OF THE PELVIS. 243 



in breadth, and is prolonged forward along the inner margin of the ramus, forming 

 what is known as the falciform ligament. The free concave edge of this prolonga- 

 tion has attached to it the obturator fascia, with which it forms a kind of groove, 

 protecting the internal pudic vessels and nerve. One of its surfaces is turned 

 toward the perinaeum, the other toward the Obturator internus muscle. 



The posterior surface of this ligament gives origin, by its whole extent, to fibres 

 of the Gluteus maximus. Its anterior surface is united to the lesser sacro-sciatic 

 ligament. Its external border forms, above, the posterior boundary of the great 

 sacro-sciatic foramen, and, below, the posterior boundary of the lesser sacro-sciatic 

 foramen. Its lower border forms part of the boundary of the perinaeum. It is 

 pierced by the coccygeal branch of the sciatic artery and coccygeal nerve. 



The Lesser or Anterior Sacro-sciatic Ligament, much shorter and smaller 

 than the preceding, is thin, triangular in form, attached by its apex to the spine 

 of the ischium, and internally, by its broad base, to the lateral margin of the 

 sacrum and coccyx, anterior to the attachment of the great sacro-sciatic ligament, 

 with which its fibres are intermingled. 



It is in relation, anteriorly, with the Coccygeus muscle ; posteriorly, it is covered 

 by the great sacro-sciatic ligament and crossed by the internal pudic vessels and 

 nerve. Its superior border forms the lower boundary of the great sacro-sciatic 

 foramen ; its inferior border, part of the lesser sacro-sciatic foramen. 



These two ligaments convert the sacro-sciatic notches into foramina. The 

 superior or great sacro-sciatic foramen is bounded, in front and above, by the 



POUPART'S 

 LMAttC 



ANT. SACRO-ILIAC 

 LIGAMENT. 



GREAT SACRO- 

 SCIATIC "LIGA- 



LESSER SACRO- 

 SCIATIC LIGA- 

 MENT. 



GREAT SACRO- 

 SCIATIC LIGA- 

 MENT. 



Obturator 

 membrane 



FIG. 166. Side view of pelvis, showing the great and lesser sacro-sciatic ligaments. 



posterior border of the os innominatum ; behind, by the great sacro-sciatic ligament ; 

 arid below, by the lesser sacro-sciatic ligament. It is partially filled up, in the 

 recent state, by the Pyriformis muscle, which passes through it. Above this muscle 

 the gluteal vessels and superior gluteal nerve emerge from the pelvis, and, below 

 it, the sciatic vessels and nerves, the internal pudic vessels and nerve, the inferior 

 gluteal nerve, and the nerves to the obturator internus and quadratus femoris. The 

 inferior or lesser sacro-sciatic foramen is bounded, in front, by the tuber ischii ; 

 above, by the spine and lesser sacro-sciatic ligament ; behind, by the greater sacro- 



