148 ANSWERS TO PRACTICAL QUESTIONS 



9. Why can we raise a heavier iveight with our hand 

 when liftinrj with the elbow than from the shoulder? 



Because we bring the fulcrum .nearer the power. In the 

 former case it is at the elbow ; in the latter, at the shoulder. 



10. Wliat class of lever do ^ve employ when ive are hop- 

 ping, the thigh-bone being bent up toward the body and 

 not used ? 



In this case the fulcrum is at the hip-joint. The power 

 (which may be assumed to be furnished by the rectus muscle* 

 of the front of the thigh) acts upon the knee-cap ; and the po- 

 sition of the weight is represented by that of the center of 

 gravity of the thigh and leg, which will lie somewhere between 

 the end of the knee and the hip. HUXLEY. 



11. Describe the motions of the bones when we are 

 using a gimlet. 



The radius rolls on the ulna at the elbow, while the ulna 

 rolls on the radius at the wrist. The two combined produce a 

 free, rotary motion. 



12. Wliy do we tire when we stand erect ? 



(See Physiology, p. 37.) 



Because so large a number of muscles must be in constant 

 action to maintain this position. 



13. Why does it rest us to change our work ? 



"We thereby bring into use a new set of muscles. 



14. !V7iy and when is dancing a beneficial exercise? 



When dancing is performed out-of-doors, or in a well-ven- 

 tilated room, and at proper hours, it is doubtless a beneficial 

 exercise, since it employs the muscles and pleasantly occupies 

 the mind. Late at night, in a heated room, with thin clothing 

 and exciting surroundings, it is simply a dangerous dissipation, 

 ruinous to the health, alike of body and soul. 



* This muscle is attached above to the haunch-bone or ileum, and be- 

 low to the knee-cap. The latter bone is connected by a strong ligament 

 with the tWa. 



