To withdraw the instrument, it is tilted forwards, and the space which separates the point of the paper from the top of the spatula, is the sacro pubic interval, and to obtain this diameter we have simply to deduct the thickness of the pubes, and this may obviously readily be obtained by the instrument.
Pinard has joined to pelvimetry, pelvigraphy, which enables us to re produce on paper the measurements of dried pelves. According to him, " in normal as well as in pathological pelves, the shortest diameter is that which extends from the promontory to a point situated .1 to .2 inches above the upper border of the symphysis, or a little higher, and not the sacro-pubic distance as is generally admitted in France. This diameter he calls the minimum or useful diameter. To attain his aim, Pinard uses two metallic blades, very supple, and yet capable of retaining the curve given to them. They are .39 inches broad, and .039 inches thick. They suffice to obtain the contour of the posterior wall of the pelvis, from the tip of the coccyx to the last lumbar vertebra, and also the imprint of the anterior and posterior surfaces of the pubes. By tracing the shapes thus given to the blades on paper, if we have also by the compass taken the position of the sacrum and the pubes, we obtain graphic outlines, repre senting the natural size of an antero-posterior section of the pelvis that is to say, giving both the sacro•sub-pubic, and the least diameter of the pelvis. The figures 100 to 109 represent a certain number of outlines thus obtained." Scheffer, from measurements on dried pelves, draws the following con clusions in regard to the dimensions of the transverse diameter of the superior strait. His measurements concern 252 pelves: 1. The greater the distance of the iliac crests, the greater the neces sary deduction in order to obtain the transverse diameter of the superior strait. The mean difference is 5.07 inches.
2. The greater the distance of the iliac spines, the greater must be the deduction in order to obtain the transverse diameter of superior strait. The mean is about 4.70 inches.
3." In non-flattened pelves, the distance between the iliac crests fur nishes more precise information than that.between the iliac spines.
4. In flattened pelves, the distances between crests and spines are of about equal value.
5. To obtain the transverse diameter, we must deduct from the distance between the crests 5.2 inches, in the dried not flattened pelvis, and 4.5
inches in the flattened.
6. The deduction from distance between iliac spines is about the same in both pelves, about 4.7 inches.
Dohrn reminds us that if we consider as contracted pelves those where the conjugate vera is less than 3.6 inches, then: With all authorities, Dohrn prefers digital mensuration, with two fin gers, over all pelvimeters. On the living, to find the true conjugate, 4 inches is to be deducted from the external, in the normal pelvis; 3.8 inches, in the uniformly contracted pelvis; 4 inches in the flattened pelvis.
Litzmann usually measures only the external conjugate and the trans verse. But, while Baudelocque deducted 3.12 inches in thin women, and 3.32 in fat, Litzmann, in 30 cases, found a mean difference of 3.71 be tween the internal and external conjugates, and ho concludes that when ever the external conjugate, in the living, is less than 6.25 inches, there is contraction in the conjugate Vera; and that with an external conju gate of 7.05 inches, contraction will exist in 50 per cent.; between 7.05 inches and 8.39 inches, scarcely in 10 per cent.; above 8.39 inches, almost never.
As for the transverse diameters, ho found in 200 women with large pelvis, distance between crests, 11.5 in.; in 200 women with large pelvis, distance between spines, 10.5 inches.
The difference between the dried and living pelvis is about .4 inches. As for the oblique diameters, he could draw no exact conclusions. Kiistner's Pelvimeter. (Fig. 110 and 11 l.)—This instrument is at the same time a kaligraph. It is composed of a solid plane curved in a half circle to rest on the iliac crests. It is furnished with a metallic half-circle divided into two portions of 90° each, the zero being at the centre. On this half-circle is fixed the arc of a circle (three-quarters) also divided into degrees. The half-circle is fixed, the three-quarter is movable around a vertical axis (a.) Around the half-circle moves a lever (d), furnished with an index (See Fig. 110) which registers the divisions of the three quarter circle. The lever is divided into two portions, between which is a circle of 90°. The tree lever bar (g) is hinged at h so that it may bend at an angle of 60°. On the plane are two hooks, i, to which rubber bands may be attached, and at the two ends are two silk bands. Figure 110 represents the apparatus reduced.