Today, medicine leads us to modern chemistry. The
University of Houston's College of Engineering presents
this series about the machines that make our civilization
run, and the people whose ingenuity created them.
Change was afoot in the 16th
century -- what we call the Renaissance. It was a new age
of art and music but, even more, a new way of learning.
Medieval scholars had tried to deduce the truth through
logic. Now we began, systematically, to observe the
material world around us. Science, as we understand the
word today, was just coming into being. And our modern
concepts of chemistry were forming within the field of
Medieval alchemists believed that matter was made of
subtle essences: earth, air, fire, and water. They tried
to deduce, logically, how imbalances of the essences
caused illness. They expected body fluids, especially
urine and blood, to reflect those essences.
Medical historian Stanley Reiser tells how a physician
would fill a special flask with a patient's urine and
hold it up to the light. He'd associate its gradations in
color with areas of the patient's body. A certain
coloration near the top meant that the illness was
affecting the patient's head, and so forth.
One alchemist knew that was a shell game. The Swiss
doctor Paracelsus spoke like an
alchemist. But he used the means of modern science. He
said, if you want to know how urine relates to illness,
distill the fluid and study its solid residue.
So Paracelsus steered us into methods of analytical
chemistry. The examination of body fluids was giving
alchemy a new purpose and new means. Today, our own
doctors use centrifuges instead of distillation. But
their purpose is the same as Paracelsus's.
The other obvious fluid, blood, is harder to read than
urine. Most of its story must be told on the cellular
level. It was more than a century after Paracelsus that
science was ready to deal with blood. In 1684, two
English scientists published papers that practically
demanded that medicine begin serious chemical analysis.
Thomas Willis renewed Paracelsus's call for the analysis
of urine by distillation. That, he argued, was how we
could learn its salt content. At the same time the great
scientist Robert Boyle wrote an extended treatise on
But Boyle didn't deal with the sick. The blood he studied
came from healthy people. Boyle grumbled that he, at
least, had shown what the composition of healthy blood
ought to be. And so the line between chemists and
physicians remained blurred until only 150 years or so
None of these analyses could bear full fruit until we had
microscopes that could descend to the cellular level,
until we had a molecular theory of matter, and until we
But the need to understand how our bodies work is primal.
That need finally drove us to invent a new chemistry of
analytical observation -- and to finally replace the old
alchemy of pure mind.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Reiser, S.J., Medicine and the Reign of
Technology. Cambridge: Cambridge University Press,
1978. (See especially Chapter 6.)
The Engines of Our Ingenuity is
Copyright © 1988-2004 by John H.