504 
The Measurements of the Pelvis 
With this large number of formulae to choose from there should be no difficulty 
in getting a very close approximation to the lengths of these two non-measurable 
diameters. Since the desire to attain an end with the least possible exertion is 
a weakness of human nature, the majority of those who favour these formulae 
with a trial will, no doubt, wish to use a single measurement, and especially one 
from which both diameters can be found. Such measurements are the antero- 
posterior diameter in (b') and (in'), and the height of the hip bone, right in (g 1 ) 
and (p), left in (h') and (q). They must not, however, expect such good results 
as the man who measures the diagonal conjugate and the inter-cristal diameter 
to obtain the obstetric conjugate from (a) or, more approximately, 
0 = -98D-l-68, 
and the transverse diameter from (k) or, more approximately, 
T=31K + 4-7l, 
With a little extra labour the height of the hip bone can be added to the list. 
If H represent the height of either hip bone in the living subject equations (i') 
and (j') may be combined to give approximately 
C = D - -05H -1, 
or C = (D-1)-^H. 
Similarly (?•') and (s') may be thrown into the combined form 
T = i(K+10) + ^(H + 10). 
We thus arrive at the following simple rules : 
(i) To find the obstetric conjugate subtract one-twentieth of the height of either 
hip bone from the diagonal conjugate diminished by one centimetre. 
(ii) To find the transverse diameter add one-quarter of the inter-cristal diameter 
increased by ten centimetres to one-tenth of the height of either hip bone increased by 
ten centimetres. 
(7) On the application of the formulae to the pelves of dwarfs. 
It is important to know what reliance can be placed on these formulae in 
cases of extreme pelvic deformity. In an article on " Dwarfism " by Rischbieth 
and Barrington (Treasury of Human Inheritance, Vol. I, p. 355, 1912) several 
measurements of dwarfs of various types are recorded. In nine cases measurements 
of the pelvis are given which include the diagonal conjugate, but in only four of 
these is the obstetric conjugate also given. The obstetric conjugate has been 
calculated from the diagonal conjugate for these nine pelves by means of the 
equation 
C = -98D + 1-68 
