232 THE BIOLOGY OF THE ANIMAL 



Endeavor to trace the course of the common 

 bile duct, which leads from the gall-bladder to 

 the duodenum. This may be done by squeezing 

 the gall-bladder, thus forcing some of its contents 

 into the duct. What is the relation of the pan- 

 creas to the common bile-duct ? Examine the in- 

 side of the duodenum for the opening of the gall- 

 bladder. 



Lying in the middle line, and to one side of 

 the large intestine, find a small red body, 



*. The spleen. — What is its shape? Size? To 

 what is it attached ? 



Cut the oesophagus across, as close as possible 

 to the mouth, and carefully remove all of the di- 

 gestive tract from the abdominal cavity by cut- 

 ting the mesentery, which holds the parts in 

 place. Uncoil the intestine in the same mannei^. 

 Leave the large intestine attached to the cloaca. 

 Do not disturb the other organs. Straighten the 

 whole alimentary canal and measure its length. 

 How many times longer than the body is it? 

 How far from the anterior end do the digestive 

 glands — liver and pancreas^pour their secretions 

 into the canal ? Note the pigmented membrane 

 or peritoneum which lines the body-cavity or 

 pleuro-peritoneal cavity. Note also that it is 

 this membrane which forms a sling in which the 

 stomach and other parts of the digestive system 

 are held. By what is this sling supported ? 

 Make a diagram of the entire alimentary canal. 



D. — The Respiratory System. 



Passing downward from the glottis find 

 a. The larynx. — What is its position with regard to 



