singing, is of cerebral origin, and controlled by centres on the opposite side of the brain, the impulses being sent down to the respective centres for the associated movements of the muscles of articulation, phonation, and breathing, in the same way as they are sent to the centres for the movements of the arm or leg.  With voluntary breathing the respiratory centre in the medulla has nothing to do.  It is in fact out of gear or inhibited for the time being, so that the impulses from the brain pass by or evade it.  There are thus two sets of respiratory nerve fibres passing from the brain—­the one inhibiting or controlling to the opposite half of the respiratory centre in the medulla; the other direct, evading the respiratory centre and running the same course to the spinal centres for the respiratory movements as the ordinary motor fibres do to the centres for other movements.  Both sets would be affected by the lesion (or damage) which produced the hemiplegia.  The inhibitory fibres being damaged, the opposite half of the respiratory centre would be under diminished control and therefore the movements of ordinary breathing on the paralysed side 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