Asa Foetida

Mind, disposition generally affected

Mind, alternating moods

Mind, fretfulness

Mind, indifference

Intellect, comprehension difficult

Intellect, confusion

INTELLECT, VERTIGO

INTELLECT, DRUGS WHICH HAVE CONCOMITANTS OF MENTAL SYMPTOMS

Internal head, in general

INTERNAL HEAD, FOREHEAD

Internal head, temples

Internal head, sides of head

Internal head, vertex

Internal head, occiput

Internal head, one-sided, in general

External head, skull

Internal head, left side

Internal head, right side

EYES, EYEBALLS

Eyes, iris

Eyes, pupils dilated

Eyes, brows

Eyes, lids

Eyes, upper lids

Eyes, orbits

Eyes, left

Eyes, right

Vision, illusions of color, dark

Vision, lightnings

Vision, spots

Vision, indistinct

Vision, tremulousness

Vision, vanishing

Ears, external

Ears, parotid glands

Ears, discharges from ears

Ears, discharges from ears, fetid

Ears, discharges from ears, mucous

Ears, ear-wax, thin

Ears, left

Hearing, acute

Hearing, loss of hearing (from paralysis of auditory nerve)

Hearing, noises in ears, in general

Nose, back

Nose, blowing out of blood

Nose, odor from nose

Nose, odor from nose, urinous

Nose, nasal discharges, gray

Nose, nasal discharges, hardened

Nose, nasal discharges, offensive

Nose, nasal discharges, yellow

Nose, left side

Smell, illusions of smell, sulphurous

FACE, COLOR ALTERNATING

FACE, COLOR ALTERNATING, PALE

Face, color alternating, yellow spots

Face, color alternating, yellow

Face, eruptions

Face, swelling

Face, swelling, between lids and brows

Face, swelling, upper lip

Face, locations of sensations, temples

Face, locations of sensations, malar bone

Face, locations of sensations, upper jaw

Face, locations of sensations, lower jaw

Face, locations of sensations, articulation of jaws

Face, locations of sensations, upper lip

Face, locations of sensations, lower lip

Face, locations of sensations, corners of lips

Face, locations of sensations, chin

Face, locations of sensations, left side

Teeth, inner gum

Teeth, right

Mouth, breath hot

Mouth, saliva, diminished

MOUTH, SOFT PALATE

Mouth, and fauces, right side

Hunger and thirst, hunger

Hunger and thirst, hunger, without relish

Hunger and thirst, thirst

Hunger and thirst, aversion to, acids

Hunger and thirst, desire for, wine

TASTE, BAD (FOUL, PUTRID)

Taste, earthy

Taste, herby

Taste, metallic

Eructations, belching

Eructations, eructations in general

Eructations, hiccough

Eructations, waterbrash

Nausea and vomiting, nausea in, abdomen

Nausea and vomiting, qualmishness

Nausea and vomiting, retching

Nausea and vomiting, vomiting

Nausea and vomiting, vomiting, of worms

INTERNAL ABDOMEN, DIAPHRAGM

Internal abdomen, hypochondria

Internal abdomen, liver (and region)

Internal abdomen, spleen

Internal abdomen, abdomen in general

Internal abdomen, epigastrium

Internal abdomen, umbilical region

Internal abdomen, sides

Internal abdomen, loins

Internal abdomen, groins (including caecum, caecal region, ileo-caecal region, iliac region and Poupart's ligament)

Internal abdomen, hernia

External abdomen, pit of stomach

External abdomen, rings externally

External abdomen, Mons Veneris

External abdomen, inguinal glands

Abdomen, left side

Abdomen, right side

HYPOCHONDRIA, LEFT SIDE

Abdominal rings, right side

Flatulence, flatus, cold

Flatulence, flatus, sour-smelling

Flatulence, flatus, borborygmi

Flatulence, flatus, incarceration of flatus

Stool, diarrhea

Stool, diarrhea, alternating with constipation

Stool, diarrhea, painless

Stool, constipation

Stool, constipation, on account of hard feces

Stool, bilious

Stool, bloody (and dysentery)

