Here we see that although the luminosity of the colour spots varies at the spectrum luminosity, the fields do not vary proportionally; when the luminosities of the green, yellow and red are made equal, the fields become nearly equal on the nasal side. The field for the blue, however, then becomes vastly larger than that for the others, showing a peculiarity which is very remarkable. [Illustration: FIG. 41. _Spectrum Scale._] Recently published experiments on colour fields have been so largely based on the exigencies of the Hering theory, that it is somewhat difficult to decide their significance from any other aspect. TABLE I.--LUMINOSITY CURVES FOR THE NORMAL EYE (see Fig. 20). -------+--------------+----------------+--------------+----------- I. | II. | III. | IV. | V. -------+--------------+----------------+--------------+----------- Scale | Wave-length. | Outside yellow | Yellow spot. | Fovea number.| | spot. | | centralis. -------+--------------+----------------+--------------+----------- 64 | 7217 | | | 63 | 7082 | .. | 1 | 62 | 6957 | 1 | 2 | 2 61 | 6839 | 2 | 4 | 4 60 | 6728 | 3·5 | 7 | 8 59 | 6621 | 7·5 | 12·5 | 15·5 58 | 6520 | 12·5 | 21 | 24 57 | 6423 | 19 | 33 | 37·5 56 | 6330 | 27·5 | 50 | 60 55 | 6242 | 35 | 65 | 77 54 | 6152 | 43 | 80 | 90 53 | 6074 | 52·5 | 90 | 97 52 | 5996 | 61·0 | 96 | 100 51 | 5919 | 71·0 | 99 | 100 50 | 5850 | 79·0 | 100 | 98 49 | 5783 | 84 | 99 | 95 48 | 5720 | 85 | 97 | 90 47 | 5658 | 83·5 | 92·5 | 85 46 | 5596 | 81·0 | 87 | 79 45 | 5538 | 77·0 | 81 | 72·5 44 | 5481 | 72.5 | 75 | 66 43 | 5427 | 68·0 | 69 | 59 42 | 5373 | 62·5 | 62·5 | 51 41 | 5321 | 57 | 57 | 45 40 | 5270 | 52 | 50 | 40 39 | 5221 | 46 | 42·5 | 32 38 | 5172 | 41·5 | 36 | 27·5 37 | 5128 | 37·5 | 29·5 | 22·0 36 | 5085 | 33·5 | 24 | 18 35 | 5043 | 30·0 | 18·2 | 14