2S ON THE PHYSIOGNOMY OF SERPENTS. 



that of the pairs of ribs, rarely exceed 300, and are never 

 below 100; the vertebrae of the tail, on the other hand, 

 are sometimes reduced to 5, whilst, in other serpents, they 

 are from 150 to 200. 



The conformation of the vertebra) varies equally in the 

 different species, though all are modelled on the same 

 tyi)e. We can always distinguish a central part, the 

 body, which is armed with apophyses more or less de- 

 veloped, and more or less numerous, according to the 

 region of the body, or the species. The body of the 

 vertebra is generally compact ; but in most tree-serpents 

 the longitudinal diameter of that part considerably ex- 

 ceeds its thickness, so that the bones of the trunk, relatively 

 to the length of these animals, are less numerous than in 

 other Ophidians. The vertebra) play pretty freely on 

 each other, by means of articulations, well defined, and 

 more numerous than in most other animals. The j^rin- 

 cipal junction, which is almost perpendicular to the axis of 

 the vertebra, is composed of a perfectly spherical condyle, 

 divided from the body of the vertebra by a stricture in the 

 form of a neck ; this condyle is secured in a hollow, 

 scooped out in the anterior part of the body of the next 

 vertebra ; hence results a species of articulation which 

 deserves the name of Enarthrosis in its most extensive 

 sense, if these movements were not restrained by the arti- 

 culations of the Ajpophyses of the vertebras. The spinous 

 processes, very broad and voluminous at their base, 

 unite behind with the articular apophyses which most 

 generally also replace the transverse processes ; at their 

 anterior face, on the contrary, the base of the spinous pro- 

 cesses is prolonged in a wide projection, which is lodged 

 in the cavity at the base of the preceding apophyses : the 

 points of union consist of two pairs of lateral articular 

 facets, inclined to the axis of the vertebra, and this is the 

 origin of the supernumerary articular planes in the Ophi- 

 dians. The planes of the articulating apophyses present 

 a flat surface, in a perfectly horizontal direction. It 

 follows from this description, that the movements of the 

 bodies of serpents can only be freely exercised in the 

 lateral and vertical directions, and yet the movements in 



