Leech, n.
1. A physician or surgeon; a professor of the art of healing. [Written also leach.] [Archaic]
Leech, heal thyself. --Wyclif (Luke iv. 23).
2. Zool. Any one of numerous genera and species of annulose worms, belonging to the order Hirudinea, or Bdelloidea, esp. those species used in medicine, as Hirudo medicinalis of Europe, and allied species.
Note: ☞ In the mouth of bloodsucking leeches are three convergent, serrated jaws, moved by strong muscles. By the motion of these jaws a stellate incision is made in the skin, through which the leech sucks blood till it is gorged, and then drops off. The stomach has large pouches on each side to hold the blood. The common large bloodsucking leech of America (Macrobdella decora) is dark olive above, and red below, with black spots. Many kinds of leeches are parasitic on fishes; others feed upon worms and mollusks, and have no jaws for drawing blood. See Bdelloidea. Hirudinea, and Clepsine.
3. Surg. A glass tube of peculiar construction, adapted for drawing blood from a scarified part by means of a vacuum.
Horse leech, a less powerful European leech (Hæmopis vorax), commonly attacking the membrane that lines the inside of the mouth and nostrils of animals that drink at pools where it lives.