PELVIS. 



181 



tion sometimes is present, and may mislead 

 the obstetrician by giving an apparent breadth 

 of haunch, while the contraction of the true 

 pelvis may be considerable. He considers it 

 to result from the entirely different and inde- 

 pendent development of the false and true 

 pelvis.* 



I have met with many specimens of the 

 masculine form of pelvis in the dissecting- 

 rooms, from among the laborious women of this 

 metropolis. In Dr. Murphy's experience it 

 is more common than had been hitherto 

 supposed. 



The obstruction in this form of pelvis is met 

 with chiefly in the deep funnel-shaped cavity, 

 at the'projecting ischial spines, or at the infe- 

 rior outlet, under the narrow arch, and be- 

 tween the tuberosities, and is rendered the 

 more serious by the foetal head in these 

 cases being generally more ossified than usual. 

 The great inward projection of the sciatic 

 spines sometimes affords an obstacle to the 

 passage of the head. The average normal 

 distance between them will be found, on refer- 

 ence to the tables, to be 4 inches. During 

 the turning of the head in the most frequent 

 positions, the inter-temporal and inter-zygo- 

 matic diameters of the foetal head, the former 

 of which is placed by Dr. Murphy at 3 inches, 

 and the latter at 3^ to 4 inches, are placed 

 obliquely between them. In one or two in- 

 stances I have found the sciatic spines as near 

 to each other as 3^ inches, and in one it was 

 not co-existent with any extraordinary massy 

 or masculine proportions, but simply with 

 small transverse diameters. In the fronto- 

 cotyloid and fronto-pubic positions, or with a 

 large foetal head, the approximation of the 

 sciatic spines becomes a serious impediment to 

 labour. In this pelvis the sacro-coccygeal 

 articulation is said by Dr. Murphy to be ge- 

 nerally less moveable, and the saero-iliac joints 

 unyielding, and that a bony ridge is often found 

 on the posterior surface of the narrow pubic 

 symphysis. 



The cause of this form of pelvis seems to be, 

 an advanced condition of ossification in a pelvis 

 which would otherwise have been "infantile" 

 brought about by the development of unusual 

 muscularity, corresponding to the laborious 

 employment of the individual. This action of 

 the pelvic muscles will have also the effect of 

 impressing irregularities upon the bones into 

 which they are implanted, or over which they 

 act. The tension of the posterior spinal and 

 abdominal muscles against those of the leg 

 would tend to elongate the pelvis, while the 

 powerful great glutei, much used in supporting 

 or raising heavy weights, will press inwards 

 the ischial tuberosities, and narrow the sub- 

 pubic arch. 



Irregularities of the pelvi-vertefoal angle. 

 Too great obliquity of the pelvis has been said 

 to cause "ante-version" by throwing the 

 weight of the uterus on the anterior abdomi- 

 nal walls ; and too little obliquity to have a 

 tendency to produce prolapsus uteri. Naeirele 

 (Das weibliche Becken), however, considers 



* Med. Gazette, voL xxxii. pp. 555. and 589. 



many of these supposed consequences are 

 theoretical only; but he observed, both in first, 

 and after many labours, that an approximation 

 of the pelvic plane to the perpendicular caused 

 the foetal head to be placed so much forward, 

 and the os uteri so high, as to be felt with, 

 difficulty ; and, on the other hand, in very 

 considerable inclination to the horizon the 

 foetal head was deep, and not easy to be felt 

 through the uterine neck. In neither condi- 

 tion was there any important deviation from 

 the mechanism of natural parturition. 



The alteration of the planes of the pelvic 

 outlets becomes, however, a valuable means of 

 indication of the more important class of pel- 

 vic distortions, in which such an alteration is 

 generally effected. In particular, when the tip 

 of the coccyx and pubic symphysis are un- 

 usually placed, especial attention to the form 

 and measurements of the pelvis is called for; 

 though, as before seen, an alteration of the 

 pelvic planes alone does not necessarily imply 

 a distorted pelvis. 



Dr. Rigby mentions, that the pelvic inclina- 

 tion is generally less in a tall slender person 

 than in a short thick-set woman ; and that, in 

 the former case, the hollow of the sacrum is 

 generally small, and in the latter deep. 



2. Distortions of the pelvis are best arranged 

 into the following practical divisions/according 

 as they affect the brim ; the cavity; or the 

 outlet only or principally ; or the whole struc- 

 ture of the pelvis at the same time.* 



Distortions affecting the brim only or princi- 

 pally.-^^y far the greater majority of these 

 cases consist in an unusually forward projection 

 of the sacral promontory. This causes the 

 opening to assume a heart-shape, diminishes 

 the conjugate diameter, sometimes contracting 

 also the oblique, and increasing the transverse 

 in some degree. At the same time, the pro~ 

 montory of the sacrum is sunk down below 

 its normal altitude, lessening the angle of the 

 superior plane y and making its axis assume a 

 more vertical direction. Most generally the 

 sacral projection deviates from the medium 

 line, and forms the lower extremity of an 

 abnormal curve in the lumbar vertebra, render- 

 ing the brim of the pelvis generally unsym- 

 metrical in shape. 



This deviation takes place most frequently, 

 according to my own observation, to the left 

 side, and appears to bean exaggeration of a very 

 common tendency (which, being seen in the 

 most robust subjects, can scarcely be called 

 abnormal) of the natural curve of the lumbar 

 vertebra towards the left side. This lateral 

 curve is evidently a compensatory one to the 

 very usual and well-known deviation of the 



* Osiander enumerates six forms of pelvic de- 

 formity, classified without regard to their origin or 

 bearing upon parturition ; viz. 1. The elliptical, 

 with diminished antero-posterior diameters, and 

 without projection of the sacral promontory; 2. The 

 reniform, with a sacral projection ; 3. The hourylass 

 or 8 shaped, from a curve backward at the sym - 

 physis pubis ; 4. The oblong ; 5. The oblique ; and 6. 

 the angular or triangular form. The method of ar- 

 rangement I have adopted in the text, seems 

 however, the best adapted for useful applications. 



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