Morphology of the Human Lachrymal JBone, Sfc. 233 



concave (1 per cent.) This is the margin which is the most 

 frequently ankylosed, and was more or less synostosed to the maxilla 

 in 4 per cent. In these cases this border is marked by a row of 

 foramina which transmit vessels and which sometimes are of con- 

 siderable size (fig. 33). These foramina can be seen, even before 

 aukylosis, in rather more than 10 per cent, of the specimens 

 examined. One large hole exists at the anterior superior angle in 

 20 per cent, of the cases examined (fig. 25). The lower end of the 

 anterior margin extends downwards into the canal below the level of 

 the hamulus in 80 per cent, of the bones, the upper end is confluent 

 with the top of the crista in 8 per cent. This margin unites in a 

 somewhat variable way with the nasal process of the maxilla, some- 

 times it forms with it a simple squamous suture, overlapping it, with 

 the intervention of a thin layer of periosteum, sometimes it forms with 

 it a harmonia, but in the largest number of cases examined (per- 

 centage not determined), the margin of the lachrymal widens and 

 tends to split into two lamellae, one passing in front, and the other 

 behind the maxilla, forming thus an imperfect schindylesis. The 

 lamella which passes internal to the maxilla is usually better marked 

 above, that which lies external is better marked below ; but I have 

 not found a perfect schindylesis in any, as the two lamellae have never 

 been sufficiently developed to embrace the margin of the nasal 

 process. 



The inferior external margin, as seen in the orbit, is the most 

 uniform and the least frequently ankylosed (\ per cent.) ; it always 

 lies on a plane external to the superior, and passes from behind 

 forwards and upwards ; its posterior angle is nearly always rounded. 

 This edge is sometimes a harmonia, but most commonly tends slightly 

 to overlap the maxilla. Of its anterior termination we shall see the 

 varieties when considering the hamulus. It is seldom irregular or 

 lobulated, sometimes rectilinear and horizontal, but most commonly 

 presents a single convexity. 



Of all the margins the posterior is that which shows the greatest 



lount of lobulation, and it is sometimes deeply indented by bays, 

 sometimes one or two of these extend almost to the crista lachrymalis ; 

 more rarely it sends a spur backwards into the ethmoid ; this I have 

 seen in three instances. In another instance a long process of the 

 os planum of the ethmoid projected forwards below the lachrymal 

 bone and . below the inferior lachrymo-ethmoidal ossicle, separating 

 these from the maxilla as far as the crista lachrymalis. 



IV. The varieties of crista lachrymalis and of hamulus are very 

 mmerous, but may be reduced to four types 



A. Simple lamellar forms with obsolete crest. 



B. Simple carinate forms. 



C. Carino-acuminate forms. 



