Resulting from this tardy development of the pelvis, the bladder and greatest portion of the rectum, in the child at birth, are con tained almost entirely in the abdominal cavity', on a level with the ilia or false pelvis, and only descend gradually afterward into their adult position with the slow development of the pelvic bones, assuming their pertnanent position about the period of puberty, a cir cumstance very necessary to be borne in mind in operations on these viscera in chil-. dren below that age. Hence one cause of the greater prominence of the belly in children from the additional number of its visceral contents.
According to Dupuytren, the female pelvis differs very little from that of the male till puberty, at which period it has a general triangular form in both sexes, but, after that period, it becomes rapidly developed, and soon assutnes its distinctive sexual cha racter. The transverse diameters begin to exceed the conjug,ate, and, in the female, attain a great preponderance, constituting one of the great characteristics of the fully formed human pelvis, as distinguished from that of the lower animals.
In Autenrieth's method of calculating the pelvic dimensions, the dorsal, or posterior part, bears a proportion to the anterior or abdominal part, as 10 to from 11 to 14, in the infant of two years ; while, in the adult pelvis, it was as 10 to from 16 to 22.
In advanced adult age, the pelvic inclination is said by Cruveilhier to be increased in con sequence of the forward curvature, or droop ing of the spinal column, which tends to arrive at the horizontal position, as in quadru peds. To keep the centre of gravity between the lo‘ter .extremities, the femurs, in old persons, are more flexed upon the pelvis, so as to be more directed towards the line of the superior pelvic plane. I have found, however, that in old subjects, although the angle of the pelvic plane with that of the whole spinal column is increased, yet the angle with the lumbar vertebrm only, is not so much changed, and that, apparently, the increased muscular traction on the sacrum and posterior part of the ilia by the muscles of the back act ing upwards, and of those of the front of the thigh acting downwards, upon the anterior part of the pelvic lever, in order to pre serve the erect position, produce this in creased obliquity- of the pelvis, which is ge nerally accompanied by a corresponding de crease of the sacro-vertebral angle. This will be more fully comprehended when consider ing the mechanism of the pelvis.