Allowance for Obesity.

With women of about normal weight I have recorded the measurements as read from the pelvimeter, but for obesity I have usually de

A deduction of one-half or one centimeter from intercrest and interspinous readings is all the allowance I have made on account of obesity or very pronounced obesity.

Several years since I began and industriously continued to make and record the distance between the iliac crests, the anterior-superior iliac spines, and the sacrum and pubes, of almost all women who presented in obstetric or gynæcologic practice. A small percentage of the whole number of pelves were found by external pelvimetry or by other tests, to be more or less out of shape and sufficiently so to warrant me in classifying them as asymmetrical.

Having thus eliminated the pelves which were found to be unsymmetrical, I grouped all others in several distinct classes according to size. The first group embraced all pelves measuring 24 centimeters between the iliac crests. The second group included those which measured half a centimeter more, or 24.5 centimeters, between iliac crests. The third group measured 25 centimeters between iliac crests. The fourth group embraced those which measured 25.5 centimeters between iliac crests. The fifth group included all which measured about 26 centimeters between iliac crests; and so on until every pelvis to the extremes of size was placed in one or other of the several groups.

Having thus classified what I esteemed to be the pelves of normal conformation, I averaged the interspinous and external conjugate measurements for each class and assumed that, for theoretical and practical purposes, the results in any instance would afford me the two companion measurements for pelves of that particular group or class.

To show how this result was obtained, let us assume, for example that the different pelves, five in number, of one group and size, measured respectively about as follows:

External conjugate measurement.. 17.0 17.8 17.4 17.6 17.2

Addition of the interspinous measurements and division by the number of pelves of this class:

Interiliac spinous measurement of pelvis: No. 1, 23.0 cms.; No. 2, 23.2 cms.; No 3, 22.8 cms.; No. 4, 23.2 cms.; No. 5, 22.8 cms.; total, 115.0 cms.

One hundred and fifteen centimeters divided by five, the number of pelves of this class, gives us 23 centimeters, which is the average or composite interspinous measurement for the pelves of this group, and which measured about 25 centimeters between the iliac crests.

External conjugate of pelvis: No. 1, 17.0 cms.; No. 2, 17.8 cms.; No. 3, 17.4 cms.; No. 4, 17.6 cms.; No. 5, 17.2 cms. ; total, 87.0 cms.

Eighty-seven centimeters divided by five, the number of pelves in this group, gives us 17.4 cms., which is the composite or average external conjugate measurement for the pelvis in this 25 cm. group. You will thus see how, by grouping all normal pelves in relation to

size between iliac crests, I was able to obtain averages of the two other and companion measurements in every instance. With these results in hand I devised a chart which shows the companion measurements for pelvis of one or other of the dozen or more groups or sizes. We may also read from the chart what I deem to be the companion measurement of the direct internal conjugate, and also the transverse diameter at brim of pelves of any size.

Description of Chart.

The space between any two horizontal lines represents one centimeter, the figures at the left and the right, reading from zero, indicate the number of centimeters for antero-posterior or external conju

gate measurements.

The heavy line beginning at 16.5 centimeters to our left on the chart and terminating at about 22.4 centimeters on our right, I designate as the external conjugate line.

Near the top of the chart appears a progressive series of numbers any one of which may be utilized for an interiliac crest measurement. The lines which descend from these numbers terminate at the bottom of the chart, where another progressive series of figures indicate the several companion measurements between the anterior superior spinous processes of the ilium.

The heavy line running obliquely across the chart from II centimeters upon our left to 15.3 centimeters upon our right, indicates the transverse diameter at brim, according to the point at which it may be intersected by any particular line in interest, thus:

A pelvis of normal conformation measuring 29 centimeters between iliac crests would measure 14 centimeters transversely at superior strait, and would measure 25.8 centimeters between iliac spines, and 20.7 centimeters over sacrum and pubes.

The heavy line running obliquely across the chart from 9.5 centimeters on our left to 13.1 centimeters on our right indicates by its intersection with any vertical line the companion direct internal conjugate of any pelvis in interest.

To make practical use of the chart, let us assume that we have examined a pelvis and find it to measure 27 centimeters between iliac crests. We follow the descending line underneath 27 centimeters to to bottom of the chart, and there we read 24.5 centimeters, that being the companion interiliac spinal measurement. Observe the point at which the descending vertical line just referred to intersects the broad and inclined external conjugate line, and follow the horizontal line from that point to its termination at the left or right of the chart, and we there read the companion external conjugate diameter for a pelvis measuring exactly 28 centimeters between crests. It is 19 centimeters.

Another Illustration.

A pelvis presents with an external conjugate of 21 centimeters. Let the eye follow the horizontal line from the figures 21 at either the left or right side of the chart to its intersection with the external inclined conjugate line; from that point follow the vertical line to the top of the chart and read the companion intercrest measurement, which is 29.5 centimeters, and to the bottom of the chart to ascertain the companion interiliac spinous measurement, which is 26.1 centimeters.

Another Example.

If a pelvis presents with an interiliac spinous measurement of 23 centimeters, follow the vertical line upward to its intersection with the external conjugate line, and you will find that the companion external conjugate measurement should be about 17.4 centimeters. Follow the vertical line to the top of the chart, and it terminates at 25, that being the companion interiliac crest measurement for a pelvis with an interiliac spinous measurement of 23 centimeters.

As one uses the chart a little he naturally acquires the habit of reading between the lines, and he soon imagines that he measures so accurately that he begins to find, for example, a pelvis whose interiliac crests are neither exactly 27.5 centimeters nor 28 centimeters, reading from his pelvimeter during application 27.7 centimeters. He looks at the chart and, finding no such interiliac crest in figures, imagines a line to descend two-fifths of the way between the 27.5 and 28 centimeters; that it intersects the external conjugate line at about 19.5 centimeters, and that his imaginary line descends to the bottom of the chart, where he estimates that the companion interiliac spinous measurement would be about 25 centimeters.

Asymmetrical Pelves.

If, in the mensuration of a pelvis, any one of these three companion measurements is found to be very much less or greater than the indications of the chart, we must feel fully warranted in the presumption of asymmetry. In such instances two of the diameters depart widely from the standard. The following from my collection of asymmetrical pelves illustrates this:

Case A.-Before craniotomy. Crest, 29 centimeters, iliac spines, 29 centimeters; external conjugate, 19 centimeters.

At autopsy, when post-mortem symphysiotomy was performed, the following internal diameters were taken: Direct internal conjugate, 6.3 centimeters; transverse, 13.8 centimeters.

In this case the increased distance between the iliac spines afforded most pronounced indication of asymmetry.

Very often only one diameter departs materially from the indications of the chart, and is illustrated by the following from my collection of ill-formed pelves:

Case B.-Crest, 27 centimeters; iliac spines, 22.5 centimeters; external conjugate, 17.5 centimeters.