CHAPTER XI
APPLICATION OF HEAT, COLD, AND COUNTER-IRRITANTS
Inflammation.
—A process called inflammation sometimes occurs in tissues that have been injured or invaded by bacteria. Although painful, it is nevertheless one of the reparative processes of the body, and therefore beneficial. Common examples of inflammation are boils, sore throat, and the swollen, painful condition resulting from sprains and fractures. Characteristic symptoms of inflammation are heat, redness, swelling, and pain.
When a tissue has been invaded by bacteria, nearby blood vessels dilate, thus bringing an increased supply of blood to the affected part. This extra supply serves to wash away the offending substance, and at the same time it brings more white blood corpuscles, one function of which is to destroy bacteria. From the increased supply of blood the affected part becomes red and hot, and so much blood may come that the vessels further on are unable to carry it away fast enough. Some of the fluid part of the blood is then forced out into the tissues, and the part
becomes swollen. Distension of the tissues and pressure on the nerve endings cause pain, and the injured part now exhibits the characteristic symptoms of inflammation.
Fig. 21.—"The History of a Boil." This figure represents a cross-section of normal skin. Note the surface layer, or cuticle, and the "true skin," or cutis. In the cutis one sees that the blood capillaries are just wide enough for the blood-cells to pass through "in single file." The skin has just been pricked by a dirty pin. On the point of this pin were several poisonous germs which were deposited at a. (From Emerson's "Essentials of Medicine.")
Fig. 22.—"The History of a Boil" (continued). The poison from these germs diffuses through the cutis. The capillaries dilate. The leucocytes force their way through the walls of the capillaries and travel towards these germs. Note the dumb-bell shape of the leucocytes as they pass through the minute holes in the capillary walls, and their pseudopods as they travel towards their common destination, attracted by the poison from the germs. The skin in this region is now swollen, red, hot, and painful. (From Emerson's "Essentials of Medicine.")