OF THE PELVIS. 33 



which, with the iliac vessels, form a sort of column, extending from 

 the sides of the sacro-vertebral angle, to the linea ilio-pectinea, so 

 as in a considerable degree to contract the bis-iliac diameter, and 

 also to increase the inclination of the strait very much. Instead of 

 being elliptical, or representing an oval whose large extremity should 

 be turned backwards, this strait is now almost circular, or in the 

 shape of a triangle with the base forwards; the sacro-iliac notches 

 scarcely exist, and the sacro-vertebral angle is much less prominent 

 than is commonly supposed, from the idea formed of it upon inspec- 

 tion of the dried pelvis. 



73. From the researches to which I have devoted myself, and 

 whose results have been already made known, I find that the en- 

 trance of the pelvis is widest between the ilio-pectineal eminences: 

 at this point its transversal diameter is four inches and some lines, 

 while the bis-iliac diameter, properly so called, is only three inches 

 and a half to four inches. Beneath the promontory and the psoas 

 muscles, the transverse diameter is really five inches, and the con- 

 cavity of the sacrum gives quite as great a length to the antero-pos- 

 terior diameter. 



74. The bottom of the excavation is of a lozenge shape, with an- 

 gles corresponding on the one hand to the ischiatic spines, and on the 

 other to the middle line of the sacrum and posterior surface of the 

 pubic symphysis. These four angles indicate the place of union of 

 the four inclined planes, which thus represent four triangles, tending 

 to approach each other at their points. 



75. The sacral vessels and plexus, as well as the pyramidalis mus- 

 cle, are found in the posterior triangles: the anterior planes enclose 

 the internal obturator muscles and part of the levator ani. The 

 pelvic fascia is exactly applied over all these parts; an abundant 

 layer of cellular tissue, in which are imbedded the internal iliac ves- 

 sels, the hypogastric flexus and arteries, a layer which, by the de- 

 position of fat, sometimes becomes so thick as to diminish the cavity, 

 and thus render labor more difficult, lines the whole, and is separated 

 from the viscera by the intermediate peritoneum. 



§. IX. Tses of the Pelvis, 



76. The diflferent bony pieces which compose the pelvis are sus- 

 ceptible of only a very slight movement upon each other; notwith- 

 standing assertions to the contrary, the kind of sliding that takes 

 place between the sacrum and coxal bones, as well as between the 

 ossa pubis, in consequence of a fall upon the feet, for example, can- 

 not in any manner be compared to articular motion of whatsoever 

 species. 



4* 



