Psychiatrists and psycho-pathologists, on the whole, have never been subject to the error of thinking that a man is a unit whose reaction to a given stimulus does not vary. Their work in the clinic and hospital would quickly force them to give up any such supposition. They naturally look for the conditions under which fluctuations occur and would probably be interested to hear that there are rhythmic changes in man's emotion apparently characteristic of the individual himself. Whether such cycles can be traced to specific factors and principles may be a difficult task to determine. The mere fact of its existence may be of value in making the economist and manager of work mindful of individual factors, as well as of the many impersonal factors in the important question of emotional attitude toward work.