Hello new folks! Wow. Yesterday, Penny Arcade joined in the bean spilling about Strip Search, and at that point I’d have to say that the bean can has been fully emptied. There are beans everywhere. If you’ve landed here from PA, you have my humblest of welcomes. I hope you enjoy your stay. If you like what you see, follow me on Twitter, like us on Facebook, and pity my new Tumblr!
Now then, onto the comic: As temperatures drop in the winter months, you might find yourself asking, “Why aren’t all those ducks getting cold?”
No? Well, you haven’t lived. Waterproof feathers are part of it, but as far as the feet are concerned, the answer lies in the network of blood vessels detailed above. Though my explanation is sadly simplistic in both depiction and scope of function. In reality, retia mirabilia are a tangled mess of capillaries, and they can be used to transfer not only heat, but also gasses, ions, and even fluids by osmosis. For example, the kidneys utilize a rete mirabile to filter waste while preserving water content. Fish use them to both help insulate their core muscles from cold water and regulate their swim bladders (used to control depth). The rete mirabile is a perfect example of a physiological structure that has been adapted for many uses over time.
I thought the giraffe neck was a particularly remarkable use of a rete. The pressure needed to pump blood to a giraffe’s brain becomes deadly when the animal lowers its head. But thanks to a unique adaptation of this “marvelous network,” these majestic animals can keep their heads from popping off. [Clarification] In the giraffe’s case, you have a single rete distributing high pressure flow over a network of smaller veins and capillaries, rather than an exchange between networks.
As a bonus, here’s footage of my family’s pet goose taking a Christmas Eve bath. You can see her collecting oil from a gland on her back to use as a sealant against water.