2g2 AYERS. [Vol. VI. 



ganglion cells and the long (relatively) stretch of nerve fibre 

 between the ganglion and the brain nuclei, are, of course, still 

 unknown to us. 



Enough has been said, I think, to show that the processes of 

 selection and of propagation of undulations of different wave 

 lengths is an extremely difficult one to follow out in all its detail, 

 and that, although we have gained some new insight into the 

 methods of cell action, the field is practically untouched experi- 

 mentally and lies before the modern advanced physiologist, an 

 inviting and very promising field for research in neuro-sensory 

 physiology, holding, in fact, the same place in physiology of 

 neuro-sensory processes that the nerve and striated muscle 

 preparations do to neuro-motor physiology, — all of this because 

 of the easily (relatively) controllable physical basis of the sen- 

 sory processes ; the physical basis of smell and sight being so 

 much more difficult of measurement as to practically exclude 

 the acquisition of quantitative results from experimental research 

 in their fields. 



From the physical constitution of the cochlea and from the 

 experiments on the hair band it follows that the action of un- 

 dulatory stimuli in the cochlea leads to very different results 

 from those taught by the Hensen-Helmholtz school (p. 263 

 et seg.). It is certain that only those wave motions are effective 

 in the stimulation of the nerve end organ which succeed in pass- 

 ing all barriers and enter and are propagated in the cochlear 

 canal as discrete wave motions of the endolymph, causing un- 

 dulations of all the auditory hairs. Any sounding body which 

 gives forth a simple tone as a fundamental accompanied by other 

 simple tones, as overtones, etc., must produce for each tone 

 propagated through the ear to the brain, a discrete series of un- 

 dulation, which of its own energy stimulates the hairs of the 

 cochlea, and all of them in greater or less degree. It does so 

 in its period entirely independent of the other tones in process 

 of propagation down the cochlear apparatus. A musical or 

 tonal effect produced as Helmholtz conceived in his " compound 

 wave," requiring an analysis by the hair band, does not occur 

 in nature, unless the term "compound wave" is used to desig- 

 nate a group of discrete stresses, any one of which might go 

 on and produce its effect, though all the rest were annihilated. 

 If this is the interpretation of the term, the use of the word 



