 formed by the living ferment, which can be severed from this fer- 

 ment, and still remains active even after the death of the latter. 

 Consequently ferments and enzymes are capable of manifesting a 

 different behavior towards certain chemical reagents. Thus there 

 exist a number of substances, among which we may mention arse- 

 nious acid, phenol, salicylic acid, boracic acid, chloroform, ether, and 

 others, which in certain concentration kill ferments, but which do 

 not noticeably impair the action of the enzymes. 



It is doubtful, indeed highly improbable, whether it has been 

 possible up to the present time to isolate any enzyme in a pure state. 

 Therefore the nature of the enzymes and their elementary compo- 

 sition is unknown. Such as have been obtained thus far appear to 

 be nitrogenized and to be similar in some degree to albuminous 

 bodies. They may be extracted from the tissues by means of water 

 or glycerin, especially by the latter, which forms very stable solu- 

 tions and which, consequently, serves as a means of extraction of 

 the enzymes. The enzymes, generally speaking, do not appear to 

 be diffusible, they decompose hydrogen peroxide and are precipi- 

 tated with other substances when these are in a finely-divided state. 

 This property has also often been taken advantage of in the prepa- 



