Chapter XXV: Part I: c. i (7)

From these circumstances of the extraneous light coinciding with the spontaneous efforts of the fatigued retina to produce a reverse spectrum, as was observed before, it is not easy to gain a direct spectrum, except of objects brighter than the ambient light; such as a candle in the night, the setting sun, or viewing a bright object through an opake tube; and then the reverse spectrum is instantaneously produced by the admission of some external light; and is as instantly converted again to the direct spectrum by the exclusion of it. Thus, on looking at the setting sun, on closing the eyes, and covering them, a yellow spectrum is seen, which is the direct spectrum of the setting sun; but on opening the eyes on the sky, the yellow spectrum is immediately changed into a blue one, which is the reverse spectrum of the yellow sun, or the direct spectrum of the blue sky, or a combination of both. And this is again transformed into a yellow one on closing the eyes, and so reciprocally, as quick as the motions of the opening and closing eyelids. Hence, when Mr. Melvill observed the scintillations of the star Sirius to be sometimes coloured, these were probably the direct spectrum of the blue sky on the parts of the retina fatigued by the white light of the star. (Essays Physical and Literary, p. 81. V. 2.)

When a direct spectrum is thrown on colours darker than itself, it mixes with them; as the yellow spectrum of the setting sun, thrown on the green grass, becomes a greener yellow. But when a direct spectrum is thrown on colours brighter than itself, it becomes instantly changed into the reverse spectrum, which mixes with those brighter colours. So the yellow spectrum of the setting sun thrown on the luminous sky becomes blue, and changes with the colour or brightness of the clouds on which it appears. But the reverse spectrum mixes with every kind of colour on which it is thrown, whether brighter than itself or not; thus the reverse spectrum, obtained by viewing a piece of yellow silk, when thrown on white paper, was a lucid blue green; when thrown on black Turkey leather, becomes a deep violet. And the spectrum of blue silk, thrown on white paper, was a light yellow; on black silk was an obscure orange; and, the blue spectrum, obtained from orange-coloured silk, thrown on yellow, became a green.

In these cases the retina is thrown into activity or sensation by the stimulus of external colours, at the same time that it continues the activity or sensation which forms the spectra; in the same manner as the prismatic colours, painted on a whirling top, are seen to mix together. When these colours of external objects are brighter than the direct spectrum which is thrown upon them, they change it into the reverse spectrum, like the admission of external light on a direct spectrum, as explained above. When they are darker than the direct spectrum, they mix with it, their weaker stimulus being inefficient to induce the reverse spectrum.

3. _Variation of spectra in respect to number, and figure, and remission._

When we look long and attentively at any object, the eye cannot always be kept entirely motionless; hence, on inspecting a circular area of red silk placed on white paper, a lucid crescent or edge is seen to librate on one side or other of the red circle: for the exterior parts of the retina sometimes falling on the edge of the central silk, and sometimes on the white paper, are less fatigued with red light than the central part of the retina, which is constantly, exposed to it; and therefore, when they fall on the edge of the red silk, they perceive it more vividly. Afterwards, when the eye becomes fatigued, a green spectrum in the form of a crescent is seen to librate on one side or other of the central circle, as by the unsteadiness of the eye a part of the fatigued retina falls on the white paper; and as by the increasing fatigue of the eye the central part of the silk appears paler, the edge on which the unfatigued part of the retina occasionally falls will appear of a deeper red than the original silk, because it is compared with the pale internal part of it. M. de Buffon in making this experiment observed, that the red edge of the silk was not only deeper coloured than the original silk; but, on his retreating a little from it, it became oblong, and at length divided into two, which must have been owing to his observing it either before or behind the point of intersection of the two optic axises. Thus, if a pen is held up before a distant candle, when we look intensely at the pen two candles are seen behind it; when we look intensely at the candle two pens are seen. If the sight be unsteady at the time of beholding the sun, even though one eye only be used, many images of the sun will appear, or luminous lines, when the eye is closed. And as some parts of these will be more vivid than others, and some parts of them will be produced nearer the center of the eye than others, these will disappear sooner than the others; and hence the number and shape of these spectra of the sun will continually vary, as long as they exist. The cause of some being more vivid than others, is the unsteadiness of the eye of the beholder, so that some parts of the retina have been longer exposed to the sunbeams. That some parts of a complicated spectrum fade and return before other parts of it, the following experiment evinces. Draw three concentric circles; the external one an inch and a half in diameter, the middle one an inch, and the internal one half an inch; colour the external and internal areas blue, and the remaining one yellow, as in Fig. 4.; after having looked about a minute on the center of these circles, in a bright light, the spectrum of the external area appears first in the closed eye, then the middle area, and lastly the central one; and then the central one disappears, and the others in inverted order. If concentric circles of more colours are added, it produces the beautiful ever changing spectrum in Sect. I. Exp. 2.

From hence it would seem, that the center of the eye produces quicker remissions of spectra, owing perhaps to its greater sensibility; that is, to its more energetic exertions. These remissions of spectra bear some analogy to the tremors of the hands, and palpitations of the heart, of weak people: and perhaps a criterion of the strength of any muscle or nerve may be taken from the time it can be continued in exertion.

4. _Variation of spectra in respect to brilliancy; the visibility of the circulation of the blood in the eye._

1. The meridian or evening light makes a difference in the colours of some spectra; for as the sun descends, the red rays, which are less refrangible by the convex atmosphere, abound in great quantity. Whence the spectrum of the light parts of a window at this time, or early in the morning, is red; and becomes blue either a little later or earlier; and white in the meridian day; and is also variable from the colour of the clouds or sky which are opposed to the window.

2. All these experiments are liable to be confounded, if they are made too soon after each other, as the remaining spectrum will mix with the new ones. This is a very troublesome circumstance to painters, who are obliged to look long upon the same colour; and in particular to those whose eyes, from natural debility, cannot long, continue the same kind of exertion. For the same reason, in making these experiments, the result becomes much varied if the eyes, after viewing any object, are removed on other objects for but an instant of time, before we close them to view the spectrum; for the light from the object, of which we had only a transient view, in the very time of closing our eyes acts as a stimulus on the fatigued retina; and for a time prevents the defined spectrum from appearing, or mixes its own spectrum with it. Whence, after the eyelids are closed, either a dark field, or some unexpected colours, are beheld for a few seconds, before the desired spectrum becomes distinctly visible.

