. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 488 Cotnparative Animal Physiology not function below 32 cycles. The mechanoreceptors of the skin are ap- parently as important as the labyrinth. Ferhat-Akat also demonstrated that Amhlystoma is able to distinguish between frequencies that differ in pitch as much as a miisical interval of a fourth or a fifth (frequency ratios of 132 : 1 and : 1). In a few experiments on Salamander maculosa larvae he showed that the upper limit of reaction was 1035 cycles. Frogs are relatively unresponsive to sounds, but the
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 488 Cotnparative Animal Physiology not function below 32 cycles. The mechanoreceptors of the skin are ap- parently as important as the labyrinth. Ferhat-Akat also demonstrated that Amhlystoma is able to distinguish between frequencies that differ in pitch as much as a miisical interval of a fourth or a fifth (frequency ratios of 132 : 1 and : 1). In a few experiments on Salamander maculosa larvae he showed that the upper limit of reaction was 1035 cycles. Frogs are relatively unresponsive to sounds, but they may have an acute sense of hearing. Yerkes,"*' on the basis of a study of conditioned reflexes, reported that frogs can hear sounds between 50 and 10,000 cycles, but he did not obtain evidence of discrimination. Yerkes' frogs continued to respond endylymph duct posterior canal brain •. anterior canal inner ear lateral canal tympanic membrane annular ring middle ear Eustachian tube sacculus Fig. 165. Diagrammatic presentation of the ear of the frog, as seen from the posterior. From Adams.^ after removal of the ear drum and columella but not after cutting of the auditory nerves. Adrian, Craik, and Sturdy'* studied the microphonic effect in frogs and obtained responses between 50 and 300 cycles, with the maxi- mum sensitivity between 50 and 200. Ross""'^ in a study of single nerve fiber preparations observed a response to vibrations of about 100 cycles per second but did not investigate the extent of the range. Witschi''*^ demonstrated that during the early development of tadpoles the round window of the inner ear becomes connected with a bulge of the lung sac by means of a fibrous cord. This cord t)ecomes cartilaginous, pierces the dorsal aorta, and serves as an aortic columella which transmits vibrations to the inner ear. In this respect the aortic columella functions in the same way as the Weberian ossicles of fishes. The oval window serves as a pressure re-
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