v THE SENSE OF HEAEING 261 



sensations and the subjective auditory sensations and hallucina- 

 tions. 



Entotic sensations are those which are caused, not by any 

 external, but by an internal stimulus, which excites the peripheral 

 auditory cells directly, or by transmission through the bones. 

 Such are the rumbling noises heard when the external meatus 

 is blocked by an accumulation of wax, or some foreign body, 

 or when the Eustachian tube is closed by catarrh. They are 

 explained by the fact that when the aerial transmission of tones 

 and noises is hindered or prevented, the ear is hypersensitive to 

 bone transmission, and perceives noises such as are caused by the 

 circulation of the blood through the ear, the beating of the arteries, 

 contraction of the muscles, and so on. 



Subjective acoustic sensations do not depend on actual 

 sound-vibrations, but on exaggerated excitability and the stimu- 

 lation of the peripheral auditory apparatus by unknown factors. 

 Some otologists distinguish these by the name of labyrinthine 

 acuphenes. In character they generally resemble ringing, rushing 

 or rustling, in which sometimes very high notes of the 3- and 

 4-times accented octave can be recognised, when the hyperaesthesia 

 of the auditory cells is not evenly diffused over the whole organ 

 of Corti, but more particularly involves special segments of it. 

 These phenomena are common in anaemic, neurasthenic, and 

 melancholic persons. 



These simple subjective sensations must be distinguished from 

 the persistent continuation and obstinate automatic and involun- 

 tary repetitions of notes, musical motifs, and verbal phrases, like 

 a distant echo of something heard, which has made a particular 

 impression on us. This often happens to people whose auditory 

 sensibility is especially acute, after they have been to the theatre. 

 These phenomena are essentially central in origin, and have the 

 significance of a spontaneous revival of auditory memory images. 



When the cerebral auditory images, which appear automatic- 

 ally, or perhaps in consequence of peripheral impulses which 

 normally arouse entotic sensations only, are so vivid and pro- 

 minent that they are projected outwards and confused with real 

 acoustic images, they become auditory hallucinations. These are 

 common in dreams, and their appearance in the waking state 

 is a conspicuous symptom of different forms of psychopathy. 

 According to their composition, auditory hallucinations are 

 distinguished as simple and complex. These last may be discon- 

 nected and chaotic, or they may have a definite character, e.g. 

 menacing or pleasant, and may be logically connected with 

 complex psychical delirium. From the psycho-physiological point 

 of view auditory hallucinations are of great importance as evidence 

 that there is nothing in common between the sonorous vibrations 

 of elastic bodies and the sensations of hearing, and that our 



