A TURTLE 139 



squeezed into this duct from the gall bladder. Note the pancreas, 

 a pinkish organ which extends along the duodenum. 

 Exercise 10. Draw the dorsal aspect of the liver, together with the 

 stomach, duodenum, and pancreas. 



Cut the intestine loose from its mesentery as far forward as 

 the bile duct, which must be preserved. Do this by lifting the 

 intestine up with forceps and cutting the mesentery where this 

 joins it. Note the great length of the small intestine. The large 

 intestine contains three divisions,— the caecum, a short, thick, blind 

 gut at its forward end, and the colon and the rectum, which form 

 the greater part of it. The rectum is sometimes wider than the 

 colon and is continuous posteriorly with the cloaca. Lying near 

 the colon in the mesentery is the dark-red spleen ; it is not a part 

 of this system. 



Free the liver from its connection with the lungs and other or- 

 gans which lie dorsal to it, but be careful not to cut the bile duct. 

 Cut the mesentery which joins the stomach with the liver. Ob- 

 serve the cardiac end of the stomach and the oesophagus. Follow 

 the latter to the head. Stretch out the digestive tract on the dis- 

 secting board, with the liver and pancreas still attached to it. 



Exercise 11. Make a drawing of the entire digestive tract, showing 

 the relative lengths of the different divisions ; carefully label all. 



Cut the rectum and the oesophagus and remove the digestive 

 tract. Slit open the rectum and the colon, also the stomach and 

 the duodenum, and observe the folds of the mucous membrane. 



The Respiratory System. The large lungs have already been 

 noticed lying against the inner surface of the carapace. Observe 

 their exact extent. From each lung a tube called the bronchus 

 passes ventrally and anteriorly, the two bronchi joining to form 

 the trachea, or windpipe. Note the cartilaginous rings which pre- 

 vent the bronchi and the trachea from collapsing. Trace the 

 trachea forward to the glottis, its opening into the pharynx. 



The forward end of the trachea is formed by the larynx ; this 

 contains a number of cartilages and has for its principal function 

 the control of the passage of air into and out of the lungs. In the 

 turtle it is composed of a large posterior cartilaginous ring, the 



