Because the mystery version of the microscope is based on magic, unlike Earth, it is not a big deal to observe multiple targets at the same time with a single microscope. Even this fandom version can do things like the earth's dissecting microscope, making the observation sample appear three-dimensional.

However, Fen didn't plan to use such a complicated operation, and the second sample she was going to present was the leaves that she had ordered the apprentices to pick before. In the same neat and concise motion, she skillfully removed the membrane of the lower epidermis and placed it on the stage after the same treatment.

With a sample of an animal and a sample of a plant, Fen was able to explain the characteristics of each part of the cell and the differences between plants and animals. In order to let everyone know the cells more clearly, she also took the epidermis, blood and other substances from someone and introduced them. It makes someone feel like they're being treated like a guinea pig, and the guinea pig has to help control the picture in class.

There are only one kind of animal and plant cells, and of course it is impossible to delay it for too long. After all, the academy in the lost land is not like the school on Earth that has the pressure of exams, so the teacher has to say things like 'here is the point, and the exam will come out later' from time to time in class.

Teaching in the Lost Land is more like the concept of making a briefing on Earth, talking about the key points, and then outputting a lot of information. This is something new to someone after taking a few math lessons.

In particular, the people who come to this advanced course are magicians, and they still have a deep foundation, not the kind of apprentices who have just received enlightenment. And those who can become full-fledged magicians have no problem with memory and comprehension. To put it simply, it's the feeling of teaching a top student. It's no wonder that teaching in the Holy City, if you don't do well, you will be ousted from power.

The definition of teaching well is also very simple, either the new content is shocking or subversive enough, or there is so much new content that others have no time to accept it. If you can do these two things, you are a good teacher in the mouth of this group of students.

Therefore, after talking about the basic differences and patterns of animal and plant cells, Fen directly introduced the cells of all parts of the human body. It includes the differences and uses of each cell, the purpose of the organs that the cells are composed of, and the uses of the internal systems of these organs.

And then one of the things that is gratifying, the next introduction is to use pre-prepared pictures, not to collect them on the spot. Someone escaped the fate of being dismembered.

However, although these new knowledge were new, they did not touch the calm hearts of these old magicians. Everyone was studying in class calmly, quietly copying notes. Of course, someone could have guessed such a situation at the beginning. After all, the masters who are obsessed with the land all take the practical route. It's so purely academic that it's hard not to wonder 'what's the use of studying this'.

So with thirty minutes left in the first life lesson, the syllabus suggested by Lin would take a small direction. Fin's ability to control time was so precise that even if she didn't look at the pocket watch, which someone had made a long time ago, and which is still one of the Lich's trophies, and she couldn't get it back, woohoo, or the clock, she could still say an hour and thirty minutes after the class began:

"The above is an introduction to the cells in various parts of the human body. Any visible organism, including humans, can be classified as multicellular organisms, that is, each organism is composed of thousands of cells with different functions. So the question arises again, are there single-celled organisms? It is the kind of organism that has the ability to move, reproduce, etc., in a single cell. ”

Without waiting for anyone to answer, Fen asked, "May I ask who of you here has brought water?" ”

Although no one answered, none of the magicians opened their mouths to chant incantations, and they easily used a ring of apprentice-level magic, the water gathering technique, which condensed into water balls in the air.

"I'm sorry, guys, I didn't make it clear. I need water like drinkable spring or well water, not magically made water. ”

The water balloon in the air dissipated silently. One of the magicians took a parchment of the water bag and said, "This is the spring of the Elven Spring in the forest, can this water be used?" ”

The spring water of the Elven Spring, one of the specialties of the holy city of Estali, is a high-priced product. It is said that long-term drinking will help the magician accumulate power and increase the speed at which it accumulates. However, people who are not suitable, or who drink too much, will experience symptoms of resistance.

"Yes, that's great." Fen took out another empty petri dish, came to the magician who spoke, and said, "Please pour some on this glass dish, and you're done." ”

Despite the high price of the Elven Spring, the small vessel did not seem to have even a mouthful, and the magician with the spring water did not care about anything, and directly poured half full.

"Yes, folks, this is the spring of the Elven Spring. Let's take a look at what's in store here. ”

Back in front of the podium, Fen did not do anything with the water in the Petri dish and placed it directly on the stage of the microscope. The next operation was to be carried out by herself, not by Lin, who was an assistant. The operation is not just a simple micromagnification, but the analysis function and comparison of the program are turned on. Looking at the constantly updated data on the screen of the Water Mirror Technique, Fen smiled: "Hehe, this world in the water is really exciting." ”

The analysis was fast, and it didn't take long for it to be all done. "Between three and four milliliters of water in the dish, a number of different types of microorganisms were detected, most of which were not very large," Fen said. But this is the most important,—"

At this time, a large number of long-shaped, rounded, spor-free, rod-shaped bacteria are displayed on the hydroscope screen.

