260 



IXTEODUCTION TO ZOOLOGY. 



venomous is nearly as four to one. This is contrary to popular 

 opinion, and it was especially so in the " olden time." Thus, 

 whenever Shakspeare mentions one of those animals, it is 

 alwa^'s as a creature to be shunned as hateful or venomous : — 



" He is a very serpent in my way ; 

 And wheresoe'or this foot of mine doth tread, 

 He lies before nie." — King John, Act iii. scene 3. 



The gigantic Boa-Constrictor belongs to those which are 

 not venomous. It kills its prey by the enormous compression 

 it exerts when coiled round the body ot its victim, which it 

 then proceeds to swallow entire. The teeth are sharp, point 

 backwards, and thus retain the food. And here comes into 

 use a curious and bountiful provision with which snakes are 



furnished. The lower jaw 

 is not united to the upper ; 

 it is hung to a long, stalk- 

 shaped bone, upon which 

 it is moveable (Fig. 224) ; 

 and this bone has also a 

 power of motion, being 

 attached to the skull by 

 muscles and ligaments. By 

 means of this apparatus, 

 which is common to all true Serpents, they can swallow ani- 

 mals larger than themselves. This being done they remain 



in a quiescent state until 

 digestion is completed, 

 and the calls of 

 again excite them 

 exertion. 



In addition to this 

 elaborate contrivance, the 

 venomous tribes are fur- 

 nished with poison-fangs, 

 " constituting perhaps the 

 most terrible weapons of attack met with in the animal crea- 

 tion" t (Fig. 225). They ai-e two in number, fixed to the 

 upper jaw, or, to use more precise language, one is fixed to 



♦ FiR. 225. — p, poison gland ; its duct terminates in the large moveaWe tooth or fang,/; 

 m, muscles which raise the lower jaw and compress the poison gland. 



f Jones's Outline of the Animal Kingdom. 



Fig. 224.— Skull of Rattle-snake. 



hunger 

 to 



Fig. 225. 



-Poison Apparatus of Rattle- 

 snake.* 



