9. _Currents seen in the field of vision not due to the circulation._--It occurred to me that if there were canals in the retina which promoted the easy flow of the visual purple into the fovea, we ought to obtain evidence of the currents flowing along these channels entoptically. I found that this was the case, and that the currents could be seen in numerous ways.[3] If one eye be partially covered with an opaque disc whilst both eyes are directed forwards in a not too brightly illuminated room, and special attention be paid to the covered eye, an appearance of whirling currents will be seen with this eye (see Fig. 1). These currents appear to be directed towards the centre, and have a very similar appearance to a whirlpool which is fed by four main branches. These again are fed by smaller branches which continually change their paths. On closing both eyes all the portion in which the whirling currents are seen appears as dull purple. These currents cannot be due to vessels, because we know that the centre of the retina corresponding to the point where the greatest movement is seen is free from vessels. The appearance is also very different from that of the movement of blood in vessels. The currents can also be seen in the light, in the dark, through yellow-green glass, and with intermittent light. The main branches form a star-shaped figure with four rays. The currents carry the visual quality, colour, and brightness from whence they come into an after-image. They also tend to move an after-image towards the centre. The currents behave as if they ran in definite channels, but could also overrun, on any further stimulus, the banks of the channels. For instance, a thin, bright line with a little more light appears as a broad band, and the central star figure will enlarge into a rhomboid, oval or disc. Movements of the eyes affect the broad currents in the outer part of the field of vision. [3] _Journal of Physiology_, vol. xli, p. 269. 10. _Pressure figure._--Pressure on the front of the eye causes the star-shaped figure to be seen, and this changes into a rhomboid with a little more pressure. 11. _Macular star._--It occurred to me that we ought to obtain evidence of the canals in the retina in cases where the outflow from the retina is obstructed, as by tumour. I find this is the case; the star-shaped figure given by Sir Victor Horsley in his paper on tumour of the frontal lobe[4] is almost exactly the same as that seen subjectively. [4] _British Medical Journal_, 1910, p. 556. [Illustration: Fig. 2.] 12. _Entoptic appearance of cone mosaic._--Appearances corresponding to the cone mosaic of the retina may be seen in several ways[5] (see Fig. 2). The appearance seen corresponds to the cone distribution of the retina as viewed from its outer side, the portions occupied by rods appearing as dark spaces. [5] _Journal of Physiology_, vol. xli, p. 226.