CURVE OF SPEE IN MAMMALS 
193 
line of the bicuspids and molars corresponds to an arc of a circle. 
These findings lead me to reject the generalization of Spee that where 
the tuberculum articulare is absent, the curve of Spee is also absent. 
As to point two: Before discussing this conclusion (2) by Spee, I 
present here my own results, which show the relation between the 
inclination of the fossa to the Hne of articulation and the length of 
the radius of the curve of Spee; also, the relation between the incli- 
nation of the fossa and the value of the "center angle" of the curve 
of Spee. 
Throughout tables 2 to 8, 10 to 13, and 15, it will be found that 
there are no reciprocal relations between these two measurements 
among individuals belonging to the same species. For example, in 
table 3, specimen 15640 has the smallest length of radius, which 
amounts to 6.00 cm., while the inclination angle of the fossa is 31.8 
degrees, the value of which is below the average (34 degrees) for the 
entire series. On the other hand, specimen 15689 has a radius of 
7.8 cm., yet the corresponding degree of the inclination angle is 43 
degrees. Condensed tables 17 and 18, which give the average values 
for the incHnation of the angle of the fossa and the average length of 
the radius, for each species in the primates and artiodactyla, show 
also that there is no reciprocal relation between those two measure- 
ments among species belonging to the same order. For example, in 
table 17, Hylobates miilleri has the smallest length of the radius 
which signifies the possession of the greatest curvature, yet the great- 
est angle of inclination is given by man. 
The data on the inclination of the angle of the fossa were obtained, 
as stated in section IV, from direct measurements on the prepared 
skull, thus disregarding the interarticular cartilage which is interposed 
between the condyle and the fossa. If therefore this cartilage were 
taken into consideration, the relation between these two measure- 
ments would be somewhat different. Fortunately, however, the men- 
iscus in the fossa of man and of the other mammals is not so thick as 
to modify the general relations already obtained. In the case of 
man, for example, the meniscus in the backward portion of the fossa 
measures 3 mm. in thickness, that in the middle portion 1 to 2 mm., 
and it is interposed between the anterior face of the articular surface 
of the condyle and the articular surface of the fossa. Finally, the 
THE JOURNAL OP DENTAL RESEARCH, VOL. I, NO. 2 
