THE PELVIC WALLS. 



The pelvic inclination is the angle between the conjugata vera and a horizontal plane (about 

 60 degrees). [The obliquity of the pelvis varies in different individuals, is greater in the female 

 than in the male, and is increased by hip-joint disease, particularly on standing. With a normal 

 inclination of the pelvis the sacral promontory is about 9.5 cm. (3^ inches) above the upper border 

 of the symphysis and the tip of the coccyx is to i inch above its lower border. Wolsey.] From 

 a practical standpoint, it will be noted that, owing to the pelvic inclination, a wound passing 

 through the abdominal wall horizontally above the symphysis may involve the filled bladder, 

 the uterus, and the rectum, parts which are protected posteriorly by the bony pelvic wall (the 

 sacrum). 



The true pelvis, our "first path in life," and of more practical importance than the false 

 pelvis, is accessible in the female to the examining finger or to the entire hand, which may be 

 introduced into the vagina for diagnostic or operative purposes. It commences above at the pelvic 

 inlet or superior aperture of the pelvis; the plane of this aperture passes through the iliopectineal 

 line and is directed anteriorly; it is open below at the smaller cordiform pelvic outlet or inferior 

 aperture of the pelvis. The plane of the latter is curved, the concavity being directed upward, since 

 it descends from the symphysis to the tuberosities of the ischium and then ascends to the tip of 

 the coccyx (compare the two pelvic apertures to the two apertures of the thorax, see page 92). 

 The form of the pelvic canal is that of a truncated and inverted cone or funnel. The anterior 

 wall of the pelvic canal is formed by the symphysis, by the two pubic rami (horizontal and 

 descending), and by the ascending ramus of the ischium. The large obturator foramina are 

 closed by the obturator membranes, only the small obturator canal being left open above and 

 internally. The lateral walls are formed by the acetabular portion of the innominate bone, by 

 the body and descending ramus of the ischium, and by the greater and the lesser sacrosciatic 

 ligaments. The posterior wall corresponds to the sacrum and coccyx and is markedly concave 

 anteriorly. The coccygeal vertebras are connected by discs of fibrocartilage which render them 

 movable, particularly in a posterior direction, as may be observed during the evacuation of a 

 mass of hardened feces and during labor. The obstetrician is consequently justified in regarding 

 an ankylosis of the coccygeal vertebras as a cause of difficult delivery. 



The portions of the pelvis which may be palpated externally are the posterior surfaces of 

 the sacrum and coccyx, the tuberosities of the ischium, the iliac crests, the anterior superior 

 spines of the ilium, and the symphysis pubis. The portions which may be palpated from the 

 vagina and from the rectum are the concave inner surfaces of the sacrum and of the coccyx, 

 the ischium, the pubis, and the pelvic surface of the acetabulum. 



Fractures of the pelvic walls are not infrequently associated with injuries to the organs 

 situated within the pelvis, the urinary bladder, the urethra (particularly in the male), the 

 rectum, the great vessels, and the sacral plexus. 



The bony framework of the pelvis is strengthened by ligaments, muscles, and fascias, which 

 better adapt it to protect the enclosed viscera, vessels, and nerves. The greater and lesser 

 sacrosciatic ligaments strengthen the lateral pelvic wall and aid in the formation of the greater 

 and lesser sacrosciatic foramina. The pyriformis muscle arises from the anterior surface of 

 the sacrum, passes out of the pelvis through the greater sacrosciatic foramen, and inserts into 

 the great trochanter. The foramen is almost entirely closed by the muscle, so that above and 



