The instrument with which the cobra and other venomous serpents are armed in so deadly a manner, consists of several parts, namely, the tooth or poison fang, the movable stock or handle in which it is fixed, called the jaw, the muscles or moving powers of the jaw, the bag containing the deadly liquid called the poison sac, the pipe which carries the ve nom into the tooth or poison duct, and the squeezer or muscle that drives the venom from the bag,along the duct, through the tooth into the wound which the latter inflicts. The tooth is not implanted in a socket like ordina ry teeth, but is firmly soldered, as it were, to the jaw bone, which commonly has no other tooth to support, and is singularly modified in size and shape, to allow of the movements re quisite for the deep plunge of the tooth into the object aimed at. The tooth, in structure resembles what is called the canine tooth, which consists of a hard, pointed, long and slender cone, with a hollow base, and if we suppose such a slender and partly hollow cone to be rolled out flat, the edges then bent to wards each other, and soldered together so as to form a canal open at both ends, we shall torm a good idea of the general form and structure of a poison fang. The edges of the flattened tooth wheel we have supposed to be so approximated, are bent round the end of the poison duct, which closely adheres to and lines the canal, and the line of union ot the two edges runs along the front and concave side of the slightly curved fang. The barrel aperture of the poison-canal is oblique and its opposite or terminal outlet is still more so, presenting the form of a narrow elliptical lon gitudinal fissure at a short distance from the fang's point, this is left solid and entire, and fit for the purpose of perforation. It is only the upper jaw that is so armed, and it is so formed that the upper jaw of the venomous serpent is not fixed, but plays or rotates backwards and forwards, having special muscles for those movements which, when they push forward the jaw bring the tooth attached to it into a vertical position, ready for action, and when they draw back the jaw, replace the tooth in a horizontal position, where it rests, with the point backwards, hidden in a bed of solt and sliry gum. The wound is inflicted by a blow rather than by a bite, the poison tangs, when erected, are struck like daggers into the part aimed at, and as the action of the compressing muscles of the bag is contemporaneous with the blow by which the wound is inflicted, the poison is, at the same moment, injected with lorce into the wound from the apical or termi nal outlet ot the perforated fang.