38 
A Study of the Variations in the Female Pelvis 
It may be seen from this table that # 200 with inter-cristal diameter over 
2 cms. broader than 1162, yet has a narrower transverse diameter. Again #112, 
with a transverse diameter practically identical with #30 and #143, has an inter- 
cristal diameter 3"6 cms. greater. By these extreme differences we are forced to 
conclude that accurate estimates of the transverse diameter of the inlet cannot 
be deduced from inter-cristal and inter-spinous diameters. 
Since we cannot measure satisfactorily the transverse diameter in the living, 
we are therefore forced to adopt for obstetric use some such rough rule as 
Williams (7) gives as follows : — " Despite many inaccuracies, the external measure- 
ments are of considerable value, in that they serve to indicate with tolerable 
certainty the variety of pelves (contracted) with which one has to deal. Normally 
the distance between the spines is 2 - 5 to 3 cms. less than between the crests : 
but in rhachitic pelves, owing to the flaring of the iliac bones, this proportion 
becomes deranged, and the two measurements approximate one another in length, 
the former frequently being equal to, and occasionally exceeding, the latter. If, 
however, both measurements are considerably below the normal, but preserve their 
usual relation to one another, and at the same time the external conjugate is 
also shortened proportionately, it is permissible to conclude that the entire 
pelvis measures below normal in all its diameters, or, in other words, is generally 
contracted." The following summarising table of these measures may make the 
results of this series more graphic : — ■ 
Inter-cristal 
Freq 
Inter-spinous 
Freq. 
Transverse of Inlet 
Freq. 
20-8 to 21-9 cms. 
2 
17-2 to 18-9 cms. 
2 
10 3 to 10-9 cms. 
2 
22 to 23-4 „ 
10 
19 to 20-9 „ 
28 
11 to 11-9 „ 
14 
23-5 to 24-9 „ 
42 
21 to 22-4 „ 
67 
12 to 12-9 „ 
71 
25 to 2(5-4 „ 
88 
22-5 to 23-9 „ 
67 
13 to 13-9 „ 
108 
26-5 to 27-9 „ 
59 
24 to 25-4 „ 
44 
14 to 14-7 „ 
22 
28 to 29-1 „ 
16 
25-5 to 27 „ 
9 
Average 25 - 76 cms. 
Maximum 29-1 ,, 
Minimum 20 - 8 ,, 
22 - 66 cms. 
27 
17-2 „ 
difference 3'1 cms. 
6-75 „ 
1 
12 - 95 cms. 
14-7 „ 
10-3 „ 
While the average difference between the inter-cristal and the inter-spinous was 
3'1 cms., the variation between the extremes (1 to 6 '75 cms.) of this series free 
from disease is wide and would tend to indicate that little reliance could be 
placed on deductions from such a comparison. 
_ . • t 7 obstetric conjugate (vera) x 100 
superior strait Index = — - — r . , 
1 transverse diameter 
average 79'5, maximum 107 - 7, minimum 61"5. 
These data were considered sufficient to give as accurate a measure of the inlet 
