88 PELVIS. 



coccygeus, and lesser sacro-ischiatic ligament ; by the tuberosity, the 

 biceps, semi-tendinosus, semi-membranosus, gemellus inferior, quad- 

 ratus femoris, erector penis, transversus perinei, and great sacro- 

 ischiatic ligament ; and by the ramus, the gracilis, accelerator urince, 

 and compressor urethrae. To the pubis fifteen ; by its upper border, 

 the obliquus externus, obliquus internus, transversalis, rectus, pyra- 

 midalis, pectineus, and psoas parvus ; by its external surface, the 

 adductor longus, adductor brevis and gracilis ; by its internal surface, 

 the levator ani, compressor urethrse, and obturator internus; and 

 by the ramus, the adductor magnus, and accelerator urina?. 



PELVIS. 



The pelvis considered as a whole is divisible into a false and true 

 pelvis ; the former is the expanded portion, bounded on each side by 

 the ossa ilii, and separated from the true pelvis by the linea ilio- 

 pectinea. . The true pelvis is all that portion which is situated be- 

 neath the linea ilio-pectinea. This line forms the margin or brim of 

 the true pelvis, while the included area is called the inlet. The form 

 of the inlet is heart-shaped, obtusely pointed in front at the symphysis 

 pubis, expanded on each side, and encroached upon behind by a 

 projection of the upper part of the sacrum, which is named the pro- 

 montory. The cavity is somewhat encroached upon at each side 

 by a smooth quadrangular plane of bone, corresponding with the 

 internal surface of the acetabulum, and leading to the spine of the 

 ischium. In front are two fossa? around the obturator foramina, for 

 lodging the obturator internus muscle, at each side. The inferior 

 termination of the pelvis is very irregular, and is termed the outlet. 

 It is bounded in front by the convergence of the rami of the ischium 

 and pubis, which constitute the arch of the pubis ; on each side by 

 the tuberosity of the ischium, and by two irregular fissures formed 

 by the greater and lesser sacro-ischiatic notches ; and behind by the 

 inferior borders of the sacrum, and by the coccyx. 



The pelvis is placed obliquely with regard to the trunk of the body, 

 so that a line drawn through the central axis of the inlet, would touch 

 by one extremity the lower part of the sacrum, and by the other 

 would pass through the umbilicus. The axis of the inlet is therefore 

 directed downwards and backwards, while that of the outlet points 

 downwards and forwards, and corresponds with a line drawn from 

 the upper part of the sacrum, through the centre of the outlet. The 

 axis of the cavity represents a curve, the extremities of which will 

 be indicated by the central points of the inlet and outlet. A know- 

 ledge of the direction of these axes is most important to the surgeon, 

 as indicating the line in which instruments should be used in opera- 

 tions upon the viscera of the pelvis, and the direction of force in the 

 removal of calculi from the bladder ; and to the accoucheur, as ex- 

 plaining the course of the foetus during parturition. 



There are certain striking differences between the male and 

 female pelvis. In the male the bones are thicker, stronger, and 



