344 Proceedings of Royal Society of Edinhttrgh. [sess. 
irregularity in their position more common in the teeth of the 
human subject than in those of the lower animals. At the same 
time, while they may not so manifestly exhibit the screw thread 
appearance, they sufficiently indicate an axial turn or twist in their 
construction. This in many cases becomes more easily perceptible 
on looking along the tooth on its long axis from the apex of the fang 
towards the crown, when the tendency to a slight spiral or winding 
in the contour will be at once apparent, the crown face of the tooth 
being turned inwards at its distal border, while the fang extremity 
inclines in an opposite direction. 
A somewhat curious circumstance attaches to the formation of 
the multiple- fanged teeth — the molars — in the human subject. In 
a lower molar tooth, with its two fangs well developed (fig. 13) — 
the larger and better marked being anterior, and the smaller posterior 
— each will be found somewhat flattened as in the single-fanged 
teeth, and, like them, each one indicating the same bias towards the 
spiral tendency they present. Each fang in this way appears as if it 
belonged to a single-fanged tooth, but that two such teeth had been 
fused together at their crowns so as to constitute one double-fanged 
molar.* Both these fangs are in the lower molars besides bent 
so as to be directed somewhat backwards. In the upper molars, 
however, where each tooth possesses three instead of two fangs, 
of much the same form as those of the lower jaw, the direction 
taken by one of them seems to differ from the others (fig. 14). 
The three fangs are arranged so that two of them are situated one 
behind the other on the outer or buccal side of the tooth, while the 
third is placed in the inner or palatal side of these. The two 
external fangs resemble those of the lower molars in being directed 
backwards; but in by far the greater number of instances the internal 
or palatal fang — the larger of the three — points, in the normally- 
formed tooth, slightly forwards, while the spiral rotation on its long 
axis would at the same time appear, in contrast to the others, as if 
it were reversed. These appearances are not very easily described, 
but they correspond to what would occur if the original tooth pulp 
* An hypothesis of this kind has been advanced in regard to the molars of 
the Elephant and some other animals — extending even to Man — by Rose, 
Knkenthal, Dybowski, Gervais, Gandry, and others, in contradistinction to 
those, such as Leche, who believe the molars to be simple teeth. 
