«Oriuuatnal 1apers AN ENQUIRY INTO THE CAUSES OF MESCAL VISIONS BY C. R. MARSHALL, TUNBRIDGE WELLS INTRODUCTION MESCAL hallucinations have recently ...»
THE JOURNAL OF NEUROLOGY
Vol. XVII. APRIL, 1937 No. 68
AN ENQUIRY INTO THE CAUSES OF
C. R. MARSHALL, TUNBRIDGE WELLS
INTRODUCTIONMESCAL hallucinations have recently been investigated in the hope that their elucidation might help to unravel other hallucinatory phenomena.
Zucker 1 administered mescaline to patients with hallucinations. From the protocols given many of the effects obtained (coloured lights, tapestry patterns, visions of snakes and other animals) appear to have been similar to those induced by mescaline in normal persons. He concludes with the non- committal statement that the hallucinatory experiences of mescaline are not essentially identical with other hallucinations.
The hallucinations produced by mescal have been frequently described, most recently by Guttmann.2 They are predominantly visual. They vary somewhat in different individuals, but show common features which have not been explained, but which in a search for causes seem worthy of study.
Knauer and Maloney 3 state that 'it was characteristic of practically all the poisonings that to wavy lines succeeded mosaics; carpets; floral designs;
ornaments; wood carvings; windmills; monuments; mausoleums;
panoramic landscapes; statuesque men and animals, frequently of un- natural doll-like forms; and finally complete scenes which changed so as to unfold episodes in a connected manner.' Rouhier4 divides the hallucinations experienced into four conventional classes, but the sequence, fundamentally, is much the same as that described by Knauer and Maloney. Most of Beringer's 5 experimenters experienced a similar succession.
COLOUR AND FORMThe visions which are the most characteristic features of mescal intoxicas tion are unique in colour and in form and in the fact that they are best seen 289 u 290 ORIGINAL PAPERS and usually only seen in darkness or dim light. Any environment not associated with dim lighting plays little part in their formation. Hallucina- tions induced by drugs which act predominantly on the brain do not have these characteristics. Those associated with cerebral depressants rarely show abnormal colours; their sequence of form perception is usually more rapid and more disconnected; and, in the slighter degrees of intoxication at least, environment plays a notable part. The Old Man of the Mountains was well aware of this factor in the phantasies produced by Indian hemp.
Personal experiments.-My own experiments were made with natural and synthetic mescaline sulphate. As the effects produced were broadly similar to those experienced by other investigators they need very brief description. Two modes of administration were employed, oral and intravenous. The effects of intravenous injection have not, as far as I am aware, been previously recorded. Up to doses of 0 05 gm. no distinct symptoms were produced. This dose caused only slightly more brilliant phosphenes, apparently somewhat more prolonged after-images, and, after retiring (four and a half hours after the injection), the appearance for a short time of dull-coloured mosaics. The intravenous injection of 01 gm. mescaline sulphate caused slight paraesthesia and a feeling of chilliness, but no distinct visions until an hour after the administration. Then, on closing the eyes, blue enamels were perceived and a little later, when the eyes were bandaged, dull-coloured mosaics, slowly moving crocodile skins and later grotesque figures like caricatured kings on playing-cards. Afterwards a nursery wallpaper pattern and a theatre-like scene were experienced. The bandage was then removed for other observations. What is remarkable in these experiments is the slow appearance of the visual symptoms and the large dose, relative to the minimum oral dose, necessary to produce them.
The minimum dose required to produce distinct hallucinations when taken by the mouth was 0-2 gm. mescaline sulphate. This dose usually produced a somewhat better effect than 0.1 gm. intravenously. The first symptoms were more brilliant phosphenes when the eyeballs were pressed upon. Later in the dark or in a dimly lit room with eyes closed, a panorama of multicoloured lights, clouds, geometric forms, was perceived, followed by iridescent snakes or similar animals, incomplete scenic displays, and, usually later, by statuesque and distorted objects. Sleeplessness and nausea were invariable accompaniments. Larger doses did not produce correspondingly more intense effects.
Colour.-The purely colour effects of mescal visions are difficult to explain.
Knauer and Maloney 6, by using Marbe's colour wheel, found an increased sensitiveness to colour; and Mayer-Gross and Stein 7 noted a greater appreciation of the differences of delicate shades and tones. Fernberger 8 states that colour seems more saturated at the periphery than at the centre of the visual field. I observed nothing distinctly abnormal in the spectrum whilst under the influence of mescaline. Continued observation of the THE CAUSES OF MIESCAL VISIONS 291
AN ENQUIRY INTO
Complementary colour changes are sometimes complex. In one experiment I looked at a 60-watt lamp with closed eyes at about 6 inches distance.
The field was bright brick red and soon showed circulatory movement or moving mosaics or scenes and on turning away the head from the light or covering the closed eyes with the hands the complementary brilliant green colour appeared. What was surprising was that on facing the light again brilliant green patches were seen for a short time in the red field. The observation was made several times and the effect seemed to be uninfluenced by the length of exposure, even to fatigue, of the light in the first instance.
The colours of objects perceived as visions in the dark tended to exhibit a preponderance of the shorter wave-lengths of the spectrum; and the combination of colours in objects conceived often seemed more delicate than those common in nature and more comparable with the colours seen when using circular polarization with the microscope. The riot of colour observed under mescaline cannot be attributed solely to processes occurring in the rods and cones. Whatever changes may be associated with colour vision of this kind in the retina, the culmination of the colour perception must be central and is probably associated with an increased sensitiveness of the colourperceiving centres, intensified, it may be, by a perverted idealization of presented combinations.
