OBSTETRICS 257 



tween the uterus and vagina the connection or common open- 

 ing is through the neck of the uterus, properly the cervix. At 

 this point the uterus narrows greatly and is composed of firmer 

 tissue, especially in the cow. As the time for delivery ap- 

 proaches this narrow canal is dilated until the opening is large 

 enough for the young animal to pass through. 



Normal period of gestation. — This varies from two years in 

 the elephant to 30 days in the rabbit. The cow carries young 

 about 283 days; mare, 345 days; sow, 119 days; ewe, 149 days. 

 All these may vary greatly. Old animals usually carry longer 

 than young. 



Accidents of Pregnancy 



The most serious accidents of pregnancy are : abortion, reten- 

 tion of the fetus, and volvulus (twist in and near the neck of 

 the uterus). 



Abortion. — For the purpose of this lesson, abortion may be 

 defined as any premature birth. 



Abortions are either sporadic or infectious, usually the latter. 



Sporadic abortions may be due to a great variety of condi- 

 tions ; e.g., death of very weak embryos ; strong medicines, espe- 

 cially purgatives; mechanical injuries; sudden and unaccus- 

 tomed exercise ; extreme nervous excitement ; diseases accom- 

 panied by cough or severe pain or high fever; disease of the 

 uterus and lack of constitutional vigor in either sire or dam. 



Infectious abortion is an exceedingly serious disease. The 

 actual abortion should be considered as merely one of several 

 serious symptoms of the disease. See "General results." It is 

 due to contagium; i.e. to the action of living germs upon the 

 uterus, fetus, and placental membranes. 



Infectious abortion, unlike hog cholera, does not spread rap- 

 idly through a herd. Cases usually come at irregular intervals 

 throughout the season until a large percentage of the herd may 

 have aborted. See next Lecture. 



Symptoms. — Symptoms of approaching abortion depend on 

 the stage of pregnancy, and are frequeiitly obscure or even 

 lacking if the abortion occurs very early. Sometimes there is a 

 discharge from the vagina and its mucous membrane may be 

 deeply congested. Slight labor pains sometimes appear several 

 hours before the fetus is expelled and before the sac is rup- 

 tured. Occasionally the animal may be noticed moving around 



