ANATOMY OF THE OAT. 



The abdominal cavity contains the principal reproduc- 

 tive, excretory, and digestive organs. The oesophagus ter- 

 minates in the stomach almost immediately below the dia- 

 phragm. The stomach (St) occupies a transverse position, 

 its larger (cardiac) end, which receives the oasophagus, lying 

 on the left, the smaller (pyloric) end on the right. The 

 pylorus has a sphincter muscle which can completely close 

 the orifice. The stomach is followed by the long intestines 

 (In), most of which have been removed, leaving a short 

 piece in front. The posterior portion of the intestine is 

 somewhat dilated, is called the colon, and passes into 

 the wide terminal rectum (Rec). The whole abdominal 

 portion of the intestinal canal is suspended from the me- 

 dian dorsal line by a thin membrane, the mesentery, which 

 forms several folds, the most striking of which is the omen- 

 turn or grand epiploon (Om.). This fold, when in situ, 

 hangs down from the stomach like an apron, covering over 

 the intestines ventrally. Upon opening the walls of the 

 abdomen, it is the first structure met with. It usually con- 

 tains a great deal of fat. Its principal function is supposed 

 to be to prevent the loss of heat. The omentum is present in 

 all mammals, but is least developed in Cetaceans, being most 

 prominent in Carnivora and ruminants. Connected with 

 the intestine are two glands, the liver (Li) and pancreas. 

 The liver is large and lies directly underneath the diaphragm. 

 The elongated light-colored pancreas lies alongside the front 

 end of the intestine (In), or so-called duodenum ; in its 

 microscopic structure it resembles the salivary glands. The 

 spleen is closely connected with the stomach, and is of an 

 elongated shape, as in the majority of the Mammalia mono- 

 delphia. 



The kidneys (Ki) are large and oval, and lie on either 

 side of the vertebral column ; the aorta passes between 

 them, giving off a renal branch to each gland. A deli- 

 cate ureter ( Urt) passes from each kidney obliquely across 

 the rectum to the large flask-shaped bladder (Bl). A 

 urethra (Ur) arises from the bladder posteriorly and 



