LIGAMENTS OF THE STERNUM. 271 



the upper part of the base of the sacrum near the anterior liga- 

 ment of the sacro-iliac articulation with which some of its fibres 

 are blended. y 



The proper ligaments of the pelvis, are as follows, viz. 1. 

 Those which connect the ilium and sacrum. 2. Those between 

 the sacrum and ischium. 3. Those between the sacrum and 

 coccyx, and 4. Those which join the two pubic bones together. 



1. Ligaments connecting the Ilium and Sacrum. 



A long flat ligament called the sacro-spinous (lig. sacro- 

 spinosum) arises from the posterior superior spinous process 

 of the os ilium descends obliquely and is inserted into the third 

 and fourth transverse processes of the sacrum. It sometimes 

 presents the appearance of two separate ligaments. 



The ligaments which form the sacro-iliac junction are two 

 in number, and are called anterior and posterior. 

 The anterior sacro-iliac ligament, consists of a thin plane 

 of short, strong ligamentous fibres, passing from bone to bone on 

 the anterior face of the joint. 



The posterior sacro-iliac ligament, is the main stay of the 

 articulation. It consists of many strong bundles of ligamentous 

 fibres, which cross horizontally over the posterior part of the 

 joint, and are attached by one extremity to the rough surface of 

 the ilium immediately behind the joint, and by the other to 

 two eminences on the lateral margin of the sacrum, as well as 

 the rough surfaces of the bone between them. 



2. Ligaments connecting the Sacrum and Ischium. 



The two sacro-ischiatic ligaments, see fig. 71, are situated in 

 the under and back part of the pelvis. They arise nearly in 

 common from the transverse processes of the os sacrum, from 

 the under and lateral part of that bone, and from the upper part 

 of the os coccygis. The first, called the external posterior or 

 greater, descends obliquely, to be fixed to the tuberosity of 

 the os ischium. The other, called the lesser, internal or ante- 

 rior sacro-sciatic or sacro-ischiatic ligament, runs transversely 

 to be fixed to the spinous process of the os ischium. These 



