Southey refers to the depressing influence made upon him by the “vile, dark, rainy clouds” of Great Britain, when he returned from a sojourn of 15 months in sunny Italy, where his brain was in a state of high illumination. An Italian proverb runs thus: “Where comes no sun the doctor comes.” Similarly a German saw: “The funeral coach turns twice as often on the shady side of the street as on the sunny side.” J. Ashby-Sterry has dwelt upon the demoralizing effect of the London fog:
“A London fog when it arises
All London soon demoralizes.”
“It chokes our lungs,
Our heads feel queer,
We cannot see, we cannot hear!
So when this murky pall drops down,
Though dearly loving London town,
We feel we cannot quite revere
A London fog.”
Likewise Walter C. Smith:
“A grey fog in the early prime,
A blue fog by the breakfast hour,
A saffron fog at luncheon time,
At dinner a persistent shower
Of smut, and then a dismal power
Of choking darkness and despair,
Thickening and saddening all the air.”
A special questionnaire investigation on nephelopsychosis made some years ago by G. Stanley Hall and the writer ([9]) indicated that heavy black clouds and fogs may often strike fear or terror into children, or may make them feel depressed and gloomy or restless. Some children experience “terrible fear” at times and others feel that “something dreadful will happen when the horrible black ones appear.” There are cases on record of actual motor paralysis caused by terrifying clouds. There is here an interesting parallelism between the emotional responses called out by clouds in the children of to-day and the responses called out in primitive races. In his mythopoetic tendency primitive man read fear and danger in dark clouds, particularly the black thunder clouds. The smoke clouds of our city probably depress children just as any dark clouds do, and when particularly black may also arouse nephelophobias.
Sir Archibald Geikie has ascribed the subdued, grim character of the Scot to the gloom of his valleys and the canopy of cloud “which for a large part of the year cuts off the light and heat of the sun.” The French formerly regarded the Englishmen as “rude, unlettered ... surly, ill-conditioned men, having lived in an unhappy climate where perpetual fog, only varied by rain, prevented the sun from ever being seen, suffering from so deep and inveterate a melancholy that physicians had called it the English spleen, and under the influence of this cruel malady constantly committing suicide, particularly in November, when we were well known to hang and shoot ourselves by the thousands” ([2]).
On the other hand, there are those who believe that the monotonous gloom of England has inoculated the Britain against moods of depression and hypochondria, and made for the evenness of temperament which is said to characterize him ([18]). Gloomy weather would thus serve as a catharsis against the very depressions which it is said to induce. I must confess that this reasoning seems to me to be quite specious. The effects of meteorological monotony, particularly of depressing states, probably do not differ from the general effects of physiological or psychic monotony: narcosis, hypnosis, fatigue, overstrain, distaste, or aversion. However that may be, there can be no doubt that many persons experience an exhilarating, tonic effect on a bright, sunshiny day and a depressing influence on gloomy days—assertions that have, indeed, been ridiculed by Dr. Johnson. Fortunately these impressionistic views on the buoyancy of sunshine and on the depression of gloom (particularly cold or hot, damp, dark days) find a certain degree of support in scientific studies.
Deprived of sunshine the human skin assumes a pale greenish hue, like the skin of the people in the polar regions. This is probably due to the absence of the blue and ultra-violet rays of the sun which dilate the blood vessels and bring the blood to the surface, and to the absence of the infra-red rays which are associated with heat. Sunshine promotes transpiration and perspiration, and thus favors the elimination of toxic products through the skin. Bright, sunny days lessen the strain on the kidneys.
The amount of blood and the per cent. of hemoglobin are increased by sunlight and decreased by darkness. Oerum, in an experiment on animals, found that light increased the quantity of blood 25% in 4 hours. Likewise Grawitz and Graffenberger have observed a diminution in the quantity of blood in animals kept in the dark, while Marti found under similar conditions that the number of red blood corpuscles was lessened ([13]). There is thus a loss of red coloring matter in the blood of animals kept in the dark. The well-known baker’s anemia points to the same impoverished state of the blood in night workers (Gardenghi, [13]). Not only so: in an examination of 29 persons Finsen ([7]) found less hemoglobin in the winter than in the summer, presumably because of the diminished sunshine in the winter time. Diesing suggests that the lack of sunlight in northern countries is an essential factor in the causation of rachitis. The rays of the sun—specifically the blue and ultra-violet rays—thus exercise a tonic or stimulating action on the organs of circulation, transpiration and elimination, and very probably also directly stimulate the nervous system. Finsen has shown that benumbed or apparently dead insects have been revitalized by the application of ultra-violet rays. It is doubtful whether this stimulating effect is due to increased electrical potential, as argued by Dexter ([5]), because the more intense the sunshine and the higher the temperature the lower is the potential ([14]). The stimulating effect is probably due to the chemical action of the short rays of light. These rays probably penetrate the deeper tissues of the body just like the X-rays. It is well known that persons suffering from chronic joint disease, particularly from joints affected with tubercular sinuses, can be greatly benefited or entirely cured by constantly exposing the affected limbs to the direct rays of the sun. Guggenbuhl, it will be recalled, attained some success in the treatment of cretinism simply by removing the cretins from the dark Alpine valley to the sunlit summit of the Abendberg.
Because of the stimulating effect of sunshine, may not an excess of sunshine be just as detrimental as a deficiency? It has, indeed, been assumed that the climatic dangers of the tropics are largely due to the injurious tropical sunlight, particularly to the abundance of the ultra-violet rays. Woodruff holds that the failure of the white race to colonize in the tropics is due to the excessive light, and not to the heat and humidity. The light, he contends, tends to produce ennui, neurasthenia and ultimate collapse in blond persons ([26]). This conclusion is not sustained by recent investigations. Experiments have shown that monkeys do not succumb from insolation in the tropical sun if care is taken not to allow the bodily temperature to rise, by conducting away by brisk air currents the excessive heat (Aron, [23]). The injurious quality of the solar light is thus due to the infra-red and not the ultra-violet rays. The white man can secure adequate protection in the shade from the heat rays, and by wearing white clothing he can be adequately protected from the ultra-violet rays.