35 



after it had ceased to be heard by the apparatus representing the 

 chain of bones. 



Experiment 5. A piece of very thin paper was gummed over the 

 end of a glass tube 6 inches in diameter ; to the outer surface of 

 this paper was glued a model of the chain of ossicles similar to the 

 one used in the previous experiment ; a vibrating tuning-fork C' 

 being placed in the interior of the tube and within a quarter of an 

 inch of the paper, the sound was heard through the free end of the 

 chain placed between the teeth for ten seconds ; when the sound 

 ceased to be heard, a straight piece of wood was substituted, and the 

 sound was not heard through it. 



II. Experiments illustrative of the influence of the articulations 

 in the chain. 



Experiment 1. Three pieces of wood, each about 5 inches 

 long and half an inch in thickness, were separated from each other 

 by pieces of india-rubber as thick as ordinary writing-paper, and they 

 were then fastened together so as to assume the angular form pos- 

 sessed by the chain of ossicles. The tuning-fork C' being placed at the 

 free extremity of the chain, the other extremity being held between 

 the teeth, it was found that the sound was heard as distinctly and 

 for the same length of time, as when it passed through the chain 

 formed of three portions glued together. 



Experiment 2. When eight layers of the india-rubber were placed 

 between each piece of wood, there was still very little difference in 

 the intensity of the sound from that observed when it passed through 

 the portions glued together. 



Experiment 3. One, two, or three fingers having been placed 

 between the first and second pieces of wood, and eight layers of 

 india-rubber between the second and third, a very slight diminution 

 in the intensity and duration of the sound was observed as compared 

 with its passage through similar pieces when glued together. 



Experiment 4. The back of the hand was placed in contact with 

 the teeth, and the end of the vibrating fork C' was pressed against 

 the palm ; the sound was heard very distinctly for several seconds ; 

 and when it ceased to be heard, a piece of solid wood 3 inches 

 long was substituted, through which the sound of the fork was again 

 heard faintly for four seconds. 



The inference from the two series of experiments above detailed is, 



D2 



