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Homework Help: Science: Biology: Leeches
by Emily McPherson
The History of Medical Leeches
During the 1800's many doctors made their living be applying leeches to
the bodies of sick people. Though it doesn't sound like a healthy thing to
do, our ancestors thought to cure anything from headaches to obesity, a
leech would do the trick.
Leeches were used on the general belief that illness was caused by an
imbalance of the body's essential fluids, known then as the four humors.
The four humors were blood, phlegm, and yellow and black bile. The
Medieval people believed leeches could suck out the black bile, leaving only
the good, healthy stuff behind. Using leeches in this way was called
leech craft and it has been performed since Ancient Greeks times.
Bloodletting reached its peak in about 1830 when all chemists kept a supply
of squirming, writhing, blood-sucking leeches in a porcelain jar on the
counter. London hospitals alone were using seven million leeches a year.
Leech Application
Leeches have a suction on each end of their bodies which they use to move
around. The mouth of a leech is centered in the front suction and has three
jaws which contain over 300 teeth.
A leech may feed for between 10 minutes and two hours before it's full.
It then falls off, too fat with blood to move. The wound it leaves is star
shaped and does not heal easily. Usually during medical operations, leeches
are only left on for less than an hour.
Scores of leeches can be applied to a person at the one time. Sometimes,
during the early leech practice, they were left on for so long that patients
lost 80% of their blood!
Bloody Treatment
In modern medicine, blood letting is no longer practiced, but leeches
continue to be used. Their main use is relieving blood congestion in
delicate operations where such use is less likely to cause infection than
many other techniques. The healing qualities of leeches are better understood now than ever before.
By draining the blood from bruised areas, they reduce tenderness and
swelling. Leeches also help to restore blood flow to injured body tissues,
or severed fingers and toes which have been reattached through
microsurgery.
In cases of severed body ligaments, some veins and blood vessels are too
small to be sewn back together by a doctor. This means that that the
injured tissue isn't getting a proper supply of blood, without this, it will
die and become gangrenous. Hungry leeches, however, are able to draw blood
to the area and start the circulation going until the body's own system kick
in once again.
Leeches are also found helpful in reducing the blood accumulation in body
tissues after plastic surgery.
Leech Disposals
Leeches involved in surgical operations are not reapplicable. After
being used, most leeches are disposed of like hypodermic syringes. This is
to stop the spreading of other diseases such as hepatitis A and AIDS. Both
diseases are carried in the blood stream.
They're After You!
Leeches are used to a blood thirsty lifestyle and they have a saliva that
is filled with chemicals to help them on their 'mission'. Their saliva,
hirudin, contains a painkiller which stops their victim from feeling the
bite; a chemical which reverses blood clotting; and, an antibiotic. This
stops the blood from 'going off' for up to six months whilst inside the
leech's belly.
Researchers are currently working on the idea that some of these chemicals
contained in the saliva can be used to make life saving drugs. One
chemical, bio-germ for example, could help heart patients by dissolving
blood clots. But, to carry out proper testing and experiments so that these
drugs may one day become reality, a huge amount of leech saliva is needed.
This means finding an immense quantity of leeches.
There is only one place where leeches are known to be found in large
numbers- a leech farm. In the UK, there is the one and only official leech
farm in the world. The 'Wales Leeching Foundation' breeds about 80
thousand leeches a year and about 20,000 of these are used for research,
while another 30,000 are used in surgery.
Bloodsuckers!
While most leeches are blood-sucking parasites, not all are good for
medicinal purposes- the giant Amazon leech is one of these. This leech
feeds on decaying animals and plant material, instead of blood.
Homework Help: Science: Biology
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