Phonoreception 



487 



absence of lateral line organ participation. Hoagland-- demonstrated that 

 the typical random discharge of spike potentials in lateral line organ nerves 

 of catfish is synchronized when stimulated with 100, 200, and 250 cycles per 

 second, but that the frequency of synchronization is not related to the fre- 

 quency of the sound waves except at low frequencies. 



It has been demonstrated with operative methods by von Frisch^'* that in 

 minnows the seat of hearing is definitely located in the sacculus and lagena, 

 which are sensitive to frequencies of 32 to 5000 or 6000 cycles, and the utri- 

 culus and labyrinth apparently have no auditory function. Low frequen- 

 cies (below 100-150 cycles) are perceived also by the touch receptors of the 

 skin, and very low frequencies (16 cycles) by the touch sense only, as shown: 



Lower limit 

 16-32 



Upper limit 

 5000-6000 



Sensitivity of sacculus 

 and lagena 



Tone C. C, C c c' c' c' c' c' CP 



Frequency 16 32 65 129 259 517 1035 2069 4138 8277 



Sensitivity 



of touch sense 



of skin 



Amphibia. In amphibia the lagena is slightly longer than in fishes (Figs. 

 164 and 165), but the principal new development is the middle ear, which is 

 found in the Salienta but not in the urodeles. In the frog, for instance, the 



posterior canal 

 endolymph duc^ 



brain 



anterior c>inal 

 lateral canal 



stapes 



sacculus 



Fig. 164. Diagrammatic presentation of the ear of Amblystoma, as seen 

 from the posterior. From Adams.' 



middle ear consists of an ear drum, an air cavity, and a bony rod, the col- 

 umella, which connects the drum with the inner ear. This is an adaptation 

 for transmitting the vibrations of air to the ear liquid, and therefore serves 

 the same function as the middle ear of man. 



Urodeles are commonly considered to be deaf. However, Ferhat-Akat^' 

 has demonstrated by means of training experiments that Amblystoma is able 

 to respond to frequencies as high as 194 to 244 cycles. Extirpation of the 

 labyrinth reduced this limit to 97-122 cycles. The lower limit of response 

 of the animal was not determined, but it was shown that the labyrinth did 



