Whether red light, or the exclusion of violet, exerts a beneficial influence on the hæmoglobin of the blood and on metabolism generally has not been distinctly proved, but it seems to me to be indicated by such experiments as those of Marti published a few years ago in the _Atti dei Lincei_. This investigator found that while feeble irritation of the skin promotes the formation of blood corpuscles, strong irritation diminishes the blood corpuscles and also the hæmoglobin; at the same time he found that darkness also diminishes the number of red corpuscles, while continued exposure to intense light (even at night the electric light, which, however, is rich in violet rays) favors increased formation of red corpuscles, and in some degree of hæmoglobin. Finsen has shown that inflammation of the skin caused by chemical or violet light leads to contraction of the red corpuscles. This brings us to the consideration of the influence of the red rays on the nervous system. From time to time experiments have been made as to the influence of various colored lights, chiefly on the insane, as first suggested by Father Secchi in 1895. Even yet, however, the specific mental influences of the various colors are not quite clear. It has been found by some that the red rays are far more soothing and comfortable, less irritating, than the total rays of uncolored light, and Garbini found that angry infants were soothed by the light through red glass, only slightly by that through green and not at all by other colored light. On the other hand, it is stated that a well-known dry plate manufacturer at Lyons was obliged to substitute green-colored glass in the windows of his large room for the usual red because the work people sang and gesticulated all day and the men made love to the women, while under the influence of green glass (which also allows yellow rays to pass) they became quiet and silent and seemed less fatigued when they left off work. We need not attach much value to these statements, but in this connection it is interesting to refer to the results obtained some years ago by Féré and recorded in his ‘Sensation et Mouvement.’ Experimenting on normal subjects as well as on nervous subjects, who were found more sensitive, with colored light passed through glass or sheets of gelatine, he found notable differences in muscular power, measured by the dynamometer, and in the circulation as measured by plethysmographic tracings of the forearm under the influence of different colors. He found in this manner with one subject whose normal muscular power was represented by 23 that blue light increased his power to 24, green to 28, yellow to 30, orange to 35 and red to 42. The dynamogenic powers of the different colors were thus found to rank in the spectral order, red representing the climax of energy, or, as Féré puts it, “the intensity of the visual sensation varies as the vibrations.” Féré found that colors need not