In considering these and other changes produced in the system by bathing, we must be careful to avoid the very common error of applying inaccurately and indiscriminately the laws of mechanical and physical _ agents to the effects produced in the animal econo my. Some of the latest and best authors on thera peutics have talked of the expansion of the fluids contained in the vessels, in consequence of the ele vation of temperature occasioned by the warm bath, and of the contraction of the vessels themselves by the cold bath, as if they were phenomena of the same kind, and simply opposed to each other. The truth is, that the mean temperature of all the fluids in the body is seldom elevated more than a degree or two by the effect of a bath of any kind ; and even if the elevation were ten degrees, the expansion of all the circulating fluids would not exceed the bulk of a sin gle additional ounce of blood or of water. The me chanical effect of cold, on the other hand, would im mediately tend to lessen the tension of the vessels, by contracting the fluid contained within them more than the vessels themselves ; but this effect would be scarcely more sensible than the former, even if we allowed that the general temperature might be de pressed 10° or le, as it seemed to be in some of' Dr Currie's experimenta ; and the actual contraction, which is really observable in the superficial parts during immersion in the cold bath, can only be referable to the action of living powers, which fall decidedly under the description of involuntary muscularity. Dr Parry's late experiments have very clearly shown the existence of such powers, and exhibited their temporary and local action. ? He found that, when the carotid of a ewe was laid bare, its circumference was 525 thousandths of an inch; " but it almost immediately shrunk, through the whole space which was exposed, so as to become in circumference only .470 ; at the same time, a por tion of the artery, before the contracted part, and which had been more recently exposed, was .635 ; the pulse in the dilated part was very strong and full, that in the contracted part very weak and soft." Dr Parry has chosen to distinguish these effects from those which are observed in other muscular parts by a peculiar denomination ; but the distinction appears to be perfectly arbitrary, and Dr Young, whom he quotes as denying the muscular powers of the arte ries, on account of the chemical nature of their coats, has expressly asserted their muscularity, in contradiction to the conclusions of Bichat and Ber zelius. (Medical Literature, 8vo, Lond. 1813, p. 502.) But by whatever term we choose to denote the ef fect, there is little doubt that an unusual degree of cold has a tendency to produce such a general con traction of the coats of all the superficial capillary arteries ; and the diminution of their diameter must necessarily increase that part of the resistance to the blood's motion, which is derived from its friction against the sides of the vessels, and must, therefore, tend materially to lessen its velocity. Again, if the contractions of the heart are at all proportional in magnitude or in frequency to the quantity of blood entering it, and acting as a stimulus to its motions, it is not unnatural to suppose that its pulsations will be rendered feebler by the diminution of that quan tity, occasioned by the increase of the resistance, and that the primitive retardation will be redoubled by the operation of this cause. At the same time, however, that the cutaneous vessels are contracted, those of the internal parts must necessarily be en larged. Hence arises the sensation of oppression on the chest, with the sobbing or panting for breath, which generally occurs at the first immersion in cold water, from the fulness of the vessels of the lungs, and which is increased, in some measure, when the immersion becomes total, by the pressure of the wa ter on the abdomen, and consequently of the con tents of the abdomen on the diaphragm. From the same cause arises also the pulsation in the descend ing aorta, which has been observed to be much more distinguishable after swimming than at other times (Medical Transactions, Vol. V.) ; the internal vessels being distended so as to exhibit the effects of the heart's action more violently, and the heart itself beating with more than usual force in consequence of the exertion, while the contents of the abdomen are compressed, and are enabled, by the presence of the surrounding fluid, to transmit the pulsation very com pletely to the superficial parts, to which the hand is applied. The diuretic effect of a cold bath may be partly explained from a similar distension of the renal vessels, which must be favourable to the secre tion of the kidneys ; and if the same effect is some times produced in a hot bath, when the superficial vessels are rather dilated than contracted, it is in this case much less considerable than in the cold bath, and probably only takes place in consequence 'of the increased rapidity of the circulation, which affects the whole sanguiferous system.
The glow, which succeeds to the first sensation of cold, may be attributed in great measure to the in creased sensibility of the nerves after a partial tor por, rendering them more susceptible of the sensa tion of heat, which is always relative to the actual temperature of the skin ; but it appears, from Dr Currie's experiments, that there is also sometimes a real increase of heat as measured by the thermome ter; and it is probable, that the causes concerned in the production of animal heat are called up into a more vigorous exertion, in a strong constitution, whenever they are required for the purposes of life; so that they first supply the superficial parts of the body during the immersion, with as much heat as is necessary to overcome the painful sensation of cold, and afterwards, by a continuation of the same action, occasion an actual elevation of temperature above the natural standard. Dr Currie found, that, during the affusion of a bucket of cold salt water on the heads and whole bodies of two healthy persons, no depression of temperature was observable ; but in a minute or two afterwards, although they remained without motion, the mercury rose 2° : in a third per son of a feebler constitution, although the tempera ture remained equally unchanged during the affusion, it sunk, in a minute after, half a degree. These ef fects seem to be almost entirely independent of any change in the state of the circulation, which must be rather retarded than accelerated, while the gene ration of heat is increased. It is true, that the heart might be called into more powerful action at the same time that the pulsation at the wrist became feeble, from the permanent contraction of the radial artery ; but the action of the heart would still be ex hibited by the carotids, undisguised by this modifica tion ; and the carotids have not been observed to beat more strongly in the cold bath than at other times, although Dr Currie has remarked, that when " the pulse could hardly be felt at the wrist," " the heart pulsated with great steadiness and due force:" a fact precisely analogous to Dr Parry's interesting experiment on the carotid of the ewe.
