PRESENTATIONS OF THE PELVIS. 327 



the lowering of the chin; the occipito-bregmatic diameter, which is 

 three and a half inches long, not being able to place itself in corres- 

 pondence with the antero-posterior diameters of the excavation and 

 apex of the pelvis, has its place occupied by the occipito-frontal 

 diameter, which has an extent equal to at least four inches. The 

 face, and particularly the forehead, are too broad and ill-disposed to 

 fit the form of the pubic arch so exactly as the nape of the neck and 

 occiput do; finally, the shoulders hardly emerge before the chin pre- 

 sents itself at the vulva. 



Nevertheless, immediately after the expulsion of the thorax and 

 upper extremities, the upper and hinder part of the neck rolls from 

 before backwards upon the anterior edge of the perineum, as upon 

 an axis, and the nose, the forehead, the anterior fontanel and remain- 

 der of the head successfully disengage, by forcing the breast back- 

 wards. 



786. Remarks. The mechanism of this position, as now seen, is 

 very unfavorable, and much more difficult than that of the calcaneo- 

 anterior positions; if the chin or forehead lodge upon the upper edge 

 of the pubis, the act of flexion of the head is prevented or destroyed, 

 and the occipito-mental diameter, or the occipito-frontal diameter and 

 circumference, occupy the situation of the occipito-bregmatic diame- 

 ter and circumference; then the labor cannot be terminated without 

 assistance. 



It would, notwithstanding, be wrong to conclude that art must of 

 necessity aid the economy in all the posterior positions of the feet: 

 attempts to change them would favor the reversion of the head, and 

 most frequently produce just the state of things which it is desired 

 most carefully to avoid. Besides, nature, when left to herself, gene- 

 rally succeeds better than any foreign power in flexing the head and 

 placing it diagonally at the superior strait.* In a very great majority 

 of cases this position spontaneously converts itself into an anterior 

 position, either suddenly, after the head has got into the excavation, 

 or, on the other hand, gradually, in proportion as the hips, the shoul- 

 ders, and the head itself present. 



* The best position for the woman, in this labori is that on the left side, with 

 the thighs strongly flexed. As soon as the shoulders are delivered, the body of 

 the child should be turned back towards the woman's buttock, so as to give 

 greater facility to the flexion of the head. At the same time that the child is 

 pressed backwards, the edge of the perineum should be pushed towards the coc- 

 cyx, in order to let the nape of the child's neck retreat as far as possible. When 

 this can be done, a fing-er in the child's mouth will easily depress the chin, and 

 thus eftect the desired degree of flexion. I have succeeded in this way several 

 times without any difficulty. — M. 



