Morphology of the Human Lachrymal JBone, fyc. 231 



groove, as well as the lower part of the orbital plate behind it, the 

 upper corresponded to the top of the orbital plate of normal 

 lachrymal bone ; they are separated by a membranous interval. 

 Possibly this should be classed with the cases, to be after mentioned, 

 of superior ethmo- lachrymal ossicles, but the upper bone took the 

 place of the upper fourth of the crista lachrymalis, and so differed 

 from all the instances of ossicle with which I have met. 



In one other instance of divided lachrymal the two parts were 

 separated, not by a membranous space, but by a projecting ridge of 

 the os planum which traversed the lachrymal and touched the 

 frontal. This was an instance of the overgrowth of the wall of 

 the partition between the upper and lower lachrymo-ethmoidal cells 

 jutting through the surface scale of lachrymal. Professor Gruber 

 has described a somewhat similar case (" Miiller's Archiv," 1848, 

 p. 412, T. xiv). In a South American skull I have seen a similar 

 spur traversing the lachrymal as far as the crista. 



7. Development of a narrow string-like lachrymal along the crista, 

 with a very narrow lachrymal part in front, and a still narrower 

 orbital slip behind; this, which is the persistence of an early 

 embryonic form, is rare. I have notes of three cases only. In one of 

 these the bone was not more than 2'5 millims. broad, and lay along 

 the front of the ethmoid. In the other the strip was closely 

 perforated with holes, another embryonic character ; in neither was 

 there any hamulus lachrymalis. 



8. In rather more than 2 per cent, the bone is composed of a coarse 

 reticulum whose meshes in the recent state are closed by membrane ; 

 most of such cases are old bones, and the holes are due to absorption 

 consequent on dilatation of the ethmo-lachrymal cells, but in some of 

 those examined the same condition occurred in young crania, and in 

 most of the recent orbits in which such deficiencies were noticed the 

 bone had a continuous sub-periosteal membrane over these holes. 

 Ten of these bones were reduced to a few trabeculae which were the 

 remains of those parts of the normal bone which are thickest and 

 densest, viz., the crista and the rods between the upper and lower 

 lachrymo-ethmoidal cells, and a bar along both the superior and the 

 inferior margins. 



In five of these cases of deficient lachrymal bone islands of the 

 ethmoid filled in the holes ; two of these were very old crania. 



e. In several crania, three at least, a space closed by membrane 

 existed between the back of the lachrymal and the anterior margin 

 of the os planum. In one I found a similar membrane-closed space 

 between the front of the lachrymal and the back of the nasal process 

 of the maxilla ; both of these were much fenestrated bones. 



In all these cases of fenestration the deficiencies of the bone were 

 opposite the middle of the lachrymo-ethmoidal cells, and the reticular 



