No. I.] THE VERTEBRATE EAR. 191 



be reabsorbed, to fade away entirely as organs, soon after, 

 leaving only the faintest traces of their previous strength and 

 perfection of development ; for, strange as it may seem, the 

 apparently physically strongest organ is the one which disap- 

 pears, leaving the smaller organ, which at the same time seems 

 to have acquired a higher degree of cell differentiation, to occupy 

 the field alone. The story of the " Rise and Fall " of organs, 

 of cell communities, is repeated within the cochlea, nor is it by 

 any means all told yet. The organ of Corti, as it exists to-day 

 in the higher Mammalia and in Man, is in a state of flux ; and 

 although change in any direction is undoubtedly very slow, yet 

 there is a tendency to increase in size and complexity very 

 manifest in this structure. The present organ has a future 

 before it ; but annihilation will remove it out of the way for the 

 better adapted successor among the future mammalian descend- 

 ants, just as the sauropsid organ has disappeared before the 

 present mammalian organ of Corti. 



It took a long time and much study for the older investigators 

 to arrive at correct conceptions of the relations of the cellular 

 elements of the organ of Corti to the floor on which it rests, 

 even in the adult ear. The Marquis Corti had only the faintest 

 conception of the actual condition of the cellular elements in 

 the organ discovered by him, and none, of the significance 

 of the morphological relations of this cochlear organ to other 

 parts of the ear. His original view was that the cells forming 

 the organ followed one another in an even layer, much as in 

 any layer of columnar epithelium. They were thus spread out 

 evenly, he thought, on the basilar membrane, and this concep- 

 tion of the relation of the parts in the adult affected powerfully 

 the ideas of its course of development. 



Claudius (1855, 53) first saw that the arches of Corti raised 

 the mass of the organ of Corti above the basilar membrane. 



Boettcher (1856, 29) and Deiters (1859, 66), who worked 

 little with cross-sections, thought the cells of Claudius followed 

 directly on the hair cells without a break in the surface. 



The structure called papilla spiralis by Huschke (1835, 148), 

 and Organon Kollikeri by Hensen (1864, 127), formed that part 

 of the epithelial thickening of the floor of the cochlear tube in 

 which the whole of the auditory nerve was supposed by these 

 earlier investigators to end. In this epithelial ridge, or papilla 



