抄録
In the first half of the article it was reported that we succeeded to confirm the discoveries made by Motokawa concerning with the electrical excitability of the eye, e.g., the indirect induction, its propagation and the neutralization. The experiments consisted in determining under various conditions the threshold for the phosphene which was evoked by a single constant pulse of 0.1sec. given through the silver electrodes attached to the brow and cheek. A kind of the method of limits in the descending series was employed and special caution was taken against the possibility that expectation of the experimenter or of the subject influences the result.
The excitability of the eye, the reciprocal of the threshold, is enhanced if a flash of light is presented before the pulse is delivered and this enhancement is expressed by an index ζ. Then, the induction is an increase observed in ζ when the white light is preceeded by a colored light. The induction vanishes, however, if a flash of the complementary color intervenes between the two flashes, the colored and the white, and this is what is called the neutralization. The propagation of the induction is demonstrated by the fact that the neutralization is observed even when the complementary one is given to a part of the retina apart from the part where the colored one is presented.
A series of the experiments were designed to make a thorough inquiry into the nature of the coordinate system according to which the propagation of the induction takes its path and a part of the results was described in the second part. Two alternative hypotheses were proposed as shown in Fig. 5, where R denotes the one that the propagation takes place in accordance with the pattern of the retinal stimulation and P the other that configuration of the induction comes to form in accordance with what the subject perceives under the given conditions. Then it was demonstrated that there existed the case where the P-hypothesis holds. For instance, under the condition that fixation shifts from the left mark to the right one between the presentation of the figures III and IV of Fig. 4, the induction initiated by Y was observed with the point 1 and the induction initiated by B arrived to the point 2 to neutralize the induction evoked by Y. These are exactly what are expected from the P-hypothesis because the point 1 is seen above the place where Y is perceived in I and the point 2 below the place where B is perceived in II. If III is omitted and the fixation shifts between II and IV, however, the induction propagates in terms of the R-hypothesis. The results were obtained with all of the three subjects.
