jQO AYERS. [Vol. VI. 



the canals begin to form. This process is true of all forms yet 

 studied with this matter in view.^ 



It is not my purpose to give at this time an exhaustive ac- 

 count of the development of the cochlea. All that I shall 

 attempt to do here will be to present in essentials the condi- 

 tion of our knowledge as established by the investigations of 

 Huschke, Remak, Reissner, Kolliker, Hensen, Middendorp, A. 

 Rosenberg, Gottstein, Pritchard, and Retzius, and to give a 

 short account of the few additional, but as I believe important, 

 facts which I am able to add to our previous fund of knowledge, 

 and to point out the modifications in the older views where 

 these new facts seem to necessitate fundamental change in our 

 conceptions of the pedigree of this organ and its present mor- 

 phological significance. 



The comparative ontogenetic history of this organ shows us 

 conclusively that the cochlea was not created after a cut-and- 

 dried plan, and having once been established among mammals 

 has gone on serenely ever since reproducing itself ; but, on the 

 contrary, embryological evidence shows that there has been a 

 struggle for existence among the parts of a growing organ, the 

 struggle ending in the annihilation of the unsuccessful candi- 

 dates for the privilege of existing. The antagonism began 

 quite as soon as the original differentiation of parts took place, 

 somewhere far back in the line of the sauropsid ancestral 

 stock, and has continued ever since in that group. In the 

 passage from Sauropsid to Mammal (the manner and the means 

 of the accomplishment of the change are as yet hidden from 

 us) there occurred a selection of the fittest (probably), which 

 gives us the mammalian organ of Corti of the adult ; but even 

 to-day the unsuccessful candidates are developed in the young 

 of Man as in all other mammals up to the functional perfection, 

 so far as we may judge on the basis of the stflicture, only to 



1 The earliest account of the ontogeny of the cochlea is given by Ibsen, according 

 to whose observations the cochlear canal is formed from the large otoHth sac by the 

 gradual recession of the otolith from the wall on which it lies {i.e. the inner wall 

 carrying the sense organ) . During its transition, it draws the wall of the chamber 

 along with it, and by contact with the other side or wall of the chamber divides the 

 tube into two scalae, while the triangular (in section) canal left between them be- 

 comes Corti's canal. The nerve supply runs across in the partition thus formed. 

 The otoliths have disappeared as such, having been converted into the lamina spiralis 

 accessoria. 



