14 



VENOMS 



sufficient to retain the prey and to cause it to pass from front to 

 rear towards the oesophagus, by a series of alternate antero-posterior 

 movements and analogous lateral ones. By means of these move- 

 ments, which are participated in by the upper and lower maxillary 

 bones, the palatines, mandibles or inter-maxillaries, and the ptery- 

 goids, the animal in a manner draws itself over its prey like a 

 glove, since the arrangement of its dentition does not admit of 

 mastication. 



Fig. 13. — Arrangement op the Scales of the Head in one of 

 THE Non-poisonous Coluhrida, (Ptijas mucosiis). (After Sir Joseph Fayrer. ) 



a, Rostral scale; b, anterior frontals ; b', posterior frontals ; c, vertical; d, occipi- 

 tals ; E, supra-ciliaries ; f, temporals; l, m, nasals; n, loreals, or frenals ; o, anterior 

 oculars, or prte-orbitals ; p, posterior oculars, or post-orbitals ; q, supra-labials ; G, 

 median infra-labial ; h h, lateral infra-labials ; i k, mentals. 



The enormous extensile power of the mouth and oesophagus 

 thus enables snakes to swallow animals, the size of which is several 

 times in excess of their own diameter. 



Deglutition is slow and painful, but the gastric and intestinal 

 juices are so speedy m action, that the digestion of the most 



