Fatigue of Excitation and Fatigue of Depression etc 41 



in Experiment 29 or of lactic in Experiment 30 are permissible from 

 these three experiments by themselves. The cell states of the animals 

 so treated, though they are less active than their control, may repre- 

 sent actually an excitation by the drugs used, over an unknown nor- 

 mal proper to each individual. The only thing proved is the indivi- 

 dual variation. To prove anything definite there must be a wide 

 divergence from the normal general limits from broad experience in 

 at least a majority of sufficient experiments. 



It is the lack of this divergence from the normal average cell 

 state that appears conclusive in all the experiments at hand. If 

 sarcolactic acid produced the anatomical changes of activity (and 

 recovery from activity and senility), it would only be reasonable that 

 after the blood of fatigue is transferred to a normal dog, that animal 

 should show nearly the same degree of intensity of reaction after the 

 same time as the cells of the dog which did the work and received 

 the reactive stimulation. Or with complete willingness to make all 

 allowance for partial transference of the blood of fatigue, the reci- 

 pient, speaking roughly, should show one half or one third of the 

 mass effect. Experiments 18, 22 and 2 were animals doing their own 

 work in the treadmill, and their counts represent fairly the range of 

 severity of change belonging to that degree of cellular activity 

 (Compare Table 1, 1909 c). It will only be necessary to refer to one 

 point to show how they stand out by themselves in the counts, 

 namely, that over one half or nearly "one half of their cells are in 

 the groups of profound changes of upset of the nucleus plasma rela- 

 tion and of exhaustion. In short, they are advancing rapidly to 

 exhaustion. Comparing with these the adult dogs, Experiments 31. 

 33 and 39, after lactic acid, transfusion, and sarcolactic acid and 

 mono-potassium phosphate respectively, the difference is most striking. 

 Not only are the latter much less advanced in activity, but the cell 

 picture is that of an average elderly normal dog. For the stages of 

 upset just specified, which are the test of activity, the percentages 

 are not over 16°/ in the drug-treated animals as against 57° „ and li )M ,, 

 in Experiments 18 and 22 respectively. Even making allowance for 

 the number of senile cells in Experiments 31, 33 and 39, which were 



