FACE PRESENTATIONS. 



73 



It will therefore be seen, from this explanation, that face presenta- 

 tions are deviations from those of the vertex. From this circumstance 

 some authors make the same number of positions for them as for 

 vertex presentations ; others again make four, corresponding to the 

 four oblique positions of the vertex, while some enumerate the same 

 number, disposing them transversely, and from front to rear, ad- 

 mitting a right mento-iliac and a left niento-iliac, a niento-'puhic 

 and a mento-sacral position. These positions having all been esta- 

 blished, it is proper that they should be mentioned. It seems ad- 

 visable, however, to simplify as much as possible, and accordingly 

 the number has been reduced very generally to two. 



First position. — Forehead to the left ilium, or left acetabulum, 

 and the chin to the right ilium, or right sacro-iliac junction, the 

 bridge of the nose representing the line described by the sagittal 

 suture in the first vertex position. (Fig. 18.) 



The second position. — Forehead to the right acetabulum, or right 

 ilium, and the chin to the left ilium, or left sacro-iliac junction. 

 (Fig. 19.) The first 



position is a deviation Fig- 19. 



from either the first or 

 fifth position of the ver- 

 tex ; the second, from 

 the second or fourth. 



Mechanism. — In the 

 first position the right 

 side of the face is an- 

 terior, and therefore 

 more depressed than 

 the other on entering 

 the brim, and the finger 

 touches the right eye 

 or zygoma first, on 

 making an examina- 

 tion ; if the labour is a 

 long one, this part of 

 the face is swollen and 

 livid. The face comes 

 down transversely, with 

 the bi-malar, or rather 

 the bi-temporal dia- 

 meter, in coincidence 



with the antero-posterior of the superior strait, and the fronto-mental 

 with the transverse. As the head is forced down into the excava- 

 tion, extension first becomes as great as possible, then the chin 

 rotates upon the right anterior inclined plane until it gets under the 

 arch of the pubes ; while the anterior fontanelle glides in an opposite 



T 



