In science Alexandria was the unchallenged head of the Hellenistic world. Claudius Ptolemy must be ranked among the most influential astronomers of antiquity, for despite Copernicus the world is still Ptolemaic in its speech. Born at Ptolemais on the Nile (whence his name), he lived most of his life at Alexandria, where he made observations from A.D. 127 to 151. The world remembers him chiefly for his rejection of Aristarchus’ theory that the earth revolves around the sun. This immortal error was enshrined in Ptolemy’s Mathematiké Syntaxis, or “Mathematical Arrangement” of the stars. The Arabs referred to the work with a Greek superlative as Al-megisté, “The Greatest”; and the Middle Ages corrupted the phrase into Almagest, by which the book is known to history. It ruled the skies till Copernicus upset the world. And yet Ptolemy did not claim to do more than systematize the work and observation of previous astronomers, Hipparchus above all. He pictured the universe as spherical and as daily revolving around a spherical, motionless earth. Strange as this view seems to us (though there is no telling what some future Copernicus will do to our present Ptolemies), the geocentric hypothesis made it possible to compute the position of the stars and planets more accurately than the heliocentric conception could do in the state of astronomic knowledge at the time.20 Ptolemy suggested further a theory of eccentrics to explain the orbits of the planets, and discovered the evection, or orbital aberration, of the moon. He measured the moon’s distance from the earth by the parallax method still in use, and calculated it as fifty-nine times the earth’s radius. This is approximately our current reckoning; but Ptolemy followed Poseidonius in underestimating the diameter of the earth.
Just as the Syntaxis gathered ancient astronomy into its final form, so Ptolemy’s Geographical Outline summarized antiquity’s knowledge of the earth’s surface. Here, too, his industrious tables of latitude and longitude for the major cities of the globe were vitiated by accepting Poseidonius’ modest estimate of the earth; but to this encouraging mistake, as transmitted by Ptolemy, Columbus owed his belief in the possibility of reaching the Indies in a practicable time by sailing west.21 Ptolemy was the first to use the terms parallels and meridians in geography; and in his maps he successfully projected a spherical upon a flat surface. But he was a mathematician rather than an astronomer or a geographer; his work consisted chiefly in mathematical formulations. In the Syntaxis he drew up an excellent table of chords. He divided the radius of the earth into sixty partes minutae primae (“first small parts”), which became our “minutes,” and subdivided each of these into sixty partes minutae secundae (“second small parts”), now our “seconds.”
Though he made many mistakes, Ptolemy had the temper and patience of a true scientist. He tried to rest all conclusions upon observation—too seldom his own. In one field he carried out a long series of experiments: his Optica, a study of refraction, has been acclaimed as “the most remarkable experimental research of antiquity.”22 It is significant that this greatest astronomer, geographer, and mathematician of his age wrote also a Tetrabiblios, or “Four Books,” on the control of human life by the stars.
Meanwhile a minor Archimedes was giving the classic world a second chance to stage an industrial revolution. A brilliant inventor or compiler, of whom we know only the one name, Hero, issued in this ageI at Alexandria a long succession of treatises on mathematics and physics, of which several have been preserved through Arabic translations. He warned his readers frankly that the theorems and inventions which he presented were not necessarily his own, but were the accumulations of centuries. In the Dioptra he described an instrument like the theodolite, and formulated principles for measuring, by surveying, the distances to inaccessible points. In the Mechanica he considered the uses and combinations of simple devices like the wheel, axle, lever, pulley, wedge, and screw. In the Pneumatica he studied air pressure in seventy-eight experiments, most of them playful tricks; e.g., he showed how either wine or water could be made to flow from the same small orifice in the bottom of a jug by closing one or the other of the air holes at the top of the divided container.
