718 ORGANS OF DIGESTION. 



The hard palate is bounded in front and at the sides by the alveolar arches 

 and gums; behind, it is continuous with the soft palate. It is covered by a 

 dense structure, formed by the periosteum and mucous membrane of the mouth, 

 which are intimately adherent together. Along the middle line is a linear 

 ridge or raphe, which terminates anteriorly in a small papilla, corresponding 

 with the inferior opening of the anterior palatine fossa. This papilla receives 

 filaments from the naso -palatine and anterior palatine nerves. On either side 

 and in front of the raphe, the mucous membrane is thick, pale in color, and 

 corrugated; behind, it is thin, smooth, and of a deeper color: it is covered with 

 squamous epithelium, and furnished with numerous glands (palatal glands), 

 which lie between the mucous membrane and the surface of the bone. 



The soft palate (velum pendulum palati) is a movable fold, suspended from 

 the posterior border of the hard palate, and forming an incomplete septum 

 between the mouth and pharynx. It consists of a fold of mucous membrane, 

 inclosing muscular fibres, an aponeurosis, vessels, nerves, and mucous glands. 

 When occupying its usual position (i. e., relaxed and pendent), its anterior sur- 

 face is concave, continuous with the roof of the mouth, and marked by a median 

 ridge or raphe, which indicates its original separation into two lateral halves. 

 Its posterior surface is convex, and continuous with the mucous membrane 

 covering the floor of the posterior nares. Its upper border is attached to the 

 posterior margin of the hard palate, and its sides are blended with the pharynx. 

 Its lower border is free. 



Hanging from the middle of its lower border is a small conical-shaped pen- 

 dulous process, the uvula; and arching outwards and downwards from the base 

 of the uvula on each side are two curved folds of mucous membrane, contain- 

 ing muscular fibres, called the arches or pillars of the soft palate. 



The anterior pillar runs downwards and forwards to the side of the base of 

 the tongue, and is formed by the projection of the Palato-glossus muscle, 

 covered by mucous membrane. 



The posterior pillars are nearer to each other and larger than the anterior ; 

 they run downwards and backwards to the sides of the pharynx, and are formed 

 by the projection of the Palato-pharyngei muscles, covered by mucous mem- 

 brane. The anterior and posterior pillars are separated below by a triangular 

 interval, in which the tonsil is lodged. 



The space left between the arches of the palate on the two sides is called the 

 isthmus of the fauces. It is bounded above by the free margin of the palate; 

 below, by the tongue ; and on each side, by the pillars of the soft palate and 

 tonsils. 



The mucous membrane of the soft palate is thin, and covered with squamous 

 epithelium on both surfaces, excepting near the orifice of the Eustachian tube, 

 where it is columnar and ciliated. The palatine glands form a continuous layer 

 on its posterior surface and round the uvula. 



The aponeurosis of the soft palate is a thin but firm fibrous layer, attached 

 above to the hard palate, and becoming thinner towards the free margin of the 

 velum. It is blended with the aponeurotic tendon of the Tensor palati muscle. 

 The muscles of the soft palate are five on each side; the Levator Palati, Ten- 

 sor Palati, Palato-glossus, Palato-pharyngeus, and Azygos UvulaB (see p. 342). 

 The tonsils (amygdalae) are two glandular organs, situated one on each side of 

 the fauces, between the anterior and posterior pillars of the soft palate. They 

 are of a rounded form, and vary considerably in size in different individuals. 

 Externally, the tonsil is in relation with the inner surface of the Superior Con- 

 strictor, and with the internal carotid and ascending pharyngeal arteries, and 

 corresponds to the angle of the lower jaw. Its inner surface presents from 

 twelve to fifteen orifices, leading into small recesses, from which numerous 

 follicles branch out into the substance of the gland. These follicles are lined 

 by a continuation of the mucous membrane of the pharynx, covered with 

 epithelium, their walls being formed by a layer of closed capsules imbedded 



