DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 135 
under the basis cranii and protecting the narrow nasopalatine canal (i.p.c.); these 
are the pterygoids (pg.c.) in their unossitied free part (“hamular process”). Outside, 
and below, we see a part of the squamosal, its zyomatie region on the jugal (j.) ; and 
inside it the glenoid facet (g/.c.) is cut along its whole transverse extent. A little 
below it a section of cartilage appears, thick above and below and narrower in the 
middle; this is the main part of the great superficial slab, a segment of which is 
given off to form the glenoidal facet. The upper part is the condyle of the lower 
jaw (cd.p.), the lower is part of the angle (wg.p.); the inside of the cartilage is 
becoming bony ; in the concavity, on the lower part of the inner side, MEcKEL’s 
cartilage (mk.) is still full-sized. 
15th Section (Plate 18, fig. 15)—-Here the fore brain (C'.) is cut through near the 
infundibulum, but the pituitary body (py.) is seen as a large separate quasi-glandular 
mass resting upon the basis cranii near the beginning of the parachordals or investing 
mass ().s.). These are flattish and ovoidal in section, the interspace between them 
being the primary pituitary space at its hinder part. On the side, the orbitosphenoid 
(o.s.) is still seen as a considerable band of cartilage; this is near the junction of the 
frontal (f) and parietal bones. The Gasserian ganglion (V.) is cut across in its 
hinder part, and the razor has caught the cochlea (above 7.c.) in its fore margin. This 
is behind the hinge of the secondary mandible, and through the part of MrecKkenr’s 
cartilage where the bony lamina that forms the ossifying centre of the malleus (m/.) 
has appeared. Outside this the postglenoid part of the squamosal (sq.) is seen, and, 
between the two, the foremost part of the tympanic cavity (c.ty.). The internal 
carotid artery (i.c.) is seen entering the skull between the cochlea and the basi- 
sphenoid (b.s.), and under it the Eustachian tube (ew.) is laid open as it is passing 
towards the fauces or back part of the oval cavity (phw.); it opens into that cavity 
between this and the last section (fig. 14). 
Under this tube the cartilaginous lining of the first cleft is seen to extend (ew.c.) ; 
this Eustachian cartilage is the innermost part of the partly segmented cartilaginous 
tube which expands externally as the “ concha,” and which, in the part next outside 
the Eustachian cartilage, becomes ossified, early, as the annulus tympanicus. 
Four arterial branches are seen, here, cut obliquely across, one of them close beneath 
and outside an oval section of cartilage, the ceratohyal (c.hy.). The one above it is 
that part of the “common carotid” which gives off the “ stapedial artery,” to inosculate 
with the artery of the lower jaw. 
At the mid-line, below the palatouasal cavity, the pharynx is laid open, and right 
and below it the hypohyal cartilages (h.hy.). Outside and in front of the cerato- 
hyal the chorda tympant (VII“) is cut across, and outside and below these the main 
facial nerve (VIT.). 
16th Section (Plate 18, fig. 16).—This is through the widest part of the hemispheres 
(C'”.), and also cuts across the large glandiform pituitary body (py.). Several large 
uervous masses are cut through (VIL, VII.), close to the top of each cochlea (chl.). The 
