32 • ON THE NERVOUS SYSTEM lY. 



properties, is quite different from the same nerve in the human body ; in Man it is 

 almost wholly motor, having no sensitive filaments, except such as are derived from 

 anastomosis, and which are intended to give a muscle its ordinary sensibility ; thus 

 its distribution is entirely muscular. In Frogs, on the contrary, as far as observed, 

 its distribution is Avholly cutaneous, its fibres having been traced to the skin about 

 the tympanum, the angles of the mouth, the submaxillary and lateral jugular region. 



The description given above, when compared with those of others which precede 

 it, corresponds with that of Cuvier and of Vogt as to the origin of its vagal and tri- 

 geminal branches. Cuvier says nothing of its ultimate distribution, other than 

 would lead to the inference that it has the ordinary distribution of the facialis. 

 Vogt's statement, likewise that of Volkman, that it is distributed to the muscles of 

 the lower jaw, I have not been able to verify. There does not appear any reason 

 from analogy, or from the dissections just described, why Volkman should apply the 

 term laryngeal to the anastomosing branch from the vagus. An anastomosis exists 

 between the facial and glosso-pharyngeai nerves in the human body, but no branch 

 termed laryngeal is given off from them, nor is the nerve in question entitled to 

 that name from its distribution. The only true laryngeal nerve in Frogs, as will 

 be seen, is given off, not by the nerve just referred to, but by the third or visceral 

 trunk of the vagus, and is the homologue of the recurrent in Man. The descrip- 

 tion given by Stannius is certainly the most complete, and he is almost the only one 

 who seems to have traced the branches to the skin. 



The anatomy of the facialis in Salmo fario, as given by Agassiz after his original 

 dissections, shows the existence in this Fish of a condition similar to that of Frogs. 

 " The facial nerve escapes from the brain by the lateral furrow of the medulla ob- 

 longata ; it is intimately connected with the root of the acoustic, and is separated 

 from the trigeminus, but instead of following the course of the acoustic, its fibres 

 pass obliquely towards the ganglion of Gasser, and, uniting to its inferior face, to 

 the fibres of the trigeminus, and especially to the suborbitar branch of that nerve. 

 Although there is evidently a mixture of these two nerves, we can nevertheless follow 

 a great part of the fibres of the facial, which pass directly to the inferior face of 

 the ganglion, into a single nerve which escapes from the cranium through the 

 hole in the great wing of the sphenoid in company with the trigeminus." * While 

 the ultimate distribution is different in the two, yet Frogs and Trouts have this in 

 common, that the facial becomes an appendage of the ganglion of Gasser, and as 

 in other Fishes it becomes more or less blended with the trigeminus. As it is in no 

 instance bodily combined with any other nerve, we may safely conclude that, phil- 

 osophically considered, the facial in Man is a dismemberment of the trigeminus. 



VI. Auditory. (Plate I. Fig, 1, vi.) — This nerve likewise arises from the 

 lateral portion of the medulla oblongata in two portions closely approximated to 

 each other. They enter the vestibule, sometimes still united by a single foramen, 

 at others slightly separated, and then by two foramina. I have noticed one of these 

 conditions on the right and the other on the left of the same individual. After 

 entering the vestibule, the two roots separate from each other, and are distributed 



* Agassiz and Vogt, Anat. des Saltnones, p. 168 ; also Table M, Fig. XVI. 



