The anterior margin of the lacrymal groove formed by the ascending ridge subdividing the outer surface of the nasal process of the supe rior maxillary bone, is thick and rounded. The posterior margin, formed by the crest which subdivides vertically the orbital surface of the lacrymal bone, is thin and sharp.
Inferiorly the crest of the lacrymal bone forms a small curved prolongation directed for wards and outwards, which serves to form the commencement of the posterior wall of the osseous canal for the nasal duct. The process, which is called hamulus ossis lacrymalis, arti culates with the orbital plate of the superior maxillary.* The osseous canal for the nasal duct.—The osseous nasal canal, about half an inch in length, extends from the lower extremity of the lacrymal groove to the lowest meatus of the nose, at the anterior part of which it opens. Its orifice is overhung by the anterior extremity of the lowest spongy bone. The osseous nasal canal is directed a little obliquely from before back wardst' and from within outwards. It is somewhat narrower in the middle than at either extremity. It is compressed from within out wards, hence a horizontal section is rather elliptical than circular.
The anterior and outer walls of the osseous canal are formed by a groove inclined down wanls and backwards on the inner surface of the body of the superior maxillary bone, the continuation of that on the nasal process which contributes to form the lacrymal groove. The posterior wall of the canal is in great part formed above by the hamular process of the lacrymal bone, where it articulates with the orbital plate of the superior maxillary. The lowest part of the posterior wall is formed by the meeting together of the lacrymal process of the lowest spongy bone and the posterior margin of the groove in the superior maxillary, constituting the anterior and outer walls. The internal wall of the osseous nasal canal is formed superiorly by a continuation of the osseous surfaces composing the lacrymal groove. Below, it is formed, in front, by a farther con tinuation of one of these surfaces, viz. that of the superior maxillary bone, and behind by a thin plate of the lowest spongy bone, the nasal or lacrymal process of the lowest spongy bone, which rises to join the inferior edge of the lacrymal. The anterior edge of this process
of the spongy bone joins the posterior edge of the lower part of the lacrymal surface of the nasal process of the superior maxillary. The line of junction is thus the continuation of that at the bottom of the lacrymal groove.
Lacrymal papilla', points and canalicules.— ( Fig. 15.) At the inner extremity of the ciliary canalicules, canaliculi lacrymales, s. cornua limacum ; Fr. Les conduits lacrymaux ; Ital. I condotti lagrimali ; Germ. Die Thriinen kanalchen ; lead from the lacrymal points into the lacrymal sac. From the superior lacrymal point the superior canalicule proceeds upwards and outwards within the papilla a little way, then suddenly bending at an acute angle and forming at the same time a small dilatation, it runs downwards and inwards, inclosed in the fold of skin and conjunctiva forming the upper border of the fissure of the nasal can thus, to the lacrymal sac. The course of the inferior canalicule is the counterpart of the above. From the lower point it runs a short way perpendicularly downwards and outwards within the corresponding papilla, then bend ing abruptly and1ike the upper forming a small dilatation, it proceeds upwards and in wards, inclosed in the fold of skin and con junctiva forming the lower border of the fissure of the nasal canthus, to the lacrymal sac.
The canalicules having met each other at the commissure of the fissure of the nasal canthus, pass under the tendon of the orbicularis mus cle, and open by separate orifices, close to each other however, into the anterior and outer part of the lacrymal sac. These orifices indeed are separated merely by a duplicature of the mucous membrane composing their walls.
The lacrymal canalicules have pretty firm walls of mucous membrane, which do not col lapse, but when cut across are seen gaping open. The calibre of the canaliculi is about the thirtieth of an inch in diameter; that of the points is less, but these are capable of being dilated.