PHYSIOLOGICAL EFFECTS OF WATER
The effects of water upon the human system are the results of the operation of its physical properties in conjunction with the vital forces. As with all other agents, its effects may be either local, or general, according to the mode of application. Different effects are also produced according as the administration is internal or external. Many other modifying circumstances, as age, sex, and physical condition, affect the results in a greater or lesser degree.
Water affects the system through three different means; viz: -
WATER AS A DILUENT
Water is received into the system by absorption, either through a mucous membrane, or through the sin. It usually enters through the medium of the stomach and intestinal canal. When received into the blood, it of course increases its volume, and produces an increased fullness of the circulatory vessels, which are never distended to their fullest extent, and hence allow room for change in the volume of their contents. The blood is necessarily rendered more fluid, and if previously in any degree viscid, its circulation is quickened by its dilution.
THE EFFECTS OF THE SOLVENT PROPERTIES OF WATER
With the exception of air, water if the most transient of all the elements received into the body. It is eliminated by the skin, the lungs, the kidneys, and the intestines. By its solvent action, it dissolves the various poisonous products of the disintegration of the tissues. The volume of the blood being increased, more water comes in contact with the debris contained in any part, and, in consequence, the same undesirable products are more perfectly removed. The increased amount of excrementitious matter in solution is brought in contact with the various depurating organs, producing, notable, the following results: -
1. An increase of the urinary excretion. It is an important fact that this increase does not consist in the addition of water merely, or dilution, bu that there is also an increased amount of urea, the chief excrementitious principle removed from the blood by the kidneys.
The removal of clogging matters from the system in this manner allows greater freedom of vital action, so that the activities of the body are quickened, and both waste and repair, disintegration and assimilation, are accelerated.
The use of water thus hastens all the vital processes by increasing the change of tissue. This result is of course chiefly obtained by employing it as a drink. The experiments of Liebig fully confirm this view. He expressly mentions the free use of water as one of the means of accelerating viatal change. Prof. John B. Biddle, M.D., in his Materia Medica, states that it promotes both the metamorphosis and construction of tissue, from which fact he attributes to its valuable curative properties, as an alternative, when the removal of a morbid taint is desired, as in certain venereal diseases.
EFFECTS RESULTING FROM THE MODICATION OF TEMPERATURE
Perhaps the most important, certainly the most common, effects of water upon the living organism are those which result from its modification of the temperature of the body in its various modes of application. These effects vary greatly according to the temperature, and the duration of the application. General and local applications also differ in their results.
It should be remarked that all of the effects of water are really the results of the vital resistance of the system in its attempts to remove abnormal or unusual conditions, or to aaccommodate itself to new circumstances.
Baths are divided into six classes, according to their temperature, as follows: -
...33 to 60 degrees F.
For the sake of simplicity, we will consider the effects of water applications under three heads; viz., cold, warm, and hot.
1. THE COLD BATH
Under this head we will consider applications of all temperatures below 85 degrees F. Cold or cool water, applied to any portion of the body, causes instant contraction of the small arteries of the part, through its influence upon the sympathetic or vasomotor system of serves. So long as the application of the unusual temperature is continued, the vascular contraction is maintained, and the part seems nearly bloodless. If the cold is below 33 degrees F., and is long continued, destruction of the tissues, by freezing, will result.
If a moderately cool or cold temperature is maintained for some time, the blood-vessels of the part are more or less permanently contracted, and the blood supply thus lessened. If, on the other hand, the application I very brief, the contraction of the vessels is only momentary, and is followed by a proportionate degree of relaxation, and a corresponding increase in the supply of blood to the part.
A very cold bath applied to any considerable portion of the body, and continued more than a very brief time, produces headache, dullness, sometimes nausea and vomiting, loss of sensibility, and other unpleasant and painful symptoms.
It is thus seen that the effects of cold are quite different exactly opposite, in fact as the application is a prolonged, or a brief one. The long application produces effects in some degree permanently sedative, while the brief application is followed by a momentary condition which may be termed shock, and which is usually followed very quickly by a reaction analogous to stimulation when produced in any other manner.
EFFECT OF COLD UPON THE PULSE. - The experiments of Drs. Currie, Bell, and others, show conclusively that the cold bath has the uniform effect of diminishing the frequency of the hearts action from ten to twenty beats in a minute below the usual standard. Upon the first application of cold, there is a slight increase in the rate of pulsation; but this soon subsides, and is succeeded by a marked diminution. The ultimate effect is the same, whether the application is made at its maximum degree of severity of not; but if the application is first warm, being gradually reduced in temperature, the result is reached without the occurrence of the unpleasant shock, or feeling of chilliness, which attends the sudden application of cold, especially in persons of delicate nervous sensibilities. The amount and after duration of the diminished rate of pulsation depends upon the temperature and duration of the bath. In health, it does not commonly extend beyond a few hours at most.
EFFECT OF COLD UPON TEMPERATURE. It was also shown by the same experimenters that the temperature of the body is reduced proportionately with the action of the heart. The natural temperature, as shown by a thermometer placed in the axilla, is 98 degrees F. During and after a cold bath, the thermometer applied to the same part, indicates from one-half a degree to five or six, or even more, degrees, diminution of temperature. In some cases the temperature continues to fall after the bath. The real temperature is lessened even though the skin may glow, and may seem to possess increased warmth. Cold and heat are, within certain limits, wholly relative terms to the nerves of sensibility. What is warm at one time may be cold at another, though the temperature remains the same. The same temperature may be warm to one hand and cool to the other. Temperature can only be accurately determined by the thermometer.
RATIONALE OF EFFECTS OF THE COLD BATH. The manner in which the cold bath produces the sedative effects noted, is apparently simple.
When applied locally, to a single organ or part, it diminishes the circulation in the part by occasioning contraction of the muscular coats of the arterioles, or small arteries.
Their caliber being thus lessened, they of course allow the passage of less blood, and the circulation in the part is diminished. There are, then, three causes for the decrease of heat; viz, -
When the application of cold water is more general, being made to the whole body, or to a considerable portion of it, the same effects are produced on a large scale. A large proportion of the small arteries of the body, being brought under the influence of cold, are made to contract, thus directly lessening the circulation, and so diminishing, also, the production of heat. Through the sympathetic system, the same effect produced upon the small arteries is produced also upon the heart, lessening the rapidity of its contractions. Again, it has been satisfactorily shown that the action of the heart is largely controlled by the action of the small arteries; so that we have abundant explanation of the decrease in the rate of pulsation Finally, we have a cold fluid in contact with a large portion of the body, abstracting heat by conduction, as well as lessening its production.
Thus we see that water, when applied at a proper temperature, is one of the most powerful means of depressing the vital activities of the body, diminishing circulation and animal heat as will no other agent.
2. THE HOT BATH
We shall include under this head applications of a temperature above 98 degrees F., the mean temperature of the body. As with the cold bath, the effects differ greatly according as the application is brief or prolonged. Local and general applications also differ in their effects.
A brief local application causes an increase in the circulation of a part which very closely resembles, perhaps is identical with, active congeston. The small arteries are distended, and the viatal activities and heat of the part are increased. The several effects eem to be little different from those resulting from the application of a mild sinapism. The action of the vital instincts is defensive in both cases.
When applied to special organs, special effects are produced.