258 THEORETICAL CONSIDERATIONS 



oughly worked out theoretical conceptions of protoplasm is the 

 *' biogen hypothesis" of Verworn,^' " and the details of this hypothesis 

 are sufficiently tangible to be of service in an attempt to form some 

 provisional conception as to how radium rays, or any other stimuli, 

 produce their effects. I will first briefly state some of the funda- 

 mental notions of the biogen hypothesis and their bearing upon radium 

 stimulus, and then, in a similar manner, some of the facts concerning 

 a few physiological processes, made known by recent investigation. 



According to Verworn's conception, "The metabolism of living 

 substance, in last analysis, depends upon the continual destruction 

 and the continual reconstruction of a very labile chemical compound." 

 This " hypothetical compound, because of its fundamental relation 

 to the genesis of life-processes," Verworn- designates* as " biogen," 

 and, since in different forms of living substance there doubtless 

 occur very different compounds of this sort, he designates " the entire 

 group of them in a chemical sense as the group of the ' biogens,' " 

 and proposes the term " biogen molecule " to supplant that of " living 

 protein molecule " of Pfliiger. The biogen is designated * as a 

 "most highly complex, labile compound that develops at an inter- 

 mediate point in metabolism, and by its construction and destruction 

 comprehends the sum total of the processes of metabolism." It is 

 not a protein body, nor would the author call it a living protein. It 

 is not alive, for a molecule cannot be alive. 



The essence of metabolism, then, is the construction and destruc- 

 tion of biogen molecules, and, under normal conditions of equilibrium 



Construction ^ , , • r , • 



fs^ — 7^ = I. On the basis of this hypothesis, " the irritabilitv 



Destruction j tr ^ j 



of living substance depends upon the lability of the biogen molecule." 

 " In metabolism as a whole two different series of processes are 

 to be distinguished: 'functional metabolism,' in which the absolute 

 number of biogen molecules remains unaltered and only certain nitro- 

 gen-free groups are involved in functional destruction and restorative 

 construction ; and ' cytoplastic metabolism,' which governs the abso- 

 lute number of biogen molecules, and thereby the phenomena of 

 growth, propagation, development, atrophy, regeneration, etc., since 

 it extends over the destruction and reconstruction of the entire 

 molecule. In case of a disturbance of their metabolic equilibrium, a 

 compensatory self-regulation underlies both series of processes, and 



* Loc. cit., p. 25. 



