The autonomic innervation of the nasal blood vessels of the cat.

1. A study has been made in the anaesthetized cat of the stimulation parameters required to separate the vasodilator and vasoconstrictor responses evoked in the nose by stimulating the cut peripheral end of the Vidian nerve.2. The extent of the vasodilation and vasoconstriction was found to be dependent on the stimulation frequency, but whereas vasodilation reached a maximum at 25 Hz, vasoconstriction occurred at lower frequencies and was maximum between 10 and 15 Hz.3. Atropine, in a dose much greater than that which inhibits nasal secretion, did not abolish the vasodilator responses evoked by Vidian nerve stimulation. This suggests that the Vidian nerve may convey atropine resistant fibres to the nasal vasculature.