While both ancient and modern physiologists were of opinion that the various phenomena of organized bodies were influenced by lunar phases, the power of the solar rays was not less active in regulating our functions both in health and in disease. The name of Phoebus signified the torch of life, and Apollo was the father of medicine and the fine arts. The sun was considered as a deity in most countries, the Supreme Being,—the father of light, Diespiter,—Jupiter, Jehovah, the creator of all living matter,—the residence of the Most High—In sole posuit tabernaculum suum, said the Psalmist;—and in Egypt three hundred and sixty-five priests were ordained to watch its heavenly movements during the year, while many philosophers attributed the propagation of the human race to the union of man with the orb of day. The disciples of Plato and Pythagoras considered it as possessing a soul; and Origenus, in his Periarchon, maintained that it displayed both virtues and vices,—an heretical doctrine very properly condemned by the second Synod of Constantinople; and, although St. Augustin was of that opinion, it was warmly combated by St. Basil and St. Ambrose, and many other beatified divines. Anaxagoras, on the contrary, considered this luminary to be a burning stone; Plato called it a compact fire; Aristotle maintained that it was formed of one-fifth of the elements that constitute the planets; Epicurus, a mass of lava, or ignited pumice-stone; Xenophon asserted that it was fed by exhalations, and Zeno by watery vapours; Empedocles considered it a translucent body; Philolaus, a concave mirror, concentrating the rays of light from every part of the universe to reflect it upon nature. Kepler was of a similar opinion, and further insisted that the sun was composed of a limpid fluid upon which a luminous Æther was reflected, whence its centre was blue, while the limbs were yellow. A modern philosopher, Woodward, attempts to show that the sun and fixed stars are masses of electric fluid, requiring no alimentation, yielding no smoke, and the light that emanates from them offers the bluish brilliancy of the electric spark. It has been justly observed, that if, like Eudoxus, we endeavoured to approach this luminary, the better to study and describe its nature, we should still remain in impenetrable darkness,—in which I must leave the matter, to confine myself to those influences which experience seems to show that the sun actually exercises on the animal economy.

The genial and invigorating glow that moderate solar heat produces has ever been considered as tending to prolong our life. Hippocrates observed, that old men are double their age in winter, and younger in summer. To enjoy this reviving influence, the ancients had terraces on their house-tops called solaria, in which, to use their own expression, they took a solar air-bath. Pliny the younger, in speaking of his uncle, tells us, Post cibum, Æstate, si quid otii, jacebat in sole. The ancients fancied that when the sun rose diseases declined, and Levato sole levatur morbus became a medical axiom. Aristotle records the case of an innkeeper of Tarentum, who, although able to attend to his business by day, became insane so soon as the sun had set. The moderns relate many similar instances of derangement brought on by the absence of solar influence. Bouillon mentions a woman who lost her senses at sunset, but who recovered them at break of day. Other cases are recorded of a different nature, when maladies were aggravated by this influence. Sauvage tells us of a woman who became maniacal whenever the sun was at its zenith; an influence that could not be prevented even by various stratagems, such as keeping her in a dark room, and deceiving her in regard to the hour. Humboldt knew a Spanish lady in Madrid who lost her voice the moment the sun dipped in the horizon, but the paralysis of the nerves of the tongue ceased the following morning. A removal to Naples cured this singular affection. Parham relates the cases of several individuals who were deprived of vision when the sun had set. In a former paper I have alluded to the effects of a vivid flood of light upon the Italian peasantry, as observed by Ramazzini. Daily practice shows us that the paroxysms of fever and various maladies are under a similar influence; and the evening gun in our garrisons is often the signal of severe exacerbation in certain febrile cases, while the reveillÉe develops acute aggravation in others. Sydenham and Floyer had observed that the gout and asthma were usually ushered in after our first sleep; and I have noticed that, during the prevalence of the cholera, the invasion of this fatal disorder generally occurred towards daybreak. The ancients divided their elementary predominance according to the diurnal cycle: thus, morning regulated the blood, noon the bile, evening the atrabile, and night the cold phlegmatic influence. Nor was this arrangement unnatural; we more or less observe it in a state of health, when man awakes refreshed and active at morn; towards noon his train of thoughts becomes more serious and busy; in the evening his mind is more gloomy and susceptible of unpleasant impressions; until night either sheds its poppies o’er his couch, or agitates his frame with its fearful dreams. The repose of night is ever more refreshing than that of day, however we may have changed the natural applications of our hours, and find, as Seneca said of Roman civilization, that antipodes habemus in urbe. The influence of night and day is equally observable in animals. Towards evening myriads of insects, who had shunned the solar heat, hum around us; while night calls forth its choristers; and as they cease to sing other creatures proclaim the dawn. Some animals, such as the simia beelzebud, and the simia seniculus, salute both the setting and the rising sun with fearful howls; and it may be considered as a law of nature, that we cannot turn night into day with impunity.

Dr. Balfour’s opinion on the influence of the heavenly bodies is of great weight: he conceives that the influence of the sun and moon when in a state of conjunction, which he names solar-lunar influence, produces paroxysms or exacerbations in continued fever, in all cases at least where paroxysms are observable. As this influence declines in consequence of the gradual separation of these luminaries from each other, and their getting into a state of opposition, a way is left open for a critical and beneficial change; in other words, that paroxysms and exacerbations in fever may be expected to take place at spring-tides, and crises at neap-tides.

It has been observed in intermitting fevers, that paroxysms of the quotidian recur in the morning, the tertian at noon, and the quartan in the afternoon; in no instance do they take place at night.

There can be no doubt that lunation, more especially in tropical climes, influences diseases; but the effects of insolation are every where observable. One of the most serious accidents resulting from this exposure is the ictus solis, the coup de soleil of the French, and the s???as?? of the Greeks, from the star Sirius, to whose influence they attributed the scorching heat of the dog-days. This attack is in general sudden, and the patient falls down as if struck with a blow on the head. Troops on a march, and labourers in the field, frequently are the victims of this solar power, which usually kills them on the spot. It has been known to destroy great numbers. In Pekin, from the 14th of July to the 25th, in the year 1743, it is related that eleven thousand persons were struck dead. On a hot day’s march in Portugal, I lost six men in a brigade under my charge. They first reeled as if under the influence of liquor, and then fell dead with a slight convulsive struggle. One of them, the bÂtman of the paymaster of the 3rd foot, or Buffs, was struck dead while speaking to me. A great number of greyhounds perished on the same march; but no other species of dog seemed to suffer, although we had many pointers and spaniels with us. Horses, mules, and cattle were also exempt from the attack, though it proved fatal to some weak donkeys who were following the troops. The shakos worn by our army are well calculated to preserve the soldier from these accidents, to which troops are constantly exposed during summer operations.