THE FEMUR, OR THIGH-BONE. 



289 



owing to a separation of the layers of the bone into cancelli. which project into the 

 medullary canal and finally obliterate it. so that the upper and lower ends of the 

 shaft, and the articular extremities more especially, consist of cancellated tissue 

 invested by a thin, compact layer. 



The arrangement of the cancelli in the ends of the femur is remarkable. In 

 the upper end they are arranged in two sets. One, starting from the top of the head, 

 the upper surface of the neck, and the great trochanter, converge to the inner 

 circumference of the shaft (Fig. 215) ; these are placed in the direction of greatest 

 pressure, and serve to support the vertical weight of the body. The second set 

 are planes of lamellae intersecting the former nearly at right angles, and are situ- 

 ated in the line of the greatest 

 tension that is to say, along the 

 lines in which the muscles and 

 ligaments exert their traction. 

 In the head of the bone these 



Great trochatiter. 



_ Digital fossa. 



FIG. 215. Diagram showing the arrange- 

 ment of the cancelli of the neck of the femur. 



FIG. 216. Calcar femorale. 



planes are arranged in a curved form, in order to strengthen the bone when exposed 

 to pressure in all directions. In the midst of the cancellous tissue of the neck is 

 a vertical plane of compact bone, the femoral spur (calcar femorale) which com- 

 mences at the point where the neck joins the shaft midway between the lesser 

 trochanter and the internal border of the shaft of the bone, and extends in the 

 direction of the digital fossa (Fig. 216). This materially strengthens this portion 

 of the bone. Another point in connection with the structure of the neck of the 

 femur requires mention, especially on account of its influence on the production of 

 fracture in this situation. It will be noticed that a considerable portion of the 

 great trochanter lies behind the level of the posterior surface of the neck ; and if a 

 section be made through the trochanter at this level, it will be seen that the 

 posterior wall of the neck is prolonged into the trochanter. This prolongation is 

 termed by Bigelow the " true neck." l and forms a thin, dense plate of bone, which 

 passes beneath the posterior intertrochanteric ridge toward the outer surface of 

 the bone. 



In the lower end the cancelli spring on all sides from the inner surface of 

 the cylinder, and descend in a perpendicular direction to the articular surface, the 

 cancelli being strongest and having a more accurately perpendicular course above 

 the condyles. In addition to this, however, horizontal planes of cancellous tissue 



Bigelow on the Hip, p. 121. 



