[Quantification of environmentally influenced differences in physical and mental development of infants by a phenomenologic-mathematical separation of the body length growth into growth spurts (author's transl)].

Retardation phenomena in the physical development--especially in the increase of body length--of infants taken care of in social institutions (day-nursery, week-nursery, residential nursery) in relation to those growing up in the family will be represented in a quantitative-analytical form on the basis of a phenomenologic-mathematical model. This kind of modelling consists in the separation into 7 successive growth periods (growth spurts) of the whole growth process during the time interval from conception until the age of 3 years. For the time interval from birth until the end of 3 years we have 4 such growth spurts. The second one (fifth in the former numbering) determines mainly the growth during the 2nd year of the individual's life and makes evident the delay in the mean increase of body length of infants taken care of in social institutions, which is most evident for children who grow up in a residential nursery. The quantitative statements derived from the mathematical model concerning the physical development will be confronted with the known facts concerning the retardation in the mental-psychial development--especially in the ontogenesis of speech--of the same groups of children. There is an astonishingly close accordance of the values of time delays in reaching the levels of the physical and of the psychical development. The model may help to perceive and to diagnose the complex of causes responsible for these retardation phenomena from a social-medical and biological point of view. On the other hand this may also give a critizism and assessment of the real relevance of the biomathematical separation of the growth process into single growth spurts practiced here.