428 



DISSECTION OF THE PELVIS. 



and trans- 

 verse pro- 

 cesses. 



Motion. 



Sacro-sciatic 

 ligaments 

 are two : 



great, 



and small ; 



apertures 

 formed by 

 them; 



Ilio-lumbar 

 ligament : 



The lateral ligament passes on each side between the projections 

 representing the transverse processes of the last sacral and first 

 coccygeal vertebrae. 



Movement. While the coccyx remains imossified to the sacrum, 

 a slight antero-posterior movement will take place between them. 



Two SACRO-SCIATIC LIGAMENTS pass from the side of the sacrum 

 and coccyx to the hinder border of the hip-bone, across the space 

 between those bones at the back of the pelvis : they are named 

 great and small. 



The great or posterior ligament (fig. 158, a) is attached above to 

 the posterior inferior iliac spine, and to the side of the sacrum and 

 coccyx ; and below to the inner margin of the ischial tuberosity, 

 sending forwards a prolongation (falciform process) along the ramus 



of the ischium. It is wide at 

 the sacrum, and gets narrower 

 towards the lower end ; but 

 it is somewhat expanded again 

 at the tuberosity. 



The small or anterior liga- 

 ment (fig. 158, 6) is attached in- 

 ternally by a wide piece to 

 the border of the sacrum and 

 coccyx, where it is united with 

 the origin of the preceding 

 band. The fibres are directed 

 outwards, and are inserted as 

 a narrow band into the ischial 

 spine of the hip-bone. Its 

 deep surface is blended with 

 the coccygeus ; and it may be 

 looked upon as being a fibrous 

 portion of that muscle. Above 

 it is the large sacro-sciatic 

 foramen ; and below it is the 

 small foramen of the same 

 name, which is bounded by the two ligaments. 



By their position these ligaments convert into two foramina 

 (sacro-sciatic) the large sacro-sciatic excavation in the dried bones : 

 the openings, and the structures they give passage to, have been 

 described with the buttock (p. 124). 



Use. The sacro-sciatic ligaments, by holding down the lower 

 part of the sacrum, serve to prevent that bone from rotating at the 

 ptcro-iliac articulation, under the influence of the weight pressing 

 on its upper end in the erect position. 



The ILIO-LUMBAR LIGAMENT is a strong triangular band, which 

 springs by its narrow end from- the extremity of the transverse 

 process of the fifth lumbar vertebra. Directed outwards and some- 

 what backwards, it spreads out to be inserted into the iliac crest for 

 about an inch, opposite the back part of the iliac fossa. To the 

 upper border of the ligament the anterior layer of the fascia 



FIG. 158. SACRO-SCIATIC LIGAMENTS. 

 a. Large, and 6, small. 



