IV. OF RANA PIPIENS. 27 



IV. Patheticus. (Plate I. Figs. 2 and 6, iv.) — This is certainly an independent 

 nerve, and at its origin conforms with the general description of the same nei"ve in 

 other animals. It arises behind the optic lobes, from the part corresponding in 

 position with the valve of Vieussens ; it perforates very obliquely the cartilaginous 

 lateral wall of the cranium, in front of the motor communis ; it runs parallel to 

 and in company with the ophthalmic nerve, and with a small branch of this last 

 seems to form an anastomosis (Plate II. Figs. 4, 5), and is described as forming 

 one by several writers ; it gives no branches, however, until it reaches the obliquus 

 superior muscle, in which it is wholly lost. 



Stannius describes this nerve as " distinct in the Anourous Batrachians, and as 

 distributed to the superior oblique ; but in Tritons and Salamanders it appears to 

 be entirely incorporated with the trigeminus, so that it is the ophthalmic branch 

 which furnishes filaments to this muscle." * Cuvier doubts the existence of any 

 communication between this and the ophthalmic nerve, and regards the supposed 

 anastomosis as merely an apposition, " quil ne qu'accole a ce nerf." f Vogt has 

 seen a filament of this nerve anastomose with the ganglion of the trigeminus in 

 Bufo pantherius. Fischer could not detect the existence of the patheticus in Sala- 

 maiidra terrestris, and therefore infers that it is derived from the ophthalmic branch 

 of the fifth, since this last supplies the superior oblique with its motor filaments. 



After repeated dissections, I am satisfied that the description of Cuvier is correct 

 as far as it relates to Rana pipiens, and that, however close the contact be between 

 the patheticus and the branch of the ophthalmic, no anastomosis really occurs ; 

 and am led, therefore, to the conclusion, that the patheticus, which in Tritons and 

 Salamanders is a branch of tlie trigeminus, is in Frogs a separate and independent 

 nerve. 



V. T>-igemi>u(s. (Plate I. Fig. 1, v. ; Plate II. Fig. 2, v.) — This has always at- 

 tracted the attention of anatomists and physiologists, on account of its extended dis- 

 tribution, its connection with other nerves, and its relations to the organs of sense ; 

 also on account of its great resemblance, in the existence of a ganglion, to a common 

 spinal nerve. In Frogs it becomes especially interesting, since, in addition to the 

 three principal trunks found in other animals (namely, the ophthalmic, superior 

 maxillary, and mandibular), it includes the facial as well as one of the motor 

 nerves of the eye, namely, the abducens. The different roots which are united in 

 the trigeminus are widely separated from each other, and, as here described, include 

 all the roots arising from the medulla oblongata, and which become connected with 

 the trigeminal ganglion. The principal one, and which corresponds with the 

 tri"eminus proper, arises from the most convex part of the lateral portion of the 

 medulla oblongata, by several distinct ftisciculi, which unite and form a single 

 trunk, that is directed obliquely forwards and enters the ganglion ; this trunk 

 includes both motor and sensitive filaments. The second is the facial (Plate 

 I. Fig. 1, a), which emerges from the medulla in close contact with the audi- 

 tory nerve, and, after accompanying it for a short distance, is directed obliquely 



* Siebold et Stannius, Nouveau Manuel d'Anatomie Comparec, Tom. II. p. 203. 

 t I.eqons, Tom. III. p. 188. 



