PRESENTATIONS OF THE SUPERIOR EXTREMITIES. 85 



of the child, as in presentations of the shoulders. As the mode of 

 proceeding is the same whenever the operation becomes necessary, 

 it will be described only in cases of sJtoulder jpieaeidations. 



PRESENTATIONS OF THE SUPERIOR EXTREMITIES. 



In almost all cases of this kind it is the shoulder which presents 

 itself at the superior strait, but it may happen that instead of a 

 shoulder, a hand or elbow may be prolapsed ; still, when they are 

 advanced to a certain degree, it is the shoulder which fills the strait 

 and presents the obstruction. The descent of the arm or hand add 

 nothing to the difficulty ; indeed it is rather serviceable, since it 

 assists us in our diagnosis, and does not at all interfere with the suc- 

 cessful termination of the labour. In this respect it differs from 

 breech presentations, in which the descent of the feet is altogether to 

 be avoided. 



In all cases of shoulder presentation the back of the child either 

 looks forwards toward the abdomen of the mother, or backwards 

 towards the spine; the former is'twice as frequent as the latter. 



It need hardly be said, that in the majority of such cases, the 

 delivery is impracticable except by art, although there are cases 

 reported of what is called spontaneous evolution^ in which the child 

 has righted itself, the arm and shoulders receding, and the breech 

 descending in its place, the labour being completed by the unassisted 

 efforts of the mother. 



Although spontaneous evolution inay take place, it is more con- 

 formable to the dictates of prudence and humanity to turn the child, 

 and bring down the feet, or restore the head to its proper place. 



Causes. — There have generally been enumerated but two great 

 presentations, viz., the cejoJtalic and pelvic, all others are but devia- 

 tions from these. As footling and knee presentations are deviations 

 from the breech, so are those of the shoulder from cephalic. Various 

 causes have been enumerated ; among them are particular positions 

 of the mother's body, inclination of the womb or of the straits of 

 the pelvis, sudden and irregular movements of the foetus, irregular 

 early contractions of the womb, and irregular distension. Dr. 

 Rigby concludes that the causes of arm or shoulder presentations 

 are of two kinds, viz., when the uterus has been distended by an 

 unusual quantity of liquor amnii, or when, from a faulty condition of 

 the early pains of labour, its form has been altered, and with it the 

 position of the child. 



Dr. Meigs looks upon obliquity of the womb as the great cause. 

 When the fundus falls over to either side, the action of the uterus is 

 oblique, the head, instead of engaging in the superior strait, strikes 

 against the brim of the pelvis, and glancing off from thence, is 



8 



