64 PHYSICAL CHEMISTRY IN MEDICINE. 



playing a r61e, therefore, only when these substances 

 appear in the organism. 



Such catalyzers can act, as was first pointed out by 

 VAN'T HOFF, in two directions, depending upon the 

 relations existing between the substances originally present 

 and those formed. In this way, as has recently been 

 shown, amygdalin cannot only be split into amygdalic 

 nitrilglucoside and glucose under the influence of yeast 

 maltase, but also be formed synthetically from these two 

 substances with the help of the same enzyme. One and 

 the same enzyme can, according to conditions, accelerate 

 the one or the other homodrome antagonistic reaction. 

 In the animal organism the synthesis of glycogen from 

 dextrose and the splitting of glycogen into dextrose might 

 in part, at least, represent a simple antagonistic reaction 

 governed by a single enzyme; while the synthesis of 

 starch in plants and its diastatic splitting into glucose 

 or maltose represents a heterodrome antagonistic reaction 

 in which the synthesis has the upper hand by day and 

 the analysis by night. 



It is also possible, however, that two catalyzers may 

 act in such a way upon a homodrome antagonistic reac- 

 tion that the one accelerates the conversion of the system 

 in the one direction, while the other does it in the opposite 

 direction. This is the case when the two catalyses go 

 hand in hand with different equilibrium-points in the 

 two reactions that constitute the simple antagonistic 

 reaction. An example of this sort will be given later. 

 The deposition and solution of the calcium salts of the 

 bone represents a simple reversible reaction which, with 

 the aid of special cells, the osteoblasts and osteoclasts, 

 can, according to physiological needs, be divided, and 



