372 



HUMAN ANATOMY. 



the side of the cavity between the notch in the acetabulum and the head of the bone. 

 Many of the statements of its absence require confirmation by more observations. 

 Thus, among the anthropoid apes it seems to be generally present in all but the 

 ourang. In this animal, though usually wanting, it has been found in a rudimentary 

 condition. Meckel declared that it was absent in the gibbon, but we believe no 

 other observer has had a similar experience. It is very strongly developed in the 

 ostrich, but is wanting in the rhea (the American ostrich) and probably in the casso- 

 wary. Sutton ' considers it as the tendon of the pectineus muscle which has become 

 separated through skeletal modifications. Sutton relies a good deal on the condition 

 in the horse for support in his argument. He found it consisting of two bands, — 

 one within the joint, apparently the usual ligament, and another passing out of the 

 cavity to the linea alba at its junction with the pubes, which he calls the pubo- 

 femoral portion. The pectineus muscle arises in part from this latter portion. 

 Sutton gives a table telling the story of the structure according to his theory. In 

 sphenodon (a lizard) the tendon of the ambiens, representing the pectineus, passes 



Fig. 388. 



Cotyloid ligament Bursa beneath ilio-psoas 



Round ligament 



Spine of ischium 



Front of capsule 



Capsule a tached to neck 

 of femur 



Cotyloid ligament Tendon of obturator externus 



Horizontal section through right hip-joint. 



into the joint to the head of the femur ; in the ostrich the ligament is continuous 

 with the tendon by means of connective tissue ; in the horse the two parts are 

 distinct ; and in man the external part is wanting. The structure is evidently a very 

 variable one. 



The synovial membrane (Figs. 386, 388) lines the capsule, covers the cotyloid 

 and transverse ligaments, surrounds the ligamentum teres, and covers the fat in the 

 fossa of the acetabulum. It is reflected from the femoral attachment of the capsule 

 onto the neck, which it invests to the border of the articular cartilage. This reflected 

 part presents certain folds caused by fibres from the capsule running up along the 

 neck, called retinaciila (Fig. 390). There are generally three chief ones : a superior^ 

 starting from the superior cervical tubercle and running along the upper border, or 

 backward across the neck to the head of the femur ; a middle, from near the inferior 

 cervical tubercle along the front of the lower border of the neck ; and an inferior, 

 from near the lesser trochanter along the lower side. Any of these may be more 

 or less free from the neck. 



^ Journal of Anatomy and Physiology, vol. xvii., 1883. 



