36 



This reserve is the fat which she wraps around the tissues and 

 with which she encases 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 contin- 

 ued 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 days, and the cow gained forty-seven pounds dur- 

 ing that time, being judged a much fatter 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 carbohydrates in making up an equation. 



Besides these three principal food elements which I have enu- 

 merated there are subordinate food elements as follows : Ash, rep- 

 resenting 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 



RATIONS. 



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 balanced 

 ration is not a fixed and invariable thing. A ration that is cor- 

 rectly 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 experi- 

 ence that the ration 1.2 (one part protein to two parts carbohy- 

 drates) is about right for chicks; the ration 1.4 is about right for 

 laying stock ; and the ration i .6 is about right for fattening. In 



