DIGESTIVE ORGANS SALIVARY GLANDS. 



51T 



Salivary Glands in situ. 



1. Parotid gland in situ, extending from the zygoma above, to the 

 angle of the "jaw below. 2. Duct of Steno. 3. Submaxillary gland. 

 4. Its duct. 5. Sublingual gland. 



the mouth at the side Fi s- 213 - 



of thefrsenum linguae. 

 The sublingual gland 

 is situate under the 

 tongue, and its excre- 

 tory ducts open at the 

 sides of that organ, 

 and the intra-lingual 

 or lingual is seated at 

 the inferior surface of 

 the tongue, where the 

 mucous membrane 

 forms a fringed fold. 

 These glands are con- 

 stantly pouring saliva 

 into the mouth ; and 

 it has been presumed, 

 that the fluids se- 

 creted by them may 

 differ from each other 

 in physical and che- 

 mical characters. Such, at least, has been the view of some as re- 

 gards the sublingual, the texture of which more nearly resembles 

 that of the compound follicles than of glands ; but the circumstance 

 has not been proved by any direct experiment. The saliva, as met 

 with, is a compound of every secretion poured into the mouth ; and it 

 is this fluid which has been chiefly subjected to analysis. The secretion 

 of the saliva, and its various properties, will be considered, however, 

 hereafter. 



The two apertures of the mouth are the labial and pharyngeal. The 

 former, as its name imports, is formed by the lips, which consist ex- 

 ternally of a layer of skin ; are lined internally by a mucous membrane; 

 and, in their substance, contain numerous muscles, already described 

 under the head of Gestures. These muscles may be separated into 

 constrictors and dilators; the orbicularis oris being the only one of 

 the first class, and the antagonist to the others, which are eight in 

 number, on each side levator labii superioris alseque nasi, levator labii 

 superioris proprius, levator anguli oris, zygomaticus major, zygomati- 

 cus minor, buccinator, triangularis, and quadratus menti. (Fig. 201.) 

 To the last two muscles are added some fibres of the platysma myoides. 



The pharyngeal opening is smaller than the labial, and of a quadri- 

 lateral shape. It is bounded above by the velum palati or pendulous 

 veil of the palate; below, by the base of the tongue ; and laterally, by- 

 two muscles, which form the pillars of the fauces. The pendulous veil 

 is a musculo-membranous extension, constituting a kind of valve, at- 

 tached to the posterior margin of the bony palate, by which all com- 

 munication between the mouth and pharynx, or between the pharynx 

 and nose can be prevented. (Fig. 214.) To produce the first of these 

 effects, it becomes vertical; to produce the latter, horizontal. At its 

 inferior and free margin, it has a nipple-like shape, and bears the name 



