A gall mite (Phytoptus pyri) sometimes severely injures the leaves, on which it forms blisters - the best remedy is to cut off and burn the diseased leaves.
The manifold plate is then heavily punched from one side, so that the opposite face protrudes in broken blisters, which are then hammered down until each becomes a centre of wave propagation.
The numerous small blisters or vesicles thus derived coalesce, forming a large sac full of "blister-fluid."
Vesica, a bladder), which irritate sufficiently to cause the blood-serum to exude and form vesicles or blisters, e.g.
Frost blisters are pustular swellings due to the up-growth of callus-tissue into cavities caused by the uprising of the superficial cortex under the action of intense cold.
Blisters also cause local dilatation of vessels, but are usually applied to the skin for inflammation in deep-seated parts, such as the lungs, though they also relieve pain in the joints in acute rheumatism.
Pustula, a blister), still more powerful in their effects, causing the blisters to become filled with pus, e.g.
24) are of economic importance, as they contain a vesicant substance used for raising medicinal blisters on the human skin.
Blisters applied at some distance from inflamed parts are also sometimes useful; and probably they produce this good effect by causing a reflex contraction of the arteries in the inflamed part, and thus acting like a cold application.
In the Ebers papyrus, 1550 B.C., mention is made of blisters, ointments, clysters, mineral and vegetable drugs.