No. I.] THE VERTEBRATE EAR. 247 



symptoms appeared the membrane of the round window was 

 found ruptured and the liquid found in the subdural space, 

 about the brain, and especially abundant at the mouth of the 

 aquasductus cochleae in the jugular fossa. These results are in 

 harmony with those obtained by Brown-Sequard, Magendie, 

 Schiff, and Schwan, who, by direct mechanical stimulation of 

 that portion of the corpus restiforme lying on the fossa jugularis, 

 had previously produced similar motor disturbances. Giddiness 

 is then a result of irritation of the brain, complicated in these 

 experiments with an irritation of the ear channels. In order to 

 obtain a more precise answer to the problem, it was necessary to 

 find a method of irritating the ear channels alone with the com- 

 plete protection of the brain. By an easy operation on the 

 Dog, following Haidenhain's method, the position of the internal 

 ear may be exposed for operation by a removal of a piece of the 

 ventral wall of the tympanic bulla. According as this operation 

 is carried out, uni- or bi-laterally, is the animal made deaf in 

 one or both ears. The animals thus operated on never show 

 any trace of motor disturbances or of loss of the power of 

 equilibrium. 



If such an animal is killed some months after the operation, 

 the entire internal ear is found in an advanced state of fatty 

 degeneration. The sacculus and utriculus are frequently not 

 recognizable, while the cochlea is transformed into a cicatricial 

 tissue. If instead of destroying with the instrument only the 

 utriculo-sacculus and the canals, the cochlea as well is broken 

 up or removed, nystagmus and malposition of the head are the 

 immediate symptoms, and they are accompanied by deafness. 

 Post mortems of such cases always showed that in removing 

 the cochlea the porus acusticus internus was exposed or injured, 

 and by the rupture of the auditory nerve the cranial cavity was 

 opened ; consequently in this operation the cerebro-spinal fluid 

 must always escape. That in rupturing the auditory nerve the 

 brain tissue is injured is quite apparent. Whereas such lesions 

 are always followed by dizziness and equilibrative disturbances, 

 such disturbances do not appear when the cochlea is preserved, 

 and only the utriculo-saccular and canal end organs are destroyed 

 and resorbed by the healing of the wounds. Giddiness does 

 not result from the destruction of the auditory organs, but only 

 from lesions of the brain ; and since the semicircular canals can 



