THE CANCELLI OF BONES 113 



It is worthy of notice in connection with these 

 directions of force, that the radiating series (a a), 

 which support pressure by their rigidity, are the 

 strongest, and the series at right angles and 

 between them, which serve as braces, are more 

 slender ; while the curved series (b &), which 

 resist by their tenacity, are the strongest, and the 

 braces, which may be regarded as a continuation 

 of the radiating series, are the weakest ; precisely 

 as would be the case in the frame of a building : 

 the braces of the circular series become stronger 

 as you approach the centre of the bone where the 

 pressure becomes the greatest. 



The shell of the neck is of itself sufficient to 

 support great weight, in virtue of its form and 

 structure ; but its power of resistance is still far- 

 ther increased by the cancelli, which form within 

 a light truss or framed arch ; the long fibres at 

 (a) transfer weight directly to the under side of 

 the neck. They, as well as the shell of the neck 

 at (d), are supported by the curved fibres (b b), 

 and these in turn by the radiating fibres (a). 

 The whole may be regarded as equivalent to an 

 increased thickness of those portions of the shell 

 of bone above and below, which are the seats of 

 the greatest strain and pressure. 



The weight of the body is transmitted through 

 the shaft of the femur to the condyles below, the 

 space between these sustaining but little pressure. 



