THE CANCELLI OF BONES 111 



trochanter at (d). Both of these series are braced 

 by other fibres, which are arranged at right angles 

 to their direction. The cancelli of the great tro- 

 chanter at (c) have no determinate form. 



If this description be correct, the " archwork ' 

 described by Mr. Ward does not exist, nor the 

 more complex arrangement described by Bour- 

 gery and Jacob. In fact, an arch which should 

 be made to resist force in this direction would 

 not be used in accordance with recognized archi- 

 tectural rules. An arch is usually made to resist 

 or sustain pressure in lines perpendicular to its 

 surface ; but is not adapted for opposing lateral 

 traction. 



The upper series of fibres will get their points 

 of resistance on the wall of bone below the tro- 

 chanter, and not on the supposed archwork. The 

 curved fibres (b b) will resist in virtue of their 

 tenacity, and the straight or radiating series (a ci) 

 in virtue of their rigidity. One resists and is 

 adapted to resist pressure, and the other resists 

 and is equally adapted to resist traction. 



We can appreciate the effect which force ap- 

 plied to the head of the femur would have upon 

 its shell and cancelli, by calling to mind what 

 takes place in a cylinder or tube when an attempt 

 is made to bend it. If it be but slightly elastic, 

 it will become more or less flattened or collapsed 

 on the side toward which it is bent ; if sufficient 



