184 VERTEBRATES 



brane? What is it called? Observe the blood vessels in 

 it. Where are they smallest? Where largest? Where do 

 they carry the blood? These vessels unite in the portal 

 vein, which carries the absorbed food to the liver, from 

 whence it goes to the heart. Follow the alimentary canal 

 down to the cloaca, the enlargement at the anal portion. In 

 front of the cloaca is the rectum, which extends from the 

 small rectal glands to the cloaca, and in front of this extend- 

 ing to the duodenum is the small intestine. 



Place the parts of the digestive system that have been 

 studied so that they can be seen and make a diagrammatic 

 drawing showing all in their proper relation. 



(9) With a small cord tie the small intestine in front of 

 the rectum in two places and sever the canal between them. 

 Remove the alimentary canal. Cut oS the gizzard and ex- 

 amine the arrangement of the muscles on the outside. The 

 hard, light-colored portion acts as a cartilage for the at- 

 tachment of muscles. How many muscles can you find 

 on the outside? Cut the gizzard across at right angles 

 to the edges. Note its internal structure. What do you find 

 in it? How does the pigeon masticate its food? Have 

 you found a similar contrivance in any other animal? 



Draw cross section (Xi)- 



(10) The reproductive organs are found in the dorsal 

 side. The male is distinguished by two oval bodies, the 

 testes, and the female by an ovary which often has eggs 

 of different sizes in it. Sometimes these show all the 

 different stages of development. These reproductive or- 

 gans are connected with the cloaca by a duct, the oviduct 

 in the female, and the vas deferens in the male. 



Draw reproductive organs (Xi)- 



