Based on this alone, Theonia was a place Greek doctors yearned for.

Davos pried open the outer skin of the model’s jaw and neck, revealing the passage inside. “Everyone, please look. The passages of the mouth and nose merge here, then split into two passages again—”

He pointed to a flexible tube made of tanned leather. “We all know that the nose is used for breathing air, but the mouth breathes air and also eats and drinks. Air and food each take their own path. Through long-term observation, doctors at the Medical School believe that this tube carries air, so they call it the trachea. The other passage behind it carries food and water; we call it the esophagus. Feel the lower part of your neck; the harder, uneven tube under the skin is the trachea.”

The foreign doctors below the podium actually touched their necks with their hands to feel the trachea Davos mentioned.

“Some might ask, since the openings of the esophagus and trachea are connected, wouldn’t food and water easily enter the trachea?” Davos said, seeing many nodding. He smiled and continued, “In fact, this is almost impossible. There is a very soft bone at the opening of the trachea. When we swallow, it automatically covers the tracheal opening, preventing food and water from entering. If you are interested, after the meeting, you can come and take a look. This human model, crafted with exquisite skill by Theonian artisans under the guidance of doctors, is quite accurate. However, don’t break it; this model is the treasure of the Medical School, priceless! Isn’t that right, Herpus?”

“Yes, Teacher Davos. Usually, we only use it during teaching and generally don’t let people touch it,” Herpus laughed.

Hearing Davos and Herpus say this, the foreign doctors itched with curiosity. They stood up one after another, craning their necks to look at the human model beside Davos, causing a bit of disorder in the venue.

Davos continued to ask, “I heard that the young Doctor Kritos of the Medical School discovered this cartilage. For this purpose, he specially dissected living pigs and sheep to carefully observe the movement and mechanism of this cartilage, is that correct?”

“Correct.” Herpus nodded.

“Is he here today?” Davos asked with a smile.

“He is.”

“Then, please stand up, Doctor Kritos, and let everyone know you,” Davos said loudly with a smile.

Under the urging of his colleagues, Kritos stood up shyly.

“Let us thank Kritos for this important discovery with warm applause!” Davos applauded first, and then thunderous applause erupted throughout the venue. His classmates even whistled excitedly.

Kritos was both nervous and excited.

Lycas looked enviously at Kritos standing in front. This doctor, who appeared to be about the same age as him, was shyly accepting the applause of the whole venue. When will I be able to make a name for myself in Magna Graecia like him, instead of always being an apprentice like a servant every day?

“Kritos, I look forward to you making more discoveries and greater achievements in medicine!” Davos encouraged him enthusiastically.

A young man encouraging another young man with the tone of an elder might seem laughable, but most doctors present didn’t think so. Kritos was so excited that his chest heaved rapidly. “Yes… yes, Teacher Davos!”

After Kritos sat down, Davos continued, “If you sometimes eat carelessly, you might suddenly choke and cough. This is actually because the cartilage didn’t cover the trachea in time, causing food to enter the trachea. If a mother brings an infant to you for treatment and tells you, ‘The child keeps choking when drinking milk,’ it might actually be due to this reason…”

Davos’s words were memorized by the foreign doctors, corroborating similar cases they had seen before.

“Air travels down the trachea into an organ. After multiple dissections, the Theonian Medical School calls this organ the lung,” Davos said, prying open the chest of the human model and detaching the left lung carved from wood to show everyone.

“Dissections at the Medical School found that there is a lung on each side of our body, left and right. It’s like a pig’s bladder children play with. When inhaling, air enters, and the lung expands; when exhaling, air is expelled, and the lung shrinks. You might find it strange that air enters the lungs from the mouth and nose, then is exhaled from the lungs through the mouth, returning to the starting point after a circle. It seems meaningless. But I tell you, our body is the most precious treasure bestowed upon the world by the gods; it is marvelous and never does meaningless things!”

