Dec, 191(3] Profundus and Gasserian Ganglia in Plethodon 41 



deles the facial is separate. A ramus opthalmicus profundus 

 is present and so named in almost every adult form of Urodele 

 described (e. g. Coghill '12, Amblystoma). 



Strong ('95) does not designate the opthalmic trunk arising 

 from the Gasserian ganglion in Rana, as r. oph. profundus. 

 He calls it the r. opthalmicus trigeminus. In discussing the 

 problem of the profundus however, he seems (p. 193) to partially 

 agree with Wilder ('92) who took the position that in Amphibia 

 and the higher vertebrates the r. op. sup. V is fused with the 

 r. op. profundus of the Elasmobranchs to form the r. op. trige- 

 minus or supra-orbital trunk. Landacre ('12) finds that 

 in the 8 mm. Rana embryo the r. opthalmicus comes almost 

 entirely from the profundus portion of the ganglion, but in 

 later stages derives some fibers from the Gasserian. 



In liighor lerrestial vertebrates neither the r. opthalmicus 

 profundus nor its ganglion are distinct in adult forms. A 

 separate profundus ganglion has been found in the cat and the 

 guinea pig embryos and Ewart ('90) found vestiges of it in 

 the ") mo. human embryo. The name ramus opthalmicus is 

 the common term for the anterior trunk from the trigeminal 

 or semi-lunar ganglion in higher vertebrates. The word 

 profundus has dropped from the terminology of this complex 

 and no hint is given that some fibers of this opthalmic trunk 

 may have their origin in the profundus portion of the ganglion. 

 The real morphology and origin of this nerve trunk is not known 

 for the higher vertebrates and such forms as these would 

 logically be the next to study after such a form as the Urodele 

 where a r. opth. profundus is present and so named. The 

 difficulty of obtaining a close series of embryos of the higher 

 vertebrates makes the problem a serious one. The results 

 of such studies would throw light on the question of what 

 happens to the region innervated by a nerve when the ganglion 

 on that nerve disappears or fuses with another. Such studies 

 would also help to clear up the question of the fate of the pro- 

 fundus ganglion in phylogeny. It is evident from the summary 

 given above that the urodeles occupy an intermediate position 

 between types with a separate profundus ganglion and a distinct 

 r. oph. prof, nerve in the adult and those types with neither 

 profundus ganglion nor nerve in the adult ; in that the urodeles 

 have both structures separate in the embryo and in the adult 



