ON THE DIGESTIVE ORGANS, AND THEIR APPENDAGES. 137 



a cuticular epithelium, as those of the Horse, the Rhinoceros, &c. ; and 

 some, again, as those of the Beaver, the Dormouse, &c., have a glandular 

 apparatus, in the cardiac portion, for the secretion of a mucous fluid. 



This singular gland is seen in the 

 accompanying sketch (fig. 137) 

 of a portion of the stomach of 

 the Beaver : the gland is partly 

 dissected, in order to shew its 

 conglomerate structure. Of the 

 ever-varying details presented 

 by the stomachs, both simple and 

 complicated, of the Mammalia, 

 a more detailed description will 

 be given, as each order, or fa- 



Cardiac gland or the stomach of Beaver. ^J^ CQmes under review . 



The commencement of the intestinal canal is termed the duodenum ; 

 and into this portion of the intestine two important secretions are poured 

 one, the bile, secreted by .the liver ; the other, the pancreatic juice, a 

 fluid closely resembling saliva, and secreted by the pancreas, a large 

 gland, which, spreading beneath the mesentery (to which it is at- 

 tached), extends from the spleen, encircled by the fold of the duo- 

 denum. The use of the bile, and of the pancreatic juice, is not well 

 understood ; the never-failing presence, however, of organs for their ela- 

 boration, proves their importance. In most animals there is, beneath 

 the liver, and attached to it, a sac, termed the gall-bladder, acting 

 as a reservoir for the bile ; but this is not universally the case. It 

 is wanting in the Rhinoceros, Elephant, Hyrax, Hippopotamus, Pec- 

 cary, and Tapir, but is present in the Hog : it is wanting in the 

 Horse and its congeners : it is absent in many of the Rodentia, as Geo- 

 rychus, Cricetus, Mus agrarius, minutus, decumanus, musculus, sylva- 

 ticus, rattus, &c. ; also, in Loncheres, in Histrix dorsata, Histrix pre- 

 hensilis, and in several of the Squirrels. Among the Ruminantia, it 

 is wanting in the Camels and the Deer; in the Giraffe it is gene- 

 rally absent, sometimes present ; it is found in the Oxen, Sheep, and 

 Antelopes. 



It may here be observed that, close to the cardiac portion of the 

 stomach, and connected with it by a fold of mesenteric membrane, lies the 

 spleen a large, flat body, differing much in shape in different animals, 

 and consisting of a tissue of tortuous blood-vessels : its use has, hitherto, 

 baffled investigation. 



The small intestines commence with the duodendum, and are some- 

 what artificially divided into duodenum, jejunum, and ilium : they are of 

 a muscular texture, lined, internally, with a highly vascular, delicate, vil- 



