Hydropathy, as a system, or mode of treatment complete in itself, dates from about 1829, when Vincenz Priessnitz (1801-51), a farmer of Gräfenberg in Silesia, Austria, began his public career in the paternal homestead, extended so as to accommodate the increasing numbers attracted by the fame of his cures. Two English works, however, on the medical uses of water had been translated into German in the century preceding the rise of the movement under Priessnitz. One of these was by Sir John Floyer, a physician of Lichfield, who, struck by the remedial use of certain springs by the neighbouring peasantry, investigated the history of cold bathing, and published in 1702 his “Ψυχρολουσία, or the History of Cold Bathing, both Ancient and Modern." The book ran through six editions within a few years, and the translation was largely drawn upon by Dr J. S. Hahn of Silesia, in a work published in 1738, On the Healing Virtues of Cold Water, Inwardly and Outwardly applied, as proved by Experience. The other work was that of Dr Currie of Liverpool, entitled Medical Reports on the Effects of Water, Cold and Warm, as a Remedy in Fevers and other Diseases, published in 1797, and soon after translated into German by Michaeb’s (1801) and Hegewisch (1807). It was highly popular, and first placed the subject on a scientific basis. Hahn’s writings had meanwhile created much enthusiasm among his countrymen, societies having been everywhere formed to promote the medicinal and dietetic use of water; and in 1804 Professor Oertel of Ansbach republished them and quickened the popular movement by unqualified commendation of water drinking as a remedy for all diseases. In him the rising Priessnitz found a zealous advocate, and doubtless an instructor also. The origin of hydropathy is thus to be traced to an English source and to the medical profession. The broad conception that water had curative relations to the whole realm of disease seems to have been first grasped by a Capuchin monk of Sicily, Father Bernardo, who, at Malta, in 1724, obtained results by iced water alone, which, according to Hahn, caused a great stir throughout Europe; but, owing to the excesses of his imitators, it was of no long duration. With this exception there is, as regards the remedial use of water, nothing in the history of medicine that approaches in completeness the system of Priessnitz, though much leading up to it can be discovered. Among most primitive peoples, indeed, both in the Old and in the New World, the existence of one kind or another of hydropathic practice can be traced; and the fathers of medicine made frequent reference in their writings to the employment of water. The warm bath came into use at an early period (see Baths, vol. iii. p. 434); and the clyster, shower bath, douche, plunge, wet compress, drop bath, head and foot baths, are mentioned from time to time, as also combinations of heat and cold and primitive modes of sweating, until, before the end of the 17 th century, all the processes of modern hydropathy, the wet sheet pack and induced cutaneous crisis alone excepted, had become known and were in a measure practised. Prominent in the roll of names associated more or less with the advocacy of water in earlier times are those of Asclepiades of Prusa (90 b.c.), surnamed Ψυχρολοντης (“cold bather”), Antoninus Musa (30 b.c. ), famed for his cure of Augustus by cold water (comp. Hoc., Epist. i. 15, 3-5), Galen (130 a.d.), Rhazes (923), Avicenna (1036), Cardan, and Van der Heyden. Raymond of Marseilles (1755) gained a prize for the best treatise on the applications of cold water in disease, and another prize essay by Marteau shows what knowledge of the subject prevailed in his time.

At Gräfenberg, to which the fame of Priessnitz drew people of every rank and many countries, medical men were conspicuous by their numbers, some being attracted by curiosity, others by the desire of knowledge, but the majority by the hope of cure for ailments which had as yet proved incurable. Many records of experiences at Gräfenberg were published, all more or less favourable to the claims of Priessnitz, and some enthusiastic in their estimate of his genius and penetration; and from these alone can a knowledge of his practice and views be obtained, not a line having ever been written by this singular man. To Captain Claridge was due the introduction in 1840 of hydropathy to England, his writings and lectures, and later those of Drs Wilson, Gully, and Edward Johnson, making numerous converts, and filling the establishments opened soon after at Malvern and elsewhere. In Germany, France, and America hydropathic establishments multiplied with great rapidity. Antagonism ran high between the old practice and the new. Unsparing condemnation was heaped by each on the other; and a legal prosecution, leading to a royal commission of inquiry, served but to make Priessnitz and his system stand higher in public estimation.

