sources, however inexpedient, is not disease, and seldom inflicts permanent injury. A temporary collapse of the mental powers may be caused by excessive or too continuous exertion, just as a surface-well may be emptied by pumping it out more rapidly than it is refilled, but the apparatus is not thereby disorganized, and time will remedy the defect. When rest is not followed by recovery, the recuperative faculty itself, an integral part of the intellectual organism, must be impaired or disabled. This is not unfrequently the case when the possessor of a worried and weakened brain in vain seeks refuge from the supposed effects of "overwork" in simple idleness. Something more than exhaustion has occurred, and rest alone will not cure the evil. The faculty of repair is not in a condition to restore the equilibrium between potential energy and kinetic force. Divers hypotheses have been suggested to explain this state of matters. The mind has been compared to a muscle overstrained by a too violent effort, or paralyzed by excessive exertion. The two phenomena have little similarity, and no new light is thrown on the nature of mental collapse by the comparison. Perhaps a closer parallel might be found in the state which ensues when the tension of a muscular contraction is so high that spasm passes into rigidity, and molecular disorganization ensues. Meanwhile, however interesting these speculations may prove to the physiologist, they bring no relief to the sufferer. It is easy to see that a worse evil than simply using up his strength too rapidly has befallen him, but no one knows precisely what has happened. To cover the enigma, without solving it, "overwork" is taken to mean more than work over the normal, in quantity, quality, and time, but no attempt is made to determine how excess, in either or all of these particulars, can bring about the disability and decrepitude we bewail. It is to the investigation of this mystery that attention needs to be directed. If it should be possible to ascertain why a mind previously healthy, and still apparently intact, breaks down instantly and thoroughly under a strain not exceptionally great, and, collapse having once occurred, recovery follows tardily and is rarely complete, it will probably be within the scope of common-sense to draw some practical conclusions as to the prevention, and it may be the cure, of what is in truth becoming a scourge of mental industry already almost decimating the ranks of the army of progress, in every field of intellectual enterprise at home and abroad.
A certain degree of tension is indispensable to the easy and healthful discharge of mental functions. Like the national instrument of Scotland, the mind drones wofully and will discourse most dolorous music, unless an expansive and resilient force within supplies the basis of quickly responsive action. No good, great, or enduring work can be safely accomplished by brain-force without a reserve of strength sufficient to give buoyancy to the exercise, and, if I may so say, rhythm to the operations of the mind. Working at high-pressure may be bad,