200 The Diseases of Animals 



through narrow doorways, kicks, blows or sudden 

 jumps from the use of the whip. During the later 

 stages of pregnancy, strong medicines, especially vio- 

 lent purgatives, should not be given. 



The period of gestation, or pregnancy, — that is, the 

 time which elapses between the fertilization of the egg 

 and the birth of the young, — varies in different animals 

 as follows: 



Mare ... . about 344 days, or eleven months ; mule colt, twelve months 



Cow .... about 280 days, or nine months 



Ewe . . . .about 152 days, or five months 



Sow . . . .about 112 days, or three and a half months 



Bitch. . . .about 63 days, or two months 



Pregnant animals frequently give birth to their young 

 sooner than the period indicated. If the young animal 

 is sufficiently developed to live, it is usually called a 

 premature birth ; if the fetus is not sufficiently devel- 

 oped to live, it is called an abortion. Pregnant animals 

 may also carry their young longer than the period 

 indicated. 



SIGNS OF PABTUEITION, OR APPROACHING BIRTH 



At the close of the period of gestation, signs of 

 approaching parturition usually appear. The mammary 

 glands become distended, the" vulva enlarges, and the 

 mucous membranes lining the vagina become congested 

 and red. In cows, the hip bones tip forward a little, 

 and a small depression on each side of the root of the 

 tail appears more marked. The cow is commonly said 

 to be "down in her hips." In mares, a waxy secretion 



