Abstract
This chapter will summarise the role of some functionally active intestinal microbes acting on man and animal on some anatomical, physiological and biochemical functions. The influences on immunological functions will be presented separately. The baselines for these functions refer to studies performed in material from germfree animals and healthy newborns, and values obtained are compared to functions in a macro-organism which have been in affected by a micro-flora. In principle, these functions are similar in all the organisms so far investigated, only the levels vary, due to age, and different dietary components and environmental factors. Alterations of the normal pattern of these functions mainly reflects altered ecological conditions in the organism and the reasons for these are sometimes known-sometimes unknown. The consequences after alterations of these functions have to be investigated in several ways, i.e., both with regard to local and distal effects on the host organism.