Determination of Ultramicroelectrode Tip Position in the Retina in Relation to S Potential

In a previous paper, this author presented histological evidences that the S potential originated in the secondary neuronal layer of the retina (Mitarai, 1958). This finding is in general agreement with the results obtained independently by other investigators (MacNichol, Macpherson, and Svaetichin, 1957; Tomita, Murakami , Sato, and Hashimoto, 1959; Oikawa, Ogawa, and Motokawa, 1959). The present paper gives more detailed information on the localization of the typical response. Due to the limitations of the histological methods so far used for the localization of the microelectrode tip in the retina, the accurate origin of the S potential has not yet been determined. The work to be described is a further at tempt to show the origin of the S potential by the use of an improved lithium carmine method developed by the author (Mitarai, 1958). In this paper a detailed description is given of this improved method and its limitations.