54 
ON THE EHYSIOONOMY OF SEKPENTS. 
cupies the other half of the length of the trunk ; plaited 
throughout almost its whole extent, and generally of equal 
width, and rather narrow, the intestinal canal merits 
in its greatest part, the name of small intestine; it is 
only near the posterior region of the trunk that it en- 
larges into a capacious cylinder of varying length, which 
represents the rectum. The separation of those two por- 
tions of the intestine is either by a contraction, or by a 
transverse fold, or by a valve more or less distinct, fol- 
lowed at some distance by one or more similar divisions. 
Some species of the genera Tortrix, Homalopsis, and 
others, have a small coecum near the entrance of the small 
intestine into the rectum. Another well-developed valve 
is formed at a little distance from the anus, and separates 
the rectum from the cloaca. This latter cavity is very 
spacious, and is often prolonged as a pouch below the 
valve ; it is always in this that we find the ducts of the 
urinary and generative organs terminate. As carnivor- 
ous animals the Ophidians have a short intestinal canal, 
relatively to the dimensions of their bodies ; we find, how- 
ever, in the different genera, very distinct modifications in 
this respect. The Boa, for example, has very capacious 
small intestines, but they are very short, and consequently 
convoluted. This canal becomes more developed in its 
longitudinal dimensions in the Elaps, in several of the 
genus Coluber, &c. In the greatest number of other Ophi- 
dians, especially in the Homalopsis, the convolutions are 
very numerous. 
The muscular tunic of the sides of the alimentary canal 
is in general little distinct : below the oesophagus it be- 
comes more sensible as we approach the spacious sac re- 
presenting the stomach: it is the same with the true 
intestines, in which the muscular tunic becomes stronger 
towards the rectum than in the small guts. The interior 
tunics of the alimentary canal are longitudinally convoluted. 
These folds become more numerous in the stomach where 
they are less regular, crossing each other in different direc- 
tions, and presenting very distinct ridges ; they disappear 
when those parts are distended with aliment. Similar 
folds or ridges are seen in the rectum. The mucous coat 
