THE POSTERIOR LIMBS. 133 



behind ; it has for base the sacrum, which presents on each side of the median 

 line the subsacral foramina. This part is also called the sacral plane, or roof of 

 the pelvis. 



The inferior region, or ischio-pubic plane, is formed by the pubes and the 

 ischial bones. It is concave from side to side ; its anterior border is nearly 

 straight, and its posterior border is scooped out by a wide notch to form the arch 

 of the ischium. 



It has been remarked by Goubaux, that the portion of this plane correspond- 

 ing to the pubis presents numerous varieties. The superior face of the pubis 

 may be convex in its anterior moiety, and concave in its posterior ; or it may be 



Fifr. 87. 



PKLVIS OF Tllli MARE. 



ooncave before and convex behind, the concavity being separated from the 

 convexity by a transverse ridge. This ridge is sometimes represented by a series 

 of small conical eminences ; at other times this upper face is disposed as a 

 smooth inclined plate, directed backwards and upwards, and a kind of rim 

 surmounts the anterior contour of the oval foramen.^ 



With regard to the lateral faces, they are formed by a small portion of the 

 inner face of the iliac bones, and in great part by the sacro-sciatic ligaments. 



The foetus must pass through the pelvic canal during parturition ; it is, 

 therefore, important to know at any time if the female pelvis is of sufficient 

 dimensions to allow the foetus to leave it. Pelvimetry is the name given to 



' It is necessary to be aware of the frequency of these asperities on the floor of the pelvic 

 cavity, in order not to arrive at false inductions when exploring the bladder per re,etum. 



