VERTEBKATA. 83 



F. The Hind Limbs. 



1. Observe the division of the hind limb into the thigh, 



(the proximal segment) the shank and the foot. 



2. How many toes are there on each foot ? 



3. What is the advantage in having the limb attached 



so near the end of the body ? 



4. Compare with a skeleton of the frog and observe 



that the attachment of the limb to the body is 

 really brought forward as far as the " hump " by 

 another bone (pelvic girdle). 

 What is the advantage of having the point of at- 

 tachment of the limb to the body so near the 

 middle of the body ? 



5. What is the resting position of the hind limb ? 

 Why? 



6. How is the limb adapted to jumping? 



7. How is the limb adapted to swimming ? 



8. In what manner are the limbs used in jumping and 



swimming ? 

 Why cannot the frog jump backward ? 



9. Make an outline drawing of the limb extended ? 



G. Respiration. 



1. The Lungs. (Examine a frog dissected to show the 

 lungs.) 

 a. Compare the size and appearance of inflated and 



uninflated lungs. Sketch. 

 h. Are the lungs spongy throughout or are they 



hollow ? (Dem.) 

 e. Observe that each lung narrows into a short 



tube (bronchus), which connects it with the 



trachea. 

 d. Is there a diaphragm ? The diaphragm is a mem- 



