The Journey of the Circulatory System
Unless specified otherwise, information was extracted from Dr. Byron Newberry’s lecture notes or “Galen Outline: On the Natural Faculties” handout (p.4)
Above: Galen's Circulatory System
Step 1: Nutrients – or natural spirits that
the body had consumed – pass from the intestines via the portal vein to
the liver. Galen believed that the liver then transformed these nutrients into
a dark venous blood, which would nourish the entire length of the body.
Step 1
Step 2: According to Galen’s The Construction of the Embryo, the blood then left the through one of two main divisions of the vena cava: one of which was found in the middle of the spine and nourished the lower half of the body while the other nourished the upper body through the chest, throat, and heart – ultimately to the right ventricle. (pp. 184-185) Consequently, Galen considered the liver to be the center of the nutritive soul. Because the venous blood would be consumed by the parts of the body as they extracted its nourishment, blood was not returned to the heart.
Step 2
Step 3: However, some venous blood did seep over into the arterial system on the left side of the heart via holes in the septum. Here pneuma travels down the pulmonary artery from the lungs to combine with the venous blood and create what Galen considered to be the vital spirit. In The Construction of the Embryo, we learn that this blood is much brighter red, finer and warmer than that found in the venous system, as is evident when blood flows from an injured artery. (p. 185-186)
Step 3
Step 4: The heart then pumped this pneuma-enriched blood throughout the body through the arterial system. Hence, the heart was known as the origin of the emotional soul since it distributed the pneuma – breadth of life – throughout the body.
Step 4
Step 5: Some of this arterial blood was pumped to the brain, where only the finest and most pure form of pneuma was filtered out. This psychic or soul pneuma was then sent throughout the body through the nervous system. This animal spirit, as it was known, was responsible for the body’s ability to sense and move. Because of this, the brain was thought to be the seed of the rational soul.
Step 5