Numerous people say, albeit erroneously, that Kraepelin classified Kahlbaum's concept of catatonia as a subtype of dementia praecox. Using strong empirical evidence from Kraepelin and his pupils, including Dehio, Aschaffenburg, Nissl, Alzheimer, Weygandt, Dreyfus, and Lange et al., namely the Kraepelin team, we are going to correct the conceptual history of catatonia with reference to the creation of the catatonia concept by Kahlbaum and its revisions.
 Kahlbaum proposed that we should consider catatonia a "disease entity" or a "natural species" of disease in the same way we consider general paralysis. We can observe various psychiatric syndromes such as melancholia, monomania, mania and dementia consecutively in the course of a specific brain disease-general paralysis. However, what evidence permits us to group these various syndromes into a single disease entity? We can see, as empirical evidence, motor paralysis throughout the course of general paralysis. Similarly, we can see specific motor symptoms such as tension or spasm in catatonia. Accordingly, are we not permitted to consider catatonia a natural species of disease? Surely it is only a matter of time before we discover the common etiology and neuropathological findings of catatonia.
 The Kraepelin team gradually reconsidered and reconstructed the concept, definition and nosological classification of catatonia with the help of strong empirical evidence. Among the symptoms of catatonia, catalepsy appears in a wide variety of diseases in addition to catatonia. Therefore, we cannot regard motor symptoms as evidence to support recognizing catatonia as a natural species of disease. To classify the concept of catatonia correctly, we need to classify the course and prognosis of catatonia more strictly. Moreover, we should regard catatonia not as a motor disorder but as a disturbance of the will. Owing to this redefinition, we can consider the category containing catatonia with poor prognosis to be a variant of a specific disease that includes hebephrenia. Accordingly, the Kraepelin team restricted the use of the term catatonia to the poor-prognosis group and classified the renamed catatonia into a subtype of dementia praecox. They also categorized the good-prognosis group into the mixed state of manic-depressive illness as manic stupor. Thereafter, however, manic stupor was removed as the central disorder of the mixed state of manic-depressive illness and was replaced with agitated depression. As a result, it is difficult to find the connection between Kahlbaum's catatonia and Kraepelin's manic-depressive illness.
 In his later years, Kraepelin himself revised his own method of psychiatric nosology. He admitted that we can see catatonia syndromes in the course of some diseases in addition to dementia praecox. He argued that an inherent apparatus is released in accordance with the degree of invasion by a disease and that this inherent apparatus manifests itself as psychiatric symptoms, which do not necessarily correspond to their own specific disease but to the degree of invasion and the characteristics of the inherent apparatus. The sixth manifestation of 10 kinds of inherent apparatus is "schizophrenic manifestation", which is equivalent to catatonia syndrome, and manifests during the course of some diseases, including progressive paralysis, senile dementia, traumatic brain disease and manic-depressive illness, in addition to dementia praecox. Kraepelin and his successor involved in textbook revision, Lange, gave up the idea of placing catatonia into the category of dementia praecox exclusively. They considered catatonia to be a non-specific and general syndrome that is seen in various diseases.
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