Platerus golden practice of physick: fully and plainly discovering, I. All the kinds. II. The several causes of every disease. III. Their most proper cures, in respect to the kinds, and several causes, from whence they come. After a new, easie, and plain method; of knowing, foretelling, preventing, and curing, all diseases incident to the body of man. Full of proper observations and remedies: both of ancient and modern physitians. In three books, and five tomes, or parts. Being the fruits of one and thirty years travel: and fifty years practice of physick. By Felix Plater, chief physitian and professor in ordinary at Basil. Abdiah Cole, doctor of physick, and the liberal arts. Nich. Culpeper, gent. student in physick, and astrology.

The Causes.

The Cause of all the declared Accidents of the Sight is either in the part communi∣cating the visive power, viz. the Brain, or consists in the Instrument receiving that power and al∣so the species of external things, to wit the Eye; which when as it consists of many more parts, then the other Organs of the senses, and humors also, in every one of them some causes prejudicing the fight may arise.

First of all in the visory or net-like Nerve implant∣ed into the Eye, and the principal Instrument of See∣ing; then in the three humors that fil up the Eye and serve the visory Nerve, last of all in the Membranes themselves that constitute the Globe of the Eye and in∣trinsecally distinguish the humors. If the Cause lie in those places where they are pervious to the sight as a∣bout the Black of the Eye, and where only if the impe∣diment of seeing do consist, it may be seen and known, for if it be elsewhere it is so hidden that it doth no waies appear to those that behold the Eye.

As all Senses may be hurt by reason of the Brain so also Seeing is weakned; both if it suffer a Disease General or Special and especially in that part where the optick Nerves come forth, or those Nerves themselves produced from the Brain and car∣ried unto the Eyes, are affected; which affects may be various.

A Cold Distemper sometimes breeds Blindness the other senses be∣ing somtimes unhurt; if the Fore∣head and Eyes being much and a long time refrigerated by cold wind, which being less cover'd, are the more exposed to the injuries, and the cold penetrating even to that part, where the optick Nerves have their original, the said parts are so hurt, that they become Blind; or there remains afterwards a certain weakness of sight, which I have seen befall a noble Matron in the Head-ach from the too much application of Oxyrrho∣dines actually most cold, who all her life time could no waies recover her sight any more; that this also doth happen, if the whol brain be hurt by the same distem∣per hath been shewed in a stupidity, but then the rest of the senses are abolisht too, and its easily known by that, whence the cause proceeds, as if it be from exter∣nals 'tis plain of it self.

That a Hot Distemper of the Brain doth bring together with a Depravation of the Mind also

a Hallucination of the sight, and the said Imagination in which various false Images of things are offerred to the sight, hath been said in a Phrensie.

As also it hath been explain∣ed there, that that distemper which ariseth from the Pertur∣bation of the spirits in the Brain from Malignant hu∣mors, together with Madness and Melancholly, doth likewise represent false Apparitions to the sight.

Too much Driness of the Optick Nerve induced by burning Feavers the easier into that Nerve, seeing it is thick, doth produce a Blindness remaining after these Feavers.

The beginning of the Nerves be∣ing comprest or bedewed as we have shewed that an A∣poplexy is caused, in which all the Senses are taken a∣way at once, so also if this be only about the rise or meeting of the Optick Nerves, or in the other car∣riage of them out of the Eye, which then must needs be from an afflux either of a bloody or flegmatick humor, it is somtimes wont to happen, that a Blindness doth suddenly follow, if the humor presently fall down thi∣ther.

