296 



Major W. B. Cannon. 



demonstrated. If one closes the nostrils and breathes through the mouth 

 for five minutes, usually nothing happens during the first minute. The 

 mucosa then begins to feel dry, and at once the saUva starts flowing, and 

 continues for the rest of the period. I have thus collected as much as 

 4*7 c.c. in four minutes. Chewing motions, with the mouth empty, yielded 

 in five minutes only about 1 c.c. In these observations precautions were 

 taken against any psychic effect due to interest, by adding long columns of 

 figures during the test. It seems clear, therefore, that if the mouth tends to 

 become dry, the sahvary glands are normally stimulated to action, and, if 

 there is sufficient outflow from them, the affected surfaces are moistened. 

 The act of swallowing favours the process, for the fluid is thereby spread 

 backwards on the tongue and wiped down the back wall of the pharynx. 



The question whether there is a relation between the existence of water- 

 need in the body and diminished flow of saliva I have examined in two ways 

 — by going without fluid for a considerable period and by profuse sweating, 

 combined with measurements of salivary secretion under uniform stimula- 

 tion. The method of determining salivary output was that of chewing for 

 five minutes and at a uniform rate a tasteless gum, collecting the saliva 

 which flowed during this period, and measuring its volume. All these 

 observations are best made when one is inactive, and in my experience more 

 nearly uniform results are obtained if one lies quiet during the tests. 



The influence on salivary flow of going without fluid for some time may 

 be -illustrated by an example. The chewing to evoke salivary action was 

 started at 7 o'clock in the morning, and repeated each hour until 8 o'clock 

 in the evening. A breakfast consisting of a dry cereal preparation was taken 

 between 8 and 9 o'clock, and a luncheon of dry bread between 12 and 



1 o'clock. Nothing had been drunk since the previous evening. From the 

 first test at 7 o'clock until 11 there was little change in the output of saliva ; 

 the average amount secreted in 5 minutes was 14"1 c.c, with variations 

 between 13 and 16'4 c.c. Then the output began to fall, and at 2 o'clock 

 only 6"4 c.c. was secreted. The average amount for the two observations at 



2 and 3 o'clock was 7"7 c.c. — only little more than half that poured out in 

 the morning. Between 3 and 4 o'clock a litre of water was drunk. The 

 effect was soon apparent. At 4 o'clock the output was 15"6 c.c, and during 

 the next 4 hours, in which more water was taken, and a supper with thin 

 soup and other fluid was consumed, the average amount secreted was 14'6c.c., 

 a figure closely corresponding to the 14" 1 c.c. of the morning hours. These 

 results arQ illustrated graphically in fig. 1. Other tests of this character 

 gave similar results, though there was variation in the rate of decrease in the 

 amounts of sahva secreted. 



