146 



NORMAL HISTOLOGY. 



capillary loops (Fig. 186) which occupies the connective tissue stroma, 

 including that of the secondary papillae. Other twigs pass to the glands and 

 end in capillary networks that surround the alveoli; still others provide 

 capillaries which ramify within the aggregations of lymphoid tissue. The 

 lymphatics of the tongue constitute two groups, a superficial within the 

 mucous and submucous layers and a deep one within the musculature. The 

 submucous vessels arise from the rich network of lymph-channels within the 



i. Epithelium covering 

 '< filiform papillae 



Capillary loops 

 within connective- 

 tissue basis of 

 papillae 



Mucous membrane 



Muscular tissue 



FIG. 186. Injected mucous membrane from upper surface of tongue. X 60. 



dorsal mucosa, the apical network being especially close. The lymph- 

 nodules of the posterior area are surrounded by meshes of lymphatics. 



The nerves of the tongue include three sets of fibres concerned in 

 conveying the impulses for common sensation, taste and motion. Those for 

 common sensation, derived from the trigeminus and glossopharyngeal nerves, 

 end in the lingual mucous membrane in the manner already described for the 

 oral mucosa (page 130), the papillae receiving fibres that confer great sen- 

 sibility. The gustatory impulses are collected by the fibres from the chorda 

 tympani and the glossopharyngeal, which are distributed to the anterior 

 two thirds and the posterior third respectively. Such fibres end in close 

 relation with the receptive neuroepithelial cells within the taste-buds (page 

 385). The motor fibres are from the hypoglossal nerve. As in other locali- 

 ties, so here, nonmedullated sympathetic fibres, destined for the blood-vessels 

 and glands, are included in many nerve-trunks along with medullated fibres. 



The Oral Glands. In addition to the large salivary glands which, 

 although pouring their secretion into the oral cavity, are situated outside of 

 the immediate walls of the mouth, certain groups of glands, for the most 

 part insignificant in size, lie within the oral wall and contribute secretions 