Stool, involuntary

Stool, large

Stool, worms

Stool, worms, thread worms

Stool, troubles, before stool

Stool, troubles, after stool

Stool, tenesmus

STOOL, RECTUM

Urinary organs, kidney

Urine, albuminous

URINE, COLD

Urine, sour odor

Micturition, too seldom

Micturition, troubles, at beginning of micturition

Micturition, troubles, at close of micturition

Micturition, troubles, after micturition

Sexual organs, sexual organs in general

Sexual organs, male organs, in general

Sexual organs, male organs, penis

Sexual organs, male organs, foreskin

Sexual organs, male organs, spermatic cord

Sexual organs, female organs, vagina

Sexual organs, female organs, uterus

Sexual organs, female organs, ovaries

Sexual organs, female organs, labor pains, too severe

Sexual organs, female organs, labor pains, spasmodic

Sexual organs, female organs, labor pains, weak (inefficient, flying in all directions)

Sexual organs, desire, too weak

Menstruation, menstruation beginning, delayed in girls

Menstruation, profuse

Respiration, loud

RESPIRATION, OPPRESSED

Respiration, sighing

Respiration, slow

Respiration, superficial

RESPIRATION, ACCOMPANYING TROUBLES OF RESPIRATION

Cough, cough in general

COUGH, WITH EXPECTORATION

Cough, night with and day without expectoration

Cough, with expectoration which he is obliged to swallow

Cough, expectoration, blood-streaked

Cough, expectoration, gray

Cough, expectoration, milky

Cough, expectoration, orange-colored

Cough, taste of the expectoration, burnt

Cough, taste of the expectoration, foul

Cough, taste of the expectoration, mouldy

Cough, taste of the expectoration, of tobacco juice

Air-passages, voice, deep

Air-passages, voice, tremulous

External throat and neck, throat, external

External throat and neck, nape

External throat and neck, thyroid gland

Neck and nape of neck, left side

Neck and nape of neck, right side

Chest, internal

Chest, upper part

Chest, sternum and region

Chest, heart and region

CHEST, PALPITATION

Chest, palpitation, anxious

Chest, palpitation, heart's action, tremulous

Chest, external chest (ribs and muscles)

Chest, milk, diminished

Chest, milk, increased

Chest, left side

Chest, right side

Back, back in general

Back, dorsal region

Back, lumbar and sacral region (including small of back)

Back, coccyx

Back, left side

BACK, RIGHT SIDE

Upper extremities, axilla

Upper extremities, upper arm

Upper extremities, forearm

Upper extremities, palm

Upper extremities, fingers

Upper extremities, fingers, nails

Upper extremities, joints of upper extremities, in general

Upper extremities, joints of upper extremities, shoulder joint

Upper extremities, joints of upper extremities, elbow

Upper extremities, joints of upper extremities, elbow, bend

Upper extremities, joints of upper extremities, elbow, tip

Upper extremities, joints of upper extremities, finger joints

Upper extremities, bones of upper extremities in general

Upper extremities, left

Upper extremities, right

Lower extremities, loins (region of hips)

Lower extremities, nates

Lower extremities, thigh

Lower extremities, thigh, anterior part

Lower extremities, thigh, posterior part

Lower extremities, thigh, outer side

Lower extremities, thigh, inner side

LOWER EXTREMITIES, LEG BELOW KNEE

Lower extremities, tibia

Lower extremities, tendo Achilles

Lower extremities, heel

Lower extremities, back of foot

Lower extremities, sole

Lower extremities, toes

Lower extremities, toes, great

Lower extremities, toes, tips

Lower extremities, toes, nails

Lower extremities, corns

Lower extremities, joints of lower extremities, hip-joint

Lower extremities, joints of lower extremities, knee

Lower extremities, joints of lower extremities, knee, hollow of

Lower extremities, joints of lower extremities, knee, patella

Lower extremities, joints of lower extremities, toe-joints

Lower extremities, bones of lower extremities in general

Lower extremities, left

Sensations, air, aversion to open

Sensations, arthritic nodes

Sensations, ascending, sensation of

Sensations, asleep feeling, in single parts

Sensations, ball internally

Sensations, band, sensation of a

Sensations, biting

Sensations, blow, pain as after

Sensations, boring

Sensations, boring, inward

Sensations, bruised pain (in general)

Sensations, bruised pain (in general), externally

Sensations, burning, internally

Sensations, bubbling

Sensations, clamp-like pains, externally

Sensations, clamp-like pains, internally

Sensations, clothing, intolerance of

Sensations, clucking (gargling)

