Page:Natural History, Reptiles.djvu/162

154 hissing, and filled the room with such nauseous effluvia, as rendered it hardly supportable.”

The eggs of serpents are enclosed in a calcareous covering, which is not hard and shelly, but tough, somewhat resembling kid-leather, or wet parchment. They are often numerous, and are deposited together, and connected by a sort of glutinous matter. Holes in the earth, in dunghills, or in heaps of decaying vegetable matter, are situations frequently chosen for their reception; and here they are left to be hatched by the heat of the weather, or by that which is developed in the putrefactive fermentation of the surrounding mass. The venomous species, as far as we are acquainted with their habits, are ovo-viviparous, the membrane of the egg being ruptured either before or during parturition.

We have said that the instruments of progressive motion in the Serpent tribes are the multitudinous ribs. The vertebræ of the spine admit of excessive flexibility, and the ribs are jointed upon them in a manner which allows the latter an extent of motion unusually great. The mode in which a Serpent proceeds will be understood from the following observations, the reader bearing in mind that the whole under surface of the body is shod, as it were, with broad plates, or scuta, the hinder margins of which are free. “When the Snake,” says Sir Everard Home, “begins to put itself in motion, the ribs of the opposite sides are drawn apart from each other, and the small, cartilages at the end of them are bent upon the upper surfaces of the abdominal scuta, on which the ends of the ribs rest; and