33 



nearly total deafness ; and the following experiments, which demon- 

 strate the great facility with which sonorous undulations pass from 

 the air to a solid body, indicate that the stapes, even when isolated 

 from the other bones of the chain, may still be a medium for the 

 transmission of sound. 



Experiment 1. Both ears having been closed, a piece of wood, 

 5 inches long and half an inch in diameter, was held between the 

 teeth, and a vibrating tuning-fork C' having been brought within 

 the eighth of an inch of its free extremity, the sound was heard 

 distinctly, and it continued to be heard between five and six seconds. 



Experiment 2. One end of the piece of wood used in the pre- 

 vious experiment being pressed against the tragus of the outer ear, so 

 as to close the external meatus without compressing the air con- 

 tained within it, a vibrating tuning-fork C' placed within a quarter 

 of an inch of its free extremity, was heard very distinctly at first, 

 and it did not cease to be heard for fifteen seconds. 



Experiment 3. Three portions of wood, of the same length and 

 thickness as that used in the previous experiments, were glued 

 together so as to form a triangle somewhat of the shape of the 

 stapes ; the base of this triangle being placed against the outer 

 surface of the tragus, as in the previous experiment, the tuning-fork 

 C' vibrating within a quarter of an inch from its apex was heard for 

 twelve seconds. 



Considering, as shown by the above experiments, the great facility 

 with which sonorous undulations pass from the air to a solid body, it 

 may, I think, be assumed that the undulations in the tympanic cavity 

 may be conveyed to the stapes even when this bone is isolated from 

 the rest of the chain, and conducted by it to the vestibule ; and 

 when it is also considered that the absence of all the ossicles, or even 

 a fixed condition of the stapes, is productive of deafness, there is 

 strong evidence in favour of the opinion that sounds from the 

 external meatus cannot reach the labyrinth without the medium of 

 the ossicles. 



2. 7* there any peculiarity in the conformation of the chain of ossi- 

 cles which precludes the passage of sonorous undulations through it ? 



This question has also been answered in the affirmative, on account 

 of the various planes existing in the chain ; and secondly, on account of 

 the joints existing between the several bones composing this chain. 



VOL. X. D 