3. The length of time taken up in viewing an object, of which we are to observe the spectrum, makes a great difference in the appearance of the spectrum, not only in its vivacity, but in its colour; as the direct spectrum of the central object, or of the circumjacent ones, and also the reverse spectra of both, with their various combinations, as well as the time of their duration in the eye, and of their remissions or alternations, depend upon the degree of fatigue the retina is subjected to. The Chevalier d'Arcy constructed a machine by which a coal of fire was whirled round in the dark, and found, that when a luminous body made a revolution in eight thirds of time, it presented to the eye a complete circle of fire; from whence he concludes, that the impression continues on the organ about the seventh part of a second. (Mem. de l'Acad. des Sc. 1765.) This, however, is only to be considered as the shortest time of the duration of these direct spectra; since in the fatigued eye both the direct and reverse spectra, with their intermissions, appear to take up many seconds of time, and seem very variable in proportion to the circumstances of fatigue or energy.

4. It sometimes happens, if the eyeballs have been rubbed hard with the fingers, that lucid sparks are seen in quick motion amidst the spectrum we are attending to. This is similar to the flashes of fire from a stroke on the eye in fighting, and is resembled by the warmth and glow, which appears upon the skin after friction, and is probably owing to an acceleration of the arterial blood into the vessels emptied by the previous pressure. By being accustomed to observe such small sensations in the eye, it is easy to see the circulation of the blood in this organ. I have attended to this frequently, when I have observed my eyes more than commonly sensible to other spectra. The circulation may be seen either in both eyes at a time, or only in one of them; for as a certain quantity of light is necessary to produce this curious phenomenon, if one hand be brought nearer the closed eyelids than the other, the circulation in that eye will for a time disappear. For the easier viewing the circulation, it is sometimes necessary to rub the eyes with a certain degree of force after they are closed, and to hold the breath rather longer than is agreeable, which, by accumulating more blood in the eye, facilitates the experiment; but in general it may be seen distinctly after having examined other spectra with your back to the light, till the eyes become weary; then having covered your closed eyelids for half a minute, till the spectrum is faded away which you were examining, turn your face to the light, and removing your hands from the eyelids, by and by again shade them a little, and the circulation becomes curiously distinct. The streams of blood are however generally seen to unite, which shews it to be the venous circulation, owing, I suppose, to the greater opacity of the colour of the blood in these vessels; for this venous circulation is also much more easily seen by the microscope in the tail of a tadpole.

5. _Variation of spectra in respect to distinctness and size; with a new way of magnifying objects._

1. It was before observed, that when the two colours viewed together were opposite to each other, as yellow and blue, red and green, &c. according to the table of reflections and transmissions of light in Sir Isaac Newton's Optics, B. II. Fig. 3. the spectra of those colours were of all others the most brilliant, and best defined; because they were combined of the reverse spectrum of one colour, and of the direct spectrum of the other. Hence, in books printed with small types, or in the minute graduation of thermometers, or of clock-faces, which are to be seen at a distance, if the letters or figures are coloured with orange, and the ground with indigo; or the letters with red, and the ground with green; or any other lucid colour is used for the letters, the spectrum of which is similar to the colour of the ground; such letters will be seen much more distinctly, and with less confusion, than in black or white: for as the spectrum of the letter is the same colour with the ground on which they are seen, the unsteadiness of the eye in long attending to them will not produce coloured lines by the edges of the letters, which is the principal cause of their confusion. The beauty of colours lying in vicinity to each other, whose spectra are thus reciprocally similar to each colour, is owing to this greater ease that the eye experiences in beholding them distinctly; and it is probable, in the organ of hearing, a similar circumstance may constitute the pleasure of melody. Sir Isaac Newton observes, that gold and indigo were agreeable when viewed together; and thinks there may be some analogy between the sensations of light and sound. (Optics, Qu. 14.)

In viewing the spectra of bright objects, as of an area of red silk of half an inch diameter on white paper, it is easy to magnify it to tenfold its size: for if, when the spectrum is formed, you still keep your eye fixed on the silk area, and remove it a few inches further from you, a green circle is seen round the red silk: for the angle now subtended by the silk is less than it was when the spectrum was formed, but that of the spectrum continues the same, and our imagination places them at the same distance. Thus when you view a spectrum on a sheet of white paper, if you approach the paper to the eye, you may diminish it to a point; and if the paper is made to recede from the eye, the spectrum will appear magnified in proportion to the distance.

I was surprised, and agreeably amused, with the following experiment. I covered a paper about four inches square with yellow, and with a pen filled with a blue colour wrote upon the middle of it the word BANKS in capitals, as in Fig. 5, and sitting with my back to the sun, fixed my eyes for a minute exactly on the center of the letter N in the middle of the word; after closing my eyes, and shading them somewhat with my hand, the word was distinctly seen in the spectrum in yellow letters on a blue field; and then, on opening my eyes on a yellowish wall at twenty feet distance, the magnified name of BANKS appeared written on the wall in golden characters.

_Conclusion._

It was observed by the learned M. Sauvage (Nosol. Method. Cl. VIII. Ord. i.) that the pulsations of the optic artery might be perceived by looking attentively on a white wall well illuminated. A kind of net-work, darker than the other parts of the wall, appears and vanishes alternately with every pulsation. This change of the colour of the wall he well ascribes to the compression of the retina by the diastole of the artery. The various colours produced in the eye by the pressure of the finger, or by a stroke on it, as mentioned by Sir Isaac Newton, seem likewise to originate from the unequal pressure on various parts of the retina. Now as Sir Isaac Newton has shewn, that all the different colours are reflected or transmitted by the laminæ of soap bubbles, or of air, according to their different thickness or thinness, is it not probable, that the effect of the activity of the retina may be to alter its thickness or thinness, so as better to adapt it to reflect or transmit the colours which stimulate it into action? May not muscular fibres exist in the retina for this purpose, which may be less minute than the locomotive muscles of microscopic animals? May not these muscular actions of the retina constitute the sensation of light and colours; and the voluntary repetitions of them, when the object is withdrawn, constitute our memory of them? And lastly, may not the laws of the sensations of light, here investigated, be applicable to all our other senses, and much contribute to elucidate many phenomena of animal bodies both in their healthy and diseased state; and thus render this investigation well worthy the attention of the physician, the metaphysician, and the natural philosopher?

