vin THE FUNCTIOXS OF THE OSSICLES 381 



a deaf man in the same position would be aware of 

 nothing but the visible oscillation of the beam as a 

 whole. 



Thus, to return to the chain of auditor}' ossicles, while 

 it may be supposed that, when the membrane of the 

 drum vibrates, these may be set vibrating both as a 

 whole and in their particles, the question arises whether 

 it is the large vibrations, or the minute ones, which make 

 themselves obvious to the auditory nerve which is in the 

 position of our deaf, or blind, man. 



The evidence is distinctly in favour of the conclusion, 

 that it is the vibrations of the bones, as a whole, which 

 are the chief agents in transmitting the impulses of the 

 aerial waves. 



For, in the first place, the disposition of the bones and 

 the mode of their articulation are very much against the 

 transmission of molecular vibrations through their sub- 

 stance, but, on the other hand, are extremely favourable 

 to their vibration en viasse. The long processes of the 

 malleus and incus swing, like a pendulum, upon the axis 

 furnished by the short processes of these bones ; while 

 the mode of connection of the incus with the stapes, and 

 of the latter with the membrane of the fenestra ovalis, 

 allows the foot-plate of that bone free play, inwards and 

 outwards. In the second place, the total length of the 

 chain of ossicles is very small compared with the length 

 of the waves of audible sounds, and physical considera- 

 tions teach us that in a like thin rod, similarly capable 

 of swinging en masse, the minute molecular vibrations 

 would be inappreciable. Thirdly, direct experiments, 

 such as attaching to the stapes of a dissected ear a 

 light style, the movements of which are recorded on a 

 travelling smoked glass plate or in some other way, 

 show that the chain of ossicles does actually vibrate 

 as a whole, and at the same rate as the membrane 

 of the drum, when aerial vibrations strike upon the 

 latter. 