But increasing popularity diminished before long that timidity which hitherto had in great measure prevented trial of the new method from being made on the weaker and more serious class of cases, and had caused hydropathists to occupy themselves mainly with a sturdy order of chronic invalids well able to bear a rigorous regimen and the severities of unrestricted crisis. The need of a radical adaptation to the former class was first adequately recognized by John Smedley, a manufacturer of Derbyshire, who, impressed in his own person with the severities as well as the benefits of “the cold water cure,” practised among his workpeople a milder form of hydropathy, and began about 1852 a new era in its history, founding at Matlock a counterpart of the establishment,at Gräfenberg.

Whilst hydropathy as a system has been gaining favour with the people, and receiving ample acknowledgment from the more liberal members of the medical profession, individual measures have from time to time been advocated in the medical journals and adopted more or less widely in particular diseases. Brand of Berlin, Räljen and Jürgensen of Kiel, and Liebermeister of Basel, between 1860 and 1870, employed the cooling bath in abdominal typhus with results which, after every deduction on the score of defective classification had been made, were striking enough, and led to its introduction to England by Dr Wilson Fox, whose able monograph commanded general acceptance. In the Franco-German war the cooling bath was largely employed, in conjunction frequently with quinine; and it now holds a recognized position in the treatment of hyperpyrexia. The wet sheet pack has of late been much used in fevers of all kinds both in private and hospital practice; and the Turkish bath, introduced about twenty-four years ago by Mr David Urquhart on his return from the East, and ardently adopted by Mr Barter of Cork, has become a public institution, and, with the “morning tub” and the general practice of water drinking, is the most noteworthy of the many contributions by hydropathy to public health.

The theoretical basis of hydropathy is wide and fundamental enough to include within its scope all disease« Each individual cell of the mass constituting in various forms and combinations the human body being in its growth and function dependent on and regulated by the nervous and vascular systems, themselves cellular, and every derangement of these cells originating in or being.attended with a derangement of their nervous and vascular supply, and that supply being powerfully and in quite diverse ways influenced by heat and cold,—all morbid conditions of the economy may be influenced materially by the regulated employment of heat and cold, which are entitled therefore to rank as powerful factors in therapeutics.

Hydropathy insists in quite a special way on the necessity of regarding disease first in relation to its cause. It next requires that whatever assistance may be afforded to the vis medicatrix naturoe should in the first place be similar in kind (⅛'.e., should be natural or physiological), rather than alien to it and drawn from sources remote and strange; and, while proceeding on lines which have been common to all medical practice from an early period, it does so by agents hitherto strangely neglected, though not unknown, and effects its purpose in ways less open to objection than those it would displace. For example, when local depletion is required, as of the lung in pneumonia, or the brain in haemorrhagic apoplexy, the final withdrawal from the general circulation of a quantity of blood is deprecated as unnecessary for the attainment of the object in view, and prejudicial in the after period of convalescence. Hydropathy substitutes a diversion to parts indifferent, as the extremities and general cutaneous surface, and so material and sustained as tobe much more effectual; while at the same time it holds in reserve the abstracted blood to perform its part in the restoration of strength. Where purgation is employed to derive blood from the brain, liver, or kidneys, a highly sensitive and vital membrane is more or less injured thereby, and convalescence proportionately imperilled. Hydropathy selects the skin as more accessible than the mucous membrane of the alimentary tract, more serviceable also, and less, if at all, susceptible of injury, either temporary or permanent. The skin can with safety be used for counter-irritation, and is a reservoir of capacity almost unlimited, into which to divert the excess of blood from the brain or other part, while for purposes of excretion it is not inferior to the bowels themselves, and, unlike the latter, is left even more efficient than before. In the febrile state, a reduction of pulse and temperature, and relief from pain and sleeplessness, were commonly attempted, at the period when hydropathy was introduced, by depressants, as antimony, ipecacuanha, and perhaps large doses of alcohol, in combination with sedatives, as opium and chloral. Impaired digestion and depressed vitality were results in some measure inevitable, and always of moment, especially in the more protracted fevers, where recovery becomes a question often of simple physical endurance. By means of the wet sheet pack, cooling compresses, spongings, and allied measures, these ends are attained with comparative ease, certainty, and simplicity, and with entire freedom from objectionable secondary effects.

