This article is taken from book by prof. George Abbott, published in 1914 in USA. We would like to present it to the bigger group of readers, especially when it is very difficult to be found anywhere. Therefore we took this opportunity to present an interesting matter as seen back in 1914. Still some parts of this article are valid, and hydrotherapy as presented here is being used in spa treatment.



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Prof. George Knapp Abbott

Published 1914

The basic principles of hydrotherapy are found chiefly in an explanation of the effects of heat and cold. Viewed in this light, the science is that of thermotherapy. Effects similar to those produced by thermic impressions can be obtained by sunlight, friction, percussion, and in fact, all physiologic agents. This is most notably true of light, many of the physiologic effects of which run parallel with those of hydrotherapy. In fact, thermic and actinic energies are so closely related that they overlap each other in the visible spectrum. From the lowest limit of the scale of energies, up through electric energy, heat , light, and actinic rays to radium emanations and the X-ray, there is laid out before the physician a greater supply of efficient curative means than can be found anywhere else in the whole realm of therapeutics.

Therapy From Within: Those agents which, by their toxic action, arouse the body to resist their intrusion, cannot be classed as physiologic means. They excite abnormal and unusual activities which are largely directed against the toxic agent itself, rather than heightening the normal activities which keep the body in health and repel the onset of morbid processes. Merely to relieve temporarily a distressing condition, without enabling the body itself to overcome that condition, is doing no permanent good. The sick cannot always be applying special means. After recovery, they must depend upon the natural surroundings and ordinary agencies which keep the body in health. For example, to relieve pain by cocaine, an ice bag, pressure, or a fomentation is productive of no lasting good, unless that cocaine, ice bag, pressure, or fomentation cause the body to overcome the condition producing the pain; and its repeated application brings about such a change that the pain (or diseased condition) does not reappear after the curative agent is withdrawn. The body must be made to “cure” itself. The restorative power lies in nature. The natural God-given forces must be rejuvenated. The power from without must produce or arouse power from within.

Warm and Cold-Blooded Animals: The reason that thermic applications and impressions are so powerful in arousing body functions lies in the fact that life activities are carried on only within a certain limited range of temperature. With regard to body temperature, there are two general classes of animals, viz., the warm and the cold-blooded.

The temperature of so-called “cold-blooded” (poikilothermic) animals rises and falls with their surroundings. The organism is not injured by comparatively wide variations. The frog, for example, is lively in water at 70 F, and sluggish in water at 45 F, but it nevertheless lives and remains normal in either. These variations do not seriously depress vital activities. The organism is able to withstand such radical changes in the temperature of its blood and body generally, without this change being inimical to its life. The body temperature of these animals remains slightly above that of the cold water they may be in and slightly below that of warm water. Cold-blooded animals are principally aquatic and amphibian.

Certain other animals maintain a constant temperature under varying conditions. The surrounding air, whether hot or cold, does not materially alter their body temperature. The heat mechanism is so nicely adjusted that more heat is produced when the surrounding medium is cold, and less when the air or other medium is hot. This class of animals is called “warm-blooded” (homeothermic) because of the constant temperature at which their blood is kept. Arterial blood is slightly warmer than venous. The ordinary limits for man are about 101- 103 F.

Organs of constant activity, such as the heart, liver, and brain have a temperature 2-4 degree higher than the average of the blood stream. At ordinary room temperature, the uncovered skin has a temperature of from 92-95 F. This fact is of importance in the administration of neutral baths. The water should be 1 or 2 degree higher than that of the general skin temperature. This secures a full sedation by adding a slightly relaxing effect. As noted above, the internal temperature of warm-blooded aimals is comparatively a fixed point, or varies within only very narrow limits, not more than one degree in health. Any radical or prolonged departure from this fixed point (98.6 F by mouth) interferes with vital functions.

Intrinsic Effects: When the body becomes thoroughly chilled, as by a long ride in the cold, the pulse and respiration are slowed, the circulation is less rapid, the nerves benumbed, the muscles respond sluggishly and clumsily, the finer skilled movements are impossible, digestion is retarded, the body temperature is lowered. Cold is, therefore, in itself, a vital depressant, i.e., it retards vital processes. This is its intrinsic effect. Kellogg records an experiment in which immersion of the body in water at 55 F for ten minutes reduced the pulse rate from seventy-six to fifty per minute. Another, in which twenty minutes in water at 45 F, the patient being rubbed continuously, reduced the pulse rate from eighty to fifty-eight. Both experiments were upon healthy persons. In another experiment, exposure to cold showed tactile sensibility decreased. Before the exposure, the points of an esthesiometer were detected as two separate points at a minimum separation of 2 mm. After five minutes immersion in water at 40 F, the minimum distance was increased to 6 mm. Another, in which five minutes in water at 68.4 F, reduced the body temperature .8 F. These data serve to make definite facts with which we are acquainted in a general way only.

