LECTURE VII. 35 



the general pattern or disposition of the colours is 

 perhaps a more certain criterion, though confessed 

 to be liable to alteration. 



One of the most singular properties of the 

 Serpent tribe is that of casting their skin from 

 time to time. When this operation takes place, 

 so complete is the spoil or cast-skin that even the 

 external coat of the eyes themselves makes a part 

 of it. The distinction of Serpents into poisonous 

 and innoxious can only be known by an accurate 

 inspection of the teeth; the fangs or poisonous 

 teeth being always of a tubular structure, and fur- 

 nished with a small hole or slit near the tip : they 

 are rooted into a particular bone, so jointed to 

 the remainder of the jaw on each side, as to 

 permit the fangs or poisoning teeth to be raised 

 or depressed at the pleasure of the animal. Above 

 the root of each is a glandular reservoir of poison, 

 which in the act of biting is pressed into the 

 tube of the tooth, and discharged into the wound 

 through the hole near the tip. The fangs are ge- 

 nerally single on each side ; sometimes double or 

 treble, and in general there are small or young 

 fangs situated at the base of the larger ones, ready 

 to grow up and supply their place when lost by 



