76 Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
Figure 
17. Drawing of a reconstruction to show some of the branches of the inferior maxillary nerve in em- 
bryo CR. This drawing corresponds to a horizontal section, 0-4 mm. in thickness, x 25 diamaters, 
seen from above. The auriculo-temporal nerve is seen passing downwards on the outer side of 
Meckel’s cartilage. The mylo-hyoid also passes downwards on the outer side of the cartilage, 
but it then turns forwards and inwards beneath the cartilage. The lingual nerve lies along the 
inner and upper border of the cartilage, and enters finally the submaxillary ganglion, which lies 
in front of Wharton’s duct. A small part of the chorda tympani branch of the facial is seen 
just before it joins the lingual. The chorda tympani ascends close to the mner side of Meckel’s 
cartilage. A portion of the facial nerve itself is seen passing downwards and forwards, and 
portions of the ganglia of the eighth nerve are seen in relation to the internal ear. The nerve 
of Jacobson is not indicated ; it would lie between the internal ear and the wall of the pharynx. 
The section represented by this drawing lies in the head, just below that represented by fig. 16. 
18. Drawing of a reconstruction to illustrate the origin of the chorda tympani branch of facial, and also 
that of the nerve of Jacobson in embryo CR. This drawing corresponds to a horizontal section, 
0-3 mm. in thickness, x 25 diameters, seen from above. The chorda tympani is seen coming off 
the facial at an acute angle, and passing upwards to the outer side of the Eustachian tube. 
The nerve of Jacobson takes origin from the petrous ganglion of the glosso-pharyngeal, and 
passes upwards almost vertically. The section represented by this drawing lies in the head, a 
little distance below that represented by fig. 17. 
19-20. Outlines of parts of two vertical antero-posterior sections of embryo F.M., x 25 diameters, to show 
the relationship between Meckel’s cartilage, the developing mandible, the lingual nerve, the 
inferior dental nerve, and the mylo-hyoid nerve. In the section represented by fig. 19, which is 
the further from the middle line, the inferior dental nerve is placed between Meckel’s cartilage 
and the developing mandible, the mylo-hyoid nerve lies below Meckel’s cartilage, and the lingual 
nerve is above its upper border. In fig. 20, which represents a section in the region of the 
mental foramen of the adult, we see the developing mandible composed of two parts separated 
by an interval, which gives passage to the mental branch of inferior dental. In fig. 20 the 
lingual nerve lies a considerable distance above and behind Meckel’s cartilage, and the mylo- 
hyoid nerve some distance below. 
