“A child who has been breathing since birth without ever noticing it does not know how essential the unheeded air that gently swells his chest is to his life. Does he happen to be suffocating in a convulsion, a bout of fever? Desperately straining his entire being, he struggles almost for his life, for his lost tranquillity, which he will regain only with the air from which he did not realize his tranquillity was inseparable.”