China's imperial era was a time of discovery and advancement in science, technology, and health care. Gunpowder was invented in Tang times (618–907) by chemical scientists working in the little-known laboratories of Daoist shrines. Increased travel and trade during the Song dynasty (960–1279) led to the improvement of ships and canals. The Song era was also known for its knowledgeable doctors, important medical developments, and its many books about zoology (study of animals) and the use of plants for healing.

When the Mongols took over (1279–1368), they respected Chinese craftsmen and inventors, so science and technology continued to improve. By the Ming dynasty (1368–1644), major improvements had been made in textiles (cotton looms and silk looms with three shuttle winders), publishing (block printing in five colors and better Page 232  |  Top of Articlemetal for movable characters), and food preparation (the refining of white sugar). New farming techniques and equipment increased the variety of crops.

Agricultural science By the sixth century, Chinese farmers had discovered the value of crop rotation, the practice of growing different crops one after another on the same land. This helped to keep the soil fertile and to control weeds and pests. Farmers also used fertilizers, including mud from the Yangzi canals and manure from animals and humans.

Song-dynasty farmers created terraced fields on mountainsides. They also drained lakes and turned them into fields, using earthen walls to keep out the water. Some farmers even created floating fields on bamboo rafts covered with water plants and earth.

Beginning in the Tang dynasty, the Chinese developed better ways to cultivate soil, sow seed, irrigate lands, and grow healthy crops. New tools included harrows, rollers, seed-drill ploughs for planting, and Page 233  |  Top of Articlemould-board ploughs to turn the soil. By the 1200s, Chinese peasants used the rotary winnowing fan extensively. Winnowing is separating the chaff (dry outer skin of the grain) from the grain. A cranked fan blew air over the grain, and the wind carried away the chaff. European farmers did not use this technique until the 1700s.

Botany From the first century BCE, the Chinese studied and illustrated plants. They discovered uses for many of them. Ming scientists looked for plants that could be eaten in times of food shortages. Scholars created encyclopedias listing and describing wild (emergency) food plants.

The greatest botanist Li Shizhen (1518–1593) described and named each plant, and classified them by medical uses. His book contained recipes and cures, including the use of human body parts as medical drugs.

By the Ming period many books about specific plants, including the orange, chrysanthemum, peony, and rose had been published. These plants were common in Chinese gardens and were later introduced into Europe.

Earth sciences In the eleventh century, the Song realized that certain plants grew over specific mineral deposits. They discovered a science known as geobotanical prospecting. This involved locating underground minerals by searching for specific plants that grew on the land on top. By the 1100s, the Chinese used many different minerals, such as alum, ammonium chloride, asbestos, and borax; they also used a variety of valuable stones, such as jade.

The Chinese kept detailed reports of the many earthquakes that occurred there. By 1644, they had recorded 908 shocks, along with the precise dates. They believed earthquakes occurred when qi (gas) escaped from below ground.

Mathematics and astronomy Song mathematicians used patterns of algebra to develop a matrix, or a grid filled by equations. They learned how to successfully solve math problems by working with several different grids at the same time. They also discovered the binomial theorem, which let them work with numbers of higher powers. Other important mathematical ideas that came from this period included square and cube roots, fractions in vertical columns, negative numbers, and coordinate geometry.

Because farming was vital in imperial China, people needed reliable information for planting and harvesting. Astronomers were appointed as government officials. These scholars recorded the oldest continuous series of astronomical observations of any country in the world. The Chinese paid attention to the celestial pole and the celestial equator and created an armillary sphere, an instrument that let them observe the positions of all celestial bodies more easily.

In the 700s, the Chinese had invented mechanical clocks to compare the motions of the heavens. Westerners did not create automatically driven observation instruments until the eighteenth century. By the thirteenth century the Chinese had built large stone instruments to observe solar shadows and make other measurements.

One of the most significant Chinese inventions was the magnetic compass. In the Tang dynasty, compass needles pivoted, providing more Page 235  |  Top of Articleaccurate readings. Scientists discovered that the needle did not accurately show true north-south. The Chinese invented the earliest compasses around the fourth century BCE. About 1040, an iron fish that floated in water was used for land directions. But the Chinese did not use magnetic compasses for navigation on their ships until sometime between 1111 and 1117.

