[Altitude adaptation. Part III. Altitude acclimatization as a problem of human biology (II. Morphology, physiology, biochemistry)].

The physiological mechanisms of adaptation will be reported. In a primary step of adaptation, the body reacts with immediate response, which already leads to a first classification: whether or not altitude will be tolerated by an individual. More steady biological processes follow with the same intention of balancing oxygen deficiency. They may be successful and acclimatization is possible, or they do not achieve the necessary level, i.e. that consequently developing pathological conditions of different severity lead to a next assortation of individuals with insufficient adaptability. The first state of lability can be compensated, or the intolerance will make a further stay in high altitudes impossible. No parameters exist which could allow a prognosis as to what kind of individuals will tolerate altitude or not. A different pattern of biological reaction is seen in permanent inhabitants of high altitudes who have been residing there for generations and haven't experienced conditions other than those of their special altitude in their individual lives. While ascending to higher altitudes, permanent residents also have to undergo new adaptation, as well as when descending to lower altitudes. Returning to their native environment requires reacclimatization. The mechanisms of adaptation on the organ level will be reviewed, as well as on the fluid and cellular level. All those functional and morphological mechanisms of adaptation to oxygen deficiency in high altitudes tend to maintain optimal equilibrium. Maladaptation may result. Expected genetically determined physiological alterations of adaptational value in permanent residents, which could have manifested themselves by way of "soft" selection and change of gene frequency in those high altitude populations, will be discussed. Genetical determination in such physiological parameters does not seem probable, although some pecularities such as the "blunted response" ventilation, the higher Bohr-Effect in Quenchua etc. might be interpreted in this direction.