PRESENTATION OF THE VERTEX. 301 



presents parallel to the greatest diameter of the pelvis. Although 

 Madame Boivin states on the one hand that she has met with it six 

 times in twenty-five thousand five hundred and seventeen cases, on 

 the other, Madame Lachapelle affirms that it is never met with. 

 These contradictory assertions at least prove that the situation of 

 the head at the commencement of labor has not always been recog- 

 nised with certainty at the Paris Maternite. And how could it be 

 otherwise? By the confession of all practitioners, it is very often 

 impossible, previously to the rupture of the membranes, to tell 

 whether the occipital fontanel is in front or behind, and o fortiori 

 whether it is to the right or left, rather than in the middle of the 

 strait. Now, it is probable that Mesdames Boivin and Lachapelle 

 could, themselves, have touched each of these thirty-six thousand 

 women before the head had engaged in the excavation? To con- 

 clude, although it be true that the occipito-pubic position, three very 

 authentic cases of which are mentioned by Dr. Dewees, is of very 

 rare occurrence, it is not less true that we are not, in the present 

 state of the science, authorised to deny its possibility; and as its 

 mechanism is not altogether the same as that of the occipito-aceta- 

 bular positions, I think it right to say a few words in regard to it. 



739. When at the superior strait, the occipito-mental diameter 

 and the occipito-bregmatic circumference are placed as in the two 

 first positions, and always correspond to the axis and plane of that 

 opening; but the bi-parietal diameter is situated transversely, and 

 the occipito-bregmatic from front to rear, instead of being parallel to 

 the oblique diameters; the pivot movement is not necessary and does 

 not take place; the direction of the various axes of the head is the 

 same at the end as at the commencement of the labor; as the shoul- 

 ders look towards the iliac fossae at the commencement, it is uncertain 

 which way the act of restitution will take place; in fact, there will be 

 none, because there was no previous act of rotation; however, as it 

 is a rare occurrence for the shoulders not to place themselves one in 

 front, and the other behind, before they pass through the inferior 

 strait, the occiput, after a few moments of indecision, turns to the 

 right or left, but without our being able to know beforehand which; 

 after that, there is nothing peculiar in the rest of the labor. 



740. Remarks. It cannot be denied that these three positions are 

 in fact but shades of each other. In all three cases the head begins 

 by flexing itself strongly down upon the breast, and ends by extend- 

 ing itself as it passes out under the arch of the pubis; the occiput, a 

 projecting part that always comes out first, never has more than two 

 inches, or at most, two inches and a half to pass over before it 

 reaches the arch of the pubis, and in escaping from the pelvis, it 

 27 



