CHAPTER V 

 SPONTANEOUS SECRETION OF SALIVA 



The digestive functions of saliva necessitate a regulatory mechan- 

 ism which can adapt the secretory rate and the composition of 

 the saliva during a meal to the amount of food and its chemical 

 and physical properties. The reflex control of salivary secretion 

 described in Chapter XII is responsible for this function. Attempts 

 have been made to demonstrate the existence of a complementary 

 hormonal control similar to that acting on the gastric or pancreatic 

 gland cells. Sacks and Kim (1929), in apparent analogy with the 

 classical experiments of Bayliss and Starling (1902) and Edkins 

 (1906), injected extracts of oral mucosa of the dog intravenously. 

 No secretion of saliva was obtained. The short period of time 

 which the food spends in the mouth seems to make a nervous 

 rather than a hormonal control mechanism suitable. The paralytic 

 secretion described in Chapter VI offers an example of a salivary 

 secretion brought about by hormones; but it is obtained only 

 under exceptional laboratory conditions when large amounts of 

 adrenaline and noradrenaline are released from the suprarenal 

 medulla to act on salivary gland cells, sensitized by previous para- 

 sympathetic denervation. 



Non-digestive functions of the saliva, particularly that of keep- 

 ing the mucosa of the mouth and throat moist, seem to make a 

 more or less continuous activity of at least some salivary glands 

 necessary. This may also be attained reflexly, the dryness of the 

 mucosa acting as a stimulus. There is, however, in addition the 

 possibility that gland cells may be secreting permanently even in 

 the absence of extraglandular stimuli. Apparently some glands of 

 the alimentary canal possess this innate ability of secretion. For 

 such a type of secretion Babkin (1950) used the term spontaneous 

 secretion, "the result of the inherent ability of the secretory cells 

 to elaborate and discharge a digestive juice; this process usually 

 goes on continuously, and is not initiated by impulses carried to 

 the gland cells along the nerves or by humoral regulators in the 

 blood although it may be increased or diminished by such agen- 

 cies". It seems appropriate to use the term in this sense and not 



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