Chapter VI. Complementary Colours

The Human Atmosphere, by Walter J. Kilner, [1920], at sacred-texts.com

p. 141

CHAPTER VI

COMPLEMENTARY COLOURS

SOON after the discovery of the aura, a friend called attention to the fact that if a light were gazed at, and the eyes were first turned to one side and then the other of any person, the colours of the spectre were often not identical. Having convinced himself that this peculiar phenomenon did manifest itself, the writer thought it possible that the apparition might be made an aid to diagnosis, but that for that purpose investigations must be carried out methodically. Experiments were commenced by gazing at gaslight, not that for a moment was it thought that such a crude plan could be satisfactory, but in the hope that the discovery of its defects might assist in future trials. It was noticed that the resultant phantom was complex, as the main portion was of one hue, and was surrounded by another entirely different. The inconvenience of having to work with two or more colours was immediately apparent, and this, coupled with another insurmountable difficulty arising from the constant changes in the colours of the spectre, which were initiated by the slight movements of the eyes for comparing the two sides of the patient, caused accurate results to be impossible. It was also recognized that if any benefits were to be derived from this process a monochromatic image was essential. After many experiments it was concluded that for obtaining this, pieces of paper of different colours answered the purpose as well as any thing else, though they were afterwards replaced to a great extent by transparent coloured screens, which will be described later on.

p. 142

This chapter will be devoted to the problem of the effect of the aura upon complementary colours, than which a more extraordinary property can hardly be conceived. The monochromatic spectre is modified by the aura so that its colour is changed to a lighter or darker shade or its hue altered under certain conditions. It is needless to say that the whole topic is difficult and complicated, but the explanations that seem most useful will be given. Some of the theories put forward may appear far-fetched or even heterodox; nevertheless they are advanced for want of better hypotheses. As the subject is entirely dependent upon colour vision, a few preliminary remarks will not be superfluous.

One widely accepted theory postulates the existence of three sets of colour-sensitive nerves in the eyes. White light is the outcome of an equal stimulation of all the colour-sensitive nerves, or, perhaps, it would be more accurate to say a stimulation proportionate to that which occurs with sunlight. The withdrawal or weakening of the stimulus to any set will produce a colour sensation which is thus derivable from the excitation of one, two or all of these sets of nerves, either separately or in combination. When more than one set of nerves are excited, they are usually unequally stimulated.

The writer has for many years considered that each person has their own proper primary colours, and accordingly sees a coloured object differently to any one else, but as a result of education every one calls the colour ^* by the same name. For instance, let two persons A and B look at an object of a colour usually designated as a shade of yellow. This colour might

p. 143

only stimulate one set of colour-sensitive nerves of A, and would be to him a pure yellow. On the other hand, with B, not merely the yellow-sensitive nerves be excited but to a slight extent the blue-sensitive; he would see a greenish yellow tone. But as both A and B have been taught that the colour is a certain shade of yellow, which, whenever they see, they will call by the same name. Nevertheless if A saw it with B's eyes he would designate it differently. Both would be correct. It follows as a corollary, that each individual probably sees in nature hues unlike those perceived by his neighbour. It is unnecessary to enter into this matter more fully except to state that the writer's primary colours are at the present time red, yellow, and blue, although thirty years ago the blue discs were a purple-blue. It is not proposed to consider any other theory, as this one will answer the purpose of explaining the action of the complementary colours.

Putting aside all speculations, it will be found that when one set of colour-sensitive nerves is exhausted to the utmost extent, the observer will on necessity be temporarily to the corresponding colour blind. If the red-sensitive be the nerves fatigued, he will be red-blind, although still able to perceive all the colours that do not contain red; in addition he will be able to see any colour that has an admixture of red, but as if all the red has been removed. Taking a simple example, purple would be more or less blue. This artificial colour-blindness evidently causes the eyes to become hyper-sensitive to many colours and shades of colours that do not contain red, as red helps to obscure a very faint tinge of other hues. The following experiments have been tried by many people, and will furnish a proof of the above remarks. When a band of light tinged with carmine, is thrown upon a white screen from a magic lantern, it will have a certain visibility, but should the observer previously

