This gives local families a chance to produce a carefully selected breed of goat and raise them at home to produce more milk.

这让当地家庭有机会生产经过精心挑选的山羊品种，并在家中饲养它们以生产更多的牛奶。

And as it is not likely that man should have succeeded in selecting so many breeds and sub-breeds with constitutions specially fitted for their own districts, the result must, I think, be due to habit.

由于人类不太可能成功地选择出这么多具有​​特别适合其所在地区的体质的品种和亚品种， 所以我认为， 结果一定是由于习惯所致。