Medical discoveries have transformed the world. They have changed the course of history, saving countless lives, pushing the boundaries of our knowledge to where we stand today, ready for great new discoveries.

Human Anatomy
In ancient Greece, the treatment of disease was based more on philosophy than on a true understanding of human anatomy. Surgery was rare, and dissection of cadavers was not yet practiced. As a result, physicians had little or no knowledge of the internal structure of the human being. It was not until the Renaissance that anatomy emerged as a science.

The Belgian physician Andreas Vesalius shocked many when he decided to study anatomy by dissecting corpses. Material for research had to be obtained under the cover of night. Scientists like Vesalius had to resort to methods that were not entirely legal. When Vesalius became a professor at Padua, he struck up a friendship with an executioner. Vesalius decided to pass on the experience he had gained from his years of skillful autopsies by writing a book on human anatomy. Thus the book “On the Structure of the Human Body” appeared. Published in 1538, it is considered one of the greatest medical works, as well as one of the greatest discoveries, because it is the first accurate description of the structure of the human body. It was the first serious challenge to the authority of the ancient Greek physicians. The book sold out in huge numbers. Educated people, even those far from medicine, bought it. The entire text was meticulously illustrated. Thus, information about human anatomy became much more accessible. Thanks to Vesalius, the study of human anatomy by autopsy became an integral part of doctors’ training. And that brings us to the next great discovery.

Circulation
The human heart is a muscle the size of a fist. It contracts more than a hundred thousand times a day, over seventy years – that’s more than two billion heartbeats. The heart pumps 23 liters of blood per minute. Blood flows through the body, passing through an intricate system of arteries and veins. If all the blood vessels in the human body were drawn in a single line, you would get 96,000 kilometers, which is more than twice the circumference of the Earth. Until the beginning of the 17th century, the circulatory process was misrepresented.

The prevailing theory was that blood flowed to the heart through pores in the soft tissues of the body. Among the adherents of this theory was the English physician William Garvey. The work of the heart fascinated him, but the more he observed the heart beating in animals, the more he realized that the generally accepted theory of circulation was simply wrong. He writes unequivocally, “…I wondered if the blood could not move as if in a circle?” And the first sentence in the next paragraph: “I subsequently found out that it was…”. While performing autopsies, Garvey discovered that the heart had unidirectional valves that allowed blood to flow in only one direction. Some valves let blood in, others let it out. And that was a great discovery. Garvey realized that the heart pumps blood into the arteries, then it goes through the veins and, closing the circle, returns to the heart to then start the cycle all over again. Today this seems like commonplace truth, but for the 17th century, William Garvey’s discovery was revolutionary. It was a devastating blow to established medical beliefs. At the end of his treatise, Garvey writes: “At the thought of the innumerable consequences which this will have for medicine, I see a field of almost limitless possibilities.

Harvey’s discovery seriously advanced anatomy and surgery, and simply saved many lives. Around the world, surgical clips are used in operating rooms to block blood flow and keep the patient’s circulatory system intact. And each one is a reminder of William Garvey’s great discovery.

Blood Groups
Another great blood-related discovery was made in Vienna in 1900. All of Europe was overwhelmed with enthusiasm for blood transfusions. First came the claims that the therapeutic effect was astounding, and then, a few months later, reports of deaths. Why were transfusions sometimes successful and sometimes not? Austrian physician Karl Landsteiner was determined to find the answer. He mixed blood samples from different donors and studied the results.

In some cases the blood mixed successfully, but in others it curdled and became viscous. On closer inspection, Landsteiner discovered that the blood clotted when specific proteins in the recipient’s blood, called antibodies, reacted with other proteins in the donor’s red blood cells – antigens. For Landsteiner, this was a turning point. He realized that not all human blood is the same. It turned out that blood could be clearly divided into 4 groups, to which he gave the designations: A, B, AB and null. It turned out that blood transfusions were only successful if a person received a transfusion of blood of the same group. Landsteiner’s discovery was immediately reflected in medical practice. A few years later, blood transfusions were performed all over the world, saving many lives.

Vaccination
The next of the great discoveries was made in the 18th century, when smallpox killed about 40 million people worldwide. Doctors could find no cause for the disease, nor a cure for it. But in an English village, talk that some locals were immune to smallpox caught the attention of a local doctor named Edward Jenner.

Rumor had it that dairy farm workers were immune to smallpox because they had already had cowpox, a related but milder disease that affected cattle. Smallpox patients had fever and ulcers on their hands. Jenner studied this phenomenon and wondered if the pus from these ulcers was somehow protecting the body from smallpox. On May 14, 1796, during a smallpox outbreak, he decided to test his theory. Jenner took fluid from a pockmark on the hand of a milkmaid who had cowpox. Then, he visited another family; there he injected a healthy eight-year-old boy with the cowpox virus. In the following days, the boy had a slight fever and several smallpox blisters appeared. He then recovered. Six weeks later, Jenner returned. This time he inoculated the boy with smallpox and waited to see whether the experiment would win or fail.

Vitamins
The next discovery came from the labors of scientists who for many years had independently struggled with the same problem.
Throughout history, scurvy was a serious disease that caused skin lesions and bleeding among sailors. Finally, in 1747, the Scottish ship surgeon James Lynde found a cure. He discovered that scurvy could be prevented by including citrus fruits in the sailors’ diet.

Another common disease among sailors was beri-beri, a disease affecting the nerves, heart and digestive tract. In the late 19th century, the Dutch physician Christian Eijkman determined that the disease was caused by eating white ground rice instead of brown unpolished rice.

Although both of these discoveries linked disease to diet and nutritional deficiencies, it was only English biochemist Frederick Hopkins who was able to figure out what that connection was. He suggested that the body needs substances that are found only in certain foods. To prove his hypothesis, Hopkins conducted a series of experiments. He gave mice artificial food that consisted exclusively of pure proteins, fats, carbohydrates and salts. The mice became weak and stopped growing. But after a little milk, the mice got well again. Hopkins discovered what he called an “essential nutritional factor,” which was later called vitamins.

Penicillin
After World War I, which claimed more than 10 million lives, the search for safe methods to repel bacterial aggression intensified. After all, many died not on the battlefields, but from infected wounds. The Scottish physician Alexander Fleming was also involved in the research. While studying Staphylococcus aureus bacteria, Fleming noticed something unusual growing in the center of a laboratory bowl – mold. He saw that the bacteria had died around the mold. This led him to speculate that it was secreting a substance that was destructive to bacteria. This substance he called penicillin. For the next few years Fleming tried to isolate penicillin and apply it to the treatment of infections, but he failed and finally gave up. However, the results of his labors proved invaluable.

In 1935, Oxford University researchers Howard Florey and Ernest Cheyne stumbled upon a report of Fleming’s curious but unfinished experiments and decided to try their luck. These scientists managed to isolate penicillin in its pure form. And in 1940, they tested it. Eight mice were injected with a lethal dose of streptococcus bacteria. Then, four of them were injected with penicillin. A few hours later, the results were in evidence. All four of the mice who had not received penicillin died, but three of the four who had received it survived.