Other Functions 259 



(Dold, Lachele and Hsing, 1936; Weigmann and Noeske, 1937; 

 Thompson, 1940, 1941 ; van Kesteren, Bibby and Berry, 1942). 



OTHER FUNCTIONS 



Adequate moistening of the buccal and pharyngeal mucosa is 

 necessary not only for digestive and protective purposes but for 

 articulate speech, as experienced in states of anxiety or fright when 

 the salivary reflex is inhibited. 



The role played by saliva in the regulation of the water balance 

 of the body has for a long time been a controversial subject. The 

 defenders of the "local dryness" theory assume that water intake 

 is regulated from the mucosa of the mouth and throat, dryness due 

 to inadequate salivation acting as a stimulus. According to this 

 view thirst may be felt and water consumed even with normal 

 stores of water whenever the mucosa becomes dry, for instance, in 

 fear, after injection of atropine, when breathing hot and dry air 

 through the mouth or after ligation of the salivary ducts. In a 

 dehydrated subject, on the other hand, thirst may be alleviated by 

 moistening the mucosa with water, by anaesthetizing the mucosa 

 or by increasing the flow of saliva. This can be achieved by putting 

 some acid substance into the mouth or even by injecting pilocar- 

 pine. In order to explain the fact that dehydration gives rise to 

 thirst, Cannon (19 1 8) pointed out that the salivary glands, like other 

 tissues, must suffer when water is lacking in the body; experi- 

 mentally, he found that the secretion of saliva in response to chew- 

 ing a tasteless gum, decreased when he reduced his water intake 

 or produced excessive sweating. Similarly, secretion of saliva has 

 been found to diminish after haemorrhage and after a meal when 

 large amounts of fluid are lost temporarily with the digestive juices. 

 Even after intravenous injection of hypertonic sodium chloride 

 solution the salivary flow is reduced. Some of the findings or their 

 interpretations upon which this theory is founded have been dis- 

 puted. Montgomery (193 1a), for instance, observed no increase of 

 the water intake in dogs after extirpation of the main salivary 

 glands. Gregersen and Cannon (1932) remarked, however, that the 

 secretion from the small salivary glands left in these experiments 

 might be able to keep the mucous membranes adequately moist- 

 ened under ordinary conditions. They repeated the experiment in 

 hot surroundings which caused the dogs to pant and found this 

 procedure to double the water intake. After injections of atropine 



