MECHANISM OF LABOUR. 63 



face turns towards the left groin, and the occiput towards the poste- 

 rior part of the right thigh of the mother. 



• The left shoulder rotates to the front under the symphysis pubis, 

 while the right falls into the hollow of the sacrum. 



M. Naegele states that this position is more common than the 

 second, and that rotation takes place from behind forwards, so as to 

 bring the occiput under the pubis, instead of into the hollow of the 

 sacrum, as already described. In this opinion he is confirmed by 

 Professor Meigs. 



In the ffth position^ the back of the child is directed to the left 

 and backwards, the right shoulder to the left and forwards, and the 

 left, to the right and backwards ; the bi-parietal diameter corre- 

 sponds with the left antero-posterior oblique, and the occipito-breg- 

 mitic with the right antero-posterior oblique diameter ; the lesser 

 circumference of the fcetal head, and the occipito- mental diameter, 

 are parallel with the plane and axis of the strait. Rotation of the 

 vertex takes place upon the left posterior inclined plane, into the 

 hollow of the sacrum, while the forehead, gliding upon the right an- 

 terior inclined plane, is brought to the symphysis pubis. 



After the birth of the head, restitution takes place, with the occiput 

 to the inside of the mother's left thigh, while the face looks towards 

 the right. This is said to be a more difiScult position than the pre- 

 ceding, in consequence of the presence of the rectum, which retards 

 the progress of the occiput. 



In the sixth position^ as in the third, there is neither rotation, nor 

 restitution ; the occipito-bregmatic diameter corresponds with the an- 

 tero-posterior, and the bi-parietal with the transverse. 



It is less favourable than the corresponding oblique positions, in 

 consequence of the liability of the forehead and face to be turned 

 downwards, and thus permit the long diameter of the head to be 

 brought into parallelism with the short diameter of the pervis. 



In all these occipito-posterior positions, there is much greater dis- 

 tension of the perineum than in the occipito-anterior, in consequence 

 of the head having to descend lower ; they are therefore more tedious 

 and painful. 



It is by no means an easy matter to diagnosticate the 'positions of 

 the vertex ; it requires great delicacy of touch, and considerable expe- 

 rience. The movements of the child, and the stethoscope, are valu- 

 able assistants to the sense of touch. Naegele observes that when 

 the movements are felt most on the right side, the head is probably 

 in \\\Q first position, when on the left, in the second. 



The stethoscope also informs us of the situation of the fcetal heart, 

 and when this is decidedly known, it becomes an easy matter to de- 

 fine the position of the head. 