Warm baths may be classed with propriety among the most useful sorbefacient remedies ; but it is not easy to decide, whether they are much more active in promoting absorption than other sudorifics, or than evacuants in general. When the weather de prives a valetudinarian of his accustomed walk, the bath often affords him a valuable substitute, increas ing the appetite, and promoting the digestion ; but too great an appetite, without muscular exercise, is sometimes lin evil, and this may have been one of the causes of the inconveniences occasioned by an abuse of bathing. A warm bath has often been of advan tage in promoting the absorption of dropsical fluids, especially when they are of limited extent, as in cases of partial anasarcous swellings ; but the most important sorbefacient effect of bathing is exhibited in the cure of glandular diseases, for which sea wa ter, whether in the form of a warm or a cold bath, has long been considered as a specific remedy ; and there is no doubt that a residence by the sea side, with a judicious employment of bathing, and the oc casional internal use of sea water, or of some equi valent remedy, has been of the most essential service to many constitutions, which have exhibited these symptoms of general debility and languid absorption; the tonic and sorbefacient powers of the remedy be ing happily combined, for invigorating and calling into activity the diminished energies of the constitution.
The refrigerant or astringent powers, both of warm and of cold bathing, have been abundantly elucidated by the late Dr Currie, who has introduced the reme dy into general practice, as a febrifuge, especially in the form of cold or tepid effusion, with the most sa lutary effects. It is not easy to determine how far the contraction of the superficial vessels by the astringent powers of cold, and how far the retarda tion of the pulse; which may possibly be dependent on that contraction, are concerned in the advantage derived from bathing in fevers ; but it is at least ob vious that the remedy does not operate simply by the abstraction of heat, since the tepid effusion is often more rapidly successful in abating fever than the cold.. We may also collect from the experiments
of Marcard, that a bath at about is more effica cious in abating the frequency of the pulse, than at any lower or higher temperature ; and these Facts appear to afford a very strong argument against the hypothesis, that the principal utility of the cold effu sion depends on the sudden shock which is given to the nervous system. Dr Currie has frequently found the pulse reduced by a single cold effusion from 120 or 130 to 80 or 90, and the heat from 104° or 106° to the natural standard. But he very pro perly limits the employment of the remedy to those cases in which the temperature is considerably ele vated, and the arterial system is in strong action, without local inflammation ; and where there is less vigour in the system, he often employs the tepid in stead of the cold effusion, or even contents himself with moistening the face and the extremities; for instance, in hectic fever, the hands and feet only, which he finds actually hotter than the rest of the body. A late writer on consumption has very justly remarked how much of Dr Currie's reasoning on the effects of cold bathing had been anticipated by Ga len, although, for want of a thermometer, he had not been able to employ the remedy in fever with safety. " Bathing," says Dr Young (On Consump tive Diseases, 8vo, Land. 1815, p. 135), " is very strongly recommended in the Method of Healing, and the process is very minutely described : first warm air is employed, next warm water, and then cold water, and lastly, the sweat is wiped off._ When we are fatigued or dried up by exercise, the bath' re stores us to comfort, and defends us from fevers. A Bathing. strong young man in the country will plunge into "..".^°•' cold water at once when heated, and be much re freshed by it. Animals also wash themselves when they are hot, by a natural instinct, as they eat when they are hungry, and seek warmth when they are cold. In fevers, if we had sufficient powers of dis crimination, we might probably sometimes derive ma terial advantage from the use of the cold bath, with out premising the hot ; and some persons have been actually benefited by this remedy. But without a more intimate knowledge of diseases than we possess, we cannot generally venture on the practice ; and least of all in hectic fever, where there is not strength enough to bear the shock. A stout young man, having a fever, in warm weather, without visceral inflammation, would bring on a salutary perspiration by bathing in cold water ; and if he were in the ha bit of cold bathing, lie might have recourse to it with the more confidence ; but, for the hectic, it is un safe, especially when there is much emaciation : thus, in a hot and dry summer, those who have travelled far, and are become thin and weak, have no need of being cooled, nor would it be safe for them to use the cold bath without first going into the warm. For we seem to be hardened by the cold bath like iron, when heated first ; and if we previously warm our selves by exercise, the effect is the, same." Dr Cur rie's relation of an adventure of his own might almost be supposed to have been intended as a commentary on these remarks of Galen. 