POISONOUS SNAKES OF NORTH AMERICA. 373 



around this joint and inserts itself {¥) broadly upon tlie lower jaw. It 

 may easily be shown that a contraction of these muscles will produce a 

 tremendous pressure up(m the poison gland. It is also apparent that the 

 closing of the mouth does not necessarily affect the gland, as only the 

 posterior and middle temporals need be employed in the action, and 

 that the pressure exerted by the anterior temporal is voluntary, as well 

 as independent of the closing of the jaw. 



While thus the flow of poison is regulated by the pressure upon the 

 gland, there are additional safeguards against waste of the precious 

 fluid. Dr: Weir Mitchell has discovered tbat the visible thickening of 

 the poison duct anterior to the sudden turn under the eye is due to an 

 increase in the amount of the fibrous tissue of the walls, and not to any 

 widening of the canal. As he also found the walls of the duct at this 

 place to contain nonstriated muscular tissue, he concludes that the 

 enlargement is a real ring-muscle, or sphincter, w^hich by its contrac- 

 tion closes the duct, and he demonstrated the correctness of his con- 

 clusion by experiments. He found that when in the living and active 

 Kattlesuake the jaws were separated, and the fangs caught on the edge 

 of a cup and erected, it was usually very difficult to produce a flow of 

 venom against the will of the snake, even when the operator pressed 

 upon the glands, but that on the contrary it was easy to force the poison 

 out along the duct and through the fang, if the snake was dead or insen- 

 sible from chloroform. 



The whole poison apparatus has very appropriately been compared 

 to-a hypodermic bulb syringe, the needle, with its obliquely cut point 

 and slit-like outlet, representing the fangs, the bulb corresponding to 

 the poison glands, and the muscles of the hand which presses the bidb 

 performing the same task as the anterior temporal muscle. 



The nature of the poisonous fluid secreted by the gland in the pit 

 vipers seems to be almost as diagnostic as the apparatus itself. The 

 discussion of its properties is so closely connected with the question of 

 antidotes and remedies that a summary of the interesting results of 

 Drs. Mitchell and Eeichert's recent studies and discoveries in this field 

 will be reserved for (juotation in the closing chapter of this paper, and 

 I shall now devote some space to the action of the snake in utilizing 

 the formidable weapon which has been described. 



The action referred to is not a "bite" pure and simple, it is the com- 

 bination of a bite and a blow delivered with such lightning rapidity 

 tliat it is very difficult, if not impossible, for the unaided eye to follow 

 the various movements composing it and to record their occurrence in 

 the proper sequence. The testimony furnished by our eyes as to the 

 movements and sequence involved in an action as familiar and com- 

 paratively slow as that of a running horse was proven utterly false by 

 the instantaneous photographs, and it is very likely that there are simi- 

 lar surprises in store for us when some one shall have rigged up a "bat- 

 tery" of cameras and fixed the successive movements of the striking 



