  Biology is considered here as an "emergent science" in the sense of Anderson
and of Laughlin and Pines. It is demonstrated that a straightforward
mathematical definition of "biological system" is useful in showing how biology
differs in structure from the lower levels in Anderson's "More is Different"
hierarchy. Using cells in a chemostat as a paradigmatic exemplar of a
biological system, it is found that a coherent collection of metabolic pathways
through a single cell in the chemostat also satisfies the proposed definition
of a biological system. This provides a theoretical and mathematical
underpinning for Young's fundamental model of biological organization and
integration. Evidence for the therapeutic efficacy of Young's method of
analysis is provided by preliminary results of clinical trials of a specific
application of Young's model to the treatment of cancer cachexia.
