CHAPTER I.
CAUSES OF DISEASE.
The causes of disease are spoken of by authors as predisposing, and exciting. By proximate cause of disease is meant the cause of the symptoms present; this cannot appropriately be dwelt upon here.
By exciting cause is meant the immediate cause of a disease, and the distinction from predisposing cause arises from the fact that when two persons are exposed to something injurious to the health, they may not be equally affected.
It has been said that if twenty persons undergo hardship and exposure from shipwreck, the effect of the wet and cold may be in one to cause catarrh, in another rheumatism, in a third pleurisy, in a fourth opthalmia, in another inflammation of the bowels, and fifteen may escape without any illness at all. A predisposing cause is defined to be anything whatever, which has had such an influence on the body as to have rendered it unusually susceptible to the exciting cause of the particular disease. In most cases the distinction is obvious, but it is sometimes difficult to say of a given cause whether it ought to be ranked among the predisposing or the exciting causes.
Disease is often warded off notwithstanding the presence of the exciting cause, when we ascertain and prevent the predisposing cause of it, and it may sometimes be averted in despite of strong predisposition, if we know and can guard against the agencies by which it is capable of being excited.
When we enumerate causes of disease we see among them many that under ordinary circumstances minister to life, health, and enjoyment; and I can hardly refer at all to the varying circumstances under which they become the medium of pain, disease and death. These circumstances are so various, so many of them are apt to be put in operation at the same time, and so little power have we of excluding them one after the other, so as to ascertain the exact efficiency of each, that our observation respecting their actual effects are open to much fallacy.
We cannot for instance in a given case estimate accurately the effect of impurities in the atmosphere such as organic and inorganic dust, nor the effect of differences in degree of its natural qualities such as extremes of heat and cold, sudden variations of temperature, excessive moisture or dryness, different electric conditions, differences of pressure, a deficiency of light, and the amount of ozone, &c.
OF HEAT AND COLD AS EXTERNAL AGENCIES CAUSING DISEASE.
The range of temperature compatible with human life is very great; men live in the hottest and the coldest climates, where the earth produces any sustenance for them. It requires more care to preserve life under intense cold than under intense heat. Tropical climates are thickly peopled where the thermometer ranges from 80° to 100° for a long time together. In arctic countries on the other hand where the thermometer sinks to 40° or 50° below zero, we still find inhabitants, but they are few and thinly scattered. It is probable that at a degree of temperature a little greater than that of the equator or a little less than that of the poles men would perish.
Man is capable of existing under certain circumstances for a short time, and enduring a much higher degree of heat than the general atmosphere attains in the hottest portions of the earth, but there are generally some deleterious effects from hot climates or continued hot weather.
The effect of HEAT is to stimulate the organic functions of the body, but when considerable heat is applied for some time together its effect is to cause languor and lassitude, want of energy, a disinclination for exertion both bodily and mental; it has a depressing effect generally upon the animal functions or the nervous system, and there are some forms of disease that are distinctly traceable to heat as a cause.
We all know the effect of hot weather in causing perspiration, and when the operation of high temperature is continued for some time it has a marked influence upon the liver, increasing the quantity of bile that is secreted, and altering its sensible qualities; this is sometimes followed by inflammation of the liver.
In this country those attacks of vomiting and diarrhœa which are so common towards the latter end of summer or in autumn are the effects of a succession of hot days. In tropical climates the morbific effects of external heat are still more conspicuous, tending to violent disorders of the stomach and intestines, and also to acute inflammation of the liver and to acute abscesses in that organ.
In these cases the heated atmosphere unduly stimulating the secreting function of the liver creates the predisposition to the disease, while the exciting cause of the inflammation may be exposure to cold.
There may be deleterious effects from exposure to cold where the climate is quite hot. For instance a man may after the heat occasioned by the employments of the day, undress and lie opposite a window, his shirt wet with perspiration, to enjoy the sea breeze at night, and though the thermometer may be as high as 80° he may have a sensation of cold. If there is real chilliness it may be deleterious.
Heat sometimes acts as an _exciting_ cause of disease—it produces sunstroke, or it may produce an eruptive disease such as prickly heat, &c.
