22 PHYSIOLOGY AND TOXICOLOGY 



the fang, whicli, rising, thrusts off, from its convexity, the cloak-like vagina-dcntis 

 so that it gathers in loose folds at its base. 



As the unsheathed tooth penetrates the flesh of the victim, a series of move- 

 ments occur, which must be .contemporaneous, or nearly so. The body of the 

 snake still resting in coil, makes, as it were, an anchor, while the muscles of the 

 neck contracting, draw upon the head so violently, that when a small animal is 

 the prey, it is often dragged back by the effort here described. If now the head 

 and fang remained passive, the pull upon the head would withdraw the fiing too 

 soon; but at this moment, the head is probably stayed in its position by the 

 muscles below, or in front of the spine ; while the pterygoideus exteruus and 

 spheno-palatine, acting upon the fang through their respective insertions, into the 

 posterior apophysis of the submaxillary bone, and the inside of the palate bone, 

 draw its point violently backwards, so as to drive it more deeply into the flesh. 

 The muscles alluded to, therefore, antagonize the spheno-pterygoid. 



At this instant, occurs a third series of motions, which result in the further 

 deepening of the wound, and in the injection of the poison. 



The lower jaw is closed upon the bitten part, or member. Where the surface 

 struck is flat and large, this action will have but slight influence. Where the jaw 

 shuts on a small limb, or member, the consequent effects will be far moi'e likely to 

 prove serious, since the power thus to shut the mouth materially aids the purpose 

 of the blow. The closure of the jaw is effected by the posterior middle, and ante- 

 rior temporal muscles. The fii-st two tend simply to shut the mouth ; the anterior 

 temporal, however, is so folded about the poison gland, that while it draws up the 

 lower jaw, it simultaneously compresses two-thirds of the body of the gland. 

 This force is applied in such a manner as to squeeze the fluids out of the upper and 

 back parts of the gland, and drive them forwards into the duct. The anterior 

 lower angle of the gland, as well as a portion of the duct, is subjected to similar 

 pressure at the same instant, owing to the flat tendinous insertion of a part of the 

 external pterygoid upon the parts in question. 



It will thus be observed, that the same muscular acts which deepen the wound, 

 fix the prey, and inject the venom through the duct, and into the tissues pene- 

 trated by the tooth.' The whole process here described at such length, is the work 

 of an instant, and the serpent's next effort is to disentangle itself from its victim. 

 This step is effected by relaxing the muscles of the neck, so as to leave the head 

 passive, while the continued traction of the muscles of the body pull upon it, and 

 thus withdraw the fang, over which glides the elastic mucous sheath as the 



^ It follows from the observations of Dr. Johnston, and Prof. Wyman, that no tissue connection 

 exists between the venom duct and the basal opening in the fang. It becomes necessary, under these 

 circumstances, to explain how the jioison is can-ied from one to the other. Usually the projecting papilla 

 at the end of the duct, is held by the gum in close contact with the fang opening, and when the fang, in 

 rising, thrusts back its mucous cloak, this presses upon the parts at the base of the fang so firmly, as to 

 bring them into perfect apposition. This explanation is given by Prof Wyman. It does very often 

 happen, however, that a part only, or even none, of the vetiom enters the fang, but is violently ejected 

 between that weapon and the edges of the vagina dentis. 



