SALIVA 171 



the office of this gland is supposed to be particularly connected with 

 mastication, although its flow continues in small quantity during the 

 intervals. Its quantity is regulated somewhat by the character of the 

 food, being greater when articles taken into the mouth are dry than when 

 they contain considerable moisture. In the human subject, the stimulus 

 produced by sapid substances will sometimes cause a considerable in- 

 crease in the flow of the parotid saliva. The supposition that the flow 

 from the parotid is dependent on the mechanical pressure of the muscles 

 or of the condyle of the lower jaw during mastication has no foundation 

 in fact. 



Submaxillary Saliva. In the human subject, the submaxillary is the 

 second of the salivary glands in size. Its minute structure is nearly the 

 same as that of the parotid. As its name implies, it is situated beneath 

 the inferior maxillary bone. It is in the anterior part of what is known 

 as the submaxillary triangle of the neck. Its excretory duct the duct 

 of Wharton is about two inches (5 centimeters) in length and passes 

 from the gland, beneath the tongue, to open by the side of the frenum. 



The pure submaxillary saliva presents many important points of 

 difference from the secretion of the parotid. It may be obtained by 

 exposing the duct and introducing a tube, when, on the introduction of 

 any sapid substance into the mouth, the secretion will flow in large 

 pearly drops. This kind of saliva is much more viscid than the parotid 

 secretion. It is clear, and on cooling, it frequently becomes of a gelati- 

 nous consistence. Its organic matter is not coagulable by heat. It 

 contains a sulphocyanate, but in small quantity. 



The submaxillary gland discharges its secretion in greatest abun- 

 dance when sapid substances are introduced into the mouth ; but unlike 

 the parotid saliva, the secretion does not alternate on the two sides with 

 alternation in mastication. Although sapid articles excite an abundant 

 secretion from the submaxillary glands, they also increase secretion 

 from the parotids and sublinguals ; and, on the other hand, movements 

 of mastication increase somewhat the flow from the submaxillaries, and 

 these glands secrete a certain quantity of liquid during the intervals of 

 digestion. 



Sublingual Saliva. The sublinguals, the smallest of the salivary 

 glands, are situated beneath the tongue, on either side of the frenum. 

 In minute structure they resemble the parotid and submaxillary glands. 

 Each gland has a number of excretory ducts, eight to twenty, - 

 which open into the mouth by the side of the frenum ; and one of the 

 ducts, larger than the others, joins the duct of the submaxillary gland 

 near its opening in the mouth. 



The secretion of the sublingual glands is more viscid, even, than 



