30 ON THE NERVOUS SYSTEM IV. 



enters the ganglion of the fifth pair, but immediately separates again from it, and 

 is continued as the tympanic branch of the fifth, till it joins the laryngeal branch 

 of the vagus. This laryngeal branch of the vagus is given off by the glosso- 

 pharyngeal branch of the latter nerve, and its anastomosis with the facial may 

 be compared to the similar connection of the glosso-pharyngeal with the facial 

 in the human body." * Vogt, in his excellent memoir on the nervous system 

 of Reptiles, describes this nerve in Toads, after leaving the ganglion, as " winding 

 around the labyrinth to the cavitas tympani, behind which it meets with a 

 branch of the glosso-pharyngeus ; these two united nerves bend over the articu- 

 lation of the lower jaw, and branch off to the skin and muscles, just as Volkman 

 has described it." f Stannius describes the nerve somewhat more fully, as follows : 

 " Another peculiarity of Fishes is found in this, that the facial nerve, which corre- 

 sponds in a great measure with the opercular branch of this class, sends a lower 

 maxillary nerve, which accompanies the alveolar branch of the trigeminus and 

 anastomoses with it. In all Anourous Batrachians, this facial or jugular nerve re- 

 ceives an anastomosing filament from the first branch (analogous to the glosso- 

 pharyngeal) of the vagus. Its first branch is ordinarily destined to the skin com- 

 prised between the membrane of the tympanum and the angle of the mouth 

 (auricular branch) ; the second is the lower alveolar just mentioned, and the third 

 is distributed in part to the sterno-hyoid, and in part to the skin of the thoracic 

 region." } The following may be added to the quotation made above from Cuvier : 

 " In tailless Batrachians, a portion of the facial seems to be furnished by the fifth 

 pair xmder the form of a fourth branch escaping from the semilunar ganglion." § 

 This, however, he states on the authority of Fischer. 



According to my dissections, the following appears to be a true description of 

 the origin, connections, and ultimate distribution of the so-called facial nerve in the 

 species of Frog here noticed. The manner in which it becomes connected with the 

 Gasserian ganglion has already been noticed (p. 27). It is the smallest of the branches 

 derived from the ganglion, which it leaves at its inferior angle, and is directed out- 

 wards, passing around the bony walls of the vestibule ; it passes backwards over the 

 columella, with which it is in close contact, and, while still beneath the tympanic 

 bony circle, is joined by a branch from the glosso-pharyngeal of the vagus, or by 

 a branch from a common trunk, which is divided into the glosso-pharyngeal and 

 this anastomosing branch. (Plate I. Fig. 1, c; Plate II. Fig. 2, g.) The single 

 trunk formed by the union of these two branches is directed downwards and back- 

 wards behind the tympanic cavity, to just above the angle of the jaw. After it has 

 reached this point, it is far from easy to trace its terminal branches, but after many 

 dissections, both with and witliout water acidulated with dilute nitric acid, the fol- 

 lowing distribution has been made out, and it goes to prove, that, although the 

 nerve in question is doubtless the homologue of the facial in Man and Mammals, 



* Physiol., Baly's Trans., Vol. I. p. 834. 



+ Vogt, Beitrage zur Nevrologie der Reptilien, p. 52. 



t Siebold et Stannius, Man. d'Anat. Comp., Paris, 1850, Tom. II. p. 204. 



§ Cuvier, Lefons, Tom. III. p. 207. 



