Perception of color may be reduced, confused, or abolished in the retina, either a diffused general way, throughout the field of vision, or following the laws of hemiopic distribution. In cases of hysteria, achromatopsia is not rarely met with, affecting the eye corresponding to the side on which the skin is analgesic or where paralysis exists. Hysterical achromatopsia may be transferred from one eye to another by the application of metals, by hypnotic manipulations, etc. Hemianopsic phenomena may be functional and transient, as witnessed just before attacks of migraine or sick headache. Attempts recently made, from purely theoretical considerations, to locate centres in the occipital cortex for perception of light, form, and color separately, are wholly unjustified or at least premature. Loss of reflex pupillary movements is a symptom of much importance. It occurs chiefly under these conditions: (1) with paralysis of the iris due to lesion of the third cerebral nerve; (2) with amaurosis or anæsthesia of the retina; (3) with posterior spinal sclerosis. The last condition is distinguished from the others by the fact that while the reflex iritic movements are lost, the quasi-voluntary movement of accommodation efforts is preserved. This condition is known as the Argyll-Robertson pupil. Diplopia, or double vision, is due to paresis or paralysis of one or more of the ocular muscles, and as such is to be classed under motor symptoms. Megalopsia (apparent enlargement of objects) and micropsia (apparent reduction in size of objects) are sometimes due to disorder of the accommodation apparatus within the eye, and to local diseases causing displacement of the rods and cones of the retina; but they are often, no doubt, fanciful (in neurasthenia and hysteria). The same remarks apply to monocular diplopia.