II. Review Of Physiological Investigations Concerning The Effect Of Thirsting On The Organism

The purely experimental studies that have been made on the effect of thirsting upon the organism need merely be mentioned in a cursory manner. Longet, Birsch-Hirschfeld, Chossat, Luciani, Bufalini, Scheffer, Schuchardt and Falck (26) have published such investigations; their chief task was to determine how long thirsting animals could survive. It was shown that the effect of thirsting was much more intense than the effect of fasting. The subjective tortures of thirst have been vividly described in the works of African explorers, e. g., v. Rohlf, Nachtigal and others, also in the work of Strübell (27). Pernice and Scagliosi (28) have performed pathologico-anatomic studies on animals dead from thirst; they found tissue atrophy and inflammatory changes in various organs and, in particular, a hemorrhagic form of glomerulo-nephritis.

Other investigations are concerned with the effect of thirsting upon the blood. A large number of the data submitted do not refer exclusively to changes in the blood in thirsting animals, but also in animals that were submitted to diaphoretic measures, that were artificially heated, etc. - all procedures that were intended to produce greater blood concentration, but that need not be discussed in detail in this place. To this category belong, e.g., the investigations of Lowy, Friedlander, Hammerschlag (29) and others. A study of Gurber (30), who found that in a thirsting frog the number of erythrocytes was increased, is concerned exclusively with the withdrawal of water, and so, also is that of Von Westendorf (31), who showed that in a thirsting dog the osmotic pressure and the specific gravity of the blood were increased; he also called attention to another interesting fact, viz., that the lowering of the specific gravity of the blood, which normally occurs after venesection, does not occur in a thirsting dog, because no water can be yielded to the blood from the dehydrated tissues of such an animal.

The investigations of Nothwang (32) lead to the studies on the effect of thirsting on metabolism; in his paper a summary of the older literature on the subject may also be found.

Nothwang made his studies on pigeons that were fed on air-dried peas. He calls attention to the experimental difficulties of studying the effect of thirsting on animals; for, as thirsting animals soon refuse to eat, the effects of fasting are soon added to those of thirsting. In inanition from lack of food the tissues of the organism itself are concerned, and in process of degradation the latter split off water. In this sense we encounter the paradoxical phenomenon that fasting in part neutralizes the effect of water-withdrawal, and that, consequently, the animals live longer.

Consequently the pigeons that Nothwang fed on dried peas survived on an average for 4 1/2 days, whereas the animals studied by Falk and Scheffer, that received much less pabulum, as well as the animals of Schuchardt, lived from 11 to 12 days.

Death occurred when about 22 per cent, of water had been lost; the existence of the animal may be said to be threatened as soon as the loss of water reaches approximately 11 per cent.

Landauer (33) studied the question from other points of view that interest us; his results form the basis of many of the conclusions arrived at by later authors.

Landauer, experimenting on dogs, arrived at the result that the urinary nitrogen excretion, i.e., the destruction of albumen, is increased by thirsting. In his experiments the increased nitrogen excretion persisted even during an after-period (during which liquid was again ingested), and the author attributes this to a retention of nitrogen during the thirst period, and a subsequent flushing out of nitrogenous waste.

Landauer also paid attention to the CO₂-excretion during thirsting. However, he arrived at no positive conclusions and, moreover, employed methods that were not beyond criticism, as emphasized by Straub (34).

The destruction of albumen that Landauer found during the thirst-period was also found by Straub. The latter author fed dogs on air-dried meat powder and bacon. During the fore- and after-period the animals received water, but received none during the main period of the experiment. In all of his investigations he found an increase of the urinary nitrogen during the period of thirsting, also an increase of the P₂0₅-excretion. The increased excretion of nitrogen continued during the first days of the after-period; the same applied to the P₂0₅-excretion.

Straub's investigations are particularly important, because he did not limit himself to a study of the albumen catabolism alone, but also made an exact investigation of the elimination of C0₂, a factor that has a very important bearing on the destruction of fat. He found that the excretion of CO₂ via the skin and the lungs was not appreciably increased.

In fact, when one compares the figures for C0₂ during the fore-, the main-, and the after-period, it will be found that during the days of thirsting the CO₂-excretion was slightly decreased.

The excretion of water through the skin and the lungs was found to be slightly, but distinctly, decreased.

The main result, therefore, of Straub's investigation is a corroboration of the fact that the destruction of albumen is increased during a period of water-withdrawal. Contrary to the findings of Landauer, on the other hand, Straub, employing better methods, could find no evidence to show that the withdrawal of liquids led to increased destruction of fat (no increase of the C0₂-production during the period of thirsting).

Almost simultaneously with the investigations of Straub appeared certain studies by Dennig (35); these contained a mass of careful clinical observations that corroborated most of the findings of older authors. The studies were undertaken on human subjects that were subjected to such degrees of thirsting that their general health became seriously impaired and a pronounced distaste for solid food became apparent. Under these conditions the weight and measurements of the body rapidly decreased. The sphygmogram indicated decreased arterial tension. The specific gravity and the amount of dry residue of the serum became increased. The urinary water-output during the period of thirsting greatly exceeded the water-intake during this time, whereas during the fore- and after-periods the reverse was the case. The temperature showed an inclination to rise.