NORMAL HISTOLOGY. 



r as the free surface. The inner or central ends of the gustatory 

 cells are prolonged as slender nervous processes, which are often 

 beset with minute swellings or varicosities.) These processes end in 

 close association, but not continuity, with the terminal axis-cylinders 

 : composing the intrabulbar ramifications of the fibres prTrieglosso- 

 pharyngeal nerve, the nerve of the special sense of taste. 



The submucous and interfascicular tissue of the tongue con- 

 tains numerous glands, both of the mucous and of the serous type. 

 The mucous glands resemble those of other parts of the oral 

 cavity, being small racemose clusters of acini more or less filled 

 with clear mucoid secretion. They are situated in the deeper layers 

 of the submucous tissue, as well as between the bundles of the 

 muscle-fibres, principally in the posterior part of the tongue, al- 

 though a group of small mucous glands (Nuhn's) is found near the 

 tip. The ducts of those at the root of the tongue are sometimes 

 lined by ciliated epithelium. 



The serous glands are limited to the immediate neighborhood 

 of the circumvallate and of the foliate papillae. The acini appear 

 darkly granular and pour out a thin watery secretion well adapted to 

 aid in producing gustatory impressions. 



The mucous membrane covering the root of the tongue contains 

 also much adenoid tissue, which occurs either as diffuse masses 

 or as circumscribed irregularly spherical lymph-follicles, 15 mm. in 

 diameter. The position of these follicles is fre- 

 quently indicated by slight elevations of the 

 mucosa, in the centre of which a minute pit leads 

 into the interior of the lymphatic crypt. The 

 epithelium lining such recesses is completely in- 

 filtrated with lymphoid cells, while the surround- 

 ing diffuse adenoid tissue contains several minute 

 spherical masses of denser structure. 



Among the formed elements observed in the 

 saliva the so-called salivary corpuscles are 

 conspicuous. These are spherical bodies, some- 

 what larger than the leucocytes, and possess a 

 distinct nucleus and minute granules within the 

 cell-contents ; under high amplification these gran- 

 ules exhibit the agitation characteristic of the molecular or Brown- 

 ian motion. The salivary corpuscles are derived from the adenoid 

 tissue of the mouth, and are really escaped lymphoid cells, which, 

 in consequence of the action of the saliva, become swollen by the 

 imbibition of a fluid less dense than the tissue-juices ; they thereupon 

 exhibit a reaction similar to that seen when the colorless blood-cell is 

 treated with water. 



FIG. 191. 



Salivary corpuscles 

 from human saliva: x, 

 group of corpuscles near 

 epithelial cells; y, cor- 

 puscle which has burst, 

 allowing granules to es- 

 cape; z, salivary cor- 

 puscle highly magnified, 

 showing granules and 

 nucleus. 



