Dixon— On the Development of the Branches of the Fifth Cranial Nerve in Man. 51 
outwards. The termination of each is about 0:2 mm. from the inner side of the 
superior maxillary nerve near its origin, and just below the level of the eyeball. 
The great superficial petrosal branch of the geniculate ganglion of the facial 
nerve ends about 0'4 mm. below the point of origin of the superior maxillary 
nerve. This branch of the geniculate ganglion, at this stage, does not communi- 
cate with the superior maxillary nerve. There is no Meckel’s ganglion present, 
unless the nuclei present among the fibres of the nerve near its origin, represent 
the cells of a ganglion. These nuclei do not seem to be as numerous in this 
embryo as they are in Br,., the representative of an earlier stage. 
Empryo C.R.—(beginning of 6th week, 13°6 mm.). Figure 13, Plate IT. 
The superior maxillary nerve rises from the anterior surface of the Gasserian 
ganglion, a little nearer to its lower than to its upper end. The fibres of the 
nerve are, at first, tightly pressed together, as if constricted by a band drawn 
round them, but they soon spread out, especially in a horizontal direction. The 
inner fibres spread out most, some passing directly inwards, some inwards and 
forwards. Three or four fine branches communicate with Meckel’s ganglion, 
which lies below, and to the inner side of the superior maxillary nerve. 
Most of the fine nerves which run inwards from the superior maxillary are 
directed towards the roof of the primitive mouth cavity, behind the point where 
the choanze communicate with it. These nerves, when viewed from above or 
below, form a loose layer of fine bundles, separated from each other by short 
intervals, apparently sometimes communicating with one another, and sometimes 
passing back into the main nerve trunk. The length of these inwardly directed 
nerves varies from 0°6 to 1:0 mm. The superior maxillary nerve passes forwards, 
until it is only about 0°5 mm. from the surface, here it divides into branches, the 
largest of which turn inwards towards the middle line. The course of the nerve 
lies some distance below, and to the inner side of the eyeball. Near its 
termination, and just before it divides into these terminal branches, the superior 
maxillary nerve turns a little upwards. The length of the nerve from its origin 
to the point of division is 1-4 mm. ‘The terminal branches of the superior 
maxillary nerve turning inwards, give off many fine twigs, those of the lower 
branches, turning downwards, for the most part, and those of the upper ones, 
upwards. The twigs which pass upwards are the longest, and supply the surface 
of the face as high as the level of the equator of the eyeball. The lower 
branches of the superior maxillary nerve, below the level of the opening of the 
nose on the face, reach to within about 0°5 mm. of the middle line. Malar and 
temporal nerves come off the outer side of the main superior maxillary trunk. 
Both of these are very slender nerves, and the temporal passing outwards, and a 
TRANS, ROY, DUB, SOC., N.S. VOL. VI., PART II, I 
