PRESENTATION OF THE FACE. 313 



also, it descends with one of the cheeks foremost, &c., and that 

 these anomalies constitute the varieties pointed out by Madame La- 

 chapelle; and which may be either primitive, that is, they may exist 

 from the very commencement of labor, or secondary, that is, not 

 become manifest until after the first efforts, and even at a very ad- 

 vanced stage of parturition; and that the last case ought to be con- 

 sidered as possible, for example, in vertex presentations with the 

 occiput backwards, or where the pelvis is very large, and also where 

 the sacrum is too concave. 



A. Right Mento-Iliac Position. 

 3d of Baudelocque, M.Gardien, Madame Boivin; 53 cases in 22,243, Madame 

 Lachapelle. 



762. In the right mento-iliac position, which evidently is a devia- 

 tion of the first or fifth of the vertex, and ought therefore to be, and in 

 fact is the most common (41 to 31; 58 to 45), the face comes down 

 transversely into the excavation; but as the length of the neck would 

 not allow the chin to get down to the level of the tuberosity of the 

 ischium without dragging the upper part of the thorax through the 

 superior strait, without throwing the occiput forcibly backwards on 

 to the chest, without putting the whole length of the vertical diame- 

 ter of the head, protracted as far as the sternum, into the situation 

 that ought to be occupied by the fronto-mental diameter, a rotative 

 movement soon takes place, and changes the relations of all these 

 parts: the chin and front of the neck slide from behind forwards upon 

 the right anterior inclined plane, and lodge in the top of the arch of 

 the pubis, while the bregma slides in an opposite direction, upon the 

 left posterior inclined plane, and proceeds to occupy the anterior 

 surface of the sacrum. Then the forehead, followed by the sagittal 

 suture and occiput, passes gradually down the plane presented to it 

 by the anterior surface of the coccyx and perineum, in front of which 

 all these parts are in succession disengaged. As it emerges from 

 the vulva, the chin rises, by degrees, towards the mons veneris, the 

 hyoidian region, or lower extremity of the vertical diameter, really 

 forms the centre of the semicircle described by the head as it clears 

 the strait, and the rest of the labor terminates as in the corresponding 

 positions of the vertex. 



B, Left Mento-Iliac Position. 

 4th of Baudelocque; M. Gardien, Mesdames Boivin, Lachapelle, etc.; 31 to 

 41; 45 to 53. 

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