ANATOMY OF THE HORSE. 
227 
Extremities. — The anterior extremity or base is broad, 
irregular, and denticulated, and articulates with the superior 
maxillary and lachrymal bones. The posterior or apiform end 
forms the zygomatic process. 
Particularities, —These bones contribute to the fonnation of 
the orbits, maxillary sinuses, and zygomatic arches; and their 
articulations exhibit a sort of dove-tail mechanism. 
Connexion, —With the temporal, superior maxillary, and 
lachrymal bones. 
> • 
LACHRYMAL BONES. (OSSA LACHRYMALIA.) 
Situation, —Antero-external part of the orbit. 
Form, —I rregularly infundibuliform. 
Division, —Into three surfaces and five borders. 
Surfaces. —The external or facial surface triangular, flat¬ 
tened, and smooth,' is bounded, laterally, by the external and 
internal facial borders; superiorly, by the orbital ridge. It ex¬ 
hibits, a little above its centre, a rounded eminence, the lachry¬ 
mal tubercle, to which is fixed the orbicularis palpebrarum. The 
internal surface is concave, but very irregularly so, being divided 
into two hollows by a cylindrical prominence, caused by the 
lachrymal conduit. It constitutes part of the roof of the max¬ 
illary sinus. The orbital surface is triangular and smooth, 
deeply excavated in front, extended and flattened posteriorly, 
and makes the antero-extemal side of the orbit. In the exca¬ 
vated part are observable a circular depression, marking the 
origin of the short oblique muscle of the eye, and, before the de¬ 
pression, the lachiymal fossa, a funnel-shaped hollow, forming 
the entrance into the lachrymal canal: within the hollow re¬ 
poses the lachiymal sac; the canal is traversed by the lachiy¬ 
mal duct. 
Borders. —Denticulate.d, with the exception of the nasal, 
which is plain. The external facial border articulates with the 
malar bone; the internal facial (including the nasal border), 
with the nasal and frontal bones; the external orbital border 
unites with the malar and maxillary bones; the internal orbital 
border with the frontal bone. 
Particularities, —A semi-transparent bone, important from 
its connexion with the lachrymal apparatus.' 
Connexion, —With the frontal, nasal, malar, and superior 
maxillary bones. 
