98 



PHYSIOLOGY 



CHAP. 



The head of the femur is united obliquely by its neck to the 

 shaft of the bone, at an angle which usually diminishes during the 

 period of growth under the influence of the weight of the body, and 

 varies in the adult from 110 to 140. In the shaft of the femur, 

 which is by far the larger portion, the compact bone forms a tube 

 with thick, solid walls, filled with marrow which is largely fat. 



FIG. 64. Section through the end of a femur. (Zaaijer.) 



But at the upper end of the femur, including the head, neck, 

 and trochanters, in consequence of the obliquity of the head to the 

 longitudinal axis of the bone the conditions for obtaining the 

 necessary strength become extremely complex, since the compact 

 substance of the tube extends (Fig. 64) into a system of lamellae 

 arranged fanlike so as to support the surfaces destined to bear the 

 greatest pressure. 



It should be noted that when from pathological conditions, for 



