What it's like to dissect a cadaver


Why

I never thought I was a bio person. But then I overheard Viv talking about MAOIs at a party. I asked her:

> - What are MAOIs?
> - monoamine oxidase inhibitor
> - What does that mean?
> - It prevents reuptake of neurotransmitters.
> - But what *is* a neurotransmitter? What does reuptake actually mean?
> - ...
> - So life uses chiral properties of space to implement things...

Viv had the most important trait of a teacher: patience. I asked the most naive questions and they answered them. They walked with me, all the way down to the very beginning, rebuilding my understanding. It was amazing. I wanted to know more. Roadblock: finding lifeforms to study.

I wondered if non-medical students could watch dissections. You can’t get more information about an object than by directly interacting with it. The concrete world contains the abstract one. I even asked my doctor at a physical if she knew of any, and she said to look at community colleges.

After some searching, I found this: Bio 848NV. Forget viewing the dissection, you’re doing the dissection. 5 hour dissection for $60, free if you just watch. The only bureaucratic hangup is that you must pay by check. Here is the latest flyer.

This is why I love the Bay Area: there’s stuff like this and you can just do it. yes it’s weird no they can’t stop you. The boundary between scientist and serial killer is paper thin sometimes.

Takeaways

  • I’ve done this a few times now. Turns out that there’s way way way too much information to understand it all in one 5 hour session. Each time, we pick out areas and focus on them.
  • Seeing how everything fits together ‒and how big it is‒ makes understanding at different scales much easier.
  • There’s a common template to life. Seeing it in you hits different.
  • Brain has interesting connections to fractals and graph theory.
  • Maybe pan-psychism isn’t totally wrong.

What & how & why

I tell my friend Leah and she says “This is the most appealing activity that I’ve ever seen you do”. Dunno whom that says more about.

We arrive and there are 5 people around 3 cadavers. We get aprons and lab coats and start syringing what’s mostly Downy fabric softener out of the corpse. It prevents decay and smells sickly sweet.

Corpses can last a long time. One of the corpses had been dead for 5 years. And when we’re done, no, we don’t put them in a cold room. They just sit in the classroom, in a body bag. Downy fabric softener purges all.

Many random observations

There’s a crazy amount of connective tissue, and it makes a creepy wireframe surrounding your skeleton. Even the space between the folds of the brain has it.

If you exercise, we’ll know. Their insides just look different. “It’s who you are inside that matters” is a much creepier sentence now.

Veins, arteries, and nerves all travel together, wound around each other by a bunch of connective tissue. Mnemonic: VAN.

Cancer can turn your guts and lungs green, and it’s this horrible bright moldy green. Metastasized tissue is hard but ultimately crumbly like overcooked chicken liver. The stomach and intestines have textures reminiscent of damp cardboard, but they’re dry to the touch.

I finally saw a lymph node. The body has a lot of drainage into the lymphatic system.

There’s a bunch of tiny nerves and you can’t feasibly preserve all.

The etymology of the word patience is “capacity for suffering”. This is apt. You can’t rush the process, and believe me, it is a process. Exposing the VANs requires reflecting away the skin, and this takes a long time and much more physical effort than you’d think. You’re basically scraping it off, and the best tool overall is your hands. Skin in particular is much tougher than it looks, and I ended up locking a pair of forceps against a shoulder and just leaning back to pull it taut.

Speaking of the shoulder, I spent 2 hours working up through one. There are a lot of fiddly bits. I knew, but didn’t understand, that your nerves go all the way up into the brain, and that you can just trace a nerve to its source. This may require destroying the rest of the cadaver, and people have made careers following bits backward.

Hands and feet. Looking at their bones made evolution’s suboptimality obvious. No wonder our feet have so many problems: they were once hands. Hands have 27 bones each, feet 26. Over time, the bones at the top squished together, the palm became the heel, and the fingers shortened into toes. The toenails are vestigial. This is the grossest part IMO, since the extremities look so dainty compared to the rest of it, and your job is basically to flay it/them. This is the one spot where blood can still be found, even after drainage.

Corpses are ridiculously stiff. I couldn’t turn an arm over without risking snapping the wrist. Even moving a finger is hard.

Interviews with cannibals claim that humans taste like pork. I can’t speak to the taste, but it looks similar. Speaking of food, knowing how to cut a chicken transfers almost perfectly. Odd feeling to realize that.

Women have wider hips, and I wonder if that leads to increased lateral flexibility. Stacking plaster hip molds so they’ll fit into a cupboard is very annoying.

We did a face lift, and it was extra uncanny, because you actually lift their face and go underneath it to the bones. Also, your face muscles are the only ones that are directly attached to your skin. This hardcoding interests me. Facial expressions are the main reason, but are any others tacked on?

Muscles can only actively contract. Which makes way more sense when they’re in front of you. What prevents us from doing the splits is our nervous system. I am now more sympathetic to the idea that flexibility can be increased extra fast in some altered states.

Fat is grease, so it’s greasy. This will become visceral (and you will never perceive the word “visceral” the same way again) real fast, since it’s everywhere, in little flecks. Marbling isn’t just for steak. It’s sort of yellow and gets on everything.

Cutting into the skin and tissue is interesting. The skin goes way deeper than I thought, and you can stand a scissor point in it.

Brain

I finally got to hold a brain!

The cerebellum is the fern-y fractal on the bottom right. In general, it has a fractal dimension of ~2.5. 3 in 4 of your neurons are in there, and it uses just 1/10 the space. But you can live without one! It’s a low latency broad (rather than deep) neural network. It’s most famous for motor skills, but there is more.

People with cerebellar agenesis (without a cerebellum, like in the picture above) have trouble developing deep, complex relationships like most of us form with our spouses, best friends, and partners. They lack emotional nuance and complexity, and so are unable to form these bonds. This shows the role the cerebellum must play in emotional coordination.

Low latency is important.

So many neurons in a fractal make me wonder if artificial neural networks do this too. Fractal dimension continuously interpolates the regular concept of dimension, so a 2.5-dimensional space is genuinely ~evenly between a 2D surface and a 3D solid. Perhaps evolution is trying to get the best of both using fractals and folds? Interpretability idea: look at the singularity spectrum of random projections of the parameter space of a model during training.

Most of the soma (main bodies) of your neurons are on a <5mm film on the surface gray matter, and the inside of the brain is the connections between them. If you shaved a brain, the connections would be mostly fine, but many neurons wouldn’t be.

There’s a cool paper by Kolmogorov and Barzdin called *On the Realization of Networks in Three-Dimensional Space, motivated by this fact.

For graphs with the expander property, the Kolmogorov-Barzdin realization from Theorem 3.2 is the smallest possible realization of the graph in \(\mathbb{R}^3\).

What is it like to experience something?

All this dissecting led to a lot of idle thoughts about pan-psychism, and it seems a bit more plausible now. I’m no longer sure it’s not like Something to be a corpse. If it is like Something, I hope it’s pleasant. I also mused if it’s like Something to be an electron. Would electrons in a vacuum all have the same experience, since they’re all indiscernible?

A weirdly large amount of my friends wanted to join, including many I thought would be horrified. 8 (and counting) have taken the initiative to ask. 6 showed up, so far. I’ve even taken a date there, and she enjoyed it! Turns out there are more than a few people who do it for pure curiosity (besides the ones I invite). Next time, the goal is to remove the brain without damaging the optic nerve. Very time-consuming, but I’m not in a rush.

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