304 NATURAL EUTOCIA. 



sacrum, the coccyx and perineum, which resist so as to force it to 

 move forwards, the breast engages in the excavation, shdes in some 

 measure behind the face, opposes the turning of the chin towards 

 the centre of the pelvis, and makes it very difficult for the occipito- 

 mental axis to become parallel with the central line of the inferior 

 strait, and especially with the axis of the vulva. The vertebral 

 column being too much curved loses a part of the power impressed 

 upon it by the womb; as it presses upon the head at an angle which 

 becomes more and more acute, it cannot urge it onwards with the 

 same degree of energy, even although the same degree of force 

 might be em.ployed. 



The pivot movement takes place, nevertheless, and the forehead, 

 or the bregma, sliding along the left anterior inclined plane, comes 

 from left to right, and from behind forwards, to place itself under 

 the arch of the pubis, whilst the vertex, or occiput, moving upon the 

 right posterior inclined plane, proceeds from before backwards and 

 from right to left, into the hollow of the sacrum; but this rotation 

 is effected with some difficulty, because the forehead is too wide to 

 adapt itself accurately to the sub-pubal notch; because, beneath the 

 superior strait, the lateral regions of the hinder half of the pelvis are 

 made up of soft parts, which do not repel the head with sufficient 

 force towards the median line; lastly, because the extremities of the 

 occipito-frontal diameter and its circumference, and not those of the 

 occipito-bregmatic, roll in inverse directions upon the planes of the 

 excavation, as is the case in the occipito-anterior position. 



745. Notwithstanding so many unfavorable circumstances, the 

 occiput descends, by bearing strongly upon the sacrum, the coccyx, 

 and perineum, and the foetus finally passes the strait. In this situa- 

 tion it is upon the posterior commissure of the vulva, and not upon 

 the inferior edge of the symphysis pubis, that the occipito-bregmatic 

 diameter now presses, slides, and reverses itself from above down- 

 wards and from before backwards; so that the posterior fontanel, 

 the sagittal suture, the anterior fontanel, the parietal protuberances, 

 the frontal protuberances, and the several parts of the face, are seen 

 to appear in succession in front of the perineum. As soon as the 

 chin is disengaged from the summit of the pubic arch, the act of 

 restitution takes place; the face inclines towards the left groin, and 

 the occiput towards the right sub-ischiatic notch; the left shoulder 

 proceeds in front, under the symphysis; the right shoulder reaches 

 the concave surface of the sacrum; the head, governed by the move- 

 ment of the trunk, places itself crosswise; and the rest of the labor 

 is concluded as it is in the right occipito-acetabular position. 



