336 Proceedings of Royal Society of Edinburgh. [sess. 
Notes on a Peculiarity in the Form of the Mammalian 
Tooth. By J. Smith, M.D. (Illustrated.) 
(Read December 3, 1894.) 
The ideal type of a mammalian tooth is here assumed to be a 
modified cone, or, as in certain molar teeth, a combination of 
cones, the vertex or vertices, as the case may be, corresponding 
either to the apex of the fang, or to the free extremity of the 
crown, or to both, as in the typical canine tooth, where two cones 
seem united by their bases. (Fig. 4.) 
Such cone is supposed to be one of considerable altitude, with 
the axis at right angles to the base. In the natural tooth, however, 
the axis would, under various circumstances, be more or less bent, 
or arched, or oblique in its direction, and the cone itself laterally 
compressed or flattened, or in various other ways modified. (Figs. 
1, 2, 3.) 
In the morphology of the joints and certain other parts of the 
skeleton the principle of a spiral or curve of double curvature has 
been traced by the researches of Meyer, Danger, Henke, Meissner, 
Goodsir, and others ; and so far back as 1858, a short paper by me, 
“ On the Condyle of the Human Lower Jaw,” and, in accordance 
with such views, was communicated to this Society by Professor 
Goodsir. Further inquiries led me, in 1864, to advance the pro- 
position that a spiral tendency was indicated in the form of the 
human tooth, although in its case, owiug to various causes, this 
confirmation is in many instances comparatively indistinct. Since 
that time, again, a number of observations made on the teeth of 
various orders of mammals have suggested some additional views 
on this subject, as not only interesting in a morphological and 
teleological aspect, but possibly of some surgical importance. 
Speaking generally, then, the single-fariged mammalian tooth, as 
represented by such elongated and compressed cone, seems to be 
again modified by being twisted upon itself. This ranges from the 
faintest trace of a s]3iral indicated in the form of the tooth, as if it 
