DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
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head—3^- lines long—I have only figured twelve, but some of these are drawn as 
separate half sections; they were somewhat oblique. 
Section 1 (Plate 23, fig. 1).-—This is close to the hind part of the alinasal region ( al.n.), 
at the beginning of the aliseptal. The nasopalatine canal is open below, and here, 
behind the narial valves, the cavity is high and simple. The septum nasi and alinasal 
folds (s.n ., al.n.) are well developed; the thickness of the former, below, is due to 
the size of the intertrabecula, and the cartilaginous walls are thickening above to 
form the nasal turbinal, and below to form the inferior turbinal. 
In the thick mass of tissue below the septum the recurrent cartilages ( rc.c.) are 
seen, they are placed subvertically, and are thick above and thin below ; outside them 
Jacobson’s organs (j.o.) are shown, and inside them the palatine processes of the 
premaxillary (p.px.). 
The hind part of each premaxillary ( px .) is cut through laterally, there are two 
laminae of bone meeting, above, at an acute angle; below, in the mucous membrane, 
a tooth-pulp (p.) is shown ; the nasals (n.) are forming, above. 
Sections 2 and 3 (Plate 23, figs. 2 and 3).—These, which were one oblique section, 
show, on the deepest side (fig. 3), the remarkable manner in which the rudimentary 
nasal turbinal ( n.tb .) encloses an oval space ; below that space the cartilage grows 
inwards, and is pedate ; this is the inferior turbinal. Here, inside Jacobson’s organs 
(j.o.), the recurrent cartilages (rc.c.) are thick throughout, and the little vomerine 
bones are not apparent. The maxillary (mx.) comes into the section here, and the 
nasals (n.) are seen, above. In this, as in the last, mucous crypts are seen here and 
there between the lining of the nose and the cartilage ; the whiskers are cut through 
in the outer skin, and a tooth-pulp is shown below. 
Sections 4 and 5 (Plate 23, figs. 4 and 5).—These, which were one oblique section, 
were made through the middle of the eye-ball (e.) on one side, and on both through 
the olfactory lobes (C 14 .). It also takes in the lower face, with the tongue (tg.). The 
mass of soft tissue under the olfactory lobes will be differentiated into the cribriform 
plate, the olfactory nerves passing through its meshes. This is behind the roof of 
the nasal labyrinth, and thus the septum, here, the perpendicular ethmoid (p.e.), has 
a free upper edge— the region of the crista galli. 
In the side which is the foremost part (fig. 4), the nasal wall passes a little over, 
above, and under, below, and sends inwards a large plate of cartilage, which is 
bifurcated and very thick at its inner part. Here we have the rudimentary middle 
turbinals ( m.tb .). The same is seen on the other, or hinder, side, but above ; the 
section is near the orbitosphenoid, or fore part of the cartilaginous cranium, for it is 
continuous with the nasal labyrinth (ale.) ; the frontal bone (/'.) is seen outside it. 
Also, below the bulbous base of the middle ethmoid, formed here of all the three 
trabeculae, the hinder forks of the vomer (v.) are to be seen ; whilst below, on the 
palatine ridge, the palatine plate of the palatines (pa.) is cut across. Below, outside 
the base of the tongue (tg.), the dentary (d.) and Meckel’s cartilage (ml.) come into 
view. 
MDCCCLX XXV. 
Y 
