Two treatises "semi-philosophical, semi-humóristicos" according to William James, comparative Anatomy of the angels (1825) and On the dance (1824) are two texts of youth written by Gustav Fechner under the pseudonym of Dr. Mises, edited for the first time Once in Spanish, they open a door to the world of concepts and images of the founder of psychophysics, whose studies of sensation, synthesized in the Law of Weber-Fechner, constitute the source of an emerging psychology, from which they will both psychoanalysis as the most experimental and behavioral psychology, but also the so-called "somatic techniques". A thought when it becomes sensitive, Marie Bardet's text that closes the book, traces possible current echoes of the conceptual images of sensitivity and dance of the Fechnerian world for philosophy and the corporal and dance practices of today. A world where German romanticism and positivist impulse coexist; where strange beings live, like angels, ideals of a visual-tactile sensitivity displayed along a non-linear series of thresholds between mineral, organic, human; where a young adolescent goes out to dance, ignoring the sermons of her mother and the priest, and will be able to do without this, according to Fechner, of every doctor.