358 ZOOLOGY. 



jaws admit of very great dilatation ; moreover, the branches 

 of the upper jaw (m) are attached to the intermaxillary bones 

 also by ligaments, and even the palatine arches partake of 

 the movement. Their teeth are intended only to seize their 

 prey, and after swallowing it they remain long in a state of 

 torpidity. 



464. Many serpents, such as the viper, the cobra, the 

 rattlesnake, and the trigonocephalus or brown viper of Caro- 

 lina, possess a dangerous venomous apparatus of an alarming 

 character. Certain glands, analogous to the salivary, secrete 

 this poison (Fig. 360) ; they are placed under the temporal 

 muscles, so as to be compressed by them when in action. They 

 communicate by a canal with a fang or poisoned tooth on either 

 side ; this is either grooved or perforated by a canal, the exit 

 of which is not at the point, but a little higher up, so as not 

 to interfere with the action of the point of the tooth. When 



Fig. 360.* 



the animal bites, the venom is by this means transfused into 

 the bottom of the wound. These teeth are fixed, but the 

 bones to which they are attached are moveable ; when not in 

 use they lie horizontally, with the palate,, encased in a sort of 

 sheath of mucous membrane. The poisonltself is neither acrid 

 nor burning to the taste, and it is harmless when swallowed ; 

 its terrible effects are felt only when mingled with the blood 

 in a wound, and they vary with the condition of the animal. 

 On some animals the poison of the viper has no effect, as on 

 leeches, slugs, the common snake, and the civet ; whilst it 



* Poison apparatus in the Kattlesnake : v, poison gland, with its duct 

 leading to the large poison fang (c) ; m, elevator muscles of the jaw, which 

 partly cover the gland, and may compress it; s, salivary glands on the edge 

 of the jaws ; n, the nostril, under which is the little cavity distinguishing 

 these serpents and the trigonocephali from vipers. 