Sensations, comfortable sensation

Sensations, constriction, externally

Sensations, consumption in general

Sensations, contractions, of extremities

Sensations, convulsions

Sensations, convulsions, without consciousness

Sensations, convulsions, with falling

Sensations, convulsions, hysterical

Sensations, convulsions, with opisthotonos

Sensations, convulsions, with stiffness

Sensations, convulsions, tetanic (rigidity)

Sensations, cramps, internal

Sensations, crepitation, sensation of

Sensations, crushing sensation

Sensations, cutting, externally

Sensations, dead feeling

Sensations, death, apparent

Sensations, dislocations

SENSATIONS, DROPSY, EXTERNALLY

Sensations, dryness of internal parts

Sensations, extravasation

Sensations, falling outward of internal parts, sensation of

Sensations, flabby feeling

Sensations, flabby feeling, internally

SENSATIONS, FLOATING SENSATION (ON WAVES)

Sensations, forcings

SENSATIONS, FROZEN LIMBS

Sensations, gnawing

Sensations, gnawing, internally

Sensations, gout-like pains (arthritic)

Sensations, hard bed, sensation of

SENSATIONS, HARDENED (MUSCLES)

Sensations, heaviness, externally

Sensations, hysteria (and hypochondriasis)

Sensations, immobility of affected parts

SENSATIONS, INDURATIONS (AFTER INFLAMMATION)

SENSATIONS, INFLAMMATION, EXTERNALLY

Sensations, inflammation of mucous membrane

Sensations, inflated feeling

Sensations, internal parts, drugs affecting

Sensations, jerking, muscles

SENSATIONS, JUMPING, INTERNALLY

Sensations, loose feelings in joints

Sensations, motion, moving up and down

Sensations, mucous secretions increased

Sensations, numbness, externally

Sensations, numbness, internally

Sensations, pain, blunt

Sensations, paralysis, of limbs

Sensations, paralysis, of organs

Sensations, pinching

Sensations, plucking, sensation of

Sensations, plug, sensation of, internally

Sensations, polypus

Sensations, pressing (simple pain), externally

Sensations, pressing (simple pain), inward

Sensations, pressing (simple pain), deep, inward, with instruments

Sensations, pressing (simple pain), in joints

Sensations, pressing (simple pain), as from a load

Sensations, pressing (simple pain), in muscles

Sensations, pressing (simple pain), from within outward

Sensations, pressing, sticking, in muscles

Sensations, pressing, tearing, in joints

Sensations, rawness (and roughness), internally

Sensations, reeling

Sensations, restlessness

Sensations, rigidity

Sensations, roaring (humming and buzzing)

Sensations, rolling sensation

Sensations, sensitiveness, internally

SENSATIONS, SHRIVELLING

Sensations, shuddering

Sensations, side (symptoms on one side)

Sensations, side (symptoms on one side), crosswise, left upper and right lower

Sensations, smaller sensation

Sensations, smarting

Sensations, sore pain (smarting), externally

Sensations, sprained pain, in joints

Sensations, startings

Sensations, sticking, extending downward

Sensations, sticking, externally

Sensations, sticking, internally

Sensations, sticking, inward

Sensations, sticking, transversely

Sensations, sticking, drawing

Sensations, sticking, jerking

Sensations, sticking, pressing, in joints

Sensations, sticking, pressing, in muscles

Sensations, strangling pain (constriction)

SENSATIONS, STRENGTH, SENSATION OF

SENSATIONS, SURGING (IN BODY)

Sensations, swellings, in general

Sensations, swellings, of affected parts

Sensations, swollen sensation

Sensations, tearing, away sensation

Sensations, tearing, downward

SENSATIONS, TEARING, OUTWARD

Sensations, tearing, jerking, in joints

SENSATIONS, TEARING, JERKING, IN MUSCLES

Sensations, tearing, paralytic, in joints

Sensations, tearing, paralytic, in muscles

Sensations, tearing, pressing, in muscles

Sensations, tearing, sticking, in joints

Sensations, tearing, sticking, in muscles

Sensations, tension, in joints

SENSATIONS, TENSION, IN MUSCLES

Sensations, throbbing, externally

Sensations, throbbing, in joints

Sensations, thrusts (pushing pain)

