258 HIP JOINT. 



From this depression a strong round ligametit (ligament-urn teres 

 or rotundum) see fig. 71, p. 270, arises, which appears to pass 

 into the depression, near the centre of the acetabulum ; but 

 actually terminates in the lower edge of the cartilaginous ring 

 or margin, where it crosses over the notch, and not in the bone. 

 This ligament is in fact divided into two parts at its insertion ', 

 one passes out at the inferior .part of the cotyloid notch and is 

 inserted on the margin of the ischium ; the other runs to the 

 superior end of the notch, and besides being blended with the 

 cotyloid ligament, is attached to the margin of the acetabulum. 

 The thin (synovial) membrane with which this ligament is 

 invested extends to the centre of the acetabulum, and has given 

 rise to the opinion that the ligament was inserted in the bottom 

 of the acetabulum.* 



This ligament allows the head of the os femoris to rise out of 

 the acetabulum, but it is probably torn in every luxation of the 

 os femoris. 



The capsular ligament, which contains these articulating 

 parts, is the strongest in the body. It arises around the aceta- 

 bulum, near the basis of the cartilaginous brim, but it does not 

 adhere to the cartilaginous edge ; and it is inserted into the os 

 femoris, near the roots of the trochanters^sb that it includes a 

 large portion of the neck of the bone. It is not every where of 

 the same thickness and strength ; for, in various places, there 

 are additional ligamentous fibres. The largest portion of these 

 additional fibres appears to arise from the inferior anterior spinous 

 process of the ilium. The capsular ligament is thinest at its 

 internal and posterior part. The additional fibres which arise 

 from the anterior inferior spinous process of the ilium constitute 

 the ilio-femoral, or accessory ligament. 



The synovial membrane forms the internal lamina of this 

 ligament: it invests the articulating surfaces in the usual manner, 

 and being reflected from the internal surface of the capsular 

 ligament to the neck of the os femoris, it is in the place of 

 periosteum to that part of the bone. 



It seems probable that this membrane is so reflected and 



* See motions of skeleton. 



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