Galen

Then comes Galen (AD 129-199), whose ideas formed the basis for all medical discussion until virtually the 17th century. Galen summed up all the ideas then current, building up a paradigm which incorporated the atoms of Pythagorus, the four elements of Empedocles, the perfectly spherical divine universe of Plato, the 'primum mobile', the vegetable, animal and rational souls, and the quintessence of Aristotle, the four humours of Empedocles and Hippocrates and Erasistratus' notion that nerves are hollow tubes which carry quintessence from the brain, and added his own discovery of blood in the arteries with the contention that arterial blood was intermixed with quintessence. Galen wrote

"In the universe there are four elements - fire, air, water and earth; and in the living body there are four humours, black bile, yellow bile, sanguine and phlegm. Out of the excess or deficiency or misproportion of these four humours there arise disease; by restoring the correct proportion diseases are cured" (Bergland, p40)

Galen further assigned the three largest organs of the body to be the seat of the three Aristotlean souls; the liver was the seat of the vegetative soul, the heart was the seat of the animal soul and the brain was the seat of the rational soul.

The brain received 'pneuma' from the lungs via the arteries and converted it into animal spirit which it pumped out through the nerves to animate the muscles` The Pneuma is drawn in from the world, enters the lungs through the trachea and is conveyed to the heart via the pulmonary artery. Food is converted to natural spirits in the liver. The natural spirits are then conveyed to the heart via a "hepatic vein" where much of it is cleaned and returned to the lungs but some is mixed with the pneuma and sent to the brain as the vital spirits. The function of the brain was to distill the vital spirits still further, converting it to animal spirits which was an ethereal substance passed into the (then thought to be) hollow nerves and distributed throughout the body, thus animating the body.

Galen's physiological teaching (after C.Singer Greek Biology and Greek Medicine)

Note: Galen "distinguished three ventricles: one at the front of the brain, divided in two; one in the centre; and one at the rear. He noted that if the substance of the brain was cut at a given point, the animal did not lose consciousness or movement. For this to happen, the section had to penetrate as far as the ventricles. A lesion of the posterior ventricle had the most disturbing effect on the animal. Galen demonstrated that the brain played the central role in controlling bodily and mental activity andtivity originated in the cerebral substance itself...For Plato and Galen the rational soul had its seat in the brain." (Changeux, 1985, p7)

The rational soul had the functions of imagination, reason and memory, and these functions were assigned to the ventricles. Because the function of the brain was to distribute 'animal spirit' throughout the body, it seemed obvious that the fluid filled ventricles should be the major functional units of the brain, rather than the white matter and the grey matter surrounding them.