OCCIPITO-ANTERIOR POSITION. 475 



ever, in order to avoid them, it suffices never to make the instrument 

 penetrate beyond the parietal protuberances without being previously 

 assured of the position and state of the os uteri. 



1067. When we are sure that the left branch is well placed, an 

 assistant takes hold of it and keeps it in contact with the thigh while 

 the physician introduces the other. 



This one is to be taken in the right hand, and guided by the 

 fingers of the left, to the right side of the pelvis, or corresponding 

 sacro-iliac symphysis; to make it enter, we are to act exactly as 

 was just now directed, in speaking of the left branch. If the occi- 

 put is inclined to the left, we endeavor to move the blade forwards 

 behind the right thyroid foramen. If it be a right occipito-acetabu- 

 lar position, on the contrary, we leave it in front of the sacro-iliac 

 symphysis, while we endeavor to get the left branch behind the left 

 acetabulum. 



1068. In order to be able to unite the two branches of the for- 

 ceps, they must both be at the same depth in the pelvis; the mortise 

 in one must correspond exactly to the pivot in the other; their place 

 of crossing must not be more to the right than to the left, and their 

 handles must be sufficijently depressed. When the occiput is behind 

 the symphysis pubis, it is sometimes difficult to fix them exactly 

 upon the sides of the pelvis; they incline towards each other at their 

 convex edges, while their concave edges tend to separate, which 

 doubtless depends upon the head being no't so thick towards the 

 forehead as towards the occiput. This difficulty may be overcome 

 by taking a firm hold of the blunt hooks of the forceps, so as to use 

 them as a bent lever of the third kind, but we should be very sure 

 that the obstacle depends upon no other cause. By following this 

 precept, the concavity of the blades comes to be applied over the 

 paiietal protuberances when the occipito-frontal diameter is in line 

 with the sacro-pubic, and, in the oblique positions, the vertex is dis- 

 placed, and promptly directs itself to the top of the arch of the pubis. 



Further, it is evident that when the head is too firmly fixed, one 

 of the branches of the forceps will, under efibrts of this kind, resist 

 less than the other, and place itself under the corresponding anterior 

 inclined plane of the pelvis; so that the three occipito-anterior po- 

 sitions, so far, do not sensibly diffijr from each other as regards the 

 application of the instrument. The hand generally suffices to turn 

 the pivot, otherwise the kind of lever called the key of the forceps 

 is had recourse to. 



1069. In the next place, we ascertain that the head is the only 

 part embraced by the blades, and that the os uteri, the womb, or some 



