One part of these indexes belong to stable blood constants (pH - blood has weakly alkaline reaction, its pH is equal to 7,35 in veins and 7,4 in arteries; osmotic tissues - 7,3 atm; oncotic pressure - 0,03-0,04 atm); others - to unstable (blood viscosity - relative is 4,5; VSR: in men- 6- 12 mni/h; in women- 8-15 mm/h) et al. Blood system is one of the most sensitive organism indicators which reflects organism state. Constants fluctuation may serve as diagnostic critérium of many diseases (sometimes - earlier than clinical critériums or more exact then clinical indexes). Many blood constants are suffered at blood diseases. One can use unstable constants in laboratory and clinical practice more oftan than unstable ones. Especially it concer...