THE HUMAN BODY. 203 



parts beneath. The outside of the skin is in itself 

 insensible, but it is so thin that we feel through it 

 The importance of the skin as a defence against 

 pain, is soon known when a portion is removed by 

 a blister or by any other means ; we cannot then 

 bear any thing to come near the part; even the 

 very air gives us an uneasy feeling. 



All the parts of our body are held together by 

 a fine membrane or web ; called from its form the 

 cellular membrane ; as it is made up of a number 

 of very small cells. This makes parts play easily 

 one over another, and lets them distend or swell 

 out, without doing injury. It is also through this 

 that vessels and nerves pass from one part to 

 another. 



Questions. 



Mention some of the operations constantly going on 

 within us. 



Are we sensible of these operations ? 



What kinds of fluids are carrying backwards and forwards 

 in our vessels "? 



How often does the heart act in a minute ] 



How many times are the lungs filled and emptied in an 

 hour? 



Of what are our bodies composed ? 



Are the solids or fluids most abundant ? 



What is remarkable about our organs 1 



What parts are called voluntary, and why ? 



What parts act without our knowledge or will ? 



Of what use is the skin, and how may we know this 1 



How arc the different parts of the body connected together ? 



