The origin of the ERG and the significance of the individual waves are still a subject of much discussion. Various conflicting opinions still exist, although important progress has been made in recent years in the approach to a solution. Clinical electroretinography has greatly contributed to this progress. Retinitis pigmentosa may serve as an example. In this disease the ERG may be absent even in a very early stage, when visual acuity and visual field are still reasonably intact, although in some cases it is possible to demonstrate electrical activity of the retina with the aid of a light stimulus of very high intensity (Goodman).1
In such cases a sufficient number of sensory cells would appear to be still functioning, but the electrical activity is markedly diminished. In view of these facts, there will be some hesitance in ascribing the ERG exclusively to the layer of sensory cells. There are