- Escherichia coli, which mainly lives in the large intestines of animals. Some strains are beneficial bacteria that make substances that the body needs and prevent the growth of other pathogenic bacteria. However, some strains can cause food contamination, which can cause symptoms of food poisoning in those who eat them. Common manifestations include vomiting, abdominal pain, and diarrhoea. In addition to the intestinal tract of living organisms, it is mostly found in the environment contaminated with feces. ”

As soon as Fin's speech came out, everyone was in an uproar.

Are you kidding! This is the Fountain of Elves, one of the most popular items for mages in the Holy City, which can be used as a material for crafting items or can be drunk directly. The person who provided the Elven Fountain was not an unknown young man, but a well-known veteran magician, so it was impossible for him to come up with a fake, nor would he deliberately deceive people.

The water in the glass dish was poured out of the sheepskin pouch in front of the eyes of the people. Although it was taken to her strange machine by the lich to be examined, there was no chance of a move in front of everyone.

So what is it about saying that there are things in the water that can poison people? It even has something to do with feces!

There has always been only Fen performing in class, and someone finally spoke at the bottom. The first question was: "Did you make a mistake, Sir Fen Ni?" How could there be something poisoning in the Fountain of Elves? I haven't heard of anyone dying from drinking the Fountain of the Elves. ”

"What do you think 'poison' is? Simply eat something that will kill you? Here I will introduce another concept, lethal dose. Everything is poisonous, but the question is how much you have to eat to kill you. Some things are so poisonous that even a little bit of powder, if it gets in your mouth, can kill you. But there are some things that are not so, like chronic poisons, which accumulate in the body. When the accumulated amount reaches a certain level, it will cause the human body to suffer from disease and death. Although the mechanism of operation of disease is not exactly the same as that of poison, there are still references in general. ”

"What do you mean?"

"These single-celled organisms, I call them bacteria. Bacteria are ubiquitous, but they may or may not be more or less when ingested. In small amounts, the body's immune system automatically eliminates these disease-causing bacteria. However, if the amount is too large to be eliminated, they will induce human symptoms, which is called illness. As for yourselves, has no one ever become unwell because of drinking the Fountain of the Elves? In particular, the characteristics are similar to what I just mentioned. ”

"This ......," the magician who asked was momentarily speechless. Because the illness just mentioned is actually the resistance that occurs in those who are not suitable. In the end, he could only reluctantly argue: "This is all secondary? ”

Fen was not angry at the distrustful questions raised by others and the suspicious glances cast by others. Instead, he nodded to Lin and began to show pictures one by one.

The first image is of a half-abandoned village with dead bodies lying on their backs. The very few people who seem to be alive also look miserable. The deceased did not die of war or demonic beasts, but had abscesses of various sizes on his face and body, and the ends of his limbs were blackened.

At a glance, those present recognized the disease as the infamous Black Death, the plague.

"This is a record I left behind when I heard about a plague somewhere during my travels and went to observe it. It is generally believed that this infectious disease is transmitted by rats, but in fact there are two vectors of infection, in addition to rats, there are also fleas, but they only serve as a bridge for the spread of the disease. The main pathogens are—"

Lin changed the picture at the right time.

Yersinia pestis is similar to the E. coli shown earlier, but the cell is longer and segmented, and it belongs to the bacillus diplococcus. The cause is that the drought is followed by excessive rainfall, which causes plants to grow in large numbers, causing herbivores and insects to multiply, and rats to multiply because of the abundance of food, which exceeds the number that can be controlled by the rat feeder, and then expands the disaster. The way to prevent it is to prevent rodents, rodents and fleas, and not to go near infected people to avoid continuing to transmit infectious bacteria. ──”

In the next picture, there is another rundown of a village. The same dead, but unlike the villages where the plague died, the faces of the dead here were haggard, as if they had dried up.

This is another village, infected with a type of plague that I call cholera. The main characteristics of infected patients are diarrhea, dehydration, vomiting, muscle twitching, etc., which in turn leads to sunken eye sockets, clammy skin and lack of elasticity. The main mode of transmission is through water or food contaminated with the faeces of the sick person, and the way to prevent it is simply to isolate the sick person and drink clean water. And the main pathogen is—"

Another picture.

- Vibrio cholerae. The thallus is short, but there are single flagella, pili, and some have capsule. There is no good treatment, and the only thing to pay attention to is to avoid dehydration. Therefore, we can only keep replenishing water and wait for the patient to survive this hurdle on their own. ”

After that, Fen went on to display several plague-rated infectious diseases, as well as bacteria in the main lesions. Now, the masters under the change can't sit still!