588 ALICE JOHNSON AND LILIAN SHELDON. 
Fic. 16.—Transverse section through the head end of an embryo at a stage 
shortly after the closure of the medullary canal, to show the neural ridge in 
the brain. Owing to the cranial flexure, all three divisions of the brain are 
cut through. 
Fic. 17.—Transverse section through an embryo slightly older than that 
from which Fig. 16 was taken, showing the origin of the 3rd nerve as a paired 
outgrowth from the neural ridge in the mid-brain. 
Fic. 18.—Transverse section through the same embryo as that from which 
Fig. 17 was taken, showing the origin of the 5th nerve from the neural ridge 
in the hind-brain. The lateral thickening of epiblast on each side is shown. 
Fic. 19.—Transverse section through the hind-brain, to show the origin of 
the 7th nerve as a paired lateral outgrowth of the neural ridge. The lateral 
thickening of epiblast, which will give rise to the ear and sense-organ of the 
7th nerve, is shown on each side. 
Fic. 20.—Transverse section through a somewhat older embryo, showing 
that the root of the 3rd nerve has shifted to the sides of the mid-brain. 
Fig. 21.—Transverse section, showing the attachment of the Gasserian 
ganglion to the epiblastic thickening forming the sense-organ corresponding 
to the 5th nerve. 
Fic. 22.—Slightly oblique transverse section, to show the shifting of the 
root of the 5th nerve; its attachment is seen to extend continuously from 
the summit of the brain to a point some way down its side. 
Fic. 23.—Transverse section through an older embryo, to show the shifting 
of the root of the 5th nerve. ‘The nerve is now connected only with a small 
area of the side-wall of the brain. 
Fic. 24.—Transverse section through a still older embryo, showing on the 
right side the superior maxillary and dorsal branches of the 5th nerve grow- 
ing out from the Gasserian ganglion. On the left the Gasserian ganglion and 
inferior maxillary are shown. 
Fic. 25.—Transverse section through a young embryo, showing on the left 
the root of the facio-auditory nerve and its fusion with the epiblast ; on the 
right the auditory epithelium and ventral continuation of the nerve. 
Fic. 26.—Transverse section through the same embryo as that from which 
Fig. 24 was taken, but slightly posterior to it. It shows on the right the 
Gasserian ganglion and inferior maxillary branch of the 5th nerve; on the 
left the root, ganglion, and pre-branchial branch of the 7th nerve. 
Fic. 27.—Transverse section through a young embryo, showing the root of 
the 9th nerve and its fusion with the lateral thickening of epiblast correspond- 
ing to it. On the right the nerve is seen passing on to the 2nd visceral cleft. 
Fic. 28.—Transverse section through a somewhat older embryo, It shows 
on the right the root, ganglion, and main branch of the 9th nerve, the last 
fusing with the epiblast of the dorsal wall of the 2nd visceral cleft. On the 
left only the main branch and its fusion are seen. 