November 1, 1785.

* * * * *

Dum, Liber! astra petis volitans trepidantibus alis,
Irruis immemori, parvula gutta, mari.
Me quoque, me currente rotâ revolubilis ætas
Volverit in tenebras,--i, Liber, ipse sequor.

* * * * *

INDEX TO THE SECTIONS OF PART FIRST.

A.

Abortion from fear, xxxix. 6. 5.
Absorbent vessels, xxiii. 3. xxix. 1.
---- regurgitate their fluids, xxix. 2.
---- their valves, xxix. 2.
---- communicate with vena portarum, xxvii. 2.
Absorption of solids, xxxiii. 3. 1. xxxvii.
---- of fluids in anasarca, xxxv. 1. 3.
Accumulation of sensorial power, iv. 2. xii. 5. 2.
Activity of system too great, cure of, xii. 6.
---- too small, cure of, xii. 7.
Age, old, xii. 3. 1. xxxvii. 4.
Ague-fit, xii. 7. 1. xxxii. 3. 4. xxxii. 9.
---- how cured by bark, xii. 3. 4.
---- periods, how occasioned, xii. 2. 3. xxxii. 3. 4.
Ague cakes, xxxii. 7. xxxii. 9.
Air, sense of fresh, xiv. 8.
---- injures ulcers, xxviii. 2.
---- injected into veins, xxxii. 5.
Alcohol deleterious, xxx. 3.
Alliterations, why agreeable, xxii. 2.
Aloes in lessened doses, xii. 3. 1.
American natives indolent, xxxi. 2.
---- narrow shouldered, xxxi. 1.
Analogy intuitive, xvii. 3. 7.
Animals less liable to madness, xxxiii. 1.
---- less liable to contagion, xxxiii. 1.
---- how to teach, xxii. 3. 2.
---- their similarity to each other, xxxix. 4. 8.
---- their changes after nativity, xxxix. 4. 8.
---- their changes before nativity, xxxix. 4. 8.
---- less liable to contagious diseases, why, xxxiii. 1. 5.
---- less liable to delirium and insanity, why, xxxiii. 1. 5.
---- easier to preserve than to reproduce, xxxvii.
---- food, distaste of, xxviii. 1.
---- appetency, xxxix. 4. 7.
Antipathy, x. 2. 2.
Aphthæ, xxviii.
Apoplexy, xxxiv. 1. 7.
---- not from deficient irritation, xxxii. 2. 1.
Appetites, xi. 2. 2. xiv. 8.
Architecture, xxii. 2. xvi. 10.
Arts, fine, xxii. 2.
Asparagus, its smell in urine, xxix.
Association defined, ii. 2. 11. iv. 7. v. 2.
---- associate motions, x.
---- stronger than irritative ones, xxiv. 2. 8.
---- formed before nativity, xi. 3.
---- with irritative ones, xxiv. 2. 8.
---- with retrograde ones, xxv. 7. xxv. 10. xxv. 15.
---- diseases from, xxxv.
Asthma, xviii. 15.
Attention, language of, xvi. 8. 6.
Atrophy, xxviii.
Aversion, origin of, xi. 2. 3.

B.

Balance ourselves by vision, xx. 1.
Bandage increases absorption, xxxiii. 3. 2.
Barrenness, xxxvi. 2. 3.
Battement of sounds, xx. 7.
Bath, cold. See Cold Bath.
Beauty, sense of, xvi. 6. xxii. 2.
Bile-ducts, xxx.
---- stones, xxx. 1. 3.
---- regurgitates into the blood, xxiv. 2. 7.
---- vomiting of, xxx. 1. 3.
Birds of passage, xvi. 12.
---- nests of, xvi. 13.
---- colour of their eggs, xxxix. 5.
Biting in pain, xxxiv. 1. 3.
---- of mad animals, xxxiv. 1. 3.
Black spots on dice appear red, xl. 3.
Bladder, communication of with the intestines, xxix. 3.
---- of fish, xxiv. 1. 4.
Blood, transfusion of in nervous fevers, xxxii. 4.
---- deficiency of, xxxii. 2. and 4.
---- from the vena portarum into the intestines, xxvii. 2.
---- its momentum, xxxii. 5. 2.
---- momentum increased by venesection, xxxii. 5. 4.
---- drawn in nervous pains, xxxii. 5. 4.
---- its oxygenation, xxxviii.
Breasts of men, xiv. 8.
Breathing, how learnt, xvi. 4.
Brutes differ from men, xi. 2. 3. xvi. 17.
Brutes. See Animals.
Buxton bath, why it feels warm, xii. 2. 1. xxxii. 3. 3.

C.

