ever, appears to me a very suspicious one. The patient might still have 

 tasted, by means of the lingual nerve, and the sense would only have been 

 weakened. The division of one of the nerves of the ninth pair could 

 render insensible, only that half of the tongue to which it is distributed, 

 the other half would continue fully to possess the faculty of taste. 



The application of metals to the different nervous filaments distributed 

 to the tongue, ought, to inform us of their different uses, if, as Humboldt 

 suspects, the galvanic excitement of the nerves of motion, alone produces 

 contractions. To ascertain the truth of this conjecture, I placed a plate 

 of zinc within the skull, under the trunk of the nerve of the fifth pair, in 

 a dog that had been killed a few minutes before, and that still retained its 

 warmth 5 the muscles of the tongue, under which a piece of silver was 

 placed, quivered very slightly; those of the forehead and temples in con- 

 tact with the same metal experienced very sensible contractions, when- 

 ever a communication was made by means of an iron rod. This experi- 

 ment showed, that the lingual branch of this nerve was, almost solely, 

 subservent to the sensation of taste, which agrees with the opinion of 

 most physiologists, and the same inference may be drawn from the ana- 

 tomical knowledge of the situation of this nerve, which, almost entire- 

 ly, terminates in the papilla of the membrane of the tongue, and sends 

 very few filaments to the muscles of that organ. But though the galvanic 

 irritation applied to the hypoglossal nerve affected the whole tongue, in 

 a convulsive manner, I did not think myself justified to infer, that this 

 nerve was solely destined to perform its motions; as this nervous trunk 

 might in this part of the body, as it does in others, contain filaments both 

 of sensation and motion. 



The tongue though an azygous organ is formed of parts completely 

 symmetrical; there are, on each side, four muscles (stylo, hyo, genio- 

 giossi, and lingual;} three nerves (lingual, glosso-pharyngeal, and hyfioglossal;) 

 a ranine artery and vein; and a set of lymphatic vessels precisely alike. 

 All these parts, by their union, form a fleshy body of a close texture, and 

 not easily unravelled, similar to that of the ventricles of the heart, endowed 

 with a considerable degree of mobility, in consequence of the numerous 

 vessels and nerves entering into its substance*. If we compare their num- 

 ber and size with the small bulk of the organ, it will be readily under- 

 stood, that, as no part of the bode can execute more frequent, more ex- 

 tensive, and more varied motions, so no one receives more vessels and 

 nerves. A middle line separates and marks the limits of the two halves 

 of the tongue, which anatomically and physiologically considered, ap- 

 pear formed of two distinct organs in juxta-position. 



This independence of the two parts of the tongue is confirmed by the 

 phenomena of disease; in hemiplegia, the side of the tongue correspond- 



* HAILER concluded that the tongue possesses irritability. BLUMEXBACH has lately 

 determined the point by direct experiment. He caused the tongue of a four-year-old 

 ox, which had been killed in the usual way, to be cutout while the animal was jet warm, 

 and at the same time, the heart, in order that he might compare the oscillatory motions 

 of both viscera; and when both were excited at the same time by mechanical stimuli, 

 the tongue appeared to survive the heart by more than seven minutes, and so vivid were 

 its movements, when cut across after its separation, that its motions might be compared 

 to those of the tail of a mutilated snake. The same phenomena were remarkable in the 

 divided tongue of other animals, on the application of mechanical or chemical stimuli ; 

 and also in that of a boy which had been bit oft' during 1 a fit of violent epilepsy Cop- 

 land. 



2 K 



