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The Cornell Reading-Courses 



animal as does the same weight of carbohydrates or of protein. 

 too well known to need illustration. 



Fat is 



DEMANDS OF THE ANIMAL FROM ITS FOOD 



Requirements for maintenance of tissues 

 Animals need food to maintain their existence, which is dependent on 

 matter and energy. As shown above, the dry matter of the body is made 

 up of ash, protein, carbohydrates, and fats. The part of the body that is 

 more or less permanent is that made up of ash and protein, while the 

 carbohydrates and fats are more changeable and have to do more with 



Fig. 2. — One use of the energy in food: the power to do work 



the energy of the body. However, the tissues are constantly being worn 

 out, and must be replaced, and this requires a new supply of ash and 

 protein from the food. 



Besides the ash and protein constantly being replaced in the mature 

 animal, the growing animal must have matter to form new tissue and 

 the productive animal must have matter for products such as milk, eggs, 

 wool, and the like, all of which contain ash, fat, protein, and carbohydrates. 

 Then, in the pregnant female, ash, fat, protein, and carbohydrates are 

 needed for the growth of the young. 



Requirements for energy 

 After this matter has been supplied from the food for the maintenance 

 of the dry matter of the body, there is a still further demand on the food 



