Page:Natural History, Reptiles.djvu/137

Rh on a peculiarity of structure no less singular, first noticed by Cuvier. That illustrious physiologist considers it a very interesting fact that a great number of the vertebræ of the tail in the common Lizards are divided in the middle in a vertical plane into two portions; and that these portions are separated with even more facility than two contiguous vertebræ at the point of articulation; and this for the simple reason that the articulation is complicated, formed of many irregularities of surface (apophyses), and strengthened by ligaments, while the adhesion of the two parts of each vertebra is retained only by the continuous periosteum (or membrane that invests the bone), and by the surrounding tendons. This structure he had observed besides in the Iguanæ and the Anoles, and is of opinion that it would be found in all the genera which, like those mentioned, are subject to the rupture of the tail. "Every one knows," adds this anatomist, "that the tail shoots out again after having been broken, but neither the skeleton nor its integuments are, in that case, the same as before the rupture. The scales of the skin are generally small, without ridges and without spines, though they may have had the contrary qualities in the original tail; and internally, instead of the numerous vertebræ, with all their apparatus of apophyses and ligaments, there is nothing but a long cartilaginous cone of one piece, which only presents annular wrinkles, numerous indeed, but scarcely at all elevated." We have some reasons for thinking, however, that in time the reproduced tail would assume at least the exterior appearance, if not the interior structure of the original member.