" 
678 THE ORGANS OF SENSE. | 
The nasal fossa above and behind the vestibule is divided into two parts, viz. 
an upper or olfactory, and a lower or respiratory region. The olfactory part, or regio 
olfactoria, is a narrow slit-like cavity, and comprises the region of the superior 
turbinated bone, together with a correspond- 
A eae ed ing portion of the septum. The respiratory 
oe “\jateral part, or regio respiratoria, is expanded, and 
Jeartileze includes the lower and remaining parts of 
— Crus mediale 
nares 
fe Lower edge of the fossa. 
f Seer a Inner Wall or Septum Nasi (Fig. 484). 
( 3 —Where the bony septum is deficient, 
ty 7 Fatty tissueof below and in front, the gap is filled by the 
ala nasi 
septal cartilage. Until the seventh year 
the nasal septum hes, as a rule, in the 
mesial plane, but after this age is very 
often deflected to one or other side—more 
frequently to the right—the deflection 
taking place along the line of junction of the vomer and mesethmoid. In the 
floor of the fossa, close to the lower edge of the septal cartilage and immediately 
over the incisive foramen, a slight depression, the recessus nasopalatinus, may be 
seen. It is directed downwards and forwards, and indicates the position of the 
communication na 
which originally 
existed between 
the nasal and 
buccal cavities. 
In the septum, 
a little above 
EDC eT OM bee SUPCOE 
5 : turbinated 
of this depres- bone 
sion, 1s a minute 
Fic. 487.—CarTILAGES OF NOSE FROM BELOW. 
Posterior 
ethmoidal 
cells 
Superior 
meatus 
Middle 
orifice, not always turbinated \\__ Middle 
O bone \\ meatus 
recognisable, \ 
f S Nasal_|! 
rom swhrehs as | seminal Antrum of 
blind pouch ex- Highmore 
Inferior 
tends upwards turbinated 
and backwards boner as 
for a distance of ; 
from 2 to 9 mm. 
This is the rudi- 
mentary organ of 
Jacobson (orga- 
non vomero- 
nasale) and is 
supported by the 
vomerine  carti- 
lage. In many of 
the lower animals this organ is well developed (Fig. 489), and in them probably 
plays a part in the sense of smell, as to it a branch of the olfactory nerve is 
distributed. 
Outer Wall (Fig. 490).— Above the superior turbinated bone is a narrow recess, the 
recessus spheno-ethmoidalis, into the posterior part of which the sphenoidal air-sinus 
opens. ‘The superior meatus (meatus nasi superior) isa short oblique fissure, directed 
downwards and backwards, under cover of the superior turbinated bone; into its 
antero-superior portion the posterior ethmoidal cells open by one or more orifices. 
The middle meatus (meatus nasi medius), situated externally to the middle turbinated 
bone, is a roomy passage, and is continued forwards into a slightly depressed area 
termed the atrium meatus nasi, which lies immediately above the vestibule. The 
atrium is limited above and in front by a low ridge, the agger nasi, the repre- 
sentative of the naso-turbinal found in many animals. On raising or removing the 
Inferior 
meatus 
Fic. 488.—CoroNAL SECTION THROUGH NASAL Fossm ; ANTERIOR HALF OF SECTION 
VIEWED FROM BEHIND. 
: 
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