THE TONGUE 



343 



glands of N"uhn. The serous glands of von Ebner are confined to the 

 region of the circumvallate papillae at the base of the tongue. They 

 pour their secretion into the trench which surrounds the base of the 

 papilla or -into the crypts of the lingual tonsil. Other lingual glands, 

 of the small tubulo-acinar mucous type, occur at various portions of 

 the dorsal surface of the tongue, being especially abundant in the 

 lymphoid area. 



The Lingual Tonsil. The lingual tonsil (Fig. 249) is a con- 

 siderable collection of lym- 

 phoid nodules which is 

 found at the base of the 

 tongue in and about the 

 median line. These nod- 

 ules are grouped about a 

 large funnel-shaped crypt, 

 the foramen cecum, which 

 opens at the apex of the V 

 formed by the group of 

 circumvallate papillae and 

 which in the embryo forms 

 the lingual extremity of 

 the so-called duct of the 

 thyroid gland (iliyroglos- 

 sal duct). Several smaller 

 crypts are also included in the region of the lingual tonsil. 



The lymphoid nodules are embedded in the mucosa or corium of the 

 tongue and are surrounded by mucous glands, many of whose ducts 

 penetrate between the nodules to open into the branching crypts. 

 Lymphocytes, apparently derived from the nodules, infiltrate the sur- 

 rounding connective tissue and epithelium and find their way into the 

 lumen of the tonsillar crypts. 



The Blood-vessels of the Tongue. The blood-vessels of the tongue 

 are supplied by large arteries (branches of the lingual artery) which, 

 with the corresponding veins, are embedded in the muscular portion of 

 the organ and supply capillary vessels to this tissue. From these ar- 

 teries, also, small arterial branches enter the deeper portion of the 

 corium and form a capillary plexus which supplies the connective tissue 

 and whose terminal ramifications extend to the very apex of the con- 

 nective tissue papilla?. The blood is returned by veins which pursue 

 a similar course. 



FIG. 323. Two FOLIATE PAPILLE FROM A RAB- 

 BIT'S TONGUE, SHOWING NUMEROUS TASTE BUDS 

 ALONG THEIR LATERAL MARGINS. 



