682 MAMMALIAN ANATOMY 



The interspinal diameter is the distance between the ischial spines. 



The width of the pelvis is taken at the following points : (1) maxi- 

 mum width at acetabula ; (2) between the outer edges of the ischial 

 tuberosities ; (3) at the anterior superior iliac spines ; (4) at the ante- 

 rior inferior iliac spines. 



The caudal angle is the angle formed by the meeting of the plane 

 of the symphysis of the pubes with a transverse plane passing through 

 the cephalic end of the symphysis and the caudal end of the sacrum. 



The cephalic angle is the angle formed by the meeting of the plane 

 of the symphysis with a transverse plane passing through the cephalic 

 end of the sacrum. 



VAEIATIONS IN FOKM AND DEVELOPMENT. 



The variations in the pelvis which depend upon the sex of the 

 animal appear to be very slight. They were studied upon male and 

 female pelves from which the soft parts had been removed with care 

 so that the sacro-iliac articulations might be undisturbed. As soon 



FIG. 526. 



FRONT VIEW OF A FEMALE PELVIS. 



1, last lumbar vertebra ; 2, intervertebral ligaments ; 3, sacrum, the figure being placed below its promontory ; 

 4, transverse Hues indicating the original separation of the sacrum into five vertebral segments ; 5, end of the 

 coccyx; 6, iliac fossa; 7,8, anterior superior and inferior spines; 9, acetabulum; 10, cotyloid notch; 11, body of 

 the ischium; 12, tuberosity of the ischium; 13, spine of the ischium, seen through the obturator foramen; 

 14, body of the pubes; 15, symphysis of the pubes; 16, arch of the pubes; 17, crest of the pubes; 18, spine of the 

 pubes; 19, pectineal line; 20, ilio-pubic eminence; 21, great sacro-sciatic notch. 



as the pelves had dried without distortion, they were bisected longi- 

 tudinally, and the halves embedded in plaster of Paris in such manner 

 that only the median surface was visible. From this surface, when 

 slightly ground and polished, prints were taken as from a wood- cut. 

 A few of these prints are given in Fig. 525. It will be noticed that 