120.) " On the 1st of September 1778, two of medi cine at Edinburgh set out on foot on a journey, a considerable part of which lay along one of the rivers of Scotland. They started by sun-rise, and proceed ed with alacrity in the cool of the morning. At the end of eight miles, they breakfasted, rested for an hour, and then resumed their journey. The day grew warm as it advanced, and after a march of eight miles more, they arrived heated, but not fatigued, on the banks of the river above mentioned, about eleven in the forenoon. Urged by -the fervor of the day, and tempted by the beauty of the stream, they strip ped instantly, and threw themselves into the river. The utmost refreshment followed, and when they re tired to the neighbouring inn, this was succeeded by a disposition to sleep, which they indulged. In the afternoon they proceeded, and travelling sixteen miles further at a single stretch, arrived at the inn where they were to sleep, a little after sunset. The afternoon had been warm, and they perspired pro fusely: but the evening was temperate, and rather cool. They had travelled for some miles slowly, and arrived at the end of their journey stiffened and wearied with their exercise. The refreshment which they had experienced in the morning from bathing induced, however, one of them to repeat the experi ment, and he went perfectly cool into the same river, expecting to relax his limbs in the water, and after wards to enjoy profound sleep, The consequences were very different. The Tweed, which was so re freshing in the morning, now felt extremely cold ; and he left the water hastily. No genial glow suc ceeded, but a feverish chill remained for some time, with a small frequent pulse, and flying pains over the body. Warm liquids and frictions brought on at length considerable heat, and towards morning per spiration and sleep followed. Next day about noon they proceeded on foot, but the traveller who had bathed was extremely feeble ; and though they had to perform a journey of a single stage only, as some part of it was difficult and mountainous, he was obliged to take the assistance of a carriage which overtook them on the road. It was several days be fore he recovered his usual vigour." The experiments of the same judicious author, published in the Philosophical Transactions for 1792, afford some striking illustrations of the effects of se vere cold : he employed baths at the temperature of 44° and the natural pulse of the person sub jected to the experiment was shout 70 in a minute, and it was generally raised to 85 or more by the pre paration for immersion ; but in the water it invariably. sunk to about 65, becoming firm, regular, and small. The change of temperature, as measured under the tongue, was still more remarkable, and greater than could have been expected either from 'reasoning or . from former observations; for the mercury fell, within a minute or two after immersion, from 98° or 100° to 87° or 88° ; it then rose gradually, but not regu larly, in a quarter of an hour, to Upon a second exposure to the wind, it fell to about 90°, and was in one instance lowered 2a more at the first im mersion in a bath of in which the natural tem perature was by degrees recovered, although not much more rapidly than it had .risen during the firmer im mersion in the very cold water ; but what raised it by far the most the application of very hot water to the region of the stomach. When, how ever, Dr Currie himself went slowly into a bath of 36°, in a fight flannel dress, and remained in it for two minutes, no observable alteration was produced in the heat of his body ; circumstance might almost induce us to suspect that the other subjects of his had incautiously allowed their mouths to be cooled by the inhalation of the cold air. Dr Marcard's experiments (p. 71) not only confirm the fact of the general retardation and diminution of the pulse by the cold bath ; but they show that the retardation commonly extends to all temperatures below that of the human body, becoming, indeed, much more remarkable in the tepid bath than in a bath of the ordinary temperature of the atmosphere, which does not appear to produce the effect with equal uniformity. Thus, in a bath at 60° and at the pulse was rather accelerated than retarded : in -six experiments from 70° to 80° ;nclusive, taking the mean of all the quantities, in order to obtain a result less liable to accidental errors, and representing all the experiments in a compendious form, the tempe rature was 75°, and in 20 minutes the pulse was reduced from 78 to 70: in four from 80° to 90°, the mean temperature was 87°, and the pulsations were reduced in 54 minutes from 91 to 75 : in three at 90°, the mean reduction in 36 minutes was from 97 to 75 : and three experiments afiove 90° give for a mean temperature 92°, and a reduction from 82 to 70, ef fected in 35 minutes. Marteau had Pound a slight reduction of frequency at 93° : but at 96°, according to Dr Parr, there is commonly no observable change. (Marcard, p. 68, 66.) From these experiments Dr Marcard very justly infers, that in a great variety of cases, the warm bath affords the only direct and certain mode of lowering the poise without inconvenience (p. 88)4 and we must be contented with the empirical know. ledge of this fact, without attempting to explain why a temperature of 90° is more favourable for the re tardation of the pulse, than a much lower tempera. tore, t which the thermometrical heat would cer. tainly be more rapidly reduced. Dr Stork has also made several observations on the effect of cold bath• ing on the pulse; but, in his experiments, the retar dation was much less constantly observable than the diminution ; a variation which frequently occur* when the temperature is very low.