92 ACETABULUM. OBTURATOR FORAMEN. 



a little less than two-fifths being formed by the ilium, a little more 

 than two-fifths by the ischium, and the remaining fifth by the pubes. 

 It is bounded by a deep rim or lip, which is broad and strong above, 

 where most resistance is required, and marked in front by a deep 

 notch, which is arched over in the fresh subject by a strong ligament, 

 and transmits the nutrient vessels into the joint. At the bottom of 

 the cup, and communicating with the notch, is a deep and circular 

 pit (fundus acetabuli), which lodges a mass of fat, and gives attach- 

 ment to the broad extremity of the ligamentum teres. 



The obturator or thyroid foramen is a large oval interval between 

 the ischium and pubes, bounded by a narrow rough margin, to which a 

 ligamentous membrane is attached. The upper part of the foramen is 

 increased in depth by the groove in the under surface of the os pubis, 

 which lodges the obturator vessels and nerve. 



Development. By eight centres ; three principal, one for the ilium, 

 one for the ischium, and one for the pubes ; and five secondary, one, 

 the Y shaped piece for the interval between the primitive pieces in 

 the acetabulum, one for the crest of the ilium, one (not constant ) for 

 the anterior and inferior spinous process of the ilium, one for the 

 tuberosity of the ischium, and one (not constant) for the angle of 

 the os pubis. Ossification commences in the primitive pieces, im- 

 mediately after that in the vertebrae, firstly in the ilium, then in 

 the ischium, and lastly in the pubes ; the first ossific deposits being 

 situated near to the future acetabulum. At birth, the acetabulum, 

 the crest of the ilium, and the ramus of the pubes and ischium, are 

 cartilaginous. The secondary centres appear at puberty, and the 

 entire bone is not completed until the twenty-fifth year. 



Articulations. With three bones ; sacrum, opposite innominatum, 

 and femur. 



Attachment of Muscles and Ligaments. To thirty-five muscles ; to 

 the ilium, thirteen ; by the outer lip of the crest, to the obliquus ex- 

 ternus for two-thirds, and to the latissimus dorsi for one-third its 

 length, and to the tensor vaginae femoris by its anterior fourth ; by the 

 middle of the crest, to the internal oblique for three-fourths its length, 

 by the remaining fourth to the erector spinae ; by the internal lip, to 

 the transversalis for three-fourths, and to the quadratus lumborum by 

 the posterior part of its middle third. By the external surface, to the 

 gluteus medius, minimus and maximus, and to one head of the rectus ; 

 by the internal surface, to the iliacus ; and by the anterior border to 

 the sartorius, and the other head of the rectus. To the ischium 

 sixteen ; by its external surface, the adductor magnus and obturator 

 externus ; by the internal surface, the obturator internus and levator 

 ani ; by the spine, the gemellus superior, levator ani, coccygeus, and 

 lesser sacro-ischiatic ligament ; by the tuberosity, the biceps, semi- 

 tendinosus, semi-membranosus, gemellus inferior, quadratus femoris, 

 erector penis, tranversus perinei, and great sacro-ischiatic ligament ; 

 and by the ramus, the gracilis, accelerator urinae, and compressor 

 urethrae. To the os pubis fifteen ; by its upper border, the obliquus 



