54 ON THE PIIYSIOGNOJilY OF SERPENTS. 



(!upies the other half of tlie length of the trunk ; plaited 

 throughout almost its Avhole extent, and generally of cf[ual 

 width, and rather narrow, the intestinal canal merits 

 in its gi-eatest part, the name of small intestine; it is 

 only near the posterior region of tlie 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 contraetion, or by a 

 transverse fold, or by a valve more or less distinct, fol- 

 lowed at some distjmce by one or more similar divisions. 

 Some species of the genera Tortrix, Homalopsis, and 

 others, have a small ccecum 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 ])rolonged 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 theh' 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 



