632 Veterhiarv Obstetrics 



and position, or otherwise overcome the obstacles to birth. The 

 chief operations or manipulations b)' which it is hoped to correct 

 the position or attitude of a fetus are repulsion, rotation, version 

 and extension. 



A. Repulsion or retropulsion of the fetus con.sists of push- 

 ing it backward, or away from the pelvis, toward the diaphragm, 

 in order that it may be returned into the abdominal cavity, and 

 contemporaneously into the uterine cavity, where space is avail- 

 able for changing the position of the various extremities or of 

 the entire body. It is necessitated by the fact that the pelvic 

 canal is so narrow, and so completely filled by the fetus when it has 

 once entered, that there is little or no room for carrying out any 

 extensive changes in the attitude of the fetus, and consequently 

 it must be repelled or pushed away from this narrow channel 

 into a more commodious cavity, where ample room may be 

 obtained. 



While considering the various obstetric instruments and their 

 uses on page 595, we have described the methods for producing 

 repulsion. 



B, Rotation. It has already been stated that, in order for a 

 fetus to pass readily through the birth canal, it must offer in the 

 longitudinal presentation and the dorso-sacral position. When 

 presenting otherwise, it is desirable, if not necessary, that the 

 fetus be rotated upon its long axis until it is brought into the 

 dorso-sacral position, and its expulsion or extraction thus facili- 

 tated or rendered possible. 



The rotation of the fetus upon its long axis is naturally most 

 practicable when its body is lying within the abdominal cavity, 

 because, when it is advanced into the pelvic canal, it is exceedingly 

 difficult to bring about such a rotation owing to the limited room. 

 In accomplishing rotation it is to be borne in mind that a fetus 

 entering the birth canal in any other than the dorso-sacral posi- 

 tion is in an unstable attitude and tends to rotate to the proper 

 position, except as prevented by the firm impaction of the fetal 

 body in the narrow channel. 



The aim of the obstetrist is to aid these natural forces as far 

 as possible in accomplishing the object desired. First of all, the 

 body of the fetus should be pushed away, if possible, into the ab- 

 dominal cavity, while its limbs are retained in the pelvic canal, 

 as levers, through which the rotation may be largely accom- 



