THE BONES. 79 



passing to the spina ischii. Important at the time of labour on account of the 

 turning of the foetal head. 



The Obturator foramina, 2, foramen obtur atorium, s. ovale, formed by the 

 ischium and pubis, lies at the anterior region of the pelvis. At the superior 

 external wall a groove, for art., ven., nerv. obturatorius ; otherwise entirely 

 closed by the memb. obturatoria. External boundary for the m. obtur. extern.; 

 internal for in. obtur. intern. 



Symphi/sis ossium pubis, in the central line of the body at the anterior re- 

 gion of the Pelvis, formed by the internal vertical borders of the two ossa 

 pubis, 15 to 20 lines in height, higher in the male than the female. The arti- 

 cular surfaces are oval, flat, but directed obliquely from behind and internally 

 to before and externally. There is a triangular space, with the apex behind, 

 between them, which is filled with an elastic, strong, Ligamentum interos- 

 seum pubis. Besides this, three ligamenta pubica serve to unite the pubes, 

 the most important of which, triangulare, assists in forming the pubic arch. 



The Pubic arch, Arcus pubis, angular in the male, round in the female, is 

 formed by the ascending rand of the Ischia on either side, by the inferior 

 border of the Ram. descend, os pubis, and the Itgam. triangulare s. arcuatum. 

 Superior transverse diameter one inch, inferior three inches. 



The Sacro-lliac symphysis unites the ossa innominata behind with the 

 sacrum, superficies auriculares, making a double angle, first vertical, then from 

 behind to before. This articulation is also moveable, although not to the 

 same extent as the Symph. pubis. 



93. Cavity of the Pelvis, cavitas pelvis, 



contains, a portion of the small intestines, the rectum, the urinary 

 bladder, the internal organs of generation, vascular and nervous 

 trunks. 



1. Pelvis major, the great Pelvis: open before and behind, 

 (closed behind, if we consider with the Obstetricians, that the 

 fifth Lumbar vertebra forms a part of the pelvis,) formed by the 

 alas, of the Ilia, fossse iliacse, for m. Iliacus intern., and the 

 small intestine ; is below narrower where the linea arcuata di- 

 vides it from the small pelvis. Anterior transverse diameter 

 between the Spinse anter. sup. Eight to nine inches. 



Linea arcuata, a crescentic raised line, passing from the centre 

 of the superior border of the Sacrum; over this, the Ilium and 

 the os pubis to the anterior spine of the pubis. 



Promontorium angle of the fifth lumbar vertebra with the 

 sacrum. 



2. Pelvis minor, the small pelvis at the superior and inferior 

 outlet narrower than in the centre. 



a. Apertura superior, elliptical or oval, with three diameters: 



1. Straight diam., conjugata [antero-posterior] = 4 inches, from Promon- 

 tory to superior border of symphysis pubis. 



2. Transverse diam. = 5 inches from the centre of the linea arcuata of the 

 one to that of the opposite side. 



3. Oblique diam., Diam. Deventeri, two, = 4 inches from sacro-iliac sym- 



