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XLVI. Microscopic Exanmiation of the. Papillcv and Nerves 



of the Tongueofthe Frog, "with Observations on the Mechanism 



of Taste.' By Augustus Walleh, M.D.* 

 [With a Plate.] 

 T HAVE described in some former observations the appear- 

 -■■ ances presented by the papillae, the vascular and muscular 

 parts of the frog's tongue. At present I propose to examine 

 it in reference to its functions as an organ of taste, and to study 

 those portions of it in particular which enable it to perform 

 its sensorial offices. As these are mainly carried on by means 

 of nerves distributed within it, which collect and convey to 

 the brain the gustatory impressions which are produced upon 

 its surface, our attention will be principally directed to the 

 ultimate ramifications of the nerves, and to the structure of 

 those parts whence the sensations arise. This investigation is 

 the more interesting from the circumstance of the minute 

 anatomy of the ultimate ramifications of the optic, auditor}', 

 olfactory and the common sensitive nerves having been de- 

 scribed with great care in man as well as the lower animals, 

 whereas the structure of the gustatory nerves has been as yet 

 unascertained. It is not from the unimportance of the subject 

 in the estimation of physiologists that such is the case, as it 

 presents some peculiarities with regard to its nervous struc- 

 ture of great interest, but that the microscopic inspection of a 

 soft, fleshy and opake body, like the tongue in most animals, 

 offered greater obstacles than any of the other organs. 



Valentin states that he has been unable to obtain a distinct 

 view of the terminal plexus and loops of the nerves of the 

 tongue. Burdach, who has so carefully examined the nerves 

 of the frog's tongue, makes nearly the same observation ; for 

 he expressly mentions that he was unable to examine the mu- 

 cous membrane of the upper surface of the tongue, on account 

 of its thickness and opacity. I hope to succeed in demon- 

 strating that the organ of taste, far from being the most diffi- 

 cult to examine, is the most accessible, and that the beautiful 

 and simple mechanism of taste may be followed in the depth 

 of the tissues during the continuance of life. 



In briefly recapitulating the principal points that have al- 

 ready been ascertained respecting the structure and functions 

 of the tongue, we find — 



1. That anatomists distinguish three kinds of elevations upon 

 the human tongue, viz. the conical, the fungiforn), and the lenti- 

 cular papillae. The conical papillae are the most numerous, the 

 smallest, and the most liable to change under the influence of 

 * Communicated by the .Author. 



