CHAPTER XIV 

 INCUBATION 



Incubation the beginning and the end of the common cycle of 

 operations in poultry culture. By incubation the bird is produced 

 from the egg. For incubation and the perpetuation of its kind the 

 bird, according to its sex, produces eggs or contributes to their fer- 

 tilization ; and then, in birds of the air, both male and female take 

 part in the incubating of the eggs, the substance of which has been 

 furnished almost wholly by the female. With poultry in domesti- 

 cation, as shown in Chapter 1, the male has no part in incubation, 

 and the female may often be relieved of it to the very great 

 economic advantage of man ; but, whatever the attitude of the 

 poultryman toward the process, incubation is one of his most per- 

 plexing problems, affecting and affected by many other important 

 problems, and seldom presenting itself in the same form twice in 

 succession. From the nature of the subject its proper place in a sys- 

 tematic study of poultry culture is doubtful. Equally good reasons 

 may be given for beginning and for concluding a detailed descrip- 

 tion of a generation of birds with the subject of incubation. But, 

 considering the close analogy between the egg of an oviparous 

 creature and the seed of a plant, it seems most natural and appro- 

 priate to begin a practical study of those details with the egg con- 

 sidered simply as material for the purpose, and without regard to 

 either its antecedents or its possibilities beyond the mere produc- 

 tion of an organism of the kind which produced it. 



The egg. Considered from the point of view just indicated, an 

 egg consists of four parts : 



1 . A germ, which is the true egg. 



2. A mass of albumin (the white of the egg), nitrogenous 

 matter which the germ, quickened into life, will, as it grows, appro- 

 priate to form the substance of the embryonic being. 



3. A supply of food (the yolk of the egg) for the first nourish- 

 ment of the young bird after exclusion. 



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