Crossed diplopia with a difference in height is distinguished with the aid of a red glass, the difference being corrected by a prism of 4°, with the base downwards before the right eye; a prism of 4° with the base inwards suffices to place the double images immediately above one another. Spontaneous diplopia does not take place; only the right visual field is seen in the stereoscope. As patient lived in Brandenburg and only came to consult me occasionally I never had an opportunity of seeing the squint till she decided to stay here for some time. It was then seen that a peculiar oscillating deviation of the left eye of about 4 mm. inwards often occurred. As the previous spontaneous disappearance of the squint and the crossed diplopia made one fear that tenotomy of the internus might be followed by divergence, instillations were used in order to make a more exact measurement of the deviation,--by this means the condition was so improved in the course of a few weeks, that deviation no longer occurred even on exclusion of the right eye. The spontaneous cure of squint may, however, be quite complete; indeed I have seen one case where convergent squint became divergent. CASE 40.--A young lady, slightly over twenty years of age, showed on the right M. ·75 D., V = 10/10, on the left H. 1·5 D., V. 10/40 to 10/30, and slight divergent squint on the left side. Crossed diplopia could be produced with a red glass, tenotomy of the left abducens sufficed to correct it. I had not concealed my doubts as to her statement that she had previously squinted inwards, but they were quite dispelled by a photograph taken about twelve years before, in which decided right convergent squint could not be mistaken. There is something to be said for the fact that it may have been a periodic squint, which occurred during the taking of the picture, as the photographer would have taken pains to hide a permanent squint in some way. Conscious suppression of squint happens now and then, although very rarely.