20 
MR. W. K. PARKER OK THE STRUCTURE AND 
cincture. On the outside the quadrate cartilage (q.) sends a process inwards which 
is tied by a ligament to the corresponding trabecular horn ( c.tr .), and thus the circle 
is completed. From this part the cornua turn downwards in a gentle manner, as they 
diverge, and end in a broad, sub-emarginate flap. 
The sclerotics and nasal roofs, which were beginning to cliondrify, having been 
removed, we have only the auditory sacs to describe in this stage. 
They are now thoroughly cartilaginous, and quite confluent with the cranial walls, 
roof, and floor. Moreover, they are swollen with the growth within of the three wide 
canals, and the sacculated base of the membranous labyrinth (a.s.c., h.s.c., p.s.c., vb.). 
A crescentic flap of cartilage grows outwards from the horizontal canal; this is the 
“ tegmen tympani,” under that roof we see the large fenestra ovalis, and the well- 
fitting oval stapes (vb., st.). The fore angle of the tegmen has a flap of cartilage 
growing from it, the result of coalescence ; this, the rudimentary “annulus,” will be 
described soon. 
Leaving out some of the smaller passages, we may refer to the double passage for 
the 9th and 10th nerves (fig. 6, IX., X.), the single passage for the 7th and 5th 
(VII., V.) and the fenestra for the 2nd nerve (II.) : the 8th and 1st are out of sight 
in this view. 
Each of the huge “ mandibular piers ” is two-thirds the length and two-thirds the 
breadth of the cranium proper. Besides the two earliest conjugations with the basal 
cartilage, each bar articulates by its “otic process” with the cartilage that projects 
from the tegmen tympani, and is tied, as above stated, near its distal end to the 
cornu trabeculae. 
It is thus swung at four points from the basis-cranii, but of these, the “pedicle” is 
the true apex or dorsal end (fig. 6, pel.), it lies beneath the parting of the facial and 
trigeminal nerves (VII., V.), and runs parallel for some distance with the front face of 
the auditory capsule. 
Between the pedicle and the palato-pterygoid bar there lies a large subocular fenestra 
(s.o.f.), or membranous space, parallel with the skull ; and behind the pedicle a smaller 
oblique space is formed, bounded behind by the ear-sac. 
The large “ suspensorium ” is thick at its outer edge, and thin at its inner, which 
rises somewhat from its smooth, sinuous, upper face; on this the long temporal muscle 
rests, as it passes from its origin in the post-orbital region, to its insertion on the 
“ coronoid ” crest of Meckel’s cartilage (mk.). 
The suspensorium is terminated by a reniform condyle for the mandible (q., mk.), 
and opposite the ethmoid it has on its under surface, at the outer edge, a pyriform 
flatfish facet for the hyoid plate (hy.f.). 
Over this secondary condyle, which projects outwards, the suspensorium is developed 
into a large rounded leaf, with a broad adherent base, a ribbed edge, and a hollow 
upper surface—this is the “ orbitar process” (or.p.), which bends over the temporal 
muscle and is tied by its apex to the skull wall in front. 
