128 A GUIDE FOR THE STUDY OF ANIMALS 



5. How many vertebrae are there in the spinal column ? 

 What advantage can you see in having the column com- 

 posed of many small vertebrae instead of a few large ones ? 

 Enumerate those having a special form or structure, and 

 state the use of each. 



6. On the vertebrae notice any irregularities, promi- 

 nences, or roughenings. For what are such bones better 

 adapted than smooth bones would be ? 



7. How is the frog's humping permitted? How are 

 the urostyle and the pelvis connected, if at all ? Has this 

 any effect on motion ? (See living frog.) 



8. In parallel columns, keeping corresponding parts in 

 a line, tabulate the bones of the fore and hind limbs. 



g. Statte how extra length has been attained in the hind 

 leg, and give the purpose or the result of this lengthening. 



10. In the forearm notice the fusing of the radius and 

 ulna. How would these parts act in rotating the hand, as 

 compared with your own, where they are free .'' Compare 

 also the tibia and fibula. Where in the frog's leg is turn- 

 ing made possible by the use of parallel bones ? 



11. Compare the frog's hand and foot as to number of 

 fingers and toes ; as to length and spread. Have any fingers 

 or toes only two phalanges ? 



12. How would an inner skeleton affect the growth and 

 the size of an animal, as compared with an outer skeleton, 

 like the clam's ? 



13. How would the lack of an outer skeleton influence 

 sensitiveness, activity, and intelligence ? 



Suggested drawings. 



a. The skull and trunk, with appendages of one side. 



b. Each set of bones separately, as the skull, the col- 

 umn, etc. 



