SUCCESS IN POULTRY CULTURE 
super-family of birds, without the danger 
that follows the practice of introducing 
new blood from outside, and, for the most 
part, from unknown sources. And this 
position gives me a great advantage over 
those who seek to improve their flocks by 
line-breeding a single family, because the 
most careful line-breeding with a single 
family of birds soon merges into an in- 
breeding proposition; and it is on account 
of this inbreeding proposition that so 
many breeders find it necessary to seek 
new blood from outside sources to build 
up the vitality and fertility of their de- 
clining flocks. If they had gone to Nature 
and studied her ways and practiced what 
she taught them, they could have built up 
the vitality and fertility of their flocks 
without having had to suffer the disap- 
pointment that almost always follows the 
introduction of new blood from partly or 
wholly unknown sources. 
The reason that there is so much 
danger from introducing new blood from 
outside sources is because the different 
strains of the same breed are bred by 
different men and are not all bred under 
the same environment and by the same 
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