Drxon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 78 
Figure 
Us 
8. 
EXPLANATION OF THE FIGURES ON PLATES I. ann II. 
Outline of embryo Br. (4 years old), x about 3 diameters. The outline is reduced from a drawing 
of Professor His’s. The longest diameter of this embryo is 6:9 mm. 
Outline of embryo Ru. (5th week), x about 3 diameters, reduced from a drawing by Professor His. 
The length of this embryo from the cervical to the caudal bend is 9°1 mm. 
Outline of embryo C.R. (beginning of 6th week), x about 3 diameters, reduced from a drawing by 
Professor His. This embryo measures 13:6 mm. from the cervical to the caudal bend. 
Outline of embryo F.M. (seven weeks), x 3 about diameters, reduced from a drawing by Pro- 
fessor His. This embryo measures from the cervical to the caudal bend 17°5 mm. 
. Are drawings of reconstructions from sections through the heads of these embryos. Each drawing 
may be taken to represent a magnified view of a very thick section. 
Drawing of a reconstruction, to show the course and position of the ophthalmic nerve in embryo 
Br;. This drawing corresponds to a section cut horizontally through the head, 0°32 mm. in 
thickness, and x 25 diameters, seen from below. The ophthalmic nerve is shown cut across 
at the point where it leaves the Gasserian ganglion. The course of the nerve is upwards and 
slightly inwards. The relationship of the third and ophthalmic nerves is also shown. 
Drawing of a reconstruction to illustrate the course of the ophthalmic nerve in embryo Ru, ‘This 
drawing corresponds to a portion of a horizontal section through the head, 0:4 mm. in thickness, 
x 25 diameters, seen from above. Deep down in the reconstruction the top of the Gasserian 
ganglion is seen ; and the ophthalmic nerve ascending from it is observed to divide into frontal 
and nasal branches. The frontal branch is short and ascends nearly vertically, while the nasal 
branch, which is much longer, passes forwards over the optic stalk, towards the upper part of 
the nasal fossa. The terminal parts of the third and fourth nerves, are also seen, passing down- 
wards and forwards. 
Drawing of a reconstruction to illustrate the origin of the ophthalmic nerve in embryo C.R. The 
drawing corresponds to part of a horizontal section through the head, 0-2 mm. in thickness, 
x 25 diameters, seen from above. The nasal and frontal nerves are seen cut across, the former just 
at the point where it crosses the optic stalk. The lachrymal nerve is shown passing outwards 
behind the eyeball. The relationship of the terminal portion of the third nerve, to the Gasserian 
ganglion and optic stalk, is indicated. The extreme summit of the Gasserian ganglion has been 
cut off at the upper surface of this thick section. In the anterior part of the drawing the nasal 
fossa is seen opening on to the face. 
Drawing of a reconstruction to illustrate the terminal branches of the ophthalmic nerve in embryo 
C.R. This drawing corresponds to a portion of a horizontal section through the head, 0-7 mm. 
in thickness, x 25 diameters, seen from above. The frontal nerve is seen turning outwards over 
the eyeball, and dividing into supraorbital and supratrochlear branches. The nasal nerve on the 
other hand passes forwards and inwards towards the roof of the nasal fossa. The nasal gives off 
an infratrochlear branch. In connection with the undivided frontal is an oval mass of cells 
which probably represents the ciliary ganglion of the adult. The fourth nerve is seen to 
communicate with the frontal, and then to end in this oval mass. A small portion of the third 
nerve is seen in the upper part of the figure. The thick section represented by this drawing lies 
in the head immediately above the one represented by fig 7. 
