478 PROF. MILNES MARSHALL AND W. B. SPENCER. 
(V.c’., fig. 10) between the fifth and seventh nerves: this is 
present at x, at which stage as well as at L, it forms a very 
stout, though short nerve, running forward and downwards from 
the seventh nerve, over the top of the third head cavity, to join 
the lower part of the Gasserian ganglion. 
The branches of the fifth nerve at stage N are well seen in 
figs. 11 and 12 which have been constructed so that each of 
them may show the whole course and distribution of certain nerves ; 
the outlines of the figures were drawn, with the camera, from 
individual sections and the branches of the several nerves care- 
fully filled in, again by the aid of the camera, from other sections 
of the same series. In this way sucha view of the nerve 
is obtained as might be got from a transparent embryo in which 
the nerves alone stood out as opaque objects. To prevent con- 
fusion, from the overlapping of different nerves, two figures 
have been given of which the first (fig. 11) shows the roots of 
the fifth and seventh, the connections of these with one another 
and with the third nerve, the branches of the latter and of the 
fifth, the fourth nerve, and some of the branches of the seventh ; 
in the second (fig. 12) the remaining branches of the seventh, 
with certain of the glossopharyngeal, are shown, and in addition 
to these, the whole course of the ophthalmics. 
The branches of the fifth nerve are seen to be the following : 
1. The ophthalmic branch, (v a) which arises by a slightly 
ganglionic root, runs forward over the odliquus superior (o. 8.), 
crossing, as it does so, the fourth nerve at right angles and 
giving off branches, some of which appear to be connected with 
the fourth. 
2. The communicating branch (V.c.) between the Gasserian and 
ciliary ganglia, the position and relations of which nerve are 
sufficiently well shown in the figure. We reserve the discussion 
of this branch, merely noticing here that, though we describe it 
with the fifth nerve, it appears to belong to the third quite as 
much as to the latter. 
3. The main stem of the fifth, ranning down behind the first 
head cavity (1) and the rectus externus, receiving the communi- 
cating branch (J.c.’) from the seventh, and after passing down- 
wards and forwards for some distance, dividing into two 
branches, (a) an anterior or maxillary nerve (v4) which again 
gives off numerous branches to the skin of the upper jaw, and 
(6) a posterior or mandibular (v ce) which runs backwards and 
downwards, lying in close contact with the outer wall of the 
lower part of the mandibular head cavity (2), and supplying it 
with branches. The distribution of ganglion cells is sufficiently 
shown in the figure ; there is a small ganglion at the base of the 
ophthalmic nerve, and the ganglion cells of the main stem 
