These phenomena are above all visual, and the intellectual character of mescal intoxication as compared with perhaps any other intoxication, seems connected with the fact that it is the most intellectual of the senses that is chiefly involved. The visual effects of mescal may be of very various character, largely depending on the idiosyncrasy of the subject as well as on the degree of the intoxication. They vary from an exaggeration of the normal phenomena, producing a heightened play of light and shade and color, to visions seen on the curtain of the eye-lid with closed eyes and with open eyes in the dark, up to actual localized hallucinations seen in broad daylight. It seems reasonable to suppose that the cerebral centers of vision are affected under mescal, and the occipital headache which occasionally follows supports such an assumption; a merely peripheral stimulation could scarcely suffice to account for such an orgy of vision. But at the same time I am convinced that the conditions produced in the eye itself are important factors in the production of the phenomena. Not only must we suppose that the retina, like all the sensory apparatus, has become hyperæsthetic, but the pupils are dilated, so widely dilated in one of my subjects that there was extreme photophobia. It is probably not without significance that in the other chief vision-producing drugs, such as haschisch and belladonna, the pupils are also dilated. It is evident that light can penetrate into the chamber of the eye with much more ease than usual. The Kiowa Indians sit round a fire during the nights on which the mescal rites are performed and I have found that the flicker of fire-light acting through the closed eyelids furnishes a very favorable condition for seeing the visions to advantage.
There is another characteristic of a large number of these visions (as indeed of many visions otherwise produced) which, it would seem, we must explain through peculiarities of the eye. I refer to what I have termed their kaleidoscopic character, the tendency to symmetrical grouping in the visual field of objects similar in shape, and harmonious, though not necessarily similar, in color, so that a kind of vision is produced such as we might attribute to an animal with faceted eyes. We might account for such a phenomenon by means of that irregular astigmatism, found more or less in normal eyes, which has been attributed to the fact that the crystalline lens is composed of many sections connected by radial sutures, or, more plausibly, with Shelford Bidwell, who has made some interesting experiments on this point, to the light passing through the coarse-meshed tissues of the eyes. With perhaps still greater probability we might adopt the suggestion of Zehender who in dealing with subjective visual perceptions would explain the strikingly regular polygonal figures which arise under various con-
- Shelford Bidwell, 'Multiple Vision,' Nature, April 13, 1899.
- Klinische Monatsblatt für Augenheilkunde, November, 1895.