Fatigue of Excitation and Fatigue of Depression etc. 49 



function at all, it is obviously a characteristic of the nerve cell to 

 struggle on through until its limit of capacity is reached. 



We must recognize for the nerve cell with Verworn, therefore, 

 fatigue of excitation and fatigue of depression, of different genesis 

 but identical effect. 



It may be said in explanation of the terms just used that one 

 quickly becomes impressed with the need of an exact terminology to 

 express this difference in the genesis of the kinds of fatigue. Ver- 

 worn himself suggested that the phenomena of depression which re- 

 sult from the consumption of necessary substances be called exhaustion, 

 and those that result from the accumulation of waste products fatigue. 

 There are, however, certain objections in regard to the aptness of 

 these designatory terms. In the first place, their significance is not 

 self -apparent. By common usage, fatigue and exhaustion rather re- 

 present different grades of the same state, fatigue being preliminary 

 and only less marked than the climax of exhaustion. In the second 

 place, the use of the term exhaustion to represent the consumption 

 of necessary substances does not recognize the different grades from 

 zero to a maximum in that consumption. Even to an advanced state 

 the cell, though affected, is entirely capable, and practically there is 

 frequently advantage in a term which conveys this idea, as the word 

 exhaustion does not. 



The states attended by consumption of substance have throughout 

 their cause in excitatory stimulation, while depression is the common 

 term to express interference with activity. To bring out this 

 distinction, the terms "fatigue of excitation" and "exhaustion of exci- 

 tation", as opposed to "fatigue of depression"', are suggested. These 

 terms preserve the more common use of the words fatigue and 

 exhaustion, express grades of the first condition when it is important 

 to express grades, state the genesis and are less cumbersome than 

 the circumlocution that would otherwise be necessary. Cytologically 

 there can be no exhaustion of depression, though functionally it 

 amounts to that, for there appears no lack of primary materials for 

 synthesis.. In fact, certain of these are increased in depression 

 (Dolley, 1913b, yolk material in the plasma, nucleolar substance of 



Internationale Monatsschrift f. Anat. u. Pays. XXXI. 



