IS about three inches in length, and in its exterior form somewhat resembles the worm; it has a small head, a black skin edged with a yellow line on each side. The back is spotted with yellow, and the belly is of a reddish cast, with some faint yellow spots. The mouth of the Leech is of a most curious construction; there is there no jaws, tongue, or teeth, it is a kind of soft snout, applying close to the place it sets itself to, drawing up as through a syphon, the blood which this small animal feeds upon. The progressive movement of the Leech is effected by sticking, through suction, its mouth to a certain spot, then bringing its tail, which has the property of sticking also, to any place, ever so smooth, and then advancing its head farther on, quick followed by the tail, and so on. The common Leech is very frequent in brooks and rivulets; and often sting the legs of boys and men when bathing.
The blood which the Leech sucks out of the wound it makes, remains long in the body, congealed and blackened, and at last evaporates by the pores of the skin. When they are kept in a bottle full of water it is easily perceived that their ejections are performed by perspiration, and leave the skin as a kind of film bearing in some sort the shape of the body. They are also, when kept in a glass bottle with water, a good barometer, as they always come up to the neck of the bottle when rainy weather is approaching, remain in the bottom in dry weather, and move themselves anxiously up and down when the weather is stormy. Horse Leeches are larger than the common ones, more voracious, and narrower at each extremity. The use of the Leech is well known in medicine, as by its means the blood is extracted from the sickly parts with more ease, safety, and success than by the lancet.