14- ANSWEMS TO PRACTICAL QUESTIONS 



ology. " So (admitting fable to be fact), when the farmer, 

 in answer to his petition for assistance, was commanded 

 by Hercules to exert himself to raise his wagon from the 

 pit, he placed his shoulder against the wheel, and draw- 

 ing his body up into a crouching attitude, whereby all his 

 joints were flexed, and making his feet the fixed points, 

 by a powerful muscular effort, he straightened the toggle- 

 joints of his limbs, and the wheel was raised from its bed 

 of miry clay. His horses at the same moment extending 

 their joints, the heavily laden wagon was carried beyond 

 the reach of further detention." GRISCOM. 



8. What class of lever is the foot when we walk ? 





 In the first stage it is clearly the second class. (See 



Physiology, page 47, Fig. 18.) The fulcrum is the ground 

 on which the toes rest ; the power is applied by the gas- 

 trocnemius muscle (see Fig. 14, k] to the heel ; the 

 resistance is so much of the weight of the body as is 

 borne by the ankle-joint of the foot, which of course lies 

 between the heel and the toes. 



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

 when lifting 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. What class of lever do we employ when we are hop- 

 ping, the thigh-bone being bend 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 



