CHAPTER X. 

 THE REGULATION OF SALIVARY SECRETION. 



i. Salivary Fistulae. The salivary glands have since the 

 earliest days of experimental physiology served as objects 

 of investigation, partly through the fact that changes in 

 the character of their secretions from time to time are readily 

 apparent and partly because their superficial situation ren- 

 ders them easily accessible to study. 



In order to determine the quantitative or qualitative 

 changes in the saliva as it is poured out by the three pairs 

 of parotid, submaxillary, and sublingual glands it is necessary 

 to collect the saliva as it issues from the ducts. It is pos- 

 sible to accomplish this in man and various animals by 

 inserting fine catheters into the ducts of these glands and 

 allowing the saliva to drip into small glass tubes. Some- 

 times nature creates salivary fistulae which open externally, 

 as when salivary calculi ulcerate through the cheek or injuries 

 of various kinds to a salivary gland or its excretory duct 

 cause the saliva to flow out upon the skin. The study of 

 such cases has yielded many valuable physiological data. 



The older investigators, in their animal experiments, used 

 to lay bare the different salivary glands, catheterize the ducts 

 and collect the saliva which poured out of them. Today, how- 

 ever, when we have learned how much narcotics and various 

 operative procedures interfere with the normal function of an 

 organ we try to employ experimental procedures which do 

 away with such disturbing influences. In a large number of 

 experiments it is possible therefore to work on animals in 



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