Internal and external vestibular caloric tests in pigeons. A nystagmographic study

The caloric test was conducted on pigeons in two different ways: 'external calorization', stimulation by irrigation of the external ear canal, and 'internal calorization', stimulation through a coil winded around one horizontal semicircular canal. Different temperatures and amounts of irrigation water were tried out to obtain caloric responses. Internal calorization proved to be more effective than external calorization in a wide range of temperature levels. The experiments proved that a kind of modifying effect of the external ear canal sensory innervation exists on the vestibular caloric test.