THE FRAMEWORK OF THE BODY. 



1? 



5. The Structure of the Bones. If we examine one 

 of the long bones, which has been sawn through length- 

 wise, we observe that it is admirably fashioned for affording 



A. Longitudinal B. Transverse section of bone. 



FIG. 1. SECTION op BONE. 



lightness as well as strength (Fig. 1). Its exterior is hard 

 and resisting, but it is porous at the broad extremities, 

 while through the central portion 

 there is a cavity or canal which con- 

 tains an oily substance, called marrow. 

 Let us now take a thin section of 

 bone, and examine it under the mi- 

 croscope ; we discover that it is pierced 

 by numerous fine tubes (Fig. 2), 

 about which layers of bone-substance 

 are arranged. Accordingly, though a 

 bone be as hard as stone externally, it 

 is by no means as heavy as stone, by 

 reason of its light interior texture. 

 Another element of power is found in 

 the curved outline of the bones. The pre 2 



curved line is said to be " the line of structure of bone en- 

 beauty," as it certainly is the line of lar ed - 

 strength, and is uniformly employed 

 in the bones whose position exposes them to accident. 



5. In what respect admirably fashioned ? Its formation? Microscopic exam 

 Ination ? The inference ? " Line of beauty ?" 



