182 



PELVIS. 



line of thoracic vertebra to the rigid side, and 

 is calculated to keep the line of the whole 

 spinal column in equivalent relation to the di- 

 rect and perpendicular line of gravity. It is an 

 interesting question, how far this common ten- 

 dency of the lumbar curve influences the po- 

 sition of the fcetal head, by affording more 

 room for the sinciput at the right sacro-iliac 

 joint, and determining its long axis in the left 

 oblique diameter, which is generally allowed 

 to be the most frequent presentation. In by 

 far the greater number of all kinds of pelvic 

 deformity that have come under my own ob- 

 servation, the projection of the sacral promon- 

 tory, when present, has been towards the left 

 side, showing the effect of a natural and previ- 

 ously existing tendency when the supporting 

 structures have been softened by disease. To 

 this subject I shall presently have occasion 

 again to advert. 



In these cases of partial distortion of the 

 pelvic brim, the cavity and inferior outlet are 

 generally roomy, shallow, and open. Often the 

 transverse or antero-posterior diameter of the 

 inferior outlet is larger than natural, and the 

 pelvis then approaches the condition of the 

 complete ovate deformity. An important prac- 

 tical result of this fact is, that in these defor- 

 mities of the brim all operations for extraction 

 of the foetus "per vias naturales" are facilitated 

 and rendered more successful. The obstruc- 

 tion being simply and only at the brim, when 

 that is overcome the rest is easy. 



Two examples of deformity of the brim are 

 recorded by Dr. Ram.sbotham. One is pre- 

 served in the Museum of the London Hospital 

 (see fig. 114.). The conjugate diameter of 



Fig. 1 14. 



Contraction of the brim of the pelvis. 

 (After Ramsbotham.') 



the brim measures 2f inches ; the transverse 

 5 inches ; and the distance from the side of 

 the sacral promontory to the centre of the su- 

 perior branch of the pubis on each side is 

 equal, and measures also 2f inches. Dr. 

 Ilamsbotham considers this to be just below 

 the smallest space through which the fcetal 

 head could pass entire. The cavity, however, 

 and the sacral curve, are well proportioned, 

 and the distance between the sciatic tuberosi- 

 ties 4f inches, or a quarter of an inch more 

 than in a healthy pelvis ; so that the foetal head 

 would pass easily, having overcome the ob- 

 struction at the brim. The second is the 

 pelvis of a woman who was delivered by cranio- 

 tomy, which is considerably contracted in all 



its diameters, but more especially at the brim. 

 The conjugate diameter is 2 inches only ; 

 the transverse 4f inches ; and while the dis- 

 tance from the right side of the sacral promon- 

 tory to the right pubic ramus is 2 inches, that 

 on the left side is 2^ inches only. The depth 

 of the cavity posteriorly is only 4 inches ; 

 the spines of the ischia project considerably 

 inwards, and the distance between the tubero- 

 sities measures only 3 inches. 



This author considers that a proportionate 

 increase in the transverse diameter does not 

 fully compensate for a great contraction in the 

 conjugate, in permitting the passage of the 

 fcetal head. In cases in which the brim is ob- 

 long, and presents a preponderance of the 

 antero-posterior diameter, as in the funnel- 

 shaped and masculine pelves, the foetal head 

 necessarily presents its long antero-posterior 

 diameter to that of the brim, and the case 

 may be one of face presentation. 



Distortions affecting the cavily only or prin- 

 cipally, and causing obstruction there to the 

 passage of the foetal head. These are occa- 

 sionally seen without particular deformity at 

 the brim or outlet. 



Vertical flatness of the sacrum, or want of 

 the proper vertical curvature, is occasionally 

 met with, according to Dr. Churchill, after 

 whom the annexed engraving of a specimen of 

 this deformity is taken (fig. 115.). This is 



Fig. 115. 



Flatness of the sacrum, and contraction of the pelvic 

 cavity. (After Churchill.} 



sometimes accompanied by an increased sacro- 

 vertebral angle. One or two instances I have 

 met with, in which there was a tendency to 

 this peculiarity. It is attended with diminu- 

 tion of the antero-posterior diameter of the 

 cavity, and is most frequently met with in 

 cases of general ovate deformity. 



The opposition it would offer to the passage 

 and circumvolution of the foetal head is evi- 

 dent. 



An inward projection of the sciatic spines 

 is often seen in connection with contraction of 

 the transverse diameter of the inferior outlet, 

 without any inordinate massiveness or mascu- 

 line form of the pelvis, as in the example be- 

 fore mentioned, and is, probably, sometimes 

 dependent on the same cause viz., the action 



