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.

    9/374 (page 9)
    minutes ; and when the most important cells have died, the death of all must follow. Life therefore depends on maintaining the internal supply services. But there must also be external supply services : animals and men (unlike trees) have to find or catch their food before they can digest it, and for this purpose they have to be able to move about. . A human being is not a stationary mass ot cells, all more or less alike. He is rather a united army of cells equipped for complicated operations both of defence and offence. This army is organized into many different specialist units; and all cells, like all soldiers in a modern army, are specialists in their jobs. 7. Bones and muscles.—Some of the cells take in lime (calcium) salts and thereby grow hard and almost stony. These form the bones, without which the body would be flabby and ineffective. But a very rigid structure would be equally unsatisfactory. Hence the spine, which acts as the central support, consists of a large number of small bones (vertebrae) jointed together so as to bend forwards, backwards or sideways. The arms and legs are attached indirectly to the spine in such a way that they can move freely, and there are niany joints in _ each limb. Fic. 3.—IHE Biceps. MuscLE BENDS THE ELBow. All movements are made by contracting a muscle ; and most muscles run between two or more bones which are connected by a joint. The muscles consist of bundles of thread-like cells or fibres, arranged lengthways, which are able instantaneously to change their shape from long to broad. A person who demonstrates the size and hardness of his biceps has a feeling that the muscle swells because he is bending his elbow (Fig. 3) ; but actually the muscle as a whole-—have become short and thick instead of long and thin.