28 OF THE PELVIS. 



ed towards the horizon without an equal or apparent degree of ele- 

 vation of the coccyx. The sacro-pubal diameter is increased, by de- 

 scending to the centre of the excavation, from six to ten lines, on 

 account of the concavity of the sacrum; the transverse diameter, on 

 the contrary, diminishes gradually as it approaches the ischiatic, 

 where it is only four inches. The oblique diameters alter but very 

 little, and I am ignorant of the facts that might warrant Mr. Meckel 

 in assigning to them a length of five inches and four lines. 



56. As the anterior face of the sacrum presents us with a cavity 

 that is irregular and of greater or less depth, it is easy to understand 

 that a series of right lines that should fall perpendicularly upon it 

 could not be parallel; that ihey would all converge towards each 

 other, and cross at angles more or less acute in front of the articu- 

 lation of the pubis, with the exception of one that would be exactly 

 horizontal. For the same reason, we may imagine that the plane 

 represented by each of these lines must have an axis as well as those 

 of the straits, and consequently, that we cannot refuse to admit an 

 axis of the excavation. The union of all these axes would give a 

 curve, concave anteriorly, and whose two extremes would be repre- 

 sented by the central lines of the superior and inferior straits. By 

 viewing the axis of the pelvis in this light, the accoucheur will always 

 have before him the direction of the plane of the anterior face of the 

 sacrum; of the coccyx, and even of the perineum; and as this is the 

 plane that directs the head of the foetus, such a mode of regarding 

 it seems to me more simple, and much more useful for practice, 

 than the method indicated by certain authors, and which is burthened 

 with geometrical formulas.* 



§. V. Base of the Pelvis. 



57. The great circumference or base of the pelvis looks upwards 

 and forwards. Its plane is parallel to that of the abdominal strait. 

 It is formed posteriorly by a notch, in the bottom of which is seen 

 the base of the sacrum, and which is naturally filled by the last ver- 



• tebra, the ileo-lumbar ligaments, and the quadratus iumborum mus- 

 cles; outwardly, by the superior edge of the coxal bone, which affords 



* Vide Deventer {Ohserv. Sur le Manuel des Accouchemens, 1734), who 

 appears to have been the first to indicate that the cavity of the pelvis is not paral- 

 lel to the axis of the body; Muller {^Collect, de Holler); Roederer (De axis pel- 

 vis, S(C. Gott. 1751); Smellie (Treatise on the Theory, Sfc. 1771); Levret (Art 

 des Accouchemens, 1766); Camper (Translation of Mauriceau, 1759); Stein (^rt 

 d^Accoucher, 1804); Lobstien (Bulletin de la Faculte de Medecine de Paris, 

 1815); Flamant (These de M. Guillemot, Paris, 1824, No. 164); Baker's Draw- 

 ing, and especially the learned Memoir of M. Neegele (Das Wiebliche Becken, 

 Sfc. Carlsruhe, 1825, and in Archives de Medecine, June, 1827). 