From these amusements he was led on to make a force pump, a fire-engine pump with piston and valves, a hydraulic clock, a water organ, and a steam engine. In this contraption the steam from heated water was passed into a globe by a tube, and escaped through curved outlets at opposite sides, causing the globe to revolve in a direction contrary to that of the expelled steam. Hero’s keen sense of humor kept him from developing this invention to industrial uses. He employed steam to support a ball in mid-air, to make a mechanical bird sing, to cause a statue to blow a horn. So in the Catoptrica he studied the reflection of light and showed how to construct mirrors that would enable a person to see his back, or appear with head downward, or with three eyes, two noses, etc. He told magicians how to perform tricks by concealed apparatus. He made water pour from a font when a coin was inserted in the slot. He constructed a hidden machine by which heated water overflowed into a bucket, whose increasing weight, by pulleys, opened temple doors. In these and a hundred other ways Hero succeeded in being a thaumaturgist, and failed to become a Watt.
Alexandria had long since been the chief center of medical education. There were famous schools of medicine at Marseilles, Lyons, Saragossa, Athens, Antioch, Cos, Ephesus, Smyrna, and Pergamum; but medical students came to the Egyptian capital from every province. Even as late as the fourth century, when Egypt was in decline, Ammianus Marcellinus wrote that “it is enough to commend a physician’s skill if he can say that he was trained at Alexandria.”24 Specialization was progressing; “no one can be a universal physician,” said Philostratus (ca. A.D. 225); “there must be specialists for wounds, fevers, eyes, consumption.”25 Dissection of cadavers was practiced at Alexandria, and there seem to have been cases of human vivisection.26 Surgery was probably as well developed there in the first century A.D. as anywhere in Europe before the nineteenth century. Women physicians were not rare; one of them, Metrodora, wrote an extant treatise on diseases of the womb.27 Great names adorned the medical history of this age: Rufus of Ephesus, who described the anatomy of the eye, distinguished between motor and sensory nerves, and improved methods for stopping the flow of blood in surgery; Marinus of Alexandria, famous for his operations on the skull; and Antyllus, the greatest ophthalmologist of the time. Dioscorides of Cilicia (A.D. 40-90) wrote a Materia Medica which scientifically described 600 medical plants so well that his book remained the chief authority on its subject until the Renaissance. He recommended medicated pessaries for contraception;28 and his recipe for wine of mandragora to produce surgical anesthesia was successfully applied in 1874.29
Soranus of Ephesus, about A.D. 116, published a treatise on the diseases of women and the birth and care of children; it ranks only below the Hippocratic collection and the works of Galen among the extant products of ancient medicine. He describes a vaginal speculum and an obstetric chair, gives an excellent anatomy of the uterus, offers almost modern dietetic and operative advice, such as bathing the eyes of the newborn child with oil,30 suggests half a hundred contraceptive devices, mostly by vaginal medication,31 and (unlike Hippocrates) allows abortion where delivery would endanger the mother’s life.32 Soranus was the greatest gynecologist of antiquity; no advance was made on his work till Paré, fifteen centuries after him. If all his forty treatises were extant we should probably rank him with Galen.
The most famous physician of the period was the son of a Pergamese architect, who named him Galenus, i.e., quiet and peaceable, in the hope that he would not take after his mother.33 At fourteen the youth found his first love in philosophy, from whose dangerous lure he was never freed. At seventeen he turned to medicine, studied in Cilicia, Phoenicia, Palestine, Cyprus, Crete, Greece, and Alexandria (a mobility typical of ancient scholars), served as a surgeon in the gladiatorial school at Pergamum, and practiced for a time in Rome (A.D. 164-68). There his successful cures brought him many rich patients, and his lectures drew distinguished audiences. His repute rose to such a point that people wrote to him from every province for medical advice; and he confidently prescribed by mail. His good father, forgetting the purpose of his name, had counseled him to join no sect or party and always to tell the truth. Galen obeyed, exposed the ignorance and venality of many physicians in Rome, and in a few years had to flee from his enemies. Marcus Aurelius called him back to care for young Commodus (169) and tried to take him on a Marcomannic campaign; but Galen was clever enough to be soon back in Rome. Thereafter we know nothing of him except his works.
