Fig. 6-2. Dorsal view of brain stem and cerebral hemispheres. Eyes are also seen from behind, as if reader is looking through eyes from the intracranial position. Loss of right vestibular influence releases the left vestibular apparatus to unopposed tonic driving of eyes to the right through neuronal apparatus illustrated by solid lines. Opposing phasic impulses that constitute the fast or checking component of nystagmus and arise from the right hemisphere are illustrated by broken lines.