Period of Heat 193 



brane, and dies. Opening into the vagina at its lower 

 surface, close to the vulva, is a small tube, the urethra, 

 which connects with the bladder, and through which 

 the urine is discharged. This is mentioned particularly 

 because, in passing probes or other small instruments 

 into the vagina, they should be directed toward the 

 upper part of the vagina, to avoid passing them through 

 the urethra into the bladder. 



When an ovum, or egg, is discharged from an ovary 

 into the fallopian tube, it is attended by certain symp- 

 toms of nervous or sexual excitement, and an abnormal 

 discharge of mucus from the vagina. To this period, 

 the term "heat" or "rutting" is commonly applied 

 by stockmen. During this period, the female is desirous 

 of sexual intercourse. If intercourse takes place and 

 conditions are favorable, the ovum or egg is fertilized 

 by the male cell and, instead of passing out and dying, 

 remains in the uterus, to the wall of which it becomes 

 attached. It develops into a young animal of the same 

 species, except when animals of different species are 

 crossed, in which rare instances a hybrid is the result, 

 as, for example, the mule. The period of heat varies in 

 different animals, about as follows: 



Mare Once in three weeks 



Cow Once in three weeks 



Ewe Once in sixteen days 



Sow Once in three weeks 



Bitch Once in six months 



These dates refer to the average time that elapses from 

 one period of heat to another, providing pregnancy 

 does not occur. 



M 



