An Introduction to a Biology 



experiments plants and animals which multiplied as rapidly 

 as possible, and could be purchased and bred as cheaply as 

 possible. And it was reasonable to test the truth of Mendel's 

 theory by breeding mice and sweet-peas before applying 

 it to the improvement of live stock : because it was possible 

 that Mendel's rules might only have applied to the material 

 with which he worked — the culinary pea — and not have 

 been of general applicability at all. If breeders had started 

 to apply Mendel's rules to the improvement of their stock, the 

 loss of much time and money might have been the result 

 Thirteen years have now elapsed since Mendel's papers were 

 rediscovered, and since the testing of his rules began. And 

 already it has been found that his rules do apply pretty 

 accurately to the breeding of a very great number of different 

 kinds of animals and plants. But these animals and plants 

 are naturally those which breed rapidly and can be bred 

 on a large scale at small expense. So it comes about that 

 our knowledge of the application of Mendel's rules to the 

 breeding of horses, cattle, sheep, and pigs is still in its 

 infancy. The question whether Mendel's rules do or do 

 not apply to a particular case can only be decided after a 

 series of crosses and interbreedings have been carried out 

 in a particular way, and on a considerable scale : the prac- 

 tical breeder scarcely ever — in fact, never — carries out his 

 matings in this way, so that the applicability of Mendel's 

 rules to a particular case can never be decided by the ex- 

 amination of the results of matings not carried out with the 

 express object of answering this question ; though the 

 results of such matings sometimes give a rough — very rough 

 — indication of the answer. 



Now, Mendel's rules are so simple that if it could be 

 shown that those characters of live stock to which especial 

 attention is paid were inherited in accordance with these 

 rules, the breeder would be in a position to bring about 

 great improvements in these characters in a comparatively 

 short period of time. To bring about these improvements 



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