But more commonly the Optick Nerves being irri∣gated or too much moistened by the watry flegmatick excrements of the Brain, which in this middle seat of the Basis of the Brain, where the optick Nerves break forth, alwaies flow down to the Infundibulum which is next to these Nerves; and together with the Nerves, and neer them break forth into the Chamber of the Eye and amplitude of the Nostrils, a darkness of sight is wont to happen in old folks and flegmatick; or if they be refrigerated by the same humor or be comprest in those streights rather then obstructed as they would have it, a blindness also is wont to follow; which abo∣lition or weakness of the sight, together with the hurt of the rest of the senses happens, if this fault be extended to their rise or progress in the Basis of the Brain, or the sight only is abolisht, if that seat chiefly be affected, and that commonly in both Eyes by reason of the meeting of the Optick Nerves and their short passage to the Eye, that is rare that one Nerve only can be so affected; the which doth proceed from flegm or a wate∣rish humor as is sufficiently manifest, by the signs of that humor abounding in the brain; and it is easily known also that a Nerve is affected, when nothing appears in the Eye, which can bring such loss or Obscurity of the sight, neither have we found this sign to be true, which they have thought most certain, to wit, if the unsound Eye being comprest the Apple is not dilated, this comes to pass by default of the Nerve, because the influx of the Spirit into the same is impeded, seeing the animal spirit doth not distend the Eye like wind, neither fils it up but persists in the netlike Nerve.

Hither also shal be referred that not unusual Cause, but by no man as I know rightly described, of that blind∣ness which is somtimes left, after grie∣vous and frequent Convulsions; the which is not from an afflux of humor as they would have it, but because in those great Convulsions by the Convulsion fits of all the parts and the Eyes also, in which they also oftentimes appear convulsive and very much stretcht out and bowed down, the Optick Nerve growing to them being thus attracted and too much distended, and that being wreathed too, and hurt, and the passage or visory spirit being hindred it happens that the Eyes are deprived of Seeing, and that it proceeds herefrom we have found out by diligent examination, and conside∣ration.

The Substance of the Brain being hurt as by an Apoplexy there is a pri∣vation of all the senses, so a Nerve be∣ing contused or wounded there which some do testifie hath somtimes happe∣ned from a puncture made by the Forehead a manifest Blindness by rea∣son of the Solution of Continuity or a Callus left hath suddenly happened, and so from a blow.

A Weak Constitution of the Brain, the spirits being dissipated and wasted by reason of old Age, or by some grievous and long continued disease, too much eva∣cuations, especially of Blood and Seed whence is a great effusion of spirits and immoderate Venery for that reason doth very much prejudice the sight; al∣so by reason of too much Watchings as hath been said there, it induceth an Am∣blyopy or weakeness of sight and also of the other sen∣senses especialy of those that have a more subtile object as of Hearing, often familiar to old folk, as appears in these external causes of them, remaining in those that are recovering, and accustomary to those that live in∣temperately.

Besides this cause which proceeds from a defect of spirits which there can be no doubt, we can by no means be induced, to feign another here in the thickness or thinness or subtilty of the Spirits as many indeed do propose these things with more subtilty than truth, out we are moved by many things to dissent from them; seeing the animal spirit being wel nigh aethereal, doth no waies suffer such changes, but is most easily dissipat∣ed, as no man neither hath ever dared so much as to fan∣sie the Vital Spirits to grow thick or be attenuated; as also wesee, unless now the defect of seeing happen from the Spirits its other discommodities, whence things far distant or neer, are less truly discerned, do happen ra∣ther from the fault of the Instrument as by and by shall be explained, not by reason of a certain thickness or subtilty of the spirits, as they have thought, seeing they are so subtile, that they cannot be more subtile.

Divers sorts of hurt of the sight are wont to pro∣ceed, by reason of the perturbation or agitation of the spirits of the Brain and the brain, also being affected by consent with them; as if being mixt with a hot, subtile vapor, either tur∣bid, or malignant, they do not only pervert the mind, but corrupt also the sight so that they think they see many things which are not; as if from the like vapors the spirits and brain grow hot, then together with the Raving, false Apparitions also are objected to the Eyes, as hath been said in a bastard Phrensie, and as if a certain Narcotick vertue be joyn∣ed with the heat, as hath been shewed to be from the e∣vaporation of Wine then together with the Drunken∣ness of the mind, that there is also an error in the sight in which they think they see divers things which are not, or those things which are they judg of falsly, hath been declared in Drunkenness (as the story of him who being drunk alwaies thought things to be double, being decived by his Wife, burned his hands, gives cre∣dit to this business) furthermore when other filthy and malignant vapors from the Region of the Hypochon∣dries do assail the Brain & disturb it and its spirits they

do not only pervert the Mind but also sometimes pro∣pose the sight being caused by consent seeing they trou∣ble the Mind too they belong to the Alienation of the mind where it hath been largely treated of them.