Weapons Centuries after the Chinese identified saltpeter (potassium nitrate), they invented gunpowder, a mixture of saltpeter, charcoal, and sulfur, around 850. Although the Chinese had made fireworks from bamboo as early as 200 BCE, they discovered they could make fireworks with a variety of colors and effects by combining gunpowder with other ingredients.

The Chinese, though, did not use gunpowder for warfare until the tenth century. As they discovered how to create more powerful explosions with saltpeter, they developed weapons, such as bombs, mines, cannons, and guns.

By the 1500s, the Chinese had designed the articulatedjunk ship, which worked well on the Grand Canal. © NORTH WIND PICTURE ARCHIVE/ALAMY © NORTH WIND PICTURE ARCHIVE/ALAMY

Shipbuilding By the Song dynasty, the Chinese had invented the junk, a ship with a flat or slightly curved bottom and planking sides that curved upward. Junks had a square-ended bows (fronts) and stern (backs). This made them strong and watertight.

By the 1500s, the Chinese had designed the articulated junk, a long, narrow barge built from two parts that were loosely connected. These boats could easily sail through shallow, winding channels that were filling with silt. Longer ships needed higher water levels, but the articulated junk worked well on the Grand Canal.

Mechanical clocks In the 700s, the Chinese invented an astronomical clock, six hundred years before an astronomical clock was invented by the Europeans. In 1080, the great scientist Su Song built a huge astronomical clock tower driven by a waterwheel. Scoops on its rim filled with water from a tank. This mechanical clock was developed centuries before one was developed by the Europeans.

The Chinese invented many objects that were useful in everyday life long before they were even imagined by the rest of the world. Chinese inventions served many different purposes, from oil lamps and fireworks, to cast iron and porcelain. The Chinese also invented such mechanical devices as spinning wheels and clocks.

Economic oil lamps and fireworks By the fifth century BCE, the Chinese had invented oil-and-wick lamps. For these lamps, a long, stringlike wick was placed into a cup of full oil, with a piece above the surface. The wick absorbed the oil, and when the wick was lit, a flame burned at the end of the wick and gave off light. However, the lamp had one major problem. The heat from the burning wick caused most of the oil to evaporate before it could be burned.

The Chinese came up with a method by the ninth century to cool the lamp and prevent evaporation. They created the economic lamp, which held cold water below the oil. Normally made of glazed earthenware, the lamp used only half as much oil as the original version.

Another famous Chinese invention gave off light of a different kind. Colored fireworks appeared in China as early as 200 BCE when pieces of bamboo were thrown into fires and exploded in bright colors. After the invention of gunpowder in the ninth century, the Chinese used it to develop many types of fireworks and colored explosions, using a wide variety of materials. To create sparkling effects, they mixed gunpowder with powdered steel dust or shavings of cast iron. Adding minerals, chemicals, and plant products to the gunpowder created flashes of different colors. For instance, fireworks with dye from the indigo plant flashed blues and greens; cinnabar, a mineral, created flashes of red.

Cast iron and porcelain As early as the fourth century BCE, the Chinese used blast furnaces, in which blasts of very hot air heat ore and other materials to high temperatures, to make cast iron. Cast iron is a mixture of iron and carbon that becomes extremely strong when it hardens. In 688, under Empress Wu Zhao (624–705), the Chinese built the largest cast-iron building in the world. This 284-foot (87-meter)-tall pagoda (a temple with many tiers, or levels) was three stories high with a large gold-plated figure of a phoenix, the mythical bird of fire, on top.

In 954, an emperor in the Later Zhou Dynasty (951–960) ordered the creation of a memorial in honor of one of his great military victories. This Great Lion of Zangzhou was 20 feet (6 meters) high and 16 feet (5 meters) long. The hollow statue weighed 40 tons (36 tonnes). The lion was the largest single cast-iron object ever constructed at that time.

Another material that the Chinese made was porcelain. Porcelain is a hard, white ceramic that is made by firing (heating) pure clay at high temperatures and glazing it with colors. The Chinese invented porcelain as early as the third century. By the tenth century, making porcelain was an art, and the porcelain trade was growing.

