Chap. xii.] SIMPLE LYMPHATIC VESSELS. 95 



shorter folds into the substance within. Numbers of 

 mucus-secreting glands situated outside the layer of 

 lymph follicles discharge their secretion into the pits 

 (the crypts) between the folds. The free surface of the 

 tonsils and the crypts is covered or lined with the 

 same stratified epithelium that lines the oral cavity. 

 Numbers of lymph corpuscles constantly, in the per- 

 fectly normal condition, migrate through the epithe- 

 lium on to the free surface, and are mixed with the 

 secretions (mucus and saliva) of the oral cavity. The 

 so-called mucous or salivary corpuscles of the saliva, 

 \aken from the oral cavity, are such discharged lymph 

 corpuscles. They become swollen up by the water of 

 the saliva, and assume a spherical shape. They finally 

 disintegrate. 



Similar relations, only on a smaller scale, obtain 

 at the root of the tongue. 



The pharynx tonsil of Luschka, occurring in the 

 upper part of the pharynx, is in all essential respects 

 the same as the palatine tonsil. Owing to large parts 

 of the mucous membrane of the upper portion of the 

 pharynx being covered with ciliated columnar epithe- 

 lium, some of the crypts in the pharynx tonsil are also 

 lined with it. 



125. The lenticular glands of the stomach are 

 single lymph-follicles. 



The solitary glands of the small and large 

 intestine are single lymph-follicles. 



The agmiiiatcd glands of the ileum are groups 

 of lymph-follicles. The mucous membrane containing 

 them is much thickened by their presence. These groups 

 of follicles are called a Peyer's patch or a Peyer's gland. 



126. In most instances the capillary blood-vessels 

 form in the lymph-follicles meshes, arranged in a more 

 or less radiating manner from the periphery towards 

 the centre ; around the periphery there is a network 

 of small veins. A larger or smaller portion of the 



