Zoonomia; Or, the Laws of Organic Life, Vol. II

by Erasmus Darwin

At the same time it must be observed, that the particles of water themselves, and of animal gluten dissolved in water, as the glue used by carpenters, slide easier over each other by an additional quantity of the fluid matter of heat.

These two fluids of heat and of water may be esteemed the universal solvents or lubricants in respect to animal bodies, and thus facilitate the circulation, and the secretion of the various glands. At the same time it is possible, that these two fluids may occasionally assume an aerial form, as in the cavity of the chest, and by compressing the lungs may cause one kind of asthma, which is relieved by breathing colder air. An increased quantity of heat by adding stimulus to every part of the system belongs to the article Incitantia.

[III]. [1]. The application of cold to the skin, which is only another expression for the diminution of the degree of heat we are accustomed to, benumbs the cutaneous absorbents into inaction; and by sympathy the urinary and intestinal absorbents become also quiescent. The secerning vessels continuing their action somewhat longer, from the warmth of the blood. Hence the usual secretions are poured into the bladder and intestines, and no absorption is retaken from them. Hence sprinkling the skin with cold water increases the quantity of urine, which is pale; and of stool, which is fluid; these have erroneously been ascribed to increased secretion, or to obstructed perspiration.

The thin discharge from the nostrils of some people in cold weather is owing to the torpid state of the absorbent vessels of the membrana sneideriana, which as above are benumbed sooner than those, which perform the secretion of the mucus.

The quick anhelation, and palpitation of the heart, of those, who are immersed in cold water, depends on the quiescence of the external absorbent vessels and capillaries. Hence the cutaneous circulation is diminished, and by association an almost universal torpor of the system is induced; thence the heart becomes incapable to push forwards its blood through all the inactive capillaries and glands; and as the terminating vessels of the pulmonary artery suffer a similar inaction by association, the blood is with difficulty pushed through the lungs.

Some have imagined, that a spasmodic constriction of the smaller vessels took place, and have thus accounted for their resistance to the force of the heart. But there seems no necessity to introduce this imaginary spasm; since those, who are conversant in injecting bodies, find it necessary first to put them into warm water to take away the stiffness of the cold dead vessels; which become inflexible like the other muscles of dead animals, and prevent the injected fluid from passing.

All the same symptoms occur in the cold fits of intermittents; in these the coldness and paleness of the skin with thirst evince the diminution of cutaneous absorption; and the dryness of ulcers, and small secretion of urine, evince the torpor of the secerning system; and the anhelation, and coldness of the breath, shew the terminations of the pulmonary artery to be likewise affected with torpor.

After these vessels of the whole surface of the body both absorbent and secretory have been for a time torpid by the application of cold water; and all the internal secerning and absorbent ones have been made torpid from their association with the external; as soon as their usual stimulus of warmth is renewed, they are thrown into more than their usual energy of action; as the hands become hot and painful on approaching the fire after having been immersed some time in snow. Hence the face becomes of a red colour in a cold day on turning from the wind, and the insensible perspiration increased by repeatedly going into frosty air, but not continuing in it too long at a time.

[2]. When by the too great warmth of a room or of clothes, the secretion of perspirable matter is much increased, the strength of the patient is much exhausted by this unnecessary exertion of the capillary system, and thence of the whole secerning and arterial system by association. The diminution of external heat immediately induces a torpor or quiescence of these unnecessary exertions, and the patient instantly feels himself strengthened, and exhilarated; the animal power, which was thus wasted in vain, being now applied to more useful purposes. Thus when the limbs on one side are disabled by a stroke of the palsy, those of the other side are perpetually in motion. And hence all people bear riding and other exercises best in cold weather.

Patients in fevers, where the skin is hot, are immediately strengthened by cold air; which is therefore of great use in fevers attended with debility and heat; but may perhaps be of temporary disservice, if too hastily applied in some situations of fevers attended with internal topical inflammation, as in peripneumony or pleurisy, where the arterial strength is too great already, and the increased action of the external capillaries being destroyed by the cold, the action of the internal inflamed part may be suddenly increased, unless venesection and other evacuations are applied at the same time. Yet in most cases the application of cold is nevertheless salutary, as by decreasing the heat of the particles of blood in the cutaneous vessels, the stimulus of them, and the distention of the vessels becomes considerably lessened. In external inflammations, as the small-pox, and perhaps the gout and rheumatism, the application of cold air must be of great service by decreasing the action of the inflamed skin, though the contrary is too frequently the practice in those diseases. It must be observed, that for all these purposes the application of it should be continued a long time, otherwise an increased exertion follows the temporary torpor, before the disease is destroyed.