552 GENERAL PHYSIOLOGY 



motion of the atoms in the biogen molecule, and thereby give 

 greater opportunity for rearrangement and explosive decomposition ; 

 the augmentation of the processes under the influence of certain 

 stimuli needs no further explanation. Those cases of reactions 

 where there is a depression of dissimilation also scarcely need further 

 discussion, for all those stimuli that diminish the intramolecular 

 motion of the atoms in the biogen molecule, or hinder the re- 

 arrangement and combination of definite atoms in any way, such 

 as cold or narcotics, must evidently diminish the normal work of 

 the cell. But not all the performances of living substance are 

 associated with the dissimilatory phase of metabolism. Many 

 important ones go hand in hand with the assimilatory phase. 

 Hence, stimuli that excite assimilation, such as increased food, 

 will augment such performances, since they afford a greater 

 opportunity for the formation of new biogen masses; and, vice 

 versa, stimuli that depress assimilation will produce the opposite 

 effect. Those vital phenomena that are associated with assimila- 

 tion and are augmented by stimuli that excite this process, have 

 been greatly neglected by investigators in comparison with the 

 more evident phenomena associated with dissimilation, and they 

 deserve special consideration in the future. 



This idea of the action of stimuli does not imply that the energy 

 that is manifested in definite work as the result of a stimulation is 

 always derived directly and solely from the excitation or depression 

 of one or another link in the metabolic chain. According to our 

 idea, the satisfying of the free affinities of the residue of the 

 biogen molecule, i.e., its regeneration, follows directly its explosive 

 decomposition. Hence, under certain circumstances there is con- 

 tained in the reaction not only the energy set free by the decom- 

 position of the complex compounds, but also the energy that 

 becomes actual in the processes that result directly from the 

 decomposition, and the same is true of other cases of reactions. 

 Thus, all the elements of the energetics of the cell are extra- 

 ordinarily closely interwoven. This follows necessarily from the 

 facts of metabolism above discussed. The very great difficulty of 

 following in their details the more delicate transformations under- 

 gone by the energy in a given work, whether spontaneously or 

 upon stimulation, is evident ; and hence, with the extremely few 

 investigations that have been carried on in this field thus far, it 

 is at present impossible to determine with any certainty the 

 energetics of even the more evident performances of the cell, such 

 as the production of light or electricity and the evolution of 

 mechanical energy in the various kinds of movement. To study 

 in detail the extremely interesting history of the energy in the 

 various internal and external labours of the living cell will be one 

 of the most stimulating tasks of the physiology of the future. 