But also it oftentimes comes to pass that the seeing is hurt by the too much agitation of the spirits, not by that which in the affects of the mind, the spirits being not only agitated, but rather confounded to∣gether with the humors conteined in the Head, Heart, and whol body, doth only disturb the mind, and scarce hurts the sight: but by that in which the spirits in the Brain being moved either themselves or with the mix∣ture of a vapor, without any perturbation of the mind, those called a Vertigo, Imagination and Scotomie are wont to be raised.

For the spirit contained in the Brain and its Arteries and Ventricles, being moved and stirred more vehe∣mently, even without the mixture of a vapor, represen∣ting to the Imagination the like commotion in things without it breeds the said Vertigo of which commoti∣on there may be divers causes; for a vehement moving of the head after the same manner continued long doth cause that the spirits for the same reason being stirred and following the Head afterwards resting, yet never∣theless they stil for a while run up and down after the same manner as the motion of the head was made, till they rest again; as it comes to pases if the Head toge∣ther with the body be turned long Round, for then a Vertigo follows, so that if this be done longer a strong one comes, that they cannot stand on their Feet, but somtimes necessarily stagger and fall, as it oft happens we see these things both in men and beasts; so the head being bowed a long while downwards, the spirits then tending from that upwards to the beginning of the Nerves, when that it is erected again, the same spirits with violence going back again to their proper seat, from that motion somtimes a Vertigo is perceived.

But if it happens not from this motion of the body only, but also from a persevering or vehement com∣motion of the mind the spirits being often and strong∣ly exagitated, in profound and dayly cogitations, and other passions of the mind, as also in Watchings, that those thus accustomed, moved from some light internal cause, fall into a Vertigo; as we do observe Vertigoes do somtimes trouble them that do very much labor at their Studies when they are fasting, for the causes by and by to be mentioned.

But from the long beholding of a thing whirled round or otherwise moved swiftly whether this be so, or seem to be so, as the Earth seems to be moved and run, to them that sail, which happens to some from their Imagination when their Eyes are shut, some are seazed with a Vertigo, the spirits also by that agitation of the sight which follows at the sudden commotion of the object, being stirred after the same manner, and as it were following the swiftness of the sight; which as it happens to those whose spirits are easily stirred, so in those disposed to the Vertigo it gives occasion for the fit to seaze, although the cause be but light. Also look∣ing downwards from a high, steep, and dangerous place breeds a Vertigo in those that are not used to it, the spirits being too much diffused, and drawn back again with fear, and so moved unequally; and there∣fore this no waies happens to those that are not afraid, unless they be otherwise disposed or some other cause joyned, as if from such a high place they behold things which are wheeled about, or Whitle-pools of Wa∣ters.

But as this Vertigo doth happen from external cau∣ses by reason of the too great impulse of the spirits, so also the spirits of themselves collected in the Arteries of the Brain, especially being more hot and plentifull because they are unquiet do cause a Vertigo and are ea∣sily agitated of themselves, or from a light occasion joyning; the which doth long and much torment men from a light cause either alone or also with a pain accompanying it, whose Arteries do beat vehemently in their Head and Ears, with a tingling of them some∣times and often in the rest of the body, and they are scarcely cured unless by opening of them, as shall be said; but this may come to pass by it self, the blood being so heated and attenuated in the Arteries, or by the mixture of a thin Vapor, as shal be said by and by.

