244 



THE LYMPHATIC SYSTEM 



tonsil is so very active that at times the epithelium becomes completely 

 filled with these cells, and it is then difficult to distinguish it from the 

 adenoid tissue beneath. The normal tonsils atrophy after puberty. 



The Lingual Tonsil. A collection of lymph nodules is also found 

 at the base of the tongue in the median line, between the cireumvallate 

 papilla3 and the epiglottis. This, because of its similarity in appearance 

 and in structure to the faucial tonsil, is called the lingual tonsil. 



In the lingual tonsil, however, the nodules are grouped about a 



FIG. 249. THE LINGUAL TONSIL OF MAN. 

 a, a crypt; b, von Ebner's glands. Hematein and eosin. X 45. 



single wide-mouthed crypt, the foramen caecum lingui. This crypt is 

 frequently branched, and into it the many mucous glands of the neighbor- 

 ing lingual mucosa pour their secretion. 



The Pharyngeal Tonsil. The posterior wall of the nasopharynx is 

 supplied with a similar accumulation of lymph nodules, the pharyngeal 

 tonsil. It lies in the median line and extends downward from between 

 the orifices of the auditory (Eustachian) tubes for a distance of three 

 centimeters (Klein). It contains a considerable number of lymph nod- 

 ules and several small crypts. The lateral extensions in the vicinity 

 of the tubal orifices are sometimes known as the tubal tonsils. 



The pharyngeal tonsil is prone to hypertrophy in youth, in which 



