96 



ANATOMY AND PHYSIOLOGY OF THE IIOESE. 



Structure. — The orbit is composed of 

 unequal portions coming from four of the 

 bones of the cranium, and from three of 

 those of the face : viz., the frontal, ethmoid, 

 sphenoid, and temporal bones; the malar, 

 lachrymal, and palate bones. 



Division — Into sides, angles, base, and 

 apex. 



Sides. — The superior side or roof of the 

 cavity consists only of the frontal arch; 

 which is concave and smooth internally, to 

 make room for the lachrymal gland, and 

 has anterior and posterior borders, sharp and 

 slightly curvated. The inferior side or floor 

 of the orbit is formed hy the orbital surfaces 

 of the lachrymal and malar bones, is broader 

 than the roof, though, like it, is deficient as 

 a whole. It comprises the orbital portion 

 of the lachrymal suture : it is terminated in 

 front, hy a smooth, rounded, curvated border; 

 behind, nearly midway between the base 

 and apex, by a shorter and straighter border. 

 The internal or nasal side, the broadest and 

 only complete one, is formed principally by 

 the internal orbital process of the frontal 

 bone, into the notch of which is received the 

 OS planum: the ethmoid bone fm-ther con- 

 tributes, and also the sphenoid and palate 

 bones, the three constituting that irregular 

 termination of the cavity ' behind which 

 represents the apex. The frontal orbital 

 plate is smooth and slightly concave, and is 

 united below by a continuation of the trans- 

 verse suture with the lachrymal bone. Its 

 border in front, though slightly curvated, is 

 very irregular, having several notches and 

 one or two small foramina in it; it also 

 presents a little tubercle, to which the lach- 

 rymal caruncle is attached. The external 

 or zygomatic side is formed principally by 

 the zygomatic process of the malar bone, that 

 of the temporal contributing but little : it is 

 concave, and smooth internally, somewhat 

 broader below than upwards ; is intersected 

 obliquely by the zygomatic suture, and has 

 an interior border, smooth and curvated, a 

 posterior one, sharp and straight. 



Angles. — The supero-internal angles, one 

 before, the other behind, are formed by the 

 beginning of the frontal arch, through which, 



midway between them, passes the supra- 

 orbital foramen. The infero-internal angle 

 includes tlie lachrymal fossa. The supero- 

 cxtcrnal angles, one anterior, the other pos- 

 terior, are intersected by the suture uniting 

 the frontal and zygomatic arches. The 

 infero -external angles, particularly the ante- 

 rior, are rounded and smooth. 



Base. — Of the circumferent border, the 

 superior and internal parts, about two-fifths 

 of the entire circle, are formed by the os 

 frontis ; the inferior and internal parts, about 

 one-fifth, by the lachrymal bone ; and the 

 remaining two-fifths by the malar and tem- 

 poral bones, in the proportion of three parts 

 of the former to one of the latter. 



The apex or back of the orbit, formed by 

 the ethmoid, spenoid, and palate bones, is 

 pierced by five foramina : the two round are 

 the internal orbital and optic, which are 

 ranged in a row with two oval and larger 

 in size, the supero-posterior and infero-pos- 

 terior orbital; the one behind is the spinal 

 foramen. 



III. CAVITIES OF THE NOSE, 



Comprehending the nasal fossae or cham- 

 bers, and the sinuses. These cavities occupy 

 about tsvo-thirds of the internal space of 

 the superior maxilla, the remaining third 

 belonging to the cranium ; from which they 

 are partitioned by the cranial septum of the 

 frontal bone, in union with the cribriform 

 plates and crest of the ethmoid. 



The nasal fossae may be said to include 

 about two-thirds of the entire space de- 

 voted to the olfactory cavities. They con- 

 stitute the interior of the proboscis ; have 

 four boundary walls, one above, one below, 

 and two laterally ; are separated from each 

 other by a septum ; but are open both be- 

 fore and behind. 



The superior wall presents an irregular 

 concave formed by the internal surfaces of 

 the nasal bones, the cells and grooves of the 

 ethmoid, and small portions of the nasal 

 surfaces of the palate bones. 



The inferior waU is horizontal ; it extends 

 forward beyond the superior, but is con- 

 siderably overreached by that wall poste- 



