Il8 AVERS. [Vol. VI. 



most writers, has estimated the number of hair cells in the 

 cochlear organ of man and other mammals. His figures, given 

 in round numbers, are the following : — 



The inner hair-cell row contains in man 3) 500 cells. 



" " " " " " " cat 2,600 



" " " " " " " rabbit 1,600 



The 4 outer hair-cell rows contain in man 12,000 



"3 " " " " " " cat 9,900 



"4 " " " " " " rabbit 6,200 



As I have shown above, each hair cell bears a number of 

 hairs which make up its bundle of percipient elements ; and 

 from the estimates which I have made up to the present time 

 on the several species of domestic mammals mentioned before, 

 the average number of hairs borne by the cells is twenty-five. 



The inner hair-cell row in man would consequently 



support 85,000 auditory hairs. 



The 4 outer hair-cell rows in man would consequently 



support 300,000 " " 



According to Retzius's estimate, there are about 24,000 fibres 

 in the tympanic layer of the basilar membrane in man's ear, 

 while the cat possesses 15,700, and the rabbit 10,500. 



These fibres were, according to the generally accepted Hen- 

 sen-Helmholtz basilar membrane theory, the percipient ele- 

 ments par excellence ; for on them, fixed as they are at both 

 ends and supposedly tensely drawn, depended the transmission 

 of the undulations of the endolymph to the hair cells. In place 

 of these fibres of the basilar membrane I would substitute the 

 385,000 percipient capillary processes floating freely in the 

 endolymph and connected directly with the sensory cell trans- 

 mission apparatus, about which as yet we know so little, as the 

 parts of Corti's organ which are sympathetically affected by 

 sonorous waves entering the ear. 



It is evident that the apparatus, which I have thus inade- 

 quately described, is far superior from a physical standpoint to 

 the system of basilar membrane fibres for the work of picking 

 up minute undulations, and the sequence of the physiological 

 steps, which all our knowledge of sensory apparatuses lead us to 

 accept as the normal condition, is maintained by this apparatus 

 if it works as all investigators who have studied on the parent 

 organs — the lateral line organs of fishes — suppose it does, 