It will be seen from this that an overactive process may be retarded and brought back toward the normal by an application of cold, continued until its intrinsic effects are manifest. The longer the duration of the cold application, the greater its effect. The same is true of the degree of cold. The lower the temperature, the more pronounced the effects.

While cold retards, heat stimulates vital activities. We know what it is to experience the vivifying effects of the warmth from a fire or sunlight after being in very cold air for some time. The circulation is quickened; the heart beats faster; respiration is more rapid; nerve sensibility is heightened; muscular action is quicker, more certain, and precise; and digestion proceeds more rapidly. In watching the activity of the white blood cell under the microscope, the stage must be kept warm or the movements will cease. The amoeba, paramecium, and other one-celled animals exhibit their peculiar movements only in the presence of a certain amount of heat. When cold, their movements cease entirely. Cold, per se, decreases oxidation and metabolic activities; heat increases the oxidizing capacity of the tissues and metabolic activities are hastened.

When the body is overheated, its function are abnormally increased and, if long continued, permanent injury may result. When heated only to a slight degree, however, sluggish activities are whipped up and, if the applications of heat are repeated at intervals, the retarded functions tend to return to normal.

Reaction: The most interesting and phenomenal results of hydrotherapy are due to that complex process- reaction, i.e. the part which the body itself takes in its own recuperation and healing. This interesting phenomenon, in its entirety, is observed only in homeothermic animals. Cold-blooded animals, instead of reacting to their external medium, are subject to the vicissitudes of their environment. On the contrary, warm-blooded animals maintain more or less uniformity of function because of the perfect control exercised over vital processes by the nervous system. This control is more highly developed and complicated than in poikilothermic animals.

We have seen that the influence of cold is to depress vital activities; that is, if continued long enough, its intrinsic effect is manifest in depression. But let us notice the effects of a brief application of cold. A plunge into cold water increases the pulse rate and force, the skin becomes reddened because of a quickened peripheral circulation, and the respiration is deeper. The muscles are energized so that their capacity for work is increased. These heightened activities continue for a time, gradually returning to normal. This is reaction- which may be defined as a group or series of changes inaugurated by the body because of some disturbing external agent. More briefly, it is the response of the organism to an external agent.

Rationale of Reaction: The explanation of these tonic and stimulating effects lies in the recognition of cold by the body as an agent which will depress its functions. Even though the contact be too brief to actually bring about this result, it immediately increases its activities in order to counteract the anticipated depression. The body tends to resist or overbalance attempts to alter its temperature. In doing so, it is said to react against this change, or attempted change. Cold, in and of itself, causes depression. But the attempt on the part of the body to resist this depression results in heightened activity. This is spoken of as the reaction or reactionary effect. It is always the opposite of the intrinsic effect. Some very common examples of this will serve to illustrate the principle. An ice bag applied over the heart for five minutes slows the pulse rate; while slapping the chest with a cold wet towel, or the brief application of a cold douche to the chest, increases both the pulse and respiration rate. A long cold application, as a cold tub bath, lowers the body temperature, while a short cold application, as a cold plunge or cold douche, soon results in an increase of body temperature.

If the external cause is long continued, the reaction may not be apparent, may be lost, or obscured by the intrinsic effect. The body reacts or attempts to react to even prolonged application of cold, so that what is seen as a result of these long applications is really a mixture of the intrinsic and reactionary effects. As to which shall predominate depends upon the intensity and duration of the application. With the more prolonged application, the reaction is suppressed or obscured; while in those of intermediate duration, we often see as much of one as of the other.

With heat, as used in actual practice, we observe its intrinsic effects when the hot application is short, i.e. of brief duration. The first effect of heat is that of a stimulant and tonic; but, if long continued, depression results. This depression is, by some, termed “a reaction.” Baruch objects to this term as applied to heat. If we define reaction as the vital response to an external force, or the attempt on the part of the organism to counteract an external agent, we can see no great objection to the term, or to saying that the reaction to heat is of an atonic nature.

