In inhalation tests involving lethal as well as sublethal doses of dias examined in rabbits by means ofhistologic and neurofunctional methods. Histologic examination revealed chromatolysis, disintegration of Nissl bodies, and cell shrinkage in proportion to the doses employed in the nuclei of the unpaired brain stem, in the sensory cortical regions and especially in the sensory cranial nerve nuclei. The sensory trigeminal nucleus was involved most severely, followed in decreasing intensity 0y the facial and oculomotor nerves and the motor trigeminal nucleus; the least changes were observed in the acoustic nerve. By testing the protopathic sensitivity of the facial skin it was possible for the first time to produce evidence of a sensory loss in the distribution of the trigeminal nerve by animal experimentation. The neuropathological and functional deficits observed may explain the cranial nerve lesions in human DCA intoxication; however, these lesions seem to be less distinct in experimental animals.