QUESTIONS 191 



several layers of cells. 'Nails and the hair grow from the 

 outer layers. The sense of touch is in the skin. 



QUESTIONS 



How does the skeleton of man compare with the skeleton of the cray- 

 fish? How do bones grow? Why do they grow? When is there the 

 most cartilage in our skeletons ? How many kinds of muscle are there? 

 What is the work of each ? What is the work of the skin ? Of what is 

 the skin composed ? 



