THEORETICAL CONSIDERATIONS 259 



the biogen molecule offers a simple mechanical explanation for indi- 

 vidual cases of this sort. . . ." 



Analyzing the phenomena of stimulation on the basis of his 

 hypothesis, Verworn^ says:* "Irritability is the capacity of living 

 substance to react to a stimulus by an acceleration of the metabolism 

 of biogens." Both the dissimilatory and the assimilatory phases of 

 metabolism may be stimulated. The degree of dissimilatory stimu- 

 lation is, for equally intense stimuli, dependent upon the following 

 factors : 



(a) The degree of lability of the biogen molecule. 



{d) The rapidity of the process of restitution after the functional 

 destruction of the biogen. 



(c) The absolute number of biogen molecules present. 



(d) The conditions for the propagation of the effects of stimula- 

 tion. 



A dissimilatory stimulation, or depression, may therefore be 

 brought about by influencing any one of these individual factors. 



On the other hand, the degree of assimilatory irritability is de- 

 pendent upon : 



(«) The quality of the raw materials available for nutrition. 



(3) The means for working up the raw material into a suitable 

 form of elaborated matter. 



(c) The quantity of the suitable elaborated matter. 



(^d) The rapidity of the transformation of the elaborated matter 

 from the reserve depots into the biogen molecules. 



An assimilatory irritability or depression may arise through in- 

 fluencing each of these individual conditions. 



Radium rays, by acting on any one of the eight factors enumer- 

 ated above, may therefore excite or depress processes of either 

 assimilation or dissimilation. NowVerworn^ has earlier explained! 

 that the atoms of his hypothetical biogen molecule are in active 

 vibration. "As a result of this, certain atoms come occasionally into 

 the sphere of attraction of others, and, becoming united with them 

 into a more fixed combination, separate off as an independent 

 molecule. In this way the spontaneous dissimilation of the biogen 

 molecule results." The residues of biogen molecules thus formed 

 may combine with constituents of the food, and thus be rebuilt into 



* Loc. cit., p. 89. 

 t Loc. cit., p. 489. 



