DAIRY MEETING. 121 



is the carbohydrates which are found as sugar or starch in the 

 cells or crude fiber in the cell walls. A few plants like cotton 

 and flax store up fat or oil in their seeds instead of starch, 

 also large amounts of protein. We, therefore, see that the com- 

 ponent parts of plants are the same as those of the animal body 

 and furnish the material necessary to sustain it. 



The animal body is often spoken of as a machine and the 

 plant the natural fuel to run it. The body is certainly a most 

 wonderful machine. It might be likened "to a gas engine which 

 supplies power to move itself and other bodies from power 

 developed by burning the fuel within its cylinders or body walls. 

 The animal body is more wonderful than the engine inasmuch 

 as when furnished with material it does its own repairing. In 

 one respect it differs from the artificial machine in that it 

 cannot be stopped and started again at will. 



NUTRIENTS. 



The component parts of plants of which we have been 

 speaking, viz. : water, protein, ash, carbohydrates and fat, are 

 called nutrients, a term with which you are probably all familiar. 

 Now what is the special office of these different substances? 

 Water is essential as a food but may be disregarded in this 

 discussion. The ash supplies the mineral portion of the bone 

 and serves to refplace the constant waste of mineral matter in 

 the system. The protein differs from the other nutrients, as 

 has already been pointed out, in that it contains nitrogen and 

 sulphur. Its primary office is that of building tissue. It is the 

 sole source whence may be made good the loss of proteids from 

 the body. The protein of the body or other nitrogenous mate- 

 rial like wool, hair or flesh, cannot be made in the animal except 

 from protein of the food. We, therefore, see that a sufficient 

 oupply of protein is absolutely necessary in the food. Protein 

 also if fed in excess of the needs for repair or growth can ba 

 and IS used as a fat former or heat producer, or, in other words, 

 as fuel to run the engine, but this is not an economical use to 

 make of it as it is the most costly nutrient in foods. 



The carbohydrates and fat are so similar in their offices in 

 feeding that they may be considered in this connection as one. 



