312 
NATURAL HISTORY 
Sir Everand Home and other authors, act upon the ribs 
in serpents to assist their progressive motion on land. 
Viscera . — The only part of the viscera, which the li- 
mited openings permitted us to examine, were a portion 
of the lung and oesophagus, with the mesentery and blood 
vessels, also a small part of the stomach. The lung was 
a long cellular and tubular viscus, as in other serpents, 
but with this remarkable peculiarity. It was succes- 
sively dilated and contracted so as to adapt itself to the ! 
cavities formed by the undulations of the spine. The 
oesophagus was also unequal, but without relation to the 
cavities of the spine, not being in contact with it. In 
the stomach was found a mass of scales, also the tail and 
part of the skin of a serpent of a different species, hav- 
ing all the scales carinate. 
In regard to the use or final cause of the curvatures 
in the back-bone, which give so peculiar a character to 
this animal; it is obvious that two important ends are 
effected by it. These are an increase of flexibility and 
an increase of strength in vertical motions . 
1. The flexibility is increased, because in any given 
length of body, there will be more joints in a crooked, 
than there would be in a straight spine, composed of 
vertebrae of the same dimensions. 
2. The strength in vertical motions is increased, since 
the fulcrum formed by the highest articulation is more 
remote from the power applied by the lateral muscles, 
and the fulcrum formed by the lowest articulation is also 
more remote from the power applied by the dorsal mus- 
cles, than they would be if the spine pursued a straight 
and intermediate course. 
The dorsal muscles, however, being bound down by 
an aponeurosis, so as to pursue nearly the course of the 
spine, are nearer their fulcrum and have less of this ad- 
vantage than the lateral muscles, which are farther from 
their fulcrum; so that the greatest power is probably that 
which is exerted in the forward flexion or extension of 
the body. This power is the one which would be most 
useful to the animal in swimming at the surface of the 
water with a motion in any degree vertical. 
