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. ’Tis a _Conglomerated_ Gland, composed of many smaller ones contained in a common Membrane; each of These sends off an Excretory Vessel, all which do afterwards Unite and Form one _Duct_ (_b_), which running towards the Roots of the Fangs, discharges the Yellow Liquor into a _Bag_. This _Bag_ is fixt to the _Basis_ of the _first_ Bone of the Upper Jaw, and also to the Extremity of the _Second_, covering the Fangs near the Root (_d_, _Fig. 10._). To the upper Part of this _Vesicula_ there is joined _another_ (_a_), in the Anterior Part of which there is a Passage for the Poisonous Teeth.