Capillary vessels are glands, xxvi. 1.
Catalepsy, xxxiv. 1. 5.
Catarrh from cold skin, xxxv. 1. 3. xxxv. 2. 3.
---- from thin caps in sleep, xviii. 15.
Catenation of motions defined, ii. 2. 11. iv. 7.
---- cause of them, xvii. 1. 3.
---- described, xvii.
---- continue some time after their production, xvii. 1. 3.
---- voluntary ones dissevered in sleep, xvii. 1. 12. xvii. 3. 7.
Cathartics, external, their operation, xxix. 7. 6.
Causation, animal, defined, ii. 2. 11. iv. 7.
Cause of causes, xxxix. 4. 8.
Causes inert and efficient, xxxix. 8. 2.
---- active and passive, xxxix. 8. 3.
---- proximate and remote, xxxix. 8. 4.
Chick in the egg, oxygenation of, xxxviii. 2.
Child riding on a stick, xxxiv. 2. 6.
Chilness after meals, xxi. 3. xxxv. 1. 1.
Cholera, case of, xxv. 13.
Circulation in the eye visible, xl. 10. 4.
Cold in the head, xii. 6. 5.
---- perceived by the teeth, xxxii. 3. 1. xiv. 6.
---- air, uses of in fevers, xxxii. 3. 3.
---- feet, produces coryza, xxxv. 2. 3. xxxv. 1. 3.
---- bath, why it strengthens, xxxii. 3. 2.
---- short and cold breathing in it, xxxii. 3. 2.
---- produces a fever-fit, xxxii. 3. 2.
---- fit of fever the consequence of hot fit, xxxii. 9. 3.
---- bathing in pulmonary hæmorrhage, xxvii. 1.
---- fits of fever, xxxii. 4. xxxii. 9. xvii. 3. 3.
Colours of animals, efficient cause of, xxxix. 5. 1.
---- of eggs from female imagination, xxxix. 5. 1.
---- of the choroid coat of the eye, xxxix. 5. 1.
---- of birds nests, xvi. 13.
Comparing ideas, xv. 3.
Consciousness, xv. 3. 4.
---- in dreams, xviii. 13.
Consent of parts. See Sympathy.
Consumption, its temperament, xxxi. 1. and 2.
---- of dark-eyed patients, xxvii. 2.
---- of light-eyed patients, xxviii. 2.
---- is contagious, xxxiii. 2. 7.
Contagion, xii. 3. 6. xix. 9. xxxiii. 2. 6. and 8. xxii. 3. 3.
---- does not enter the blood, xxxiii. 2. 10. xxii. 3. 3.
Contraction and attraction, iv. 1.
---- of fibres produces sensation, iv. 5. xii. 1. 6.
---- continues some time, xii. 1. 5.
---- alternates with relaxation, xii. 1. 3.
Convulsion, xvii. 1. 8. xxxiv. 1. 1. and 4. iii. 5. 8.
---- of particular muscles, xvii. 1. 8.
---- periods of, xxxvi. 3. 9.
Coryza. See Catarrh.
Cough, nervous, periods of, xxxvi. 3. 9.
Cramp, xviii. 15. xxxiv. 1. 7.
Critical days from lunations, xxxvi. 4.

D.

Darkish room, why we see well in it, xii. 2. 1.
Debility sensorial and stimulatory, xii. 2. 1.
---- direct and indirect of Dr. Brown, xii. 2. 1. xxxii. 3. 2.
---- See Weakness.
---- from drinking spirits, cure of, xii. 7. 8.
---- in fevers, cure of, xii. 7. 8.
Deliberation, what, xxxiv. 1.
Delirium, two kinds of, xxxiii. 1. 4. xxxiv. 2. 2.
---- cases of, iii. 5. 8.
---- prevented by dreams, xviii. 2.
Desire, origin of, xi. 2. 3.
Diabetes explained, xxix. 4.
---- with bloody urine, xxvii. 2.
---- in the night, xviii. 15.
Diarrhoea, xxix. 4.
Digestion, xxxiii. 1. xxxvii.
---- strengthened by emetics, xxxv. 1. 3.
---- strengthened by regular hours, why, xxxvi. 2. 1.
Digitalis, use of in dropsy, xxix. 5. 2.
Distention acts as a stimulus, xxxii. 4.
---- See Extension.
Distinguishing, xv. 3.
Diurnal circle of actions, xxv. 4.
Doubting, xv. 3.
Dreams, viii. 1. 2. xiv. 2. 5.
---- their inconsistency, xviii. 17.
---- no surprise in them, xviii. 17.
---- much novelty of combination, xviii. 9.
Dropsies explained, xxix. 5. 1.
Dropsy cured by insanity, xxxiv. 2. 7.
---- cure of, xxix. 5. 2.
Drunkards weak till next day, xvii. 1. 7.
---- stammer, and stagger, and weep, xii. 4. 1. xxi. 4.
---- see objects double, why, xxi. 7.
---- become delirious, sleepy, stupid, xxi. 5.
Drunkenness. See Intoxication, xxi.
---- diminished by attention, xxi. 8.
Dyspnoea in cold bath, xxxii. 3. 2.

E.

Ear, a good one, xvi. 10.
---- noise in, xx. 7.
Eggs of frogs, fish, fowl, xxxix. 2.
---- of birds, why spotted, xxxix. 5.
---- with double yolk, xxxix. 4. 4.
Electricity, xii. 1. xiv. 9.
---- jaundice cured by it, xxx. 1. 2.
Embryon produced by the male, xxxix. 2.
---- consists of a living fibre, xxxix. 4.
---- absorbs nutriment, receives oxygen, xxxix. 1.
---- its actions and sensations, xvi. 2.
Emetic. See Vomiting.
Emotions, xi. 2. 2.
Ennui, or tædium vitæ, xxxiv. 2. 3. xxxiii. 1. 1. xxxix. 6.
Epileptic fits explained, xxxiv. 1. 4. xxvii. 2.
---- in sleep, why, xviii. 14. & 15.
Equinoxial lunations, xxxii. 6.
Excitability perpetually varies, xii. 1. 7.
---- synonymous to quantity of sensorial power, xii. 1. 7.
Exercise, its use, xxxii. 5. 3.
Exertion of sensorial power defined, xii. 2. 1.
Existence in space, xiv. 2. 5.
Extension, sense of, xiv. 7.
Eyes become black in some epilepsies, xxvii. 2.

F.

