ANATOMY OF THE TIIREE-TOED SLOTH. 175 



diameters, the shape of cross- sections of some of the bones, the 

 sizes of openings, and the development of crests and eminences. 

 Speaking generally the female pelvis is rounder and more capacious, 

 for it has to accommodate the large trumpet-shaped rectum, and 

 leave a passage for the foetus during parturition. 



For purposes of measurement I have chosen the following 

 diameters which are made use of in human obstetric anatomy, 

 but have modified them slightly : — 



1. Conjugate — from the centre of the inner boi'der of the pubis 

 to the front of the centrum of the first sacral vertebra. 



2. Transverse — between the widest points of the lateral pelvic 

 walls ; that is between the inner surfaces of the acetabula. 



3. Oblique — from the sacro-iliac joint to the mid point of the 

 bone between the mid line in front and the anterioi- border of 

 the obturater foramen. 



4. Intersjjinous — between the iliac spines. 



5. The measurements of the outlet are taken between the 

 widest points dorso-ventrally and transversely. 



The proportions present in male and female pelves are as 

 follows : — 



Diameters. Male pelvis. Female jjelvis. 



Interspinous diameter 9"8 cm. lO'l cm. 



Conjugate of inlet : 7*7 ,, 7-5 ■„ 



Transverse,, ,, 5*5 „ 6-8 „ 



Oblique ,, „ 7 „ 7-5 „ 



Conjugate of outlet 5*5 ,, 5*7 ,, 



Transverse,, „ 5 „ 5-8 „ 



Width of pubis 2 „ 2-3 ,, 



Ischiadic Foramina. 



Antero-posterior diameter 2'3 ,, 1'8 , 



Transverse ,, 1-6 ,, 1-3 ^^ 



Obturator Foramina. 



Antero-posterior diameter 1-6 ,, 1-7 



Transverse ,, 2-2 ,, 2-5 ,. 



The following difterences are also present between a male and 

 female pelvis : — 



Male pelvis. Female pelvis. 



Ischial tuberosities well marked. I Ischial tuberosities verv small. 

 Pubis circular on section. ' Pubis flat on section. 



Iliac spines incurved. j Iliac spines not incurved. 



Inlet less defined. [Inlet well defined by a sharp 



crest. 



Ischia more sloping from last i 



sacral vertebra. | 



Transverse px^ocesses of caudal Transverse process of caudal 



vertebrae sloping. vertebra^ horizontal. 



