186 
MASARU NAGAO 
TABLE 20 
Data on the length of the radius of the curve of S pee for various species. 
to the diminishing values for the radius 
Arranged according 
NAME OF SPECIES 
Camelus bactrianus 
Rhinoceros 
Rangifer tarandus 
Dicotyles sp 
Lama huanacho 
Porcus babyrussa 
Macacus nemestrinus . . . 
Nasalis larvatus 
Man 
Simia satyrus 
Didelphys marsupialis . . 
Macacus cynomolgus . . . 
Semnopithecus femoralis 
Hylobates miilleri 
Fiber zibethicus 
23.99 
23.28 
17.10 
14.95 
13.56 
11.22 
10.17 
7.82 
7.55 
7.43 
6.54 
6.02 
5.94 
5.50 
3.64 
Discussion 
As to the physiological and anatomical significance of the curve 
of Spee and as to the relation of the curve of Spec to the other parts 
of the skull, Spee (1890) has put forward the opinions which were 
briefly summarized at the beginning of this paper, and it is now my 
intention to reconsider these statements of Spee in the light of my 
own data. 
It is evident, from the data in tables 2 to 18, that there is no direct 
relation between the value of the "center angle" of the curve of Spee 
and the values of a, /3, and 7, either among different individuals of 
the same species, or for different species of the same order. Since a 
has always a fixed relation to the total length of the teeth and 7 to 
the length of the lower jaw in the same species, it must be conceded 
that both the total length of the teeth and of the lower jaw have no 
relation to the value of the "center angle" of the curve. Further- 
more, since it is conceivable that the length of the lower jaw has a 
fixed relation to both the length and the size of the skull in the same 
species, we may conclude tliat there is no correlation between these 
