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Once Enzo had left for work, Lorenzo called Hedy over to ask what they should do next.
The young woman tapped her chin thoughtfully and then suddenly asked if Da Vinci had returned yet.
The lord raised an eyebrow and replied calmly, "He’s already gone to the public baths to wash."
The method Hedy had in mind, though clumsy and tedious, was effective enough. She had taken basic biology courses and often chatted with her private doctor, so she was familiar with serum and red blood cells.
"Lord, if possible... I would like to request blood from six different convicted criminals."
This era already had syringes, and doctors had attempted to forcefully extract cataracts from eyeballs.
When blood is left to stand in a test tube, it gradually coagulates and separates into layers.
The top layer is a pale, clear liquid, either white or light yellow, known as serum. Below it, the clot of blood contains many red blood cells.
Da Vinci helped her label each test tube and wrote tags indicating the different condemned criminals’ identities. They found several clean small dishes and began their comparative experiments.
When red blood cells were dropped into serum, some of them dispersed like diluted paint, creating a uniform light red color. Others, however, formed clear clumps, almost as if they were resisting the serum in some way.
Before Hedy could figure out the next step in the experiment, Da Vinci suddenly gasped and began quickly sketching something.
“You... figured it out?” she hesitantly asked, watching him draw two symbols, and she began to doubt who was from the modern world.
“This is already very obvious!” Da Vinci quickly recorded the effects of different liquid interactions, sketching a six-by-five grid to record the thirty different outcomes.
Hedy hadn’t fully grasped what he was calculating yet, so she tentatively asked, “How many blood types do you think there are?”
“Four—” Da Vinci replied, as if he were a student handing in a completed exam. He handed her the paper, saying, “How did you think of this experiment? It's so direct!”
Hedy looked at the Latin characters on the paper, then glanced at the six test tubes. She asked, “What do you see?”
“This tube is the most interesting—no matter which blood it’s mixed with, it doesn’t form any clumps,” Da Vinci began furiously taking notes, likely preparing to ride his horse straight to the Florence Academy for a debate: “It’s like a mother—so accepting, it doesn’t reject any other blood.”
“These two tubes of blood are completely incompatible. They’re like brothers who have grown apart—no matter what, they refuse to mix together.”
Hmm… you really are talented.
Hedy finally caught up with his train of thought, and together they began recording each specific reaction. She guided Da Vinci to use Greek letters to name the four blood types.
For a brief moment, she felt as if she had truly returned to the Renaissance, there to help inspire the scientific progress of the time.
After some discussion, the two of them came to a unanimous conclusion.
As long as they had a sample of A and B blood serum, they could roughly determine the blood type of others.
Hedy even, like a calm and composed teacher, suggested that they apply this to blood transfusions and emergency treatments. With proper sterilization and blood type matching, blood transfusions to save lives wouldn’t be a difficult task in this era.
As soon as this idea emerged, it shocked the Florence Academy. Rumor had it that their paper was sold out on the day of its publication, with even the lord’s own copy almost being stolen.
This discovery was on the level of a Nobel Prize.
Hedy only vaguely remembered the details but had unintentionally helped Da Vinci complete a historical review.
They found a time to meet with Duke Enzo again, explaining the entire process and safety of the experiment. They even performed the experiment in front of him.
The young duchess was Type A, Duke Enzo was Type O, but their child turned out to be Type B.
When the result was revealed, Da Vinci immediately reacted, taking the elderly duke into the study to discuss the matter further—or perhaps offer comfort.
