1. (Physiol.) In the broadest sense, a process or series of processes
by which the living organism as a whole (or its component parts or
organs) is maintained in its normal condition of life and growth.
In this wide sense it comprehends digestion, absorption, circulation,
assimilation, etc., in fact all of the steps by which the nutritive
matter of the food is fitted for incorporation with the different
tissues, and the changes which it undergoes after its assimilation,
prior to its excretion. See Metabolism.
2. (Physiol.) In a more limited sense, the process by which the living
tissues take up, from the blood, matters necessary either for their
repair or for the performance of their healthy functions.