14 SPECIAL HISTOLOGY. 



lower surface, and lie for the most part immediately beneath the 

 Fig. 172. 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-glossi, at the 

 septum, at the root of the tongue, and 

 under the mucous membrane. 



[In the tongue of the Frog very beau- 

 tiful instances of division of the trans- 

 versely striated fibres occur (fig. 172), of 

 which I have not been able to find any 

 certain trace in man. Occasionally, how- 

 ever, 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 caecum 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 papillae circumvallatae consist, when they are well deve- 

 loped, of a central round papilla, flattened at the end, having 

 a diameter of \ — 1'" and \ — J'", or even £"' high; and of a 

 lower uniform wall, J — J'" broad, which closely surrounds the 

 papilla, particularly at its base. These papillce, however, vary 

 much in number, size, and position, and occasionally pass into 

 the fungiform kind ; which is especially true of the posterior 

 ones lying in the foramen ccecum or Morgagnii. The papillae, an- 

 terior to the circumvallatce, are arranged in more or less regular 



Fig. 172. A branched primitive muscular bundle, of 0-01 8'", from the tongue of 

 the Frog, x 350. 



