The other drainage arteries are all small, but many in number; while lakes and marshes aggregate fully 222% of the total surface.
Nitrite of amyl has the power of dilating the arteries; it has consequently been employed with much success in lowering the blood pressure and removing the pain in angina pectoris.
By raising the hand nearly to a level with the head both the constant pain and the severity of the throbs may be relieved, as the blood is not sent with such great force into the arteries and returns more readily through the veins.
The reason probably is that the application of cold causes contraction of the arteries leading to the inflamed part, while heat by dilating the vessels around forms a side channel through which the blood passes, the tension in the seat of inflammation being thus lessened in both cases.
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.