Physical education / by Archibald Maclaren.

  • Maclaren, Archibald, 1819-1884.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Physical education / by Archibald Maclaren. Source: Wellcome Collection.

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    the body is given up by the blood in the form of carbonic acid, &c., and its place supplied by life-giving oxygen from the surrounding atmosphere. To make this all-important process plainer, let us glance at the mechanical action of breathing. On the requirement for air, the besoin de respirer, being experienced, the inspiratory muscles contract and lift the osseous framework of the chest, thus increasing its diameter from side to side and from back to front; while at the same time the large arched muscle (the diaphragm), forming the convex floor of the cavity, also contracts, and in doing so its fibres are straightened, and its elevated surface is consequently depressed, in- creasing the diameter of the chest from above down- wards. As this takes place the air rushes down the trachea, or windpipe, and passes at once into the lungs, which it fills out in every direction. But all muscular action is intermittent; the contractile effort accom- plished, the reaction begins ; the inspiratory muscles relax and a second set of muscles, the expiratory, antagonizing those which lifted the walls of the cavity, now contract, and the muscles of the abdomen, antagonizing the diaphragm, also contract, and the air is expelled by the aperture through which it entered. This is, in outline, the process of ordinary effortless breathing; but in the forced respiration of energetic exercise, and especially of exercise calling into action the muscles of the upper limbs and the upper region of the trunk, many of the voluntary muscles may also be employed in the process of respiration. I have stated that the involuntary muscles are prompted to action each by its proper stimulus; and the heart is stimulated by the presence and augmen- tation of blood within its cavities. Thus, the instant