Tonic effects are obtained from the: Intrinsic effects of heat (short); reaction to cold (short)

Retarding and depressant effects are obtained from the: Reaction to heat (long); intrinsic effects of cold (long).

It must not be concluded from the above grouping that the depressant effects of a long cold application (intrinsic) and those of a long hot application (reaction) are identical in nature. The depression is manifest in different ways. With cold, the depression is in the nature of a simple retardation of vital functions, whereas with the heat the depression is manifest chiefly in the nervous and muscular systems, and is perhaps best described as atonic. That this is largely a nervous phenomenon is apparent from the fact that a vigorous cold treatment following prolonged heat often quickly restores the patient to a normal condition.

Abrams makes the following statement: “Respecting the physiologic effects of heat, it suffices to say, that a prolonged application of a high temperature is primarily an excitant, and secondarily a depressant; a brief application, however, is strongly excitant and the depressing effects, if any, are imperceptible.” In discussing the effets of thermic stimuli (on secretion) Pope says, “In general terms, it may be stated that brief application of thermic stimuli, whether hot or cold, stimulate secretion, differing in degree rather than in toto; long-continued applications depress.”

Phases of Reaction: There are two important phases of reaction, viz., the circulatory and the nervous. The circulatory is most apparent and is that by which we judge of the completeness of reaction. The skin should become ruddy and warm. The patient feels a warm glow over the entire skin surface. There should be nothing of stasis, no cyanosis, or goose flesh. The skin should be smooth, soft, and pliable. The nervous reaction is appreciated not only by the patient but by the observer. The dull, listless appearance of the eye and countenance generally, gives way to a decided brightening. If there is delirium or stupor, as in typhoid, pneumonia, etc., it may be replaced by quiet sleep. In fact, the salutary effects are visible in all the nervous functions of the body. With a neurasthenic patient, the feeling of languor, restlessness and weight in the abdomen is replaced by that of vigor and exhilaration. Another phase of reaction is that termed thermic. It is the response of the heat mechanism to stimulation. It is of less practical importance since it cannot be conveniently utilized in judging of the completeness of reaction.


Suppressed Reaction: It is often desirable to suppress or limit the reaction arising from some application. This is especially true with long cold applications which are designed to delay vital activities or reduce fever. Of course, the body attempts to react to all such measures, as has been mentioned. The reaction may be limited, e.g. by a cold application such as ice bag to a part. The nervous excitability is lessened by the continuous and severe cold, so that the phenomena of reaction do not appear in their entirety and completeness. In the case of Brand bath, the exciting stage soon gives way to a slower heart beat, slower and deeper respiration, etc., by reason of the continuance of the cold. In general, the suppression of the reaction depends upon the intensity of the cold and its duration, being greater with the lower temperature and with the prolonging of the application.

Repeated Reaction: In the giving of alternate hot and cold treatments, the body is called upon to react several times. After two or three applications, the reactions are less complete. The oscillatory changes occurring in the blood vessels become less and less in amplitude after each succeeding application. In order to produce complete reactions where the applications are repeated, it is necessary to increase the intensity of the stimulus. This may be done in the case of alternate hot and cold by using a higher temperature for the hot and a lower temperature for the cold, or by adding mechanical stimulus.

Incomplete Reaction: Applications not properly suited to the reactive ability of a patient will result in an incomplete reaction. Should this occur, the patient experiences quite unpleasant symptoms, such as chilliness, shivering, cold feet, a feeling of fullness in the head, and even faintness and nausea. These are due mostly to the internal congestion which has not been relieved or has been made more intense.


Age and Vitality of the Patient: In either extreme of life, the ability to react is quite limited. Neither infants nor aged persons bear cold treatment well. We have treated persons in advanced life who were utterly unable to react to even cool water as applied by the wet hand rub, and who invariably chilled after a cold mitten friction.

In certain diseases or states, the vitality is so reduced as to render reaction extremely difficult. This is true of nearly all those diseases which produce a profound asthenia. In anemia and extreme emaciation, the same conditions prevail. In all such cases, it is necessary to thoroughly warm the body previous to the cold application and give vigorous friction during and following the treatment. Even these means will not always insure a reaction.

Exercise: sufficient to warm the body, promotes reaction. This is true whether taken before or after the treatment. It quickens the circulation and brings the blood to the surface. Body heat is increased so that the surface blood vessels become dilated in order to increase heat elimination. Fatigue is not conducive to completeness of reaction. In case it is necessary to treat persons who are fatigued, a short hot application should be given first, quickly followed by some short but very vigorous cold treatment, accompanied by friction or percussion.

