Papilla and Nerves of the Tongue of the Frog. 283 



muscular contraction produces a constant acceleration of the 

 blood, if previously stagnating in them. I have not detected 

 any valves in these capillaries, such as are seen in some of the 

 larger veins of the frog's tongue. Muscular striae may be seen 

 at the upper and lower surfacesof the tongue, through the layer 

 of epithelium and cellular tissue. The contraction of the mus- 

 cular fibres may be frequently observed, either uncovered or 

 through the epithelium. I have examined them sometimes in 

 an animal under the influence of strychnia; in none of these 

 cases have I found either the zigzags described by Dumas and 

 Prevost as characteristic of muscular contractions, or the ap- 

 proximation of the transverse striae, as described by more re- 

 cent observers. 



To return to the nervous fibres. Burdach has employed 

 another means of unveiling the distribution of the nerves, which 

 consists in immersing the tongue for a few minutes in a solu- 

 tion of potassa, in the proportion of three or four drops of alkali 

 to an ounce of water. By this method the membrane of the 

 back of the tongue becomes rapidly converted into a transparent 

 viscous substance like the white of egg, which is easily removed, 

 leaving the subjacent parts nearly unaffected. By compressing 

 the tongue between two pieces of glass, we may trace the dis- 

 tribution of all the principal nervous branches of the organ. 

 The four nervous trunks advance forwards in a parallel direc- 

 tion to the tubercular extremity, giving off numerous branches 

 on their external sides, which branches subdivide and ramify 

 towards the borders of the organ. On their internal sides they 

 give off no branches, and appear to have no anastomoses one 

 with another. The same unilateral ramification is observed 

 with regard to the vascular canals, and may in a great measure 

 be accounted for by considering, that as they and the nerves 

 are all near the median line of the tongue, the parts to be sup- 

 plied are placed to the right and left sides of this line, and the 

 nervous and vascular trunks are only in proportion to the parts 

 to be supplied. 



The cervical nerves are seen to form numerous plexiform 

 anastomoses between their various branches, and to distribute 

 frequent loops composed of nearly single fibres among the 

 muscular part-;. The cranial pair ramify in a unilateral man- 

 ner until they attain the tubercular extremity, where branches 

 are given oH'on each side of the main trunks: Burdach states 

 that this nerve presents no plexiform arrangement like the 

 former, that a lew of its fibres at the extremities form curves 

 or arche.s, but that generally they terminate abruptly in a bush- 

 like nu\nner, hence his term "terminaisou en buisson." In 

 describing his process, Burdach has not concealed its defects in 