p. 144

look through a red or a blue glass at daylight for a minute or so, he will see the band having more blue, or more red respectively, although, perhaps, not quite as brilliant. Similar effects can be obtained after the eyes have been fatigued by looking at a blue or a yellow strip of paper (vide ultra), when the observer has for all practicable purposes become temporarily blue-blind or yellow-blind. Were it possible for two sets of colour-sensitive nerves to be inhibited for some short time, the observer would be completely monochromatic. This extreme proceeding is never requisite for the present investigations, and in practice it has been found impossible by this method to induce total red, blue or yellow blindness. However, the remark that "the eyes have become abnormally sensitive to certain shades of colour" remains correct. It is quite reasonable to suppose that this colour hyper-sensitiveness of the eyes permits the rays of the aura which are probably ultra-violet, otherwise invisible, to be perceived, and that this is one of the explanations why the different coloured patches can be seen within the complementary coloured bands.

In ill health, as will be noticed hereafter, the aura frequently contains more yellow than during good health, and this colour is especially pronounced in circumscribed areas from local disturbances. These patches are usually seen as yellow places in the midst of the blue complementary coloured band. The rationale of this phenomenon is probably as follows: when the eyes have become sufficiently fatigued for the successful induction of the blue complementary coloured band, the yellow-sensitive nerves are only able to convey to the brain sensations of that colour to a limited extent, while they still retain their power intact for the shorter wave lengths of the ultra-violet yellow. Possibly these latter exert a greater influence from not being obscured by the more easily perceived yellow of the ordinary visible solar spectrum. Another

p. 145

factor which very likely assists in the perception of the auric colours, but to which too much importance must not be attached, is that the body assumes as a whole the hues of the complementary coloured band and thus affords a better contrast to the yellow or other colours the aura may locally possess. (Page 170.)

Every one knows that if he gazes intently for a short time at a coloured object and then looks at the ceiling, or at a white screen, etc., he will see on it a spectre of the same object similar in shape but of a different hue. This secondary colour will for an equal amount of stimulation always have the same tint, which is dependent upon the hue of the object, and is termed complementary to the primary colour. For example, after a yellow object, has been gazed at, the hue of the virtual object will be blue, the exact tint being governed by the shade of the yellow employed, and to a certain extent by personal idiosyncracies.

When an investigator has looked at a yellow object sufficiently long, the time varying accordingly to the brightness of the light, and the steadfastness of the gaze, etc., he will always see the after-image at first of the same blue tint, but this will gradually become lighter, and will more frequently blend with red, turning purple or plum coloured. In these cases the complementary colour always includes a red tint, although it is at first masked by the intensity of the blue colour.

Should he, however, at first see a plum or purple coloured phantom, he may be sure that his eyes have not been adequately fatigued by the original yellow colour, or else that there is a larger amount of white light in the room than usual. These modifications show the advisability of being conversant with the varying tints the spectre undergoes, but at the same time they do not make ali the difference that was at one time imagined. After a short time the phantom will vanish, but will be sure to return with an altered

p. 146

hue. This secondary change may as a rule be neglected, because the employment of the complementary colour is rarely continued sufficiently long for its advent. However, the secondary changes may at times be useful, as the following instance exemplifies.

After the examination of a woman by means of the complementary colours had been completed and the blind drawn up, in full daylight while the writer was speaking to her, a new after-image became visible upon her body, and in the middle of the band there was a yellow mark about the size of a shilling on the upper part of the left mamma about two inches from the sternum. It had been overlooked in the prior examination. The spot was quite invisible directly the coloured band had disappeared, but as soon as the eyes had been re-influenced in the ordinary manner for obtaining the complementary coloured bands, the patch became again perceptible and very distinct. Here was an unrehearsed effect which up to the present has never been repeated.

One other self-evident inference still remains, viz., that when the background is not white the complementary colours will not always appear in their true shades, but as if blended with the hue of the background.

