The newly built Konoha Hospital was the first landmark project completed by Danzo's "Konoha Construction Team."
Under the almost freakish construction efficiency of Danzo's "Konoha Construction Team," a brand new, comprehensive hospital, three times the size of the original, rose from the ground in just a few short months.
The entire top floor of the hospital was designated as the exclusive research department for Tsunade and Orochimaru.
This five-story building, using a new chakra-conductive metal frame mixed with earth, was scientifically designed with ample lighting, making it the most advanced medical facility in the entire Land of Fire.
And the research department on the top floor was specially approved by Sarutobi Hiruzen as an "S-rank classified area," possessing the most advanced equipment and the most abundant budget in all of Konoha.
At this moment, in the largest laboratory of the research department, the atmosphere was so tense it was about to explode.
"No!"
Tsunade slammed her palm hard on the special alloy laboratory bench, making a loud "clang."
She pointed at the pale-faced youth opposite her.
"Orochimaru, your idea is too crazy."
"This is precisely the data I want to observe."
Orochimaru's voice was cold and calm. He adjusted the non-prescription glasses on his nose, his golden, serpentine pupils shining with a rational light.
"Tsunade, your thinking is too confined to the identity of a doctor. We are now scientists. Science requires bold hypotheses and rigorous verification!"
Ever since being enlightened by Sarutobi Hiruzen with the concept of blood types, Tsunade and Orochimaru's research had entered a fast track.
Through a large number of animal experiments and dissections of captured enemy corpses, they had successfully verified the correctness of blood classification.
They named this phenomenon "Blood Inheritance Limit" and, based on its different agglutination reactions, preliminarily divided it into four basic types.
They named them "Type A, Type B, Type C, and Type D."
This discovery was an epoch-making breakthrough in the field of medical ninjutsu.
It meant that as long as a matching blood type was found, the success rate of blood transfusions would leap from less than thirty percent to over ninety percent!
However, new problems also arose.
How to quickly and accurately identify a person's blood type?
Their current method was to extract a small amount of blood and mix it with the four known standard serums—Type A, B, C, and D—to observe whether agglutination occurred.
This process was cumbersome, time-consuming, and required the consumption of precious standard serum.
On a battlefield where every second counted, it was simply not practical.
Thus, Orochimaru proposed a bolder and crazier idea.
He believed that the compatibility of blood was essentially determined by some unknown chakra imprint in the blood.
He wanted to find the pattern of this imprint through large-scale mixing experiments, and then develop a ninjutsu or test paper that could directly read the blood type information.
Tsunade, however, was firmly opposed to this research method.
She believed that they should start from a safer angle, for example, by studying the genetic laws of blood between parents and children.
The two had been arguing about this for three whole days, and neither could convince the other.
"Genetic laws? Too slow!" Orochimaru retorted unceremoniously. "By the time we figure out all the genetic combinations, the third war might already be over. My method is the most efficient!"
"Hmph, the benevolence of a woman."
"What did you say?!"
Just as the two were about to escalate from an academic debate to a full-blown fight.
"Ahem."
A gentle cough came from the laboratory door.
Sarutobi Hiruzen walked in slowly, his hands behind his back.
"Sensei."
"Sensei."
Tsunade and Orochimaru immediately stopped arguing and stood respectfully.
"It seems your research is progressing quite heatedly," Sarutobi Hiruzen said with a smile, glancing at the cracked alloy lab bench that Tsunade had slammed, and then at the two of them, who were at each other's throats.
"I've heard about the problem you've encountered."
Sarutobi Hiruzen got straight to the point without beating around the bush.
He walked to the lab bench, picked up a test tube, and looked at the bright red blood inside, pretending to be deep in thought.
Tsunade and Orochimaru watched him nervously, hoping that this teacher, who could always come up with amazing insights, would once again point them in the right direction.
Sarutobi Hiruzen pondered for a moment, then spoke slowly.
"Since you already know that there is compatibility between different types of blood. Some can be mixed, while others will be rejected."
"Have you ever thought... besides coagulation, are there any other manifestations of this rejection reaction? For example... is there something in one type of blood that is attacking something in another type of blood?"
Attack?
Tsunade and Orochimaru were both stunned.
Their previous thinking had been focused on the macroscopic phenomenon of agglutination.
They had never thought that on a microscopic level, a "war" might be taking place.
"Sensei means..." Orochimaru's serpentine pupils instantly lit up. He seemed to have grasped something crucial.
Sarutobi Hiruzen waved his hand and continued in an enlightening tone, "It's like a battle between us ninja. Some are good at taijutsu, some are good at ninjutsu. Could it be that there's a similar situation between blood and blood?"
"For example, let's call the four blood types you discovered Type A, Type B, Type AB, and Type O."
"On the red blood cells of Type A blood, there's a little hand called 'A antigen.' On the red blood cells of Type B blood, there's a B antigen. Type AB has both little hands. And Type O has none."
"At the same time, in their serum, there are antibodies that specifically attack these little hands. Type A blood has anti-B antibodies, Type B blood has anti-A antibodies, Type O blood has both antibodies, and Type AB blood has no antibodies."
"So, when you transfuse Type A blood into a person with Type B blood, the anti-A antibodies in the Type B blood will immediately rush over, grab the A antigen little hands on the Type A red blood cells, and stick them all together. This causes agglutination."
"The reverse is also true."
"And Type O blood, because it has no antigens, won't be attacked no matter who it's transfused into. It's the universal donor. Type AB blood, because it has no antibodies, can accept anyone's blood. It's the universal recipient."
Sarutobi Hiruzen, in the simplest and most direct way, like telling a fairy tale, explained the underlying logic of the "ABO blood group system" to the two of them.
The entire laboratory fell into a dead silence.
Tsunade, Orochimaru, and even Jiraiya, who was eavesdropping nearby, were all petrified.
Their mouths were slightly agape, their eyes wide like saucers, their faces filled with the ultimate philosophical questions of "who am I, where am I, what did I just hear."
Antigen? Antibody?
Type A? Type B? Type O?
Universal donor? Universal recipient?
What... what is this theory?
Especially Orochimaru.
His truth-seeking, self-proclaimed genius brain completely shut down at this moment.
He felt that his dozens of pages of proud research report were nothing compared to his teacher's few minutes of "fairy tale."
So... so this is the origin of blood!
"Class... classification..."
"Antigen... antibody..."
Orochimaru began to fanatically mutter these two words. A brilliant light erupted from his golden, serpentine pupils.
He could almost see the door to a new world, leading to the ultimate mystery of life science, slowly opening for him.
"I get it! I completely get it!"
Orochimaru grabbed the still-dazed Tsunade next to him and, ignoring her disgusted look, dragged her to the other end of the laboratory.
"Classification! That's right! How did we not think of that! We can create standard reagents that only contain anti-A and anti-B antibodies. With just two drops of blood, we can identify anyone's blood type in seconds!"
"We can even... we can try to separate and modify these antigens and antibodies! Tsunade! We... we're going to change the world!"
The two of them, in a flurry of excitement, left their Hokage teacher behind.
Sarutobi Hiruzen looked at their energized backs and smiled with satisfaction.
He knew that before long, the medical level of Konoha, and even the entire ninja world, would undergo a world-shaking change because of this little "tip" today.
"Sigh, geniuses sometimes just get stuck in a rut," he shook his head and silently complained to himself.
"Now that the blood type problem is solved, it's time to think about improving the villagers' diet."
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