1). The Second Level Of Regulation - -

1). The second level of regulation - - is created by hormones. Hormones - the special substances developed in glands; arriving in blood, they influence activity of cages sensitive to them. Action of hormones, for example, such glands as adrenal glands and parathyroid glands, first of all it is directed on performance of the law of a constancy of the internal environment. If to recollect that initially the life has arisen in the water environment should admire that the structure and concentration of the salts (ions) washing a cage, almost precisely correspond to the salt environment of the World ocean in the period when in the course of evolution the structure of a modern cage was created. During millions and millions years the structure of cages remains to constants, despite their so difficult transformations to specialised fabrics and bodies during the further evolution of wildlife. Concentration in the calcium and phosphorus blood, supervised mainly parathyroid glands, concentration of sodium and , supervised mainly adrenal glands, is strictly protected during all life of an individual.