the same processes and the same result are best brought about through the combined agencies of food and rest, with sleep. Sleep is here of value since, by its complete inhibition of the more obvious corporeal activities, it makes rest more complete and thus allows the more complete elimination of fatigue substances and restoration of those things that are essential to future activity.
Equally difficult with the problem of the extent to which labor may safety be carried is the problem of how much food, rest and sleep are required for healthful recuperation. How much we think we require is another question, for here again our sensations are misleading and it is easy to acquire habits which bear little relation to nature's demands. We here assembled, being in the shadow of Professor Chittenden's laboratory, are in the very center of the low-protein camp, and with appetites bridled we can safely defy those who tell us to eat what we please, when we please, and all that we please. There is, indeed, little doubt of the correctness of the main contention of Chittenden, Fletcher, Fisher and their followers, that it is physiologically advantageous to consume less protein than most of the civilized races consume, and it is impossible to avoid a strong suspicion that the presence of a superfluity of food stuffs within the body leads to an accumulation of intermediate metabolic products which in themselves act on the tissues as fatigue substances. The physiological optimum in the matter of quantity of food probably differs with each individual and, with our customarily unscientific habits of judging ourselves, is probably rarely known. This is equally true of the amount of rest and sleep required for recuperation. Our fathers told us "eight hours' work, eight hours' rest and eight hours' sleep"—yet did our fathers, more than we, literally observe the adage? As I believe that most of us eat too much, so I believe that most of us work too briefly and rest too long. Yet more significant than duration is intensity. "Work when we work, and play when we play," is not a meaningless nursery jingle, but a wise physiological dictum. Application, concentration, putting our whole selves into our task, with a wholesome disregard of fancied fatigue—that is the method of accomplishment. But when fatigue really comes, then should the task be laid completely aside for restoration. Play is one of the surest agencies for mental relaxation in the waking state. Pathetic was the confession of one of the world's most busy workers a few years before his death, at the age of forty-five, that he had "almost forgotten how to play." Effective sleep should be dreamless, and if it is of the right sort, it need not occupy one third of all our life. For most persons eight hours of actual sleep would mean nine hours in bed—and only a sluggard would demand that.
Food, rest, play and sleep may be regarded as the effective physiological antidotes to fatigue. One ingenious German investigator would add to these another. In an experimental study he believes that he has
