Rats! Or the more unpleasant part of making anatomy models.

In the words of John Hutchinson: Stomach-Churning Rating:  7/10; some inconvenient and unavoidable truth about my work. And I added some photos of the real stuff. I put them below the screen line so you can prepare yourself.

Not just data

In order to make the anatomy models, I can’t just rely on papers and research data. One of the more unpleasant parts of my job  is that I have to do the hard stuff and dissect the animals myself. Animals as in plural because for each model one animal is not enough, unfortunately. With mammals for example, I need one for the skeleton, one for the intestines and one or two for the muscles. The rest of the data I try to extract out of those animals and out of research data.

Because I need more than one animal, I can’t kill them myself (and even if it was one animal, I would have a lot of trouble with it, I have to admit) and most of the time I don’t find them just lying around. Road kill doesn’t work either. Luckily, the animals I am planning on working on in this year are also considered food for several pets.

Rats, for example, can be bought as snake food and pigeons, chickens and rabbits too. They are even advertised as food for dogs and cats, so I don’t have to go to some obscure shop in the middle of nowhere to get the animals I need.

So how are those animals killed? Since they are whole, they don’t have wounds or stressed looks, and nothing seems to be done with them except for them being dead, I guess the stores I buy from kill them using carbon dioxide. Carbon dioxide anesthetizes an animal, thus making it a relatively friendly dead. When the animals are dead they are put into a sack by the dozen and then in a freezer.

And that is my luck. If I defrost the animals, the colors and structure of the skin, muscles and intestines are almost as when the animals where alive. The only problem I encounter with dead animals is that I sometimes have to guess the real life position of the internal organs. Luckily most of the animals I work with are popular research subjects and most of them are scanned alive, thus giving me the position data.

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For the animals I described here I have to start with the skeleton. I would love to do it the other way around, resulting in less animals to be used, but unfortunately I just can’t rely on photo’s alone to make my models. I do take an enormous amount of photos and even film the dissection to be able to recall all the fine details, but most of the time the work goes as follows: I dissect for half an hour and then work on my pc making that part of the model. With the skeleton I can keep the separate bones with me while modeling, but you can imagine that having an open rat and trying to look at all the details while simultaneously modeling just doesn’t work.

And that is also why I need more than one animal for the muscles: making a model like the rat cost me several months to build. So the rats I need have to be preserved while I am working on specific parts of the model. I preserve the animals in denatured alcohol. Denatured alcohol has its pros and cons: it actually firms the muscles thus making it easier to dissect, but it also changes its color and structure. So the first day I have to take pictures like a mad man in order to have the right colors and such. In the days after that I dissect as much as possible while working on the 3d model. Since dissecting an animal also destroys it, I am never able to get everything I want to see all at once.

 

The actual work

As I said before, I start with the skeleton. For that I cooked one of the rats I used. When you cook a rat, you know why we don’t consider it a source of food. Rats stink. They really stink. But cooking gets the job done and it is a lot quicker than putting a rat in the ground or in an aquarium full of beetles. That rat will become the standard everything else has to fit into. So I look for the most average rat within the bunch when I have to do the skeleton. I start modeling with the head for logical reasons: it gives a focal point and is of course one of the most interesting parts of a skeleton.

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And then I work my way back via the vertebrae, ribs and legs towards the tail. Luckily mammals are sort of symmetrical, at least regarding the skeleton, so if I can I middle what I see from both sides but only make one of the sides to mirror it later. Making the skeleton takes several weeks. The skull is the hardest part of course, but even the individual vertebrae take time to make perfect. I place all the parts of the skeleton in a standard position that fits how the animal, in this case the rat, is build and moves.

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When the skeleton is finished I start working on the intestines. Those are actually one of the easier parts of the job: most organs are easily distinguishable from each other and have a recognizable shape. And, if the animal I am working on is really fresh, I only need a day to work on those. At least for mammals that is. The hardest part of the intestines to make is the mesentery. But everything else is rather easy to do because I don’t have to cut one organ to see another. The only thing I have to take into account is that what I see in the rat I just opened doesn’t necessarily have to be the configuration all other rats have. That is why I use both real animals and research papers to make sure the model is accurate.

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The muscles are a different matter. As I wrote already, the intestines are easy, also because I don’t have to cut anything to see everything. It doesn’t work that way with the muscles. Ideally I work from the skeleton up. So I actually have to dig into the muscles because the muscles hold on to the skeleton and aren’t neatly arranged (they actually are, but not in a way that helps) so I can’t see every muscle from the outer layer. That is why I work by region of a rat. First I try to see as much as possible from the outside. Then I carefully dig in. I know my anatomy so I know what I can and cannot expect. But some aspects you can’t find in anatomy books (or at least not in most of them). Did you know for example that a rat has a (big) muscle that controls its skin? It protrudes from its forelegs and is one of the muscles I still have to examine properly.

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I face two problems with modeling the muscles regarding time: I have to make a plan on how to put every layer of muscle in its right place and still keep track on where I am and I can’t do one region within the time that the rat looks like it did when it was alive because of its complexity. That is why making the muscles upon the model takes the most amount of time. There are a lot of muscles and they are easily overlooked if I am not careful.

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Until now I only did a part of the vascular system using the dissected animals. The rest I made using research papers, mostly from Science Direct. The lymph system has the same problem: I need a microscope for that, which I don’t have yet.

The brain is a completely different matter. Denatured alcohol doesn’t reach the brain in the preserved rats I used, so I used scanned data. But I am still thinking of doing a dissection of its brain to see the real colors and material. But for that I need a frozen brain.

And a microscope.

I hope I can soon start working on a new rat again, finishing the forelegs and the lymph system.

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