BODY REQUIREMENTS FROM FOOD 21 



energy, and ordinary waste of tissue) which is available 

 for this purpose. 



The various constituents of the food which are 

 capable of supplying heat, energy, or body tissue to 

 an animal are called " nutrients," and all the processes 

 through which the nutrients go in the animal body in 

 order to fulfil their respective functions are called by 

 the word " metabolism," such processes would therefore 

 be called " metabolic processes." 



Before attempting to describe how to meet the 

 above body requirements, it will be necessary to give 

 the process of digestion and the various food-stuffs that 

 are available for feeding purposes. 



VII. THE PROCESS OP DIGESTION. 



Food material is taken in at the mouth of the animal 

 and gradually passes along the alimentary or food canal, 

 where it is attacked at different stages by various 

 digestive juices as well as bacteria. In this way part 

 of the food is dissolved or digested, and is therefore 

 capable of soaking through the thin cellular walls of 

 the intestines into the circulation, which carries this 

 digested food to various parts of the body where the 

 nutritive material is required. 



The part of the food which resists the digestive 

 juices travels along the alimentary track, and is finally 

 expelled as solid excrement. 



Digestion, therefore, refers to those processes 

 through which the food passes in the animal body, by 

 which it is dissolved and thus rendered capable of being 

 absorbed into the blood. This solvent action is brought 

 about by ferments or substances capable of producing 

 fermentation. 