To meet the demand for Chinese porcelain, hundreds of thousands of people worked in the industry. Some workers cleaned the clay; others glazed the pieces or fired them. Kilns, which are the large covered ovens in which the pieces were fired, were usually built on the slope of a hill. Large kilns could handle 25,000 pieces of porcelain in a single firing.

Special techniques and firing conditions were used to create colors and effects. Ming artists popularized a type of white porcelain with beautiful blue designs and images. The blue color was created by the addition of cobalt, a type of metal. In the fifteenth century, blue-and-white porcelain from China was prized by European kings and queens. Europeans did not produce their own porcelain until three hundred years later.

Mechanical devices The spinning wheel, a device that twists and stretches plant or animal fibers into yarn or thread, originated in China. A person using a spinning wheel pumps a foot pedal that makes a large wheel turn. Fibers connected to the turning wheel are pulled and stretched, becoming thread or yarn. The Chinese began using fabrics made from the fibers produced by silk worms as they made their cocoons as early as the fourth millennium BCE. The Chinese processed silk and other fibers into thread by hand and with simple tools for many Page 238  |  Top of Articlecenturies. During the imperial period, trade increased the demand for silk, and producers wanted an easier, faster way to turn silk fibers into thread. As a result of this need, the first spinning wheels were invented around 1035 CE.

Pictured is a scale model of a Chinese astronomical clock. The Chinese were the first to create a clock. © SCIENCE & SOCIETY PICTURE LIBRARY/GETTY IMAGES © SCIENCE & SOCIETY PICTURE LIBRARY/GETTY IMAGES

Another mechanical device created by the Chinese was the clock. The Chinese created many designs for clocks. The Buddhist monk and mathematician Yixing (c. 683–727) created the world's first mechanical water clock. Completed in 725, the clock included a wheel that was moved by the flow of water in order to measure time. The water in Page 239  |  Top of ArticleYixing's clock could freeze in the cold temperatures, however, so torches were lit nearby to keep it warm.

Because mercury, a type of liqud metal, does not freeze, the tenthcentury astronomer Zhang Sixun used it to power a similar clock in 976. In time, hundreds of thousands of these clocks were in use throughout the empire.

In 1090, the inventor Su Song (1020–1101) decided to build a clock that would show astronomical information, such as the phases of the moon. His clock used water to power a wheel that served as a gear to move a series of chains that operated the clock. He named his invention the “celestial ladder.” Later, he illustrated this chain drive in his book, New Design for an Astronomical Clock. The Europeans did not make a real chain drive until 1770.

Su Song then built the largest astronomical clock in the world in 1092. The clock tower rose more than 30 feet (9 meters) high. A large bronze sphere on top of the sphere showed the location of the stars in the sky according to the time kept by the clock, and it was moved by a similar water-powered chain drive as his earlier clock. It also used chimes and moving figures to show the time of day. Europeans did not develop a similar clock until the fourteenth century.

The invention of gunpowder allowed the Chinese to create a variety of weapons used to fire projectiles such as bullets or cannonballs at an enemy. The barrel gun and cannon, which both used gunpowder, were perfected by the Chinese in the late 1100s. China also was the first to develop other weapons of war, including flamethrowers, thunderclap bombs, land mines, and rockets.

Gunpowder Chinese scientists discovered and developed the necessary ingredients—saltpeter or potassium nitrate, sulfur, and charcoal—to make gunpowder. By the mid-600s, Chinese scientists discovered that combining sulfur and saltpeter created small explosions, but the mixture was not flammable. In the early 800s, chemists added dried birthwort herb to the mix, which had enough carbon to make the mixture burst into flames, but it did not actually explode. By 850, they had created a gunpowder by adding more saltpeter to their mixtures.

The more saltpeter in the gunpowder, the more explosive it becomes. In the eleventh century, Chinese gunpowder had about 50 percent saltpeter, but 75 percent saltpeter is needed for big explosions. As higher proportions of saltpeter were added in the following centuries, the Chinese produced bombs, grenades, and land mines.

The Song emperor recognized the potential of these chemicals to create weapons, so he prohibited the sale of sulfur or saltpeter to foreigners in 1067 and would not allow private companies to produce both ingredients. In this way, the government controlled all access to gunpowder.

