160 , INTESTINAL MUCOUS MEMBKANE. 



in structure (vide ut supra}. These follicles present 

 no trace of an excretory duct, or any visible external 

 opening ; the existence of the central orifice on the 

 surface of the mucous covering of the eminence 

 which they form, has led to mistakes on this point, 

 but, as we have already seen, this opens only into a 

 cul-de-sac. 



Tonsils. The tonsils are composed of an aggregation of 

 ductless follicles identical with those just described ; 

 they are therefore compound ductless glands. The 

 excavations which we see upon their free convex sur- 

 faces are simple blind cavities, sometimes containing 

 masses of whitish material of a disagreeable odor, 

 and consisting of debris of epithelium in a state of 

 partial fatty degeneration. 



The lymphatics of the cavity of the mouth are 

 very numerous, especially those of the mucous mem- 

 brane of the tongue. They appear to take their 

 origin immediately beneath its epithelial layer, and 

 communicate with the cervical lymphatic glands. 



The papillae of the mucous membrane of the pha- 

 rynx are smaller, and less numerous, than those of 

 the mouth. Its epithelium, in strata, resembles that 

 of the buccal cavity, only it is to be noticed that in 

 the upper portion, or vault, of the pharynx, it is pro- 

 vided with ciliated cells, In the deeper layers of the 

 membrane proper are numerous ductless glands, and 

 clusters of follicles ; the first are found only in the 

 upper part of the pharynx, whilst the mucous folli- 

 cles exist in all parts of the membrane. Its blood- 

 vessels are numerous, and are similarly distributed to 

 those of the walls of the cavity of the mouth. Its 



