BODY OF THE HOUSE. 55 



holes in each side of the spine as there are 

 vertebrae. Through these holes large branches 

 of the marrow of the spine pass off, like the 

 branches of a tree, to all parts of the body. 

 These branches are called nerves. At first, 

 they are pretty large ; but they divide and 

 subdivide, as they proceed towards the extremi- 

 ties of the frame, titt they become very small. 

 Their number, in all the soft parts of the body, 

 particularly in the skin, is very great. I do 

 not know that they could be counted. 



Those things which look like three arms, by 

 interlocking with the bones above and below 

 them, serve as braces to the whole spine. At 

 the sides are parts of the ribs (c e.) These 

 show where the spine and ribs come together. 



Between these bones, where the body of each 

 (a) rests upon the other, is a tough substance 

 or gristle, very yielding or elastic, almost like 

 India rubber. This keeps the bones from 

 wearing out too fast when they move, and yet 

 it allows of their moving pretty freely. 



The spine is, really, one of the most curious 

 things in nature. Why, rope-dancers and tum- 

 blers will bend their heads back till they almost 

 touch their feet, and bring this straight, pile of 



