CHAPTER XXI 



DIGESTION, ASSIMILATION, AND NUTRITION 



BIRDS, like all other animals, in order to grow and produce 

 must eat. The bird in its ability to produce is somewhat 

 like a machine. The feed it consumes is the raw material, 

 and the raw material is first digested, then assimilated, and 

 produces the finished or manufactured product. That prod- 

 uct is the egg. Birds differ from ordinary machines, in that 

 they use some of the raw material to repair the body. There 

 are three processes in this nourishing and building up of the 

 body; namely, digestion, assimilation, and nutrition. 



Digestion. Digestion may be defined as a process in 

 which raw material is so changed that it can be assimilated 

 by the blood, and may furnish nutriment to the body. 

 Digestion is largely a process of chemical changes. The 

 digestive organs of the bird are the parts used to perform 

 this operation; and these organs, taken as a whole, are called 

 the alimentary tract, or the digestive system. 



Assimilation. Assimilation may be defined as a process 

 whereby material already digested is taken up by the 

 blood vessels and arteries. This assimilation takes place 

 in the lower part of the alimentary tract, or the intestines, 

 and is largely brought about by diffusion. 



Nutrition. Nutrition may be defined as the process of 

 transporting and distributing assimilated material to all 

 parts of the body. It is the ultimate process in the promo- 

 tion of growth, the repair of waste, and the yielding of a 

 product outside of the body. Blood is one of the leading 

 carriers of nutriment. 



Nutrients. Nutrients is a term used to designate certain 

 groups of feed materials which are eaten by animals. These 

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