234 



HISTOLOGY 



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

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



The sensory nerves are the terminations of the lingual branches of the 

 mandibular nerve anteriorly, and of the lingual branches of the glosso- 

 pharyngeus posteriorly. In the submucous connective tissue they form 

 a plexus of medullated and non-medullated fibers, and in some places, 

 notably beneath the vallate papillae, nerve cells are found, grouped in 

 small ganglia (Fig. 223). The terminal branches of these nerves probably 

 end in part in bulbous corpuscles, but most of them, as non-medullated 



Taste bud. 



Fibers between 

 the buds 



Fibers overlying 

 a bud. 



Connective tissue. 

 Epithelium. 



Fibers within the buds. 



Connective tissue. 



Nerve. 



FIG. 224. FROM A VERTICAL SECTION OF THE FOLIATE PAPILLA OF A RABBIT. X 220. 



fibers, enter the epithelium and extend to the outer epithelial cells, gener- 

 ally without branching (as on the left of Fig. 224). Others enter the groups 

 of specialized epithelial cells, known as taste buds, which are believed to 

 be the special organs of taste. Within the buds the nerves divide into 

 coarse varicose branches which end freely, without uniting with the cells 

 or anastomosing with one another (Fig. 224). 



Taste buds are round or oval groups of elongated epithelial cells, most 

 of which extend from the basal to the free surface of the epithelium. In 

 embryos of from five to seven months they are more numerous than in the 

 adult, occurring in many filiform papillae, in all the fungiform, vallate and 

 foliate papillae, and also upon both sides of the epiglottis. Subsequently 

 they are destroyed with an infiltration of leucocytes except on the lateral 

 walls of the vallate and foliate papillae, on the laryngeal surface of the 