Since these complementary colours are entirely subjective, they will receive the names of pigments which afford the best matches, these being sufficiently accurate for all descriptive purposes. After a large number of experiments had been made with the colours usually termed primary, the conclusion arrived at was, that they did not give such good results as mixed ones. As a consequence of the trials, the following colours have been chosen as the most useful.

p. 147

Each observer should it possible select by experiment what colour or colours suit him best.

In routine work, use can be made of strips of coloured paper three inches long and three quarters of an inch in width with a black dot in the centre, pasted on black board. Experience has shown that this is the largest size that can be conveniently employed, since a longer object does not yield the complementary colour perfect to the ends. With a patient standing a few feet in front of the observer, one of these strips will give a band of the complementary colour which, when used transversely, will be wider than the body, allowing the ends that are projected on each side beyond the body to be compared with one another, and also with the central portion of the body itself.

In winter or foggy weather, especially in London, the difficulty of using paper strips for obtaining the subjective complementary colours is great, and it is occasionally impossible to make a thorough examination from the inordinate time required, which is exceedingly trying to both the investigator and the patient. To overcome this defect an apparatus has been devised, which can be used in daylight or, in an emergency, even by gaslight. It consists of a cylindrical mask about six inches long and five in width, with one end shaped to fit the face, while the other has a revolving cap in which there is an oblong slit three quarters of an inch in breadth. The slit can thus be turned either horizontally or vertically to the eyes at pleasure. Behind the slit is placed a piece of ground glass, and at the back of this again a transparent screen, which may be either a cell containing a fluid, or else a piece of stained glass. The mask ought to be blackened inside or else lined with velvet. A small mark can be made on the ground glass to act in a similar way as the dot on the coloured papers. The distance between the eyes and the screen will be about

p. 148

correct for emmetropic sight, but for presbyopia and myopia the reading glasses worn by the observer will be needed. The writer's personal apparatus has a removable diaphragm with lenses of the same focal length as the spectacles he usually employs. ^*

To use the apparatus, it is only necessary to hold it in front of and close to the face, and to gaze at the light, keeping the eyes fixed on the mark on the ground glass. In a few seconds the eyes will have become sufficiently affected, and the complementary coloured band can be perceived in the same manner as if the coloured papers had been used. The apparatus requires more skill in using than the coloured papers, as the screen needs alterations in depth of colour according to the brightness of the light.

As soon as the patient is ready for examination, he should stand in front of a white background opposite the light and illuminated evenly all over. Should there be any shadows on the background they must be made to correspond on the two sides. Preferably the light should be brighter than when the aura itself is being inspected, but almost always it will be necessary for one blind to be partially or wholly drawn down. After everything has been properly arranged, the observer must look at the sky through the transparent screen in the mask, or stare at one of the coloured paper strips, keeping his eyes fixed on the dot from twenty to thirty seconds according to the brightness of the light.

When coloured strips are used a brilliant light is required, so it will be necessary to pull aside the blind to allow the paper to be fully illuminated. The observer then turns towards the patient and looks at some pre-determined spot on the median line of the body, when, if used transversely, the complementary

p. 149

coloured band will be seen reaching across the body and extending to the background on either side, the whole being simultaneously visible. He is thus enabled to notice variations in the shades of the colour in every part of the band. The tints of the extensions of the band prolonged beyond the trunk can be compared with each other, but of course not with the portion on the body itself. The above-mentioned method, although simple, requires a considerable amount of practice, and the mastery of one or two details, trifling in themselves, will assist greatly in speed and comfort. First, while looking at the coloured strip, it is indispensable to fix the eyes on one particular spot and keep this in exact focus the whole time, as unless this is properly done there will be blurring and an increase of time needed for obtaining the requisite effect. A slight exercise of will is required for this, but practice will soon make the effort almost involuntary. Secondly, a novice often experiences a difficulty in keeping his eyes on a given place on the patient's body, owing to the proneness of the complementary coloured band to wander, often out of the field of vision, and for the eyes to follow it, thus completely destroying the value of the observation. When the habit of keeping the eyes stationary on one point has been acquired, the complementary coloured band will remain fairly motionless, and should it move away will return to its proper position of its own accord. As dexterity can only be attained by exercise, it is a good plan to train the eyes upon some inanimate object before proceeding to the examination of the human subject.

