Morphology of the Human Lachrymal Bone, Sfc. 237 



into the superior lachrymo-ethmoidal cell. In 20 per cent, there is 

 a distinct aperture, sometimes of large size for this, and I have found 

 in many cases a very fine twig of the infra-trochlear nerve to accom- 

 pany the artery through this foramen, making thus, with the 

 nervulus spheno-ethmoidalis of Luschka and the proper nasal, a third 

 ethmoidal branch from the ophthalmic division of the fifth. 



VII. The disposition of the periosteum on the outer surface of the 

 lachrymal bone is worthy of note. Tracing it forward from the 

 os planum on the orbital surface, it is without much difficulty 

 divisible into two layers, and at the crista lachrymalis the innermost 

 of these again divides into two lamellse one, which keeps close to the 

 surface of the bone, lining the lachrymal groove, and is traceable 

 forwards on the nasal process of the maxilla to the level of the 

 lachrymal crest on that bone. This layer is separable from the outer 

 wall of the lachrymal sac, to which it is attached by a loose connective 

 tissue, in which many vessels ramify.* The outer layer of this 

 inner lamella unites with the entire of the outer lamella and passes 

 over the lachrymal sac as a lachrymal aponeurosis continuing for- 

 wards and inwards to unite with the former layer at the crista lachry- 

 malis anterior. These layers underlie the tnusculi lachrymales, and 

 are pierced by the canaliculi, along which, towards the puncta, they 

 send an expansion, and beneath the inferior of which the deeper layer 

 is strengthened by a more or less strong fibrous band, which starts 

 from the lower edge of the crista lachrymalis and passes obliquely 

 forwards to be attached to the outer and lower part of the crest of 

 the same name on the maxilla. This is the band which, when 

 ossified, becomes the hamulus lachrymalis, and which seems to be 

 constantly present, either in this primitive membranous condition or 

 else as a longer or shorter ossification in this membrane ; the presence 

 or absence of the hamulus is thus in reality the ossification or non- 

 ossification of a constant though variable band. Beneath this band 

 the small lachrymal branch of the infra-orbital artery passes to the 

 nasal duct, and where it arches over this vessel, the membranous or 

 bony hamulus not uncommonly gives attachment to fibres of the 

 inferior oblique muscle, for the rest of which there is usually a 

 distinct depression on the maxilla. 



I The outer connexions of the periosteal fibrous layer which lies 

 superficial to the lachrymal sac are not easily traced ; a transverse 

 section through the inner canthus shows this layer to be continued 

 forwards under the lachrymal caruncle into the ridge of fibrous tissue 

 which gives origin to the orbicularis palpebrarum, and which, when 

 detached from its surroundings, is called tendo palpebrarum. When 

 * This separation of the comparatively thin and simple mucosa along most of the 

 course of the duct from the periosteum was described by Bobin and Cadiat (" Journal 

 de la Physiologic,' ' 1875, p. 497) . 



