class="x-ebookmaker-pageno" title="[Pg 30]"/> This retarded circulation is followed by the phenomena of emigration.

Emigration. Emigration of the white blood corpuscles consists in the passage of the cells directly through the vessel walls. It is most frequently seen in the capillaries, although it also takes place in the small veins. The white corpuscles, or leucocytes, have the property of ameboid movement, stretching out at will in any direction, long, narrow processes of their protoplasm, called pseudopodia, which may be attached to any object, and having secured such an anchorage, the rest of the protoplasmic body is drawn towards it.

In this way, the leucocytes are able to pass through the interstices between cells, or along narrow channels in the tissues. When the blood current becomes sufficiently slow to enable them to cling to the walls of the vessels, it is then that ameboid movement begins. Sometimes the cells loose their hold and are swept on again, but in other cases a minute bud of protoplasm will appear on the other side of the wall of the vessel, opposite to the spot where the leucocyte is clinging, and as this grows larger, a narrow neck of protoplasm can be traced through the wall directly to the leucocyte, and presently the mass of the leucocyte becomes proportionately smaller as the external bud of protoplasm grows larger. The conditions are gradually reversed, the nuclei of the cells appear outside and only a small mass of protoplasm remains within the vessel until finally the entire leucocyte is in the tissue outside of the vessel and is free to wander in any direction.

The mechanical part of this process is not yet understood. It is claimed by some that small openings exist in the walls of the vessels, between the endothelial cells which line them, to which is given the name of stomata. These openings ordinarily are invisible, but they are said to enlarge under the effect of the dilation of the vessels, and of the alterations in their walls, produced by the inflammatory reaction, and that the leucocytes escape through those openings.

There can be no doubt that the emigration is due to the ameboid motion of the cell, and the discovery of the phenomenon, to which is given the name chemotaxis, affords a sufficient explanation.

This is the influence possessed by certain substances to attract or repulse ameboid cells. In some cases this attraction appears purely to be mechanical, but it is probably a chemical effect of some kind in most, if not in all, instances.

The process of inflammation produces some chemical compound which similarly causes the cells to leave the vessels, and when there is any inflammatory action in their neighborhood, to find their way by the shortest route to the seat of the inflammation.

The leucocytes direct their course through the tissues to the chief points of inflammation by reason of chemotaxis, and surround the dead tissues, or any point of bacterial growth, or any foreign body which may be the cause.

The wandering leucocytes form the pus cells, and if they are very numerous, they constitute a purulent or suppurative inflammation. The wandering cells, however, are almost entirely made up of leucocytes, of which three forms are known, varying in size and in the size and number of their nuclei. The leucocytes surround any foreign body, and if the particles are small enough, they incorporate them within themselves, in fact, they may be said to swallow them. This taking up of particles by the wandering cells is called phagocytosis.

Diapedesis. When the circulation becomes very low and the pressure very high, there is a tendency of the red corpuscles to leave the vessel.

This is a purely passive process, and is observed only when the changes in the vessel wall are extreme. Both varieties of these cells die and are destroyed in the exudate, the former furnishing the fibrin which is so abundant in some forms of inflammation. This escape of red corpuscles is known as diapedesis, and is sometimes so extensive as to amount to capillary hemorrhage.

Symptoms. From antiquity the local symptoms of inflammations have been enumerated, as heat, redness, pain and swelling and to these has been added, impaired function.

The redness is due to congestion. The pain is due to the pressure exerted on the sensory nerves by the surrounding swelling, as is well shown by the intensification of the distress, as every beat of the heart forces more blood into the space already filled. In some cases, however, it may be caused by the direct action of the inflammatory agent upon the nerves. The heat is caused by the increased supply of warm arterial blood, for it has been abundantly proven that the temperature never rises above the heat of the blood, although naturally in a patient with fever, it will be above the normal temperature of that fluid. The swelling is due to the dilated vessels, and to the escape of serum and blood cells from the vessels into the tissues. The impaired function is chiefly caused by the pain which is often increased by any attempt to use the part, and by the swelling which prevents free movement, though the loss of function may also be dependent upon the direct action of inflammation upon the nerves.

The constitutional symptoms of inflammation are an elevation of temperature with or without a chill. There are also other disturbances, such as nausea, vomiting, diarrhea, sweating and polyuria. These are due to efforts on the part of the general economy to eliminate toxic substances.

The inflammatory products may poison the system in two ways: (1) by the diffusion of their chemical substances, (toxins and ptomains), or (2) by the passage of bacteria themselves into the blood.

Termination. Inflammation may result in resolution, suppuration, necrosis or sloughing, or in the establishment of a chronic state.

Resolution. Resolution is the termination of an inflammation by the gradual cessation of all the changes which have occurred. The pain subsides, the circulation becomes more normal, and the exudate is absorbed, or makes its way to the free surface of the body, where drainage occurs either spontaneously or by incision.