The _Lower Jaw_ (_c d e f g_, _Fig. 4._) on each side is made up of two Bones, but firmly united, the Extremity of the _one_ entring within the _other_ (_f_). The First (_c d e_) articulates with the _Second_ of the _Common Bones_ (_b_), where it is broad, and sends off an _Apophysis_, into which there is a _Muscle_ inserted, which helps to open the _Jaw_. There is in _this_ is a _Hole_ (_d_), for the Entrance of the Branch of the _Nerve_, which passing thro’ a _Canal_ in the middle of it, goes to the Extremity of the _Second_ Bone, and in its way sends off several Branches which go to the _Teeth_; and also a very considerable one, which goes out at (_e_), and is wholly spent upon the Neighbouring _Muscles_. The _Second_ Bone (_f g_) serves chiefly to receive the small _Teeth_, which answer to _those_ in the upper Jaw. As for the _Teeth_, they are of two Sorts, the _Great_, or poisonous _Fangs_, and the _Small_. The _Great_ (_b_, _Fig. 3._), being fixt in the First Bone of the _Upper Jaw_, are Crooked and Bent, like the _Dentes Canini_ in most _Carnivorous_ Animals. They are manifestly hollow from their Root a considerable way, not to the very _Apex_ or Point, (which is solid and sharp, the better to pierce the Skin) but to a small distance from it, as is plainly seen by splitting the Tooth thro’ the middle (_Vid. Fig. 6._). This Cavity ends at the Convex Part in a visible _Slit_, very well resembling the _Nip_ or _Cut_ of a _Pen_ (_Fig. 9. d_), which is the _Emissary_ or Outlet to the Poyson. _Galen_ (37) has given us a considerable Hint of this Make of the Tooth: For, _The Mountebanks_ (He says) _used to suffer themselves to be bit by Vipers, having first with some Pastes stopt the Holes of their Teeth, that the Venom being thus kept in, the Spectators might think they did by their Antidote secure themselves from its dangerous Effects_. The Reason why these Teeth are _Crooked_, is, That the _Point_ of the Tooth, when the Viper bites, may be _Perpendicular_ to the Part to be Wounded; for the Head being raised back in the Time of Biting, and the Tooth erected, if _this_ were strait, It would not, by reason of its oblique Situation to the part, enter with so much Force, nor so deep into the Flesh. As for the _Number_ of the Poisonous Fangs, I have observed, that there are, for the most part, besides One, Two or Three on each side, fixt Perpendicularly to the first Bone of the Upper Jaw, some others which are Young, and of a smaller Size, adhering to the same Bone: Their _Points_ are hardened, and they have their _Fissures_ formed as in the other, but their _Roots_ are Soft and Mucilaginous, like the Roots of the Teeth in Infants, and so they lye always depress’d at the _Bottoms_ of the _Former_, as may be seen _Fig. 10. c_.