But we have found our another cause of a Vertigo proceeding from the spirits in the Arteries and Vessels of the Head, by dissecting a certain Merchant our Country-man, who many yeers being sick of a Verti∣go was neither able to walk nor to rise out of the bed, but he fel down, to wit, the veins of the Brain and all its Arteries from their rise and ingress within the Skul, in their whol passage through the Brain, grown together, and hard, and distinguisht with little Glandules in their whol progress; from which obstruction of them, the spirits being impeded and retained in the Brain, being wheeled about by a light motion, bred an incurable Vertigo.

But by reason of vapors mixt with the now declared spirits of the Brain, there are wont to be produced not only a Vertigo, but also the said Imagination and Sco∣tomie, either seazing at once, or apart; and they ac∣cording to the diversity of the nature of the Vapors and place from which they arise, and to which they are carried in the Brain; for if they being plentifully con∣founded with the spirits of the brain in its Vessels, fil∣ling up those places and seeking passage out, together with them they be brought to the sides, by offering to the sight, such a sense and motion in things externall they breed a Vertigo as hath been said formerly; ligh∣ter or more grievous according as their agitation is greater or less

The which also doth affect a man alone, if the Vapor be subtile and no otherwise polluted, or if it be too hot there is joyned also a pain of the Head; if it be tur∣bid or some other way polluted, coloured, shining, as it may diversly exhale from divers humors and Choler as shal be said by and by, then there are caused Imagi∣nations also with a Vertigo by which there falsly repre∣sented to the sight divers small bodies, Insects, Atoms, Colours, Shinings; or if by their obscurity rather than thickness, as they would have it, they darken the sight, they cast Clouds, Fumes, or Darkness before the Eyes together with the Vertigo in the said Scotodinos affect for though they see nothing, (as formerly hath been said of their Eyes closed) yet they may feel a Ver∣tigo.

The which Imaginations notwithstanding and Ob∣tenebrations or Darknesses do oftentimes also happen apart without a Vertigo, if that Circumaction of the spirits in the Head be not made, but only a mixture of the Vapors with them; the which for what reason it can befall the sight, in so great a variety of Opinions concerning this thing, we must a little more diligently search out.

Many have beleeved these Vapors ascending and breaking forth of the Chamber of the Eyes which are before the Eyes like a Fume, do either deceive, or hin∣der the sight being moved with this reason, because they saw tears provoked, and the Eyes look red from

Vapors which in like manner did penetrate to the Eyes and prick them; yet this seeing it rather comes to pass, from the pricking of the sensible coat of the No∣strils, by reason of its communication with the adnate coat of the Eyes, this comparison will no waies take place; and seeing the vapor, if it did so come under the orbite of the Eyes, and creep about them, it would presently fly forth before it could touch them, we re∣ject this Opinion as weak.

But others have thought that these Vapors do wholly go under the Eyes and penetrate even to their inner∣most parts so that intrinsecally they are seen by the Eyes, but whenas after this manner there is no passage to the Globe of the Eye, and that is so thick by reason of the horny coat on every side whol, that the Vapors can no waies pass through it, into which a Needle can hardly be thrust, when a Suffusion is to be taken off, this Opi∣nion of some is vain, and by so much the more foolish, because they would palliate and cover their errors with the perspirability of our body.

But others that they might explain after what man∣ner these vapors might enter into the Eye, seeing they knew that there was no other entrance into the cham∣ber of the Eye, then of the Optick Nerve, Vein and Artery; they have writ that these Vapors indeed did first assault the Brain, but from thence descended by the Veins and Arteries to the Eye; not understanding what we have deliverd in our Anatomy, that these ves∣sels only run through the adnate coat of the Eye and do no where come neither into the horny coat of the Eye, nor the inner part of the Eye, seeing if blood should en∣ter the Eye, by its colour it would represent all things red unto the sight (as it comes to pass when being poured out of the Vessels it falls upon the Horny coat) for this reason it hath been proved by this de∣monstration that the Vapors are not carried neither af∣this manner to the Eyes.

