28 
ON THE PHYSIOONOMY OF SEEPENTS. 
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 vertebrae varies equally in the 
different species, though all are modelled on the same 
type. 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 vertebras play pretty freely on 
each other, by means of articulations, well defined, and 
more numerous than in most other animals. The prin- 
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 JEnarthrosis in its most extensive 
sense, if these movements were not restrained by the arti- 
culations of the Apophyses of the vertebrae. 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 
