daylight is as necessary for man as it is for the flower. One reason the reason one might say-why man rises at all is that towards waking time there is a return of vigour to the outward part of the frame. Of this there are many proofs; one is that more carbonic acid is breathed out of the lungs from daybreak to noon; another that the pulse rises towards the time for waking. Dr. Knox of Edinburgh, one of the greatest thinkers and observers of any age, found from a very extensive series of notes made principally among his students that the pulse rose regularly towards morning. Guy did the same.* This disposition seems to prevail in disorders, which I shall endeavour to show are only an exaggerated form of natural action. One of the most regular forms of disorder, one of the favourite studies of physicians in all lands and all times has been fever. Now Dr. Gregory tells us that in all febrile disorders there is a tendency to get worse in the evening (or when the outward life is weakest), and to remit in the morning.† Mr. Durham being anxious to ascertain the condition of the brain during sleep administered chloroform to a dog, and while it was insensible removed a portion of the skull, substituting for it a piece of glass. He found thus that when the dog slept the blood-vessels were comparatively empty, the arteries lost their bright red colour and assumed the blue colour of the veins, and the brain tissue *Guy's Hospital Reports, 1st Series, vol. iii. collapsed, leaving a space within the skull which was filled with cerebral fluid. When the dog was awakened the blood-vessels resumed their functions and the brain once more filled the cavity. How necessary sleep is to health, strength, and freshness most people know. Mr. Durham mentions that a chinese murderer whose punishment was total want of sleep, died on the ninth day. Brodie says that a gentleman who passed six days and nights without sleep, was seized with such illusions that it was necessary to place him in confinement. At the same time there are apparent anomalies which seem difficult to explain. Many persons have passed months without one night's good sleep, and therefore must have been in that time subjected to several times the amount of loss which in the one case kept up for a week had produced fatal results. The explanation is that in these persons the natural cycle of action and rest was never completely broken for a great length of time. A vast amount of interruption to natural action may be endured if it be spread over a sufficiently long period. Sir Henry Holland speaks of the difficulty of explaining the physical causes of sleep as almost insuperable, and Dr. Graves* says that all the explanations of hunger are unsatisfactory, but according to the views now given I do not myself see any insurmountable obstacle in the way. But why it may be asked is there a return of vitality towards the animal life in the morning? The answer is that rest beyond a certain time for any function means the beginning of decay and death of the parts * Studies in Physiology and Medicine. which perform this function. If they have no natural action they will have an unnatural one; absorption, wasting, and disease will come on; the stomach without food will digest itself. But provident nature has provided a safeguard, and at the first sign of this the vital power begins to flow from the seats of nutrition to the brain, muscles, and stomach. It resumes its seat in the organs of animal life, and in consequence man awakes to seek that food and action which employ these organs in their natural way. The first function is exercise of the animal life either of the brain or muscles. Taking life all over the globe, it may be safely said that the muscles are most worked in the morning. Instinct has taught the working classes that this is the time for toil; it is a saying amongst masters who have risen from the station of labouring men, among captains of ships who have seen workmen of different nations, that there are no two hours of the day in which so much is done as in those before breakfast. Efforts have been repeatedly made, sometimes from pure humanity, at others from selfish motives, and at others again in the interest of commerce and policy, to change this and induce the men to begin work later and leave off later, but they have almost uniformly been resisted. And yet this is at the close of a period when least food is taken, and in fact when food cannot be borne. It is only among those who have long reversed the ordinary habits of life, that even the hardest workers can take a hearty meal so early in the morning as four or five o'clock. It seems quite as universal a rule that the principal part of food is taken after the bulk of man's work is done. The workman begins at six and goes on till eight-breakfasts-resumes his work at half-past eight, and works till half-past twelve or one o'clock, when he dines, rests now for an hour and continues till six; thus performing six hours' work before dinner and four hours after it; the latter part of the work being I believe with few exceptions worse got through than the other. Again the merchant or lawyer gets through the bulk of his work before dinner, and as surely as men attempt to break through this natural tendency so surely does the health give way. The young in whom digestion is very powerful, bear it pretty well, but elderly and feeble persons soon find the ill effects of it. The more, too, a man works his brain the more does he require rest after dinner. To what is this due? By what theory is it to be explained? The mechanical physiologist, who must always talk of man as if he were a steam-engine, says that motion disturbs the digestion. Very likely it does, but I want to know how? Mechanical physiologist says by the exercise disturbing secretion of gastric juice and causing contents of stomach to ferment, &c. But this is simply telling me the same thing in other words, so I give up mechanical physiologist and turn to nature, who tells me that the disturbance of digestion is as complete if a man goes off to his study, and sets to work upon the binomial theorem, and that the real secret is that the vital power cannot keep up two actions at one time. Weakly persons often feel chilly and sleepy after dinner, facts of which I see no explanation save by applying the same rule to them. Exercise of the higher functions of the frame follows naturally much the same path as that of the merchant, being chiefly performed between breakfast and dinner, or in the evening after digestion is pretty well completed. Some few persons work irrationally; astronomers and others are compelled to do so, but as a rule abstruse and vast problems are rarely worked out at other times. Bright immortal thoughts have often risen to the mind in the stillness of midnight, in long wakeful hours, as they will in the throng of business, in the dance, at the theatre, at lectures, or in lonely walks; Milton is said to have been in the habit of rising in the night and writing down his recollections of those grand visions, and many of his noblest lines are related to have been thus preserved. But the great labour of weighing, testing, and shaping out such thoughts is as much the work of the busy garish day as double entry is. Besides these thoughts at midnight are only fitful flashes of an overtasked brain, and as the tide of the vital power sets in towards the centres of nutrition they get fewer and fainter till they altogether cease. In fact persons who lead at all regular lives notice little of this kind of thing after two or three o'clock in the morning, for a reason to be afterwards given.* I fancy it will generally be found that the most wholesome genial writing, like that of Scott and Washington Irving, Dickens and Shakspere, is done in the morning, or when the brain is well cleared up in the evening. The heated morbid fancies of a Schiller, a Shelley, or a Poe remind one irresistibly of spectres * See page 375. |