Stratum Corneum

I find a very fine irony in the fact that the stratum corneum, the outermost layer of human skin is composed of "horny" cells; that is, horny as in callous, not as in hungry for sex.
Actually, up to a few years ago, doctors believed that this layer was not sensitive at all, they deemed it to be some kind of protective sheet of dead cells only; recently, however, research has showed a much more intricate structure and function.

Horny, etymologically related to corneum, and to horn, to a stiff material, something rigid, something unmoving. And yet, this layer is the one that is never the same, like that river, that could never be crossed twice.