Fatigue of Excitation and Fatigue of Depression e1r. 43 



plane. So far as there is any difference, one of the normals, Experi- 

 ment 13, shows probably the highest degree of activity. The other 

 normal, Experiment 14, is, if anything, more advanced than the lactic 

 acid puppy, which is the least affected of the group, and the three 

 transfusions appear to come between these extremes. There is no 

 weighty difference between Experiments 23 and 24 of transfusion and 

 their operative control, Experiment 25. There was no shock, as the 

 normal controls indicate, and, throughout, the results correspond to 

 the degree of operative stimulation, for the anesthetic was light, 

 the manipulation superficial and the blood was rapidly removed 

 and immediately restored. Finally, consideration of the points 

 brought out leads to the same conclusion in the case of the three 

 remaining Experiments 28, 29 and 30. The evidence is uniformly 

 negative. 



To sum up, the treated animals not only fail to exceed the 

 limits of their various controls but they do not come out of the nor- 

 mal limits obtained. Neither the blood of fatigue nor the artificial 

 products accepted as fatigue substances excite the nerve cell to the 

 changes peculiar to function. They are thus thoroughly eliminated 

 by experimental test as a causative factor. On rational grounds this 

 was to be expected. Such substances are the result, a by-product of 

 function, and a full appreciation of the significance of the changes 

 described by Hodge and his successors as the changes of actual work 

 could have assigned them only a secondary place. Their essential 

 effect is to „depress" cell activity, to inhibit it, not to excite it. If 

 at the moment there arises a question in regard to the initial exci- 

 tation, it will be shown to depend upon the two-fold nature of certain 

 stimuli. If at the time of making these experiments I had known 

 that waste products could go so far as to produce anatomical depres- 

 sion, the labor of making them would have been saved. That they 

 do this has since been demonstrated (Dolley, 1913b). This finding 

 confirms the results of physiological experimentation on the action of 

 such substances (Lee, 1907a and b) and by itself gives them their 

 proper place in relation to activity. 



