238 M. Dumeril on the General Movements of Serpents. 
small bones ; it is the most solid portion, the centre on which they move. 
It follows from the particular mode of their junction with each other, 
hitherto observed only among these animals, that every vertebra of an 
ophidian is scooped out in the anterior part in the form of a concave, re- 
gular, hemispherical depression, cut somewhat obliquely at its cireum- 
ference ; and that this same central part of the vertebra bears behind a 
kind of convex head, regularly rounded, corresponding in its curvature 
to the concavity which is to receive and enclose it. This head, or salient 
bone, is itself supported by a kind of neck or small constricted portion. 
The two articular facettes which thus correspond in their inverse curva- 
tures, are covered with a true cartilaginous incrustation, and protected 
by a synovial membrane covering a fibrous capsule, so as to admit of 
movements similar to those which mechanicians designate by the name 
of aknee’d joint. It is an enclosed ball, which can turn upon itself in all 
directions. 
It is necessary to keep this arrangement in mind, because the diffe- 
rences presented by the numerous salient points projecting from these 
vertebrae on the back, belly, and even laterally, limit, check, and facili- 
tate, by their extent, inclination, and curvatures, the variety of the move- 
ments of the whole body. They indicate in the different races of ser- 
pents the particular mobility of each piece in the whole skeleton, and 
this examination enables us to comprehend beforehand, and explains the 
numerous modifications which have been required for each special mode 
of progression. It enables us, in fact, to understand the mechanism of 
the movements of ophidians on the earth, both at its surface and in deep 
sands, their mode of clasping and twisting themselves round the branches 
and trunks of trees, and continuing suspended there for whole days ; and 
lastly, the means they employ to move on the surface and in the depths 
of waters. 
What first strikes our notice in this series of vertebral bones in ser- 
pents, is their resemblance and uniformity in the two regions of the trunk 
and tail, insomuch that it would be impossible for the most skilful 
zootomist to assign its exact rank in the series to each of the pieces, with 
the exception perhaps of the hinder vertebree, which often diminish gra- 
dually in size. They are the links of a chain so closely resembling each 
other, that they seem successively to have come out of the same matrix 
in which they had received their solid forms and impressions, to enter 
into a concatenation so perfect and regular. 
These vertebre are generally short, broad, and of a compact tissue, 
consequently very solid and capable of great resistance, so that it is more 
easy, in violently striking the backbone of a serpent, to separate the 
pieces than to fracture them. Their number varies much according to 
the genera and species. It is observed that the number is not always the 
same in the regions ; it amounts sometimes to 400 in some Boas and 
Pythons. It is rarely below a hundred ; serpents, therefore, have in 
