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When I looked for the deeper meaning of existence, I found that I was too skeptical for heaven and hell, for deities and spirits. Sometimes, I thought about astrophysics — roiling energy, dark matter, the multiple dimensions of an expanding universe — but it was all too vast and distant. The closest I ever got to a mystical experience was working with animals as a molecular biologist.

As a biologist, I performed experiments on flatworms, sea urchins, zebrafish, frogs, opossums, and mice. These studies required the careful administration of life and death: I merged sperm with eggs and observed early embryos when they were just three layers of tissues flattened together. At certain times, I preserved animals in formaldehyde and bathed them in chemicals that turned their bodies transparent.


In the lab, life and death were demythologized. Instead of some immense, cosmic force, they shrank into something tangible that could be contained in a Petri dish or studied under a microscope.

Watching generations of animals flash in and out of existence, I also felt time compressing. I cared for zebrafish embryos that, in a matter of days, transformed from balls of cells to larvae that roamed their tanks searching for food.

As a scientist, my job was to observe life and death objectively. But the work also made me feel part of a larger order. I could experience a different version of life and death than I did in the outside world – not as personal or intense but just as strange and profound.


When I was a graduate student, I typically began my weeks attempting to unite sperm and egg.


The process was not entirely natural. First, I coaxed female frogs to lay eggs by holding them over a Petri dish and massaging their bottoms with my pointer and middle fingers. The movement was meant to imitate the squeezing motion a male makes with his legs during mating. Once the eggs were laid, I ran a sliver of testicle over them — the organ having been separated from its euthanized owner — and waited.

With frogs, you can witness the moment of fertilization.

Their eggs have two hemispheres — one white and yolky, the other pigmented and cherry brown. Before the sperm arrive, the eggs lie every which way, tiling the bottom of the dish in a mix of white and brown. After fertilization, the eggs turn — their molecular machinery grinding into action – so that they all face pigmented side up.

Seeing a dish of brown eggs may not sound dramatic, but it felt as if some spirit or vital force was speaking directly to me through these changing colors. It was all so simple, as if life was being summoned with the flip of a switch.

“Oh that,” a senior graduate student commented after I had been staring at the eggs for several minutes. “It gets old after a while.”

But for me it never did. Through winter storms silently subduing Boston outside the laboratory windows, the rise and fall of my romantic relationship, the years congealing together, I continued to stare. I felt the same existential solemnness as I did when watching the sun set or getting lost in a melody.

It’s all here, the eggs seemed to say.

Sometimes the eggs never fertilized. I waited for hours, walking away and returning, staring and willing them to turn. I sat in a room filled with microscopes, bottles of colored solutions, and shelves packed with scientific notebooks. Beyond the walls, I was surrounded on all sides by other laboratories each aglow with the green and red lights of precisely calibrated equipment. And yet, here I was sitting like a witch next to her cauldron, dependent on this fickle mixing of flesh.

The summers were especially difficult — the eggs coming out of the frogs in long, stringy clumps. Most of them were either gray or the chalky white of dead cells. Bursting upon the surface tension of the buffer, they clouded the Petri dish.

“It’s terrible here, too,” a researcher in England told me. “Somehow, the frogs must be sensing the seasons change.”

I walked down to the frog room, located in the core of the research institute, to investigate. It was cool but damp and filled with the sound of trickling water. The animals lived in plastic tanks the size of bathtubs. I peered down at them. Their skin was a mix of pea and navy green melded in repetitive globular patterns. Lying underwater, perfectly still and unblinking, they didn’t seem to notice me at all.

The frogs looked emotionless, alien, and prehistoric. They were from Wisconsin — born in a laboratory facility specializing in animal husbandry and at least five generations removed from any wild-caught frogs originating in sub-Saharan Africa. Most likely they had never been outside, seen a tree, or sat in the mud. Their lives were climate controlled and illuminated by lights that switched on and off at the same time each day. And yet, in their meditative trance, they had become the perfect receiver of a wave or a particle, something that spoke to the cadence of the tides or tilt of the earth, something that said: summer.


