244 Prof. A. Macalister. Notes on the Varieties and 



the orbital border is as variable in the twelve foatal crania under fonr 

 months which I have now before me as in the same nnmber of ado It 

 skulls. 



Of the later changes taking place in the development of the 

 lachrymal bone the principal is the assumption of a more vertical 

 position. The embryonic lachrymal until the end of the eighth month 

 is inclined inwards at an angle of from 60 to 70, but after birth it 

 rapidly becomes more vertical and the surface develops its outward 

 concavity from above downwards, the first appearance of which 

 immediately precedes birth. The degree of obliquity of the foetal 

 lachrymal at birth may be represented by an inter-lachrymal index, 

 that is, the maximum distance between the upper margins of the two 

 lachrymal bones multiplied by 100, divided by the maximum distance 

 between the lowest margin of the two bones. This in ninth month 

 skulls averages 72. 



X. In the adult the position and obliquity of the lachrymal bone 

 depends on several factors, the size of the orbits, the internasal 

 width, the width of the respiratory region of the nose, the degree of 

 projection of the frontal bone, all influence it. The curve of the 

 surface is not uniform, the lower third being generally turned rather 

 sharply outward. The simplest method of estimating both the 

 obliquity and curvature of the surfaces is by comparing the relative 

 distances between the respective points of the two lachrymal bones. 

 The average superior inter-lachrymal width or distance between the 

 posterior superior angles of the two lachrymals is 25'2 millions. The 

 posterior inferior inter-lachrymal width or distance between the 

 posterior inferior angles, measured from the point of contact of 

 lachrymal, ethmoid, and maxilla on each side is 30 millims., and the 

 anterior inferior inter-lachrymal width, or that between the most 

 divergent points of the two lachrymals, the extreme inferior point of 

 the crista (not taking the hamulus into account), is 33'4 millims- 

 The amount of inclination may be expressed by two indexes which I 

 may call the anterior and posterior inter-lachrymal indexes. The 

 latter of these (superior inter-lachrymal width X 100, divided by 

 posterior inferior inter-lachrymal width), indicates the degree of 

 obliquity of the upper two thirds of the bone. The former 



| '- '- ) indicates the obliquity plus the curve of the lower 



\ a.i.t.w J 



third, the amount of which can be estimated by comparison of the 

 two indexes. The average anterior inter-lachrymal index =75, the 

 average posterior =84. The former index decreases with increasing 

 splay of the lower margin, the latter with increasing general 

 obliquity. 



These degrees of obliquity seem to vary in different races. In the 

 crania of negroes from South- West Africa the bone is most vertical ; 



