[Classification of the abnormality concept]

This paper deals with congenital malformations in man and presents a classificatory system for them. It first distinguishes abnormalities from normal variation and then further separates between primary and secondary structural disorders. Secondary disorders are those which are due to disturbances in primary normal tissues. Every maldevelopment which originates in prenatal life, is a congenital malformation. The level at which the malformation occurs must be considered, i. e. whether it is at the organism level, organ level, tissue, cell or subcellular level. A standardized system is absolutely necessary if the incidence of malformations is to be compared throughout the world.