The effects of cold and heat recall to my mind the words that I heard in my youth from the lips of Abernethy, "Cold is bracing, heat relaxing—that is the notion, but only consider its absurdity. Heat excites, how then can it relax? There is a difference between heat and moisture and mere heat. They say a cold bath is bracing. Ah! a man jumps into a cold bath, and he feels chilled; he jumps out again, and rubs himself with a coarse cloth; he is invigorated, refreshed, and cheery; he feels as if he could jump over the moon. So, if a man takes a glass of brandy, he feels vigorous enough for a little while, but the brandy is any thing but bracing. Keep the man in the cold water, and see what a poor, shivering mortal he would be; you might almost knock him down with a feather; and add more brandy to the man, and he becomes a lump." Heat and cold, in fact, both operate in the same manner, by exciting the vital powers into action, but to use either to excess as surely debilitates, disorders, and overpowers the system as an abuse of brandy would do. All things that cause action of course must act as stimuli, and whatever rouses the heart and nerves must be proportioned to the degree of power existing in the patient, or it can not be safe; it is spurring the jaded horse that kills him. Moderation is the course prescribed in the law of nature and of God, and it needs no exquisite discernment to distinguish right from wrong in a general way, or to see when the system needs rest, and when rousing.
Sea-bathing is serviceable only as a stimulus to all the functions by rousing the nerves, and hence the heart and arteries, to greater activity. In this manner, I have seen vast benefit in a multitude of cases, more particularly those in which the lymphatic system and the glands were diseased, as in scrofula, tumid abdomen, and harsh skin, with deficient appetite, and indisposition to take exercise. It does mischief if it does not at once improve power. In such cases, however, great care is required to avoid too long a chill, which always aggravates the glandular congestion. Salt stimulates the skin, but a certain degree of cold, and, perhaps, of shock, is necessary for the beneficial effects, a warm bath very often increasing the malady. I speak from my experience of the effects of sea-bathing, and would strongly urge the propriety of preparing children for plunging in the sea, by getting them accustomed to cold sponging at home, as this plan will often supersede the need of visiting the sea for their benefit, and enable them to bear the sea the better when advisable.
Sea-air and sea-water exert a very decided influence upon children, and, indeed, upon all who are not accustomed to it, whether in health or disease. Young persons coming from inland situations are very apt to become somewhat fevered by the change, and bilious disorder is a common consequence of their approaching the sea; and in almost all persons sea-bathing begets after a while a slight intermittent disorder, which seldom goes quite off in less than a fortnight from the last bath. If the bath be resorted to daily, this disorder usually comes on in about a week; if only twice or thrice a week, it may not appear for a month, and those who bathe only now and then, without regularity, do not seem to be subject to it. I am disposed to think that this new action of the system promotes the cure of glandular disease, but it may, if neglected, conduce to internal disorder of a worse kind, and I have frequently seen a dangerous remittent fever supervene upon it in delicate and excitable children. These results prove the stimulating operation of sea-water, and sufficiently show the necessity of caution in its use. Instead of improving the powers of the body, it may produce debility by over-exciting them; hence it is prudent in most cases not to bathe oftener than every other day, and to use milder measures if, after the second or third occasion, there is not a visible increase of vigor. Where exercise can not be taken immediately after the bath, friction of the body, especially over the back and stomach, is desirable. The best time for cold bathing, where there is any debility, is about two hours after breakfast. Early bathing is best for the robust. Let it be remembered that cold acts always as a stimulant; whenever it does good, it rouses the nervous system; it makes a greater demand for oxygen; it enables the body to absorb more of the vital air, and thus it facilitates the changes on which the energy of life depends. In this respect it acts like all other stimulants proper to the body, and not like alcoholic stimuli, which excite the brain, while they diminish the influence of the vital air upon the blood, and favor capillary obstructions and inflammations.
The influence of cold on the nervous system is no new discovery, for ever since man has felt and inferred from his feeling, he must have known that influence alike from experience and observation. Used as a bath, we have seen that it may produce very contrary effects; like any other powerful agent, it both excites and depresses. The first action of nearly all remedies is to excite; from fire to frost, from aqua fortis to aqua fontis, the influence is always more or less stimulating, and it is capable of depressing the vital powers in proportion to its power of exciting them. Thus the hydropathists have in their hands the power of producing all the stages of the most vehement fever, from the rigor of the severest cold fit to the fiercest excitement which the heart and brain will bear, succeeded by a perspiration proportionately violent; and hence sometimes inadvertently they lose a patient by the production of a sudden sinking like the collapse of cholera. Some tact and skill, therefore, are requisite for the safe employment of such an agency as cold water.
