In 1543, Andreas Vesalius (vuh SAY lee us) published On the Structure of the Human Body, the first accurate and detailed study of human anatomy. Vesalius's careful and clear drawings corrected errors inherited from ancient classical authorities.

About the same time, French physician Ambroise Paré (pa RAY) made many practical advances. He developed a new, more effective ointment for preventing infection and better ways to seal wounds during surgery. He introduced the use of artificial limbs and invented several scientific instruments.

In the early 1600s, William Harvey, an English scholar, described the circulation of the blood for the first time. He showed how the heart serves as a pump to force blood through veins and arteries. Pioneering scientists like Harvey opened the way for further advances.

Illustration of a man standing on front of seated group, pointing to a skeleton next to a large open book. Group is seated around a cadaver lying on a table, whose torso has been cut open to expose organs.

English surgeon John Banister dissects a corpse to teach students about human anatomy. New approaches to scientific investigation helped to change how physicians learned about the human body.

The Microscope

Later in the 1600s, the Dutch inventor Anton van Leeuwenhoek (LAY wun hohk) perfected the single-lens microscope. Van Leeuwenhoek worked on grinding lenses as a hobby. He used them to examine tiny objects such as lice or the mouths of bees.

Peering through his microscope at drops of water, he was surprised to see tiny organisms, which he called “very little animalcules.” Van Leeuwenhoek thus became the first human to see cells and microorganisms such as bacteria. For this work, he is often called the founder of microbiology. Over time, the microscope would lead to still more startling discoveries.

The New Science of Chemistry

The branch of science today called chemistry was known as alchemy in medieval times. Alchemists believed that one substance could be transformed into another substance and tried to turn ordinary metals into gold. During the Scientific Revolution, chemistry slowly freed itself from the magical notions of alchemy. Still, scientists benefited from some of the alchemists' practical knowledge, such as the manipulation of metals and acids.

In the 1600s, English chemist Robert Boyle explained that all matter was composed of tiny particles that behave in knowable ways. Boyle distinguished between individual elements and chemical compounds and explained the effect of temperature and pressure on gases. Boyle's work opened the way to modern chemical analysis of the composition of matter.

Sketch of two arms labeled figures 3 and 4 with tourniquets tied above each elbow, blood vessels marked with letters, and fingers pointing to each.

An illustration of the circulatory system from William Harvey's book, On the Motions of the Heart and Blood. Harvey revolutionized medicine by suggesting that blood circulates continuously throughout the body.

Isaac Newton Links the Sciences

As a student at Cambridge University in England, Isaac Newton devoured the works of the leading scientists of his day. By age 24, he had formed a brilliant theory to explain why the planets moved as they did. According to one story, Newton saw an apple fall from a tree. He wondered whether the force that pulled that apple to Earth also controlled the movements of the planets.

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Table of Contents

World History Topic 1 Origins of Civilization (Prehistory–300 B.C.) Topic 2 The Ancient Middle East and Egypt (3200 B.C.–500 B.C.) Topic 3 Ancient India and China (2600 B.C.–A.D. 550) Topic 4 The Americas (Prehistory–A.D. 1570) Topic 5 Ancient Greece (1750 B.C.–133 B.C.) Topic 6 Ancient Rome and the Origins of Christianity (509 B.C.-A.D. 476) Topic 7 Medieval Christian Europe (330–1450) Topic 8 The Muslim World and Africa (730 B.C.-A.D. 1500) Topic 9 Civilizations of Asia (500–1650) Topic 10 The Renaissance and Reformation (1300–1650) Topic 11 New Global Connections (1415–1796) Topic 12 Absolutism and Revolution Topic 13 The Industrial Revolution Topic 14 Nationalism and the Spread of Democracy (1790–1914) Topic 15 The Age of Imperialism (1800–1914) Topic 16 World War I and the Russian Revolution (1914–1924) Topic 17 The World Between the Wars (1910–1939) Topic 18 World War II (1930–1945) Topic 19 The Cold War Era (1945–1991) Topic 20 New Nations Emerge (1945–Present) Topic 21 The World Today (1980-Present) United States Constitution Primary Sources 21st Century Skills Atlas Glossary Index Acknowledgments