ANATOMY AND PREGNANCY. 229 



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

 the elephant to 28 clays in the rabbit. The 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 and membranes. Note 

 the small, light-colored bodies ("cotyledons) which connect uterus and mem- 

 branes. See also Fig. S3. A, uterus; B T cervix (neck of uterus). 



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

 may be defined as any premature birth. 



They are either (1) 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 vitality may favor the outbreak. 



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