The effect of extreme COLD (I use the term cold in the popular acceptation), when its application is continued, is that of a sedative upon the organic functions. Though at first causing pain in the extremities, if continued it causes sleep or overpowering drowsiness. Before this complete stupor comes on there may be a blunting of the sensations and confusing of the intellect, giving to the person exposed to it, the appearance of one intoxicated. When persons in this state are suffered to sleep, and the operation of the cold continues, they become less and less sensible to external impressions until death closes the scene.
But the effect of cold upon the body within certain limits of intensity and duration is that of a tonic. When its refrigerating and sedative properties can be sufficiently counteracted by exercise and warm clothing, cold is stimulating, refreshing, and invigorating to mind and body, it clears and sharpens the faculties, bestows alacrity and cheerfulness of spirits, and may become a curative agent.
Yet exposure to cold is one of the most common causes of various complaints. As a rule it is true that there is danger from sudden vicissitudes of temperature, although the proposition requires limitation. No peril need attend a change from a hot to a cold temperature if the power to evolve heat inherent in the system be entire and active and persistent, not lessened by any of those circumstances which have the effect of weakening it, such as local disease, and fatigue. Cold is dangerous, not especially when the body is hot, but when it is cooling after being heated. At such times taking a large draught of cold water, or cooling the body suddenly some other way might cause death immediately; if not, an inflammation of some internal part of the body might arise.
Every thing that has the effect of weakening the system and so diminishing the power of evolving heat, favors the morbific effect of cold, and is a predisposing cause of disease. The most common of these debilitating circumstances are fasting, evacuations, fatigue, a last night’s debauch, excess in venery, long watching, much study, and rest or inaction immediately after it, or after great exercise.
The faculty of evolving heat is weak in old persons and in the newly born, and these are often the victims of the power of cold.
The bad effects of cold depend very much upon the duration of the sensation. Even slight feelings of chilliness, if long protracted, are apt to terminate in some form of disease.
Cold is more likely to prove injurious when it is applied by a wind or currant of air, and the injurious operation of cold is augmented when it is accompanied with moisture—wetness is the worst way in which cold can be applied. The contact of wet or damp clothes with the skin, both increase and prolong the sensation of cold. A foggy atmosphere is more prejudicial than a clear one of the same temperature. While we are asleep, also, our power of resisting the effects of cold is diminished.
The power of habit enables a person to resist the effect of cold, and we may sometimes turn our knowledge of it to good account in gradually fortifying the system against the influence of cold that cannot be avoided. But we must not, while we fear to render our children effeminate by over care and much clothing, run into the opposite extreme and endanger their health by exposure. The process of hardening is doubly dangerous when it is attempted with children who were originally delicate, and should never be tried on any child or any person who is unsound, who shows any signs of present or approaching disease, or any marked predisposition to future, and especially to scrofulous disease.
An abiding sense of chilliness must never be permitted even when we are endeavoring to accustom a child to cold. If they can be kept in the cold air, and at the same time be kept feeling warm either by exercise, diversion of the mind, or by clothing, the result as regards the health is good.
The cold bath, and especially the shower bath, is a good means of fortifying the body against cold air. When we take a cold bath in the morning, if the sense of cold does not remain long, and is followed by a glow of warmth, the bath is sure to do good. If, however, after the bath we suffer headache, and continue to be chilly and languid or uncomfortable, it should at once be given up as useless and dangerous.
EFFECTS OF THE SEASON UPON HEALTH.
In this country, generally, catarrh and coughs and pectoral complaints of all kinds, are most apt to prevail in the winter and spring months, while bowel complaints are more numerous and distressing in the summer. The mucous membranes of the air passages sympathize with the skin under the agency of external cold; those of the stomach and intestines under that of heat.
The thoracic disorders which commence or grow worse in the winter are often fatal, and there are various other maladies that are aggravated by cold, so that the mortality of winter is greater than that of summer. Bowel complaints are more prevalent at the latter part of summer or early fall, when moderately cold days succeed a long period of hot weather, the high diurnal temperature being the predisposing cause, and the cold exciting or bringing on the disease.
I shall not refer to other causes of disease except to say that if two persons marry each other who have a hereditary predisposition to disease, their children, if they have any, will probably not be healthy.