Reprinted from The Jooinal of Dental Researcb 
vol. i, DO. 2, June, 1919 
COMPARATIVE STUDIES ON THE CURVE OF SPEE IN 
MAMMALS, WITH A DISCUSSION OF ITS RELATION 
TO THE FORM OF THE FOSSA MANDIBULARIS 
MASARU NAGAO 
Dental Hospital of the Department of Education, Tokyo, Japan 
From the Wislar Institute of Anatomy atid Biology, Philadelphia 
CONTENTS 
I. Introduction 159 
II, Material used in these studies 161 
Examination of the material 161 
Results of the examination 168 
III. Selection of the standards to be used for the purpose of comparing the curve 
of Spee given by various mammals 170 
IV. Determination of the length of radius 171 
V. Determination of the inclination of the fossa mandibularis 178 
VI. Determination of the dental and gnathic indices 182 
VII. Determination of the angle formed between the line of articulation and the 
basio-nasal line 183 
VIII. Comparative study of the curve of Spee 184 
The author's own data 184 
Discussion 186 
Relation between the "center angle" of the curve of Spee and the angle of 
the line of articulation to the basio-nasal line 189 
IX. Relation between the form of the fossa mandibularis and the curve of Spee.. 191 
X. Summary 199 
XI. Literature cited 201 
I. INTRODUCTION 
In 1890 Spee described some peculiarities of the occlusion of the 
bicuspids and molars, which are closely related to the form, and es- 
pecially to the inclination, of the fossa mandibularis and the manner 
of movement of the mandible, and which have an important bearing 
upon the efficiency of these teeth as masticatory organs. A free 
translation of his initial statement follows : 
"If a curved line be drawn touching the summits of the buccal cusps of 
the upper or lower teeth from first bicuspid to third molar, it will more or 
159 
THE JOtTRNAL OF DENTAL RESEARCH, VOL. I, NO. 2 
