FOODS IN NUTRITION 177 



of a carbohydrate in the body is the same. Since this class 

 of food is easily handled by the alimentary canal, requires 

 little extra O for its destruction, and is very abundantly sup- 

 plied by the vegetable world, it is the most economical from 

 digestive, absorptive, respiratory and financial standpoints. 

 Carbohydrates may also be deposited as adipose tissue as 

 will be seen presently. 



3. The fats have the same general office in nutrition as the 

 carbohydrates, viz., the furnishing of energy by oxida- 

 tion. They leave the alimentary canal by way of the lacteals, 

 are conveyed by the blood to the tissues and there oxidized 

 with the formation of carbon dioxide and water and the lib- 

 eration of heat. Though more O is necessary to burn up the 

 fat than the carbohydrate molecule, oxidation of the fat is 

 attended with the liberation of the greater amount of heat 

 i. e., of energy. This would seem to indicate that it would 

 be more economical to eat fats to the exclusion of carbo- 

 hydrates, since a smaller quantity of the former will supply 

 the requisite amount of energy. This is theoretically true, 

 but considerations of digestion render it not practically 

 so, since fats tax the digestive apparatus much more than 

 carbohydrates. 



The fat deposited in the body the adipose tissue what- 

 ever may be its source, it is to be looked upon as so much 

 stored-up energy. When the supply of blood is cut off it is 

 the first part of the organism to be consumed. Hence, a fat 

 animal will survive starvation longer than a lean one. 



The individuality, the functional activity, and the proper- 

 ties involved in regeneration of protoplasm are ultimately 

 dependent upon its nitrogenous characters. The other con- 

 stituents are more or less passive. The oxidation of fats and 

 carbohydrates, however, takes place under the influence and 

 through the agency of the cells. It is scarcely necessary to 

 add that neither fats nor carbohydrates, nor both together, 

 are sufficient to sustain life; for life is embodied in proto- 

 plasm and protoplasm must have nitrogen, which element 

 these foods cannot furnish. 

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