DIRECTORY 331
BRAHMAGUPTA
598–670
The Indian mathematician
and astronomer Brahmagupta
introduced the concept of zero into
the number system, defining it
as the result of subtracting a
number from itself. He also detailed
the arithmetic rules for dealing
with negative numbers. He wrote
his major work in 628, while living
and working in Bhillamala, the
capital city of the Gurjara-Pratihara
dynasty. Called Brahma-sphuta-
siddhanta (The Correct Treatise of
the Brahma), the work contained no
mathematical symbols but included
a full description of the quadratic
formula, a means of solving
quadratic equations. The work
was translated into Arabic in
Baghdad the following century
and was a major influence on
later Arab scientists.
See also: Alhazen 28–29
JABIR IBN-HAYYAN
c.722–c.815
The Persian alchemist Jabir
Ibn-Hayan, also known by
the latinized name Geber, was a
practical, experimental scientist,
who outlined detailed methods
for, among other things, making
alloys, testing metals, and
fractional distillation. Almost
3,000 different books have been
attributed to Jabir, but many were
probably written in the century
after his death. Few of Jabir’s
works were known to medieval
Europe, but a work attributed to
him, called Summa Perfectionis
Magisterii (The Sum of Perfection),
appeared in the 13th century. It
became the best-known book on
alchemy in Europe, but was
probably written by the Franciscan
monk Paul of Taranto. At the time,
it was common practice for an
author to adopt the name of
an illustrious predecessor.
See also: John Dalton 112–13IBN-SINA
980–1037Also known as Avicenna, the
Persian physician Abu ‘Ali
al-Husayn Ibn-Sina was a child
prodigy who had memorized
the entire Koran by the age
of 10. He wrote widely on topics
including mathematics, logic,
astronomy, physics, alchemy, and
music, producing two major works:
the Kitab al-shifa (The Book of
Healing), a huge encyclopedia of
science; and Al-Qanun fi al-Tibb
(The Canon of Medicine), which
was to remain in use as a
university textbook into the 17th
century. Ibn-Sina outlined not only
medical cures but also ways to stay
healthy, stressing the importance
of exercise, massage, diet, and
sleep. He lived through a period
of political upheaval and often
found his studies interrupted by
the need to stay on the move.
See also: Louis Pasteur 156–59AMBROISE PARÉ
c1510–1590Ambroise Paré spent 30 years
working as a military surgeon in
the French army, during which
time he developed many new
techniques, including the use
of ligatures to tie arteries after
amputation of a limb. He studied
anatomy, developed artificial limbs,
and produced one of the firstmedical descriptions of the
condition known as “phantom
limb,” in which the patient feels
sensation in a limb after it has
been amputated. He also made
artificial eyes from gold, silver,
porcelain, and glass. Paré
examined the internal organs of
people who had died violent deaths
and wrote the first legal medical
reports, marking the beginning of
modern forensic pathology. Paré’s
work raised the previously low
social status of surgeons, and he
acted as personal surgeon to four
French kings. Les Oeuvres (The
Works), a book detailing his
techniques, was published in 1575.
See also: Robert Hooke 54WILLIAM HARVEY
1578–1657English physician William Harvey
produced the first accurate
description of the circulation of
blood, showing that it flows rapidly
through the body in one system
pumped by the heart. Previously,
there were thought to be two blood
systems: the veins carried purple
blood full of nutrients from the liver,
while the arteries carried scarlet
“life-giving” blood from the lungs.
Harvey demonstrated blood flow
in numerous experiments, and
studied the heartbeats of various
animals. However, he was opposed
to the mechanical philosophy of
Descartes, and believed that blood
had its own life force. Initially
resisted, by the time of his death,
Harvey’s theory of circulation was
widely accepted. Smaller capillaries
linking the arteries and veins were
discovered under new microscopes
in the late 17th century.
See also: Robert Hooke 54 ■
Antonie van Leeuwenhoek 56–57