588 I'^eten'nary Obstetrics 



moving the fetus, although the presentation, position, fetus and 

 maternal pelvis were each apparently normal. 



The amount of traction. In passing through the birth 

 canal the fetus and the maternal parts in contact with the fetus 

 undergo an enormous pressure because of the comparative nar- 

 rowness of the canal. This pressure is to a great extent inevit- 

 able, and it is only when it becomes excessively high that it 

 has any danger for the fetus or mother. 



In veterinary practice we scarcely recognize the presence of 

 any danger whatever to the fetus from the pressure during its 

 passage through the birth canal, nor as a rule do we observe any 

 injury to the fetus because of traction applied to any of its ex- 

 tremeties. The amount of traction which will be boine by the 

 head or the limbs of a fetus during its passage through the canal 

 is astonishing. It far surpasses any point which an average per- 

 son would believe possible for the fetus to endure without more 

 or less serious injury, and yet, as a rule, strain or other in- 

 jury to the fetus from such traction is virtually unknown in 

 practice. 



The mother, however, not infrequently suffers seriou.sly from 

 severe, or rather we might say, from injudicious traction. How 

 much pressure the pelvis of our domestic animals will withstand, 

 when applied through the medium of a fetus impacted within its 

 canal, we do not know. Experimentally, it has required from 

 375 to 635 pounds pressure upon a round ball representing the 

 head of the fetus, to produce a fracture of the bones or disunion 

 of the pelvis of woman. 



The great danger to the organs of the domestic animal is not 

 to the bony, but to the soft parts, and it is these which are first 

 injured by an excessive pressure. 



The amount of traction which may be applied to the fetus 

 varies with its position. When the fetus is presenting normally 

 and the traction is exerted in the direction which we have sug- 

 gested, there is no point where the soft tissues of the fetus may 

 not move to some extent upon each other and thus relieve the 

 pressure upon a given point, so that in normal cases the pressure 

 of the fetus against the walls of the birth canal is well nigh equal 

 over the entire surface. 



When the fetus presents improperly, when an extremity is re- 

 tained in such a way that a greatly increased pressure is brought 



