KEPTILES. 275 



in order to endow these tribes with the greatest possible 

 flexibility, the number of joints in their spinal column is even 

 greater than in the Eels. In the Rattle-snake (Crotalus, 

 Fig. 223) there are about two hundred; and above three 

 hundred have been counted 

 in the spine of the Viper 

 (Natrix tor quota).* Thus 

 furnished, they can glide 

 along with silence and 

 rapidity, climb trees, and 

 leap with considerable vi- 

 gour and agility. 



The number of Serpents, 

 like that of other reptiles* 

 increases towards the tor- 

 rid zone, while compara- 

 tively few are found in 

 cold regions. They do not 

 appear to advance so far 

 northwards as Frogs and 

 Lizards. 



" One of the most cu- 

 rious facts in the distribu- 

 tion of Serpents, viewed in relation to different parts of the 

 globe, is their total absence from the numerous isles of the 

 Pacific Ocean a phenomenon the more remarkable, since the 

 neighbouring isles forming the great Indian Archipelago belong 

 to those regions of the earth most abounding in Serpents. 

 Another interesting fact is, that the Serpents, and indeed all 

 the reptiles of America, are specifically different from those of 

 the Old World; while, on the other hand, a great many birds 

 and several mammiferous animals of North America are pre- 

 cisely the same as those of Europe and a great part of Asia."t 



Some Serpents live amid the foliage of trees, some inhabit 

 fresh waters, some poisonous tribes live in the seas of tropical 

 Asia and New Holland, but by far the greater number are 

 terrestrial. According to Schlegel, there are at present 265 

 known species, and of these only 58 are venomous; so that 

 the proportion of the harmless ophidians to those which are 



* Koget's Bridgewater Treatise, vol. i. p. 450. 



f Schlegel, " Essai sur la Distribution Geographique des Opliidiens," 

 as abridged in Berghaiis, Physical Atlas. 



Fig. 223. RATTLE-SNAKE. 



