A. ORAL CAVITY, BY E. KLEIN. 513 



of the thyreo-palatinus and the levator palati. It also con- 

 stantly occurs between the first layer of glands of the upper 

 surface, and is to be met with, in larger or smaller quantity, in 

 various parts of the mucous membrane. 



The muscular folds of the mucous membrane which extend 

 as the arcus glosso-palatinus and pharyngo-palatinus, from the 

 soft palate to the root of the tongue and pharyngeal wall, ex- 

 hibit no peculiarity of structure differing from that of the 

 mucous- membrane of the soft palate ; the epithelium, papillae, 

 and muco-membranous tissue being in all essential respects 

 similar. Elastic tissue, forming plexuses, is usually abundant 

 in the mucous membrane of these folds. The lowermost 

 glands diminish in number and size in adults, present the same 

 dimensions as those of the uvula, and are united into a layer, 

 the continuity of which is interrupted by a sparing amount of 

 loose connective tissue containing fat cells surrounding the 

 lobules and acini, and here and there by small muscular fasciculi. 

 The tissue of the mucous membrane is frequently infiltrated at 

 the free border of the folds with a greater or less number of 

 lymph corpuscles. These infiltrated portions, in which may be 

 recognised, besides numerous bloodvessels, a delicate cellular 

 network with decussating fibres of connective tissue, are never 

 sharply defined, but pass gradually into the adjoining tissue. 



Between the palatine arches the lateral walls of this part of 

 the oral cavity, known as the Isthmus faucium, present a de- 

 pression; from the bottom projects a swelling the tonsil, 

 which is sometimes so small in newly born children as to be 

 scarcely perceptible on inspection of the oral cavity from be- 

 fore, and is sometimes so large that the two organs materially 

 contract the dimensions of the isthmus. Their surface is 

 lobulated by fissures of various depths and complexity. The 

 whole organ is to be regarded as a thickened portion of the 

 mucous membrane, presenting a lobulated surface, the proper 

 membrana mucosa of which constitutes a kind of conglobate 

 gland substance (Henle), consisting partly of fibrous, and partly 

 of adenoid tissue, in the meshes of which numerous lymph 

 corpuscles are contained. The epithelium is here tesselated 

 and laminated ; papillae can scarcely be said to be present. 

 Beneath the epithelium is a close plexus of vessels, and the 



