Name: 這部電影太爛了!宅男周的水蛭科學 (This Film Sucks! The Science of Leeches for Geek Week)
Uploaded: 2021-01-14T05:52:09.000Z
Duration: 4 min 46 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

For most people, they're the stuff of nightmares.

But there's a lot more to them than just slimy bloodsuckers.

Now, the leeches in this tank are medicinal leeches, and

they've got this name for a really good reason.

So for about 2,000 years, up until quite recently, it was

thought that the body's health was kept in balance by

substances called humours which flowed through the body.

Now blood was one of those humours, and if you had bad

blood or too much blood, then it needed to be drained.

Draining the blood from the body was known as

And using leeches to do this was the height of fashion in

In fact, millions were used every year across Europe.

Leeches are actually worms related to the ones you find

And they find a host by detecting shadows and movement

So if I dip my fingers in the tank and wiggle them around,

They've got both male and female body parts.

You can see it's desperately trying to find

When leeches are feeding, they inject anti-inflammatories and

an anticoagulant called hirudin that stops the blood

And it's because of these that they're still

People say that leeches inject a kind of anaesthetic so the

Now, there's actually no good evidence to support this.

And what it's actually doing is using three rows of teeth

There's about 100 teeth in each row, and it's using these

to slice through the skin to suck the blood.

It could take up to a couple of hours until it's fully

engorged, so all we can do is sit and wait.

The leech has been feeding for about two hours.

And as you can see it's absolutely massive, but it's

Now, I don't want to try to pull it off, because if the

leech feels threatened it might regurgitate is stomach

So after nearly three hours the leech has

And the wound is going to continue to bleed for at least

It's the most dangerous stunt in the fire eater's

Well, it all hinges on the oxygen in the air.