THE TONGUE, BY E. KLEIN. 521 



At the junction of the horizontal with the descending portions on 

 the border of each side of the tongue is found a slightly depressed 

 semi- circular spot, the periphery of which touches the posterior part of 

 the oval prominence. The surface is not smooth, but covered with 

 delicate, parallel, vertically arranged folds, on a few of which a filiform 

 papilla may be here and there discerned. 



This portion, as well as the above-mentioned minute folds at the 

 border of the tongue in man, and the group of papillae found at the 

 junction of the horizontal and descending portions of the tongue in 

 the cat, correspond to the peculiar organ described by Weber,* 

 and especially by J. C. Mayer, j in many mammals under the term of 

 papilla lingualis foliata. 



The papillae of the tongue of the rabbit appear considerably shorter 

 than those of man, and this is due to the absence of depressions in 

 the epithelium between them. 



The thickness of the epithelium diminishes from before backwards, 

 and also towards the sides ; yet, posterior to the oval prominence, is 

 as thick as at the apex of the tongue. 



The structure of the mucosa does not differ from that of man. Its 

 thickness also diminishes from the tip towards the oval prominence. 

 At the root of the tongue the fasciculi of muscular fibres situated 

 beneath the mucosa form a rectangular network, in the loculi of 

 which are contained the lobules of the acinous glands. The excretory 

 ducts of these glands penetrate the mucosa in a vertical direction to 

 reach the surface. Numerous small masses of lymph corpuscles are to 

 be met with around and between the lobules of the glands. In the 

 depressed semi-circular portion of the border of the tongue the lami- 

 nated pavement epithelium is much more attenuated on the margin of 

 the folds than on their sides. The depths of the folds amount to 

 0*45 of a millimeter, and the mucous membrane projects into them in 

 the form of an acute angle. 



The excretory ducts of large acinous glands open into the grooves 

 intermediate to the folds, the relation of which to the muscular 

 fasciculi is similar to that already described in the case of the 

 glands at the root of the tongue. A considerable number of nerves, 



* Weber, in Hildebrandt's Lehrbuch der Anatomie, Band., iv, 4. Aufl. 

 p. 150. 



f J. C. Mayer, Untersuchungen aus dem Gebiele der Anatomie, etc. 

 Bonn, 1842, p. 25. 



