406 ORGANS OF THE SENSES. 



is not only a nerve of sensibility, but one of special sensibility, as 

 it is the principal organ of taste. Lussana and Inzani mention 

 (" Archives de Physiologic," 1869 and 1872) the case of a person 

 in whom the chorda tympani had been cut in an operation per- 

 formed on the middle ear by a quack. After the operation the 

 Cterior two-thirds of the corresponding half of the tongue were 

 nd to have lost the sense of taste, while retaining an unim- 

 paired sensibility to touch and to pain. Lussana has since collected 

 several similar observations in cases in which the paralysis of the 

 facial nerve, following a wound or an operation, was accompanied 

 by the partial loss of the sense of taste. Lussana made the experi- 

 ment of performing the bilateral extirpation of the glosso-pha- 

 ryngeal nerves in a dog, and afterwards cutting the two chordae 

 tympani. The result of this experiment showed that the sense of 

 taste entirely disappeared while the posterior portion of the tongue 

 retained its sensibility to touch and pain. In a counter-experiment 

 Schiif ( Physiologic de la Digestion," Florence, 1866, Vol. I.) 

 succeeded in cutting the lingual nerve above its junction with the 

 chorda tympani, close to the base of the skull; the tactile and 

 painful sensibility of the corresponding portion of the tongue 

 ceased entirely, while traces of the sense of taste remained; these, 

 though sometimes extremely slight, could be always recognized by 

 the movements and contortions of the animal subjected to the in- 

 fluence of acid or bitter substances. 



Lussaua and Schiff conclude from this, that the lingual nerve 

 governs only the general sensibility of that portion of the tongue through 

 which it spreads, and has no gustatory fibres of its own, these Jibres 

 proceeding from the chorda tympani. 



This conclusion, unfortunately, loses something of its value 

 from the circumstance that it necessitates a condition which it is 

 almost impossible to satisfy in the present state of science. What 

 course do the gustatory n'bres of the chorda of the tympani follow 

 in proceeding to the nerve centres? Are they represented by the 

 intermediate nerve of Wrisberg ? or do they arise from an intra- 

 cranial anastomosis of the facial nerve with a sensory nerve, a 

 branch of the trifacial? 



Lussana has no hesitation in adopting the former hypothesis, 

 and he has helped to strengthen it by a number of experiments, in 

 some of which the trifacial was entirely destroyed, the taste re- 

 maining uninjured, while, in others, intra-cranial lesions (lesions 

 of central portion) of the facial nerve are accompanied by a 

 change in the sense of taste. 



The number of experiments, however, which have produced an 

 entirely opposite result are much more numerous than these. The 

 cases reported by Davaine, Gueneau de Mussy, and Roux, the 

 experiments made by Biffi and Morganti, and Schiff's researches, 1 

 all seem to prove that lesion of the central portion of the facial 

 nerve produces no effect upon the sense of taste; and that, conse- 



i See Art. "Gofrt," in the ''Nouveau Dictionnaire de Mdd. et de Chirur. 

 Pratiques," Vol. XVI. 



