Other psychiatrists, before and after Kasanin, have made scientific observations of schizoaffective disorder based on assumptions of a biological and genetic cause of the illness. In 1863, German psychiatrist Karl Kahlbaum (18281899) described schizoaffective disorders as a separate group in his "vesania typica circularis". Kahlbaum distinguished between cross-sectional and longitudinal observations. ("Cross-sectional" refers to observation of a single, specific episode of the illness, for example, one episode of psychotic depression; while "longitudinal" refers to long-term observation of many distinct episodes or different often occurring over the span of years.) In 1920, psychiatrist Emil Kraepelin (18561926), the founder of contemporary scientific psychiatry, observed a "great number" of cases that had characteristics of both groups of psychoses that he originally posited were two distinct and separate illnesses, "dementia praecox" (now called schizophrenia) and "manic depressive insanity" (now called bipolar disorders since there are more than one type of bipolar disorder and recurrent depression).