A HISTORY OF THE HEART
"For the concept of a circuit of the blood does not destroy, but rather advances traditional medicine." -- William Harvey, 1649
The heart has played an important role in understanding the body since antiquity. In the fourth century B. C., the Greek philosopher Aristotle identified the heart as the most important organ of the body, the first to form according to his observations of chick embryos. It was the seat of intelligence, motion, and sensation -- a hot, dry organ. Aristotle described it as a three-chambered organ that was the center of vitality in the body. Other organs surrounding it (e.g. brain and lungs) simply existed to cool the heart.
In his treatise On the Usefulness of the Parts of the Body, written in the second century A. D., Galen reaffirmed common ideas about the heart as the source of the body's innate heat and as the organ most closely related to the soul: "The heart is, as it were, the hearthstone and source of the innate heat by which the animal is governed." He also observed carefully many of its unusual physical properties. "The heart is a hard flesh, not easily injured. In hardness, tension, general strength, and resistance to injury, the fibers of the heart far surpass all others, for no other instrument performs such continuous, hard work as the heart." He argued that the expansion and contraction of the heart was a function of its role as an intelligent organ: "The complexity of [the heart's] fibers... was prepared by Nature to perform a variety of functions... enlarging when it desires to attract what is useful, clasping its contents when it is time to enjoy what has been attracted, and contracting when it desires to expel residues."
However, Galen was not afraid to contradict others in matters of detailed anatomy, such as Aristotle's claim that the heart is the origin of the nerves. He further argued that the heart was secondary to the liver in its importance to the operations of the body, since it was not the site of the production of the humors. His ideas generally predominated until the mid-seventeenth century.
As the scientific and philosophical writings of Aristotle became more important in medieval Islam and Europe, physicians began to puzzle over the discrepencies between these two ancients. At the beginning of the eleventh century, for example, Avicenna in his Canon of Medicine integrated Aristotle's ideas within his largely Galenic physiology when he wrote: "[The heart is the] root of all faculties and gives the faculties of nutrition, life, apprehension, and movement to several other members." He believed that heart produced breath, the "vital power or innate heat" within the body; it was an intelligent organ that controlled and directed all others. He identified the pulse as "a movement in the heart and arteries which takes the form of alternate expansion and contraction, whereby the breath becomes subjected to the influence of the air inspired." Despite Avicenna's recommendation to pay more attention to the heart, and the writings of the Syrian jurist-physician Ibn al-Nafis in the thirteenth century on pulmonary transit, most medical practitioners preferred Galen's idea that the veins connected the operations of the liver to the heart, which circulated vital spirits throughout the body via the arteries. Look at this published image of the heart on the left. How does it exemplify the vagueness of its anatomy?
The Renaissance revival of anatomy made it possible for physicians to clarify basic structures in the heart. By this point, they commonly agreed the heart was divided into four parts with two ventricles and two auricles. Wondering at the confusion over the divisions of the heart's chambers, Andres de Laguna wrote in 1535, "The heart has only two ventricles, a right and a left. I do not know what is the meaning of the riddle proposed by the people who add a third ventricle to the heart unless perhaps they intend by it those pores which are found in the septum." The drawing on the right by Leonardo da Vinci, probably from the 1490s, illustrates the typical Renaissance image of the heart as a Galenic organ with two basic chambers dividing by the septum. Look closely at it. What function would the "pores" that Laguna mentioned have served? Can you see them?
Leonardo, for all his ability to draw and observe the heart with a great deal of accuracy, did not deviate significantly from Galen's account of it. "The heart of itself is not the beginning of life but is a vessel made of dense muscle vivified and nourished by an artery and a vein as are the other muscles. The heart is of such density that fire can scarcely damage it." Yet he offered a more elaborate mechanical account of the heart, underscoring the relationship between heat and motion. He began to puzzle over the actual movement of the heart, writing:
"At one and the same time, in one and the same subject, two opposite motions cannot take place, that is, repentance and desire. Therefore, if the right upper [auricle] and lower ventricles are one and the same, it is necessary that the whole should cause at the same time one and the same effect and not two effects arising from diametrically opposite purposes as one sees in the case of the right ventricle with the lower, for whenever the lower contracts, the upper dilates to accommodate the blood which has been driven out of the lower ventricle."
Look at his drawing on the left above. How does it differ from his earlier image of the heart? To what extent does it reflect his interests in physics and engineering?
By the middle of the sixteenth century, a handful of physicians had begun to wonder about several key aspects of the traditional heart. Were the arteries truly separate from the veins? Was the heart really divided by its septum in such a way that arterial and venous fluids were physically distinct? Was the septum the key site of interchange between blood and pneuma? Both Michael Servetus and Realdo Colombo returned to theme raised by Ibn al-Nafis: pulmonary transit. Andreas Vesalius, who initially accepted the idea of the porous septum, eventually rejected it because he found that he could not see it in repeated dissections of cadavers. Yet it was not until the English physician William Harvey wrote his On the Circulation of the Blood (1628) that a viable alternative to Galenic physiology became widely accepted.
Harvey supported the Aristotelian notion of the heart. He wrote in 1653: "The heart is situated at the 4th and 5th ribs. Therefore [it is] the principal part because [it is in] the principal place, as in the center of a circle, the middle of the necessary body." He examined carefully the function of all of its different parts and came to a reverse conclusion of Galen and his medieval and Renaissance readers: he believed that the heart was actively at work when it was small, hard and contracted (systole), expelling blood, and at rest when it was large and filled with blood (diastole). In 1628, he wrote: "[T]he heart's one role is the transmission of the blood and its propulsion,, by means of the arteries, to the extremities everywhere." Needless to say, Harvey firmly dismissed the idea of a porous septum.
Yet he did not challenge the metaphysical intepretation of the heart. The heart, as Master Nicolaus had aptly observed in the late twelfth century, was the primary "spiritual member" of the body. As such, it was the seat of all emotions. "If indeed from the heart alone rise anger or passion, fear, terror, and sadness; if from it alone spring shame, delight, and joy, why should I say more?" wrote Andreas de Laguna in 1535. Harvey metaphorically described the heart as the "king" or "sun" of the body to underscores its cosmological significance. Popular imagery of the heart, such as this image to your left from the mid-seventeenth century, combined scientific and cultural ideas. This image, not from a medical text, effectively conveys a detailed external anatomy of the heart while demonstrating its cultural significance. What do you think the message is?
By the end of seventeenth century, the anatomical knowledge of the heart was surprisingly accurate and Harvey's ideas were widely accepted. The French philosopher Rene Descartes, who was one of the first scholars to accept Harvey's new theory, too his ideas a step further when he argued that the heart was like a pump or, better yet, a combustion engine. The heart became an important site for debating the pros and cons of mechanistic and vitalistic accounts of the body, since it served both agendas.
QUESTIONS: WHAT MADE THE HEART A SIGNIFICANT ORGAN? WHAT MADE IT, ANATOMICALLY AND PHILOSOPHICALLY, SO HARD TO UNDERSTAND?
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