GENERAL CHARACTERS OP REPTILES. 533 



It is always widely dilated ; but it is among Serpents, that it is 

 susceptible of being extended in the most remarkable manner ; 

 hence, these Reptiles can swallow animals larger than themselves. 

 The two branches of the lower jaw are not united ; and the sort 

 of peduncle or stalk which supports them (the tympanic bone, , 



Fig. 310,) is not only movable 

 itself, but is also suspended to 

 another portion of the tem- 

 poral bone, called the mastoid 

 lone (ma), which is likewise 

 distinct from the cranium (c), 

 and is attached to it only by 

 ligaments and muscles. The 

 FIG. 3io.-SRu L L OF RATTLE-SNAKE. branches of the upper jaw (m), 



c, cranium ; ma, mastoid bone ; t, tympanic are Only fixed to the inter- 

 bone : m upper jaw ; mi, lower jaw ; n, nasal M , , IT 



bones; p and pi, pteregoid and palatine maxillary bone by ligaments, 

 bones. which permit them to be more 



or less separated ; and the palatine arches (p) also participate 

 in this mobility. This peculiarity of structure corresponds 

 with the habits of these essentially carnivorous Reptiles. 

 They can support abstinence for a long time ; but generally, 

 when an occasion presents. itself, they take into their stomach 

 such a great mass of nutriment, that, during their digestion 

 of it, they remain in a state of torpidity more or less pro- 

 found. They do not masticate their food, but their mouth 

 is armed with hooked teeth, adapted to retain their prey 

 within it. 



474. Several Serpents, such as the Viper, the Asp, the Cro- 

 talus, or Rattle Snak (Fig. 331), and the Trigonocephalus, 

 present still more remarkable peculiarities of structure ; for 

 nature has endowed them with a venomous apparatus, by the 

 aid of which they can immediately kill, as soon as they bite 

 them, the animals upon which they intend to feed. Their poison 

 is secreted by glands, which greatly resemble the salivary ; and 

 which pour this liquid out by an excretory duct, in the neigh- 

 bourhood of one of the maxillary teeth of the upper jaw, whose 

 form is modified, in order to adapt it to the uses for which it is 



