40 OF THE PELVIS. 



shape have been met with; scirrhus, fibrous tumors, &c. may also 

 be developed so as to interfere with parturition; but it must be 

 acknowledged that a majority of the faults of the excavation depend 

 upon too great or too small a curve of the sacrum. 



§. III. Faulty dii'ection of the Axes. 



100. Nearly all these faults of conformation change, to a greater 

 or less degree, the planes and axes of the pelvis. When the sacro- 

 vertebral angle projects too much towards the pubis, the hoUowness 

 of the lumbar region being necessarily augmented, it happens that 

 the angle between the spine and sacrum, instead of being one hun- 

 dred and thirty-five degrees, may yield only one hundred and thirty, 

 or even one hundred and twenty degrees; the axis of the superior 

 strait, therefore, inclines forwards, and approaches the horizontal 

 line; if the coccyx and the point of the sacrum, restrained by the 

 sacro-sciatic ligaments, are not drawn away by this see-saw, the 

 plane of the inferior strait is depressed to the level, or below the 

 level of the horizontal line, and may even become parallel to the 

 plane of the superior strait, which in some measure justifies the 

 opinion of Messrs Sosmmering, Carus, Naegele, &c., who think 

 that even in the natural strait the perineal strait inclines downwards 

 and not upwards. But this disposition, far from bringing the axis 

 of the apex of the pelvis towards the perpendicular, or, from inclin- 

 ing it backwards, as at the first glance might be supposed, carries it, 

 on the contrary, considerably in front, inasmuch as the anterior face 

 of the coccyx must determine its direction. When the pubis rises 

 and the promontory becomes obtuse, the axis of the superior strait 

 approaches towards the vertical line, and in some cases becomes 

 parallel to the axis of the trunk of the body; if, in this case, the pos- 

 terior wall of the excavation fails in being sufficiently concave, the 

 two pelvic axes may become parallel, although the plane of the in- 

 ferior strait be much inclined forward. This conformation, which 

 especially favors the laceration of the perineum, gives rise, during 

 labor, to difficulties that have not been sufficiently dwelt on in our 

 classical works, and to which M. Lobstein endeavored to direct the 

 attention of the profession in 1817. 



§. IV. Causes of deformities of the Pelvis. 



101. In order correctly to understand the causes of faulty con- 

 formations of the pelvis, it is right to study them as they act in in- 

 fancy, during puberty, or at the adult age. Until the sixth or seventh 

 year, they are very well explained by a reference to rachitis, which 

 is almost the only cause of them. The bones that are chiefly affected 



