Branch Chordata loi 



XIII. — Digestive System. Study the aHmentary canal. 

 / Beginning at the mouth see the straight tube, the 

 oesophagus, extending backward to the enlarged crop, 

 and then continuing to the muscular walled gizzard. 

 Open this : what is inside .'' What is the chief use of 

 the gizzard ? Back of the gizzard see that the alimen- 

 tary tube continues as the duodenum, more or less curved 

 and looped. Within this loop see the pancreas — a 

 yellowish gland. Lift the pancreas and find where its 

 ducts enter the duodenum. At this time study also the 

 liver with its two large lobes, and find the greenish 

 gall-bladder between them. Directly under the gizzard 

 see the small, flattened, red spleen. The alimentary tube 

 continues backward from the duodenum as the small 

 intestine, much convoluted, until it enlarges in the 

 cloaca near the posterior end. Notice the coeca on the 

 small intestine. Make a sketch of the alimentary tube 

 and its connections. 



XIV. — Respiratory System. The cartilaginous trachea is 

 easily seen extending from the mouth to the thoracic 

 cavity, where it divides into the bronchi, one passing to 

 each lung. Inflate the lungs through a tube inserted 

 into the trachea through the glottis, where it opens into 

 the mouth. 



XV. — Reproductive System. If your specimen is a male, 

 the oval glandular testes will be readily seen in the 

 abdominal cavity after the alimentary system is re- 

 moved. Find a convoluted vas deferens running from 

 each' to the cloaca. If your specimen is a female, you 

 will see the glandular ovary. A single oviduct on the 

 left side of the body opens into the cloaca. Only a 

 vestige of the right oviduct remains. 



XVI. — Renal System. When all the abdominal viscera 



