136 UNIVERSITY OF MISSOURI STUDIES 



In birds one can hardly speak of some nerve ends being farther 

 away from the windows than others. 



It is of some interest, in this connection, to note that ani- 

 mals with a short tube, as the birds, do not possess in the par- 

 tition of the tube the pillars of Corti. They can get along 

 without these pillars. And naturally. The longer the tube, 

 the greater is the maximum pressure which may act upon the 

 partition near the windows, in case the bulging of the partition 

 is forced to proceed far towards the end of the tube. The 

 greater the possible pressure, the greater is, of course, the need 

 of a skeleton-like support in order to protect the sensitive cells 

 from collapsing. Thus the mammals need the pillars because 

 of the greater length of the tube. 



What must be the difference of sound perception resulting 

 from these anatomical differences in various species of ani- 

 mals? We saw that the human ear can 

 Comparative perceive several tones at the same time be- 



psychology of cause the linear extension of the auditory 



the sense of organ permits the compound mechanical 



hearing processes, transmitted from the stirrup to 



the fluid of the cochlea, to be analyzed into 

 much simpler mechanical processes taking place in successive 

 sections of the partition. It is plain, then, that in the auditory 

 pit of a frog no analysis is possible. The result must be that 

 the frog's ear can perceive only one tone at any moment ; and 

 this tone is most probably, as a rule, the highest cf the sev- 

 eral tones heard simultaneously under the same circumstances 

 by the human ear. 



The bird's ear, as we have seen, is intermediate between 

 the frog's ear and the human ear. But it does not seem very 

 probable that even birds can perceive very many tones simulta- 

 neously. The fact that birds sing is no indication to the con- 

 trary, since their song does not consist — like orchestral music 

 — of simultaneous, but only of successive tones. Of more sig- 

 nificance, in this respect, is the fact that some birds, for ex- 