Face, flushing of after dinner, xxxv. 1. 1.
---- why first affected in small-pox, xxxv. 1. 1.
---- red from inflamed liver, xxxv. 2. 2.
Fainting fits, xii. 7. 1. xiv. 7.
Fear, language of, xvi. 8. 1.
---- a cause of fever, xxxii. 8.
---- cause of, xvii. 3. 7.
Fetus. See Embryon, xvi. 2. xxxix. 1.
Fevers, irritative, xxxii. 1.
---- intermittent, xxxii. 1. xxxii. 3.
---- sensitive, xxxiii. 1.
---- not an effort of nature for relief, xxxii. 10.
---- paroxysms of, xii. 7. 1. xii. 2. 3. xii. 3. 5.
---- why some intermit and not others, xxxvi. 1.
---- cold fits of, xxxii. 4. xxxii. 9. xvii. 3. 3.
---- periods of, xxxvi. 3.
---- have solar or lunar periods, xxxii. 6.
---- source of the symptoms of, xxxii. 1.
---- prostration of strength in, xii. 4. 1. xxxii. 3. 2.
---- cure of, xii. 6. 1.
---- how cured by the bark, xii. 3. 4.
---- cured by increased volition, xii. 2. 4. xxxiv. 2. 8.
---- best quantity of stimulus in, xii. 7. 8.
Fibres. See Muscles.
Fibres, their mobility, xii. 1. 7. xii. 1. 1.
---- contractions of, vi. xii. 1. 1.
---- four classes of their motions, vi.
---- their motions distinguished from sensorial ones, v. 3.
Figure, xiv. 2. 2. iii. 1.
Fish, their knowledge, xvi. 14.
Foxglove, its use in dropsies, xxix. 5. 2.
---- overdose of, xxv. 17.
Free-will, xv. 3. 7.

G.

Gall-stone, xxv. 17.
---- See Bile-stones.
Generation, xxxiii. 1. xxxix.
Gills of fish, xxxviii. 2.
Glands, xxiii. 2.
---- conglobate glands, xxiii. 3.
---- have their peculiar stimulus, xi. 1.
---- their senses, xiv. 9. xxxix. 6.
---- invert their motions, xxv. 7.
---- increase their motions, xxv. 7.
Golden rule for exhibiting wine, xii. 7. 8.
---- for leaving off wine, xii. 7. 8.
Gout from inflamed liver, xxxv. 2. 2. xviii. 16. xxiv. 2. 8.
---- in the stomach, xxiv. 2. 8. xxv. 17.
---- why it returns after evacuations, xxxii. 4.
---- owing to vinous spirit only, xxi. 10.
---- periods of, xxxvi. 3. 6.
Grinning in pain, xxxiv. 1. 3.
Gyration on one foot, xx. 5. and 6.

H.

Habit defined, ii. 2. 11. iv. 7.
Hæmorrhages, periods of, xxxvi. 3. 11.
---- from paralysis of veins, xxvii. 1. and 2.
Hair and nails, xxxix. 3. 2.
---- colour of, xxxix. 5. 1.
Harmony, xxii. 2.
Head-achs, xxxv. 2. 1.
Hearing, xiv. 4.
Heat, sense of, xiv. 6. xxxii. 3. 1.
---- produced by the glands, xxxii. 3.
---- external and internal, xxxii. 3. 1.
---- atmosphere of heat, xxxii. 3. 1.
---- increases during sleep, xviii. 15.
Hemicrania, xxxv. 2. 1.
---- from decaying teeth, xxxv. 2. 1.
Hepatitis, cause of, xxxv. 2. 3.
Hereditary diseases, xxxix. 7. 6.
Hermaphrodite insects, xxxix. 5.
Herpes, xxviii. 2.
---- from inflamed kidney, xxxv. 2. 2.
Hilarity from diurnal fever, xxxvi. 3. 1.
Hunger, sense of, xiv. 8.
Hydrophobia, xxii. 3. 3.
Hypochondriacism, xxxiii. 1. 1. xxxiv. 2. 3.

I.

Ideas defined, ii. 2. 7.
---- are motions of the organs of sense, iii. 4. xviii. 5. xviii. 10.
xviii. 6.
---- analogous to muscular motions, iii. 5.
---- continue some time, xx. 6.
---- new ones cannot be invented, iii. 6. 1.
---- abstracted ones, iii. 6. 4.
---- inconsistent trains of, xviii. 17.
---- perish with the organ of sense, iii. 4. 4.
---- painful from inflammation of the organ, iii. 5. 5.
---- irritative ones, vii. 1. 4. vii. 3. 2. xv. 2. xx. 7.
---- of resemblance, contiguity, causation, viii. 3. 2. x. 3. 3.
---- resemble the figure and other properties of bodies, xiv. 2. 2.
---- received in tribes, xv. 1.
---- of the same sense easier combined, xv. 1. 1.
---- of reflection, xv. 1. 6. ii. 2. 12.
Ideal presence, xv. 1. 7.
Identity, xv. 3. 5. xviii. 13.
Iliac passion, xxv. 15.
Imagination, viii. 1. 2. xv. 1. 7. xv. 2. 2.
---- of the male forms the sex, xxxix. 6.
Imitation, origin of, xii. 3. 3. xxxix. 5. xxii. 3. xvi. 7.
Immaterial beings, xiv. 1. xiv. 2. 4.
Impediment of speech, xvii. 1. 10. xvii. 2. 10.
Infection. See Contagion.
Inflammation, xii. 2. 3. xxxiii. 2. 2.
---- great vascular exertion in, xii. 2. 1.
---- not from pains from defect of stimulus, xxxiii. 2. 3.
---- of parts previously insensible, xii. 3. 7.
---- often distant from its cause, xxiv. 2. 8.
---- observes solar days, xxxii. 6.
---- of the eye, xxxiii. 3. 1.
---- of the bowels prevented by their continued action in sleep, xviii.
2.
Inoculation with blood, xxxiii. 2. 10.
Insane people, their great strength, xii. 2. 1.
Insanity (see Madness) pleasurable one, xxxiv. 2. 6.
Insects, their knowledge, xvi. 15. and 16.
---- in the heads of calves, xxxix. 1.
---- class of, xxxix. 4. 8.
Instinctive actions defined, xvi. 1.
Intestines, xxv. 3.
Intoxication relieves pain, why, xxi. 3.
---- from food after fatigue, xxi. 2.
---- diseases from it, xxi. 10.
---- See Drunkenness.
Intuitive analogy, xvii. 3. 7.
Invention, xv. 3. 3.
Irritability increases during sleep, xviii. 15.
Itching, xiv. 9.

J.

Jaundice from paralysis of the liver, xxx. 1. 2.
---- cured by electricity, xxx. 1. 2.
Jaw-locked, xxxiv. 1. 5.
Judgment, xv. 3.

K.

Knowledge of various animals, xvi. 11.

L.

