10 



THE FROG 



used will be explained. In one apparatus, starch paste is in the inner 

 tube; in another, a sugar solution is in the inner tube. Do tests show 

 that these substances pass through the membranes? If both starch 

 paste and saliva are placed in the inner tube what happens? Record 

 the results and conclusions of the experiment in the form of a table 



muscle laye. 



mesenierij 



artery 

 - lymph iressel 



lymphaiics 

 submucosa 



-arteru 



-mucous membrane. 



lymphatic, 

 capillaries 



~~ — villus- " ' 



Fig. 13. — Blood and lymph vessels in the wall of the digestive tract; dia- 

 grammatic. A, a portion of the entire wall. B, capillaries in a villus of Ihe 

 intestine. C, lymphatic in a villus of the intestine. Arrows indicate direction 



of circulation. 



such as the one shown in Fig. 14. Make diagrams to show the parallel 

 between the apparatus used and the structure of the digestive tract. 

 What facts can be cited against the physical process of osmosis as 

 a complete explanation of the absorption of food in the living animal? 



