44 
A Study of the Variations in the Female Pelvis 
Summary. The features brought out by this investigation are : 1. The 
variation in the size, shape, and type of the female American Indian pelvis as a 
whole. 2. The variation in the pelvic inlet and 3. outlet. 4. The variation in 
the number of sacral vertebrae. 5. The frequency of a false promontory. 
1. The variation in size of the normal female pelvis is considerable, as is 
illustrated in Plate I, 1. 
The shape of the pelvic cavity also varies much, as is suggested by Plate II, 2, 
comparing a flat inlet with a rounded one ; and Plate VII, 9 contrasting a wide 
outlet with a narrow one. 
The "male" type or high, narrow-arched pelvis is shown in Plate III, 3, com- 
pared with the "female" or extremely shallow, broad-angled pelvis. The "male" 
type suggests a birth canal with a small bore, long cylindrical cavity ending in a 
narrow-arched small outlet. The effect on the mechanism of labour is to increase 
its difficulty proportionately. 
The determination of the sex of a pelvis is not always easy, and in a small 
percentage (perhaps 1 to 3 °/ 0 ) of cases is next to impossible, even with the aid 
of the whole skeleton. The breadth of the great sacro-sciatic notch was found 
to be the most reliable guide. The acuteness of the sub-pubic angle was next in 
usefulness. The thickness of the bones and finally the skull and long bones 
were referred to in doubtful cases (10). No specimen was included unless deter- 
mined by these signs to be female. 
2. Considerable variation is seen in the diameters of the inlet. Michaelis (11) 
reported 1,000 cases carefully studied as to pelvimetry and the results of labour. 
Litzmann(12) continued the work, reporting a second 1,000 cases. The standard 
determined by these men has been accepted throughout the world. Litzmann (12) 
considers all pelves contracted if the conjugata vera is 10 cms. or less in a generally 
contracted pelvis, and 9 - 5 cms. or less in a flat pelvis. By this standard my series 
of Indian pelves show 63 "contracted pelves," or 29 %> as follows: — 
Generally contracted 9 to 10 cms. 
6 
Flat 9 to 9-5 cms. 
43 
8 to 8-9 „ 
1 
„ 8 to 8-9 „ 
11 
„ 7-5 to 7'9 „ 
2 
A pelvis was classed " generally contracted " if the transverse diameter was 
less than 12 cms., at least one centimetre below the average: with, at the same 
time, an obstetric diameter of 10 cms. or less. A pelvis was considered "flat" 
if the transverse diameter measured 12 cms. or more with the obstetric diameter 
9'5 cms. or less. 
Three only of the seven generally contracted pelves showed the inter-cristal 
and inter-spinous diameters reduced more than 1*5 cms. below the average, and 
thus might be said to "suggest" lateral contraction within normal limits. The 
other four showed no such suggestion of contraction. 
