Читать книгу The Body at Work: A Treatise on the Principles of Physiology онлайн

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Lymphatic glands are barriers which stop the spread of infection. They are the stations to which our police carry captured germs. The skin of the heel is abraded. Germs from the soil, or elsewhere, which have accumulated in a dirty stocking—owing to the warm moisture enclosed by an impervious boot, the woollen covering of the foot is a peculiarly healthy place for germs—enter the opened lymph-spaces of the subcutaneous tissues. Leucocytes hasten to the spot. They seize the invaders with their pseudopodia, engulf them in their body-substance, enter lymphatic vessels, and are rolled away by the lymph-stream. The instinct which brings them in ever-increasing numbers to the breach in the protecting skin can be explained only in terms of force. From our own conscious action to the causes which determine the movements of a leucocyte, or of an amœba, is so deep a drop that we prefer to recognize in the latter a merely chemical attractive force. “Chemiotaxis” we term the influence which draws leucocytes to the place where food is abundant; although it is also the place, one must admit, where in the interests of the body as a whole they run great risk of asphyxiation. It is appetite which draws a schoolboy to a bun-shop; a sense of duty prompts a fireman to risk his life in a chamber filled with smoke. We have no desire to humanize a leucocyte; but it is difficult to emphasize too strongly its independence. It would be absurd to use terms which imply that a leucocyte has a self-directive power; yet it is equally misleading to describe its migration to the seat of injury, its retreat with ingested germs to a lymphatic gland, its wriggling from the lymph-ways of the gland into the shelter of its adenoid tissue, in terms which imply that the forces which direct it are known, and their mode of action understood. The success which attends the inroads of germs is due to their amazing capacity for multiplication when they reach lymph or blood. It is useless to attempt to form an idea of the rapidity with which they divide, since we have no data upon which to base calculations. If the leucocytes fail to deal with the first few that enter, germs soon swarm within the lymph-vessels. This leads to an inflammation of the walls of the vessels, which may then be seen as red lines beneath the skin. These red lines lead upwards towards the nearest lymphatic gland. The glands in the space behind the knee are not usually affected when the focus of infection is in the foot. The red lines can be traced up the inner side of the knee and the front and inner side of the thigh to the groin. The glands in this situation swell until they can be easily felt. If the mischief is in the hand, the gland at the elbow may be affected, but most of the lymphatics pass by it on their course to the glands in the armpit. If a sore throat is the source of infection, the glands beneath the angle of the jaw enlarge. Thus various glands block the further progress of infection. In doing this their resources may be strained to the uttermost; they may enlarge, become tender, grow soft, fill with pus, break down and discharge the pus without the aid of a surgeon’s knife, although as soon as pus is recognizable within them it is wise to let it out. If germs pass through these first stations into the lymph-vessels beyond them, abscesses are formed in other situations. A condition of “blood-poisoning,” so called, is set up.