VOL. XXX 



v.] PHILOSOPHICAL TKANSACTIONS. 21/ 



The Dissection of the Poisonous Apparatus of a Rattle-Snake, made by the 

 Direction of Sir Hans Sloane, Bart. With an Account of the quick Effects 

 of its Poison. By John Ranby, Surgeon, F. R. S. N° 401, p. 377. 



This rattle- snake was sent from Virginia, and delivered to Mr. Ranby, on 

 purpose to make such experiments with it as might inform mankind of the fatal 

 symptoms which attend its bite, and the appearances in the dead bodies of such 

 animals as have been bitten by it. Removing the common integuments of the 

 head, the muscles that raise the poisonous fangs appear; the first of which 

 arises with a short fleshy beginning, from the upper edge of the lower jaw, 

 near the articulation of one of those bones which Dr. Tyson calls maxillarum 

 dilatores, as represented at a, fig. 7, pi- 4, and sends a few carnous fibres to 

 the side of the cranium ; then becomes tendinous, and so proceeds to its inser- 

 tion in the outside of the bone, which receives the poisonous fang. Fig. 8. 



Removing this muscle, there appeared a gland, b, fig. 7» about the size of a 

 small pea, which Mr. R. takes to be one of the maxillary glands, for the fol- 

 lowing reasons : first, the structure of the parts and its distance from the fang 

 make it unlikely to be designed for separating the poisonous fluid, but rather a 

 saliva to moisten the aliment, in order to make it pass down the oesophagus 

 with ease, the stomach of those animals being but small, and the gullet con- 

 siderably larger ; not without some analogy to the ingluvies or crop of grani- 

 vorous fowls, where the food stops for some time and is moistened, before it is 

 capable of descending into the stomach. 2dly, These parts are so contrived, 

 that on opening the mouth to receive the prey, when such a fluid is most 

 wanted, the muscle abovementioned pressing on the gland promotes the dis- 

 charge of its contents into the mouth. The duct of this gland seems to open 

 between the upper lip and the jaw ; but as the excretory ducts of so small a 

 gland are rarely to be seen with certainty, Mr. R. pretends not exactly to deter- 

 mine its aperture. Under this gland lies another muscle, smaller than the for- 

 mer, which arises and is inserted near it, at c, fig. 7 ; these two muscles draw 

 the bone d, in which the poisonous fang is fixed a little outwards and upwards. 

 Between the last described muscle and gland passes a nerve, to the upper part of 

 the bone which receives the tooth e, fig. 7, and b, fig. 8 ; and it is probable 

 that this nerve has been taken for the excretory duct of the gland beforemen- 

 tioned. Opening the mouth, 2 small eminencies appear in the fore part, on 

 the inside of the upper jaw, being a membrane, raised by the fangs and drawn 

 over them like the mouth of a purse, at ab, fig. Q, and c, fig. 8. This mem- 

 brane is thick and strong, and placed in a microscope, appears to have a num- 



VOL. VII. Ff 



