ii5 2 Rural School Leaflet 



The plant may use any one or all three of the groups, protein, carbo- 

 hydrates, and fat, as a form in which to store reserve food. Mainly, 

 however, the common form in which reserve food is stored is in the form 

 of carbohydrates, of which starch is the most common example. 



The body of a cow is built up from the food that she eats. It is com- 

 posed of the elements that also make up the plant body. These elements 

 form numerous compounds, which may be grouped into the same five 

 groups into which we separated the plant body or the food of the cow: 

 water, ash, protein, carbohydrates, and fat. The chemical formula for 

 an animal fat may not be the same as for the particular vegetable fat that 

 was in her food ; and this will hold true also for proteins and carbohydrates. 

 In the animal body there are few compounds that are carbohydrate in 

 nature. The plant, as noted above, stores its surplus food mainly as 

 carbohydrate, with some protein and fat. The animal, on the other hand, 

 stores its excess food material as fat. The proportion of protein in the 

 animal body as a whole is large because the lean meat of the muscle tissue 

 is nearly pure protein. A good example of animal protein is the albumen 

 of an egg; another is the casein, or curd, of milk. We have no common 

 animal carbohydrate. Lard and tallow are common forms of animal fat. 



What data we have go to show that in order to form the protein of the 

 body the animal must have protein in the food. Any excess of protein 

 in the food that is not needed to form body protein will be broken up. A 

 part of the protein carrying the nitrogen will be excreted and the remainder 

 will be used as carbohydrate material. The protein of the body can have 

 no source except in the protein of the food. The carbohydrate material 

 in the body can have as its source, protein, carbohydrates, or fat in the 

 food. The fat in the body may be manufactured from the protein, 

 carbohydrates, or fat. Therefore, to summarize, there must be a sufficient 

 amount of protein in the food in order to keep up the necessary protein of 

 the body, but the fat or carbohydrates of the body may be derived from 

 any one of the groups — protein, carbohydrates, or fat — in the food. 



The animal uses the water that it drinks and that it derives from its 

 food to keep up the supply in the body, much in the same way that the 

 plant uses water to help support the body by keeping the cells distended, 

 and as a transportation agent. The ash (mineral matter) taken into 

 the body forms the bones and furnishes the mineral matter that is present 

 in all the tissues. The protein makes up the muscle tissues of the body 

 and any nitrogenous matter in the other tissues. The carbohydrates are 

 used to furnish the energy for the muscles. Any excess of carbohydrates 

 may be transformed into fat and stored as reserve material. Fats in the 

 body are used to give energy to the cells, or they may be stored as body fat. 



A cow or other animal has three uses for the food that it takes into its 

 body: (i) to furnish energy for the mechanical work of the body; (2) to 