Weapons with firepower The Chinese invented the first continuous flamethrowers. A flamethrower is a device that shoots out a stream of fire. In 904, the Chinese developed a weapon that used a pump to move a flammable liquid past a gunpowder fuse to light it on fire, creating a sheet of steady flames and spraying victims with burning liquid.

In the tenth century, Chinese inventors created fire arrows. They tipped arrows with little gunpowder bundles inside folded papers sealed with wax. They added gunpowder fuses so when the arrows hit, they set fire to their targets. Soldiers shot at enemy tents, wagons, clothing, weapons, and stores of hay or food. In 1083, the Song army had a supply of 250,000 gunpowder-tipped arrows.

Bombs As gunpowder developed, so did explosive bombs. Bombs create large, destructive explosions. By the late 1000s, scientists had created the thunderclap bomb. For these bombs, gunpowder was enclosed in light bamboo or paper and thrown from trebuchets, or catapults. Before these bombs were thrown, soldiers either lit a fuse or ignited the bomb with a red hot metal poker. Thunderclap bombs started fires and terrified the enemy's horses with explosive sounds. The noise also frightened many enemy soldiers.

Thunderclap bombs could also be used as grenades thrown by hand. Soldiers or hunters most likely put a grenade in a narrow pottery container, lit the fuse, and tossed it. When the pottery shattered, the bomb exploded and a fire was ignited.

By 1221, the thundercrash bomb was invented. More deadly than earlier bombs, thundercrash bombs had hard casings of iron rather than Page 241  |  Top of Articlesoft paper or bamboo. The shrapnel, or metal fragments thrown off when the bomb exploded, killed and wounded large numbers of enemy fighters.

Gunpowder had other uses in warfare as well. In 1276, the Chinese used soft-shelled bombs timed to explode in midair, possibly colored like fireworks. They fired these flares to send messages to distant troops when they were attacked.

Tear gas and poison bombs By the 1200s, Chinese scientists had developed many other types of bombs. These included poison bombs, gaseous bombs, and feces-filled bombs. These bombs gave the Chinese additional ways to attack and destroy enemy warriors. For example, powdered lime, a poisonous chemical, was added to bombs to create a type of tear gas. When the bomb exploded, the smoke and lime mixture made soldiers' eyes water. Similar bombs filled with lime and sulfur, another chemical, were used in sea battles. When the bombs hit the water, the sulfur burst into flames. The paper case containing lime then burned away, spreading smoke that blinded enemy sailors.

Another type of tear-gas bomb was filled with charcoal and a combination of arsenic, sawdust, resin, and human hair, as well as chicken, wolf, and human excrement. Smoke from burning wolf excrement, which looked red both in the daytime and at night, could also be used for sending warning signals.

Mines By 1277, the Chinese had developed land mines, which are explosive devices that are buried underground. These mines had triggers and fuses that sparked an explosion when enemy soliders were nearby. One type of Chinese land mine had eight small guns pointing in different directions, all set off by an automatic trigger. In 1360, these triggers were made of flint and steel, which created a spark when struck together. This invention was later used in Europe in 1547 for flintlock muskets, a type of gun.

The Chinese also developed sea mines, called “submarine dragon-kings.” Made of wrought iron, sea mines drifted in water on a wooden board. The mine was placed inside an ox bladder to keep it from getting wet. A thin stick, which was kept dry inside a goat's intestine, served as a fuse. Surrounded by goose and wild-duck feathers, the burning fuse floated above the water. When the joss stick burned down, the bomb ignited and caused a great explosion.

Rockets By 1150, Chinese inventors developed rockets. Rockets are devices that fly long distances through the air powered by an explosion. Page 243  |  Top of ArticleThe idea came from a Chinese firework known as the “ground rat” or “earth rat,” which sped along the ground spurting flames behind it. Another firework, called the “water rat,” skidded across lakes on floats or little skis. The Chinese added fins and wings to rockets soon after 1300. These rockets were attached to arrows, allowing them to fly great distances.

Sometimes soldiers clustered rocket arrows together inside a long, narrow basket and lit all the fuses at once. These devices sent many arrows into enemy territory at the same time. Chinese armies also used wheelbarrows as portable launchers. By lining up rows of wooden launchers in a wheelbarrow, they could shoot hundreds of rocket arrows at once. A Ming super-launcher supposedly could launch 32,000 rockets at once; approximately one million rocket arrows might be used during a battle.

