170 
MR. W. K. PARKER OK THE STRUCTURE AND 
last section, is a retral tract of cartilage, convex on the inner face, where it touches the 
septum, and concave externally; this is the “recurrent cartilage” ( rc.c .) developed 
for the support of Jacobson’s organ. Here the upper lips are seen, and have a hollow 
palatine part between them ; below, the Meckelian rods (ink.), are distinct in the mass 
of the lower jaw, over which the tip of the tongue is seen. The pulps of the whiskers 
(vibrissce ) are cut through in the outer thick skin. 
6tli Section (Plate 23, fig. 21).—PXere the septum nasi is deeper, and the bulbous 
part less; the aliseptal folds ( al.sp .) turn inwards below; the inturned part is the 
rudiment of the inferior turbinal. The recurrent cartilage (rc.c.) was tubular between 
this and the last section; but it is now open again to the end; here it has Jacobson’s 
organ (j.o.) in its concavity. The pulp of an incisor is seen, and Meckel’s cartilages 
are getting some distance apart. 
7th Section (Plate 23, fig. 22). —This is a remarkable section, and very instructive. 
It is behind Jacobson’s organs and cartilages, and is seen to be girdled with bony 
tracts—the nasals (n.) and maxillaries (mx.), with them palatine plates; the base of 
the deep septum (s.n.) also is supported by the main vomer (v.). The septum becomes 
thin above, as it passes into the broad and solid nasal roof (al.sp.), which is convex 
right and left and in the middle. The wall as it becomes floor turns inwards to form 
the pedate rudiment of the inferior turbinal, which projects upwards so as to lessen 
the nasal passage below. Below each shallow valley on the roof, a large lamina of 
cartilage grows downwards and a little outwards, dividing the nasal passage into a 
larger inner, and a lesser outer, space, both sub vertical and somewhat pinched in at 
the middle. 
This is the “ nasal turbinal ” ( n.tb .), which for a short distance, fore and aft, and for 
a short time during development, forms a complete secondary nasal septum on each 
side of the septum proper (s.n.). 
8th Section (Plate 23, fig. 23). —This is immediately in front of the olfactory fossae, 
and through the fore part of the eye-balls (e .); this is the widest paid of the complete 
nasal labyrinth. The septum is now perpendicular ethmoid (p.e.), and the roof is in 
the aliethmoidal region. The maxillary (mx.) is cut through close in front of the 
orbit, and again in the palatal region, right and left of which there is a tooth-pulp (t.). 
The vomer (v.) is cut through its middle, and over it the deep septum (p.e.) thickens 
twice ; it also grows so as to lift the roof over it into a low rounded ridge. Inside, 
near the septum, and at the upper part of the wall, there are small rudiments of the 
upper turbinal folds (u.tb.), and half way down the wall grows inwards as a large mass 
of cartilage, pedate in section ; this is the common rudiment of the middle turbinal 
folds ( m.tb.). The floor is cut through behind the inferior (properly anterior) turbinal, 
it ends far from the mid-line. Below, the dentary (d.) is cut through ; over it, outside, 
is a tooth-pulp, and further inwards Meckel’s cartilage (mk.) ; the tongue (tg.) is now 
developing its -freeman. The palatine plate of the palatine begins to be seen in section. 
9th Section (Plate 23, fig. 24). —The olfactory lobes (CP) are cut through the 