Sensations, tickling internally

Sensations, trembling, internally

Sensations, trickling sensation, like drops

Sensations, twistings

Sensations, twitchings, of muscles

Sensations, valve in the throat, sensation of

Sensations, washing, dread of

Sensations, weakness (consult weariness and debility)

Sensations, weakness (consult weariness and debility), of joints

Glands, boring

Glands, inflammation

Glands, itching

Glands, pressings

Glands, sensitiveness

Glands, smarting

Glands, sticking

Glands, swelling

Glands, swelling, bluish

Glands, swelling, cold

Glands, tension

Glands, ulcers

Glands, ulcers, spongy

Bones, band around, sensation of

Bones, boring

Bones, broken, pain as if

Bones, bruised sensation

Bones, burning

Bones, drawing as from a thread through shafts

Bones, gnawing

Bones, gouty nodes

BONES, INJURIES

BONES, JERKS

Bones, jerking pain

Bones, looseness from flesh, feeling as if

Bones, painfulness, of periosteum

Bones, pressure

Bones, pressure, sticking

Bones, pulsation

Bones, sensitiveness

Bones, sensitiveness, of periosteum

Bones, sticking

Bones, sticking, burning

Bones, sticking, pressing

Bones, swelling

BONES, TEARING

BONES, TEARING, CRAMPLIKE

Bones, tearing, paralytic

Bones, tension

SKIN, BITING

Skin, chilblains

Skin, chilblains, inflamed

Skin, chilblains, painful

Skin, color, blue

Skin, cutting

Skin, desquamation

Skin, desquamation, hard

Skin, dryness

Skin, dryness, burning

Skin, eruptions, on covered parts

Skin, eruptions, blood-boils

Skin, eruptions, erysipelas

Skin, eruptions, erysipelas, gangrenous

Skin, eruptions, itch (scabies)