Others more considerately teach that it comes to pass, by reason of the optick Nerve, which they hold to be the chief instrument of sight, the which we also do admit of, yet we grant not that this is done for that rea∣son, as they who have thought that the vapors can en∣ter the optick Nerve and through that as through a pipe are carried from within the Scul even to the Eye; seeing turbid vapors can no waies be carried through the Nerves ful of animal spirit, and seeing this is against the nature of vapors to be carried downwards unless they be driven by some violence (which here is not at all.)

But we rather probably think that it happens thus, to wit, that these vapors assaulting the fore parts of the Brain especially, and being confounded with the ani∣mal spirits, there with the brightness of the Images which are offered to the Brain by the optick Nerve, where all sensation and distinction is made, by the mix∣ture of some sparks, by which their light is rendred un∣equall, or darkned in certain places, they represent to the Brain these like false apparitions confounded with the true Images, in this hurt of Seeing which is called a little Cloud; for that this is done in the Brain and not in the Eyes, the Vertigo which for the most part doth accompany these imaginations as hath been formerly demonstrated, doth sufficiently shew, the spirits then in the Brain being affected and agitated too, whence they that then labor of a Vertigo have not these imaginati∣ons, but seem to themselves wholly to be turned about, and a Scotomie or Obtenebration of the sight, that they become almost blind sometimes following these little Clouds, the spirits being then wholly obscured by a multitude of vapors, doth evidently declare it; all which hath been sufficiently demonstrated to happen in that part of the Brain which gives the Original to the optick Nerves, and is higher than the rest, and therfore seems chiefly to prejudice Seeing, but not in the Eyes if it proceed from vapors.

As in an internal fault of the Eyes arising from a Coat growing there, we shal by and by shew, that that these Clouds also, and the other aforesaid may be offered to the sight, and the sight also be wholly obscu∣red, in that called A Suffusion of the Black of the Eye; wherefore these little Clouds generated from vapors they have falsly called by the name of a Suffusion be∣cause they thought that then also vapors were spred o∣ver the Eyes, and did there generate a little skin, which we have more rightly indigitated to be little Clouds, & Imaginations; which also are distinguisht from a true Suffusion by these signs, because in a Cloud & imagina∣tion there is no Speck in the Eyes of the affected, these accidents of the sight being objected to both Eyes at once, which do somtimes abate and cease and return a∣gain at a certain time, seeing in a true suffusion the fault appearing in one Eye, but scarce perfectly in both at once, it hinders the sight without intermission, as shal be said there.

But the Cause of these Evaporations whence a Verti∣go imagination and Scotomie proceed, may consist in divers parts of the body, seeing somtimes vapors raised from the lower parts are sent into the Head, most com∣monly they proceed from the Stomach, in which a cholerick humor especially, bringing a hot subtile eva∣poration, and sending it not only into the Nose (as the vapor rising from Onions Radishes, Mustard, is wont only to vellicate the Nostrils and presently again is dissipated) but also into the head it self, sometimes causeth a Vertigo, somtimes Imaginations: which for the most part imitating the nature of Choler, somtimes are yellowish, somtimes green, or blackish: and seeing Choler in the Stomach is most fierce and boyling hot whiles it is empty, and the vapors then being hindred, are the more freely carried upwards, it happens that the said accidents are troublesome to the cholerick whiles they are yer fasting, and that upon the taking of meat, because the vehemency of Choler is abated and the vapors represt, they grow milder, and at last cease; the which happens also the vapors in the head being discust of their own accord, and so much the sooner by how much they are more subtile, till new evaporations being made, these evils do return; but it is known that this proceeds from Choler, by the bitterness of the mouth and gnawing at the mouth of the stomach, which they call the heart, and by other signs of this hu∣mor; which also somtimes brings with the same labor a pain of the Head too, with a Vertigo.

