[The problem of acalculia: a study of a case].

1)The Authors describe a case of acalculia and emphasize some peculiar aspects, the study of which was facilitated by being the patient a mathematics teacher. 2) The patient was unable to perform arithmetic operations (addition and subtraction) but was able to carry our more complex and algebric operations. The acalculia was associated with constructional apraxia. 3) These findings are discussed and the hypothesis is suggested that simple mental arithmetic calculations need spatial operations which are not required for more complex mathematical reasoning and that the ability for calculation may decline by the very same progression, one level after the other, as the language.