y 



188 



THE SKELETON. 



little behind the centre of the lower border of this surface: the front part of this 

 depression gives origin to the Popliteus muscle, the tendon of which is lodged in 

 the groove during flexion of the knee. The groove is smooth, covered with carti- 

 lage in the recent state, and runs upward and backward to the posterior extremity 

 of the condyle. The inner surface of the outer condyle forms one of -the lateral 

 boundaries of the intercondyloid notch, and gives attachment, by its posterior part, 

 to the anterior crucial ligament. The inferior surface is convex, smooth, and broader 

 than that of the internal condyle. The posterior extremity is convex and smooth : 

 just above and to the outer side of the articular surface is a depression for the tendon 

 of the outer head of the Gastrocnemius, above which is the origin of the Plantaris. 



Inner Condyle. The inner surface of the inner condyle presents a convex emi- 

 nence, the inner tuberosity, rough for the attachment of the internal lateral liga- 

 ment. The outer side of the inner condyle forms one of the lateral boundaries 

 of the intercondyloid notch, and gives attachment, by its anterior part, to the 

 posterior crucial ligament. Its inferior or articular surface is convex, and 

 presents a less extensive surface than the external condyle. Just above the articular 

 surface of the condyle, behind, is a depression for the tendon of origin of the inner 

 head of the Gastrocnemius. 



Structure. The shaft of the femur is a cylinder of compact tissue, hollowed 

 by a large medullary canal. The cylinder is of great thickness and density in the 

 middle third of the shaft, where the bone is narrowest and the medullary canal 

 well formed ; but above and below this the cylinder gradually becomes thinner, 

 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. 128) ; 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 



trochanter. 



_ Digital fossa. 



Pressure 

 planes. 



FIG. 128. Diagram showing the arrange- 

 ment of the cancelli of the neck of the femur. 



FIG. 129. Calcar femorale. 



