42 Vetcri7ia>y Obstc fries 



meet with mares breeding annually for ten, twelve or more con- 

 secutive years. 



Neither do all animals born reach maturity. Their j^rowth 

 and development afterbirth is predicated upon the available food 

 supply and their immunity from predatory animals and from 

 di.seases and accidents. Speaking generally we might safely say 

 that in the wild state the probabilities of maturity are in inver.se 

 ratio to the rapidity of reproduction. In those which reproduce 

 slowly, like the mare, with less than one young per annum, which, 

 in turn, needs live about three years before giving birth to young, 

 the new-born animal is born in a well matured state and is 

 quickly able to travel long distances for food or water and to 

 flee rapidly from pursuing predatory animals and enjoys, in addi- 

 tion, highly efficient maternal protection. On the other hand, 

 the young of the rabbit are born in a state of utter helplessness 

 against enemies or of procuring food independently, while the 

 mother is not competent to afford effective protection against 

 foes. Thus, in a state of nature, where there is neither room nor, 

 food for all the young which might be born, agencies which 

 modify the birth rate and the percentage of young which shall 

 successfully mature serve to maintain a balance in animal life. 



The rapidity of the increase of a species is also modified by the 

 available nutritive surplus of the mother. Generally speaking 

 the larger the animal the lower the nutritive reserve. The 

 greatest drain upon the nutritive supply is that upon the muscles 

 for locomotion. Large animals need move over a more extensive 

 area in order to obtain sufficient food and, the greater the body, 

 weight, and, especially, the greater the height, the greater the 

 drain upon the nutritive supply within the body. 



Among domesticated animals, where food and protection are 

 provided by man, the control of the numbers of animals is brought 

 about through such agencies as slaughtering the immature ani- 

 mals for human food (ruminants and swine), the direct control 

 of numbers by killing the surplus new-born (carnivora), castra- 

 tion and the prohibition of breeding by sexual segregation. 



The maintenance of nutrition of the body of the parent must 

 necessarily take precedence over the reproduction of young, and 

 the latter be limited constantly by the nutritive reserve within 

 the parent after the neces.sities for her own existence have been 

 supplied. The drain upon the maternal system in the reproduc- 



