Because they originated in the ringed snake, which, even in Europe, has been found ten feet in length and upwards. Its colour is steel-grey, wherefore the dragon is often so coloured.
Because of the poison-teeth, which are placed on the anterior edge of the upper jaw, with the corresponding increase in the size of the latter; while, in the harmless serpents, the whole of the outer edge of the upper jaw is furnished with teeth, even to the very back part. - From the German.
Among the other characters of distinction, are the broader and heart-shaped head of the venomous, with small flat scales, instead of a single plate; the tail-shaped ridge on the back; and the shorter tail, which measures less than one-fifth of the animal. - Dr. Gray, in Philos. Transac.
The number of known venomous species, compared to those which are not so, is reckoned as one to six.
Because they contain a tubular cavity from their base (where is the poison-bag) passing through a tooth on its convex side, to the apex, where it ends in a narrow slit. When the serpent bites an animal, the poison flows from the bag through this slit, into the bottom of the wound, where to most advantage it can produce its deleterious effects. The properties of the poison continue even after it has been dried. If instilled into the wound, in any quantity, and it enters any of the larger vessels, death speedily follows. The virulence of the poison depends not only on the species of serpent, but on its condition at the time, and the habit of body of the animal which has received the bite.
Because, when irritated, the skin on the neck is expanded and drawn forwards, and appears behind the head as a kind of hood. This motion is produced by the cuticular muscles of the neck, aided by the moveable ribs.
Because they rub their hands, previously to taking hold of the snake, with an antidote composed of pounded herbs, the virtue of which is such, that they hold with the naked hand, and provoke fearlessly, the deadly cobra di capello. The secret is not unknown in China; and the cobra, in common with other serpents of a similar nature, are often exhibited in Canton.
Because vipers bring forth their young alive, whereas, snakes hatch their young from eggs, in dunghills, etc.