THE SACRO-SCIATIC LIGAMENTS. 



179 



united. In some cases, however, the two surfaces are connected in part of their 

 extent by fine transverse fibres ; while on the other hand, it not unfrequently 

 happens, especially in advanced life, that the surfaces become rough and irregular, 

 and are separated by small spaces containing glairy fluid. The bones are united by 

 anterior and posterior sacro-iliac ligaments, and the articulation receives additional 

 support from the great and small sacro-sciatic ligaments. 



The anterior sacro-iliac ligament consists of thin irregular fibres passing 

 between the sacrum and hip-bone on their iliac and pelvic surfaces. 



The posterior sacro-iliac ligament consists of a large number .of strong 

 irregular bundles extending from the rough space above the auricular surface of the 

 ilium, downwards and inwards to the depressions on the back of the lateral mass of 

 the sacrum. A superficial band, passing nearly vertically downwards from the 

 posterior superior iliac spine to the third and fourth pieces of the sacrum, is 

 distinguished as the long or oUique sacro-iliac ligament. 



THE SACKO-SCIATIC LIGAMENTS. The posterior or great sacro-sciatic 

 ligament, broad and triangular, assists in bounding the lower aperture of the pelvis. 



Fig. 20fi. RIGHT HALF OF A FEMALE PELVIS, SEEN 

 FROM THE INNER SIDE. (Allen Thomson.) | 



1, supraspinous ligament descending to the sacrum 

 from 2, 2, the lumbar spinous processes ; 3, 4, lumbar 

 and sacral spinal canal ; 5, placed on the ilium above 

 the anterior sacro-iliac ligament ; 6, placed in the great 

 sacro-sciatic foramen, points to the small sacro-sciatic 

 ligament ; 7, great sacro-sciatic ligament, with 7', its 

 falciform process ; 8, aperture where a portion of the 

 wall of the cotyloid cavity has been removed, so as to 

 give a view from the inside of the head of the femur ; 

 9, interarticular ligament put upon the stretch, the 

 femur being partially flexed and adducted ; 10, inner 

 part of the capsular ligament relaxed ; 11, shaft of the 

 femur. 



Its base is attached to the posterior inferior 

 iliac spine and to the side of the sacrum and 

 coccyx ; while its apex is fixed along the 

 inner margin of the ischial tuberosity, where 

 it expands somewhat, and sends forwards 

 along the margin of the ischial ramus a fal- 

 ciform process the border of which is con- 

 tinuous with, and forms the inferior attachment of, the obturator fascia. Some of 

 the superficial fibres of the ligament are continued over the tuberosity into the 

 tendon of the long head of the biceps muscle. 



The anterior or small sacro-sciatic ligament, much shorter and thinner 

 than the preceding, in front of which it lies, is also triangular in form, and is 

 attached by its base to the side of the sacrum and coccyx, where its fibres are 

 united with those of the great ligament, and by its apex to the spine of the ischium. 

 The deep surface of this ligament is blended with the coccygeus muscle. 



The great sacro-sciatic ligament represents the proximal portion of the tendon of the 

 long head of the biceps muscle, which, has formed an attachment to the ischial tuberosity. 

 The small sacro-sciatic ligament is formed by fibrous degeneration of the superficial part of 

 the coccygeus muscle. 



Foramina. Between the great sacro-sciatic ligament and the hip-bone is a 

 large space subdivided by the small sacro-sciatic ligament. The part which lies 

 above this ligament is named the great sacro-sciatic foramen. It transmits the 



VOL. II. N 



