Abstract.-The auditory sensitivity of 4 specimens of the bullhead catfish (Ictalurus nebulosis) was determined by shock-avoidance training in an aquatic shuttle box. The range of hearing extended from 100 to 4000 cycles per second, with the maximum sensitivity around 600 to 700 cycles per second.Previous work by Stetter1 indicated that bullhead catfish, then called Ameiurus nebulosus, had a hearing range extending to 13,139 cycles per second (Hz). Poggendorf2 also tested the auditory range of a single specimen of bullhead catfish but did not find sensitivity beyond the 5000 Hz limit commonly reported in the general literature for fishes. Because the structure of the fish ear, which involves macular organs weighted with large otoliths, does not appear to be suitable for high frequency response,3 the auditory range of the bullhead catfish needs careful reassessment.Procedure. The unconditioned shock stimulus was provided by the 110 v a-c line stepped down through an isolation transformer and a variable autotransformer and switch-operated to give 0-24 v a-c pulses between wire-grid electrodes on the sides of the tank. The shock level was found to be most effective at 5 v a-c.The intertrial interval, the trial duration, and conditioned-unconditioned stimulus interval were monitored by two Standard Electric Time Company model S-1 clocks. A Digital Electronics Company Digiac 3010 computer controlled the intertrial interval, the conditioned-unconditioned stimulus interval, and the presentation or termination of both the tonal and shock stimuli. The computer was programmed to vary the intertrial interval between 47-, 60-, and 73-second periods to 1)r'Vellt, time conditioning. Six Clairex type CL707 HI, photocells, placed in a vertical array three on each side of the barrier opposite 12 v bulbs, detected the movement of the subject across the barrier and provided the d-c pulse required to trigger the computer. The lamps and photocells were powered by three Electro Products model EC-2 power supplies.

No abstract

Several studies have been concerned with hearing in the amphibia. However, at present, no clear statement can be made regarding either the effective frequency range or the sensitivity of the amphibian ear.

This paper is a continuation of studies initiated over two years ago in this laboratory for the purpose of assessing the effects of local anesthetics used topically in otological surgery."! The favorable conditions accompanying the use of topical anesthesia have been discussed there. However, our studies have shown that some of the commonly used anesthetics cause serious disruptions in the action of the cochlea's sensory mechanism when these drugs are applied to middle ear structures. The major effect involves a reduction in the magnitude of the electrical response of the cochlea. These losses have serious implications for hearing. It is clear that the choice of anesthesia for otological surgery is an important matter, and one that demands further systematic study.The purpose of our present research was to determine the effects of lidocaine hydrochloride (Xylocaine® 2, 1, and Y2 per cent solutions with and without 1: 100,000 epinephrine) upon the electrical response of the cochlea of the cat. Also considered was the effect of 1: 100,000 epinephrine alone upon this response. The effects of 10 per cent cocaine hydrochloride and of normal saline are included for comparison. PROCEDURE Twenty-eight cats were used as experimental animals, and each was anesthetized with a solution of diallyl-barbituric acid and ethyl