Drxon— On the Development of the Branches of the Fifth Cranial Nerve in Man. 21 
have been noted. The mode of origin of these ganglia in mammals must still 
be looked upon as an unanswered question; but at all events it may be asserted 
that they resemble spinal ganglia neither in their mode of origin, nor, as Retzius 
has shown, in their microscopic structure. 
In this Paper the branches of the fifth nerve are described as growing 
out from the Gasserian ganglion in the manner described by Professor His, and 
the fibres which compose them are referred to as processes of the cells in this 
ganglion. 
Goronowitsch* has recently shown in the chick embryo, that before the axis- 
cylinder processes are formed, and therefore before true nerves are present, cords 
of cells derived from the mesenchyme occupy the positions of the future nerves. 
These tracts of mesenchyme he called ‘ Nervenfiihrendes Gewebe,” and he 
considers that later on they form the different parts of the nerve sheaths, the 
axis-cylinders alone arising from the ganglionic cells. Dohrnt on the other hand, 
from observations on Elasmobranch embryos, considers, that the axis-cylinders 
are not processes of the ganglionic cells, as they are usually believed to be, 
and that the nerves arise by cells, uniting together in a chain-like manner. 
More recently still, Sedgwick in his attack on the cellular theory of develop- 
ment, from observations also on Elasmobranchs, states that nerves are formed 
by the fibres of the mesoderm reticulum falling into line. These fibres, according 
to Sedgwick, first become re-arranged to form nerves in the region of the ganglia, 
and so it thus comes about that the nerves appear to grow out from the latter, 
but the axis-cylinders are not processes of ganglionic cells. All observers agree 
that the nerves, no matter how formed, appear to grow out from the ganglia. 
It would appear to be an assured fact that in lower animals before the axis- 
cylinders are formed, cellular tracts—“ nerves”—are present. These have been 
noticed by many authors in different animals, and Kupffer§ has described and 
figured such for the fifth nerve in Petromyzon. Kupffer regards them as out- 
growths from the ganglia, while Goronowitch apparently considers similar 
structures in the chick to be chiefly mesodermic in origin. Speaking more 
recently of these chains of cells in the case of the spinal nerves Kupfer 
* Untersuchungen iiber die Entwicklung der sog. “‘ Ganglienleisten’”’ im Kopfe der Vogelembryonen. 
Morphologisches Jahrbuch, 1898. Bd. 20. p. 187. 
+ ‘“‘ Nervenfaser und Ganglienzellen. Histogienetische Untersuchungen.”  Mittheilungen aus der 
Zoologischen Station zu Neapel. Bd. 10, p. 256. 
t ‘‘On the Inadequacy of the Cellular Theory of Development, and on the Early Development of 
Nerves, particularly of the Third Nerve, and of the Sympathetic in Elasmobranchii.” Quarterly Journal 
of Microscopical Science, vol. 37, 1894, p. 87. 
§ ‘‘ Die Entwicklung von Petromyzon Planeri.” Archiv fiir Microscopische Anatomie, 1890. Bd. 35 
p. 020. 
+ : E 2 
