128 POULTRY PRODUCTION 



be considered which is the better of the two reciprocal 

 crosses. 



Such a practice as this is sometimes erroneously referred 

 to as line breeding, because both lines of stock are bred pure 

 and only the first cross used. 



PURPOSE OF SELECTION. 



The purpose of selection is to prevent the birth of indi- 

 viduals not suited for production. In pursuance of this 

 purpose the points to be selected for in the order of their 

 importance are (1) constitutional vigor, (2) hatching power, 

 (3) fecundity, (4) longevity, (5) early maturity, and (6) 

 breed and varietal characteristics. 



With the producer, from the nature of the case, selection 

 is confined to the first and the last three points. In most 

 cases it will be confined to the first and the last. For the 

 second and third he must depend upon the breeder. If 

 grading is carried on, selection so far as the producer's own 

 flock is concerned is further limited to females. 



Constitutional Vigor. — The appearance and manifestation 

 of maximum vigor and vitality can only be present where 

 all organs of the body that have to do with digestion, circu- 

 lation, respiration, and the nervous system which controls 

 all, continuously perform their full work. This maximum 

 efficiency of all organs makes up constitution. 



That constitutional vigor is the foundation of good pro- 

 duction cannot be overemphasized. 



The best inheritance conceivable, with regard to all other 

 points of selection, is useless unless there is physical stamina 

 to back it up. Without it inheritance is as helpless as a 

 dynamo that has no "conducting cable to connect it with its 

 motors. It is the conductor that makes possible in produc- 

 tion the possibilities generated in breeding. 



There must be physical thrift to withstand the exhaustion 

 of an inherited heavy production. Reproduction in the hen 

 is normal only when there is an excess of vitality, as well as 

 of feed, beyond that needed for the hen herself. In the C9,5e 