The agents of hydropathy are at once simple and complex,—simple in their elements, and complex in their combinations and modifications. They afford the physician a series of effects almost infinite in variety, both in kind and in degree, both immediate and remote. According as heat and cold are used in their extreme or their intermediate degrees, singly or in combination, successively or alternately, momentarily or continuously, dry or moist, and according as the primary action is utilized or the secondary, do their effects differ. The direct or primary effect of cold is to depress, cool, and deplete the part concerned. If its exhibition is brief, reaction (an important factor in hydropathic practice) quickly establishes an opposite condition, stimulating the part, and determining an increased flow of blood to it, with increase of its temperature and vital activity. If it is continuous, the primary depression is maintained, and the revulsive or secondary effect delayed or averted. The direct effect of heat is to increase the amount of blood present; but if the exhibition is brief, and evaporation is permitted, the contrary effect is produced, viz., depression, coolness, and depletion; if it is continuous, the primary effect is preserved. Thus with truth it may be said that cold heats and heat cools, while the converse holds good, and that by simple variations of detail. From the intermediate temperatures (80° to 100°) simple sedative effects are obtained, with absence of secondary or revulsive effects in proportion as the temperature of the part is approximated to. Results vary also according to the heat of the subject. In local inflammations, continuous cold benumbs and contracts, continuous heat soothes and relaxes. Momentary cold excites, heats by reaction, and intensifies inflammation; while momentary heat soothes and ultimately cools the inflamed part by the after evaporation. In the earlier stages and acute varieties of inflammation, therefore, continuous cold or transient hot applications are appropriate, and brief applications of cold in the later, congestive, and chronic forms. But where the local inflammation coexists with general feverishness, continuous cold as the local application is preferable, helping, as it does, to reduce the general exaltation of temperature. In collapse the low general temperature makes heat the best local application. On internal parts the application of heat and cold externally has definite therapeutic effects either identical or opposite (as remarked by John Hunter) through reflex or sympathetic nervous action. Through the vascular system also remote effects are produced, as in heating the lower extremities to derive blood from the brain. The counter relation also of the entire cutaneous surface to the internal organs, as the kidneys and alimentary mucous membrane, is, in hydropathy, largely utilized for remedial purposes. This sympathy is familiar enough in the etiology of disease, which may be said likewise of all the physiological laws applied to curative purposes in hydropathy.

The appliances and arrangements by means of which heat and cold are brought to bear on the economy are—(a) Packings, hot and cold, general and local, sweating and cooling; (δ) hot air and steam baths; (c) general baths, of hot water and cold; (d) sitz, spinal, head, and foot baths; (e) bandages (or compresses), wet and dry; also (∕) fomentations and poultices, hot and cold, sinapisms, stupes, rubbings, and water potations, hot and cold.

(a. ) Packings. —The full pack consists of a wet sheet enveloping the body, with a number of dry blankets packed tightly over it, including a macintosh covering or not. In an hour or less these are removed and ageneralbath administered. The pack is a derivative, sedative, sudorific, and stimulator of cutaneous excretion. There are numerous modifications of it, notably the cooling pack, where the wrappings are loose and scanty, permitting evaporation, and the application of indefinite duration, the sheet being rewetted as it dries; this is of great value in protracted febrile conditions. There are also local packs, to trunk, limbs, or head separately, which are derivative, soothing, or stimulating, according to circumstance and detail.

(δ.) Hot air baths, the chief of which is the Turkish (properly, the Roman) bath, consisting of two or more chambers ranging in temperature from 120° to 212° or higher, but mainly used at 150° for curative purposes. Exposure is from twenty minutes up to two hours according to the effect sought, and is followed by a general bath, and occasionally by soaping and shampooing. 11 is stimulating, derivative, depurative, sudorific, and alterative, powerfully promoting tissue change by increase of the natural waste and repair. It determines the blood to the surface, reducing internal congestions, is a potent diaphoretic, and, through the extremes of heat and cold, is an effective nervous and vascular stimulant and tonic. Morbid growths and secretions, as also the uraemic, gouty, and rheumatic diathesis, are beneficially influenced by it. The full pack and Turkish bath have between them usurped the place and bettered the function of the once familiar hot bath. The Russian or steam bath and the lamp bath are primitive and inferior varieties of the modern Turkish bath, the atmosphere of which cannot be too dry and pure.