Skin, eruptions, itch (scabies), fatty

Skin, eruptions, itch (scabies), moist

Skin, eruptions, moist

SKIN, ERUPTIONS, PAINLESS

Skin, eruptions, scarlatina

Skin, eruptions, scarlatina, smooth

Skin, flabbiness

Skin, hard, with thickening

Skin, inactivity

Skin, indurations

Skin, inflammation

Skin, itching, in general

Skin, itching, crawling

Skin, itching, voluptuous

Skin, itching, after scratching, red streaks

Skin, itching, after scratching, scales

Skin, itching, after scratching, tension

Skin, spots, smarting

Skin, spots, stinging

Skin, spots, yellow

Skin, sticking

Skin, swelling, general, external

Skin, swelling, burning

Skin, swelling, cold

Skin, swelling, dropsical

Skin, swelling, spongy

Skin, tetter, yellowish

Skin, tightness

Skin, ulcers, biting

SKIN, ULCERS, BLACK

Skin, ulcers, black, at base

Skin, ulcers, bleeding

Skin, ulcers, bleeding, at edges

Skin, ulcers, bluish

SKIN, ULCERS, WITH BORING

Skin, ulcers, burning

Skin, ulcers, with cold feeling

SKIN, ULCERS, WITH CRAWLING

Skin, ulcers, with cutting

Skin, ulcers, deep

Skin, ulcers, fistulous

Skin, ulcers, foul

SKIN, ULCERS, WITH GNAWING PAIN

SKIN, ULCERS, INDOLENT

Skin, ulcers, inflamed

Skin, ulcers, surrounded by pimples

Skin, ulcers, pus, blackish

Skin, ulcers, pus, copious

Skin, ulcers, pus, corrosive

Skin, ulcers, pus, gray

Skin, ulcers, pus, offensive

Skin, ulcers, pus, offensive, like herring-brine

Skin, ulcers, pus, scanty

Skin, ulcers, pus, smelling sour

Skin, ulcers, pus, thin

Skin, ulcers, pus, yellow

SKIN, ULCERS, RED AREOLA

Skin, ulcers, reopening of old

Skin, ulcers, smarting

SKIN, ULCERS, SPONGY

SKIN, ULCERS, SPONGY, AT MARGINS

Skin, ulcers, spotted

Skin, ulcers, stinging

Skin, ulcers, stinging, in areola

Skin, ulcers, swollen

Skin, ulcers, swollen, areola

Skin, ulcers, swollen, margins

Skin, wounds, old wounds break out

Sleep, falling asleep, late

Sleep, falling asleep, prevented by various symptoms

Position in sleep, legs, stretched out

Position in sleep, legs, one stretched out, the other drawn up

Position in sleep, sitting

Sleep, sleepiness, during the day

Sleep, sleepiness, morning

Sleep, sleepiness, forenoon

Sleep, sleepiness, evening

Sleep, sleepiness, caused by various things

Sleep, restless

Sleep, stupid

Sleep, associated symptoms

Sleep, sleeplessness, in general

Dreams, anxious

Dreams, anxious, of thieves

Dreams, anxious, of water

Dreams, with indifference

Dreams, pleasant

Dreams, pleasant, of gold

DREAMS, VEXATIOUS

DREAMS, VEXATIOUS, OF VERMIN

CIRCULATION, BLOOD, BLOOD VESSELS, LIKE A NET-WORK

CIRCULATION, BLOOD, BLOOD VESSELS, PULSATION

CIRCULATION, BLOOD, BLOOD VESSELS, STITCHES

Circulation, pulse, abnormal in general

Circulation, pulse, full

Circulation, pulse, hard

CIRCULATION, PULSE, RAPID

Circulation, pulse, slow

Circulation, pulse, slower than the beat of the heart

Circulation, pulse, tremulous

Fever, chilliness, with thirst

FEVER, CHILLINESS, WITHOUT THIRST

FEVER, CHILLINESS, WITH TREMBLING

Fever, chilliness, symptoms during chill

FEVER, HEAT

FEVER, HEAT, INTERNALLY

Fever, heat, in special parts

Fever, heat, in special parts, externally

Fever, heat, anxious

FEVER, HEAT, WITH THIRST

Fever, heat, without thirst

Fever, heat, with inclination to uncover

Fever, heat, associated symptoms

Fever, coldness, of special parts

Fever, coldness, externally

FEVER, COLDNESS, ONE-SIDED

Fever, shivering, in general

Fever, sweat, posterior parts

Fever, sweat, with inclination to uncover

Fever, compound fever, chill, and heat at the same time

Fever, after fever

Fever, febrile symptoms, left side

Aggravations, during the day

Aggravations, morning

Aggravations, forenoon

Aggravations, afternoon

Aggravations, bathing

Aggravations, bathing, cold

Aggravations, bathing, sea

Aggravations, bending or turning

Aggravations, bent, holding the part

AGGRAVATIONS, BITING TEETH TOGETHER

Aggravations, blowing nose

Aggravations, change of weather

Aggravations, closing mouth

AGGRAVATIONS, CLOUDY WEATHER

Aggravations, drawing off boots

Aggravations, driving in a wagon

Aggravations, driving in a wagon, after

Aggravations, excitement, emotional

Aggravations, excitement, emotional, vexation

Aggravations, excitement, emotional, vexation, with fright

Aggravations, excitement, emotional, vexation, with quiet grief

Aggravations, exertion, physical

Aggravations, fatigue

Aggravations, food and drink, brandy

Aggravations, food and drink, cold

Aggravations, food and drink, oysters

Aggravations, hang down, letting limbs

AGGRAVATIONS, IDLENESS

Aggravations, looking, sideways

Aggravations, looking, at something turning around

