ANATOMY-OF THE HORSE. 
349 
Each lateral wall or side presents an irregular concavity, 
and is formed by the anterior and superior maxillary and the palate 
bones. To it are attached the superior and inferior turbinated 
bones, by which the fossa is divided into three separate passages 
or meatus. The superior meatusy comprised between the nasal and 
superior turbinated bones, extends from the angle of the lateral 
nasal opening passing over the ethmoidal cells, to the cribriform 
plate, following superiorly the declination of the wall. The mid¬ 
dle meatusy included between the turbinated bones, leads superi¬ 
orly into the ethmoidal grooves and cells, and into the sinuses of 
the head, and ends below beneath the termination of the superior. 
This passage, like the fomier one, is narrow; but its greatest 
diameter is, obliquely, in the perpendicular direction; whereas 
the other measures most from side to side. It receives the aper¬ 
tures of the ductus ad nasum, maxillary sinus, ethmoidal grooves, 
and turbinated cells. The inferior meatus is the most capacious 
as well as most direct one: it extends along the inferior wall, from 
the anterior to the posterior opening of the nose. 
The septum nasi is the partition separating one fossa from 
the other. It is toraied, posteriorly, by the ethmoidal plate; in- 
feriorly and posteriorly, by the vomer; superiorly and anteriorly, 
(and principally) by a broad pei’pendicular plate of cartilage. 
The openings of the nose are,— The anterior, divided 
by the nasal peak and septum nasi into two, and formed by the 
•superior borders of the anterior maxillaiy bones : the posterior, di¬ 
vided after the same manner by the vomer and septum, and formed 
by the nasal surfaces and crescentic borders of the palate bones. 
THE SINUSES OF THE HEAD communicate with, and 
may be said to constitute, part of th^ nasal cavities. They are 
the frontal, nasal, maxillary, sphenoidal, ethmoidal, and palatine. 
The frontal sinuses, formed within the frontal bones, are 
so situated, that a straight line extended between the supero- 
intemal angles of the orbits passes opposite to about the angular 
or deepest parts of their-cavities. The sinus, on either side, has 
a triangular figure. The superior side or roof is flat, and (barring 
the septa) even upon its surface; whereas the posterior side 
is irregular, being convex, inwardly, wfoere it is formed by the 
cranial septum; concave, outwardly, where it is opposed to 
the part composing the temporal fossa. The inferior side slants 
from behind forwards, and from below upwards, is irregular 
•on its surface, and open or deficient outwardly, where the 
cavity communicates with the maxillary sinus. Of the angles, 
one is directed upwards; another downwards, terminating in the 
nasal sinus, with which it is conjoined, the two forming one con¬ 
tinuous cavity; the third points backwards, and is directly 
