WATER AND NEUTRAL ALKALIN SALTS

The deportment of these salts in the organism, as has been previously stated, is determined by a general salt-action on the one hand and on the other by a decomposition and the specific poisonousness of the ions. On their introduction into the stomach and intestinal canal this deportment is very considerably influenced by the different conditions of the absorption of the several salts.

The chorids, bromids, iodids, as well as the nitrates, chlorates, and iodates of the alkali metals pass very rapidly from the mucous membrane of the digestive tract into the fluids and tissues of the body, and can here, undisturbed, develop all their actions with the physiologic salts of the organism, and arrive for excretion in a relatively short time in unaltered condition, or partly in the form of reaction-products.

The absorption of the alkalin earths, on the contrary, takes place only very slowly and in small quantities.

The actions are principally confined to the intestinal canal in that they, through their molecular-physical properties, produce diarrhea and consequently constitute a special group of the cathartic salts.

In osmosis they always go with less rapidity through a closed membrane than the easily absorbable salts, and are inclined, as a rule, according to the researches of Hofmeister, 1888, to more easily precipitate colloid substances from their solution.

WATER AND EASILY ABSORBABLE NEUTRAL SALT GROUP

If solutions of different molecular concentration are separated from each other by membranes or similar partitions, which they stimulate by high pressure without, in turn, allowing filtration, then a movement through the membrane from the concentrated to the more dilute and "vice versa❞ takes place, the water passing from the dilute to the concentrated solution. The movement takes place to equalize concentration, which lasts until, in a unit of volume, each of the original solutions contains the same number of separate molecules or dissociated ions of the dissolved substances. This condition of equality is known as the isotony of solutions. If the membrane will only allow the passage of water and not the dissolved substances, then water passes through the membrane from the dilute to the concentrated, until isotony is obtained. Thereby the volume is increased, and when it cannot escape in the neighborhood, but is compelled to remain, it produces a hydrostatic pressure (dependent on concentration), which is called the osmotic pressure. Two solutions separated by an osmotic membrane are therefore isotonic, when they occasion the same osmotic pressure.

Solutions which are not isotonic can be called anisotonic; the more dilute the hypoisotonic, the more concentrated the hyperisotonic solution.

These osmotic processes and physical-tonic conditions play an important part in the organism, only here they are more extensive and complicated than has been described in the foregoing scheme, and therefore are difficult to observe and follow. Whereas the membranes and coverings of the living cellular elementary organs in osmosis are seemingly completely penetrated by water and readily by dissolved substances, others only pass with difficulty, and possibly not at all. To such a selection in the assimilation of substances on the part of the cellular organic elements a part of the processes can be referred; these, like glandular activity, are often supposed to be specifically vital. These conditions become the more complicated if we take into consideration that physical isotony need not of necessity be physiologic at the same time.

The first exists and the solutions are isotonic only when they contain the same number of dissolved molecules or dissociated ions, without being of the same substance in the different solutions. If in such solutions very different salts and other neutral substances be brought into plant cells, they remain entirely unaltered externally, whereas from hypoisotonic solutions. water passes into cells and the cell-membrane is removed from the protoplasm, a process which de Vries, 1884, has called plasmolysis. But in isotonic solutions the physical properties of the cells, (their expansibility), alone remains unaltered when the dissolved substances are unlike those of the cell-contents. In this case, according to the penetrability of the membrane, an exchange of the substances between the external solution and the cellcontents takes place, whereby the latter is altered in its composition and the vital condition of the cell is influenced.

The deviation from the normal, which the absolute or relative quantity of the dissolved substance in the elementary organs is subjected to under the influence of physiologic salt-solution, can hardly be considerable. Still, it is sufficient to cause death of tissue; also lesser deviations will occasion a marked alteration in the deportment of the function of the organ and in the metabolism, which can be easily brought about artificially by increased influx of water or salts, and thus in many cases can be used with advantage therapeutically.

WATER ACTION

The local action of pure water is principally one of the osmotic extraction and swelling of the tissues. If living organ-elements or lower organisms are brought into pure water free from salt, they quickly die, because salts and other soluble substances are removed in such enormous quantities that a continuance of life is endangered or arrested. In fact, fish die rapidly in oxygenated distilled water. (S. Ringer, 1883.)

Slight alterations in the concentration and composition of salt-solu

tions which permeate the tissues, give rise to functional and nutritive disturbances in the same.

Milder grades of this water-action come into practical consideration in water-cures, where pure thermal or other waters are ingested in large quantities for a long time.

By flushing out the stomach the superficial layers of epithelium are greatly swollen and extracted; thereby they are rendered incapable of life, and are exfoliated, a process which leads to a marked regeneration, whereby pathologically altered tissue-elements are replaced by normal, and diseased conditions of the gastric mucous membrane are often benefited, if not cured.

In bathing, on the contrary, a pure water-action plays but little if any part, because the water cannot penetrate or in any great degree alter the external cuticle. In warm-water baths the body not only does not take up the water, but through the escape of the latter through the skin the bodily fluids are decreased. L. Riess, 1887.

Only protracted baths cause a swelling of the superficial layers of the skin. These alterations take place more readily on diseased skin or when the external layers are removed from the epidermis in wounds or tumors. In such cases the influence of local baths is analogous to the effects on the stomach. An easier exfoliation of the altered tissue elements follows and the injured part remains protected from contamination through carriers of infection.

