THE BODY.] PHYSIOLOGY. 



arteries together are called blood-vessels, and it 

 will be easy for you to make out that the larger ones 

 you see are really hollow tubes. Lastly, if you sepa- 

 rate the muscles still more, you will come upon the 

 hard bone in the middle of the leg, and if you look 

 closely you will find that many of the muscles are 

 fastened to this bone. 



Now try to put back everything in its place, and you 

 will find that though you have neither cut nor torn nor 

 broken either muscle or blood-vessel or bone, you can- 

 not get things back into their place again. Everything 

 looks "messy." This is partly because, though you 

 have torn neither muscle nor blood-vessel, you have 

 torn something which binds skin and muscle and fat 

 and blood-vessels and bone all together; and if you 

 look again you will see that between them there is 

 a delicate stringy substance which binds and packs 

 them all together, just as cotton-wool is used to pack 

 up delicate toys and instruments. This stringy pack- 

 ing material which you have torn and spoilt is called 

 connective because it connects all the parts together. 



Well, then, in the leg (and it is just the same in the 

 arm) we have skin, fat, muscle, tendons, blood-vessels, 

 nerves, and bone all packed together with connec- 

 tive and covered with skia These together form the 

 solid leg. We may speak of them as the tissues 

 of the leg. 



8. If now you turn to the trunk and cut through 

 the skin of the belly, you will first of all see muscles 

 again, with nerves and blood-vessels as before. But 

 when you carefully cut through the muscles (for you 

 cannot easily separate, them from each other here), 

 you come upon something which you did not find in 