The same vapors proceeding from the Mesaraick Veins in which the cholerick juyces are wont often∣times to abound, as hath been shewed elsewhere (as by those vapors raised from the same place, and carried upwards by the Veins and Arteries, intermitting Fea∣vers, hypochondriacal Melanchollies do invade a man by intervals) so also they oftentimes raise the said symp∣toms, which is done the vapors being carried upwards from thence through the Veins, and somtimes through the Arteries which are annext to the Mesaraick Veins; then especially when those vapors are subtile, that they induce rather these accidents than Perturbations of the mind which hath been shewed do rather proceed from their malignity the which therefore do somtimes pro∣duce Vertigoes only or as they are qualified, Images and Scotomies together with them, or without them; which we had rather alleadg as the truer cause than

Pretend Crudities, from which Wind rather than these like Vapors are generated.

But also from some other seat of the body these like vapors raised from a thinner blood through the Veins and Arteries may cause the same: as from that part which is about the Womb, as the Courses being stopt this symptom also doth happen; as other also often∣times upon this account: and from some part of the Foot or of another member a vapor proceeding like to some Air being carried upwards, as we have observed it hath been the Cause of an Epilepsie, so also of a Ver∣tigo, whence somtimes Vertigoes go before an Epilep∣sie and presage that wil presently follow, when from the like vapors vellicating the Brain, Epilepsies also may be caused, as shal be said in its place.

But the cause of these diseases sometimes consists in the Head it self, in which not only spirituous, hot and plentiful blood collected, may cause the same (as hath been said formerly) but also from humors contained there, the like Vapors raised and mixt with the spirits may produce these accidents; which we do beleeve doth arise rather from the Blood of the Vessels and Ventricles of the Brain, and the humors mixt with it than from flegm, the which also we do not deny to be a cause of the Vertigo, but not because it sends forth vapors, but after this manner now to be explained.

'Tis certain that a Repletion of the Brain caused by a watry humor, as well that Serous as Flegmatick doth cause that Vertigo which is wont to precede and threaten an A∣poplexy or Carus; which being frequent and of long continuance unless it be prevented, is wont to terminate in these Diseases with great danger of life; but it doth not this by cooling and moistning the brain, seeing this agitati∣on of the spirits which is in a Vertigo would so rather be hindred than promoted; but this comes to pass, when filling up the windings and spaces of the Brain by its great plenty filling the Skul, and also generating plenty of Wind (which are oftener ingendred from waterish humors than Vapors) it waves in it; for then as in the cover of the heart, water abounding doth cause a Palpitation of the heart, when it is stirred; so here also, it every where filling the Brain when the Head is moved, the humor being stirred and following the mo∣tion of the Head, as we have said of the spirits, it gives such a sense to the head; which doth sufficiently ap∣pear by their relation, who complain of such a fluctua∣tion, and the Skul being opened, we have often found an immense plenty of this humor, as hath been said in an Apoplexy, and in him in whom even now we said that the Arteries too were grown hard, we have found so great plenty of it, that the Skul being opened it hath come forth by floods, the which together with that ob∣struction of the Arteries, producing a double cause of the Vertigo, made it so lasting and incurable, in which that humor for continuance watring the Brain, had bred that Carus of which he died. But it is known that this is the cause of a Vertigo not only from that sense of fluctuation, but also from other signs of flegm abound∣ing, explained in a Carus and Apoplexy, to which those that are prone become at once sleepy and more stupid, and at last fall into these Diseases unless pre∣vented.

By occasion of the Visory Nerve implanted into the Eye and dilated like the form of a Net, most discommodities of the fight do happen, seeing that is the principal Organ of seeing; and that for the most part by consent of other parts, when by reason of them it is disappointed of those things which are re∣quired to Seeing, viz. the spirit and the proper object, or else it cannot rightly enjoy them, for otherwise be∣ing immersed in the Eye 'tis so grounded, that 'tis scarcely troubled with any disease, unless by consent of the Brain.

It is disappointed of the Animal spirit either altogether in blind∣ness, or in part in a weakness of the sight, by reason of the Optick Nerve, such as are Distemper, Compression, Hurts, and Weak∣ness proceeding rather from the defect of spirits, than that fansied thickness and subtlty of them.

