THE PELVIS. 283 



ward. The tuberosities of the ischia and the acetabula are wider apart. The 

 pubic arch is wider and more rounded than in the male, where it is an angle 

 rather than an arch ; its pillars^ are somewhat excavated, and sloped from within 

 outward, so that their inner surfaces look forward. In consequence of this the 

 width of the fore part of the pelvic outlet is much increased and the passage of the 

 foetal head facilitated. 



The size of the pelvis varies, not only in the two sexes, but also in different 

 members of the same sex. This does not appear to be influenced in any way by 

 the height of the individual. Women of short stature, as a rule, have broad pelves. 

 Occasionally the pelvis is equally contracted in all its dimensions, so much so that 

 all its diameters measure an inch less than the average, and this even in women 

 of average height and otherwise well formed. The principal divergences, however, 

 are found at the inlet, and affect the relation of the antero-posterior to the transverse 

 diameter. Thus we may have a pelvis the inlet of which is elliptical either in a 

 transverse or antero-posterior direction ; the transverse diameter in the former 

 and the antero-posterior in the latter greatly exceeding the other diameters. Again, 

 the inlet of the pelvis in some instances is seen to be almost circular. 



The same differences are found in various races. European women are said to 

 have the most roomy pelves. That of the negress is smaller, circular in shape, and with 

 a narrow pubic arch. The Hottentots and Bushwomen possess the smallest pelves. 



In ihefcetus and for several years after birth the pelvis is small in proportion 

 to that of the adult. The cavity is deep, and the projection of the sacro-vertebral 

 angle less marked. The antero-posterior and transverse diameters are nearly 

 equal. About puberty the pelvis in both sexes presents the general characters of 

 the adult male pelvis ; but after puberty it acquires its proper sexual characters. 



Surface Form. The pelvic bones are so thickly covered with muscles that it is only at cer- 

 tain points tliat they approach the surface and can be felt. through the skin. In front, the 

 anterior superior spinous process is easily to be recognized ; a portion of it is subcutaneous, 

 and in thin subjects may be seen to stand out as a prominence at the outer extremity of the fold 

 of the groin. In fat subjects its position is marked by an oblique depression amongst the sur- 

 rounding fat, at the bottom of which the bony process may be felt. Proceeding upward and 

 outward from this process, the crest of the ilium may be traced throughout its whole length, 

 sinuously curved. It is represented, in muscular subjects, on the surface, by a groove or fur- 

 row, the iliac farrow, caused by the projection of fleshy fibres of the External oblique muscle 

 of the abdomen. It terminates behind in the posterior superior spinous process, the position 

 of which is indicated by a slight depression on a level with and on each side of the spinous 

 process of the second sacral vertebra. Between the two posterior superior spinous processes, 

 but at a lower level, is to be felt the spinous process of the third sacral vertebra (see page 164). 

 Another part of the bony pelvis which is easiry accessible to the touch is the tuberosity of the 

 ischium. situated beneath the gluteal fold, and, when the hip is flexed, easily to be felt, as it is 

 then to a great extent uncovered by muscle. Finally, the spine of the os pubis can always be 

 readily felt, and constitutes an important surgical guide, especially in connection with the sub- 

 ject of hernia. It is nearly in the same horizontal line with the upper edge of the great tro- 

 chanter. In thin subjects it is very apparent, but in the obese it is obscured by the pubic fat. 

 It can. however, be detected by following up the tendon of origin of the Adductor longus 

 muscle. 



Surgical Anatomy. There is arrest of development in the bones of the pelvis in cases 

 of extroversion of the bladder ; the anterior part of the pelvic girdle being deficient, the bodies 

 of the pubic bones imperfectly developed, and the symphysis absent. The pubic bones are 

 separated to the extent of from two to four inches, the superior rami shortened and directed 

 forward, and the obturator foramen diminished in size, nan-owed, and turned outward. The 

 iliac bones are straightened out more than normal. The sacrum is very peculiar. The lateral 

 curve, instead of being concave, is flattened out or even convex, with the ilio-sacral facets 

 turned more outward than normal, while the vertical curve is straightened. 1 



Fractures of the pelvis are divided into fractures of the false pelvis and of the true pelvis. 

 Fractures of the false pelvis vary in extent : a small portion of the crest may be broken or one 

 of the spinous processes may be torn off, and this may be the result of muscular action ; or the 

 bone may be extensively comminuted. This latter accident is the result of some crushing vio- 

 lence, and may be complicated with fracture of the true pelvis. These cases may be accom- 

 panied by injury to the intestine as it lies in the hollow of the bone, or to the iliac vessels as 

 they course along the margin of the true pelvis. Fractures of the true pelvis generally occur 

 through the horizontal ramus of the os pubis and the ascending ramus of the ischium, as this 

 is the weakest part of the bony ring, and may be caused either by crushing violence applied 



1 Wood. Heath's Dictionary of Practical Surgery, i. 426. 



