122 THE ALIMENTARY SYSTEM. 



situated wedge-shaped, pyramidal, or crescentic bodies called 

 the crescents of Gianuzzi or demilunes of Heidenhain, each of 

 which is made up of a few opaque granular deeply staining 

 dark cells. The significance of these demilune cells is quite 

 unknown, though several views as to their nature have been 

 propounded, some regarding them as younger germinal cells 

 destined to develop into mucinogenous cells, others as old and 

 exhausted cells which have not taken part in the secretory 

 process, others still as being of the serous type. 



The submaxillary gland is mixed, some of its alveoli being 

 serous, like the parotid, others mucous and with demilunes, 

 like the subliugual. 



The Tonsils. 



The tonsils (Fig. 52) are lymphoid glands located between 

 the pillars of the fauces on each side. They consist of aggre- 

 gations of lymphoid tissue enveloped by a fibrous capsule 

 formed by a condensation of the submucous connective tissue. 

 They are covered by the oral mucous membrane, and rest on 

 the superior constrictor muscles of the pharynx. 



The mucous membrane forming the surface of the tonsil 

 dips down into a number (ten to fifteen) of blind depressions, 

 or crypts, or follicles, each of which is lined with a continua- 

 tion of the stratified squamous epithelium and surrounded by 

 adenoid tissue. 



Mucous glands are present, which discharge into the crypts. 

 The lymphoid cells infiltrate the tunica propria of the mucosa 

 so densely as to obscure it ; they even penetrate among the 

 epithelial cells, often making the boundary between the epithe- 

 lial layer and the subjacent lymphoid tissue indistinct. The 

 lymphoid cells make their way entirely through the epithe- 

 lium in some number, and appear in the mouth as salivary 

 corpuscles. 



The lymphoid tissues in the tonsils, base of the tongue, 

 palate, and pharynx form an adenoid ring about the fauces and 

 pharynx. These structures in the tongue and pharynx are 

 sometimes called the lingual and pharyngeal tonsils. 



The saliva as secreted by the salivary glands, is a homo- 