Paracelsus treated that form of St. Vitus' Dance which prevailed in his day, and which he called chorea lasciva, by cooling his patients in tubs of cold water; and Priesnitz brings his patients also to the right point by baths that allow no idleness to whatever function of nature may remain capable of action within them, and thus he often removes partial complaints by a general diversion. Aubrey, in his account of the great Harvey, informs us of a bold piece of practice with cold water. He says, that when Harvey had a fit of the gout that interfered with his studies, "He would sitt with his legges bare, though it were frosty, on the leads of Cockayne-house, put them into a payle of water till he was almost dead with cold, and betake himself to his stove, and so 'twas gone." Harvey doubtless knew how to balance matters in his own mind between the risk and the remedy, and he might feel justified in treating himself with less gentleness than his patients; but, perhaps, physicians should try such extreme remedies only on themselves. Since Harvey's day, the virtues of cold water in fever and inflammation have been abundantly tested, and we find it is capable of producing contrary effects, according to the condition of the body at the time. Thus, if it be long applied, or applied when the vital action is low, it dangerously depresses the vascular system, to be followed by a more or less dangerous and obstinate reaction; but if the system be tolerably strong, without being very excitable, the use of cold in a moderate degree always safely increases vigor. It is therefore always safe so far to employ cold, as will help to maintain the ordinary temperature of the body. Thus, in fever, when the skin is hot, sponging it with cold water is both most refreshing and curative; while a free use of cold water as drink is almost always in such cases highly advantageous.
It has been well shown by Dr. R. B. Todd, in his Lumleian Lectures at the College of Physicians, on what principle cold may be employed to modify and control a great number of diseases, especially those of a convulsive character. But these things are of course known, or ought to be known, by professional men; and as they are not of a character to admit of practical application, except by those accustomed to treat disease, it will answer no good purpose to enlarge on the subject in this place.
The warm-bath is among the most useful of remedial measures. One who has experienced the delicious refreshment of a warm-bath at about the temperature of the blood (100°), after exhausting fatigue and want of sleep, whether from disease or exertion, will need no arguments in its favor. It is exactly under such conditions that it is most useful. From time immemorial, thermal springs of tepid warmth have been lauded for their virtues in relieving nervous disorders, and diseases dependent on insufficiency of blood, and exhaustion of the brain, such as the dyspepsy of anxious persons, and individuals debilitated by excitement, bad habits, and hot climates. The mode in which it acts seems evident—it checks waste of warmth from the skin, invigorates its vessels without producing perspiration, admits a little pure water into the blood by absorption, and by its tranquillizing influence on the nerves, favors the action of any function that may have been checked or disturbed. The body becomes highly electric in warm water, and probably all the conditions of increased power are present for the time at least; and of course, so far as warm bathing promotes appetite, digestion, assimilation, and sound sleep, it contributes to the establishment of increased vigor. Thus we find, that hypochondriacal patients have often found new hopes in the genial lymph as it embraced and laved their naked limbs; they have felt the elements were still in their favor; they have rejoiced in the sunny air, and taken their homely meals as if they were ambrosia, with hearts grateful to the Hand that helped them. The blessing may, however, be abused—the remedy may be made a luxury, the means of health a cause of weakness. When continually resorted to by persons well nourished, but inactive, it is apt to produce a flaccidity of the system, and to encourage that relaxation of the veins which predisposes to excessive formation of fat. For the same reason, it is generally injurious where there is a tendency to dropsy, and in some such cases I have known it immediately followed by great lymphatic effusion in the cellular tissue, which has been quickly removed, however, by saline aperients and tonics.
As it is the combination of heat and moisture that renders the thermal bath so efficacious, it frequently happens that a thoroughly hot bath most effectually facilitates the cure, and we are not astonished that the parboiling waters of Emmaus, at 148°, on the shores of Tiberias, are as famous for their cures as any of the German baths. The semi-barbarians about the sea of Galilee, the inhabitants of Iceland, and the savages of America, know how to employ the hot bath skillfully; and if we were equally accustomed with them to exercise our natural instinct and common sense, we also might bathe in hot water without consulting the doctor; but as it is, we had better take advantage of a better opinion than our own. I the more earnestly urge this course, because I know the danger of all hot baths, wherever there is acute disease of an inflammatory kind affecting internal organs, more especially of the lungs, heart, and bowels. Even acute rheumatism is more likely to attack the heart when the hot bath is employed; and where there is any considerable structural disorder of that organ, the use of the bath in any form is at all times attended with risk.
Warm baths are useful in all nervous disorders attended with debility, in all cases in which there is dryness of the skin and a tendency to feverish less, in mental fidgetiness, in irregular circulation, as when a person can not take due exercise, and is subject to coldness of the feet or hands, and in many forms of congestion and dyspepsia, with tenderness over the stomach. It is serviceable in the convulsive diseases of children, and in painful diseases, especially of a spasmodic kind, but more particularly in cases of chronic irritation from local causes, whether of the skin or of internal parts. It is injurious to plethoric persons, to persons subject to hæmorrhage of any kind, and in the active stage of fever. But whether it would be good or bad in any individual case, can be determined only by one who has ability to examine and judge of that case.
As a general rule, mineral and salt-water warm baths are less relaxing than those of pure water. The vapor bath, when the vapor is not breathed, acts more powerfully, though much in the same manner as the warm bath, but it is more useful in common cold and rheumatism. The warm-air bath, at from 100° to 120°, is highly convenient and useful, where it is desirable to excite perspiration, as in rheumatism, scaly eruptions, and certain stages of fever and cholera. The plan most readily adopted is that of Dr. Gower: A lamp is placed under the end of a metallic tube, which is introduced under the bed-clothes, which are raised from the body by a wicker frame-work, and the degree of heat regulated by moving the lamp.