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Herophilus of Chalcedon: 335–280 BC
Herophilus was born in Chalcedon, a settlement on the Bosporus, directly across from ancient Byzantium. As a teenager, he moved to Cos where the medical faculty formed by Hippocrates was located. At this time, Hippocrates had been dead for more than 60 years. Nonetheless, he greatly influenced Herophilus' work.
After completing his medical education, Herophilus traveled to Alexandria in 300 bc at about the same time that the city had become fully equipped to support medical education. It was there that Herophilus, along with his contemporary Erasistratus, was able to perform systemic dissections and vivisections on humans and animals, because Ptolemy I and Ptolemy II had authorized vivisections of criminals sentenced to death. In fact, Herophilus often performed such vivisections publicly so that he could better demonstrate the effects of his methods. This practice on live humans was occasionally opposed by religious and moral beliefs. Cornelius Celsus wrote as follows:
Moreover, since both pains and various types of diseases arise in the internal parts, they [scil. the "Rationalists"] think that no one who is ignorant of these parts can apply remedies to them. It therefore is necessary to dissect the bodies of the dead and to examine their viscera and intestines. Herophilus and Erasistratus, they say, did this in the best way by far when they cut open people who were alive, criminals out of prison, received from kings. And while breath still remained in these criminals, they inspected those parts which nature previously had concealed, also their position, color, shape, size, arrangement, hardness, softness, smoothness, connection, and the projections and depressions of each, and whether anything is inserted into another thing or receives a part of another into itself. For, they say, when pain occurs internally, it is impossible for one who has not learned in which part each internal organ or intestine lies, to know what hurts the patient. Nor can that part which is ill be treated by one who does not know what it is. And when a person's viscera are exposed by a wound, one who does not know the color of an [internal] part in its healthy state, cannot recognize which part is intact and which damaged; thus he cannot even come to the aid of the damaged parts. External remedies also can be applied more suitably by people acquainted with the positions, shapes, and size of the internal parts… . Nor is it cruel, as most people maintain, that remedies for innocent people of all times should be sought in the sacrifice of people guilty of crimes, and of only a few such people at that.
Celsus and later Tertullian remarked that Herophilus vivisected at least 600 live prisoners.
Herophilus contributed to the knowledge of brain anatomy as he dissected the ventricles, choroid plexus, venous sinuses, arachnoid, cranial nerves and their foramina, and many other neuroanatomical structures. He named certain structures of the brain based on their shape, for example, the cerebrum (encephalon), cerebellum (parencephalon), torcular herophili, calamus scriptorius, and choroid plexus. He described the bones forming the skull, the intervening sutures, and the membranous coverings of the brain. He described the lower brainstem and spinal cord as one structure he referred to as "spinal marrow." Herophilus and Erasistratus established the importance of the brain and the sensory and motor functions of the nerves.
According to Galen, Herophilus was the first to describe the connection between the cerebrum and cerebellum through the ventricular system and the structural distinction between the cerebrum and cerebellum. Herophilus extensively studied the lateral, third, and fourth ventricles because he thought they were part of the seat of the soul. He also described the inner lining of the ventricles as "choroid meninx or choroid twisted clusters." Galen writes about Herophilus' description of the venous sinuses: "At the crown of the head the folds of the membrane [sinus transversus] that conduct the blood come together into a common space like a cistern, and for this very reason it was Herophilus' custom to call it "wine vat" [torcular herophili]. From this point, as from some acropolis, they [sinuses] send forth canals to all the parts lying below them." Herophilus not only named the confluence of sinuses (torcular herophili), but he also compared it to the confluence in the ox, noting that it divides evenly in the ox but unevenly in humans.
When describing the human cranial nerves, Herophilus and Marinus (a contemporary who lived ad 70–130) debated the number of cranial nerves, especially the lower ones, that originate from the lower pons and medulla and the spinal roots of the accessory nerves. Herophilus suggested that the facial nerve did not exit the cranial fossa but ended as it enters the internal auditory meatus, which he called the "blind foramen." He described the cavity in the floor of the fourth ventricle as the calamus scriptorius (calamus means "reed pen") because this cavity resembled the groove of a writing pen. A confluence of sinuses in the skull was originally named torcular herophili after him.
Herophilus differentiated between nerves and blood vessels and discovered the differences between motor and sensory nerves. He believed that the sensory and motor nerves exited the brain and that neural transmission occurred by means of the pneuma, which was thought to be a substance that flowed through the arteries along with the blood. Although Herophilus stated that diseases occurred when an excess of one of the four humors impeded the pneuma from reaching the brain, it is clear that he studied the base of the brain and the cranium in detailed fashion to make such observations.
Herophilus pioneered the physiology of nerves, considering them responsible for voluntary movement. He possessed a considerable amount of knowledge on at least seven cranial nerves: the optic, oculomotor, trigeminal, motor root of the trigeminal, facial, auditory, and hypoglossal nerves. According to Galen, Herophilus called the optic nerve "conduits" because it displays visible channels for the passage of animal spirits. Herophilus also mentioned a single nerve that has three roots coming from the brain. This nerve was further explained by Galen as the glossopharyngeal, accessory, and vagus nerves "wrapped" together in one sheet. Herophilus described the structures entering the eye as two large nerves (V1 and optic) and a smaller one (oculomotor). He also first described the styloid process, naming it after styloi, a pen used in Alexandria to write on wax paper. He also compared it to the famous lighthouse on the Island of Pharos (Fig. 7). Herophilus also studied the blood vessels at the base of the brain, which were named rete mirabile. Unfortunately, none of the detailed writings of Herophilus survive, although many of his contributions were mentioned and confirmed by later historians or physicians.
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Figure 7.
A: Photograph of a replica of the famous lighthouse of Alexandria at the Window of the World cultural park in Changsha, China. Image available at http://commons.wikimedia.org/wiki/File:Lighthouse_of_Alexandria_in_Changsha.jpg. B: Drawing of Alexandria's lighthouse by archaeologist Hermann Thiersch (1909) considered to be an excellent rendering of the original structure. Image available at http://en.wikipedia.org/wiki/File:Lighthouse_-_Thiersch.gif. C: Comparative image from an original drawing by Austrian architect Johann Bernhard Fischer von Erlach, who illustrated the Alexandrian Pharos from travelers' descriptions. The Pharos, the most recognized landmark of Alexandria, was one of the Seven Wonders of the Ancient World and one of the tallest structures of the ancient world. Built in 283 BC, it was about 140 m high, and for many years it guided ships for miles in the Mediterranean Sea. This well-known monument served as a lighthouse to the bay of Alexandria in ancient Egypt and was a beacon of science, hope, and light in the Dark Ages. The lighthouse underwent various renovations and embellishments but was badly damaged in the earthquakes of ad 956, 1320, and 1323. In 1480 the rampart had disappeared and a fort was built upon it. A major archaeological expedition discovered remains of the Pharos in 1994. Image available in Bergk JA: Museum des Wundervollen, oder Magazin des Ausserordentlichen in der Natur, der Kunst und im Menschenleben. Leipzig: Baumgärtner, 1803–1805.
Herophilus also introduced many of the scientific terms used to this day to describe anatomical phenomena. He was among the first to introduce the notion of conventional terminology, as opposed to the use of "natural names." He created terms to systematically describe the objects of study, named them for the first time, and established nomenclature so that there was some uniformity for study and description.
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