The Warmth of the Body: When the body is warm, reaction appears promptly. The internal heat of the body may be ever so much and yet reaction be impossible, if the skin is cold and clammy, pale, cyanotic, or goose flesh in appearance. The skin should be warm and, if possible, ruddy before cold applications are used. In case it is not, some sort of hot treatment should be used first, in order to draw the blood to the skin. The air of the room in which the patient is treated should be warm and he should remain in a warm room after treatment until reaction is complete. It may be necessary to give a drink of hot water in order to warm the body. More essential than all of these is the warmth of the feet. It is impossible to secure full reaction or the best possible results, if the feet are cold. It should, therefore, be a general rule that the feet should be warmed by a hot foot bath or alternate hot and cold foot bath or hot foot pack, previous to any and all treatment. In the giving of even an enema, this is necessary. After treatment it may be necessary to provide the patient with additional covering, either in the form of bedding or clothing, in order to secure full reaction.

Psychic Attitude: It is difficult to produce complete reaction in a patient that dislikes the measures used. That the mind does exercise an inhibitory influence over body functions cannot be doubted by those whose practice brings them in contact with profound neurasthenia. Those under great mental strain, worry, or anxiety, react poorly.

Character of Treatment and Mode of Application: In all cases where reaction is likely to be tardy, the cold treatment should be preceded by a hot treatment. In ordinary cases, the hot application should exceed in duration the cold application. It should thoroughly warm the body and make the cold a welcome change. The reaction is more prompt in its appearance if extreme cold is used and accompanied by friction or percussion. The colder the water, the greater the reaction. The cold treatment should be given quickly. The treating of one part at a time favors the quick appearance of the reaction. The larger an application or more general the surface treated, the less promptly will the reaction appear. Friction with the dry hand or a rough towel, following the drying, enhances the reaction. Percussion has the same effect. The drying from sprays and general applications of water should be done as quickly and as thoroughly as possible. If moisture is left on the surface, the resulting evaporation cools the body and reaction is delayed. The patient should be dried in a warm room near the place where the last application of water was made. To properly shape circumstances so as to favor reaction, requires much care and forethought on the part of the attendant nurse. A little carelessness may undo much or all of the benefit which should accrue from a given treatment.

Test of Reactive Ability: Ability to react to cold application varies with the climate of usual residence, state of health, occupation, and habits of the patient. As to the reactive capacity, little can be determined by questioning the patient. Often those who say they are unable to take cold baths react as well or better than those who affirm their ability to react. What one calls very cold another regards as only cool. Some persons consider that they have been taking cold baths when bathing in water at 90-95 F. The response of a patient with anemia is usually in direct proportion to the degree of anemia. The state of the vasomotors and the readiness with which they react to mechanical stimuli serve as a rough test of the ability to respond to cold treatment. This test is mentioned by nearly all writers on hydrotherapy. Baruch makes the statement:

“I have found that the response of the cutaneous circulation to mechanical excitation furnishes an index to the probable reactive capacity of the patient. Passing the back of the nail of the index rapidly but gently across the abdomen, and increasing the pressure of the nail with a second stroke parallel to the first, induces a more or less deep reddening of the irritated skin. The rapidity with which the red line develops after the nail is removed, and the pressure required to produce it, afford the trained eye a crude, but fairly correct test of the patient’s reactive capacity. By applying this test frequently before each procedure, one may readily train the appreciation of this test and thus avoid the necessity of slow development of the reaction by gradual increase of the intensity of the treatment which the author adopts in most cases.”


Heat and cold are relative, not absolute, terms and must need to be defined. This cannot be done with accuracy, since patients differ in their toleration of heat and cold. What one designates as very cold may be only cool to another. The extent of skin surface exposed to thermic stimulation also makes a difference in the degree of the temperature impression received. For example, immersion of the hand in water at 70 F will give an impression of cold; but, if the entire body is immersed, the water will seem very cold. Again, a full tub bath at 105 F will seem very hot; while, if only one hand is immersed, the impression received is that of only moderate heat. The most satisfactory way of designating temperature is to define the limits in terms of degrees. The table below has been found practical. The designations above neutral are those that would be used for full tub baths; those below neutral are such as would be used for partial immersion.

Very hot: 104 and above

Hot: 100-104 F

Warm (neutral, 94-97 degree): 92-100 F

Tepid: 80-92 F

Cool: 70-80 F

Cold: 55-70 F

Very Cold: 32-55 F