i 5 6 



NORMAL HISTOLOGY. 



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

 cells are prolonged as slender, sometimes forked, processes ; the 

 minute swellings or varicosities which these extensions often exhibit 

 are supposed to indicate the direct connection of the neuro-epithelial 

 cells with the fibres of the nerve of the special sense of taste. It 

 must be remembered, however, that no such continuity has been, as 

 yet, positively demonstrated. The submucous and interfascicular 

 tissue of the tongue contains 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, although a group of small mucous glands (Nuhn's) is found 

 near the tip. The ducts of those at the root of the tongue are some- 

 times 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, 1-5 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 



Salivary corpuscles & *- 



from human saliva: x, spherical masses of denser structure. 



group of corpuscles near Among the formed elements observed in the 



epithelial cells; y, cor- 

 puscle which has burst, saliva the so-called salivary corpuscles are 

 allowing granules to es- consp i cuous> These are spherical bodies, some- 



cape ; z, salivary cor- ~ 



puscie highly magnified, what larger than the leucocytes, and possess a 

 showing granules and distinct nucleus and minute granules within the 



nucleus. m 



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. 



