Galen
& Circulation
by Matthew Megill, Dartmouth
College
Why did it take Western science
until the seventeenth century, to discover the process of blood
circulation? Why do we still think of the heart as an emotional
organ, both in our poetry, and in our Valentine's Day cards?
Many answers could be given to these two questions, but one partial
explanation can surely be traced to the research of Galen.
Galen was a second century A.D.
Greek physician, probably the most respected Greek doctor after
Hippocrates, and a man who knew a great deal about the heart,
as we may see in many preserved writings, such as his work On
the Doctrines of Hippocrates and Plato. Many have wondered
why Galen failed to recognize the heart's true role as a circulatory
pump. The question must be raised, because, from a strictly scientific
perspective, he could have, perhaps even should have, discovered
circulation. He had all the pieces that were needed, and which,
indeed, William Harvey used to perceive the true process in 1628.
Yet despite suggestive evidence, Galen failed to pursue the idea
of the blood's circulation, or to try the simple calculations
which lent Harvey such success 1400 years later. Galen was not
dumb, and we must ask if anything prevented him from making the
logical leap to an understanding of blood as a reusable transport
vehicle, from a traditional conception of blood as a consumable
fuel, much like the water that irrigated agricultural fields.
My thesis is that Galen's philosophical
opposition to the Stoic view of the heart distracted him from
understanding the heart's role as a circulatory pump. In defending
this view, I will first describe the scientific pointers, which
might have led Galen to a discovery of circulation. Next, I will
discuss what I consider to be the primary cause of Galen's failure:
his disagreement with the Stoics, and their spokesman, Chrysippus,
over the nature of the soul.
Many experimentally verified
facts might have directed Galen to the heart's circulatory function.
C.R.S. Harris has examined the pieces of the puzzle that Galen
held, and concluded that they could have led him to an accurate
understanding (266-397).
Galen knew a great deal about the heart and how closely it was
linked to the pulsing arteries (On Anatomical Procedures,
7.16 as cited in Harris, 378-9).
He knew that the arteries and the veins ran parallel, and were
connected (Harris,
364). He knew that both contained blood, though blood of
different types (PHP,
6.8).
