would be exaggerated. The damage to the direct fibres would prevent the
passage of voluntary stimuli to the groups of respiratory muscles (as it
would do to the rest of the muscles of the paralysed side), and thus the
voluntary movement of respiration would be diminished--diminished only and
not completely abolished as in the limbs; because according to the theory
of Broadbent, in the case of such closely associated bilateral movements
the lower nervous respiratory centres of both sides would be activated from
either side of the brain." This certainly applies also to the muscles of
phonation, but not to the principal muscles of articulation, viz. the
tongue and lips. It is not exactly known what part of the cerebral cortex
controls the associated movements necessary for voluntary costal (rib)
respiration in singing; probably it is localised in the frontal lobe in
front of that part, stimulation of which gives rise to trunk movements
(_vide_ fig. 16). Whatever its situation, it must be connected by
association fibres with the centres of phonation and articulation.

[Illustration: FIG. 18]

[Description: FIG. 18.--The accompanying diagram is an attempt to explain
the course of innervation currents in phonation.

1. Represents the whole brain sending voluntary impulses _V_ to the regions
of the brain presiding over the mechanisms of voluntary breathing and
phonation. These two regions are associated in their action by fibres of
association _A_; moreover, the corresponding centres in the two halves of
the brain are unified in their action by association fibres _A'_ in the
great bridge connecting the two hemispheres (Corpus Callosum). On each side
of the centre for phonation are represented association fibres _H_ which
come from the centre of hearing; these fibres convey the guiding mental
images of sounds and determine exactly the liberation of innervation