IV. THEOPHRASTUS, HEROPHILUS, ERASISTRATUS

Zoology never rose again in antiquity to the level that it had reached in Aristotle’s History of Animals. Probably by an agreed division of labor his successor Theophrastus wrote a classic treatise, The History of Plants, and a more theoretical discussion called The Causes of Plants.Theophrastus loved gardening, and knew every aspect of his subject. In many ways he was more scientific than his master, more careful of his facts, and more orderly in his exposition; a book without classification, he said, was as untrustworthy as an unbridled horse.³⁵ He divided all plants into trees, bushes, shrubs, and herbs, and distinguished the chief parts of a plant as root, stem, branch, twig, leaf, flower, and fruit—a classification not improved on till A.D. 1561.³⁶ “A plant,” he wrote, “has the power of germination in all its parts, for it has life in them all. . . . The methods of generation of plants are these: spontaneous, from a seed, a root, a piece torn off, a branch, a twig, pieces of wood cut up small, or from the trunk itself.”³⁷ He had no clear idea of sexual reproduction in plants, except in a few species like the fig tree or the date palm; here he followed the Babylonians in describing fertilization and caprification. He discussed the geographical distribution of plants, their industrial uses, and the climatic conditions most conducive to their health. He studied the minutiae of half a thousand species with an accuracy of detail astonishing in an age that had no microscope. Twenty centuries before Goethe he recognized that the flower is a metamorphosed leaf.³⁸ He was a naturalist in more ways than one, stoutly rejecting the supernatural explanations current in his day for certain curiosities of botany.³⁹ He had all the inquisitiveness of a scientist, and did not think it beneath his dignity as a philosopher to write monographs on stones, minerals, weather, winds, weariness, geometry, astronomy, and the physical theories of the pre-Socratic Greeks.⁴⁰ “If there had been no Aristotle,” says Sarton, “this period would have been called the time of Theophrastus.”⁴¹

Theophrastus’ ninth “book” summarized all that the Greeks knew about the medicinal properties of plants. One passage hinted at anesthesia in describing “dittany, a plant especially useful for labor in women; people say that either it makes labor easy, or it stops the pains.”⁴² Medicine progressed rapidly in this age, perhaps because it had to keep pace with the novel and multiplying diseases of a complex urban civilization. The Greek study of Egyptian medical lore stimulated a fresh advance. The Ptolemies were ruthlessly helpful; they not only permitted the dissection of animals and cadavers, but turned over some condemned criminals for vivisection.⁴³ Under these encouragements human anatomy became a science, and the absurdities into which Aristotle had fallen were substantially reduced.

Herophilus of Chalcedon, working at Alexandria about 285, dissected the eye and gave a good account of the retina and the optic nerves. He dissected the brain, described the cerebrum, the cerebellum, and the meninges, left his name in the torcular Herophili*and restored the brain to honor as the seat of thought. He understood the role of the nerves, originated their division into sensory and motor, and separated the cranial from the spinal nerves. He distinguished arteries from veins, discerned the function of the arteries as carrying blood from the heart to various parts of the body, and in effect discovered the circulation of the blood nineteen centuries before Harvey.⁴⁴ Following a suggestion of the Coan physician Praxagoras, he included the taking of the pulse in diagnosis, and used a water clock to measure its frequency. He dissected and described the ovaries, the uterus, the seminal vesicles, and the prostate gland; he studied the liver and the pancreas, and gave to the duodenum the name that it still bears.⁴⁵“Science and art,” wrote Herophilus, “have nothing to show, strength is incapable of effort, wealth is useless, and eloquence is powerless, where there is no health.”⁴⁶

Herophilus was, so far as we can now judge, the greatest anatomist of antiquity, and Erasistratus was the greatest physiologist. Born in Ceos, Erasistratus studied in Athens, and practiced medicine in Alexandria about 258 B.C. He distinguished more carefully than Herophilus between cerebrum and cerebellum, and made experiments on living subjects to study the operation of the brain. He described and explained the working of the epiglottis, the lacteal vessels of the mesentery, and the aortic and pulmonary valves of the heart. He had some notion of basal metabolism, for he devised a crude respiration calorimeter⁴⁷ Every organ, said Erasistratus, is connected with the rest of the organism in three ways—by artery, vein, and nerve. He sought to account for all physiological phenomena by natural causes, rejecting any reference to mystical entities. He discarded the humoral theory of Hippocrates, which Herophilus had retained. He conceived the art of medicine as prevention through hygiene rather than as cure through therapy; he opposed the frequent use of drugs and bloodletting, and relied upon diet, bathing, and exercise.⁴⁸

Such men made Alexandria the Vienna of the ancient medical world. But there were great schools of medicine also at Tralles, Miletus, Ephesus, Pergamum, Taras, and Syracuse. Many cities had a municipal medical service; the physicians so employed received a modest salary, but were honored for making no distinction between rich and poor, free and slave, and for devoting themselves to their work at any time and risk. Apollonius of Miletus fought the plague in near-by islands without reward; when all the doctors of Cos were laid low by an epidemic which they had labored to control, others came to their rescue from neighboring towns. Many public decrees of gratitude were issued to Hellenistic physicians; and though ancient jests railed at mercenary incompetence, the great profession kept high that standard of ethics which had come down to it from Hippocrates as its most precious inheritance.