Scholars, who live entirely from the product of their mental labors, often do not present a healthy appearance, and are not infrequently subject to nervous, gastric or intestinal disorders, chronic constipation, etc. In laborious mental activity an excessive amount of blood flows to the brain, that of other organs being withdrawn, and thus diminished formation of gastric juice is favored and the appetite reduced. Intellectual activity should, if possible, be suspended a full hour before and after meals. Congestion of the brain likewise interferes with proper sleep, which, as a rule, can only become truly deep when the brain is bloodless. Intellectual efforts should therefore be avoided for a period of one to two hours before going to bed, and especially one should not read in bed.

After a good night’s sleep the brain is adequately rested and hence capable of doing the most work. For this reason the morning hours are the best of all for mental labor; the very early hours have the additional advantage of absolute quiet and freedom from disturbance. Personally I work preferably from 5 to 8 o’clock in the morning, especially in the winter time when one cannot well go out walking so early.

In a previous chapter I mentioned the fact that organs upon which great demands are made more readily become the seat of arteriosclerosis because of the abundant flow of blood to them. In persons of great intellectual activity we accordingly find marked sclerosis of the cerebral arteries, especially if they have the bad habit of smoking and drinking excessively. Besides, drinking interferes with the quality of work done. The influence of smoking in the production of arteriosclerosis we have already discussed. Under normal conditions intellectual workers can live to an advanced age—this we know from numerous celebrated instances: Hippocrates, Democritus, Plato, Plutarch, Leibnitz, Newton, Galileo, Michael Angelo, Carlyle, etc. Socrates wrote his Panathenæ in his 94th year, the celebrated Dr. Hufeland the fifth edition of his “Makrobiotik” at a ripe old age, while Goethe’s powers of execution remained to the last undiminished. Recently I received from an English colleague 80 years of age, who had attained eminence by his studies on metabolism, an excellent work on diabetes, which he had just brought out.

With but very few exceptions, we find that the great master-intellects who attained to an advanced age led lives of moderation in every respect—not only as to their bodies, but also their minds. Whoever lives as hygienically as did Newton, can, like him, become very old in spite of bodily weakness. Newton was a very frugal eater, had no passions and never worked until over-fatigued. Not to work to excess, to permit one’s self to rest at the proper time—this is the chief precept in the hygiene of the mind. The brain requires rest even more than any other organ from which great activity is demanded. One should not work more than a few hours at a stretch.

I strongly recommend going to bed at ten or eleven o’clock, rising at five to half-past six o’clock, and then after refreshing one’s self, at once settling down to work. Breakfast may be eaten at about eight o’clock. A walk should then be taken before going back to work, which should be interrupted an hour before dinner-time and only resumed an hour after the meal. In the warmer seasons it is best to work in the garden or in the woods whenever the nature of the work permits. It is advisable to leave off one hour before supper, and then, as a general rule, do nothing further, but take a walk, if possible also before supper. In general, mental workers need plenty of exercise in the open air; especially in the woods or elsewhere in the midst of foliage is the flow of ideas more easily aroused. When it is not too hot, one may sit out in the sun while working, though the eyes and the book or paper should be shaded. The combination of pure air, sunshine, and mental occupation is of great value. Laboratories and libraries should be so disposed as to correspond strictly to all rules of hygiene regarding air and light.

In winter time one gains distraction by visiting friends, attending society meetings, concerts, theatres, etc. In every season of the year it would be well to spend Sundays in the country. It is necessary, likewise, to follow the general rules of hygiene. Insofar as the diet is concerned it is strongly to be recommended during heavy mental labor, especially where much thinking is required, that meat-eating be given up and a vegetarian diet, with the addition of milk products and eggs, adopted. At any rate, a diet rich in meats must be avoided; it not only makes one heavy and dull, but also creates a want for alcohol, coffee, tobacco and other unwholesome stimulants, for which a diet containing little or no meat need evoke no desire.

Regularity and moderation heighten the expectations of long life in mental workers and guard against the premature failure of the intellectual powers which must sooner or later follow upon overwork. This not infrequently happens quite early in life. Boerhaave could already cite two such cases; “I have known a young man who knew everything and was a prodigy of learning, but who hardly lived to the age of 25, and another who worked day and night with the industry of a bee, and without any definite illness died in his nineteenth year in a state of emaciation.” In common with scholars and men of letters physicians must take particular care of themselves, their brains being continually on a stretch. The efforts they make to prolong the lives of others shorten their own—the irony of fate! Few callings demand as much mental work as that of the medical man. We physicians often have to deal with infectious diseases; since the continued mental strain is capable of injuring our bodily health and hence diminishing our resisting power against infections, it is advisable for us as far as possible to avoid all harmful influences,—and especially excess of any kind.