Chuck Underwood, age 15, of Jamestown, N.Y., for his question:
DID DOCTORS USE LEECHES TO DRAW BLOOD?
Leech, also called a bloodsucker, is a worm that has a disk like sucker at each end. At one time in the past leeches were widely used by doctors and barbers for bloodletting. They are still used for this purpose in some regions of the world.
Doctors once used what they called medicinal or health giving leeches to remove blood from patients. At one time, bloodletting was considered to be the best cure for almost ail diseases.
Early in the 19th century, leeches were so popular with doctors that some people made a business of raising them. The name "leech" was given to both the physician and the bloodsucking worm which was his favorite instrument.
At the present time, the worms are rarely used for bloodletting in America or Europe.
Leeches are closely related to earthworms. They are flattened ringed worms that measure from less than an inch in length to 18 inches long. They are equipped with sucking disk at both the anterior and posterior ends. The body is made up of 33 segments. The external segments vary in number among different species. Each ring contains about five or six warty prominences, or papillae, which serve as sense organs.
On the anterior end of the worm are several eyes. In some leeches, the anterior mouth contains three toothed plates with which the animal pierces the skin of its prey.
Blood ingested by leeches is mixed with salivary juices containing an anticoagulant substance known as hiruden. Hirudin can be extracted and has been used in some medicine to prevent blood clotting.
The blood passes into a dilated, branched stomach, or crop, where it is stored for several months before being completely digested by the leech. A leech consumes about three times its weight in one feeding and then subsists for months on the stored food.
Leeches are hermaphroditic, which means that each specimen contains both male and female reproductive organs. Typical species lay their eggs in mucous cases known as cocoons. Upon hatching, the young of some forms attach themselves to the underside of an adult and are carried about with it until they can live independently.
Aquatic leeches can swim. Both aquatic and terrestrial species move over solid surfaces by muscular expansion and contraction. Some leeches also move by attaching themselves with one sucker and then somersaulting onto the other sucker.
Some leeches live as parasites, sucking on the blood and tissue of other animals for nourishment. Others feed on decaying animal and plant material.
Parasitic leeches attack to their victim with their front sucker, make a wound and then suck out blood.
Leeches may be black, red or brown and may have stripes or spots. They are sensitive to touch, temperature and drying.