Lachrymal sack, xvi. 8. xxiv. 2. 2. and 7.
Lacteals, paralysis of, xxviii.
---- See Absorbents.
Lady playing on the harpsichord, xvii. 2.
---- distressed for her dying bird, xvii. 2. 10.
Language, natural, its origin, xvi. 7. & 8.
---- of various passions described, xvi. 8.
---- artificial, of various animals, xvi. 9.
---- theory of, xxxix. 8. 3.
Lapping of puppies, xvi. 4.
Laughter explained, xxxiv. 1. 4.
---- from tickling, xvii. 3. 5. xxxiv. 1. 4.
---- from frivolous ideas, xxxiv. 1. 4. xviii. 12.
Life, long, art of producing, xxxvii.
Light has no momentum, iii. 3. 1.
Liquor amnii, xvi. 2. xxxviii. 2.
---- is nutritious, xxxviii. 3.
---- frozen, xxxviii. 3.
Liver, paralysis of, xxx. 1. 4.
---- large of geese, xxx. 1. 6.
Love, sentimental, its origin, xvi. 6.
---- animal, xiv. 8. xvi. 5.
Lunar periods affect diseases, xxxii. 6.
Lust, xiv. 8. xvi. 5.
Lymphatics, paralysis of, xxviii.
---- See Absorbents.

M.

Mad-dog, bite of, xxii. 3. 3.
Madness, xxxiv. 2. 1. xii. 2. 1.
Magnetism, xii. 1. 1.
Magnifying objects, new way of, xl. 10. 5.
Male animals have teats, xxxix. 4. 8.
---- pigeons give milk, xxxix. 4. 8.
Man distinguished from brutes, xi. 2. 3. xvi. 17.
Material world, xiv. 1. xiv. 2. 5. xviii. 7.
Matter, penetrability of, xiv. 2. 3.
---- purulent, xxxiii. 2. 4.
Measles, xxxiii. 2. 9.
Membranes, xxvi. 2.
Memory defined, ii. 2. 10. xv. 1. 7. xv. 3.
Menstruation by lunar periods, xxxii. 6.
Miscarriage from fear, xxxix. 6. 5.
Mobility of fibres, xii. 1. 7.
Momentum of the blood, xxxii. 5. 2.
---- sometimes increased by venesection, xxxii. 5. 4.
Monsters, xxxix. 4. 4. and 5. 2.
---- without heads, xxxviii. 3.
Moon and sun, their influence, xxxii. 6.
Mortification, xxxiii. 3. 3.
Motion is either cause or effect, i. xiv. 2. 2.
---- primary and secondary, i.
---- animal, i. iii. 1.
---- propensity to, xxii. 1.
---- animal, continue some time after their production, xvii. 1. 3.
---- defined, a variation of figure, iii. 1. xiv. 2. 2. xxxix. 8.
Mucus, experiments on, xxvi. 1.
---- secretion of, xxvi. 2.
Mules, xxxix. 4. 5. and 6. xxxix. 5. 2.
Mule plants, xxxix. 2.
Muscæ volitantes, xl. 2.
Muscles constitute an organ of sense, xiv. 7. ii. 2. 4.
---- stimulated by extension, xi. 1. xiv. 7.
---- contract by spirit of animation, xii. 1. 1. and 3.
Music, xvi. 10. xxii. 2.
Musical time, why agreeable, xii. 3. 3.

N.

Nausea, xxv. 6.
Nerves and brain, ii. 2. 3.
---- extremities of form the whole system, xxxvii. 3.
---- are not changed with age, xxxvii. 4.
Nervous pains defined, xxxiv. 1. 1.
Number defined, xiv. 2. 2.
Nutriment for the embryon, xxxix. 5. 2.
Nutrition owing to stimulus, xxxvii. 3.
---- by animal selection, xxxvii. 3.
---- when the fibres are elongated, xxxvii. 3.
---- like inflammation, xxxvii. 3.

O.

Objects long viewed become faint, iii. 3. 2.
Ocular spectra, xl.
Oil externally in diabætes, xxix. 4.
Old age from inirritability, xxxvii.
Opium is stimulant, xxxii. 2. 2.
---- promotes absorption after evacuation, xxxiii. 3. 1.
---- in increasing doses, xii. 3. 1.
Organs of sense, ii. 2. 5. and 6.
Organs when destroyed cease to produce ideas, iii. 4. 4.
Organic particles of Buffon, xxxvii. 3. xxxix. 3. 3.
Organ-pipes, xx. 7.
Oxygenation of the blood, xxxviii.

P.

Pain from excess and defect of motion, iv. 5. xii. 5. 3. xxxiv. 1. xxxv.
2. 1.
---- not felt during exertion, xxxiv. 1. 2.
---- from greater contraction of fibres, xii. 1. 6.
---- from accumulation of sensorial power, xii. 5. 3.
---- from light, pressure, heat, caustics, xiv. 9.
---- in epilepsy, xxxv. 2. 1.
---- distant from its cause, xxiv. 2. 8.
---- from stone in the bladder, xxxv. 2. 1.
---- of head and back from defect, xxxii. 3.
---- from a gall-stone, xxxv. 2. 1. xxv. 17.
---- of the stomach in gout, xxv. 17.
---- of shoulder in hepatitis, xxxv. 2. 4.
---- produces volition, iv. 6.
Paleness in cold fit, xxxii. 3. 2.
Palsies explained, xxxiv. 1. 7.
Paralytic limbs stretch from irritation, vii. 1. 3.
---- patients move their sound limb much, xii. 5. 1.
Paralysis from great exertion, xii. 4. 6.
---- from less exertion, xii. 5. 6.
---- of the lacteals, xxviii.
---- of the liver, xxx. 1. 4.
---- of the right arm, why, xxxiv. 1. 7.
---- of the veins, xxvii. 2.
Particles of matter will not approach, xii. 1. 1.
Passions, xi. 2. 2.
---- connate, xvi. 1.
Pecking of chickens, xvi. 4.
Perception defined, ii. 2. 8. xv. 3. 1.
Periods of agues, how formed, xxxii. 3. 4.
---- of diseases, xxxvi.
---- of natural actions and of diseased actions, xxxvi.
Perspiration in fever-fits, xxxii. 9. See Sweat.
Petechiæ, xxvii. 2.
Pigeons secrete milk in their stomachs, xxxix. 4. 8.
Piles, xxvii. 2.
Placenta a pulmonary organ, xxxviii. 2.
Pleasure of life, xxxiii. 1. xxxix. 5.
---- from greater fibrous contractions, xii. 1. 6.
---- what kind causes laughter, xxxiv. 1. 4.
---- what kind causes sleep, xxxiv. 1. 4.
Pleurisy, periods of, xxxvi. 3. 7.
---- cause of, xxxv. 2. 3.
Prometheus, story of, xxx. 3.
Prostration of strength in fevers, xii. 4. 1.
Pupils of the eyes large, xxxi. 1.
Pulse quick in fevers with debility, xii. 1. 4. xii. 5. 4. xxxii. 2. 1.
---- in fevers with strength, xxxii. 2.
---- from defect of blood, xxxii. 2. 3. xii. 1. 4.
---- weak from emetics, xxv. 17.

