The problem of water and electrolyte metabolism, an essential regulation in the living body of its internal environment, has been investigated by many researchers. In this paper, we have summarized our study concerned with the effects of thermal bath (plain water or hot spring) on the water and electrolyte metabolism. Also, some related changes in circulatory and endocrine systems were considered.
Twelve young men were selected and series of comparative study before and after each bathing for 10 minutes duration at temperature of 40 to 43°C have been performed.
I Water and electrolyte metabolism
(1) Immediately after the bathing no change was observed in the total body water. The extracellular fluid and the plasma volume increased; hematocrit values were lowered, while the total blood water as well as the plasma water was both increased and the water content of blood corpuscles was decreased. This result was inferred to a replacement of body water from inside to outside of the cells.
(2) The minute volume of urine voided immediately after the bathing showed a transient increase, whereas it was decreased after the period of bath and also less than the pre-bathing stage.
(3) Plasma Na was lowered after the bathing, while K and Cl remained unchanged. Na content of blood corpuscles showed a rise and K was lowered. The same tendency has also been observed in the skeletal muscle.
(4) Reabsorption of Na as well as excretion of K in the urine was slightly increased after the bathing.
(5) There was a loss of electrolytes into sweat.
(6) The permeability of Na²⁴ across the capillary wall was increased during and immediately after the bathing.
II Changes in circulatory and endocrine systems related with water and electrolyte metabolism
Among many changes induced by thermal bathing which may cause alteration in circulatory and endocrine systems, a rise of body temperature and an induced hyperfunction of adrenal glands were considered to play a major role in the whole processes.

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Introduction: The variation or fluctuation is a principal character of skintemperature, and it should be understood as a part of autoregulatory mechanism of body temperature in the physiological as well as pathological conditions.
As for the skin, man is situated in special condition; that is, man has both purely biological and cultural regulation. Consequently it is doubtful that deta obtained under nude condition could be normal.
All factors of body temperature regulation are considered also as those of the skintemperature variation, Therefore, the skintemperature variation is very complex and study on this problem is perplexing and difficult.
The consideration of many experimental deta on skintemperature, bodytemperature and relation between skintemperature and circulation at various conditions, lead to the following conclusion. Emphasizing of the identity of the regulatory stage is important, and the measuring conditions and temperature reaction should be considered as the factors producing this stage and the reaction invited from this respec tively.
From this standpoint, regulatory stages of skintemperature belonging to perspiratio insensibilis are classified “five stadia”, that is, I, II, III IV, V stadium, and phenomena at physiological and pathological condition are analyzed belonging to each stadia. Measurements are performed chiefly by means of thermocouples.
The seasonal variation, diurnal variation, short time variation of skinperature distribution, inversed correlation of skin-and body-temperature, etc, are discussed.
An investigation on the relationship between skintemperature and skincirculation. —Experiment chiefly with the ear of rabbit—: The ear of rabbit is experimentally proved to be an effective organ concerning heat loss, and both ear of rabbit and peripheral parts of human extremities are considered as similar organs as to heat loss. Therefore, investigation on the ear of rabbit is significant for that of human subject, from a standpoint of the comparative physiology. The relation between the thermal and circulatory variation in the rabbit's ear is analyzed mathematicaly from the viewpoint of “signal and its response”, and the fact that temperature curves are expressed as exponential function, and number of descending branches of variation curves have the same parameter, it is concluded that temperature variation is produced by “off and on” of circulation. And then, this fact is proved by the perfusion experiment on cut-off ear. That is, it is found that the variation curves of ear temperature is evoked by one or both of alternations of “off and on” frequency and circulatory duration. (Fig. 1, 2, 3, 4.)
Resulting from this fact, it is impossible to estimate circulating blood volume by means of intermittent skintemperature measurement, and also impossible to conclude the absolute skintemperature value corresponding to room temperature, even if continuous temperature curve were obtained.
The same discussion is available on the peripheral skintemperature of human subject comparative-physiologically. (Fig. 5)
An investigation on the skintemperature variation. —On its “stadium”—: It is proper to classify the regulated state of skintemperature into five stadia (namely, I, II, III, IV, V stadium) basing upon the relationship of rectal-, skin-temperature of fingers and toes and room temperature.
A number of phenomena of skintemperature are reasonably interpreted from the standpoint of the classified five stadia.
As can be seen in the diagramm in the text, the characteristics of temperature curves, temperature level (of finger, toe, and body temperature), fluctuability (temperature variations of finger, toe and bodytemperature, duration and periodicity of variation from the analysis of autocorelogramm), difference between right and left side (similarity of variation rhythm between right and left si

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