ANATOMY AND PREGNANCY. 



229 



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

 the elephant to 28 days in tlie rabbit. Tlic cow carries young- 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. 



Most important. — (a) Abortion; (b) retention of the foetus; 

 (c) volvulous (twist in the neck of the uterus). 



FIG. 82. BOVINE FOETUS AND FOETAL MEMBRANES AT MID-TERM. 



Uterus opened on the right side, exposing foetus ar.d membranes. Note 

 the small, li.ght-colored bodies (cotyledons) which connect uterus and mem- 

 branes. See also Fig. 83. A, uterus; B, cervix (neck of uterus). 



(a) Abortion. — For the purpose of this lecture, abortion 

 may be defined as any premature birth. 



They are either (i) sporadic, or (2) infectious. 



( 1 ) Sporadic abortions may be due to a great variety of con- 

 ditions ; e. g., sudden change in the weather and exposure to cold ; 

 strong medicines, especially purgatives; mechanical injuries; sud- 

 den and unaccustomed exercise ; extreme nervous excitement ; dis- 

 eases accompanied by cough or severe pain or high fever; ergot, 

 smut, etc., on the food; water containing sewage; disease of the 

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



(2) Infectious abortion is probably due to a distinct conta- 

 gium ; i. e., to the action of living germs upon the uterus and pla- 

 cental membranes. Certain conditions of the atmosphere, diet, 

 and vitalitv mav favor the outbreak. 



