Kahlbaum in 1863 described a form of mental disease occurring at puberty and rapidly terminating in dementia; this he called “hebephrenia.” In 1874 the same author described the condition known as “katatonia” or the “insanity of rigidity.” These terms do not appear to have been adopted till 1891, when Pick, under the heading of “dementia præcox,” described cases, including hebephrenia, characterised by maniacal symptoms followed by melancholia and rapid deterioration. This term has now been extended by Kraepelin to include the “hebephrenia” and “katatonia” of Kahlbaum, together with certain forms of paranoia which undergo early deterioration.