Royal Army Medical Corps training pamphlet no. 3 / War Office.

Date:
1944
Catalogue details

Licence: Public Domain Mark

Credit: Royal Army Medical Corps training pamphlet no. 3 / War Office. Source: Wellcome Collection.

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    Muscles can be made to contract by an electric current, and in cases of paralysis this is sometimes used to keep up their activity. 38. Expenditure of energy.—Energy is expended by the body in two ways :— (a) Internal work.—By this is meant the work always going on in the body, even during sleep, which is necessary to maintain life. It includes the beating of the heart, breathing, and the movements of the alimentary canal whereby the food is continually kept in motion. In-these activities the body uses on the average in 24 hours the amount of energy that would be required to raise 240 tons to a height of one foot. Asa by-product, the body tissues, particularly the muscles, also produce in 24 hours enough heat to raise the temperature of 40 pints of water from freezing to boiling point. This heat prevents the body from cooling down. If it is insufficient for this purpose, messages are sent to the muscles to make them contract frequently (shivering) and so produce more heat. The chemical processes of the body cannot continue normally unless a fairly constant internal temperature is maintained. (b) External work.—By this is meant the expenditure of energy which takes place when a person engages in any muscular exertion, such as manual labour, walking or playing games. The amount of energy expended in this way depends on the amount of work performed. The total daily loss of energy by the body is made good by the energy derived from burning up, or oxidation, of the food. A man doing heavy muscular work will require a more generous diet than a man leading a sedentary life. If this is not supplied, ' food stored in the body is broken down to prove the extra energy, with the result that weight is lost. 39. Supply of blood to muscies.—To maintain its life every muscle fibre, like every other cell, requires liquid food (fuel) and oxygen; and when called upon to perform hard work—+1.e. to contract strongly or frequently—muscles need especially large additional quantities of these chemical materials. Oxygen and fuel reach them in the blood, freely supplied to all muscles through arteries and capillaries ; and as it travels through the capillaries in the muscles this blood picks up the waste-products (chiefly carbon dioxide) formed by chemical action. | \