It's actually kind of dated. What it refers to is often referred to as fascia and the extra-cellular matrix and it's importance has been known for about a decade. I'm a med / anatomy nerd
. Prior to that, fascia was viewed and nothing terribly important, just a covering to stop friction, but a lot of research has been done and it's now known that it interacts with the nervous system and is heavily involved with proprioception. It's also involved in endocrine / neuroendocrine function and the lymphoid system among other things and there is still much more to learn. It really is fascinating stuff.
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I have a piece of paper that says ASD Level 2 so it must be true.