He was almost as voluminous as Aristotle. Of 500 volumes ascribed to him some 118 have survived, covering in 20,000 pages all branches of medicine and several fields of philosophy. They are of little medical value today, but they abound in incidental information and in the vitality of a vigorous and controversial spirit. His fondness for philosophy had given him a bad habit of drawing large deductions from small inductions; his faith in his own knowledge and powers often betrayed him into a dogmatism impossible to a scientific mind; and his great authority prolonged for centuries the life of serious errors. Nevertheless, he was an accurate observer and the most experimental of ancient physicians. “I confess the disease from which I have suffered all my life—to trust … no statements until, so far as possible, I have tested them for myself.”34 Forbidden by the Roman government to dissect the human body alive or dead, he dissected and vivisected animals, and sometimes too readily concluded to human anatomy from a study of apes, dogs, cows, and pigs.
Despite his limitations Galen made more contributions to anatomy than any other observer in antiquity. He described accurately the bones of the cranium and the spinal column, the muscular system, the lacteal vessels, the ducts of the lingual and submaxillary glands, and the valves of the heart. He showed that an excised heart can continue to beat outside the body; he proved that the arteries contain blood, not air (as the Alexandrian school had taught for 400 years). He missed anticipating Harvey; he thought that most of the blood traveled forth as well as back in the veins, while the remainder, mixed with air from the lungs, moved to and fro in the arteries. He was the first to explain the mechanism of respiration, and brilliantly conjectured that the principal element in the air we breathe is also that which is active in combustion.35 He differentiated pleurisy and pneumonia, described aneurism, cancer, and tuberculosis, and recognized the infectious nature of the last. Above all, he founded experimental neurology. He made the first experimental sections of the spinal cord, determined the sensory and motor functions of each segment, understood the sympathetic system, recognized seven of the twelve pairs of cranial nerves, and caused aphasia at will by cutting the laryngeal nerve. He showed that injuries to one side of the brain produce derangements in the opposite side of the body. He cured the sophist Pausanias of numbness in the fourth and fifth fingers of the left hand by stimulating the brachial plexus in which the ulnar nerve arises that controls those fingers.36 He was so skilled in symptomatology that he preferred to diagnose without questioning the patient.37 He made much use of diet, exercise, and massage, but he was also an expert on drugs and traveled widely to secure rare medicines. He condemned the prescription of offal and urine, still popular with some of his contemporaries,38 recommended dried cicadas for colic, applied goat dung to a tumor, and gave a long list of illnesses that could be cured by theriac—a famous drug made as an antidote for Mithridates the Great, daily imbibed by Marcus Aurelius, and containing the flesh of snakes.39
He tarnished his record as an experimentalist by a torrent of precipitate theory. He ridiculed magic and spells, accepted divination by dreams, and thought that the phases of the moon affected the condition of patients. He took up Hippocrates’ notion of the four humors (blood and phlegm, black and yellow bile),II added a dash of Pythagoras’ doctrine of four elements (earth, air, fire, and water), and tried to reduce all diseases to derangement of these humors or these elements. He was a firm vitalist, convinced that a pneuma, a vital breath or spirit, pervaded and activated every part of the body. Mechanistic interpretations of biology had been advanced by several physicians, as for example by Asclepiades, who held that physiology should be treated as a branch of physics; Galen objected that whereas a machine is merely the sum of its parts, an organism implies the purposive control of the parts by the whole. And just as purpose alone can explain the origin, structure, and function of organs, so the universe, Galen thought, can be understood only as the expression and instrument of some divine plan. God, however, operates solely through natural laws; there are no miracles, and the best revelation is Nature herself.
Galen’s teleology and monotheism won him favor with Christians, as later with Moslems. Nearly all his writings were lost to Europe in the chaos of the barbarian invasions, but in the East they were preserved by Arab scholars, and were translated from Arabic into Latin from the eleventh century onward. Galen became then an uncriticized authority, an Aristotle for medieval medicine.
The last creative age of Greek science ended with Ptolemy and Galen. Experiment ceased, dogma ruled; mathematics relapsed into restatements of geometry, biology into Aristotle, natural science into Pliny; and medicine marked time until the Arab and Jewish physicians of the Middle Ages renewed the noblest of the sciences.