For the future, unless otherwise specified, the yellow strip of paper with its blue complementary coloured band will be the colour implied, and also for the sake of brevity, the letters c.c. will be employed instead of "complementary colour," and p.c. will indicate the colour of the strip itself.

p. 150

As there are natural variations in the colour of the skin, and shadows on the body of a patient, the observer ought to notice every modification, however insignificant, before inspection with the c.c. band. With care, judgment, and a little experience, most of the difficulties from these causes will disappear. In its simplest form the c.c. band projected upon the body of a person in good health will be equal in tint all over, if due allowance has been made for any variations in the colour of the skin, and the extensions of the band beyond the body will generally correspond in hue with each other.

When the extensions of the c.c. band show on a healthy subject a tint on one side unlike that of the other, the difference is rarely great. This dissimilarity of shade is the simplest form of alteration of the c.c. band, and may only be the consequence of improper lighting; however, all doubt can be dissipated by turning the patient completely round, when, if correct, the different tints will have changed places, this being proof positive that the alteration depends upon the aura itself.

Another very characteristic effect can often be elicited as follows:—note which extension of the blue band has the deeper shade; then gaze at the blue p.c. strip of paper to induce a yellow c.c. band. More frequently than not the latter will have a lighter shade where the blue c.c. band was darker, and vice versa.

An occasional change in the c.c. band, when projected upon the body of a patient who at the time is not in good health, and standing with his face Jo the observer, is for one side of the body to be darker than the other. When this happens, the shades may blend gradually into one another, or a sharp line of demarcation may divide them. In the majority of instances when the division is sharply defined, it will take place at the median line of the body, but there are many exceptions to the rule, and the line of separation may

p. 151

occur at any distance to the right or left. If the c.c. band (on one side of the body light and on the other dark), be continued beyond the body, the extension on the light side will invariably have a paler shade than the extension of the dark portion of the band. This change seldom if ever occupies the whole of the trunk, and occurs most frequently between the levels of the mammæ and umbilicus. Sometimes one thigh has a different shade to the other. The dark part generally overlies a deranged portion of the body, and it will be found that this place is absolutely of a deeper hue than the rest of the band. On the other hand the affected portion of the body may cause the c.c. band to become lighter, instead of darker.

There is another variation slightly different, but much more common, in which instead of the c.c. band across half the body being changed in shade, a patch either large or small is lighter or darker than the rest of the band which surrounds it. When the patch is large it occasionally takes the outline of an organ in whole or in part. The smaller patches, not exceeding an inch or two in diameter, do not in themselves determine what organ is affected, though they generally point to some disease or local disturbance and almost invariably to the seat of pain or tenderness.

A third constantly occurring alteration of the c.c. band consists of patches or spots of a colour different to that of the rest of the band. Some shade of yellow seems the most frequent, and the interpretation, with very few exceptions, is that the patient has at the time, or has had recently, pain and tenderness at that place. The colour does not necessarily denote anything abnormal, as it has often been seen on the epigastrium when there has been no dyspepsia to account for it, and it is then apparently dependent upon active digestion of food partaken a short time previous to inspection. Elsewhere it generally points to some pathological change.

p. 152

Four p.c. strips of coloured papers or four transparent screens have been chosen, each possessing advantages not presented by the others. These advantages seem to be generally dependent upon obscure causes connected with the patient. For ordinary observations the p.c. strip giving rise to the blue c.c. band is the most useful, and generally the only one needed, since it is more sensitive to changes than the yellow c.c. band, which is as its complementary especially valuable as a control to the blue c.c. hand, if the change in tint be only slight. There are, however, occasions when it is better to work with the yellow c.c. band rather than the blue. Perhaps the most sensitive of all the c.c. bands is the green, but unfortunately it does not undergo so many variations as the blue, and the changes are more fleeting in character. In cases of doubt, its delicacy of action will determine a question of fine differences of colour. The choice of the colour for the c.c. band is usually unimportant, when it is borne in mind that occasionally owing to individual idiosyncrasies better results can be obtained with one colour than with another.

