Some of the earliest advances in biology occurred within the fields of what are now known as anatomy (the study of the structure of living organisms) and physiology (the study of how living organisms function). In the Mediterranean, Greek physicians and natural philosophers began inquiries into these fields from about 500 BCE. Their investigations included dissections of dead human and animal bodies and animal vivisections (the cutting open of live animals). For a limited period, they also included some human vivisections. However, due to religious teachings and taboos, all experimental cutting open of humans, whether alive or dead, ceased from about 250 BCE.
Galen’s Experiments
Although the Greeks achieved some progress in understanding anatomy and physiology from their dissections and vivisections, the most significant medical advances in classical antiquity occurred during the 2nd century CE, with the experiments carried out by Galen of Pergamon, physician to Emperor Marcus Aurelius in Rome. Unlike those of his predecessors, Galen’s experiments were carried out exclusively on animals—mainly monkeys, but also pigs, goats, dogs, oxen, and even an elephant—though he also treated people who had suffered deep wounds, which taught him much about human anatomy. One way in which Galen sought to establish aspects of how the body functioned was by cutting away or disabling certain body parts of animals and then observing the effects. In one vivisection—carried out on a strapped-down, squealing pig—he cut two of the laryngeal nerves that carry signals from the brain to the larynx, or voice box. The pig continued to struggle but now did so noiselessly. The cutting of other nerves coming from the pig’s brain did not have the same effect. This proved the function of these laryngeal nerves. Since it showed that the brain used nerves to control muscles involved in speech, the experiment supported Galen’s opinion that the brain is the seat of voluntary action, including the choice of words (in humans) and other vocalizations (in animals).
Galen went on to show that cutting the laryngeal nerves in some other animals also eliminated vocalization. Further vivisections included tying off an animal’s ureters—the tubes that connect the kidneys to the bladder. The results proved that urine is formed in the kidneys—not in the bladder, as previously thought—and is then carried via the ureters to the bladder. Among other advances, Galen was also the first to recognize that blood moves through blood vessels, although he did not fully understand the workings of the circulatory system.
Questioning Galen’s Work
Galen is generally considered the greatest experimental anatomist and physiologist of the classical era, and his ideas about biology and medicine were influential in Europe for more than 1,400 years. However, many of his observations based on animal dissections were wrongly applied to humans. His account of the arrangement of blood vessels in the human brain, for example (based solely on the dissection of ox brains), was proved wrong by Arab scholar Ibn al-Nafis in 1242. Yet, the unquestioning adherence to Galen’s beliefs persisted for generations of physicians and hindered medical progress in Europe right up to the time of the Flemish anatomist Vesalius in the 16th century.
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