This consists of Muscular Fibres, both _Longitudinal_ and _Circular_, by Means of which it can _Contract_ it self when the Fangs are erected; and by this Contraction the _Venom_ is press’d into the Hole at the Root of the Tooth, and forced out at the Fissure near the Point. That this is so done, I have frequently observed with the naked Eye, having cut off the Head of a Viper, and immediately pinching the Neck to make it open the Mouth wide; for by this means the Venom was _Squirted_ out as from a _Syringe_. When the Viper lyes quiet with its Mouth shut, the Fangs are depress’d and covered with the _External Bag_; when it intends to bite, it opens the Mouth very wide, at the same time the lower Extremity of the _Second_ of the _Common_ Bones (_Fig. 4. b_) is moved forwards by proper Muscles, and turns as it were upon the fixt Centre (_b_), thus pushing forward the Upper and Lower Jaws, whose Extremes are united at (_c_). By this means the Lower Part of the First Bone of the Upper Jaw (_Fig. 3. a_) is thrust forwards, the other Extremity turning in the Cavity of its Articulation, where it is fastned by _Ligaments_; the Fangs being by this Mechanism Erected, the Bags which covered them, by the Contraction of their _Longitudinal_ Fibres, are pulled back, and the Action of the _Circular Ones_ does at the same Time straiten the _Internal_ Bag, and force the _Juice_ into the Teeth. Besides this, when the Viper bites, It strikes in the Fangs to the very Root; and thus the _Vesiculæ_ are still more squeezed for the Discharge of the Liquor. It is worthy our Observation, that the Viper can move the Jaw Bones on _one_ side without moving Those on the _other_, for they are not joined together at the Extremes as in other Animals; which Contrivance is very beneficial to it in the _swallowing_ its Prey; in that, while the Teeth on one side stand unmoved, and fixt in the Flesh to hold it, _Those_ on the other side are brought forward, to draw it in farther, then they keep it fast till the former Jaws advance again in their _Turn_. Thus they act successively, and force the Animal intire (there being no _Dentes Incisivi_ or _Molares_ to divide it) into the _Œsophagus_, whose Muscular Fibres are very Weak, and can help but little in the Business. It may not be amiss to conclude these _Remarks_ with a short _Hint_ concerning the _Organs of Hearing_; Mr. _Charas_ (who is however followed by others in _it_) having, as we mention’d before, Entertain’d a very absurd Opinion about _Them_. _These_ then are placed in the _Temporal_ Bones, as in other Animals, and consist of _One_ long, small _Bone_ (_Vid._ _Fig. 11._), like _that_ of _Birds_, whose Extremity is broad, like the _Basis_ of the _Stapes_ in _Man_, and situated upon a little _Hole_ which opens into the _Labyrinth_; and besides of _three Demicircular Canals_ (_Fig. 12. a b_) which also open into the _Labyrinth_.