OF THE PELVIS. 25 



join tlie tendon of the pyramidalis in the digital cavity of the great 

 trochanter, and by the pudic vessels and nerves which re-enter the 

 pelvis to be distributed in the perineum. 



42. Suppose a vertical cut, which should divide the lesser basin 

 into four equal parts, there would be found four planes inclined to- 

 wards each other at their points. The two anterior inclined planes 

 comprise a portion of the lateral regions and the whole of the ante- 

 rior region of the excavation; the two posterior are formed by the 

 front of the sacrum and coccyx, by the sciatic ligaments and notches, 

 and the sacro-iliac articulations. It is always on two of these four 

 surfaces that the extremities of the diameters of the foetal head glide, 

 during parturition. 



§. III. 8trait§ of the Pelvis. 



43. A. Superior strait. The sort of horizontal circle which 

 separates the internal surface of the pelvis into two parts, is called 

 the superior or abdominal strait, greater strait, or margin of the 

 pelvis: formed behind by the sacro-vertebral angle and the anterior 

 edge of the lesser wings of the sacrum, outwardly by the rim which 

 limits the iliac fossa below, in front by the superior posterior edge 

 of the body of the pubis; it is thick or rounded in the first portion 

 described, while in the second it, on the contrary, grows thin, and 

 is transformed, so to speak, into a crest. 



44. Its form in the dried pelvis approaches more or less to that of 

 an oval, of the heart on a card, or of an ellipse; but with the soft parts 

 it represents a triangle, with the base in front. 



45. Its inrJination downwards and forwards, when the woman is 

 on foot, varies from thirty-five to fifty degrees. This inclination is 

 less in the silting posture, and Avhen the person lies down or bends 

 forwards; it increases in pregnant women, in those who make use of 

 their abdomen to support heavy burthens, as is the case at Paris with 

 the women who sell fruit, vegetables, fish, &;c.; also while on the 

 knees; and whenever, for the purpose of preserving the equilibrium, 

 we attempt to throw the upper end of the central line of the body 

 backwards. 



46. Its axis is an imaginary line extending from the umbilical 

 region to the lower two-thirds of the front of the sacrum. Every 

 degree of inclination of which the plane of the strait is susceptible, is 

 equally applicable to its axis, since the latter must pass through the 

 former. The upper extremity of this may rise higher or fall lower, 

 according as its lower extremity recedes from or approaches towards 

 the point of the coccyx. In this respect there are infinite shades of 

 difference, which must not be lost sight of in practice, whether the 