(c.) General baths comprise the rain (or needle), spray (or rose), shower, shallow, plunge, douche, wave, and common morning sponge baths, with the dripping sheet, and hot and cold spongings, and are combinations, as a rule, of hot and cold water. They are stimulating, tonic, derivative, and detergent.

(<Z.) Local baths comprise the sitz (or sitting), douche (or spouting), spinal, foot, and head baths, of hot or cold water, singly or in combination, successive or alternate. The sitz, head, and foot baths are used “flowing” on occasion. Rapid alternations of hot and cold water have a powerful effect in vascular stasis and lethargy of the nervous system and absorbents, yielding valuable results in local congestions and chronic inflammations.

(e.) Bandages (or compresses) are of two kinds,— cooling, of wet material left exposed for evaporation, used in local inflammations and fevers; and heating, of the same, covered with waterproof material, used in congestion, external or internal, for short or long periods. Poultices, warm, of bread, linseed, bran, &c., changed but twice in twenty-four hours, are identical in action with the heating bandage, and superior only in the greater warmth and consequent vital activity their closer application to the skin ensures.

(∕.) Fomentations and poultices, hot or cold, sinapisms, stupes, rubefacients, irritants, frictions, kneadings, calisthenics, gymnastics, electricity, &c., are adjuncts largely employed in hydropathic practice. Water drinking, while still an important factor in hydropathy, has declined somewhat since the early times of the system.

But that which has from the first distinguished modern hydropathy, and still makes its strict practice a thing apart, is the “crisis” so called. It is related of Priessnitz that, when a boy'of fourteen, and treating a sprain, as was the native custom, with wet cloths, he observed an eruption appear beneath them, with immediate recovery of the part. Gradually the significance and wider application of this eruption dawned upon him, until it came to hold so prominent a place in his practice as to be regarded by many as his greatest discovery. The eruption coinciding in point of time with recovery as a rule, it was called the crisis, involving doubtless a reference to the term as used by Hippocrates and his successors. But with Priessnitz crisis attained a higher rank, a wider application, and a more definite character. He first showed it to be producible at will under given conditions of the patient, and amenable to direction and control. This eruption, it is claimed, appears only in morbid states of the blood (cachexia) resulting from derangement or defect in the organs of assimilation or excretion or both {p.g., gout, rheumatism), or from the presence of a specific poison (e.g., syphilis). The continuous application to a given tract of skin of the heating bandage or poultice (mediums merely for the exhibition of warmth and moisture) stimulates, in a cumulative way, its vascular and nervous activity, and leads, it may be in a few days or weeks (in some cases hours, in others months), to an eruption, papular, then pustular, and ultimately resolving itself into a suppurating surface commensurate with the area covered by the bandage. There is, in the latter stage, a copious discharge of yellowish-green pus, usually foetid, varied occasionally with patches of brown, blue, or metallic green, and accompanied with itching, sometimes intense. The general temperature is not, as a rule, disturbed; the pulse, except perhaps for the first day or two, falls, if previously quick, to a natural rate; the weight and strength, in the most favourable cases from the outset, and in the rest later on, increase, and it is not uncommon to find the anomaly of a patient exulting in freedom from suffering and a return of the impulses of health simultaneously with the appearance of an extensive inflammation of the skin. The applications, continued without intermission and unaltered (save as cleanliness requires) for weeks or months, according to the nature of the case, are at last no more stained with pus but with serum simply; and finally, still without change of application, the skin will heal, or, at most, show a little psoriasis, pityriasis, or eczema, or, it may be, but a faint tinge of red. The bandages are then withdrawn. The original symptoms meanwhile have disappeared with more or less celerity and completeness; and with the eruption has departed the disease that called for it and made it possible. Strength grows apace, no longer taxed by disease or crisis, until recovery in appropriate cases is absolute and secure.

Occasionally the cutaneous inflammation extends in the form of psoriasis, eczema, sudamina, a papular rash, or a succession of boils, invading parts untouched by the wet compress. This is called a general crisis; it usually occurs in the last stage of the local one, sometimes after it has ceased, and is advantageous and transient. Debility, whether pre-existing or consequent on the crisis, may call for some modification of its severity and duration, whether by instalments at proper intervals, or curtailment in the later stages, the natural emunctories being relied on to complete the work of Surification at greater leisure. A residuum of incurable organic egeneration, as of the kidneys or liver, may likewise put limits to recovery, and provide perpetual material for crisis until the...