I20 A GUIDE FOR THE STUDY OF ANIMALS 



8. What holds the internal organs in place, and from 

 what are they suspended ? 



9. The spleen is called a " ductless gland." Give its 

 function, and explain why a duct is not necessary to it. 



10. Since the frog swallows its food alive and entire, 

 what work must the stomach do ? What digestive organs 

 would be absent from the mouth, or else poorly developed ? 



1 1 . Since the frog is carnivorous, what digestive ferments 

 are probably present, and what ones absent from the ali- 

 mentary canal ? 



12. Fat bodies are largest in the fall, and are rarely 

 found in the spring. How can you account for this .'' 



13. When through with the general study of the alimentary canal, 

 you may open the stomach by cutting it lengthwise. Describe the 

 character of the stomach lining as to folds and villi, stating the advantage 

 of each being present and the reason for the direction of the folds. Tell 

 how the food is propelled onward through the alimentary canal. Give 

 the scientific name for this action. 



Suggested drawings. 



a. The viscera (internal organs) undisturbed. 



b. The alimentary canal extended. 



c. The excretory system. 



The Organs of Circulation and Respiration of the Frog 



Materials. 



The materials used in this exercise are the same as those 

 used in the preceding exercise. 



Observations. 

 The pupil should identify the following structures : — 

 Pericardium, a membrane that surrounds the heart and, 

 in the case of the frog, separates the body cavity into two 

 portions, the abdomen and the pericardial chamber. 



