CURVE OF SPEE IN MAMMALS 
161 
me to study at the Institute, and in furnishing me with all the material 
and instruments necessary for the present investigation. Also I wish 
to express my thanks and gratitude to Dr. Turner and Dr. Hatai, for 
their kindness and interest shown me during the course of this 
investigation and in the revision of this paper. 
n. MATERIAL USED IN THESE STUDIES 
The skulls used for this study belong to the collection in the mu- 
seum of the Wistar Institute of Anatomy and Biology, and had been 
prepared by the usual method for the purpose of exhibition. Nearly 
120 skulls, representing several orders of mammals, and apparently 
of adult age, as shown by the presence of the well developed third 
molars, were available. On account of the difficulty in getting human 
skulls which show the ideal occlusion, only fourteen human skulls out 
of this series were utilized, though for the other orders of mammals, 
this selection was easier. In the cases of Porcus babyrussa. Lama 
huanacho, Cervulus muntjac, and Rhinoceros, however, I found only 
one specimen for each species. 
In this paper I have followed the classification used by Brehm in 
his "Tierleben" (third edition, 1890). There are some orders of 
mammals which I did not study owing either to the difficulty in 
getting specimens, or because of the absence in them of the curve of 
Spee. The name, the locality (or race in the cage of man), and the 
sex of each individual, as well as the museum catalog number, are 
given in table 1. 
Examination of the material 
Preliminary to the study of the curve of Spee, I attempted to 
determine the following two points on every skull used. 
1. Whether or not the curved line, which is drawn touchijig the 
summits of the buccal cusps of the bicuspids and molars, would cor- 
respond to the arc of a circle with its convexity downwards. 
2. If so, whether the extension of the curved line backwards touches 
the anterior face of the articular surface of the condyle? 
I shall first present briefly the various methods employed for these 
determinations. 
