Consequently he summarizes his reflexions on coloured afterimages and their reversals of colour in these words: 'The eye demands actual completeness and closes the colour-circle in itself.' How true this is, the law connecting the corresponding colours shows, as may be seen in the following diagram. Here, red, yellow and blue as three primary colours confront the three remaining colours, green, violet and orange in such a way that each of the latter represents a mixture of the two other primary colours. (Fig. 10.) Colour and contrast-colour are actually so related that to whatever colour the eye is exposed it produces a counter-colour so as to have the sum-total of all the three primary colours in itself. And so, in consequence of the interplay of outer and inner light in the eye, there is always present in it the totality of all the colours. It follows that the appearance of the contrast-colour in the field of vision is not, as the Newtonian theory asserts, the result of fatigue, but of an intensified activity of the eye, which continues even after the colour impression which gave rise to it has ceased. What is seen on the neutral surface (it will be shown later why we studiously avoid speaking of 'white light') is no outwardly existing colour at all. It is the activity of the eye itself, working in a dreamlike way from its blood-vessel system, and coming to our consciousness by this means. Here again, just as in the simple opposition of light and dark, the perception of coloured after-images is connected with a breaking-down process in the nerve region of the eye, and a corresponding building-up activity coming from the blood. Only in this case the eye is not affected by simple light, but by light of a definite colouring. The specific destructive process caused by this light is answered with a specific building-up process by the blood. Under certain conditions we can become dreamily aware of this process which normally does not enter our consciousness. In such a case we see the contrasting colour as coloured after-image. Only by representing the process in this way do we do justice to a fact which completely eludes the onlooker-consciousness - namely, that the eye produces the contrasting colour even while it is still exposed to the influence of the outer colour. Since this is so, all colours appearing to us in ordinary vision are already tinged by the subdued light of the opposite colour, produced by the eye itself. One can easily convince oneself of this through the following experiment. Instead of directing the eye, after it has been exposed to a certain colour, to a neutral surface, as previously, gaze at the appropriate contrasting colour. (The first and second coloured surfaces should be so arranged that the former is considerably smaller than the latter.) Then, in the middle of the second surface (and in a field about the size of the first), its own colour appears, with a strikingly heightened intensity.