By the early 1300s, the Chinese had developed multistage rockets. These rockets had two sections; the second part fired after the first one ran out of power. When the gunpowder in the first rocket tube was almost gone, the rocket still flew because the second fuse lit automatically. Using this technology, some rockets had a range of 1 mile (1.6 kilometers).

Guns By 905, the Chinese had developed a weapon called a fire-lance, which is sometimes considered the world's oldest gun. The fire-lance was a firework attached to a spear. Later fire-lances had metal barrels, or tubes through which small objects like rocks could be fired. Even after the invention of guns, fire-lances remained popular and were used until the mid-1900s as protection against pirates.

The handgun was developed in the thirteenth century. These weapons used an explosion caused when gunpowder was lit to force a bullet-like object forward through a tube, or barrel. A bronze handgun made in 1288 was excavated in Manchuria. It was more than 1 foot (0.3 meters) long and weighed about 8 pounds (3.6 kilograms). Its fat, round shape prevented it from exploding along with the gunpowder.

Cannons Cannons are much larger and heavier than guns, but they are used in a similar way. Gunpowder is sparked to cause an explosion and shoot an object forward through a long barrel. Early Chinese cannons were made of brass. By the Yuan dynasty, cannons were made of iron, Page 244  |  Top of Articlewhich made them very heavy. As a result, they were usually moved around on a wheeled cart. The Chinese also developed rapid-fire cannons by joining the back ends of two cannons into one long barrel. They placed the cannons on a cart; after one cannon was fired, the cart was quickly rotated to shoot the second cannon.

Another type of cannon was the cartwheel gun. It had thirty-six barrels coming out from the center like spokes of a wheel. These guns were so small that a single mule could carry two, one on each side of its pack. In the following centuries, though, handheld guns became more popular.

From ancient times, Chinese scientists studied the world around them. They created many new branches of science. They observed much about the natural world and performed many experiments long before many cultures in other parts of the world. Some of the ideas they came up with and techniques they developed are still used in modern times.

Earth science In 1086, the scientist Shen Kuo (1031–1095) published Dream of Pool Essay. This book contained information about many different areas of science, including geology, the study of the makeup of the earth. Shen explained how mountains erode (wear away) over time and described deposits of sediment, which are made from soil and rocks carried by flowing water. Although he was not the first person to come up with these ideas, his explanations were thorough and clear. He also discussed fossils and changes to the climate.

The Chinese discovered a branch of science known as geobotanical prospecting. This science linked the types of plants growing in certain areas to minerals found underground in those spots. In the early 500s, three guidebooks listed different plants and their related mineral deposits.

In 1062, Su Song published a medical book titled Illustrated Pharmacopoeia. He wrote that the purslane plant contained mercury and explained how to extract it. In 1421, a book called The Precious Secrets of the Realm of the King of Xin claimed that gold could be found in the rape turnip; silver in a type of weeping willow; lead and tin in chestnut, barley, and wheat; and copper in Indian sorrel. In contrast, Europeans Page 245  |  Top of Articledid not understand geobotanical concepts such as these until the seventeenth century.

Natural luminescence By the third century, the Chinese had become interested in studying natural objects or living creatures that give off their own light. This phenomenon is called natural luminescence. In 1596, naturalist Li Shizhen (1518–1593) correctly identified glowworms, fireflies and other glowing insects, as well as mayflies or midges that gave off their own light.

The Chinese called luminescence “yin fire,” and they collected naturally luminescent pearls and glowing minerals. They used their knowledge to make phosphorescent (glowing) paints by the eleventh century.

Astronomy The Chinese had been studying the sky for thousands of years before the imperial era, when several advancements in astronomy were made. For instance, Chinese mapmakers created the first known star map, which was discovered in a cave. Some scholars believe it was made in the mid-600s, during the Tang dynasty. This map, known as the Dunhuang Star Atlas, was discovered in a cave in western China around 1900. It divides the sky into 13 regions, one for each month of the year and another showing the stars around the North Pole. In each panel, it shows the positions of the stars as seen from Earth.

