34 



The following experiments refer to the influence of the varying 

 plane of the bones forming the chain, and of its articulations, on the 

 progress of sonorous undulations through it : 



I. Experiments illustrative of the influence of the variety of planes 

 in the chain. 



Experiment 1 . Three pieces of wood, each 5 inches in length 



and half an inch thick, were glued together thus /\ , so as to 



represent the planes in which the malleus, incus, and stapes are 

 arranged in the chain of ossicles, while three similar portions were 

 glued end to end so as to form a straight rod. A watch was placed 

 in contact with one end of the straight rod, while the other was 

 pressed gently against the tragus so as to shut the external meatus. 

 The result was that the watch was heard nearly as distinctly as 

 when in contact with the ear. When a similar experiment was per- 

 formed with the angular portion of wood representing the chain of 

 bones, the watch was also heard, but less distinctly than through the 

 straight portion. 



Experiment 2. A tuning-fork C', being made to vibrate, was 

 placed in contact with one extremity of the angular piece of wood, 

 the other being placed against the tragus of the ear ; and as soon as 

 the sound ceased to be heard, the straight portion was substituted, 

 when the tuning-fork was again heard, and it continued to be heard 

 for about three seconds. 



Experiment 3. A vibrating tuning-fork C' was placed at one ex- 

 tremity of the angular piece of wood, the other extremity being held 

 between the teeth ; the fork was at first heard very distinctly, and 

 when its sound could no longer be distinguished, the straight piece 

 was substituted, and it was again heard for the space of two 

 seconds. 



Experiment 4. Instead of the horizontal portion of wood repre- 

 senting the stapes, three portions of the same size were made into 

 a triangle, and this was glued to the anterior surface of the inferior 



extremity of the piece representing the incus, thus A^ The 



previous experiment was then repeated with the substitution of this 

 apparatus for the angular one, and with nearly the same result, viz. 

 the fork was heard through the straight piece about three seconds 



