Page:Food and cookery for the sick and convalescent.djvu/29

Rh HE familiar comparison between the body and the locomotive engine serves as a most forcible illustration for studying the fuel value of foods.

Food furnishes fuel to supply heat and energy for the body as wood and coal do for the locomotive. The food not only does this work, but it must also build and repair the human structure, while the locomotive is not capable of making its own repairs.

Latent heat is just as surely found in meat or bread as in wood or coal. They are both waiting to be oxidized, that they may be converted into heat and energy. As different kinds of wood and coal are capable of giving off different degrees of heat, and also giving off that heat in longer or shorter periods of time, so different food stuffs work in comparatively the same way.

The subject of the fuel value of food is of such great importance that within the last few years much time has been devoted to experiments along this line, and the results have furnished much valuable knowledge to aid us in correct feeding.

The latent energy in different foods has been determined by their oxidation, outside the body, in the apparatus known as the bomb calorimeter. Still further experiments have been made with the respiration calorimeter. By this apparatus not only is the fuel value of all the food taken into the body determined, but the excreta, products of respiration, and heat given off by the body are measured. From this statement it can be seen that man himself is used in making the experiments.