THE RABBIT. 245 



is thus left a mediastinal cavity, within which the heart 

 and its pericardium lie. The pleura lining the thorax 

 and covering the lung may be readily seen when lifted 

 with a needle point. 



The Digestive System. The organs of digestion have 

 been noted as far as the esophagus. The esophagus de- 

 scends straight through the thorax, perforating the dia- 

 phragm, and entering the stomach on its concave anterior 

 border. Note the shape and size of the stomach, the point 

 at which the esophagus meets it, and the point at which the 

 intestine springs from it. At the origin of the intestine 

 is the pylorus, an internal valvular fold which guards the 

 passage, and prevents the premature exit of the food. The 

 first part of the intestine is the duodenum, a narrow por- 

 tion extended along the right side of the abdominal cavity, 

 and folded upon itself, to form a long, narrow loop. Into 

 this part the ducts from the gall bladder and the pancreas 

 open. The gall bladder is situated under one of the five 

 lobes of the liver, and is of a dark-bluish color. Its duct 

 (usually appearing brownish in color) extends posteriorly 

 to open into the duodenum, not far from the pylorus. 

 The duct is about an inch and a half long. It may be 

 made very plain by squeezing the contents of the gall 

 bladder out into it. 



The pancreas is whitish in color, and diffuse in form. 

 It is a loosely aggregated mass, completely surrounded by 

 the duodenal loop. Its short white duct opens near the 

 middle of the distal half of the duodenum. 



The small intestine is the long posterior continuation of 

 the duodenum. It is of about uniform diameter, and is 

 looped up in numerous folds of the mesentery. 



The ccecum is the long lateral pouch into the end of 

 which the intestine opens. It is the most conspicuous 

 part of the digestive tract, on account of its ventral posi- 



