Hygiene and public health / by B. Arthur Whitelegge.

  • Arthur Whitelegge
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene and public health / by B. Arthur Whitelegge. Source: Wellcome Collection.

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    90ic + 300?/ = 300 2000a; + 3300^/ = 5000 giving as approximate values a? = 1*7 lb., and 2/ = i lb. It has been found experimentally that the energy which is developed by oxidation is for one ounce of lean meat about 50 foot-tons,^ carbohydrates 150 fobt- tC^ns, and fats 300 foot-tons. These determinations of potential energy have, of course, no close relation to nutritive values. The oxidation of food in the system is by no means complete, even as regards that portion whicli is assimilated. In calculating the mechanical work done, that of respiration, circulation, and locomotion must be taken into account, as well as the load carried or lifted. According to Haughton and Parkes the force exerted daily in respiration, circulation, and other internal work is about 260 foot-tons ; and in addition to this a strong man can do external work equivalent to 300 to 500 foot-tons more per day. Walking along a level road at three miles per. hour is equivalent to climbing vertically ^V*^^ distance traversed; at 4 miles ^th. Hence, if a man weighing W lbs. carries a load of X lbs. on a horizontal track for D feet, at 3 miles per hour, he exerts energy equivalent to foot-tons in so doino;. A march of 20 20 X 2240 * miles along the level involves work equivalent to 350 foot-tons, taking the weight of the body as 150 lbs. If a load of 60 lbs. is added, the work is 500 foot-tons., The whole work done, estimated in this way, represents only J-th of the force theoretically obtainable from the food'by coniT)uslTon' The^ energy expended in a fair day's work is about one-fifth meclianical labour to four-fifths heat {Martin). * Afoot-ton is the force required to raise 1 ton to a height of 1 foot.