correlatives of water content 227 



§ 84. Correlated metabolisms and behaviors 



Thus far, diverse changes of composition and physical charac- 

 teristics have been mentioned in relation to the body's water con- 

 tent. Another large group of correlatives are rates of physiologi- 

 cal activities; they are set apart from compositions in that they 

 involve intervals of time. The ones considered in the dog concern : 

 (!) outputs of alimentary glands; (2) food intake; (5) energy 

 transformations; (4) renal outputs and clearances; (5) neuro- 

 muscular activities. A great many other quantities might be of 

 equal interest if adequate data be correlated concerning them. 



(1) The outputs of water in the dog's alimentary glands have 

 been studied in saliva, gastric juice, and bile. Saliva is secreted 

 only in minute amounts ordinarily ; in tests some standard stimulus 

 such as pilocarpine or food is given to increase output of saliva. 

 The stimulus is given to the dog once a day (or once an hour) while 

 water privation is decreasing the body water content progressively 

 through several days. Since the changes of body weight are not 

 recorded, rough estimates of water deficit might be made, from the 

 time elapsed and the water missing in the diet. In each series of 

 experiments the saliva is collected from submaxillary glands alone. 

 With each of five stimuli a decrease of salivary output with deficit 

 of water content is found (Crisler, '28; Gregersen, '31; Barron, 

 '32). 



At positive increments of water the rates of salivary secretion 

 have been recorded less precisely. With very large administra- 

 tions of water, "unstimulated" salivation is reported as excessive 

 (Rowntree, '23 ; Underbill and Sallick, '25). Possibly this produc- 

 tion of saliva is correlated with vomiting (Rowntree) ; it is appar- 

 ently reinforced by additional stimuli such as spinal irritation or 

 pituitrin (Theobald, '34). The loss of saliva from the mouth may 

 then be almost as effective as the outputs of urine in relieving the 

 dog of the water load. But these events occur only in certain 

 circumstances and in extreme excesses of water content. 



Vomiting is a direct means of refusing water ; of decreasing the 

 intake of it. It is probably more useful to regard it so than to 

 classify vomiting as a means of output from the body. I believe it 

 has not been shown that water introduced by a non-alimentary 

 route is appreciably lost through the alimentary tract. 



Gastric juice output has been measured in relation to water 

 excesses (Pavlov, '01; Lonnquist, '06; Foster and Lambert, '08; 