Aggravations, looking, upward

Aggravations, after lying down

Aggravations, after lying down, on side

Aggravations, after lying down, on side, painless

Aggravations, micturition

Aggravations, moonlight

Aggravations, opening, mouth

Aggravations, organ, playing the

Aggravations, pressure, of hat

Aggravations, putting out the tongue

Aggravations, raising, eyes

Aggravations, raising, affected limb

Aggravations, rest

Aggravations, running

Aggravations, shaving

Aggravations, shooting

Aggravations, sitting down, on first

Aggravations, sitting, upright

Aggravations, society

Aggravations, squatting down

Aggravations, summer, in

AGGRAVATIONS, UNCLEANLINESS

Aggravations, unnatural position

Aggravations, wet, with sweat

Aggravations, wind

Ameliorations, bending or turning affected part

Ameliorations, bending, head backward

AMELIORATIONS, DRY WEATHER

Ameliorations, eating, on

Ameliorations, eating, after

Ameliorations, food and drink, water, cold

Ameliorations, light

Ameliorations, lying

Ameliorations, lying, on side

Ameliorations, lying, on side, left

Ameliorations, lying, on side, painful

Ameliorations, motion, continued

Ameliorations, pressure, external

Ameliorations, raising limbs

Ameliorations, rest

Ameliorations, rising up, from seat

Ameliorations, rising up, from seat, after

Ameliorations, stretching limbs

Ameliorations, sweat, cold

Ameliorations, talking

Ameliorations, walking

Ameliorations, walking, in open air

AMELIORATIONS, WARM

Ameliorations, warmth, in general

Ameliorations, warmth, of bed

AMELIORATIONS, WARMTH, OF THE STOVE

Abdomen

Abdominal rings

AGGRAVATIONS

Aggravations, exertion

Aggravations, food and drink

Aggravations, looking

Aggravations, moon

Aggravations, opening

Aggravations, pressure

Aggravations, raising

Aggravations, sitting

Aggravations, wet

Air-passages

Air-passages, voice

AMELIORATIONS

Ameliorations, bending

Ameliorations, eating

Ameliorations, food and drink

Ameliorations, food and drink, water

Ameliorations, motion

Ameliorations, rising up

Ameliorations, sweat

AMELIORATIONS, WARMTH

BACK

BONES

Bones, painfulness

CHEST

Chest, milk

Chest, palpitation, heart's action

CIRCULATION, BLOOD

CIRCULATION, BLOOD, BLOOD VESSELS

CIRCULATION

CIRCULATION, PULSE

COUGH

Cough, expectoration

Cough, taste of the expectoration

DREAMS

Ears

Ears, ear-wax

Eructations

External abdomen

External head

External throat and neck

EYES

FACE

Face, locations of sensations

FEVER

FEVER, CHILLINESS

FEVER, COLDNESS

Fever, compound fever, chill

Fever, compound fever

Fever, febrile symptoms

Fever, shivering

Fever, sweat

Flatulence

Flatulence, flatus

Glands

Hearing

Hearing, noises in ears

Hunger and thirst, aversion to

Hunger and thirst

Hunger and thirst, desire for

HYPOCHONDRIA

INTELLECT

INTERNAL ABDOMEN

INTERNAL HEAD

LOWER EXTREMITIES

Lower extremities, joints of lower extremities

Menstruation

Micturition

Micturition, troubles

Mind

Mouth, and fauces, left side, right side

MOUTH

Mouth, saliva

Nausea and vomiting

Nausea and vomiting, nausea in

Neck and nape of neck

Nose

Nose, nasal discharges

Position in sleep

Position in sleep, legs

RESPIRATION

SENSATIONS

Sensations, air

Sensations, burning

Sensations, clamp-like pains

Sensations, constriction

Sensations, cramps

Sensations, cutting

SENSATIONS, DROPSY

Sensations, heaviness

SENSATIONS, INFLAMMATION

Sensations, jerking

Sensations, motion

Sensations, numbness

Sensations, pain

Sensations, paralysis

Sensations, plug, sensation of

Sensations, pressing (simple pain)

Sensations, pressing

Sensations, pressing, tearing

Sensations, sensitiveness

Sensations, side (symptoms on one side), crosswise

Sensations, sore pain (smarting)

Sensations, sprained pain

Sensations, sticking

Sensations, sticking, pressing

Sensations, swellings

SENSATIONS, TEARING

SENSATIONS, TEARING, JERKING

Sensations, tearing, paralytic

Sensations, tearing, pressing

Sensations, tearing, sticking

SENSATIONS, TENSION

Sensations, throbbing

Sensations, trembling

Sensations, twitchings

Sexual organs, desire

Sexual organs

Sexual organs, female organs

Sexual organs, female organs, labor pains

Sexual organs, male organs

SKIN

Skin, color

SKIN, ERUPTIONS

Skin, hard

Skin, itching, after scratching

Skin, itching

Skin, spots

Skin, swelling

Skin, tetter

SKIN, ULCERS

Skin, ulcers, pus

Skin, wounds

Sleep

Sleep, falling asleep

Sleep, sleepiness

Sleep, sleeplessness

Smell, illusions of smell

Smell

STOOL

Stool, troubles

TASTE

Teeth

Upper extremities

Upper extremities, joints of upper extremities

Urinary organs

URINE

Vision

Vision, illusions of color