No. I.] THE VERTEBRATE EAR. 



257 



ear executes an ajtditory function, as regards essentials, in the 

 same manner as its prototype the lateral line sense organ, and tJiere 

 exist betiveen the auditory sense organs differences only in degree, 

 not in kind, of the function subserved. 



Likewise, the perilymphatic parts of the ear are not essential 

 to the correct understanding of the auditory processes ; they 

 are simply the enlarged lymphatic spaces always developed 

 below and around these sense organs, from the lateral line con- 

 dition increasingly up to the mammalian ear. 



In 1838 Duges arrived at conclusions with respect to the 

 functions of the parts of the internal ear which were later 

 accepted by Helmholtz. According to this view the utriculo- 

 saccular chambers subserved the functions of perceiving noises 

 and measuring the mtensities of all auditory stimuli, while the 

 cochlea alone was capable of the perception of tone and its 

 timbre. 



Carl Hasse (1873, 118) concludes his comparative studies on 

 the vertebrate ear with a summary of his physiological ideas in 

 these words {loc. cit. p. 95) : "Thus we find also in mammals 

 and in man masses which cover the macula (Corti's organ), into 

 which the hairs of the hair cells freely penetrate, whose inner- 

 most layer, the membrana reticularis, adheres firmly to the cells 

 of Corti, and consequently must follow the movements of the 

 basilar membrane. 



" Should such a fibre of the membrana basilaris be thrown into 

 vibration by the proper tone, in reptiles and birds, all of the 

 isolation and hair cells lying on the fibre would move with it. 



"They with the hairs would be moved against the membrana 

 tectoria, whereby the stimulation of the nerve fibre which pro- 

 jects into the hair would be caused. The same is true of mam- 

 mals and man, but in a more complete degree. The motion 

 is propagated through modified isolation cells, attached to the 

 fibre, which form an elastic arch, up to the auditory cells with 

 the hairs and the membrana reticularis which are moved against 

 the membrana tectoria. 



" Thus we find that motion of the superposed groups of isola- 

 tion and auditory cells is connected with the vibrations of the 

 single fibres of the basilar membrane, while the neighboring 

 ones do not participate, and by this means the vibration of such 

 a cord reaches consciousness in isolation ; it calls forth a special 



