

Morphology of the Human Lachrymal Bone, $c. 249 



Professor Gegenbaur, in his valuable paper on the pars facialis of 

 the lachrymal bone (" Morph. Jahrbuch," 1882, p. 173,), has pointed 

 out that the hamulus is the passage between the pars facialis and the 

 pars orbitalis. The former, present as a definite element in 4'25 per 

 cent, of orbits is, as he has indicated, an atavism. 



In man the nasal process of the maxilla very early projects in front 

 of the anterior border of the ethmoidal lateral mass, and thus 

 encroaches on the territory which in earlier conditions was only 

 occupied by the lachrymal. The ossification, extending upwards, 

 stretches on both sides of those branches of the infra-orbital artery, 

 which turn in to terminate on the mucosa clothing the front of the 

 ethmoid, making thus the line of vessels or sutura notha. 



In the development of the large lachrymal bone of the pig ossifica- 

 tion springs from a common centre, from which it extends around the 

 duct. In man, in those cases wherein an ossiculum hamuli exists, 

 there is really a second ossific centre in the bone, and in those 

 instances in which an ossiculum maxillo-frontale exists, this bony 

 segment of that part of the nasal process of the maxilla overlying the 

 ethmoid has had its special centre. All these facts are instructive as 

 showing the comparatively low morphological value of mere centres 

 of ossification. 



EXPLANATIONS OF THE PLATES. 



The following letters refer to most of the figures. 



e = oa planum of ethmo'd. 

 e. i.= ossiculum ethmo-lachrymale inferior. 

 e. s.= ossiculum ethmo-lachrymale superior. 



f. = orbital plate of the frontal. 

 f. v. = vascular foramen. 

 Ti. hamulus. 

 l.= lachrymal bone. 

 lac. = lacuna. 

 m. = malar. 



m.-l.-s. = maxillo-lachrymal suture. 

 mx. maxilla. 

 o. c.= ossiculum canalis. 

 o. h. = ossiculum hamuli. 

 o. m.f. ossiculum maxillo-frontale. 

 *. i. t.= sutura infraorbitalis transversa. 

 *. i. v. = sutura infraorbitalis verticalis. 

 . . = sutura notha. 



;1. Orbital surface of lachrymal bone of foetus, middle of fifth month x 30. 

 2. Transverse section of nasal process of right maxilla of girl, aged about 24. 

 p. . = processus lachrymalis ; c. 2.=crista lachrymalis x 10. 

 3. Transverse section of lachrvmal region in foetal skull of twelfth week. a = 

 cartilaginous septum ; b and c = ethmoidal cartilage; d = periosteum ; e = section of 



