The water loss and blood changes by prolonged sweating without intake of food and drink.

Thirst sensations due to the water loss of the body by sweating exhibit a characteristic time lag so that men always fail to drink enough to replace immediately their sweat losses. If a heavy sweating has took place under such a state of water debt, the chloride concentration of the body fluid has to be remarkably raised, for the chloride content of sweat is far lower than that of the body fluid. But previous reports indicated that the Cl content of blood remained unchanged or even decreased slightly after heavy sweating (1-5). If so, some regulatory mechanisms preventing the rise of osmotic pressure of the body fluid must be in action during the sweating. The following mechanisms appear to be responsible for the regulation: (1) renal regulation, (2) the shift of water in the body and (3) the storage of Cl in some tissues. Experiments with regard to this problem were previously made by members of this Institute on men walking for hours on midsummer days without taking food and drink. The general symptoms, sweating and changes in the blood were investigated, special reference being taken to renal regulation. The results of the experiments were published in 1942 in two Japanese papers by Itoh, Masui, Hattori, Okuda and Suzuki (6) and by Itoh, Masui and Matsumoto (7) respectively. The present paper presents an account of the experimental results described in these two papers and some discussion newly considered by the author.