CURVE OF SPEE IN MAMMALS 
201 
ularis is not supported, the data on these two measurements failing 
to indicate a definite relationship (see tables). 
(b) The existence of the curve of Spee was established in animals 
which have the tuberculum articulare, as well as in some animals 
(e.g., the muskrat) without the tuberculum. Even among animals 
which have the tuberculum, the teeth do not always exhibit the curve 
of Spee, but in some cases (e.g., the wild pig) lie in a straight line. 
Therefore the existence of the curve of Spee is not necessarily associ- 
ated with the presence of the tuberculum articulare. 
(c) Spec's opinion, that the path of the lower jaw during its antero- 
posterior movement is on the curve of Spee, cannot be accepted. The 
arguments on this question, from the standpoint of the mechanism 
of the jaw during mastication, as well as from the morphological 
examination, are presented in the text. I am therefore inclined to 
believe that the curve of Spee is not closely related either to the man- 
ner of movement of the lower jaw, or to the efficiency of mastication. 
6. A reciprocal relation between the value of the "center angle" 
of the curve of Spee and the value of the angle of the line of 
articulation to the basio-nasal line (articular basio-nasal angle), was 
found in the primates, with the exception of man. 
7. The real significance, physiological and anatomical, of the curve 
of Spee is not clear. 
LITERATURE CITED 
Bkehm, a. C 1890 Brehm's Tierleben. Leipzig und Wien. 
FiCK, R. 1911 Eandhuch der Analomie u. Mechanik der Gelenk. dritter Teil, pp. 1-35. 
Fischer, Jena. 
Gysi, a. 1910 The Dental Cosmos, ]ii, 1. (Being a translation of Professor Gysi's 
book Beiirag sum Articulationsproblem, published by Hirschwald, Berlin, in 
1908, with some practical additions written since its publication). 
Hopewell-Smith, A. Dental Anatomy and Physiology. Lea and Febiger, Philadelphia, 
pp. 168 and 172. 
KiLABBE, H. 1892 Einige Bemerkungen iiber die mechanischen Verhaltnisse der Kau- 
werkzeuge und der Kaubewegungen. Deutsch. Zeitschr. f. Tiermedizin u. 
vgl. Pathologic, xix, 33. 
LuBOSCH, W. 1906 Semon's Forschungsreisen, iii. Jena Zeitschr., pp. 549-606. 
LuBOSCH, W. 1907 Universelle und spezialisierte Kaubewegungen bei Saugetieren. 
Biol. Zentralhl., xxvii. 
Meyer, H. 1865 Das Kiefergelenk. Arch. f. Anat. n. Physiol., pp. 719-731. 
Port and Euler 1915 Lehrbuch der Zahnheilkunde, pp. 186-207. 
