446 



SPECIAL HISTOLOGY. 



the lateral borders of the tongue, and in part seems to unite -with the 

 larger bundles of the stjjlo-glossus. 



If, after thus describing the separate muscles of the tongue, both ex- 

 ternal and internal, we consider the general structure of the organ, it 

 appears that its proper substance presents essentially only three sets of 

 muscular fibres, which may be denominated perpendicular, transverse, 

 and longitudinal. The perpendicular fibres arise from the genio-glossi 

 in the middle ; from the lingualis and hjo^glossus laterally ; at the 

 apex, also, from the perpendicularis ; and they form from the point to 

 the root, a great number of transverse lamellxe, occupying nearly the 

 entire breadth of the halves of the tongue, whose fibres pass in general 

 from the lower surface to the upper. The transverse fibres, derived 

 from the transversus and in part from the stylo-glossus, are inserted in 

 so many, usually somewhat thicker, lamellce, between the above named, 

 commencing at the sejjtum and ending at the lateral edges and partly 

 upon the surface; the longitudinal fibres, lastly, belong to the lingualis 

 superior {chondro-glossus), the lingualis inferior and stylo-glossus, cover 

 the upper surface, the margin, and in part the lower surface, and lie for 

 Fis- 172. the most part immediately beneath the mucous 



membrane. The various layers of muscles of the 

 tongue are invariably separated from one another 

 by a thin perimysium, and where larger vessels 

 and nerves run, by thicker masses of connective 

 tissue ; besides which, there are in many localities, 

 larger or smaller aggregations of common fat- 

 cells, which especially abound between the genio- 

 ^M glossi at the septum, at the root of the tongue, 

 '"" and under the mucous membrane. 



In the tongue of the Frog very beautiful in- 

 stances of division of the transversely striated 

 fibres occur (Fig. 172), of which I have not been 

 able to find any certain trace in man. Occasion- 

 ally, however, it has seemed to me that the fibres 

 of the genio-glossus exhibited divisions shortly 

 before their passage into tendinous bands. 



§ 132. On the dorsum of the tongue, from the foramen ccecum as far 

 as its point, the mucous membrane differs from that of the rest of the 

 oral cavity, in being very closely united with the subjacent muscular 

 tissue, and in possessing a great number of processes, the well-known 

 lingual or gustatory papilla;. The 6-12 papillce circumvallatce consist, 



Fig. 172. — A branched primitive muscular bundle, of 0-018 of a line, from the tongue of 

 the Frog ; magnified 350 diameters. 



