84 GENERAL BIOLOGY 



removed as soon as formed. Some of these enzymes 

 are reversible, splitting and synthesizing the same 

 substance, as conditions differ. In these processes, 

 enzymes seem to follow the same " law of mass 

 action " as well as the equations of reaction- velocity 

 in relation to temperature that have been worked 

 out in inorganic chemistry. 



Within the cell, through the aid of enzymes there 

 present, analysis and synthesis may take place 

 side by side, and by a series of such changes, oxida- 

 tion following reduction in continuous sequence, the 

 most complex molecules may be built up, the energy 

 of one disruptive process being utilized to combine 

 the components into a molecule of a higher order. 

 Oxidizing enzymes or " oxidases " seem to be 

 present in all protoplasm, and owing to their presence 

 the necessary oxidations take place in the organism 

 very rapidly at a comparatively low temperature. 

 The seat of these oxidations, and hence of the oxi- 

 dative enzymes, appears to be in the nucleus. 



A distinction was formerly made between the 

 so-called " unorganized ferments," such as pepsin, 

 and the " organized ferments," such as the active 

 principle of yeast, which was supposed to require 

 the presence of a living cell in order to work. It 

 has been found possible, however, to crush all life 

 out of the yeast cells and, by filtering the extract, to 

 get a solution which is as active a fermentative 

 agent as living yeast. The distinction between the 

 two sorts of enzymes then falls to the ground. 

 The only difference seems to be that some enzymes 



