382 HUMAN ANATOiMY. 



tion, which sometimes shows thickening over the inner surface of the acetabulum in 

 the latter case and not in the former (Cheyne). In dislocation from disease, unless 

 there has been separation of the head or great absorption of the neck, the tro- 

 chanter will be farther away from the middle line on the affected side than on the 

 sound one. This will serve to distinguish shortening of the limb due to this cause 

 from shortening due to acetabular deepening. Abscesses developing within the 

 joint may pass outward through the thin posterior part of the capsule, and under 

 the gluteal muscles, to a point beneath the greater trochanter ; they may make their 

 exit through the cotyloid notch and point in Scarpa's triangle ; they frequently 

 pass out anteriorly, and are found beneath the tensor vaginae femoris at the outer 

 aspect of the thigh ; they may perforate the acetabulum and point within the 

 pelvis. A finger in the rectum may then detect fluctuation through the structures 

 that separate the abscess from the rectal wall, — viz. , the anal fascia, the levator ani, the 

 obturator fascia and obturator internus, and the periosteum of the inner surface of 

 the innominate bone. After perforation of the acetabulum, an abscess may extend 

 upward and point above Poupart's ligament on the inner side of the vessels. 



Excision of the hip may be done either by means of an anterior incision 

 passing between the tensor vaginae and sartorius muscles superficially and the 

 glutei and rectus more deeply, or by a posterior incision in the line of the limb 

 and just back of the greater trochanter, the muscles attached to which being divided 

 as close to the bone as. possible. 



THE FRAMEWORK OF THE LEG. 



This is formed by the {ibia and the fibula and the interosseous membrane ( Fig. 

 411). The bones are so closely united as to constitute one apparatus, but as they 

 are separable it is necessary to describe them apart. The tibia, very much the larger, 

 is the only one concerned in forming the knee-joint, and bears almost the whole 

 weight. It forms the upper and inner side of the mortise known as the ankle-joint. 

 The fibula, placed externally and posteriorly, is a slender bone. The upper end has 

 a true joint with the tibia, the lower is more closely fastened to it. The interosseous 

 membrane is at the bottom of a hollow between the bones. The arrangement favors 

 lightness, as it gives increased size for the origin of muscles. The joints of the 

 fibula, as well as its elasticity, serve to break shocks. 



THE TIBIA. 



The tibia consists of a shaft, an upper and a lower extremity. 



The upper extremity, or head, composed of an ouier and an inner hiberosity, 

 is very large, expanding laterally from the shaft. 'The outHne of the upper surface 

 is transversely oval, the inner end being the broader. It is chiefly occupied by two 

 articular surfaces for the condyles of the femur, separated at the middle by a promi- 

 nence, the spine, ^ with a triangular non-articular surface before and behind it. The 

 former of these is rough, the latter smooth and grooved. The spine itself is com- 

 posed of two lateral parts connected behind, of which the inner is the longer from 

 before backward, rising from the condylar surfaces. The crucial ligaments of the 

 knee-joint are attached to the non-articular surfaces before and behind it. The 

 inner condylar facet is concave ; it has an oval outline and is longer from before 

 backward than transversely. It rises as a ridge on the side of the spine. The outer 

 facet is more nearly circular, being shorter than the inner. It is slightly depressed 

 in the middle. The posterior half is usually a little convex from before backward, 

 and is often prolonged onto the posterior surface of the bone. The convexity is 

 much greatei when the semilunar cartilage is intact. The front half may be plane, 

 convex, or concave in the same direction. This facet rises to a point on the outer 

 side of the spine. The tuberosities ' overhang the back of the tibia. They are 

 separated behind by the popliteal notch^ continuous with the groove from the top. 

 Under the back of the outer tuberosity is a small articular facet for the head of the 

 fibula, looking downward and a little backward and outward. Its outline is uncer- 

 tain, being either round or quadrilateral. It may be curved in any direction, and 



' Emioentia iutercondyloidea. - CoDdylus lateralis et medialis. '^ Fossa intercondyloidea posterior. 



