They drop off from the Bone at the least Touch; and therefore some Anatomists have imagined them to be fastened to Muscles or Tendons, which would have rendred Them altogether Useless. For they are made to supply the Place of the Greater, when they fall away, or are pulled out by Accident, and in order to do this, they do by degrees harden, and rise more and more, till at last they stand upright, and come to a Perpendicular Situation in the Bone.
They are not all of the same Growth, for in some we can only discern the Shape of a Tooth without any Hardness, in others the Point, and in the next somewhat more is hardened, and so on to the greatest Fang.
Their Number is very uncertain, there being sometimes six or seven in each side of the Jaw, sometimes fewer.
These seem to have occasioned the Disputes among the Ancients concerning the Number of the Viperine Teeth.
The Poysonous Fangs have small Holes at the Internal Part of their Root, thro’ which the Vessels pass which carry their Nourishment ([Fig. 5. a]).
It is remarkable, that Nature has provided Young Vipers with Poisonous Teeth grown to their Perfection, that so they may kill their Prey as soon as they come into the World.
The Second Kind of Teeth, or the Small, are hooked, and bent, as well as the former, but without any Slit or Opening. Of These there are Four Rows, Two on each side of the Mouth. They are fixt in the third Bone of the Upper Jaw, and in the Second in the Lower, as exhibited to view in the Figures.
Their Use is to hold the Prey fast while Execution is done by the Bite, lest in struggling to get away, It should pull out the Fangs.
The Instruments that Emit the Venom being thus describ’d, we come next to those which serve to Prepare and Contain it.
This Liquor is separated from the Blood by a Gland on each side of the Head, placed in the Anterior and Lateral Part of the Os Sincipitis, just behind the Orbit of the Eye ([Fig. 9. a]); It lies immediately under that Muscle which helps to depress the Fangs, so that by the Action of this it is Press’d; which is an admirable Contrivance to forward the Secretion of the Juice out of it.