Foods / by Edward Smith.

  • Edward Smith
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Foods / by Edward Smith. Source: Wellcome Collection.

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    The importance of the latter is the more apparent, since wasting of the body is familiarly associated with decay of life ; but the former is so much the more urgent, that whereas the body may waste for a lengthened period, and yet live, it rapidly dies when the source of heat is removed or even greatly less- ened. The production of heat in the body, so wonderful in the process and amount, results only from the chemical combination of the elements of food, whether on the minute scale of the atoms of the several tissues, or on the larger one connected with respiration, and is thence called the combustion of food. As familiar illustra- tions of the production of heat from chemical change, we may mention that when cold sulphuric acid and cold water are added together the mixture becomes so hot that the hand cannot bear it, and the heating of hay- stacks, and also of barley in the process of malting, is well known. This action in the body is not restricted to changes in one element alone, but proceeds with all; yet it is chiefly due to a combination of three gases, viz. oxygen, hydrogen, and carbon, and requires for its support fat, starch, or sugar, or other digestible food composed of those substances precisely as coal and wood supply fuel for fire without the body. This effect is made extremely striking, by Professor Frankland, in the following table, which shows the amount of heat generated from so small a quantity as ten grains of certain foods during their complete combus- tion within the body, and the force which scientific calculations have shown to be equivalent to that amount of heat. The original quantity used by Prof. Frankland has been reduced by Dr. Letheby to ten grains, for the convenience of English readers. (Royal Inst. A-pril 1868.)
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