PRESENTATIOXS OF THE FCETUS. 



'241 



is considored in this respect, because it is the most important in practice, 

 unil the position may be altered either spontaneously or artificially 

 iluring labour ; indeed, this alteration has often to be effected by the 

 obstetrist in order to render birth possible. 



SECTION I.— rilESENTATlONS. 



The presentation results from the part of the fa^tus which first offers 

 itself at the pelvic inlet — that re^'ion of the young creature which the 

 hand of the obstetrist immediately meets on being passed into the os, 

 and which is directly opposite the inlet. In this sense the head, fore 

 feet, hind feet, croup, etc., are said to be presented, according as one or 

 other of them first offers itself on exploration. 



These presentations are extremely varied, as any part of the foetus 



Fig. 72. 



Normal Position oi- the Kams i.\ tub Make at rARTURiTiON (Second Stage). 



a. Allantoic ; b. Amnion. 



may occupy this situation ; though so far as description and compre- 

 hensibility are concerned, their study can be greatly simplified. As 

 Hainard says: "The futus, when covered by its envelopes, is oval 

 shaped, or like an olive which it is desired to pass down the neck of 

 a bottle, and which may be presented to this in three ways — either by 

 one of its two ends or by its middle." These ends are the anterior 

 part of the chest in front, and the croup behind ; and it is these parts 

 on which the classification of the presentations is based. This classi- 

 fication gives two lonfjitudinal, or an anterior and posterior presentation ; 

 and as the foetus may also offer itself across the long axis of the 

 uterine cavity, we have a transverse presentation, which may again be 

 dorso-linnbar or sterno-ahdominal, according to the side of the fcRtus 

 which presents. These four fundamental presentations are, therefore : 

 1. Anterior Presentation. — The chest of the foetus presents towards 



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