104 CATTLE-BREEDING. 



tendency and it shows a large number of the 

 forms which this tendency will take. For in- 

 stance, decreased fecundity, impaired fertility, 

 (the difference between these should be kept 

 well in mind; the sow above named in her 

 failure to breed to a related boar showed im- 

 paired fertility; her dam when she produced 

 her, one pig at a litter, showed decreased fe- 

 cundity) disease of the procreative organs in 

 frequent births of dead young, transmission of 

 weak organisms seen in the idiocy and incapac- 

 ity of some of the young, and so on. Over against 

 these things are set the case of an extraordi- 

 narily superior animal in form and appearance. 

 These fine animals have been produced again 

 and again by such a course, but nearly always 

 at a cost analogous to that witnessed in the 

 case of this sow. 



We have perhaps had enough examples to 

 see the theory and the experience of breeders 

 in applying in-and-in breeding. It may be 

 briefly summed up as follows: 



The theory of in-and-in breeding rests first 

 on the view that the way to obtain the best 

 cattle is to select the best obtainable animals 

 and breed them and their offspring together 

 over and over again, thus maintaining their 

 excellencies free from the intermixture of any 

 less excellent blood, and making by constant 

 interfusion the blood of all the animals iden- 



