Fatigue of Excitation and Fatigue of Depression etc. 59 



as the cause of the changes described as peculiar to function in the 

 nerve cell. Instead, if administered in sufficient amount and over 

 sufficient time, they produce anatomical changes of depression, which 

 disposes of them in harmony with physiological knowledge. 



Activity and depression, which are held to be merely quantitative 

 opposites in the physiological sense by Verworn, are also quantitative 

 opposites as regards their reciprocal mass relations. Activity finally 

 results in an upset of the nucleus-plasma relation in favor of the 

 cytoplasm, depression produces an upset in favor of the nucleus. The 

 whole possible range of the vital activities of the nerve cell is in 

 these phases or in their combination fully accounted for anatomically 

 in harmony with the possibilities of stimuli. From anatomical analysis, 

 stimuli conform to the recognized physiological division into pure 

 excitants, pure depressants and an intermediate group which first 

 excite then later depress. 



There is a separate anatomical basis both for fatigue of excit- 

 ation and for fatigue of depression. The former is the organic and 

 substantive fatigue of the dissipation of energy in normal function, 

 the latter results from the by-products of this function. Each may 

 lead to a total cessation of function. 



The outward phenomena of these two forms of fatigue must be 

 in the main identical. In exhaustive activity, chromatin formation 

 fails, in depression its formation is inhibited — in both cases the 

 phenomena of function disturbed by fatigue depend upon the state of the 

 same substance, which in both ultimately reaches the same state of 

 total deficiency. For the same reason, irritability is progressively 

 lowered in both prior to the total cessation of function. 



Between the two opposite phases, activity and depression, activity, 

 incited by excitatory stimulation and ending in organic fatigue, is 

 primordial and plays the vaster rôle in health and disease. The 

 neglect of this is conducive to error as exemplified in the speculative 

 idea of the inexhaustibility of the nerve cell. 



Any nerve cell is capable of absolute immediate exhaustion, 

 without interference with its power of recuperation, provided ex- 

 citation be continued sufficiently long. 



