36 



dren shall live from day by day ; so she lays by a reserve from 

 which they can draw in time of need. This reserve is the fat 

 which she wraps around the tissues and with which she en 

 cases some of the organs. 



There is one very curious thing that is true of the different 

 food elements they can take the place of each other, to some 

 extent. This is not true of the proteids. Nothing can take 

 their place. But it is true of the carbohydrates and the fats. 

 At the New York State Experiment Station a cow was fed for 

 95 days upon food from which the fat had been extracted as 

 thoroughly as possible. In spite of this absence of food fat the 

 cow continued to secrete milk similar to that produced on a 

 normal ration. Nearly sixty-three pounds of fat was yielded 

 in the milk during the ninety-five da^s, and the cow gained 

 forty-seven pounds during that time, being judged a much fat- 

 ter cow at the end than at the beginning. This experiment 

 would seem to be conclusive that the milk fat was produced 

 quite largely, if not entirely, from the carbohydrates of the 

 food. On the other hand, so well is it settled that fat may be 

 converted into carbohydrates, that it is the common practice 

 to multiply the fat by 2.25 to get its equivalent in carbohy- 

 drates in making up an equation. 



Besides these three principle food elements which I have 

 enumerated there are subordinate food elements as follows: 

 Ash, representing the mineral ingredients after a food is 

 burned. These ashes consist of lime, potash, soda, magnesia, 

 iron, phosphoric acid and sulphuric acid. Water, present in 

 all foods to some extent. Fibre or cellulose, the coarse or 

 woody part of a plant (already mentioned under the head of 

 carbohydrates, but more appropriately coming here). 



A BALANCED RATION, WIDE AND NARROW RA- 

 TIONS. 



We are now in a position to frame our definitions. A bal- 

 anced ration is a ration in which all the elements required to 

 meet the needs of the animal for the time being are present in 

 right proportion. It will be seen by this definition that a bal- 

 anced ration is not a fixed and variable thing. A ration that is 

 correctly balanced for chicks is not balanced for laying stock, 

 and a ration that is balanced for laying stock is not balanced 

 for birds that are being fattened for market. It has been found 

 by experience that the ration of 1.2 (one part protein to two 

 parts carbohydrates) is about right for chicks; the ration 1.4 



