THE PELVIS. 



279 



Attachment of Muscles. To the ilium, sixteen. To the outer lip of the crest, 

 the Tensor vaginae femoris, Obliquus externus abdominis, and Latissimus dorsi ; 

 to the internal lip, the Iliacus, Transversalis, Quadratus lumborum, and Erector 

 spinse ; to the interspace between the lips, the Obliquus internus. To the outer 

 surface of the ilium, the Gluteus maximus, Gluteus medius, Gluteus minimus, 

 reflected tendon of the Rectus ; to the upper part of the great sacro-sciatic notch, a 

 portion of the Pyriformis ; to the internal surface, the Iliacus : to that portion of 

 the internal surface below the linea ilio-pectinea, the Obturator internus, and the 

 Multifidus spime to the internal surface of the posterior superior spine ; to the 

 anterior border, the Sartorius and straight tendon of the Rectus. To the ischium, 

 fourteen. To the outer surface of the ramus, the Obturator externus and Adductor 

 magnus ; to the internal surface, the Obturator internus and Erector penis. To the 

 spine, the Gemellus superior, Levator ani, and Coccygeus. To the tuberosity, the 

 Biceps, Semitendinosus, Semimembranosus, Quadratus femoris. Adductor magnus, 



. , . f Three primary (Ilium, Ischium, and Os Pubis). 



By eight centre* j pi^sLndary. 



8. Symphysis pubis. 



The three primary centres unite through \-shaped piece about puberty. 

 Epiphyses appear about puberty, and unite about 25th year. 



FIG. 209. Plan of the development of the os innoniiimtnm. 



Gemellus inferior, Transversus peringei, Erector penis. To the os pubis. sixteen: 

 Obliquus externus, Obliquus internus, Transversalis, Rectus, Pyramidalis, Psoas 

 parvus, Pectineus, Adductor magnus, Adductor longus. Adductor brevis, Gracilis, 

 Obturator externus and internus, Levator ani, Compressor urethrae, and occasion- 

 ally a few fibres of the Accelerator urinae. 



The Pelvis (Figs. 210, 211). 



The Pelvis, so called from its resemblance to a basin (L. pelvis), is stronger 

 and more massively constructed than either the cranial or thoracic cavity : it is a 

 bony ring, interposed between the lower end of the spine, which it supports, and 

 the lower extremities, upon which it rests. It is composed of four bones : the two 

 ossa innominati. which bound it on either side and in front, and the sacrum and 

 coccyx, which complete it behind. 



The pelvis is divided by a plane passing through the prominence of the sacrum, 