Q.

Quack advertisements injurious. Preface.
Quadrupeds have no sanguiferous lochia, xxxviii. 2.
---- have nothing similar to the yolk of egg, xxxix. 1.

R.

Rhaphania, periods of, xxxvi. 3. 9.
Reason, ix. 1. 2. xv. 3.
Reasoning, xv. 3.
Recollection, ii. 2. 10. ix. 1. 2. xv. 2. 3.
Relaxation and bracing, xxxii. 3. 2.
Repetition, why agreeable, xii. 3. 3. xxii. 2.
Respiration affected by attention, xxxvi. 2. 1.
Restlessness in fevers, xxxiv. 1. 2.
Retrograde motions, xii. 5. 5. xxv. 6. xxix. 11.
---- of the stomach, xxv. 6.
---- of the skin, xxv. 9.
---- of fluids, how distinguished, xxix. 8.
---- how caused, xxix. 11. 5.
---- vegetable motions, xxix. 9.
Retina is fibrous, iii. 2. xl. 1.
---- is active in vision, iii. 3. xl. 1.
---- excited into spasmodic motions, xl. 7.
---- is sensible during sleep, xviii. 5. xix. 8.
Reverie, xix. 1. xxxiv. 3.
---- case of a sleep-walker, xix. 2.
---- is an epileptic disease, xix. 9.
Rhymes in poetry, why agreeable, xxii. 2.
Rheumatism, three kinds of, xxvi. 3.
Rocking young children, xxi. 3.
Ruminating animals, xxv. 1.

S.

Saliva produced by mercury, xxiv. 1.
---- by food, xxiv. 1. 1.
---- by ideas, xxiv. 1. 2. and 5.
---- by disordered volition, xxiv. 1. 7.
Schirrous tumours revive, xii. 2. 2.
Screaming in pain, xxxiv. 1. 3.
Scrophula, its temperament, xxxi. 1.
---- xxviii. 2. xxxix. 4. 5.
Scurvy of the lungs, xxvii. 2.
Sea-sickness, xx. 4.
---- stopped by attention, xx. 5.
Secretion, xxxiii. 1. xxxvii.
---- increased during sleep, xviii. 16.
Seeds require oxygenation, xxxviii. 2.
Sensation defined, ii. 2. 9. v. 2. xxxix. 8. 4.
---- diseases of, xxxiii.
---- from fibrous contractions, iv. 5. xii. 1. 6.
---- in an amputated limb, iii. 6. 3.
---- affects the whole sensorium, xi. 2.
---- produces volition, iv. 6.
Sensibility increases during sleep, xviii. 15.
Sensitive motions, viii. xxxiii. 2. xxxiv. 1.
---- fevers of two kinds, xxxiii. 1. 2.
---- ideas, xv. 2. 2.
Sensorium defined, ii. 2. 1.
Senses correct one another, xviii. 7.
---- distinguished from appetites, xxxiv. 1. 1.
Sensorial power. See Spirit of Animation.
---- great expence of in the vital motions, xxxii. 3. 2.
---- two kinds of excited in sensitive fevers, xxxiii. 1. 3.
---- powers defined, v. 1.
---- motions distinguished from fibrous motions, v. 3.
---- not much, accumulated in sleep, xviii. 2.
---- powers, accumulation of, xii. 5. 1.
---- exhaustion of, xii. 4. 1.
---- wasted below natural in hot fits, xxxii. 9. 3.
---- less exertion of produces pain, xii. 5. 3.
---- less quantity of it, xii. 5. 4.
Sensual motions distinguished from muscular, ii. 2. 7.
Sex owing to the imagination of the father, xxxix. 7. 6. xxxix. 6. 3.
xxxix. 6. 7. xxxix. 5.
Shingles from inflamed kidney, xxxv. 2. 2.
Shoulders broad, xxxi. 1. xxxix. 7. 6.
Shuddering from cold, xxxiv. 1. 1. and 2.
Sight, its accuracy in men, xvi. 6.
Skin, skurf on it, xxvi. 1.
Sleep suspends volition, xviii. 1.
---- defined, xviii. 21.
---- remote causes, xviii. 20.
---- sensation continues in it, xviii. 2.
---- from food, xxi. 1.
---- from rocking, uniform sounds, xxi. 1.
---- from wine and opium, xxi. 3.
---- why it invigorates, xii. 5. 1.
---- pulse slower and fuller, xxxii. 2. 2.
---- interrupted, xxvii. 2.
---- from breathing less oxygene, xviii. 20.
---- from being whirled on a millstone, xviii. 20.
---- from application of cold, xviii. 20.
---- induced by regular hours, xxxvi. 2. 2.
Sleeping animals, xii. 2. 2.
Sleep-walkers. See Reverie, xix. 1.
Small-pox, xxxiii. 2. 6. xxxix. 6. 1.
---- eruption first on the face, why, xxxv. 1. 1. xxxiii. 2. 10.
---- the blood will not infect, xxxiii. 2. 10.
---- obeys lunations, xxxvi. 4.
Smell, xiv. 5. xvi. 5.
Smiling, origin of, xvi. 8. 4.
Solidity, xiv. 2. 1.
Somnambulation. See Reverie, xix. 1.
Space, xiv. 2. 2.
Spasm, doctrine of, xxxii. 10.
Spectra, ocular, xl.
---- mistaken for spectres, xl. 2.
---- vary from long inspection, iii. 3. 5.
Spirit of animation. See Sensorial Power.
---- of animation causes fibrous contraction, iv. 2. ii. 2. 1. xiv. 2. 4.
---- possesses solidity, figure, and other properties of matter, xiv. 2.
4.
Spirits and angels, xiv. 2. 4.
Stammering explained, xvii. 1. 10. xvii. 2. 10.
Stimulus defined, ii. 2. 13. iv. 4. xii. 2. 1.
---- of various kinds, xi. 1.
---- with lessened effect, xii. 3. 1.
---- with greater effect, xii. 3. 3.
---- ceases to produce sensation, xii. 3. 6.
Stomach and intestines, xxv.
---- inverted by great stimulus, xxv. 6.
---- its actions decreased in vomiting, xxxv. 1. 3.
---- a blow on it occasions death, xxv. 17.
Stools black, xxvii. 2.
Strangury, xxxv. 2. 1.
Sucking before nativity, xvi. 4.
Suckling children, sense of, xiv. 8.
Suggestion defined, ii. 2. 10. xv. 2. 4.
Sun and moon, their influence, xxxii. 6.
Surprise, xvii. 3. 7. xviii. 17.
Suspicion attends madness, xxxiv. 2. 4.
Swallowing, act of, xxv. 1. xvi. 4.
Sweat, cold, xxv. 9. xxix. 6.
---- in hot fit of fever, xxxii. 9.
---- in a morning, why, xviii. 15.
Sweaty hands cured by lime, xxix. 4. 9.
Swinging and rocking, why agreeable, xxi. 3.
Sympathy, xxxv. 1.
Syncope, xii. 7. 1. xxxiv. 1. 6.

