828 THE NERVES. 



evidently motor ; the external possesses the ganglionic cells of a sensitive root ; 

 and the trunk they both form may be regarded as a mixed nerve. 



As will be observed, our view of the ganglion genie ulare differs from the 

 general opinion held with regard to it, inasmuch as we make it belong exclusively 

 to the great petrosal nerve, and not to the whole of the facial fasciculi. On the 

 other hand, the portio intermp/Ua of Wrisherg is not, in our opinion, the sensitive 

 root of the facial, the fibres of which we only look upon as motor ; it is not even 

 that of the great superficial petrosal nerve, of which it might, at the most, be con- 

 sidered as only an accessory filament. In the Horse, this ramuscule is extremely 

 attenuated, and can scarcely, if at all, be distinguished at its origin from tlie 

 filaments of the lateral root af the auditory nerve ; it is seen to enter the aqueduct 

 of Fallopius, and divide on the bend (or gangliform enlargement) of the facial 

 nerve into several gradually diminishing filaments, which are confounded with 

 the proper fibres of this nerve, or the ganglion geniculare. What a difference 

 there is between this arrangement, and that of the real sensitive roots opposite 

 the ganglia placed on their track ! 



The opinion which regards the nerve of Wrisberg as the sensitive root of the 

 facial has, we beUeve, been more particularly accredited by the apparent impos- 

 sibility of otherwise accounting for the sensibility this nerve possesses, even at 

 its exit from the stylo-mastoid foramen — that is, before contracting any anasto- 

 mosis with the fifth pair ; but this sensibility belongs exclusively to the fibres of 

 the communicating branch sent by the pneumogastric nerve, and not to the 

 fasciculi of the facial, as is proved by stimulating the latter outside the aqueduct 

 of Fallopius, after destroying the pneumogastric at its origin. If it is sought to 

 regard the intermediate nerve absolutely as a branch distinct from the original 

 filaments of the auditoiy, and if it be determined to make it a sensitive nerve, 

 then it must at least be admitted that it does not caiTy its sensibility beyond 

 the stylo-mastoid foramen, and that all its filaments disappear in the ramuscules 

 furnished by the facial in its interosseous course. Otherwise, it is known that 

 Longet considers this nerve as forming the small superficial petrosal branch and 

 the nervous filament of the stapedius muscle ; but he makes it a motor branch, 

 destined to supply the muscles of the middle ear. His idea is very ingenious, 

 and would assuredly be feasible if it were possible to follow the intermediate 

 nerve from its origin to the lateral column of the medulla oblongata ; but, 

 unfortunately, this is not the case, as the small ramuscule only appears to be 

 an offshoot of the fibres proper to the auditory nerve. 



To sum up, the great superficial petrosal nerve proceeds from the facial by 

 two roots — one motor, the other sensitive — assimilable, to a certain point, to the 

 roots of the spinal nerves. The first is furnished by the filaments of the seventh 

 pair ; while the second probably comes from the pneumogastric nerve, and has 

 annexed to it on its course the ganglion geniculare. The nerve of Wrisberg 

 perhaps concurs in the formation of this ganglion, but it is certainly not its 

 principal source. We ought to add, that a study of microscopical sections of the 

 isthmus has caused Mathias Duval to regard this nerve as an erratic portion of 

 the glosso-pharyngeal ; and Pierret has assimilated it to the vaso-motor filaments 

 which leave the lateral column of the spinal cord, to form the rami commtinicantes 

 of the great sympathetic, while the nucleus from which the branch proceeds 

 constitutes the anterior extremity of this column. A good deal of obscurity 

 still prevails with regard to the intermediate nerve, and Sapolini has proposed 

 to make it a thirteenth cranial nerve. 



