CURVE OF SPEE IN MAMMALS 
183 
VII. DETERMINATION OF THE ANGLE FORMED BETWEEN THE LINE OF 
ARTICULATION AND THE BASIO-NASAL LINE 
As will be seen later, my own investigations fail to corroborate the 
statements made by Spee that there exists a close relation between 
the curve of Spee and the inclination of the fossa, but I have further 
attempted to find out what the curve of Spee means. 
While examining many skulls, in which the curvature of the curve 
of Spee differs, one relation was found; that is, when the "center 
angle" was greater, the position of the fossa was correspondingly 
higher. Furthermore, the fossa and the occipital foramen have ap- 
proximately the same relative distance from the horizontal plane. 
I attempted therefore to determine the situation of the occipital 
foramen in relation to other parts of the skull, and from the data thus 
obtained it was my hope to determine whether there is any relation 
between the position of the occipital foramen and the value of the 
"center angle." I found in the work of Topinard (1878) that Douben- 
ton first determined the situation of the occipital foramen in relation 
to other parts of the skull. Afterwards Broca attacked the same 
problem, and proposed two methods. Thus, we have three methods 
for the determination of the situation of the occipitalf oramen ; namely, 
(1) in relation to the angle between the line drawn from the inferior 
border of the orbit to the opisthion, the opisthio-nasal line (Douben- 
ton) ; (2) in relation to the angle between the occipital plane and the 
opisthio-nasal line (occipital angle of Broca); and (3) in relation to 
the angle between the occipital plane and the basio-nasal line (basilar 
angle of Broca). 
After some practice with these three methods, I came to the con- 
clusion that the last method suited my purpose best. However, to 
meet my purpose more completely, the occipital plane, which forms 
one side of the angle in the last method, was substituted by the Hne 
of articulation, because the latter line is directly related to the oc- 
clusion, while the former plane is not. Thus, I measured the angle 
(A C N)^ between the hne of articulation and the basio-nasal Hne by 
the following method. 
* For convenience in description, the abbreviated form "articular basio-angle" is used 
in place of "the angle between the line of articulation and the basio-nasal line." 
