Kraepelin's diagnostic classification of the endogenous psychoses received world-wide acceptance, but today it is generally considered to have failed and is at times rejected by some workers with a few scornful words. This is not due to Kraepelin's own work but is the result of the way in which his successors have used his concepts. Kraepelin himself was not satisfied with the rough division of the endogenous psychoses into the two forms of manic-depressive insanity and schizophrenia, or as he termed it, dementia praecox. He, in fact, never ceased trying to isolate more disease entities. Thus, for example, he differentiated a large number of special forms of schizophrenia. Although he defined the two major groups of endogenous psychoses, this did not mean that he limited the number of diagnostic categories. On the contrary, he investigated all special forms of mental illness very carefully. If he saw a clinical picture which was unknown to him he would say, “So far I do not know this clinical picture, we should describe it adequately, perhaps other cases will occur as well, which will allow the isolation of a characteristic clinical picture.”