SALIVARY GLANDS. 497 



the tooth they are reflected into the alveolus, and become continuous 

 with the periosteal membrane of that cavity. 



The Tongue has been already described as an organ of sense ; it 

 is invested by mucous membrane, which is reflected from its under 

 part upon the inner surface of the lower jaw, and constitutes, with 

 the muscles beneath, the floor of the mouth. Upon the under sur- 

 face of the tongue, near to its anterior part, the mucous membrane 

 forms a considerable fold, which is called the frsenum linguas ; and 

 on each side of the fraenum is a large papilla, the commencement 

 of the duct of the submaxillary gland, and several smaller openings, 

 the ducts of the sublingual gland. 



The Soft palate (velum pendulum palati) is a fold of mucous mem- 

 brane situated at the posterior part of the mouth. It is continuous, 

 superiorly with the hard palate, and is composed of mucous mem- 

 brane, palatal glands, and muscles. Hanging from the middle of its 

 inferior border is a small rounded process, the uvula ; and passing 

 outwards from the uvula on each side are two curved folds of the 

 mucous membrane, the arches, or pillars of the palate. The anterior 

 pillar is continued downwards to the side of the base of the tongue, 

 and is formed by the projection of the palato-glossus muscle. The 

 posterior pillar is prolonged downwards and backwards into the 

 pharynx, and is formed by the convexity of the palato-pharyngeus 

 mjiscle. These two pillars, closely united above, are separated below 

 by a triangular interval or niche, in which the tonsil is lodged. 



The Tonsils (amygdala?) are two glandular organs, shaped like 

 almonds, and situated between the anterior and posterior pillar of 

 the soft palate, on each side of the fauces. They are cellular in 

 texture, and composed of an assemblage of mucous follicles, which 

 open upon the surface of the gland. Externally, they are invested 

 by the pharyngeal fascia, which separates them from the superior 

 constrictor muscle and internal carotid artery, and prevents an ab- 

 scess from opening in that direction. In relation to surrounding 

 parts, they correspond with the angle of the lower jaw. 



The space included between the soft palate and the root of the 

 tongue is the isthmus of the fauces. It is bounded above by the soft 

 palate : on each side by the pillars of the soft palate and tonsils ; 

 and below by the root of the tongue. It is the opening between 

 the mouth and pharynx. 



SALIVARY GLANDS. 



Communicating with the mouth are the excretory ducts of three 

 pairs of salivary glands, the parotid, submaxillary, and sublingual. 



The Parotid gland (*,, near, o5V, wroj, the ear), the largest of 

 the three, is situated immediately in front of the external ear, and 

 extends superficially for a short distance over the masseter muscle, 

 and deeply behind the ramus of the lower jaw. It reaches infe- 

 riorly to below the level of the angle of the lower jaw, and poste- 

 riorly to the mastoid process, slightly overlapping the insertion of 



63 



