PATHOLOGY OF PREGNANCY AND PARTURITION 441 



promontory ; the funnel-shaped pelvis and the pelvis of male 

 type, which is deeper and narrower transversely than the usual 

 female pelvis. 



To these must be added pelvic deformities secondary to 

 some pathological condition. By defective development of the 

 two wings of the sacrum, and ankylosis of both sacro-iliac joints, 

 the pelvis of Robert is produced (Fig. 212) ; Naegele's pelvis is 

 formed by ankylosis of one sacro-iliac joint and imperfect 

 development of the wing of the sacrum on that side, producing 

 a narrow slanting cavity. Asymmetry of the pelvis, with con- 

 traction of one-half, may result from unequal development of the 

 transverse processes of the lower lumbar or first sacral vertebrae ; 

 or the pelvis may be narrowed by the excessive growth of cer- 

 tain bony projections 

 (ridges or processes) . 

 Two bone diseases, both 

 of them special forms of 

 inflammation, are speci- 

 ally unfavourable to the 

 proper development of 

 the pelvis. Rhachitis 

 produces either a dimi- 

 nution of the conjugate 

 diameter with a normal 

 or increased transverse 

 measurement, or a gene- FIG. 215. Pelvis in hip-joint disease. (Spath.) 



ral decrease in all diameters. Osteomalacia, on the other 

 hand, in which the bones are abnormally soft, causes a change 

 of shape which is due to the pressure of the body-weight from 

 above and on both sides. The promontory of the sacrum arid 

 the ilia are forced inwards and the symphysis forwards into a 

 peaked shape. Pelves with ankylosis of the sacro-iliac joints are 

 very rare ; deformities due to single or double hip-joint disease 

 (Fig. 215) are more common, whilst commonest of all are those 

 in which the contraction is due to curvature of the spine such as 

 kyphosis or scoliosis (Fig. 216). 



It is these contracted pelves which easily give rise to more or 

 less deep and extensive tearing of the perineum. 



Laceration of the perineum appears to be confined to human 



