D. H. DB Sotjza 
501 
differences for the two pelves are given in the last column. In future calculations 
the numbers in this column are used to indicate the effect of moisture on the 
different measurements. It follows that, in the moist pelvis, all the diameters 
and the heights of the hip bones are slightly greater than in the dry pelvis. 
(5) The thickness of the soft parts. 
We have been unable to find any very satisfactory record of the thickness of 
the soft parts of the pelvis. The soft parts affect our calculations. An internal 
diameter such as the obstetric conjugate measured on the tissue-clothed pelvis 
must be less than it would be if measured on the moist bony pelvis, by the 
thickness of the tissues over the sacrum and pubes. An external measurement 
such as the height of the hip bone is greater on the living subject than on the 
moist pelvis by the thickness of the tissues above the iliac crest and over the 
ischium. The thickness of the tissues which increase the height of the hip bone 
as well as that of the tissues over the ilium in the inter-cristal diameter have 
been most kindly measured for us by Dr Derry on twenty adult female post- 
mortem subjects in the manner already described. The details of these measure- 
ments will be found in a table at the end of this paper. The averages only are 
given here. 
TABLE VIII. 
Inter-cristal diameter 
Thickness of tissues in this diameter jleft^ 
Ischio-iliac diameter ... ... ... ||g|^ 
Thickness of tissues above crest of ilium j 
Thickness of tissues over ischium ... 
28-63 
•34 
36 
49 
62 
47 
47 
49 
■47 
The inter-cristal diameter on the living subject is therefore greater than that 
of the moist bony pelvis by "70 cm., that being the combined thickness of the 
tissues on the two sides. The ischio-iliac diameter, i.e. the height of the hip, 
is greater on the living subject by *47 + '49 or '96 cm. on the right side, and 
•47 + '47 or - 94 cm. on the left side. 
The tissues over the promontory of the sacrum and the posterior surface of 
the pubes were not measured. They are almost negligible. Two diagrams drawn 
to scale and most generously placed at our disposal by Prof. Symington show the 
differences for a thin and fat subject. In Fig. 1, Plate XXVIII, the median 
section of a rather thin woman 35 years old, the tissues over the promontory 
measure 2 mm. while those over the pubes cannot be measured on account of the 
distended bladder. In Fig. 2, Plate XXIX, showing the left half of the median 
section of the pelvis of a rather fat woman 30 years old, the tissues over the pro- 
montory measure 6 mm., over the pubes 4 mm., i.e. less than over the promontory. 
Biometrika ix 64 
