True conjug., estimated, 11 cm. Left diagonal, 22 cm. Between Trochanters, 31 cm. Circumference of Pelvis, 90 cm. An accurate measurement of the pelvis by means of the pelvimeter will disclose any change in shape or size of the pelvis, indicate the degree of the deformity, and thus influence the treatment. The measurements are made externally and internally between certain bony prominences. The varying factors in the external measurements to be taken into consideration are the thickness of the skin, subcutaneous tissue, and the bones. Estimation of the Size of the Inlet.—An approximate idea of the transverse diameter is gained by measuring externally between the anterior superior spinous processes of the ilia (26 cm.); between the crests of the ilia where they are most widely separated (29 cm.); between the two trochanters (31 cm.). The transverse diameter may be determined more accurately by an internal measurement called the internal ascending oblique (Löhlein). This is measured, by the finger in the vagina, from the centre of the sub-pubic ligament to the upper anterior corner of the great sacro-sciatic foramen. The transverse is 2 cm. longer than this diameter. An idea of the length of the antero-posterior diameter of the inlet is derived from the external conjugate, measured from the depression under the spine of the last lumbar vertebra to the upper edge of the symphysis (204 cm.). The internal measure- / ment for estimating the antero-posterior diameter is made by the fingers reaching from the middle of the sub-pubic ligament to the top of the promontory, and is called the internal conjugate diagonal (12 cm.). This diameter is necessarily longer than the true conjugate, and it has been found that by subtracting 13 cm., the true conjugate is estimated. The possible sources of error in thus estimating the true conjugate are found in the fact that the internal conjugate diagonal does not take into account the height and angle of the symphysis, two factors which obviously influence the length of the true conjugate, while they have no effect upon the diagonal conjugate. Normally the height of the symphysis is 4 cm., and its angle 105° (conjugato-symphyseal angle). If this were always the case, subtracting 12 cm. from the measured internal conjugate diagonal would be absolutely correct. As a matter of fact, both the height and the angle vary, and by the following rules the true conjugate can be accurately determined. For every .5 cm. increase in the height of the symphysis above the normal, add .3 cm. to 12 cm., and subtract the sum from the measured internal conjugate diagonal. The converse of this is applicable to a decrease in height of the symphysis. For every degree of increase of the conjugato-symphyseal angle above the normal, add half that number of mm. to 12 cm., and subtract the sum from the measured internal conjugate diagonal. The converse of this is also true. The oblique or diagonal diameters may be measured externally from the posterior superior spinous process of the ilium to the opposite anterior superior spine (22 cm.). Estimation of the Size of the Cavity.-No external points of measurement. Its general size, or the presence of a tumor, is learned by a vaginal examination. Estimation of the Size of the Outlet.-As it is increased in many varieties of deformity, and but rarely contracted, external measurements are not required in the vast majority of cases. It is decreased in the kyphotic pelvis. The distance between the tuberosities of the ischia (11 cm.) is ascertained by Chantreuil's method: placing the two thumbs on the tuberosities, and an assistant measures the distance between them. Chief diagnostic points of the commoner forms of pelvic deformity. Simple Flat Pelvis.-The external conjugate will be less than 204 (19 or 18) and the internal conjugate diagonal less than 122. Flat Rachitic.-The external conjugate lessened (18 or under). Internal conjugate diagonal lessened (11 or under). Conjugatosymphyseal angle is increased; about 2 cm., not 13 cm., is subAtracted. The relation of the distances between the spines and crests is disturbed. These measurements in the ordinary type in this country will be about 25 and 26. Justo-minor.-All the diameters less, but normal relation main tained. Justo-major.-All diameters increased, but normal relation re mains. In private practice it is by no means necessary accurately to measure the pelvis of every pregnant woman. When, however, there exist evidences of some deformity, as rachitis, kyphosis, coxalgia, a history of grave difficulty in previous labors, etc., a vaginal examination should be made to estimate the conjugata vera, and other measurements taken as may be indicated. Bipariet. 11& 131 93 66 34" Occip. front. Occip. mental Trachelo-bregm. Circumference, occip., front. The weight of mature infant is 3250 grm, In connection with the size of the pelvis, a second important factor influencing the difficulty of labor is the size of the foetus, particularly of its head. Estimation of the Size of the Foetus. -An approximate idea of its size can be determined by abdominal palpation. When the head has not engaged, its relative size to the inlet, which is of obvious importance, may be discovered by an effort to push it through the superior strait. Anomalies of the Soft Parts. Anatomical anomalies of the maternal soft parts engaged in parturition may be the following: |