The Birth of Modern Medicine

Medical science advanced very little during the Middle Ages. Even though some of the most famous medical schools of Europe were founded during this era, the professors taught medicine primarily as a dogmatic commentary on Galen and Aristotle, not as a field of original research. Medieval medical illustrations were crude representations of the body that served more to decorate a page than to depict the body realistically (fig. 1.2). Some were astrological charts that showed which sign of the

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4 Part One Organization of the Body

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Figure 1.2 Medieval Medical Illustration. This figure depicts a pregnant woman with a fetus in the uterus and shows the heart, lungs, arteries, and digestive tract.

zodiac was thought to influence each organ of the body. From such pseudoscience came the word influenza, Italian for influence.

Free inquiry was less inhibited in the Muslim world than in Christendom. Ibn Sina (980-1037), known in the West as Avicenna or "the Galen of Islam," studied Galen and Aristotle, combined their findings with original discoveries, and questioned authority when the evidence demanded it. Muslim medicine soon became superior to Western medicine, and Avicenna's textbook, The Canon of Medicine, became the leading authority in European medical schools until the sixteenth century.

Modern medicine began around the sixteenth century in the innovative minds of such people as the anatomist Andreas Vesalius and the physiologist William Harvey. Andreas Vesalius (1514-64) taught anatomy in Italy. In his time, cadaver dissection had resumed for the purpose of autopsies and gradually found its way into the training of medical students throughout Europe. Dissection was an unpleasant business, however, and most professors considered it beneath their dignity. In these days before refrigeration or embalming, the odor from the decaying cadaver was unbearable. Dissections were conducted outdoors in a nonstop 4-day race against decay. Bleary medical students had to fight the urge to vomit, lest they incur the wrath of an overbearing professor. Professors typically sat in an elevated chair, the cathedra, reading dryly from Galen or Aristotle while a lower-ranking barber-surgeon removed putrefying organs from the cadaver and held them up for the students to see. Barbering and surgery were considered to be "kindred arts of the knife"; today's barber poles date from this era, their red and white stripes symbolizing blood and bandages.

Vesalius broke with tradition by coming down from the cathedra and doing the dissections himself. He was quick to point out that much of the anatomy in Galen's books was wrong, and he was the first to publish accurate illustrations for teaching anatomy (fig. 1.3). When others began to plagiarize his illustrations, Vesalius published the first atlas of anatomy, De Humani Corporis Fabrica (On the Structure of the Human Body), in 1543. This book began a rich tradition of medical illustration that has been handed down to us through such milestones as Gray's Anatomy (1856) and the vividly illustrated atlases and textbooks of today.

Anatomy preceded physiology and was a necessary foundation for it. What Vesalius was to anatomy, the Englishman William Harvey (1578-1657) was to physiology. Harvey is remembered especially for a little book he published in 1628, On the Motion of the Heart and Blood in Animals. Authorities before him believed that digested food traveled to the liver, turned into blood, and then traveled through the veins to organs that consumed it. Harvey measured cardiac output in snakes and other animals, however, and concluded that the amount of food eaten could not possibly account for so much blood. Thus, he inferred that blood must be recycled—pumped out of the heart by way of arteries and returned to the heart by way of veins. Capillaries, the connections between arteries and veins, had not been discovered yet, but Harvey predicted their existence.

Modern medicine also owes an enormous debt to two inventors from this era. Antony van Leeuwenhoek (an-TOE-nee vahn LAY-wen-hook) (1632-1723), a Dutch textile merchant, was the first to invent a microscope capable of visualizing single cells. In order to examine the weave of fabrics more closely, he ground a beadlike lens and mounted it in a metal plate equipped with a movable specimen clip (fig. 1.4). This simple (single-lens) microscope magnified objects 200 to 300 times. Out of curiosity, Leeuwenhoek examined a drop of lake water and was astonished to find a variety of microorganisms—"little animalcules," he called them, "very prettily a-swimming."

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Humani Corp
Figure 1.3 The Art of Vesalius. Andreas Vesalius revolutionized medical illustration with the comparatively realistic art prepared for his 1543 book, De Humani Corporis Fabrica.

He went on to observe practically everything he could get his hands on, including blood cells, blood capillaries, sperm, and muscular tissue. Probably no one in history had looked at nature in such a revolutionary way. Leeuwenhoek opened the door to an entirely new understanding of human structure and the causes of disease. He was praised at first, and reports of his observations were eagerly received by scientific societies, but this public enthusiasm did not last. By the end of the seventeenth century, the microscope was treated as a mere toy for the upper classes, as amusing and meaningless as a kaleidoscope. Leeuwenhoek had even become the brunt of satire.

Leeuwenhoek's most faithful admirer was the Englishman Robert Hooke (1635-1703), who developed the first

Chapter 1 Major Themes of Anatomy and Physiology 5

Lens

Specimen holder

Focusing screw

Lens

Specimen holder

Focusing screw

Figure 1.4 Leeuwenhoek's Simple Microscope. (a) Modern replica. (b) Viewing a specimen with a Leeuwenhoek microscope.

Figure 1.4 Leeuwenhoek's Simple Microscope. (a) Modern replica. (b) Viewing a specimen with a Leeuwenhoek microscope.

practical compound microscope—a tube with a lens at each end. The second lens further magnified the image produced by the first (fig. 1.5a). Hooke invented many of the features found in microscopes used today: a stage to hold the specimen, an illuminator, and coarse and fine focus controls. His microscopes produced poor images with blurry edges (spherical aberration) and rainbow-colored distortions (chromatic aberration), but poor images were better than none. Although Leeuwenhoek was the first to see cells,

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Physiology: The Unity of Anatomy and Physiology Companies, 2003 Form and Function, Third Edition

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6 Part One Organization of the Body

Figure 1.5 Hooke's Compound Microscope. (a) The compound microscope had a lens at each end of a tubular body. (b) Hooke's drawing of cork cells, showing the thick cell walls characteristic of plants.

Hooke named them. In 1663, he observed thin shavings of cork with his microscope and observed that they "consisted of a great many little boxes," which he called cells after the cubicles of a monastery (fig. 1.5b). He published these observations in his book, Micrographia, in 1665.

In nineteenth-century Germany, Carl Zeiss (1816-88) and his business partner, physicist Ernst Abbe (1840-1905), greatly improved the compound microscope, adding the condenser and developing superior optics that reduced chromatic and spherical aberration. Chapter 3 describes some more recently invented types of microscopes. With improved microscopes, biologists began eagerly examining a wider variety of specimens. By 1839, botanist Matthias Schleiden (1804-81) and zoologist Theodor Schwann (1810-82) concluded that all organisms were composed of cells. This was the first tenet of the cell theory, added to by later biologists and summarized in chapter 3. The cell theory was perhaps the most important breakthrough in biomedical history, because all functions of the body are now interpreted as the effects of cellular activity.

Although the philosophical foundation for modern medicine was largely established by the time of Leeuwen-

hoek, Hooke, and Harvey, clinical practice was still in a dismal state. Few doctors attended medical school or received any formal education in basic science or human anatomy. Physicians tended to be ignorant, ineffective, and pompous. Their practice was heavily based on expelling imaginary toxins from the body by bleeding their patients or inducing vomiting, sweating, or diarrhea. They performed operations with dirty hands and instruments, spreading lethal infections from one patient to another. Fractured limbs often became gangrenous and had to be amputated, and there was no anesthesia to lessen the pain. Disease was still widely attributed to demons and witches, and many people felt they would be interfering with God's will if they tried to treat it.

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