英语时差：机械水蛭

The problem is that sometimes the veins can’t remove the blood fast enough from the area and so the blood begins to clot. If additional surgery fails to correct the situation, they bring in the leeches. The leeches do three things. They attach to the wound and suck out blood, they provide their own anesthetic so that the bite doesn’t hurt, and they secrete an anticoagulant that keeps the blood flowing for hours. This gives the body time to form new veins that can handle the blood flow. Researchers in Madison, Wisconsin have come up with a machine that acts as a leech. But unlike leeches, their machine can be sterilized and doesn’t move from one body part to another, and doesn’t fall off when it’s gorged itself.