[Functional origin of the respiratory system in ontogeny. II. The biological importance of the act of birth and the start of extrauterine respiration].

The programme preparation of the fetus for extrauterine autonomic development in the air medium is completed during the process of natural generic act. The postnatal apnea appears to be the result of the fetus central nervous system depressive state. This depression originates in prenatal period and continues during the delivery. The so-called first breath occurs as a results of overcoming of the depressive influences action and the renewal of automatic activity of the respiratory center which has been temporarily switched off.