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12 Underappreciated (But Equally Precious) Bodily Fluids

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Blood, sweat, tears? Classic bodily fluids. And then there’s mucus, spit, semen, and urine—well known to juvenile minds everywhere. But blood, for instance, only makes up 9% of your total bodily fluid. What else is oozing around inside you?

1. Interstitial Fluid

Interstitial Fluid, AKA tissue fluid, works in conjunction with lymph and plasma (the liquid part of your blood) to maintain your body’s internal pressure and make sure your organs and other fluids properly interact. Most interstitial fluids have a specific job and a specific name, like peritoneal fluid, which lubricates everything inside the abdomen, or pleural fluid, which coats the lungs to allow them to do that whole oxygen exchange thing so you can live. And you were giving air all the credit.

2. Lymph

Lymph is pale and doesn’t look like much, but it plays a huge role in keeping you from dying. Several roles, in fact. It runs throughout your entire body, identifies bacteria and viruses, carries them to your lymph nodes to activate the immune system, then meets up with your blood stream to deliver important items like proteins and infection-fighting white blood cells. It delivers fats from your digestive system to wherever your body needs them (fatty lymph is called chyle), and toxins to the excretory system for disposal. And all the while it helps interstitial fluid maintain that fluid balance. Imbalanced fluids result in swelling, like in the ankles of pregnant ladies.

3. Serum

If plasma is blood without the red blood cells, serum is plasma without the clotting agents like fibrin and platelets. Of its many roles, it’s best known as “the stuff inside a blister.” Blood and lymph both contain serum, but all three exist separately in the body, and serve different purposes at different times. But serum is the most basic of the three, which kind of explains its all-purpose, old-timey name.

4. Aqueous and Vitreous Humors

And speaking of old-timey names—yes, you have humors. But these aren’t the “black,” “yellow,” “phlegm” and “blood” humors, the imbalance of which ancient docs claimed were the source of all malady. These fluids are humors in name only, and are necessary to eye function: The aqueous humor is a clear fluid that brings nutrients to the lens area of your eye, so that you’re not—you know—looking at blood all the time. The vitreous humor (or vitreous body) is the gelatinous goop that fills the inside of your eyeball.

5. Bile

Bile is another term misused by physicians of yesteryear—the black and yellow humors were called “yellow bile” and “black bile,” too much of which would make a person overly idealistic or melancholy, respectively. Real bile, or gall, is produced by the liver, held in the gallbladder (Greco-Romans were right about that part) and it squirts into the beginning of the small intestine when you eat. Its salts act kind of like soap, breaking down fats into more absorbable/digestible bits. Along with urine, bile helps the body excrete most of its toxins and other undesirables.

6. Cerebrospinal fluid

Cerebrospinal fluid—or CSF to the cool kids in the know—surrounds the spinal cord and brain, and fills the hollow spaces all up inside them. Not only does it cushion your all-important central nervous system from potential trauma, it also removes cell waste, and delivers hormones that help the brain and spinal cord communicate with the rest of the body.

7. Endolymph

Endolymph is not really lymph in the aforementioned sense. It’s the fluid in your inner ear that helps you keep your balance. Like the bubble in a level, your endolymph holds its place in relation to gravity, while your body moves. Small hairs in the ear detect the position of the endolymph, and tell the brain how best to maintain your equilibrium, so you don’t wind up hurling that...other...bodily fluid.

8. Sebum

Sebum is a fancy word for skin oil—that stuff you have way too much of when you’re going through puberty. Secreted by sebaceous glands, sebum is odorless, but can collect zit-causing bacteria, which stinks as it decomposes.

9. Milk

Milk only occurs in some humans of course, but the mammary glands that produce it are similar to other glands in the body. Scientists believe they probably evolved from either sweat glands or the aforementioned sebaceous glands. What you’ve heard is true: Men have the right hardware for lactation, and if the necessary hormones happen to be present, they, too, can nurse their young.

10. Female Ejaculate

Female Ejaculate is another lady secretion that has the scientific community pretty baffled. Studies strongly suggest that the fluid most closely resembles prostate plasma, and may originate in lady glands analogous to the male prostate.

11. Cytosol

Cytosol, or intracellular fluid, is the fluid inside a given cell—unlike all the other fluids we’ve mentioned here, which work outside and around cells. Remember those cell cross-sections you had to draw in middle school biology? Cytosol is the gunk in which all the other parts of the cell are suspended. You may never lay eyes on your intracellular fluid, but it makes up a whole third of your total fluid volume.

12. Cerumen

Cerumen is just the fancy name for earwax, a combination of sebaceous and modified sweat-like secretions that protect the ear canal from potentially harmful foreign bodies. There are actually two kinds of earwax: the brown, sticky “wet” kind, and the grey, flaky “dry” kind. Turns out there's a genetic difference between the two, identifiable in a single DNA base pair. Wet-type cerumen is the dominant type, more common in people of European and African heritage. Dry-type cerumen is recessive, and more common in people of Asian and Native American decent. Tracing the earwax gene has recently given researchers a window into the history of human distribution.

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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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