Normal Parturitioti 521 



the mare, there may be some sweating. The pain is somewhat 

 intermittent and after each uterine contraction, which is of 

 variable length but which rarely exceeds two or three minutes, 

 there is a pause in the pain and anxiety until another period of 

 contraction comes on. As the uterus is an unstriped muscle 

 organ, its contractions are more or less slow, are virtually in- 

 voluntary and, like other contractions of this type of muscle, are 

 rythmic and recur at more or less regular intervals. The uterine 

 contractions are almost wholly involuntary, but may be indi- 

 rectly modified by fear or other emotions. As soon as the fetal 

 membranes pass into and beyond the os uteri, the expulsive 

 efforts of the animal increase in force and the full power of the 

 abdominal and other muscles of the body is brought into play in 

 a supreme effort to bring about the expulsion of the fetus. 



When the labor pains become fully established, the animal 

 assumes varying attitudes, somewhat according to the species 

 and individual. Our larger domestic animals alternate between 

 the standing and recumbent positions during labor, while multi- 

 parous animals lie almost continually and chiefly in lateral re- 

 cumbency. The larger afainials, when standing, arch the back, 

 bring all the feet together and strain violently. This straining 

 is aided materially by the animal taking a deep inspiration of 

 air, closing the glottis so that the air cannot escape from the 

 chest, and then powerfully contracting the muscles of the body, 

 increasing enormously the intra-abdominal pressure and tending 

 to force the contents of the abdomen in the direction of least 

 resistance. With the contractions of the uterus, this force is 

 concentrated chiefly upon the fetus and its envelopes, and forces 

 them toward and through the dilated os and out through the 

 vagina and vulva. 



Herbivorous animals do not constantly maintain a given posi- 

 tion during labor, but vary their attitude somewhat according 

 to the progress of parturition and partly according to indi- 

 vidual temperament. During the earlier stages of the act there 

 is' a greater tendency to maintain the standing position, than 

 later. When the fetus has been well propelled into the pelvis 

 and the anterior feet and head have passed beyond the vulva, 

 there is a very marked tendency, in the cow and mare, to as- 

 sume the recumbent position, and the animal may lie either in 

 the sternal position, or prone upon the side, in lateral recum- 