Form. With the perception of form we are on ground capable of stricter investigation. Since visions of form may occur with closed eyelids or in a dark room, external objects are not essential to the visual hallucinations. A fundamental cause of these must therefore be within the body itself; and theoretically it nmay be in the ideational or visual centres within the brain or in the structures within the eye. A wholly central causation offers many difficulties. Mescal visions are characterized by what Kluver 9 has called 'form constants.' Those he mentions are: (a) grating, lattice, fretwork, filigree, honeycomb or chessboard design; (b) tunnel, funnel, alley, cone or vessel; (c) spiral. The most frequent of this type is the tapestry pattern, which will be considered later. It may, I think, be postulated that if circulatory movement is constantly seen by different individuals there must be some peripheral stimulus producing it; or, if similar geometrical forms are perceived by different individuals, the cause must be sought at or near the periphery. It is almost inconceivable that a part of the visual centres should be solely concerned with the presentation of such specialized patterns.
U2 292 ORIGINAL PAPERS
ENTOPTIC ASSOCIATIONSAs entoptic phenomena, under the conditions producing the visual hallucinations, seemed to be possible factors in inducing these representations, those of my own eyes were investigated with this end in view. The entoptic appearances ordinarily visible arise mainly from motile forms in the vitreous or from secretion on the cornea, but they may result from conditions in the cornea, the crystalline lens, or other structures of the eye; and by special manoeuvres the network of retinal vessels may be observed; but none of these entoptic phenomena can be seen in the dark and none of them could produce a semblance of the image forms seen during mescal intoxication. In the search for an explanation of mescal visions, investigation led to the discovery that retroretinal structures can be observed; and, since it is under similar conditions that mescal visions are experienced and retroretinal structures are seen, it seems probable that we have here the primary cause of these constant visual hallucinations. The results obtained and the methods employed have been described.'0 The most interesting of the retroretinal structures that can be observed is the choriocapillaris. This circulation is one in sinuses and when seen fully resolved has a foliaceous appearance and is in turbulent motion. Unlike the perception of the retinal vessels it covers the whole visible field and indeed is most apparent in the foveal region. Out-of-focus presentations are common and when seen with closed eyelids against suitable lighting are usual. They may appear as variants from indistinct marbled forms, showing evidence of some circulatory movement, to whirling arabesques.
Besides the choriocapillaris, the pigment granules in the retinal pigment layer may be observed, most commonly as fine granules covering the choriocapillary circulation, and, rarely, as discrete granules or crystals apart from the circulation. Thus more than one retroretinal plane may be perceived and apparently under different magnifications. It is questionable, however, if the layer of pigment granules alone plays any part in producing mescal visions. The luminous points which may be seen under special conditions of lighting are probably more potent factors. The most easily observed of the luminous points are the darting points seen by gazing with relaxed accommodation at the reflected light of the mercury lamp or other uniform white surface. These luminous points are probably circulating red blood corpuscles in the capillaries of the inner nuclear layer. They may play a part in the production of some mescal visions, but against this view there is the very serious objection that normally they require a considerable intensity of light to make them visible and in light of this intensity mescal visions in my experience are never present. Other luminous points which may be observed in special circumstances are corpuscles, probably white corpuscles in the choriocapillary circulation. They may be seen for a short time running across the foveal position after relaxation of heavy pressure on the eyeball.
Heavy pressure on the eyeball, as Vierordt 11 found, may also bring into view 293
AN ENQUIRY INTO THE CAUSES OF -MESCAL VISIONSthe choriocapillary circulation; and this fact suggests that a small amount of energy, which is interpreted as light, emanates from the circulation. This hypothesis is supported by the effect of intravenous injection of santonin when the eyes are dark-adapted 12; and by the fact that in mescal intoxication a transient retroretinal illumination may be induced by exertion, as will be mentioned presently. Under ordinary circumstances the luminous intensity of the circulation is so small that it is not perceived, except possibly as part of the self-light of the eye, but in the state of increased sensitiveness of the visual centres which mescaline appears to induce, this small intensity of light may be, in some measure, perceptible. The sensation of brightness in the dark room is mentioned by many experimenters. One of Beringer's subjects 13 was astonished at the clearness of his arm, etc., and began to laugh, saying, ' People call this a dark room ! a room in which I can almost see to read ! ' It is difficult to avoid the conclusion that in these cases there is abnormal sensitiveness to luminous stimuli of small intensity.
Pressure OIl the eyeball also causes starry lights and geometrical figures.
The star-like lights probably arise from the pigment granules which have absorbed light-energy and under pressure are able to emit sufficient electrons to produce the appearance of luminous points. The geometrical figures, in my opinion, are due to the compactness and small diameter and regular arrangement of the rods and cones and a light source behind, mainly pigment granules, producing diffraction-like figures.
The earliest visual effects of mescal are usually produced by pressure on the eyeball; they are, that is, earliest experienced as phosphenes. They consist of light effects and geometric patterns. Geometric forms-honeycomb and lattice designs however, are perceived under the influence of mescal without pressure on the eyeball, and it is suggested that their production is not dissimilar from that of pressure phosphenes. Owing to an increased sensitiveness of the visual centres the threshold of sensibility is reduced to the extent of perceivinig retroretinal pictures which are only observed by the normal retina when the stimulus has been intensified by pressure on the eyeball. Under the influence of mescaline the geometrical figures are more varied than those obtained by pressure. The difference may be due to complications induced by some perception simultaneously of the choriocapillaris and to the altered cerebration and consequent less control of conlcepts in a mescalized state.