Dermographisme [aka dermographism, dermatographismm or "skin writing] - Démence précoce catatonique, from Nouvelle Iconographie de la Salpêtrière, Paris, 1904.
From the Wellcome Collection Skin exhibition website (which featured this image):
Démence Précoce Catatonique Dermographisme. L Trepsat, 1893. From 'Nouvelle Iconographie de la Salpêtrière', 1904.Click on image to see larger version.
During the second hald of the 19th century, the belief spread that the phenomenon of dermatographism (or 'dermographism', or 'skin writing') was linked to hysteria and other mental or nervous disorders. Here a female patient at the Salpêtrière hospital in Paris has had her diagnosis 'Démence précoce' (dementia praecox) 'written' on her back.
Via Rrosehobart Tumblr.