These persons, as may be gathered from what has been stated, saw fewer colours than other people: hence arose the confusion of different colours. They called the sky rose-colour, and the rose blue, or _vice versâ_. The question now is: did they see both blue or both rose-colour? did they see green orange, or orange green? 111. This singular enigma appears to solve itself, if we assume that they saw no blue, but, instead of it, a light pure red, a rose-colour. We can comprehend what would be the result of this by means of the chromatic diagram. 112. If we take away blue from the chromatic circle we shall miss violet and green as well. Pure red occupies the place of blue and violet, and in again mixing with yellow the red produces orange where green should be. 113. Professing to be satisfied with this mode of explanation, we have named this remarkable deviation from ordinary vision "Acyanoblepsia."[2] We have prepared some coloured figures for its further elucidation, and in explaining these we shall add some further details. Among the examples will be found a landscape, coloured in the mode in which the individuals alluded to appeared to see nature: the sky rose-colour, and all that should be green varying from yellow to brown red, nearly as foliage appears to us in autumn[3].--Note H. 114. We now proceed to speak of morbid and other extraordinary affections of the retina, by which the eye may be susceptible of an appearance of light without external light, reserving for a future occasion the consideration of galvanic light. 115. If the eye receives a blow, sparks seem to spread from it. In some states of body, again, when the blood is heated, and the system much excited, if the eye is pressed first gently, and then more and more strongly, a dazzling and intolerable light may be excited. 116. If those who have been recently couched experience pain and heat in the eye, they frequently see fiery flashes and sparks: these symptoms last sometimes for a week or fortnight, or till the pain and heat diminish. 117. A person suffering from ear-ache saw sparks and balls of light in the eye during each attack, as long as the pain lasted. 118. Persons suffering from worms often experience extraordinary appearances in the eye, sometimes sparks of fire, sometimes spectres of light, sometimes frightful figures, which they cannot by an effort of the will cease to see: sometimes these appearances are double. 119. Hypochondriacs frequently see dark objects, such as threads, hairs, spiders, flies, wasps. These appearances also exhibit themselves in the incipient hard cataract. Many see semi-transparent small tubes, forms like wings of insects, bubbles of water of various sizes, which fall slowly down, if the eye is raised: sometimes these congregate together so as to resemble the spawn of frogs; sometimes they appear as complete spheres, sometimes in the form of lenses. 120.