314 SERPENTS. 



vious characters. The colour is indeed often va- 

 riable, but the pattern, or general distribution of 

 markings in each species, appears to be more con- 

 stant : the relative size of the head, the length of 

 the body and tail, the size, smoothness, or rough- 

 ness of the scales, as well as their shape in dif- 

 ferent parts of the animal, ot*ten afford pretty cer- 

 tain specific marks. 



The distinction of Serpents into poisonous and 

 innoxious can only be known by an accurate exa- 

 mination of their teeth ; the fangs or poisoning 

 teeth being always of a tubular structure, and 

 calculated for the conveyance or injection of the 

 poisonous fluid from a peculiar reservoir commu- 

 nicating with the fang on each side of the head : 

 the fangs are always situated in the anterior and 

 exterior part of the upper jaw, and are generally, 

 but not always, of much larger size than the other 

 teeth ; they are also frequently accompanied by 

 some smaller or subsidiary fangs, apparently de- 

 stined to supply the principal ones when lost either 

 by age or accident. The fangs are situated in a 

 peculiar bone, so articulated with the rest of the 

 jaw as to elevate or depress them at the pleasure 

 of the animal: in a quiescent state they are recum- 

 bent, with their points directed inwards or back- 

 wards ; but when the animal is inclined to use them 

 as weapons of offence, their position is altered by 

 the peculiar mechanism of the above-mentioned 

 bone in which they are rooted, and they become 

 almost perpendicular. 



