The weird biology of germ-free animals is most obvious in the gut. A well-functioning gut needs a big surface area for absorbing nutrients, which is why its walls are densely lined with long, finger-like pillars. It needs to constantly regenerate the cells at its surface, which get sloughed off by the passing tide of food. It needs a rich network of underlying blood vessels to carry nutrients to and fro. And it needs to be sealed – its cells must stick tightly to each other to prevent foreign molecules (and microbes) from leaking into those blood vessels. All of these essential properties are
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Gut. Technical.
