78 THE LAW OF BIRTHS AND DEATHS 



apply to maiden mares only ; those which have dropped 

 a foal are generally put to the horse nine or ten days 

 afterwards, when almost every mare is in season. For 

 this reason, valuable thorough-bred mares are often sent 

 to foal at the place where the sire stands who is intended 

 to be used next time. 



" The mare then remains to be tried at intervals of 

 nine or ten days, and when she is stinted the foal is strong 

 enough to stand any length of journey with impunity." * 



We have here recorded a fact which is noticeable with 

 most breeds of domesticated animals. The maiden 

 mare is a " very uncertain " animal. That is, she does 

 not always come into season at the proper time, and 

 when in season is apt to be very difficult to impregnate. 

 When, however, a mare has dropped a foal, and has 

 suckled the hungry youngster for nine or ten days, it is 

 seldom that much trouble is experienced in getting her 

 to conceive. Why ? On the hypothesis under discussion 

 it will be because the drain on the mare's resources will 

 have diminished her nervous energy. 



Cattle yield much the same evidence as horses. It 

 is an interesting commentary on Herbert Spencer's 

 theory that a condition of plethora is favourable to fertility 

 that, after the first calf, cows are usually served when 

 in full milk. A good milking cow in full milk is usually 

 all points and angles. It is this condition which is most 

 favourable to fertility ; high condition being notoriously 

 unfavourable. 



Darwin says of sheep : " The amount of food affects 

 the fertility of the same individuals ; thus sheep which 

 on the mountains never produce more than one lamb 

 at a birth, when brought down to lowland pastures 

 frequently bear twins. This difference apparently is not 



1 The Horse in the Stable and in the Field, Stonehenge, chap. xi. 



