912 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



evidenced simply by greater uneasiness, leaving the flock and seeking the 

 ram, and will only then permit the act of copulation. The same remarks 

 also appty to the goat. The sow at this time appears to grunt more than 

 usual, is more irritable and more vivacious, is restless, may bite, and 

 shows loss of appetite. Heat reaches its maximum in twelve to sixteen 

 hours. In the bitch there occurs a great hypersemia of the genital parts 

 and an abundant exudation of bloody mucus. The vulva is congested 

 and swollen, and the animal is much more lively and vivacious than usual 

 and playful, especially with dogs which are attracted from a great dis- 

 tance by the peculiar odor of the discharge. 



In all the domestic animals the phenomena of heat have a longer or 

 shorter duration. In the mare they last from two to three days ; in the 

 cow, from fifteen to thirty hours ; in the sow, from one to three days ; in 

 the sheep, from two to three da}-s ; in the goat, from two to three days, 

 and in the bitch, from nine to fourteen days. 



If conception occurs the phenomena of heat only make their reap- 

 pearance after delivery. In the cow this occurs in three to four weeks 

 after delivery, and recurs every three weeks if impregnation does not 

 occur. In the mare heat may appear from five to nine weeks after 

 delivery, and, if impregnation does not occur, every nine days afterward. 

 So long as the sow is suckling phenomena of heat do not appear, but 

 after the removal of the young heat comes on about the third day, and, 

 if impregnation does not occur, recurs every nine or twelve days. In 

 the sheep, after delivery, heat occurs in from three to four weeks ; when 

 suckling only two to four months later, and recurs at intervals of from 

 seventeen to twenty-five days. The mare is in heat usually in the spring 

 and again in the autumn; the goat in the autumn; the sheep in the 

 autumn and spring, while the other animals are in heat at intervals 

 throughout the entire year at the intervals already mentioned (Strebel). 



The occurrence of menstruation and heat coincides with the ripening 

 of an ovum. In the human female, as in the mare and cow, one ovum or, 

 at the most, two ripen at one time ; in the goat, from one to four, while 

 in the dog and cat as man}^ as ten ova may mature together. 



Through an increase of the blood pressure in the vessels of the 

 ovary blood transudes into the interior of the Graafian follicle, and thus, 

 by increasing the pressure, causes a rupture of the wall at its thinnest 

 point, and the ovule, together with the proligerous disk and the follicular 

 fluid, escape into the abdominal cavity. The ovary lies free in the 

 abdominal cavity in a fold of the peritoneum. As the ovule escapes from 

 the ovary the Fallopian tube, and its fimbriated extremity, is found, from 

 its state of congestion, in a condition of erection, and in all probability 

 the fimbriated extremity becomes closely applied to the ovary. As a con- 

 sequence, the ova escaping from the ovary fall within the mouth of the 



