If the work of Hippocrates represents the foundation of Greek medicine, then the work of Galen, who lived six centuries later, is the apex of that tradition. Galen crystallized the best work of the Greek medical schools which had preceded his time. It is essentially in the form of Galenism that Greek medicine was transmitted to the Renaissance scholars.
This illustration accompanying Galen’s work shows the surgical procedures described by Galen—on the head, eye, leg, mouth, bladder and genitals— still practiced in the 16th century.
Galen hailed from Pergamon, an ancient center of civilization, containing, among other cultural institutions, a library second in importance only to Alexandria’s. Galen’s training was eclectic. Although his chief work was in biology and medicine, he was also known as a philosopher and philologist. Training in philosophy was, in Galen’s view, an essential part of the training of a doctor, not merely a pleasant addition.
His treatise entitled That the best Doctor is also a Philosopher provides a rather surprising ethical reason for the doctor to study philosophy. The profit motive, says Galen, is incompatible with a serious devotion to the art of healing. The doctor must learn to despise money. Galen frequently accused his colleagues of avarice. In order to defend his profession against this charge, he downplayed the motive of financial gain associated with becoming a doctor.
For his first professional appointment, Galen served as surgeon to the gladiators in Pergamon. In this tenure, he undoubtedly gained much experience and practical anatomical knowledge from the combat wounds he treated. After four years, he emigrated to Rome where he earned a brilliant reputation as a practitioner and a public demonstrator of anatomy. The emperors Marcus Aurelius, Lucius Verus, Commodus, and Septimius Severus sought his care.
Galen, for all his mistakes, remained an unchallenged authority in his lifetime, and his work established a legacy that continued for over a thousand years. In his day Galen said everything there was to be said on anatomy. According to reports he kept as many as 20 scribes on staff to write down his every dictum. When he died in 203 CE, serious anatomical and physiological research ground to a halt.
Although he was not a Christian, Galen’s writings reflect a belief in only one god, and he declared that the body was an instrument of the soul. This made him acceptable both to the fathers of the church and to Arab and Hebrew scholars. Galen’s mistakes perpetuated fundamental errors for nearly fifteen hundred years. Later, Vesalius, the sixteenth century anatomist, began to dispel Galen’s authority, although he regarded his predecessor with esteem.
Galen on the Soul
The fundamental principle of life, in Galenic physiology, was pneuma (air, breath). Pneuma took three forms and had three types of action: animal spirit (pneuma physicon) in the brain, center of sensory perceptions and movement; vital spirit (pneuma zoticon) in the heart, center of blood flow regulation and body temperature; and natural spirit (pneuma physicon) residing in the liver, center of nutrition and metabolism (both animal and natural spirit are known as pneuma physicon, or sometimes the animal spirit is known as pneuma psychicon).
Galen studied the anatomy of the respiratory system, and of the heart, arteries, and veins. But he did not discover the circulation of the blood in the body, and he believed that blood passed from one side of the heart to the other through invisible pores in the dividing wall. Galen was convinced that the venous and arterial systems were each sealed and separate from each other. William Harvey, discoverer of the circulation of the blood, wondered how Galen, having gotten so close to the answer, did not himself arrive at the concept of circulation.
Galen’s genius was evident in the physiological experiments he conducted on animals. The work On the Use of the Parts of the Human Body comprised seventeen books concerning this topic. To study the function of the kidneys in producing urine, he tied the ureters and observed the swelling of the kidneys. To study the function of the nerves he cut them, and thereby showed paralysis of the shoulder muscles after division of nerves in the neck and of voice loss after interruption of the recurrent laryngeal nerve.
Because his knowledge was derived for the most part from animal (principally the Barbary ape), rather than human, dissection, Galen made many mistakes, especially concerning the internal organs. For example, he incorrectly assumed that the rete mirabile, a plexus of blood vessels at the base of the brain in ungulate animals, was also present in humans. In spite of Galen’s mistakes and misconceptions, his writings reveal an astonishing wealth of accurate detail.