96 
STRUCTURE OF SERPENTS. 
their ribs are also very numerous ; and they are able to crawl 
upon the points of these, using them almost as Centipedes do 
their legs (fig. 42). But in general the movement of their 
Fig. 34.— Anatomy oe a Coluber 
bodies is accomplished by their being drawn-up into folds, 
and then straightened so as to project the head. The pro¬ 
longed form of the body in Serpents occasions a curious 
variation in the arrangement of the principal organs, which 
is shown in the accompanying figure. The oesophagus or 
