38 Dixon— On the Development of the Branches of the Fifth Cranial Nerve in Man. 
Ewart considers that he has proved the existence of this oculo-nasal ganglion in a 
five-months human fcetus, in which he has found a collection of cells lying under 
cover of the inner portion of the Gasserian ganglion. It seems more probable 
from my observations that what he has found in this foetus represents a cellular 
connexion, which exists in the embryo, between the otic and Meckel’s ganglion, 
and which has the position described. This will be discussed again when we 
come to consider the otic and Meckel’s ganglion. 
It is then quite certain that in Elasmobranchs, at all events, the nasal nerve 
or ramus profundus is primitively not a branch of the Gasserian ganglion, but 
that it is a separate nerve with a separate ganglion, and that it may persist as 
such even in the adult of some forms (Ewart). 
‘The independent nature of the nasal nerve is not, however, a peculiarity of 
Elasmobranchs, as a number of observers have described it, having a more or less 
similar origin in a variety of other animals. 
Thus Shipley,* Scott,t Ahlborn,t Kupffer,§ and others have described the 
special ganglion of the ramus profundus in Marsipobranchu either for the embryo 
or for the adult, while Kupffer|| also describes similar conditions in Ganoidei 
(Accipenser). In Reptilia we have the observations of Hoffman] on this point ; 
and in Aves those of Beraneck.** According to the observations of Plessen and 
Rabinovicz,t}+ Salamandra maculata forms an exception, as these authors state that 
in this animal, although two distinct ganglia are present for the fifth cranial nerve, 
the nasal and mandibular nerves arise from the main ganglion, while the fronto- 
maxillaris takes origin from the accessory one. The observations of Wieder- 
sheimt} and Kingsley§§ in other amphibia do not agree with those of Plessen and 
Rabinovicz; further, Oliver Strong|||| has recently stated that Plessen and Rabinovicz 
have mistaken a ganglion, which really belongs to the superficial ophthalmic and 
buccal branches of the seventh nerve, for an accessory ganglion of the trigeminal. 
* «Some points in the Development of Petromyzon Fluviatilis,” Quarterly Journal of Microscopical 
Science, vol. xxvii., p. 325, and fig. 22, plate xxv. 
+ ‘‘Embryology of Petromyzon,” Journal of Morphology, 1887, vol. 1., p. 278, and fig. 40, plate xr. 
aac Uber den Ursprung und Austritt der Hirnnervyen yon Petromyzon,” Zeit. fiir wiss. Zool., 1884. 
Bd. xl, p. 286. 
§ ‘‘ Studien zur vergleichenden Entwicklungsgeschichte des Kopfes der Kranioten,” Miinchen, 1894, 
Heft. ii., p. 72. See also Heft. iii. ‘‘ Die Entwicklung der Kopfnerven von Ammocoetes Planeri,’’ which 
has appeared since this paper was written. || Loc. cet., p. 72. 
q ‘‘ Weitere Untersuchungen zur Entwicklungsgeschichte der Reptilien,” Morphologisches Jahrbuch, 
1886, Bd. xi. 
** « Htude sur les replis medullaires du Poulet,” Recueil Zoologique Suisse, 1888, vol. iv., p. 387. 
tt ‘ Die Kopfnerven yon Salamandra maculata,’ Miinchen, 1891, p. 8. 
tt ‘‘ Lehrbruch der vergleichenden Anatomie,” Jena, 1886, p. 338. 
§§ ‘‘ The head of an Embryo Amphiuma.” The American Naturalist, August, 1892, p. 677. 
||| <* Cranial nerves of Amphibia.’”’ Journal of Morphology, vol. x., 1895, pp. 162, 108. 
