THE PELVIS. 



and forms the anterior portion of the linea ilio-pectinea, to 

 which is attached G-imbernat's ligament and the fascia 

 lata. The anterior ridge is more round, and ends at the 

 upper margin of the acetabulum. Between the two ridges 

 is situated the pectineus muscle. Internal to the spine of 

 the pubis is the crest, leading transversely to the median 

 line, and about an inch in length. It gives attachment to 

 the rectus abdominis and pyramidalis muscles, and to the 

 united tendons of the internal oblique and trans versalis. 

 From the crest there is an inferior or descending portion 

 called the sympJiysis and descending ramus. The symphysis 

 is vertical and rough, and forms with the crest the angle of 

 the pubis. It meets its fellow of the opposite side by an in- 

 termediate substance of fibre-cartilage. The ramus goes 

 backward and outward to meet the ramus of the ischium, 

 and its outer edge bounds the thyroid foramen, while its 

 inner edge gives attachment to the crus of the penis or the 

 clitoris. The space between the rami on either side and 

 below the symphysis describes a curve called the arch of 

 the pubis. 



The innominatum, composed of three bones, presents at 

 their common point of junction a deep, hemispherical cavity, 

 the acetabulum or cotyloid cavity. The ilium forms a little 

 less than two-fifths, the ischium a little more than two- 

 fifths, and the pubis about one-fifth of this cavity. It is 

 bounded by a deep notch internally, which is converted, by 

 a ligament stretched across from the pubis to the ischium, 

 into a foramen, through which pass the articular vessels. 

 The superior and outer part of this cavity is smooth, cov- 

 ered with cartilage, and receives the head of the thigh bone. 

 The central portion and the part leading from it to the 

 notch, is rough, gives attachment to the ligamentum teres, 

 and contains a quantity of soft adipose matter. 



In the front of the innominatum and to the inside of each 

 acetabulum are seen two large foramina, called the obturator 

 or thyroid. These are formed by the ischium and pubis. 

 The edge of this opening is thin and has superiorly a 

 groove for the passage of the obturator vessels and nerve. 



