RECTIFICATION OF PRESENTATIONS AND POSITIONS. 487 



indeed, is not desirable ; for partial unconsciousness will allay the 

 excitement and abnormal straining, but -will not suspend the uterine 

 contractions. The chloroform may be inhaled from a piece of sponge 

 or lint placed in a basin or similar vessel and held under the animal's 

 nostrils, a blanket being thrown over the head to keep in the vapour ; 

 or the sponge may be laid at the bottom of a nose-bag put on the head. 

 The antf sthetic should be inhaled until the introduction of the hand 

 into the vagina or uterus no longer excites the severe straining. Partial 

 narcosis might also be tried in some dillicult cases of parturition in the 

 Cow, but then it must be remembered that in the event of slaughter 

 the flesh will have the odour of the drug. With the smaller animals 

 the production of this condition is often beneficial. 



We will now consider the principal mutation movements required to 

 effect a change in the position of the fcjctus. 



CHAPTER II. 



Rectification of Presentations and Positions of the Foetus. 



Wh have seen how numerous and varied are the presentations and 

 positions of the foetus, and how, in order to effect delivery, some of 

 these must be changed or modified ; this can only be done by moving 

 the fcctus itself, and so altering its relations to the adjacent parts of the 

 mother. These movements are sometimes designated mutations by 

 obstetrists, and the procedure necessary to effect them varies with 

 circumstances ; sometimes, for instance, the object may be achieved by 

 merely altering the position of the parturient animal, or by sustaining 

 its abdomen and manipulating externally ; but in the great majority of 

 cases it is necessary to introduce the hand into the genital canal, and 

 operate directly on the foitus. 



The pi-incipal of these mutation movements are four in number : 

 lictropulsion, Rotation, Version, and Extension and Flexion. 



In order, however, that these movements may be effected, certain 

 conditions are necessary. In the first place, it is essential that tlie os 

 uteri be sufficiently dilated, or relaxed and extensible, so that the hand 

 may reach the interior of the uterus ; next, the body of the fcctus must 

 be movable in the uterus — a circumstance not always noted, as the 

 organ is often contracted closely on the fcctus when the liquor amnii 

 has escaped, or the fa-tus itself may be fixed in the genital canaL 

 And, finally, the fcctal envelopes must be ruptured, as it is impossible 

 to manipulate the young creature effectively while it is entirely invested 

 by them. 



Before any alteration in the presentation or position of the foetus can 

 be accomplished, these conditions must be assured. 



Retrgpulsion. 



When the foetus, in a vicious position, has entered the pelvic cavity 

 and become fixed there, or even when in the uterus and approaching 

 the inlet, before the position can be corrected it is nearly always neces- 

 sary to push the creature forward again into the uterus ; as there only, 

 from the greater space this organ affords, and the elasticity of its walls, 

 can the impediment be overcome and adjustment effected. 



" Retropulsion " is often necessary during protracted labour, even 



