26o AYERS. [Vol. VI. 



ich aiich nicht glaube, dass das Verhaltniss derselben zum Ner- 

 venepithel und zu den Horhaaren desselben ein anderes, als bei 

 den iibrigen Vertebraten, so bedarf dieser Punkt doch noch 

 weiterer Untersuchungen." 



In stating Helmholtz's view, let us begin with an account of 

 what takes place when the stapes is forced into the oval window. 

 According to his generally accepted views, when the tympanum 

 is vibrating under the influence of aerial undulations, the stapes, 

 owing to its mechanical connection with that membrane, exe- 

 cutes to-and-fro movements which transfer the tympanic vibra- 

 tions to the perilymph, in the form of delicate blows delivered 

 against the surface of the fluid by the foot of the stapes. The 

 fluid in the perilymphatic spaces, being bounded by bony walls, 

 has only one means of escape, — the round window with its 

 yielding membrane. 



To reach it, the fluid of the labyrinth must either pass through 

 the helicotrema, flowing over from tlie scala vestibuli into the 

 scala tympani, or, as it would probably not have time to do so 

 in the case of sonorous vibrations, press the membranous parti- 

 tion of the cochlea against the scala tympani. The converse 

 action must take place when the air in the auditory passage is 

 rarefied. 



" When 1 the pressure of the fluid in the scala tympani is 

 increased by driving the foot of the stirrup against the oval 

 window, the membrane at the base of the arches (of Corti) will 

 sink downwards {i.e. the membrana basilaris), the fibres of the 

 second series of Corti's arches be more tightly stretched, and 

 perhaps the corresponding places of the fibres of the first series 

 be bent a little downwards. It does not, however, seem prob- 

 able that the fibres of the first series themselves move to any 

 great extent, for their lateral connections are strong enough to 

 make them hang together in masses, like a membrane, when 

 they have been released from their attachment in anatomical 

 preparations. On reviewing the whole arrangement, there can 

 be no doubt that Corti's organ is an apparatus adapted for 

 receiving the vibrations of the membrana basilaris, and for 

 vibrating of itself ; but our present knowledge is not sufficient 

 to determine with accuracy the manner in which these vibra- 

 tions take place. 



1 Helmholtz, ed. 1S77, or Eng. ed. 1S85. 



