THE MOUTH AND THROAT, ETC. 63 



three pairs of glands, the hirgest of which are the parotid, 

 situated at the root of tlie ear, and from which ducts convey the 

 fluid to the mouth, terminating opposite the second molar 

 teeth. The submaxillary glands are situated under the jaws, and 

 their ducts terminate in tubular eminences near the frrenum 

 or bridle of the tongue. The other salivary glands are the sub- 

 lingua], situated under the tongue, and its ducts terminate rather 

 higher up than those last described. 



The mouth is principally filled with the tongue, which ia 

 muscular in its structure, and very flexible, being indeed a prin- 

 cipal agent in mastication and swallowing. It is larger at 

 the upper part than towards its tip, and is confined poste- 

 riorly to the muscles between the branches of the lower jaw, 

 by a sort of fleshy bridle, and above to a singularly shaped 

 bone, called the os hyoides. It possesses both the power of 

 feeling and tasting, and for this purpose is well supplied with two 

 descriptions of nerves, and is covered by both cutis and cuticle. 



The cavity of the mouth is separated from that of the nostrils 

 by the soft palate, a muscular membranous substance fiistened 

 to the semicircular border of tbe palate bones, and hanging 

 down on the back of the tongue, so that in the ordinary state 

 there is no open communication between the mouth and the 

 thi-oat, and thus all breathing is carried on by the nostrils, and 

 fluids coming either from the lungs or the stomach pass into the 

 nostrils. \Mien, however, food is passing to the stomach, it 

 raises this membrane, and then enters the pharynx, the mem- 

 brane immediately afterwards falling down into its old situation. 



The Pharynx, or food bag, is a muscular cavity, situated at 

 the root of the tongue, and immediately above and adjoining the 

 larynx. It receives the food from the mouth, and by its mus- 

 cular power forces it into the oesophagus. It is this part that is 

 affected in catarrh when there is a difficulty in swallowing. 



The Oesophagus is a long tube, commencing at the pharynx, 

 and ending in the stomach. It passes down the neck rather 

 above the windpipe, and towards the left side enters the chest ; 

 it traverses its upper part, piei'ces the diaphragm, and ends by 

 a sort of curvature in the cardiac orifice of the stomach. It is 

 lined, in common with the mouth and alimentary canal, by a 

 mucous membrane ; but it is principally composed of two orders 

 of muscular fibres, one circular, the other longitudinal, by which 

 it is enabled to propel the food forward, into the stomach. In 

 addition to this there is a white cuticular coat between the 

 muscular and the mucous, and which also lines half the stomach. 



The larynx, the pharynx, and the tongue, ai'e connected 

 together, and to the upper jaw bone, or rather to the bones of 

 the head, by means of the os hyoides, so called from its resem- 

 blance to a spur. The semicircular part of the spur embraces 



