Every year, tens of millions of experiments are performed on living animals.  In the EU, 93% of these animals are mice, rats, birds, fish, frogs, or invertebrates.  Usually, when the test is finished, the animal is killed.  

The test I witnessed was done in order to determine if further research would be possible.  Depending on the outcome, the course of future testing could be altered by a matter of degrees.  The research is performed in a series of tiny steps, and while the scientists have a vision for what they eventually want to understand, no single experiment is designed to be ground breaking.  

In this lab, they are researching heart attacks.  For that reason, there is a scientist who goes to work each day and performs a simple heart surgery on mice.  He opens up the mouse, and puts a thread stitch into its heart.  Typically, a mouse can survive that, and in the lab I visited, many mice live on after being stitched back together. 

On the day I was there though, the scientist needed to analyze the mouse's heart, liver, and spleen.  Therefore, the mouse would die. Its head would be held in place while its tail was pulled three times in order to break its back. 

"That part of it I never got used to," the scientist told me.  "When I have to kill them.  That part, I still feel it." 

I am keeping the scientist anonymous, because animal testing is very controversial.  In his lab, there are many locked doors, and locked wings of the building.  Even he only has access to areas he needs for his research.

"It's routine now," he said.  "Some days, I can do eight surgeries."  

"So four before lunch and four after?" I ask him.

"Something like that," he said.

"When I started," he said, "it was difficult to catch them."  He reaches into the cage and takes the mouse by its ears.  He holds it upside-down, and injects it in the stomach, explaining that if he does it wrong, blood will come out at this stage, and that it happened a few times, but now it rarely does.

"We're looking at different things," he explains.  "All of it to do with the heart.  Usually, it is to do with stem cells, and whether they can be used to help injured hearts."  

Today, it is different.  Today, he is working on an idea that the time of day that a heart gets injured can effect the patient's recovery. He says it was inspired because they noticed a lot of heart attacks happening at certain times of day, and wondered if that could change the way the heart reacted to injury.

"So this mouse will help solve that?" I ask him.

"Sort of," he said. "I want to check on something in the heart.  So I am going to mince them up and look at them. I want to find out if its feasible to do the same thing for more mice. It's a proof of principle."

He hooks the mouses teeth to a string.  He made this apparatus himself.  He pulls the string tight, and the mouse is held back in position by its teeth.  It is unconscious.  Powerful lights show him where to put the breathing tube.  If it goes wrong the mouse's stomach will inflate when he turns the air on.

He tapes the mouse onto a heating pad.  First he tests the breathing.  It is working.  Then he tapes one front paw, then the other.  

The mouse's back left leg is crossed over the right.  This way, when the mouse is fully taped down, its heart will be directly beneath the lights and the microscope and available for cutting.  

He uses hair removal creme to take the hair off the mouse. He puts creme on its eyes, which are still open.  

As I am watching the scientist and asking him questions, I am struggling to avoid calling the mouse "him." I am embarrassed because it seems childish.  I try to call the mouse "the subject" once but that sounds weird too. 

He cuts the mouse open, showing me how to move the ribs out of the way, and get the muscles to come apart, and how hooks are used to hold the hole open.

The beating heart is visible once he cuts the mouse open.  The scientist shows it to me, and lets me look through the microscope.  He can push it from side to side if he wants.  He tells me that a mouse heart is very strong.  Doing this to a human would be extremely dangerous.  The heart is the size of a pea.  It is red and blue.  

Now he will give the mouse a heart attack. 

Using a tiny suture, he puts a stitch into the coronary artery, and ties a knot in it.

The mouse is then stitched back together.  24 hours on pain killers, the scientist tells me, and this mouse could live a normal mouse life, even with a stitch on its heart.  He holds it in his hand.  It is limp, but still breathing. He turns it onto its stomach, grasps it by the neck, and pulls on the tail hard.  Then again.  Then a third time. 

Later, the scientist brings me into the room where the mice are kept.  "Here is my team," he tells me.  There is a little family of mice in a box like you would see at a pet store.  His mice are all small white mice.  "I like to give them some paper towels.  They like them.  They tear them up and they can make houses or whatever.  It makes them happy," he said.  

Some of the other mice, next to these have massive growths.  "Tumor mice," he tells me.  Others have red signs on their cages, showing that someone witnessed a fight in the cage.  Others have skull and crossbones, indicating that for whatever reason, there is reason to be concerned that they are toxic.

Once his mouse is dead, the scientist's cuts are still somewhat careful, but less precise.  No tape is used.  The mouse's limbs are pinned down.  It's body is opened.  Using a scissor, he takes out the heart, and puts it in a petri dish.  "See?" He said. "It keeps beating."  He stirs it with the scalpel, and yes, it beats. 

"How?" I ask him.  It is amazing. "Is it still alive?"

"It's just energy left in the cells," he says. 

"50% of people don't believe in animal testing," he told me.  He puts a date on a little paper, which is the mouse's death certificate. He stitches the mouse back together somewhat after removing the heart, the spleen, and part of the liver.  Each is put into a tiny test tube and sealed.  After the weekend he will grind them up to analyze them, testing for levels of enzymes.  The result has a meaning to him, but it is a tiny step in a very long journey.

He put the mouse into a little sandwich bag.  It occurs to me how small the mouse is.  He walks to the freezer, and tells me not to look inside.  I look anyway.  Then he puts the mouse in, near many others. 

To reach a conclusion, hundreds of experiments like this will need to be done.  Some mice will be given treatments, others will not.  The way the hearts react will be looked at, over many many experiments.  If it is a success, the experiments will need to be repeated many more times in other labs.  Dozens of minor variations will be checked, and hundreds more mice will be asked to verify or falsify results.  Each life is like a drop in a rainstorm.  Regardless, it was hard not to call the mouse "him" while it was alive. 

"He did his duty," I said.

"He did his duty." the scientist agrees.