We present two types of Generalized Green Functions (GGFs) which became standard GFs in a limit process. This approach is extremely suitable for the study of biological systems. We derive the basic relations for GGFs and apply the method of GGFs to a system of harmonic boson excitations and to the electron gas. We demonstrate that the correlation of the past and the future has, as a consequence, quasi-periodic behaviour of the entropy of both systems and strong dissipation of the energy. We give a number of illustrative examples.