A prolonged examination will fatigue the observer's eyes, and as no amount of will power can render any assistance, he must either leave off the inspection for a few minutes or else change the c.c. band. The former, when possible, is preferable, as the latter is only a makeshift to be used when time is of consequence. The opposite c.c. band will then be the best to employ.

A most pertinent question and one most difficult to answer now arises. What is it that causes the band to be altered in colour? In the first place for reasons already stated, it seems more than probable that the eyes of the observer are hyper-sensitive to certain colours after gazing at one of the p.c. strips of coloured paper, and can differentiate tints so nearly alike as would baffle ordinary perception. Next, theoretically,

p. 153

there seem to be five agencies that can alter the shade of the c.c. band; firstly the skin; secondly the thickness of the aura; thirdly a change in the texture of the aura; fourthly the colour of the aura; and lastly

rays.

Each of these propositions will be considered in turn. After making all possible allowances for any variations in tints than can be appreciated in the ordinary manner, it is quite within the bounds of reason to imagine that there may exist hues in the skin that can be distinguished only under exceptional circumstances. This has been kept constantly in mind and instances have been sought for that would settle the question, but up to the present time without any success, so that although possible, this agency must be so extremely rare as to be negligible. One fact that especially militates against the skin being the cause of the change, is that when the c.c. band is discoloured up to the edge of the body, the extension will be in like manner affected, being lighter or darker as the case may be. Under no circumstances can the latter change be due to the influence of the skin, consequently there is nothing to which it can be attributed except the aura, although it hardly seems possible that such a transparent, colourless, almost invisible cloud should have so powerful an action upon the c.c. bands.

Secondly is the thickness of the aura competent to induce any change in the c.c. band? As the aura is composed of highly attenuated material (the word is used advisedly), it would be necessary to acquire an enormous thickness before any perceptible alteration could be produced. Everything points to a negative answer to this proposition. One case illustrates the fact in the strongest manner. A woman, when standing sideways to the observer, showed an aura in front of the abdomen quite four times as wide as by the thorax, yet when she turned facing, no difference

p. 154

could be detected either directly or with the c.c. band, which was uniform in colour over both the thorax and abdomen. Pregnancy supplies analogous cases, as the aura is in front of the abdomen much wider than before the thorax. Never has this extra breadth been observed to make any change in the shade of the c.c. band unless accompanied by some alteration in colour or texture.

The first two theoretical agencies that might cause a change in the shade of the c.c. band have thus been discounted, and there remains a third and fourth, which offer better chances for a solution of the problem.

Thirdly, can an alteration in the texture of the aura induce a sufficient change in the c.c. band to account for variations in their tints? When the writer first began to employ the c.c. bands, he imagined that after gazing at the p.c. strip of coloured paper and then exploring the body through the light dicyanin screen, he was able to distinguish shades of colour better than without the intervention of the screen, and consequently this method was habitually used. Unfortunately this was a mistake, as it led to patches that could be seen discoloured without the intervention of a screen, being attributed entirely to an alteration of the texture of the aura, consequently giving a greater prominence to that condition than it merited. It is highly probable that in the majority of instances an alteration of the texture and chromatic changes go hand in hand. There remain, however, cases in which no traces of colour can be detected, so that modification of the texture of the aura is the only explanation left. If with each of the c.c. bands employed in succession the patch continues to be either darker or lighter than the surrounding tint of the band, the presumption is that the change of the shade is the result of some peculiarity in the texture of the aura. On the other hand, should one of the

p. 155

bands show a light patch which appears dark with the rest of the bands, then it is likely that there is some other change. (See page ¹⁵⁵.) It is quite on the tapis that two of the bands may disclose a light patch which others show dark. This probably means that the patch is caused by two auric colours, which primarily due to ultra-violet radiations, for some reason do not blend in the ordinary manner. A good illustration as to what may be taken as an alteration of texture producing a dark patch, is as follows:

