96 VERTEBRATE ZOOLOGY 



the base of the hind legs, the large urinary bladder will be seen ; 

 if it is not found readily, insert the blowpipe in the anus and 

 inflate the bladder. Several elongated yellowish bodies may be 

 seen here projecting from between the other organs; they are 

 called the fat bodies. 



The body cavity is divided into two compartments, the abdom- 

 inal cavity and the pericardial cavity. The former is by far the 

 larger of the two and contains the liver, intestine, and most of 

 the other viscera ; it is lined by a membrane called the peritoneum. 

 The pericardial cavity is small, being only large enough to con- 

 tain the heart and the base of the great blood vessels ; it is formed 

 by a membrane called the pericardium. Note that the organs in 

 the abdominal cavity are attached to the walls or to each other by 

 thin membranes. These are the mesenteries. They are folds of 

 the peritoneum and have come into existence as a result of the 

 growth of these organs in the body cavity. The peritoneum is a 

 closed sac with extensive mesenterial folds extending into it, within 

 which lie the various organs. 



Exercise 5. Draw an enlarged outline of the animal, and in it the 

 internal organs as they lie in the body cavity before they have 

 been disturbed ; label all carefully. 



The Digestive System. This system consists of the mouth, 

 pharynx, oesophagus, stomach, intestine, cloaca, liver, and pancreas. 



The mouth and pharynx have already been studied. Without 

 cutting anything, press the liver to the animal's right and fully 

 expose the stomach. It will be seen to be a large, curved organ,— 

 the anterior or cardiac end being near the left lung at the side of 

 the heart, and the posterior or pyloric end being near the median 

 line of the body. The oesophagus is a short tube, not quite so 

 wide as the stomach, which joins the cardiac end of that organ 

 with the pharynx. 



From the pyloric end of the stomach, which is marked by 

 a constriction, the intestine proceeds with many turns to the 

 hinder part of the body. It is composed of two divisions,— the 

 small intestine and the large intestine, or rectum. The small intes- 

 tine forms the greater part of it. Its anterior portion, the duode- 



