DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
173 
section, and besides the hyoid rods (e.hy., h.hy.), the thyroid cartilage, as well 
as the arytnoids (lx.) are cut across. 
17th Section (Plate 24, fig. 7). —This section is through the basisphenoicl ( b.s .), close 
behind the edge of the alisphenoid (al.s.), which, however, is caught further outwards, 
still bearing the Gasserian ganglion (V.). The hinder edge of the soft palate is cut 
through, and the nasopalatine canal ( n.p.c .) is nearly continuous here with the mouth 
(m.). Besides the hyoid and cartilages (e.hy., h.hy.), and the larynx (lx.), the upper 
tracheal rings are seen in section. The tympanic cavity (c.ty.) is laid open, and 
also the inner part of the Eustachian tube (eu.) ; here the meatus cartilage (m.c.) 
is thick. Meckel’s cartilage is now thick : it is the fore part of the head of the 
malleus (ml.) that is seen at this point; above it a small tract of the tegmen tympani 
( t.ty.) is also brought into view; outside these cartilages the squamosal is shown. 
l%th Section (Plate 24, fig. 8).—This section is behind the alisphenoid and through 
the ganglion geniculatum (VII., VIII.); also, besides a small piece of the tegmen 
tympani, the fore part of the cochlea (chi.) is cut across. In this and the last section 
the basisphenoicl (b.o.)* is concave below, this is because the mammillary processes that 
form the foundation of the “tympanic wings” are cut through (Plate 25, fig. 2, b.s.). 
In the hollow we see the large faucial passage (phx.), which opens into the larynx (lx.). 
The laryngeal and tracheal cartilages are similar to those of the last section, and so 
are the hyoid (e.hy., h.hy.) ; beneath the epihyal, the chorda tympanic nerve (VII 3 .) 
is seen in section. Inside the squamosal, and under the tegmen tympani, the whole 
head of the malleus, with its manubrium, is shown; the latter pushing the membrana 
tympani before it ; this is behind the Eustachian tube. 
19 tli Section (Plate 24, fig. 9).—This section of the cranial basin is oblique and may 
serve as two ; the right side is from a point in front of the left; and from the some¬ 
what sinuous direction taken by the razor, some things on the left side belong to 
points in front of the parts shown in the last (fig. 8). 
The orbitosphenoidal band and part of the parietal (o.s ., p.) are cut across, above ; 
whilst the squamosal (sq.) and the meatus (m.a.c.) are seen lower down. Here, again, 
the head of the malleus (ml.) is seen in its whole extent, capped by the tegmen 
tympani, and with its manubrium pushing inwards the membrana tympani. 
Over the malleus, the ganglion geniculatum (VII., VIII.) is seen, and under the 
tympanic cavity (c.ty.) the ceratohyal (e.hy.). On that side the cochlea (chi.) is just 
laid open, on the other it is cut across its middle. Between the two, the basisphe- 
noid (b.o.) f has becomes thicker and narrower, and it is still concave below; 
it carries, here, the pituitary body (py.). The obliquity of the section is shown by 
the form of the upper part of the fauces (phx.) below the basis cranii. 
The left side is very instructive, for it shows the other elements of the ear- 
chain behind the malleus. This is the front view of the section, and thin as it is, the 
* Tlie letters of reference in this ancl tlie next figure sliould be b.s. 
t Tlie letters of reference sliould have been b.s. 
