ISCHIUM. 231 



prominent rim or lip, to which the cotyloid fibre-cartilage is attached. Below 

 the acetabulum, between it and the tuberosity, is a deep groove, along which 

 the tendon of the Obturator Externus muscle runs, as it passes outwards, to be 

 inserted into the digital fossa of the femur. The internal surface is smooth, 

 concave, and forms the lateral boundary of the true pelvic cavity ; it is broad 

 above, and separated from the venter of the ilium by the linea ilio-pectinea ; 

 narrow below, its posterior border is encroached upon, a little below its centre, 

 by the spine of the ischium, above and below which are the greater and lesser 

 sacro-sciatic notches; in front it presents a sharp margin, which forms the outer 

 boundary of the obturator foramen. This surface is perforated by two or three 

 large vascular foramina, and affords attachment to part of the Obturator In- 

 ternus muscle. The posterior surface is quadrilateral in form, broad and smooth 

 above, narrow below where it becomes continuous with the tuberosity ; it is 

 limited, in front, by the margin of the acetabulum; behind, by the front part 

 of the great sacro-sciatic notch. This surface supports the Pyriformis, the two 

 Gemelli, and the Obturator Internus muscles, in their passage outwards to the 

 great trochanter. The body of the ischium presents three borders, posterior, 

 inferior, and internal. The posterior border presents, a little below the centre, 

 a thin and pointed triangular eminence, the spine of the ischium, more or less 

 elongated in different subjects. Its external surface gives attachment to the 

 Gemellus Superior, its internal surface to the Coccygeus and Levator Ani ; 

 whilst to the pointed extremity' is connected the lesser sacro-sciatic ligament. 

 Above the spine is a notch of large size, the great sacro-sciatic, converted into 

 a foramen by the lesser sacro-sciatic ligament; it transmits the Pyriformis 

 muscle, the gluteal vessels, and superior gluteal nerve passing out of the pelvis 

 above the muscle ; the sciatic artery, the greater and lesser sciatic nerves, the 

 internal pudic vessels and nerve, and a small nerve to the Obturator Internus 

 muscle below it. Below the spine is a smaller notch, the lesser sacro-sciatic ; 

 it is smooth, coated in the recent state with cartilage, the surface of which pre- 

 sents numerous markings corresponding to the subdivisions of the tendon of 

 the Obturator Internus which winds over it. It is converted into a foramen by 

 the sacro-sciatic ligaments, and transmits the tendon of the Obturator Internus, 

 the nerve which supplies that muscle, and the pudic vessels and nerve. The 

 inferior border is thick and broad ; at its point of junction with the posterior is 

 the tuberosity of the ischium. The internal border is thin, and forms the outer 

 circumference of the obturator foramen. 



The tuberosity presents for examination an external lip, an internal lip, and 

 an intermediate space. The external lip gives attachment to the Quadratus 

 Femoris, and part of the Adductor Magnus muscles. The inner lip is bounded 

 by a sharp ridge, for the attachment of a falciform prolongation of the great 

 sacro-sciatic ligament ; it presents a groove on the inner side of this for the 

 lodgment of the internal pudic vessels and nerve; and, more anteriorly, has 

 attached the Transversus Perinei and Erector Penis muscles. The intermediate 

 surface presents four distinct impressions. Two of these, seen at the front part 

 of the tuberosity, are rough, elongated, and separated from each other by a 

 prominent ridge ; the outer one gives attachment to the Adductor Magnus, the 

 inner one to the great sacro-sciatic ligament. Two, situated at the back part, 

 are smooth, larger in size, and separated by an oblique ridge : from the upper 

 and outer arises the Semi-membranosus ; from the lower and inner, the Biceps 

 and Semi-tendinosus. The uppermost part of the tuberosity gives attachmeut 

 to the Gemellus Inferior. 



The ramus, or ascending ramus, is the thin flattened part of the ischium, 

 which ascends from the tuberosity upwards and inwards, and joins the ramus 

 of the pubes their point of junction being indicated in the adult by a rough 

 eminence. The outer surface of the ramus is rough, for the attachment of the 

 Obturator Externus muscle, also some fibres of the Adductor Magnus, and of 

 the Gracilis ; its inner surface forms part of the anterior wall of the pelvis.. 



