40 Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
of the Gasserion ganglion cannot represent the ciliary ganglion of the adult. My 
observations go only as far back as the end of the fourth week (embryo Br,.), at 
which time I believe the Gasserian ganglion has a rounded upper, or anterior end, 
from which a relatively thick nerve, with many nuclei among its fibres, passes 
upwards. This nerve, which represents the nasal, takes origin from a point in 
front of the summit of the ganglion. Professor His,* in a description of the 
nerves of this same embryo describes and figures a ganglion on the ophthalmic 
nerve.t I have not, however, been able to find any definite collection of cells 
which might represent it. At my request Professor His has, with great courtesy 
again examined the sections, and has been so kind as to write me a letter in which 
he says that the description written in 1888 corresponds to his opinion at the 
time, but that now he finds it difficult to determine whether the nuclei present 
represent ganglion cells, or belong to the nerve sheath. Since I was unable to 
satisfy myself of the presence of a ciliary ganglion in Ru., a still older stage than 
Br;., I believe that the nuclei present among the fibres of the ophthalmic nerve in 
the latter, cannot represent a ciliary ganglion, but rather that they represent the 
cells of the so-called ‘‘nerventfiihrendes Gewebe,” which appears before the axis- 
cylinders of the nerves are present, and from which the nuclei of the white 
substance of Schwann are said to be developed. A cellular stage in the ophthalmic 
nerve is described by Béraneck{ for the chick embryo and also by Goronowitsch,§ 
who, however, does not consider true nerves to be present until axis-cylinders are 
formed. Kuffer|| also described these cellular tracts in Petromyzon, and other 
authors have mentioned them in various other lower animals. 
In a rat embryo of the twelfth day the Gasserian ganglion is found to have 
a rounded upper end from which a cellular cord passes up behind the eyball, a 
distance of 0.1mm. The cells of this cord do not seem to differ much from those 
of the ganglion itself. The cord does not, as figured by Professor His for his 
human embryo A, end in a swollen extremity. No fibres were detected among 
the cells of this cord. Also in this embryo the two other divisions of the fifth 
nerve are present, and possess some fibres in them, and are thus farther advanced 
than in Professor His’s embryo A. In a rat embryo, just a little more advanced 
* «Geschichte des Gehirns sowie der centralen und peripherischen Nervenbahnen beim Menschlichen 
Embryo,’ Abhandlungen der Konigl. Sachsischen Gesellschaft der Wissenschaften, Bd. xiy., 1888, p. 372, 
and fig. 4, plate 1. 
+ Professor F. Mall has also described a ciliary ganglion as present on the ophthalmic division of the 
fifth nerve in a human embryo of 26 days. Journal of Morphology, vol. v., p. 495, 1891. 
{ ‘‘ Etude sur les Replis Médullaires du Poulet,’”’ Recueil Zoologique Suisse, 1888, vol. iv., p. 336. 
§ ‘‘ Untersuchungen iiber die Entwicklung der sog. ‘Ganglienleisten’ im Kopfe der Végelem- 
bryonen,”’ Morphologisches Jahrbuch, 1893, Bd. 20, p. 187. 
|| ‘‘ Die Entwicklung von Petromyzon Planeri,” Archiv fiir Mikroskopische Anatomie, 1890, Bd. 35. 
See also ‘‘ Studien zur yergleichenden Entwicklungsgeschichte des Kopfes der Kranisten,” Heft. ii. 
Miunchen, 1895. 
