[Electrophysiological studies on the spectral sensitivity of the photoreceptors of the frog retina].

A new method for potential measurements is proposed to study the spectral sensitivity of more than two different types of photoreceptors by means of the mass receptor potential of the isolated retina. The studies were carried out on retinas of animals belonging to the European waterfrog group: Rana ridibunda, R. lessonae and R. esculenta. We were able to demonstrate two different spectral types of rods and two different types of cone responses in each retina. In connection with morphological findings the european waterfrogs are suggested to possess the same types of photoreceptors as Rana pipiens. The question is discussed whether the different types of both rods and cones show different thresholds.