1. Blood theories

In the 17th century, physicians had already seen bacteria and red blood cells, though they were ignorant of their importance. However, the more prominent new invention was the syringe. In 1667, the syringe was used experimentally with mixed results. With a quill, humans were given transfusions of sheep’s blood (because Jesus was the Lamb of God, you know).

Surprisingly, it worked. But, only once. Why? Allergic reactions often don’t occur the first time, but the second time you are exposed to a foreign matter your immune system will react in defense. This stumped physicians. Sometimes it worked, sometimes it didn’t.

Physicians of the period had little knowledge of how blood actually worked. In 1628, William Harvey had at least observed that blood flowed two ways from the heart and lungs. Before that, the most commonly held belief was that red blood carried some sort of air energy and that blue blood in the veins distributed food from the liver.

Ya, food from the liver. Through clinical experimentation on animals, Harvey determined that there was only one supply of blood that’s pumped by the heart through the veins and that oxygenation by the lungs turns blood red.

2. Book smart, not street smart

Physicians were book-learned, not clinically skilled. Surgery was thought to be beneath them, comparable to a barber or butcher. In fact, one of the premier surgeons of the time, Ambroise Paré, was once a barber’s apprentice before becoming a surgeon to the king of France.

But that’s okay because you wouldn’t want a doctor to operate on you then anyway. Doctors of the 17th century were still studying Galen’s anatomy notes from 1100 years ago. And his observations were based on monkeys.

However, one of the surgeries that was most performed was the removal of kidney stones. The doctor would squeeze the stones to the surface of the skin and make a small incision to remove it.

Smart, you’re thinking. But this was without anesthesia and most patients died or at least suffered incontinence because that incision was usually done through the perineum. Don’t worry, an experienced physician could do it 54 seconds, because any slower and the patient could die.

3. Tools Of The Trade

If they didn’t use knives or other medical instruments, what did they use? Leeches. And maggots. And cobwebs. I’m not joking. They used leeches to purge the body of “excess blood” that caused apoplexy and fevers (doesn't work, by the way).

And maggots were used to clean dead flesh from a wound (still in use today and does work). And the cobwebs were stuffed up nosebleeds and were packed into wounds (can we say, unsanitary). They also thought swallowing a spider would cure a fever (or kill you, depending on the spider).

Got a gunshot wound from war? Prepare yourself to have it cauterized with boiling hot oil. Which was more likely to kill you than the initial gunshot. A lot of a physician’s practical knowledge came from superstition and dogma. And maybe a bit of luck and the human body’s will to persevere.

4. Hospitals (Death’s Door)

Hospitals grew out of the church. The church cared for the poor and the sick. Infirmaries were created were nuns cared for the dying. However, many didn’t go to a hospital to get well; they had a 25% death rate. They went there to get their last rites. In fact, many hospitals had only one or two visiting physicians.

Why so many sick people: the Bubonic Plague. The majority of patients in hospitals were plague victims. In 1628-1631, France alone lost 1 million people. It’s no surprise that Louis the 14th, the Sun King of France, ordered a hospital in every major city.

But it wasn’t until late in the 17th century that Sir William Petty said, “Hey, maybe we should train physicians in hospitals, and maybe we should be doing research while we’re treating patients, and maybe we should separate the plague victims and have a separate maternity ward.” But his ideas were too advanced for the time. These suggestions wouldn’t be implemented until late 19th century.

5. Bogus methodology

In the 17th century, physicians still didn’t know that germs spread diseases and that germs thrived in unhygienic conditions. For example, they thought malaria came from a poisonous gas called ‘miasma’ emanating from sewers and cesspits. Everyone in New York City today would have malaria.

So, they followed Galen, the 1100 years-ago monkey butcher, and his idea that the body was ruled by four fluids or humors: blood, phlegm, yellow bile, and black bile. And physicians used a host of magical powders from dubious sources to balance them. Think: horn of unicorn, bezoar stone (dried tear of a stag), fox lung, and skulls of executed criminals.

Where did they get these erroneous concoctions? The Silk Road. Chinese herbal medicine had filtered to Europe and European physicians had a field day with it. Chinese medicine worked in China because it was rooted in 4500 years of trial and error and passed along through generations via a caste system. They didn’t just sprinkle unicorn dust everywhere and proclaim people healed