Case 28. C., a man fifty-three years old, was inspected in October, 1914. He was not really strong, but made the most out of every ailment. He had just recovered from an attack of lumbago brought on by rowing when not accustomed to that exercise, and afterwards getting a chill. He had been subject to indigestion and also addicted to taking too much alcohol. His aura had a blue-grey colour. The outer which was quite plain and distinct, had a breadth of eight inches by the side of the head, four and a half by the trunk, five at the back, and three by the thighs and legs. The inner aura was below the average in clearness, about three inches wide, granular at the small of the back, and also by the right hypochondrium as he stood sideways, but otherwise healthy. All the four c.c. bands showed a dark patch on the back, over the two lower dorsal and all the lumbar vertebræ, which reached to about two inches from the edge of the body on each side. This patch did not seem to be derived from any local colouration of the aura, as tested by the c.c. bands, so that there was nothing to which it could be assigned except the texture. In front with the blue c.c. band there was a dark patch over the liver, and a yellow one over the epigastrium. He had pain and tenderness in all these places. As he stood facing the observer with his arms akimbo, when the aura in the interspaces between the body and the arms was examined by means of the coloured screens, no yellow

p. 156

was found. Had this colour been seen, probably the patch on the back would, although dark with the blue c.c. band, have looked lighter with the yellow.

A patch may be produced by two or more colours. A good-sized patch was seen on the sacrum of a patient of a pinkish hue when the blue c.c. band was used. As the colour was uncommon, this area was examined with three other c.c. bands. With the yellow it looked rather darker than the rest of the band. It certainly was not a pure yellow, as it con-tailed a mixture of other colours, that could not be dissociated. With the red and green bands the colour was red; the tint differed in the two instances, but it was impossible to decide the particulars of the variation. Each band also made a slight alteration in the size and shape of the spot.

The only feasible explanation was, that the patch was multi-coloured, being composed of two, if not of more, colours (certainly red and yellow were there), and that the different c.c. bands resolved them. Unless the pink patch consisted of ultra-violet rays, its appearance in the red and the green bands would be incomprehensible.

When using the blue c.c. band it is not an uncommon occurrence to meet with dark and yellow patches upon the same person, but light patches accompanying the yellow are infrequent. On only one occasion have there been seen, when using the blue c.c. band, yellow dark and light patches on the same individual. The patient was a hysterical lady, of whose case a description is given in another chapter.

The pathological alteration of the texture that gives rise to a dark patch in the aura when seen by the aid of the c.c. band, always consists, so far as his been noticed up to the present time, of a coarsely granular state of the inner aura, but it is undecided whether the outer aura assists in any way. In no instance where the blue c.c. band has been employed and a

p. 157

light patch become visible, has it been possible to exclude all chromatic alterations of the aura, so as to be fairly confident that the change was wholly due to a textual modification. Theoretically an alteration of the substance may have taken place, but it is extremely difficult to obtain unequivocable proof of it, as the observer's eyes so often become tired before the examination is completed, and besides, patients naturally object to a too prolonged inspection, having usually come not for experimental but for diagnostic purposes.

The fourth agent, viz., the colour of the aura, has a much surer foundation, as patches of different colours to the surrounding c.c. band are being constantly perceived. When employing the blue c.c. band, yellow is the commonest colour, and next in frequency an indefinite pink. The shades of the yellow range from a transparent lemon to the darkest shade of Roman ochre. Besides a pink which varies a good deal, there are a number of hues that defy description, as they are evidently mixtures of ultra-violet colours. If these colours are naturally but merely locally present in the aura, an explanation is needed why they cannot be perceived except during the use of the c.c. bands. This has been partially given on page ¹⁵¹. On rare occasions it has been possible to detect them in the aura over (not by the side of), the body, but never as yet sufficiently distinct to describe. It is quite possible that better trained or more peculiarly adapted eyes may have the power of resolving them. At one time it was thought possible that the use of coloured screens might have revealed these patches without having to resort to the tedious process of partially colour-blinding the eyes. There was nothing but failure for reasons given a little later on.

