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The Causes and Results of Inflammation

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THE CAUSES AND RESULTS OF INFLAMMATION.

The Causes of Inflammation are numer ous, but they may be placed in several classes. }'or instance, we may speak of physical causes, including in this class injury done by an instru ment, which cuts or tears or bruises; or injury done, for instance, by a bullet, which enters the tissue and lies there; or injury done by electricity, by light or heat.

Then there are chemical causes. The in jury or irritation done by acids, or caustic sub stances, would be included in this class.

But by far the commonest causes of inflam mation are living organisms, microbes, organ isms of the type classed generally as bacterial, which, gaining entrance to the tissues in one way or another, set agoing the various processes of inflammation by acting as irritants to the tissues, either by their own activity or because of the poisonous substances they produce in the course of their multiplication.

A study of the inflammatory process set agoing in a tissue by this last kind of cause reveals occurrences of a most remarkable and highly interesting character. In the case of injury by the other kinds of causes, the cut, the tear, the bruise, the burn, &c., the damage to the tissue has been done, and is finished, provided the instrument of injury, the knife, &c., has been perfectly clean. But in the case of inflammation set up by the introduction of a microbic poison, the injury or irritation is going on, the living poison is multiplying in the tissue, extending its ravages farther and farther. In the case of injury done by physical or chemical agents, generally speaking the re action of the tissue would be confined to the breaking down and removal of the parts of the tissue destroyed by the injury, and the repair of the breach so made. But when the inflam mation is septic, where, that is, it is (Inc to the operation of microbic substances, the whole purpose, so to speak, of the inflammatory pro cess, to begin with, is to kill or neutralize and expel the invading organism, and not till this has been accomplished can the process of clear: ing away destroyed elements of tissue be gone on with, or repair begun.

This primary necessity, the destruction or expulsion of the invading organisms, is the reason for many of the changes that go on in inflammation. The main agents in defending the tissue are the white cells, which pass out of the blood-vessels of the inflamed region and flock in enormous numbers to the irritated portion of tissue. It has been shown that the

process by which they protect the tissue is two fold ; some of the white cells directly attack the organisms by incorporating them within their own substance. On p. 53 it has been de scribed how the amoeba surrounds by processes of its substance particles it comes into contact with, and thus incloses then) within it, digest ing them, or otherwise acting on them. So do the white cells swarm to the attack of the organisms of disease, eating them up, so to speak, and so depriving them of their power to injure the tissue.

Thus, within a short period of the introduc. tion into the tissue of some infective material, large numbers of white cells, which have emi grated from the nearest blood-vessels, will have appeared upon the scene, and will be found crowded with the minute organisms of the infective material, which they have ingested. Cells which play this active part are called phagocytes (Greek, pluzgein, to eat up, and katos, a cell).

But there is another method of defence against attack which the organism possesses. There are several varieties of white cells in the blood, as has been explained on p. 19, and illustrated on Plate III., p. 18. The cell 04 of that plate is specially the phagocytic cell, and the cell of the a group marked 3 has also phagocytic power. But other cells play other and not less heroic parts. The numbers of viru lent organisms that may be introduced into the body by the prick of a dirty needle, or by a poisoned wound of any kind, may be so great as to make it impossible for the phagocyte cells to get at them all. The evidence is complete that the body is yet not without defence. Other kinds of white cells help the defence by breaking down, and so liberating from their interior substances which are unfavourable to the life and growth of the invading organisms, and it may be that some cells, without breaking down, are able to deprive the invading organ isms of their power of mischief by discharging among them sonic of the granular material they manufacture. The cell numbered 5 of the a group in Plate III. seems to have this power.

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