PHYSIOLOGY AND TOXICOLOGY 



CHAPTER II. 

 ANATOMY OF THE VENOM APPARATUS. 



The subject of the myology of the Rattlesnake has been considered at length, 

 in several systematic works, and in the monographs referred to at the close of this 

 paper. For the fullest details, it would be necessary to refer the reader to the 

 books in question. Since, however, it is impossible otherwise to convey an accu- 

 rate idea of the mode in which the fangs are employed, I am forced to describe the 

 parts concerned, and the general mechanism of their motions. It is the more 

 necessary to dwell, at least, briefly, on this matter, because some of the French 

 observers have fallen into error, as regards the action of certaiu of the muscles 

 concerned in the elevation and depression of the fangs. 



I shall first describe, as shortly as possible, the bones involved ; then the muscles, 

 and lastly the gland and its duct. Thus prepared, we shall next study the mode 

 in which the blow is given, and the mechanism, through the agency of which the 

 poison is ejaculated. 



The heads of the true serpents are so constructed as to admit of a large amount 

 of movement in the component boues. Thus the zygomatic bones which support 

 the lower maxillary bones, are loosely articulated to the mastoid bone, which is 

 itself so mobile as to permit of the greatest possible expansion of the throat. 

 Anteriorly the superior maxillary bones are united, by ligaments only, to the inter- 

 maxillaries, and the lower maxillary bones of each side are also so connected ante- 

 riorly as to permit of their being widely separated, and of one or the other side of 

 the inferior jaw being drawn down to some distance, without involving a corre- 

 sponding motion on the part of its fellow. Finally, the superior maxillary bones, 

 the pterygoid and palate bones admit of considerable movement, so that the 

 arches which they form can be widened or narrowed as circumstances may require. 



The mobility of these parts is essential to the motions which raise and depress 

 the fang, and to the deglutition of the large animals upon which the snakes are 

 accustomed to prey. 



The poison fang, when at rest, projects downwards and backwards into the 

 mouth of the serpent. It is firmly anchylosed in the alveolar process, which 

 crowns the summit of the shortened upper maxillary bone. Fig. 1, d, whose pecu- 

 liar brevity is characteristic of venomous snakes. The superior maxillary bone is 

 of a rather irregular triangular shape, abruptly cut off below to form the alveolar 

 socket. One fiice of this bone is smooth, and looks inwards and slightly forwards. 



