STUDIES ON THE REGULATION OF WATER INTAKE

Abstract

I. In an attempt to evaluate the importance of the salivary glands in relation to water intake, the amount of water taken by dogs during 1 or 2 hrs. of panting in a warm room (40[degree] C.) was determined before and after exclusion of the salivary flow by extirpating the submaxillary, sub-lingual and infraorbital glands, and tying the parotid ducts. After recovery from the operation 6 out of 8 dogs tested drank on the average twice as much water in the warm room as before the exclusion of the salivary flow. Therefore, under conditions which make the mouth dry (panting), a deficient salivary flow may cause thirst and increased water intake even in the absence of bodily dehydration.[long dash]II. An instrument (the potometer) is described whereby the drinking of water is recorded graphically and quantitatively. Graphic records of the 24-hr. water intake of dogs reveal that almost all the water is taken within 2 to 5 hrs. after feeding, regardless of the time food is given. Fasting usually reduces the 24-hr. intake to 1/4 normal or less. If the giving of water is delayed for several hrs. after feeding, the 24-hr. intake is ordinarily much less than when water is given ad libitum throughout the postprandial period. The postprandial thirst is therefore, in part, temporary, and probably due to withdrawal of water from the body for the secretion of digestive juices.