68 POPULAR SCIENCE MONTHLY. 



suddenly formed upon a bright ground the patch appears to be momen- 

 tarily surrounded by a blue border, and he accounts for this by the 

 theory of a sympathetic affection of the red nerve fiber; when the light 

 is suddenly cut off from a patch in a bright field, there occurs an 

 insensitive reaction in the red fibers just outside the darkened patch, in 

 virtue of which they cease for a short time to respond to the luminous 

 stimulus, in sympathy with those inside the patch. The green and 

 violet fibers, by continuing to respond uninterruptedly, give rise to the 

 sensation of a blue border. Where highly competent experts fail to 

 agree it would be rash to state any definite conclusions. It is difficult, 

 however, not to believe that, whatever the precise retinal process may 

 be, over- stimulation and fatigue certainly have very much to do in 

 calling it into action. Associated with the violet halo, as we have 

 found, there is a tendency under mescal, especially by the aid of a bright 

 flickering light, for shadows generally to be variously colored, more 

 especially (as in erythropsia and allied conditions) towards the out- 

 skirts of the visual field. Any one who will sit for a few minutes with 

 his eyes directed on a sheet of white paper illuminated by bright 

 sunlight will soon begin to see on a small scale a faint reproduction of 

 the colored shadows seen under the influence of mescal. Here clearly 

 we have a fatigue phenomenon due to over-stimulation by bright light, 

 and precisely analogous to the after-images produced by looking at 

 any excessively bright object. Under mescal we have a similar effect 

 produced, not through the stimulation of unusually bright light, but 

 by the unusually hypersesthetic condition of the visual apparatus, due in 

 part to the dilatation of the pupil and in part to the effect of mescal on 

 the retina. 



There is one other effect of this fascinating drug to which attention 

 may finally be called. It has been pointed out that under mescal all the 

 peripheral sense organs become highly irritable or hypersesthetic. Not 

 only is this so, but they are brought in a quite unusual degree into 

 sympathy with each other. I found that casual stimulation of the skin 

 at once heightened the brilliancy of the visions, or produced an impres- 

 sion of sound. One of my subjects, an artist, had a curious sensation 

 of tasting colors, and another found that music had a delightful 

 influence over the visual effects. This, and the fact that the Indians 

 keep up a continual beating of drums during the time they are under 

 mescal, led me to plan a further experiment on myself with mescal. 

 I arranged that when the stream of visions was in full force a friend 

 should play to me on the piano various pieces of a more or less 

 progressive character which were unknown to me, at all events by name. 

 I found that these pieces, more especially those which were somewhat 

 uniform and monotonous, not only distinctly stimulated the visions, 

 but influenced their character; and in about half the tests there was a- 



