[Comparative characteristics of deficiency and excess of the same trace element (as exemplified by nickel)]. / Sravnitel'naia kharakteristika odnoimennykh gipo- i gipermikroélementozov (na primere nikelezov).

General rules of biological effects of essential trace elements in human and animal body are discussed as illustrated by nickel model. Their action depends on the dose and duration of exposition. 5 levels of their action depending on the elements concentration in the body are distinguished. Pathology of low and high content of the same element in spite of the contrast of these conditions has certain similarity in the coincidence of the target organs and some pathological manifestations.