Drxon—On the Development of the Branches of the Fifth Cranial Nerve in Man, 41 
than the last one, we have, in place of the cellular cord, a tract in which some 
fibres are present, although many cells still remain. In an embryo a little longer 
still, we find a better marked nasal nerve, and the frontal, which is now begin- 
ning to develop, is in a condition very like that in which we have seen tie nasal 
in the second stage, 7.e. it is represented by a tract chiefly composed of cells, but 
with a few fibres among them. As the fibres of the nerves increase in number, 
the nuclei are found in section more on the outside, while the fibres are collected 
towards the centre. 
In the rat, therefore, as in man, nasal and frontal nerves are branches of the 
Gasserian ganglion. In both cases we have, at first, relatively a large number of 
nuclei present among the nerve fibres. Later on these disappear. A ganglion 
for these nerves, distinct from the Gasserian, does not exist in the human or rat 
embryos. The forward cellular prolongation of the Gasserian ganglion, described 
by Professor His, does not represent such a ganglion as Beard has suggested. The 
ciliary ganglion of the adult is not present in a recognisable form at the time of 
origin of these nerves. 
In the guinea-pig, Professor G. Chiarugi,* describes an early stage in which 
there is a distinct ophthalmic ganglion forming later a conical bed on the 
Gasserian ganglion, and from whose apex the ophthalmic nerve arises. This 
ophthalmic ganglion later fuses completely with the Gasserian ganglion. It 
probably represents the cellular cord which I have described in the rat embryo, 
which, however, disappears as the fibrous ophthalmic nerve is formed. 
It is, indeed, unfortunate that Minot in his description not only considers that 
the ganglion described by Professor His represents the ciliary ganglion of the 
adult, but also states that it gives origin to the fibres of the ophthalmic nerve. 
On page 641 of his “‘ Human Embryology,” referring to the fifth cranial nerve, 
he remarks :—‘‘ Its ganglionic portion is double, comprising the ciliary or ophthal- 
mic ganglion and the Gasserian.” Then, on page 642, under ‘ ganglion ciliare,” 
we find :—‘ This is the ganglion which has been long and generally known as the 
ciliary, and becomes the ciliary of the adult . . . The centrifugal nerve, arising 
from the ganglion, is known as the ramus ophthalmicus profundus, the centripetal 
nerve as the radix longa, which joins the trigeminal ganglion before the radix 
enters the brain . . . Why the fibres pass to the brain by way of the trigeminal, 
instead of making an independent entrance, is unknown.” 
Professor His has stated, as we have seen above, that the ganglion which he 
described as ciliary in man did not give rise to fibres of the ophthalmic nerve, and 
further, the proved structure of the ciliary ganglion in the adult shows that it is 
not the homologue of a spinal ganglion. ‘This will be mentioned more fully at 
a later stage. 
* Monitore Zool. Ital. v., 1894, pp. 275-280. 
