THE DIGESTIVE ORGANS. 



as clusters of small lymph -follicles, similar to those found in the 

 tongue. The pharyngeal tonsil presents numerous irregularly 

 formed crypts, lined by stratified pavement epithelium. These crypts 

 are often widened at the base and are provided with irregular sac- 

 cular enlargements. The crypts are all surrounded with lymphoid 

 tissue, which may be regarded as diffuse lymphoid tissue in which 

 are found numerous lymphoid follicles, often showing germ-centers. 

 The lymphoid tissue is bounded externally by fibrous tissue, septa 

 of which pass into the lymphoid tissue surrounding the crypts. 



Fig. 196. Section through the pharyngeal tonsil of man; X 6^ : agp, Arcus 

 glosso-palatinus ; ep, epithelium;/?, crypt; M, striated muscle; nl, lymphoid nodules; 

 S, connective tissue septa ; sf, remains of tonsillar sinus. 



The epithelium lining the crypts or cavities of the tonsils shows, 

 as in the lingual follicles, extensive degenerative changes, resulting 

 mainly in the formation of variously shaped communicating spaces 

 filled with lymphocytes and leucocytes. (See Fig. 197.) 



Besides the nerves terminating in the taste-buds, the tongue is 

 richly supplied with sensory nerves which terminate in free sen- 

 sory endings, which may be traced into the epithelium, and which 

 are especially numerous in the fungiform and circumvallate papillae ; 

 or in smaller or larger end-bulbs of Krause found in the mucosa of 



