408 THE DIGESTIVE APPARATUS IN MAMMALIA. 



There consequently results, between these three organs, a remarkable unity 

 of action, which is readily explained by the part they all take in the one common 

 act of deglutition. 



5. Soft Palate (Figs. 215, 224). 



Preparation. — The soft palate is studied : 1. On the antero-posterior and vertical section of 

 the head (Fig. 220). 2. On the portion intended to show the interior of the pharynx (see the 

 preparation of this regii)n). 3. On the portion represented in Fig. 215, the mode of dissecting 

 ■which lias been indicated at page 399 ; in removing the mucous membrane and glandular 

 layer, the fibrous membrane and the two intrinsic muscles are exposed. The extrinsic muscles 

 should be studied with those of the pharynx. 



Situation — Form. — The soft palate (palatum molh, velum pendulum palati) is 

 suspended like a partition between the mouth and the pharynx, and by its 

 posterior border circumscribes the orifice that establishes a communication 

 between these two cavities. 



This partition, which continues the hard palate posteriorly, represents in its 

 external form a membranous valve, oblique downwards and forwards, much 

 longer than it is wide, and exhibiting for study two faces and/o?/r borders. 



The inferior or anterior face, towards the mouth, shows longitudinal folds 

 and transverse ridges, with multitudes of orifices belonging to the submucous 

 glandulffi. On its sides it is united to the base of the tongue by means of two 

 thick mucous columns, designated the posterior pillars of the tongue. The 

 superior or posterior face forms the anterior wall of the pharynx ; it only exhibits 

 some very shght longitudinal ridges. 



The two lateral borders are inserted into the walls of the two cavities which 

 the soft palate separates. The anterior border, continuous with the palate, is 

 attached to the palatine arch, and follows the curve described by it. The 

 posterior border — the only free one — is concave, and closely embraces the base of 

 the epiglottis, which is usually found lying against the posterior surface of this 

 curtain. This border is continued at its extremities by two thin prolongations, 

 which can be followed on the lateral walls of the pharynx to the oesophageal 

 inf undibulum, above which they unite in the form of an arch. These prolonga- 

 tions are the posterior pillars of the soft palate, in contradistinction to the two 

 mucous folds at the base of the tongue, which constitute, by their relation to 

 this partition, veritable anterior pillars. This posterior border concurs in cir- 

 cumscribing what is named the isthmus of the fauces— an aperture constantly 

 closed in Solipeds, in consequence of the great development of the soft palate ; 

 it is only dilated for the passage of the alimentary substances passing into the 

 pharynx. The isthmus of the fauces is, therefore, not merely an opening ; it is 

 a passage which has for its inferior wall the base of the tongue as far as the 

 epiglottis ; for its upper wall, the anterior face of the soft palate ; and for its 

 sides the posterior pillars of the latter. 



Structure.— To give the most simple idea of the structure of the soft 

 palate, it may be said that the mucous membrane of the palate, and that of the 

 floor of the nasal cavities, is prolonged behind the palatine arch, parallel to one 

 another, and become joined towards the free border of this curtain ; and it 

 might be further shown that, in the space between these two mucous membranes, 

 there is a fibrous membrane, muscles, a glandular layer, vessels, and nerves ; 

 besides these, there are no other elements in the organization of the soft palate. 



