ridiculously wrong. From Greek and Roman times all the way to the early
Renaissance, no researcher could reliably and precisely dissect any
mammal and ascertain what the purpose of the vessels and the heart was.
There was no way of properly sedating an animal while slicing open its
chest, so any animal experimentation gruesomely involved strapping down
the poor subject for a few seconds and hurriedly carving open the thoracic
cavity as it bled to death. This left fleetingly few seconds to ponder about
the flow of blood and dynamic function of the heart. It is little wonder that
no one understood how it all came together.
Galen and every anatomist after him were confronted with the labyrinth
of the large vessels, some as large in diameter as a garden hose, coursing
hither and yon about the oddly shaped muscular organ. Anatomy students
today are given textbooks with color-coded drawings delineating arteries
and veins and the circuitous route of the flow of blood, but in ancient
times an open chest with a pounding heart and indiscernible vessels
presented an enigma.
For 1,500 years, medical students were taught that there were two
distinct and parallel vascular systems based upon the thickness of the
vessel walls. Dear Reader, if you and I were in an anatomy lab today I
could show you the chief differentiating feature of blood vessels
everywhere in the body: on the one hand, a flimsy vessel with thin walls—
a vein—on the other, a blood vessel with thick, stout walls—an artery. No
matter the location of the vessels (whether they are in the abdomen or in a
limb), veins and arteries always fall into these two main categories.
Galen (incorrectly) concluded that arteries had the innate ability to
pulsate based upon the thickness of the vessels. Worse, classic Galenic
teaching held that the liver was the source of blood. While correct in
maintaining that blood was supplied with nutritive properties from the
digestion of food, Galen was wrong to teach that blood ebbed and flowed
in both directions in every vein in response to the attractive powers of
individual organs and muscles. To make it all work, Galen theorized that
all organs “attracted” blood to themselves, and “consumed” the blood and
its vital spirit.
Unable to understand the function of the lungs, Galen and his
apprentices established that the vital spirit, or “pneuma,” entered the lungs
with each breath; how else to explain the impulse to breathe? The divine
breath, they concluded, is what vivified the pulsating, arterial blood,
marcin
(Marcin)
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