182 



HISTOLOGY. 



chiefly in relation with the taste cells; to a less extent they are said to 

 ramify about certain of the supporting cells. The taste cells are believed 

 to transmit to the nerves the stimuli received at the taste pore. 



The tunica propria of the mucous membrane, a loose connective tissue 

 layer containing fat, is not sharply separated from the denser submucosa. 

 At the tip, or apex linguae, and over the dorsum, the submucosa is par- 

 ticularly firm and thick, forming the fascia linguae. Three sorts of glands 

 branch in the submucosa and may extend into the superficial part of the 

 muscle layer. These are the serous glands found near the vallate and 

 folliate papillae; mucous glands occurring at the root of the tongue, along its 

 borders, and in an area in front of the median vallate papilla; and the 



Median section of a nodule. 

 Epithelium. 



Diffuse lymphoid tissue. -_ 



Lymph nodules. 



Duct of a mucous gland. " 



| Epithelium. 



Periphery 

 of a nodule. 



) Tunica propria. 

 Fibrous capsule. 



J 

 Blood vessel. 



FIG. 205. FROM A SECTION OF THE LINGUAL TONSIL OP AN ADULT MAN. X 20. 



i , Pit containing leucocytes which have infiltrated its epithelium on the left side ; that on the right is 



almost intact. 



two mixed anterior lingual glands, from half an inch to an inch long, each 

 of which empties by five or six ducts on the under surface of the apex. 

 The appearance of these types of glands will be described in a following 

 section. 



Blood vessels are numerous in the submucosa and form extensive 

 capillary networks in the tunica propria of both the larger and the second- 

 ary papillae. Small lymphatic vessels also form a network in the tunica 

 propria and this is continuous with a coarser net in the submucosa. The 

 nerves (sensory) are the terminations of the lingual branches of the man- 

 dibular nerve anteriorly, and of the lingual branches of the glossopharyn- 

 geus posteriorly. They contain nerve cells which are grouped in small 

 ganglia, notably beneath the vallate papillae. The glossopharyngeal end- 