In 1596 Li Shizhen correctly identified glowworms as one of the insects that contained bacteria that emitted a natural luminescence, or light. © BLICKWINKEL/ALAMY © BLICKWINKEL/ALAMY

The Chinese used other methods of tracking the positions of stars and other celestial objects. Astronomers built observatories, large structures from which they watched the sky, often using special instruments. Guo Shoujing (1231–1316) was one scientist who developed devices for astronomers to use. One of these was the gnomon, which was a tall, thin rod planted in the ground. The length and location of the rod's shadow at noon each day provided information used to track the position of the sun and the length of a year.

Mapmaking The Chinese also accurately mapped the land around them. For some maps, this accuracy was enabled by the use of grids. One example is the Map of the Paths of Yu the Great, which was created in the twelfth century. It is overlaid with a grid, and each side of a square represents a distance of 100 li (about 33 miles, or 53 kilometers). The map contains details of China's eastern coastline and includes the Shandong Peninsula, which juts into the Yellow Sea. Carved in stone, this map is remarkably similar to twentyfirst-century maps of China's coast.

In 1320, the Daoist monk and geographer Zhu Siben (1273–c. 1335) published an atlas called the Yutu that also used grids. These networks of squares showed the accurate geography of China. The map was seven feet long, though, and hard to unroll. The grid system made Page 247  |  Top of Articleit easy to create smaller copies of the map, however, because the grid was easily resized. Other later Chinese maps and atlases also used such grids.

The Chinese had developed and used several different mathematical ideas and processes, including those that supported the creation of calendars and the study of astronomy, in the centuries before the imperial era. In the third century, the mathematics textbook Nine Chapters on the Arithmetical Skills was compiled by mathematician Liu Hui. Several generations of scholars who lived between the tenth and the second century BCE developed the information that was included in the book. The book included problem on such mathematical ideas as calculating area and volume, fractions, finding square roots and cube roots, right angles, and negative and positive numbers. It served as the basis for mathematical education for centuries, including during the imperial era.

The growth of trade, industry, construction, and the military during the imperial era resulted in advancements in mathematics. The Song and Yuan dynasties are known for great achievements in the field. Several mathematicians, including Shao Yong (c. 1011–1077), Qin Jiushao (c. 1202–1261), and Li Zhi (1527–1602), made strides in the development of algebra, geometry, trigonometry, and high-level calculations.

Suan chou and zero For centuries, the Chinese used a system called suan chou, or counting rods, to do math calculations. This system used small rods made of bamboo or wood arranged vertically or horizontally to indicate certain numbers and place values. By the Ming dynasty, however, the abacus had mostly replaced counting rods. With an abacus, beads are threaded on several rods enclosed in a frame. Both simple and complex calcuations can be made by sliding the beads along the rods into different positions.

Another mathematical idea adopted during the imperial period was the zero. The Chinese were not the first to use the zero, but they left a blank space for zero. For example, they wrote number 302 as 3 [blank] 2, or three hundreds, no tens, two units. The blank space worked because the Chinese solved problems without signs and calculations.

Some scholars think that Chinese mathematicians started drawing a circle around the blank space. Eventually, this circle was likely written in Page 248  |  Top of Articleplace of the blank space to signify zero. By 1247, zeroes appeared in Chinese books.

Imperial Chinese medicine diagnosed diseases and offered therapies for most health problems as well as for psychological problems. Chinese medicine, however, did not excel in surgery. Both rich and poor people had access to health care during imperial times, but only men from the upper classes were allowed to become doctors. State doctors visited the poor in their homes or in hospitals to treat injuries and disease.

Although some Chinese doctors made many practical advances in medicine, many traditional beliefs were also part of diagnosis and treatment. Chinese philosophy taught that yin and yang must be balanced to maintain harmony in many aspects of life, including health. The idea of yin included darkness, cold, wetness, and rest, while yang included light, heat, dryness, and activity. An excess of one or the other in the human body was thought to cause disease, and treatment was meant to restore that balance.

Chinese medicine spread to other regions during the imperial era. Over the centuries, doctors in Korea, Japan, India, and Persia, as well as bordering regions such as Tibet and Mongolia, all adopted many of the practices of Chinese physicians.

