THE ORIGIN OF THE HUMAN SOUL 229 



imagination, therefore, involves the destruction of a consider- 

 able amount of the cortical substance, and results in temporary 

 incapacitation or paralysis of the imagination, which must 

 then be compensated by a process of repair in the cortical 

 neurons, before the imagination can resume its normal mode of 

 functioning. Brain-fag, then, is due to the activity of the 

 imagination rather than that of the intellect. That such is 

 the case appears from the fact that after the initial exertion, 

 which results from the imagination being forced to assemble 

 an appropriate and systematized display of illustrative 

 imagery as subject-matter for the contemplation of the intel- 

 lect, the latter is henceforth enabled to proceed with ease along 

 the path of a given science, its further progress being smooth 

 and unhampered. Once the preliminary work imposed upon 

 the imagination is finished, the sense of effort ceases and intel- 

 lectual investigation and study may subsequently reach the 

 highest degrees of concentration and intensity, without involv- 

 ing corresponding degrees of fatigue or depression on the part 

 of the cerebral imagination, just as, conversely speaking, the 

 activity of the cerebral imagination may reach degrees of in- 

 tensity extreme enough to induce brain-fag in psychic opera- 

 tions wherein the concomitant intellectual activity is reduced 

 to a minimum, e.g., in the task of memorizing a poem, or reci- 

 tation. Here, in the all but complete absence of intellectual 

 activity, the same fatigue results as that induced by a pro- 

 longed period of analytic study or investigation, in which 

 imaginative activity and rational thinking are concomitant. 

 The point to be noted, in this latter case, is that the intellect 

 does not show the same dependence upon the physiological 

 vicissitudes as the imagination. The imagery of our imagina- 

 tion, being rigidly correlated with the metabolic processes of 

 waste and repair at work in the cerebral cortex, manifests 

 correspondingly variable degrees of intensity and integrity, 

 but the intensity of thought is not dependent upon this alterna- 

 tion of excitation and inhibition in the cortex. Hence, while 

 the concomitant imagery is fitful, sporadic, and fragmentary, 



