The trade of chemist (fortified, in my case, by the experience of Auschwitz), teaches you to overcome, indeed to ignore, certain revulsions that are neither necessary or congenital: matter is matter, neither noble nor vile, infinitely transformable, and its proximate origin is of no importance whatsoever. Nitrogen is nitrogen, it passes miraculously from the air into plants, from these into animals, and from animals into us; when its function in our body is exhausted, we eliminate it, but it still remains nitrogen, aseptic, innocent.