Precise and preplanned, largely stripped of emotional attachment, the death of a laboratory animal is unlike most other deaths. Even now, I am not sure what to call it. My undergraduate adviser, who ran an opossum laboratory, argued against the commonly used term “euthanize” because it had the connotation of a merciful death, one that relieves pain and suffering. She preferred to say “sacrifice.”

My adviser was intelligent and irreverent. She had a habit of laughing uncontrollably at jokes and then looking around while covering her mouth. And yet, her mood transformed completely when sacrificing her animals. Like many scientists, she had a way of summoning a grim focus, as if she were becoming an alter ego.

“Hello, it’s me, Yolanda,” she said while reaching her hand into the cage, “the bad Yolanda.”

After an internship studying obese mice at the National Institutes of Health, I thought of my own term: “disembody.” The act of killing the animal was so terrible that, in my mind, I had to transform the mouse into a series of abstract shapes and colors, something other than a body.

I, too, disengaged. Rising up out of myself, I watched the scissors in my hand press into the lower abdomen of the anesthetized mouse, with just enough pressure to crease the skin but not break through. Poised on this delicate balance, I felt like a skater inching out over thin ice. When the blades plunged through, my anxiety dissipated, replaced by a steely concentration.

At the NIH, my goal was to compare the brain structure of normal and obese mice. This type of analysis requires “fixing” the brain, or chemically preserving it against decomposition. The best way to do so is to inject formaldehyde into the heart, where it travels through the circulatory system and saturates the depths of the brain.

Opening the mouse, I found a tender world with its own logic, shapes, and colors. Everything fit together perfectly, each organ tucked into place as though in a well-packed suitcase. There were barely any corners or hard edges — mainly curves, bulges, and loops. I had never seen such glistening colors before: the reddish-brown liver, the yellow intestine, everything else mostly a deep beet red. The pockets of deoxygenated blood, almost black, made the body dark and vibrant. It glowed dimly, like stained glass in the evening.

An animal’s innards are so different from its outside and yet exactly as they appear in anatomy text books. That something can be so well-described and still surprise makes it all the stranger.

Using forceps, I cracked open the ribcage to reveal a heart beating so hard that it seemed to bubble like the surface of boiling water. As I readied the syringe, the mouse shimmered before me: a system of perfectly calibrated organs, splotches of colors swimming together, billions of cells that just happened to be in the shape of a mouse. I pressed down, feeling the sigh of the syringe beneath me, and everything solidified into the mouse once more.

After each experiment, I became giddy with relief. Slumped back in my chair, I felt each breath filling my lungs before branching out into my arms and fingers. My whole body tingled. It felt luxurious.

Perfusing mice revealed the distance between thought and feeling. I could rationally justify killing mice for research but reasoning never calmed my squeamishness — at best it helped me tolerate the dread and remorse. I made a vow to never work with mammals in the future. It was the first time I had weighed my feelings in a scientific context.

Near the end of my internship, my boss, a middle-aged staff scientist, told me a story. A few years before, the custodian had found a mouse in our hallway. By its ear tag, my boss identified it as one of his animals. The mouse had escaped its cage, snuck past multiple doors, and ridden the elevator up to our floor.

“What do you think it wanted?” I asked, half jokingly.

“Revenge,” he said.


When I was a scientist, I was surrounded by the churning of life — generations of animals rushing into existence and dying. Some days, I saw myself in that churning. It was calming. Instead of being only myself, I was playing a role. All my defining traits – introversion, a streak of nonconformity, the desire to experience the world through writing – would recur in others after me.

After completing my dissertation, I joined a nonprofit’s communication team and acclimated to office life: rows of white desks with a standing desk connected to a treadmill in the corner, drafts of press releases and annual reports, inside jokes with co-workers. Some mornings, I feel a disappointed relief to be so far from animals. Mostly, though, I am content to let the intensity of the experience fade. I settle into the illusion of stasis. Time passes but nothing seems to change.