In chapter iv., when discussing the likelihood of a secondary spectrum, an account was given of the inspection of the aura in the interspaces between the

p. 158

body and the arms of persons when standing facing the observer with their arms akimbo. The results are extremely interesting, but the discrepancies so great as to render impossible any attempt to tabulate them in a useful form. However, when the aura is investigated through the different coloured screens, two important facts stand out: First, during good health a blue tint is predominant. Secondly, during indifferent health the aura constantly has an addition of yellow.

In good health the aura as a rule retains its natural colour, blue or blue-grey as the case may be, when examined through the yellow or orange screens, but it generally receives a tinge of red or violet when very dark screens of these colours are employed. With the green screen the natural hue remains, or else the aura becomes a pure blue. The action of the blue screen when dark is not that which would have been naturally expected. as it almost always causes the aura to assume a blue colour of a different quality and not resembling that of the screen. At times when seen through any of the coloured screens, this blue may be mixed without blending with red, yellow, or green, but they are seldom distinct. The auras of patients who are constitutionally weak, who have been debilitated from any cause whatever, or who are ill at the time of examination, are commonly more or less changed when looked at through the different screens, for the most part by the addition of red, yellow, or green, either singly or together. The yellow is rarely absent and generally predominates over the other colours. It may be a bright yellow, but the worse the health the patient has, the more nearly the hue approaches to the deepest shade of Roman ochre.

The blue screen is the most useful, and the only one needed to show the yellow when time is of importance, but when possible all the screens ought to be employed, as sometimes very bizarre effects are obtained. The

p. 159

aura in the interspace between the arm and the trunk may be altogether blue, but usually the inner aura has a different shade to the outer, being as a rule darker or warmer. The inner may be yellow while the outer remains blue. A further variation is for the outer aura to exhibit an admixture of yellow or to be entirely yellow. The outer aura never contains yellow as long as the inner continues blue, nor is this colour ever more pronounced in the former than in the latter, so that it may be safely inferred that the inner aura becomes yellow more often and to a greater extent than the outer. It has been remarked elsewhere that the inner is the part of the aura that is most frequently changed locally, and in consequence very liable to assume a yellow hue in patches.

When an observer is investigating the aura in the interspaces between the arms and the body for colour, he is working under advantageous conditions, including besides a greater depth of the aura, a black background, but when examining the yellow patches on the body the conditions are by no means as favourable, because the body makes an inferior background, so that a yellow patch is harder to see, and consequently can only be detected by sensitive processes. This is the reason why too much importance should not be attached to the hue the body takes from the c.c. band. (See page ¹⁴⁴).

On various occasions when using the transparent screens for the inspection with the complementary colours, the band instead of being projected directly on the body, had the appearance of being advanced several inches in front of the patient, and if horizontal, seemed curved towards the observer. This phenomenon has always occurred unexpectedly, and the writer has never been able to induce it voluntarily by focusing his eyes on a plane in front of the patient, nor when it once presents itself, is he able to throw the bands back on the body, without gazing through the

p. 160

p.c. screen again to induce a fresh after-image. This peculiar type of image, moreover, is quite useless, as the c.c. band, instead of being sharply defined, has always a weird and foggy look and never showed the slightest sign of any patch.

As the complementary colours are invisible in midair, and require a background for their perception, their appearance a little distance in front of the body of a patient has a peculiar interest. It proves that there must be some substance allied to a vapour or a gas which constitutes a background. There is only one thing that this background can possibly be, viz., the aura.

Footnotes

142:* A simple test for obtaining one's own personal primary colours is to press the closed eye, when there will be generally seen small yellow dots covering the whole field of vision. Intermingling with these are much larger discs of blue, and lastly red points intermediate in size between the yellow and blue discs. The yellow are the most numerous, the blue next in number, and the red fewer and far more difficult to obtain.

148:* The distance between the eyes and the screen is rather less than the ordinary reading distance, producing a slight strain of the eyes which has been found beneficial in practice.