The non-articular circumference of the lip of the aectahulum is rough and marked by foramina for the passage of nutritious vessels, and also for the attachment of the capsular ligament.
The head of the .femur, representing about three-fourths of a sphere, is supported and con nected to the shaft of that bone at an angle varying with age, by a constricted and flattened process termed the neck. A waving prominent line surrounds the head at its junction with the neck, and may be regarded as the boundary line between these two parts, leaving en its inner side the articular surface of the head of the femur, which is smooth, having in the adult its greater convexity directed upwards and inwards. At one point, however, the ar ticular character of this surface is interrupted by a depression, which is not covered with carti lage in the recent state.. This depression, snu ffled immediately behind and through which the axis of the head of the bone would pass, gives insertion to the ligamentilm teres.
2. The cartilage.—That portion of the sur face of the acetabulum which corresponds to the facies lunata is alone invested by articu lar cartilage. This cartilaginous layer is thick est at its external circumference, becoming gradually thinner as it proceeds internally. The head of the femur, on the other hand, is nearly entirely incrusted with cartilage, which, as is usual on convex surfaces, is thickest towards its centre, where it is interrupted by the depression for the lig-amentum teres, and be comes progressively thinner towards the circum ference.
3. Fibro-eartilage.—Immediately surround ing the marg,in of the acetabulum is a fibre. cartilaginous ring about three lines broad, tri angular in shape, having its base attached to the brim of the cavity, whilst its apex is free. This is the so-called cotyloid ligament ( ligumen tam cotyloideum, fibro-cartilagincum, labium eartilagineum acetabuli.) It clearly belongs to the libro-cartilages of circumference, and is the counterpart of the glenoid ligament in the shoulder-joint (see Ft DttO-Ca aTI LAC E), and as it completely removes the irregular character of the margin of the acetabulum, it will be found to be deepest where it corresponds to the concavities of the acetabular border. Its free border is sharp, and directed inwards, i. e., towards the centre of the joint, narrowing the orifice of the acetabulum, at the same time that it increases the depth of that cavity. Its fixed
margin constitutes its base, and is connected to the brim of the acetabulum; its external sur face covered by synovial membrane corres ponds to the capsular ligament, whilst its inter nal, also covered by synovial membrane, em braces the head of the femur. Having arrived at the notch, it is continued over each cornu of the facies lunata, retaining somewhat of its form, but much diminished in dimensions, and having assumed much more the appearance of pure cartilage than of fibro-cartilage. It ceases at the point at which the concave margin of the facies lunata becomes blended with the con vexity of each cornu. It is not stretched across the notch as some anatomists erroneously describe it. The whole extent of this fibro cartilage, then, corresponds exactly to the con vex margin of the fames lunata.
4. Ligaments.—The notch of the acetabu lum is convened into a foramen, strengthened and in a great degree 'closed by ligamentous fibres arranged in two layers, and extended from the superior to the inferior cornu. The whole forms the ligamentum trans-serrate °Cad buli of Winslow. Of these the external and deepest arises from the superior, and is inserted into the inferior cornu of the acetabulum. The external surface of this layer, directed obliquely backwards towards the cavity of the acetabulum, corresponds and gives attachment to the liga mentum teres. Its internal surface is applied to the external layer ; its external margin is attached to the capsular ligament, and its inter nal superiorly to the pubis, but inferiorly it is free, and bounds a foramen for the passage of vessels. The internal layer of the transverse ligament is attached below to the inferior cornu, and above to the superior, where it appears to blend with the cotyloid ligament. By its exter nal surface it is in apposition with the external layer of the transverse ligament, and its inter nal surface is directed towards the obturator ligament and external obturator muscle. Some fibres pass from its upper margin to the obtu rator ligament ; hut in greatest part this mar gin contributes to form the foramen already described for the passage of vessels. Its infe rior margin affords attachment to the capsular ligament.