I70 PHYLUM CHORD ATA 



Make a transverse incision in each flap of the body wall. Turn 

 the flaps to the side and pin them down, exposing fully the 

 internal organs. 



In addition to the organs already mentioned one or both lungs 

 may be seen. They are usually shriveled, saclike organs which 

 lie at the forward end of the abdominal cavity, concealed by the 

 liver. If either is fuH of air, it should be punctured and made to 

 collapse. At the hinder end of the abdominal cavity, between 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 project- 

 ing from between the other organs ; they are called the fat bodies. 



The abdominal cavity is lined by a membrane called the perito- 

 neum. Note that the organs in it are attached to the walls or to 

 each other by thin membranes ; these are the mesenteries ; they 

 are folds of the peritoneum. 



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 as 

 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 con- 

 striction, 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 intestine 

 forms the greater part of it ; its anterior portion, the duodenum, 

 is bent forward so as to lie parallel with the stomach, and be- 



