328 A TREATISE ON HORSE-BREEDlNG, 



during the time of any subsequent period of evolution or 

 heat; and though there may, in such a case, bs two or more 

 foetuses developing within the uterus at the same time, they 

 cannot be regarded as twins or triplets, because their nat- 

 ural term of gestation terminates unequally, the difference 

 depending upon the length of time that passed between the 

 two different acts of conception; and, besides, if no acci- 

 dental or detrimental influences should occur during the 

 original term of gestation they would be born of two en- 

 tirely independent acts of parturition. Superimpregnation, 

 in its two forms, may occur after sexual connection with one 

 or with several males. The difference in time between the 

 two acts of parturition, in cases of superfoecundation, in re- 

 corded cases, has been from two to six months. 



HEAT DURING PREGNANCY. 



As a rule, when conception has taken place, the regular 

 periods of heat terminate, and do not reappear until after 

 parturition. But there are exceptions to this rule, and these 

 are due to the fact that during gestation an ovule may ma- 

 ture, and, as a consequence, heat will appear. This may 

 happen in all species of animals and during any period of 

 gestation. If during such heat sexual intercourse should 

 happen, conception may take place again, constituting su- 

 perf cec undation . 



LACERATION OF THE RECTUM. 



Occasionally reports have come to hand concerning cases 

 where, during the service of the stallion, the rectum became 

 lacerated. These reports invariably contained statements 

 of a fatal termination. While laceration of, the rectum 

 may happen during the normal performance of coition, it is, 

 however, more likely to occur when, as sometimes happens, 

 the penis enters the rectum instead of the vagina. Lacer- 

 ation of the rectum during coition may be considered as 

 incurable and generally causes death of the mare. 



ABORTION. 



The causes of abortion are numerous. Among these may 

 be mentioned qplic, violent external injuries, violent exer- 