Occasionally I stumble across an exception, reminders of a larger timescale. After the dentist frowns, I ask about cavities. “Oh, nothing to worry about,” she replies cheerfully, “it’s just incipient decay.” There are more serious events: A friend’s sister has a baby; another friend visits her grandfather in hospice; a car runs into a biker near my apartment.

On a brittle winter night, six months after my last experiment, I came home to find a dead mouse at the base of my bed. The body seemed like a mirage. Kneeling down, I observed the long curve of its front teeth and prodded its head with my pinky finger. The smallness of the death allowed me to linger over it and, for a moment, I’m drawn back into the churning with equal parts dread and nostalgia: memories of the animals I’ve killed. The essence of summer nudging the biochemistry of frogs – biology as involuntary clockwork.

I’m not sure how long I spent with the mouse. I heard gusts of wind outside my window and my housemate on the phone below me. After a few minutes, I placed the body in a plastic bag and disposed of it in the trash can behind the house.

After that, over a period of days and weeks, my mind would wander. I’m 30, almost the age of my father when I was born. Stitching the second half of his life onto mine, I divine the future — friends marrying and considering children, the struggle between my parents and me to understand each other, the stories I want to tell, the person I want to become — and I will think to myself: If only we had more time.

Justin Chen is an external affairs associate at OpenBiome and a former AAAS mass media fellow at STAT.

  • There Is One Chance To Be

    Do not fear the air–
    the message of each cell is ending
    the DNA we wear is old and broken
    frazzled torn as passed-down clothing.
    A sweater can be shed
    when worn away
    but not our bodies
    borne through all the years
    we carry on but cannot stay.
    Knit and sew and stitch and ravel
    there are no maps to guide
    no sun that arcs the sky
    and measures space
    there are no roads
    Take care–
    the openings to emptiness await.

    © March 16, 2019 Carol Snyder Halberstadt

  • Excellent piece. Hits on a lot of relevant feelings in conducting animal research and their immense range of scale: from peering at cells under a microscope or a mouse that lives only a few weeks to how our own lives may fit into whatever greater narrative there is. My hope is that everyone, and especially those who experiment on animals, would never lose such perspective. And although by eventually leaving the lab we may distance ourselves from the squeamishness and feelings involved, we should keep in mind that almost all of human society directly benefits from animal research in one way or another. We are all morally implicated, whatever that may mean to different people. Unfortunately at this time there is still no better alternative.

  • Justin. Beautifully well written essay. This is creative nonfiction at its finest. I worked in clinical research early in my career at a large pharmaceutical company and the animal labs, the preclinical research was down the hall. And I recall, they used baby beagles in one set of experiments. I wondered how the researchers could manage that, and then I tucked it away.My bad. Thank you for your essay. A

  • I turn 70 years old this year, and through the ages of having dozens of companion animals, I have been fortunate not to have to euthanize any of them until this past year. All passed on from old age. I had to make the choice for one of my rescue dogs – she was 17 and had been with me for 5 years – and our special needs bunny, who lived to nearly 11 years. I had to decide in order to alleviate their suffering, a most difficult and emotional choice. It felt God-like, and not in a good way. I stayed with them and held them for 30 minutes afterwards, talking to them and reassuring them that I loved them and that I would never forget them. All life is precious, human or animal, and yet hard decisions have to be made every day as to whether it is selfish to keep them going medically, or better for them to relieve their pain and send them on to their next adventures, whatever that may be. Whether one likes it or not, the fact is, we are all connected.

  • Over 50 years ago, I worked in a lab that was researching _in vitro_ fertilization in cows and used rats, mice, and guinea pigs in its research. My contact with the animals was usually preparing frozen samples for analysis, but once in a great while, I would have the duty of feeding the small animals over the weekend. One time only, I had to gas a litter of pink and hairless one-day-old mice, the size of a baby’s finger tips, and I found it very difficult to do. Your wonderful writing brought that moment back to me and made me very grateful that I took my career in another direction.

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