T.

Tædium vitæ. See Ennui.
Tape-worm, xxxix. 2. 3.
Taste, sense of, xiv. 5.
Tears, secretion of, xxiv.
---- from grief, xvi. 8. 2.
---- from tender pleasure, xvi. 8. 3.
---- from stimulus of nasal duct, xvi. 8. xxiv. 2. 4.
---- by volition, xxiv. 2. 6.
Teeth decaying cause headachs, xxxv. 2. 1.
Temperaments, xxxi.
Theory of medicine, wanted. Preface.
Thirst, sense of, xiv. 8.
---- why in dropsies, xxix. 5.
Tickle themselves, children cannot, xvii. 3. 5.
Tickling, xiv. 9.
Time, xiv. 2. 2. xviii. 12.
---- lapse of, xv. 3. 6.
---- poetic and musical, why agreeable, xxii. 2.
---- dramatic, xviii. 12.
Tooth-edge, xvi. 10. iii. 4. 3. xxii. 3. 3.
Touch, sense of, xiv. 2. 1.
---- liable to vertigo, xxi. 9.
---- of various animals, xvi. 6.
Trains of motions inverted, xii. 5. 5.
Transfusion of blood in nervous fever, xxxii. 4.
Translations of matter, xxix. 7.
Typhus, best quantity of stimulus in, xii. 7. 8.
---- periods of observe lunar days, xxxii. 6.

U.

Ulcers, art of healing, xxxiii. 3. 2.
---- of the lungs, why difficult to heal, xxviii. 2.
Uniformity in the fine arts, why agreeable, xxii. 2.
Urine pale in intoxication, xxi. 6.
---- paucity of in anasarca, why, xxix. 5.
---- its passage from intestines to bladder, xxix. 3.
---- copious during sleep, xviii. 15.

V.

Variation, perpetual, of irritability, xii. 2. 1.
Vegetable buds are inferior animals, xiii. 1.
---- exactly resemble their parents, xxxix.
---- possess sensation and volition, xiii. 2.
---- have associate and retrograde motions, xiii. 4. xxix. 9.
---- their anthers and stigmas are alive, xiii. 5.
---- have organs of sense and ideas, xiii. 5.
---- contend for light and air, xxxix. 4. 8.
---- duplicature of their flowers, xxxix. 4. 4.
Veins are absorbents, xxvii. 1.
---- paralysis of, xxvii. 1.
Venereal orgasm of brutes, xxxii. 6.
Venesection in nervous pains, xxxii. 5. 4.
Verbs of three kinds, xv. 3. 4.
Verses, their measure, xxii. 2.
Vertigo, xx.
---- defined, xx. 11.
---- in looking from a tower, xx. 1.
---- in a ship at sea, xx. 4.
---- of all the senses, xxi. 9.
---- by intoxication, xxxv. 1. 2.
Vibratory motions perceived after sailing, xx. 5. xx. 10.
Vinegar makes the lips pale, xxvii. 1.
Vis medicatrix of nature, xxxix. 4. 7.
Vision, sense of, xiv. 3.
Volition defined, v. 2. xxxiv. 1.
---- affects the whole sensorium, xi. 2.
---- diseases of, xxxiv.
Voluntarity, xi. 2. 4.
Voluntary motions, ix. xxxiv. 1.
Voluntary ideas, xv. 2. 3.
---- criterion of, xi. 2. 3. xxxiv. 1.
Vomiting from vertigo, xx. 8.
---- from drunkenness, xx. 8. xxi. 6.
---- by intervals, xxv. 8.
---- by voluntary efforts, xxv. 6.
---- of two kinds, xxxv. 1. 3.
---- in cold fit of fever, xxxii. 9. 1.
---- stopped by quicksilver, xxv. 16.
---- weakens the pulse, xxv. 17.

W.

Waking, how, xviii. 14.
Walking, how learnt, xvi. 3.
Warmth in sleep, why, xviii. 15.
Weakness defined, xii. 1. 3. xii. 2. 1. xxxii. 3. 2.
---- cure of, xii. 7. 8.
---- See Debility.
Wit producing laughter, xxxiv. 1. 4.
World generated, xxxix. 4. 8.

* * * * *

END OF THE FIRST VOLUME.