When we consider the marvellous complexity of
structure of one of the higher animals, and the
amazing variety of its functions, the question
naturally arises, as to how all this is brought
about without any sort of clashing of the in-
terests of one part with those of another. Why
is it that the stomach has enough and not too much
blood? By what means has Nature solved the
problem of supplying more oxygen to parts in
action than to those at rest? How is it that one
set of muscles acts with instead of antagonizing
another set, as in any complicated series of move-
ments, such as walking?

To bring about this harmonization, or coordina-
tion, the nervous system has been provided. As
the nervous and muscular systems are of pre-
eminent importance in voice-production, they will
now be considered with more detail than it is
necessary to give to other systems.
