CORONAL SECTIONS OF THE CRANIUM. 
perforated or oblique. 
171 
The sinuses are hardly ever symmetrical, the right being 
usually the smaller of the two (Logan Turner, Hdin. Med. Jowrn. 1898). 
The infundibulum on either side, leading from the frontal sinus above to the middle 
meatus below, is seen with the 
middle turbinated bone internal 
to it, and the anterior ethmoidal 
cells to its outer side above. If 
the section passes through the 
canal for the nasal duct the con- 
tinuity of that channel leading 
from the orbit above to the 
inferior meatus of the nose below 
is clearly shown. Its inner wall 
above, by which it is separated 
from the cavity of the nose, is 
formed by the thin lachrymal 
bone; below, it passes under 
cover of the inferior turbinated 
bone to open into the fore part 
of the inferior meatus. It is 
separated from the antrum ex- 
ternally by a thin lamina of bone. 
The cavity of the antrum is seen 
to extend upwards and forwards 
so as to pass over the outer side 
as well as slightly in front of the 
canal for the nasal duct. 
The lower margins of the 
middle turbinated bones lie pretty 
nearly on a level with the most 
dependent parts of the orbital 
margins, whilst the lower borders 
of the inferior turbinals are 
placed a little above the lower 
margin of the anterior nares on 
a level with the lowest point of 
the malo-maxillary suture. 
Such a section will reveal any 
deflection of the nasal septum 
should it exist, and will also show 
that but a narrow cleft separates 
the upper part of the septum, on 
either side, from the inner surface 
of the superior turbinals. 
The next section (Fig. 121) 
passes through the fore part of 
the temporal fossa just behind 
the external angular process of 
the frontal bone above ; inferiorly 
it passes through the alveolar 
process of the upper jaw in the 
interval between the first and 
second molar teeth. The cranial, 
orbital, nasal, and maxillary 
cavities are all exposed, together 
with the roof of the mouth. 
The anterior cranial fossa is 
deepest in its centre, where its 
floor is formed by the cribriform 
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Fic. 121.—CoronaAL SECTION PASSING INFERIORLY THROUGH 
INTERVAL BETWEEN FIRST AND SECOND Moar TEETH. 
Groove for superior longi- 
tudinal sinus. 
Crest for attachment of falx 
cerebri. 
Crista galli of ethmoid. 
Cribriform plate of ethmoid. 
Perpendicular plate of eth- 
moid, assisting in the forma- 
tion of nasal septum. 
Lateral mass of ethmoid con- 
sisting of the ethmoidal cells. 
Os planum of ethmoid. 
Middle meatus of nose. 
Middle turbinated bone. 
Opening from middle meatus 
into antrun. 
Orbital plate of 
maxilla, 
superior 
Fronto-malar suture. 
. Infraorbital groove. 
Antrum or maxillary sinus. 
Canal for the anterior dental 
nerve and vessels exposed. 
Inferior turbinated bone. 
. Inferior meatus of nose. 
. Alveolar process of superior 
maxilla. 
. Groove for anterior palatine 
nerve and vessels. 
. Palatal process of superior 
maxilla, 
. Maxillary crest forming part 
of nasal septum. 
Vomer forming part of nasal 
septum, 
plate of the ethmoid; this corresponds to the level of the fronto-malar suture 
externally. 
the roof of the orbit. 
On either side the floor of the fossa bulges upwards, owing to the arching of 
Of the orbital walls, the external is the thickest and stoutest ; 
the superior, internal, and inferior walls, which separate the orbit from the cranial cavity, the 