Medical training and practice The need to ensure doctors were properly trained to treat patients was recognized in the imperial era. China's Grand Medical Office, founded in 624, is one of the earliest known models of state-supervised medical teaching. Later, the Song government set up formal testing and grading of doctors, medical schools, hospitals, and pharmacies. Yuan leaders founded the Imperial Academy of Medicine in 1305 to oversee medical schools and standardize the subjects students were taught.

In addition to physicians, other specialists provided treatments and healing during the imperial era. These included acupuncturists (healers who insert thin needles through the skin at special points), masseurs (people who give massages), and exorcists (those who cast out evil spirits). Some religious scholars served as healers. Women healers included nuns or elderly women who made medicines or acted as midwives (women who help mothers during childbirth). However, these women were not well respected. Some stories from the era portray them as gossips and criminals.

A historical illustration from the Ming dynasty shows acupuncture points. Medical specialists, such as acupuncturistsfirst appeared in imperial China during the Tang dynasty. © ACUPUNCTURE POINTS ON THE BODY, MING DYNASTYWOODCUT/PRIVATE COLLECTION/J. T. VINTAGE/BRIDGEMAN IMAGES © ACUPUNCTURE POINTS ON THE BODY, MING DYNASTYWOODCUT/PRIVATE COLLECTION/J. T. VINTAGE/BRIDGEMAN IMAGES

Knowledge of diseases Chinese doctors developed their knowledge of disease during the imperial period. For example, they were the first to realize that diabetics had too much sugar in their urine, beginning in the 600s. Physician Sun Simiao (581–682) advised diabetics to give up wine and stop eating cereals and salted food. (Even in the twenty-first century, diabetics are advised to avoid alcohol and certain foods.) By 1189, the physician Chang Kao had identified the dangers to diabetics of even small cuts or abrasions, which can be slow to heal.

By the 600s, Chinese physicians discovered that goiters, which are large lumps in the neck caused by swelling of the thyroid gland, could be healed. The physician Chen Quan (died 643) used the thyroid glands of sheep to treat goiters in people. He first washed one hundred thyroid glands in lukewarm water, removed the fat, and then cut them into pieces. He mixed them with jujube dates and ground the entire mixture into pills. As an alternative, the patient could eat one thyroid gland immediately following its removal from the sheep.

Wang Xi used the thyroid glands of different animals, including pigs, to treat goiters. He air-dried the glands into powder, and patients mixed the powder into cold wine and swallowed some every night. Each prescription required the thyroid glands of fifty pigs. Other doctors recommended that patients use the thyroid glands of water buffalo instead.

Chinese doctors also identified beriberi, an illness caused by a deficiency of vitamin B1. In the late 700s, writer Han Yu (768–824) noted that the disease was more common in the south than in the north. He noticed that southern people ate rice, whereas northerners ate wheat and millet, now known to contain a high content of vitamin Bl. Hu Sihui (1314–1330) wrote about two kinds of beriberi, the wet and the dry, and suggested diets rich in Bl and other vitamins as a prevention.

Treatment for other diseases developed in imperial times as well. Qian Yi (1032–1113), an eleventh-century pediatrician, was among the first to identify smallpox, as well as chicken pox, measles, and scarlet fever. In the late 1500s, doctors began using variolation, or inoculation, for smallpox. Doctors usually took pox material from scabs of a person who had been inoculated. They put this pox material on a piece of cotton and inserted it into the patient's nose. The pox went through the mucous membrane of the nose and moved quickly into the bloodstream. The blood developed antibodies, or substances to fight off disease.

Activity 1: Chinese medical dictionary Chinese doctors and healers had a range of information about illnesses and how to treat their patients. Considering what they knew during the imperial era, create a Chinese medical dictionary. Research herbs, medicines, and other treatments used by imperial Chinese doctors and other healers. Write prescriptions on the page along with the expected cures. Illustrate the dictionary with images of the treatments you find.

Activity 2: Chinese time traveler You are a Chinese peasant transported in time from the early Tang to the Ming dynasty. What changes shock you the most? Sketch one invention created since your time and write a description of this object to take back with you upon your return to your own time. Be sure to explain how it is used so people who have never before seen this invention can understand its operation.