In regard to the absorption of water in the digestive canal which occurs very rapidly, the stomach seems to play little or no part. In fact here water serves as a hindrance to the absorption of other substances, such as sugar and peptone, since these are absorbed in relatively smaller quantities from dilute solutions than they are from concentrated, whereas in the bowel a less concentrated condition favors this process. Tappeiner, 1881; v. Anrep, 1881; Segall, 1888; Brandl, 1893; Mering, 1893.

The reason for the absorption of water in the bowel is not yet sufficiently known. Osmosis and endosmosis or dialysis cannot play a part here; they would not, for example, explain the thickening of the feces. Filtration will also not explain the absorption of the water, because it is not to be supposed that, with the susceptibility of the tissue a difference in pressure exists which is essential to filtration between the intestine and organs or blood.

It seems as little possible that through open stomata an excretion of water takes place through the digestive tract. If this were the case all fluids would be absorbed with equal rapidity. This does not take place, however, since a solution of sodium sulphate conducts itself entirely differently from a solution of common salt. On the contrary, the absorption of water in the intestinal canal and other mucous membranes can be viewed as a swelling process.

The parts of organs capable of swelling, coming in contact with water, take it up and give it up again in the form of serous lymph, or it is abstracted by the blood flowing by.

There seems to be no positive ground for including any particular vital force in the transport of this water. The blood does not alter its concentration much with the absorption of large quantities of water. It is therefore probable that the abstracted water, as also fluids injected into the blood, collect in the tissues, (Hamburger, 1890,) and then gradually reenter the lymph, and blood-channels, and are excreted through the kidneys. The excretion of water through the kidneys is due to the blood-pressure in the vessels of the glomeruli, and consequently can best be referred to filtration, in which the filter must be so arranged that it takes up the water but not the dissolved substances, and conducts it further, whereas these others are taken up by the epithelium in other parts of the kidney and are given off in the urinary canals. In this manner can be explained how, in the diuresis brought about by the simultaneous intake of common salt and large quantities of water, the osmotic pressure of the excreted urine can sink below that of blood. (Dreser, 1892.)

Sweating can only take place after the ingestion of large quantities of water, with the skin at the same time in a state of congestion, which for practical purposes is brought about by preventing cooling, or by raising the temperature of the neighboring parts, thus warming the surface of the body, whereby the vessels of the skin are widened, and possibly also increasing the function of the sweat-producing nerves.

Such water as is necessary to keep up the normal distention of the tissue and to dissolve colloid constituents of the body has but little to do with excretion through the kidneys. On the contrary, by increased administration the excess is rapidly removed. Thereby the percentage of solids in the urine falls, so that the latter, by drinking large quantities of water, can be greatly diluted. Pure water is easily excreted by the skin and lungs, and it is therefore advisable, in place of this, to select dilute salt-solutions if it is the purpose to render the urine less concentrated in reference to its general constituents, for example, uric acid.

The increased intake and excretion of water is associated with the appearance of large amounts of nitrogenous metabolic products in the urine.

In healthy persons, for example, after taking four liters of water in twenty-four hours the amount of urea in the urine is raised twenty per cent, whereas the uric acid entirely disappears. In this same experiment the quantity of sulfuric acid increased proportionately with the urea, so that the former under normal conditions as well as after the use of the water gave the proportion of 10 grams of urea to 0.60-0.68 grams of sulfuric acid. (Genth, 1856.)

It deals therefore with increased formation of nitrogenous metabolic products in consequence of excessive destruction of proteids and not only with an extraction of the tissue and an accelerated excretion of the urea already formed. The latter is therefore increased in amount when in consequence of a diminution of other secretions the amount of urea is increased abnormally. (Kaupp, 1856.)

However, this influence of water on metabolism in researches on animals is not a constant one and is dependent on the condition of nutrition of the latter, as in starving animals the destruction of the proteids seems to occur more easily. Further, the increased excretion of urea seems to be a transient one; it ceases often after a short time in spite of the continued administration of large quantities of water to dogs. (J. Mayer, 1880; and in man, Oppenheim, 1880.)

The preceding facts show that even with the passage of large quantities of water through the organism the nitrogen balance is finally reestablished under these conditions; however, the tissue should contain a much smaller quantity of nitrogenous material than before the advent of the water.

If such an alteration is produced under normal conditions, then it can be supposed that, with a methodic use of pure water in the form of indifferent thermal and cold springs, pathologic products will be more readily affected and brought to absorption in case they are subject to destructive metamorphosis at all. In this manner the beneficial result of drink cures in inflammatory and hypertrophic disturbances of nutrition of different kinds can be explained.

From the above it also follows that a beneficial result is not always to be expected. The special indications rest on an entirely empiric foundation and are therefore very uncertain. The supposition that in obese persons the storing up of fat is not favored by the free use of water and diminished by its limited use, is not corroborated by experiment in fattening animals; in this case but little water is given with the fattening food.

THE SALT ACTION

Salt action in the purest form is brought about only by the use of sodium. chlorid; but the other salts in a dissociated condition also influence more or less different parts of the nervous system.

Of the neutral salts which are readily absorbed, chlorid, bromid and iodid of potassium, and, in part also, the sodium compounds, have become of practical importance.

The salts and their concentrated solutions extract water from the tissue like any moist body by osmosis. Thus, if they belong to the sodium chlorid group, they rapidly penetrate the tissues in large quantities; the tissues then become poorer in water and richer in salts. Through both of these processes. to which usually a solution of cellular constituents and an independent ac