Davos looked around at the doctors below. Seeing they were all listening intently, he said seriously, “After multiple dissections of corpses, the Medical School found that after the trachea enters the lung, it continuously branches downwards into finer tubes, just like a big tree branching into twigs. Finally, how big are the tubes we can see?”

Davos pulled a hair from his head and said, “Just this big! And what is at the end of such a small tube? Who can tell me?!”

At this moment, a young Theonian doctor stood up. “Blood vessels! During dissection, we found many equally tiny blood vessels intertwined with these air tubes. These tiny blood vessels are formed by the continuous branching of two large blood vessels coming from the heart…”

“Then, what is the use of these two large blood vessels coming from the heart?” Davos continued to ask.

“They come from different locations in the heart. One is responsible for pumping blood to the lungs, and the other is responsible for collecting blood back from the lungs.”

“Any other obvious differences?”

“Um… the one pumping blood out is one vessel, and the ones collecting blood back are two vessels…” the young doctor answered hesitantly.

“That is a difference. Anything else?”

“Uh…” The young doctor blushed and couldn’t answer.

“Thank you for your answer. What is your name?”

“Strobus of the Theonian Medical School.”

“Thank you for your wonderful answer. You spoke well!”

Strobus, who had been slightly dejected, smiled again upon hearing Davos’s praise.

“Gentlemen, air circles in the lungs and goes out; blood circles in the lungs and returns to the heart. If nothing happens, our bodies would be too bored, idle enough to do such meaningless things all the time. Is this possible?!” Davos asked a question, provoking deep thought, then answered decisively, “Of course not! Air and blood must undergo some marvelous reaction in the lungs, only invisible to our naked eyes, just like we can’t see what causes our wounds to get infected. So what is this reaction? How important is it to our bodies?”

Hearing this, the doctors showed great interest. While thinking, they perked up their ears to listen to Davos’s next words.

Davos smiled. “Although I don’t know what reaction occurs between blood and air, we can discover the existence of this reaction through certain phenomena. Herpus, have you carefully observed the blood in humans or animals? Did you find any difference in the blood?”

“Blood?” Herpus fell into thought. To be honest, Davos hadn’t informed him of the lecture topic beforehand. Like everyone else, he was accustomed to transparent air and hadn’t thought deeply about this issue. Plus, having served as the head of the Ministry of Health and concurrently as the Dean of Thurii Hospital and the Theonian Medical School for the past two years, administrative affairs had increased, leaving him little time for medical research.

Beside him, Stesichordas also fell into deep thought.

“Oh!” Someone suddenly remembered something and shouted, “It’s the color! The color of the blood!”

Davos looked closely; the speaker was Kritos. He looked appreciatively at this young doctor who was good at thinking and full of original ideas, then quickly withdrew his gaze. “Exactly, it is the color of the blood! Doctors of the Medical School, if you have done vivisections on animals regarding this, you will find that the originally dull-colored blood entering the lungs becomes bright red when brought back to the heart by another vessel. Only air and blood flow in the lungs, so something in the air must have entered the blood to change its color! And what role does this thing… this invisible thing entering the blood play?”

Herpus, Stesichordas, Kritos… all the doctors, including Lycas, stared intently at Davos, holding their breath, fearing to miss a single word.

Davos’s expression also became serious. “We notice that the blood returning to the heart is pumped by the heart to all parts of the body. The bright red blood is manifested on our bodies. Our lips are red, our fingertips are red, our faces become red after exercise… When we see a person with these characteristics, based on our years of medical experience, we can easily judge that this person is healthy and energetic.

“However, we sometimes encounter patients whose lips are purple, extremities are black, faces are blue, and who walk tremblingly… We can also easily judge that this person is sick, and very seriously so. Isn’t this the change manifested on the body due to the blood mixing or not mixing with this thing from the air?! Can we consider that this thing is as indispensable to the human body as food, making us healthy and energetic?! Can we also infer for these patients with purple lips and black fingertips that something went wrong in their trachea, lungs, blood vessels entering the lungs, or blood vessels returning to the heart, preventing this thing in the air from reaching the whole body through the blood?!…”