116 PHYSIOLOGY CHAP. 



406), have shown that fishes are destitute of auditory sensations 

 (Bateson, Kreidl, Lee). According to the latest observations of 

 Parker and of Zenneck, some fresh - water fishes (Leuciscus, 

 Alburnus) are exceptions to this rule, because under certain 

 conditions they react to sound- vibrations. But it has not been 

 and cannot be shown that in these animals such reactions are 

 preceded by acoustic sensations, and not merely by sensations 

 of vibration. On the other hand, the fact that in the higher 

 vertebrates the destruction of the cochlea alone is sufficient to 

 produce total deafness shows that the vestibular organs are not 

 able to subserve any sensation of noise or sound. Nor is it prob- 

 able, as Breuer points out, that the maculae and crista are organs 

 of acoustic sensation, because the hairs of the sensory epithelia 

 are bound together by mucous matter which impedes their free 

 vibration. 



This excludes another early view put forward by Autenrieth 

 (1801), Kerner, and Duget, who supposed that the semi- 

 circular canals subserved perception of the direction of sounds. 

 This hypothesis was upheld later by Lussana, particularly from 

 the syndrome of Meniere's disease, which will be discussed 

 below. 



The founder of the modern theory of the functions of the 

 non-acoustic labyrinth was Flourens (1828), who found that after 

 lesions or excitation of the semicircular canals in pigeons and 

 mammals characteristic forced movements were obtained. After 

 section or removal of one semicircular canal he noted pendular or 

 nystagmic movements of the head, the direction of which depended 

 on the plane of the canal destroyed or removed (the horizontal 

 plane if the external canal were injured, one of the two vertical 

 planes if the upper or lower canal suffered). These phenomena 

 diminish and pass away after a certain time. But if the canals of 

 the opposite side are destroyed or removed, the pendular move- 

 ments reappear with greater intensity. They return spasmodic- 

 ally whenever the animal is in any way disturbed. The nystag- 

 mus of the head is associated with nystagmus of the eyes, often 

 with a tendency to fall or roll over, with vomiting, tachypnoea, 

 tachycardia, etc. The operated pigeon can no longer fly and has 

 difficulty in feeding itself and in walking. The greater the injury 

 to the vestibular organs, the more intense and persistent are the 

 motor disorders. But if the cochlea is spared there will be no 

 appreciable alteration of hearing, while if the cochlea is removed 

 without injuring the canals, deafness results in rabbits without 

 abnormal movements. 



Flourens first showed experimentally that the vestibular organs 

 are of no importance to hearing, while they are of supreme 

 significance in the complex movements of animals. The motor 

 phenomena which he described were universally confirmed, but 