The same happens also, the spirits flying from the visory Nerve towards their beginning: in the Eye prest a long time, and by consequence the Net-like Nerve by reason of humors filling up the Eye, it some∣times happens that they are afterwards so long blind til the spirits return again.

And also the spirits being too much idle in the viso∣ry Nerve and as it were laid asleep, or being retreated when there is no use of them, the Nerve it self being made dull, in those who being kept in darkness for a long time, as in Prison or other dark places, have seen nothing for a long time, when they return into the light, they scarce recover their fight, or slowly, or never any more.

And seeing the Animal spirit hath a constant need of the vital, this by swooning being for a while dissipated, and the Animal spirit being hindred by consent, a∣mongst the cessations of functions, the Seeing first of all is darkned in those that swound, and by and by it is taken away with all the rest so long till they come to themselves.

By reason of the proper Object, viz. the Images of things entring the Eye by light and brightness; the Net-like Nerve suffers a hurt of seeing if it be offered to it too violently and it be so affected with it, that afterwards it perceives no more, or nor rightly.

As when one very much strucken with the brightness of the Sun, Lightening, Fire, afterwards thinks that he sees sparks for a while, and either their Eyes are altoge∣ther blinded for some time, or as it often happens, they afterwards continue blind.

Or if the Eye be destitute of light by which the things ought extrinsecally to be illuminated, and the Eye in∣trinsecally that it may see; by reason of the external darkness, it cannot know the species of things.

Which also how they happen by reason of the stop∣page of the black of the Eye, we shall explain in the faults of the Membranes of the Eye, as also when it happens by reason of humors, it shall be said there.

Likewise an Impediment in the sight may happen, by reason of hu∣mors contained in the Eye, especial∣ly of the Chrystalline, through which as through a Spectacle, the Net-like Nerve doth first collect the Images of external things, and again receives in its cavity, those dispersed, dilated, & made bigger, to which Chrystalline humor the other humors are servants only, and this comes to pass, when either they fail because either they have flown forth, or are wasted; or when they change their natural scituati∣on,

or their substance is changed, or they are infected with a strange color, which how it may be done we shal explain in the particulars.

And somtimes the humors flow forth of the Eyes more commonly the watry one seeing it is placed in the fore part, and is more fluid, the others seldom unless the cause be great, and then Blindess is caused; for the watry humor being flowed forth, the Globe of the Eye is somwhat fallen together and wrinkled; whence the hole of the black which ought to let in the light, is shut up; and the rest of the humors falling forwards out of the cavity of the Net∣like Nerve, do cause that that doth somwhat fall toge∣ther, whence it must needs be that seeing doth cease; and by much the more if the Chrystalline humor doth fall forth with the glassie, in which it inheres, seeing that (as hath been said) is altogether requisite to seeing and then the Net-like Nerve being wholly fallen together, can no longer comprehend the species of things in its cavities.

Of all which the apparent Cause is wont to be a Wound or Ulcer of the Eye; if a large wound being made 'tis open'd through the horny coat so thick and hard; for by a light puncture with which they are wont to perforate the Globe of the Eye in takeing off a Cata∣ract, the watry humor which hath its tenacity also, cannot flow forth,: and I have somtimes seen that an abscess of the Eye hath been generated from an Inflam∣mation also, in which part of the horny coat is conver∣ted into matter, which being broke, it somtimes pours forth the humors of the Eyes with the matter; and I have observed in a pestilent Feaver that it hath hapend in both Eyes, the Crystalline humor slowing down to the Beard, and sticking there.

The Humors of the Eye also are wasted especially the glassie seeing it is thinner; and then the Eye not be∣ing sufficiently distended (which is required that the black may remain exactly open) but somewhat fallen together, the hole of the apple of the Eye although not wholly shut up, yet loosing its large∣ness or roundness, and the situation of the rest of the humors being troubled by the way there follows a weakness of the sight, or if the confusion be greater, Blindness: as in long acute Diseases wasting the body with a high and long continued pining it happens to some more rarely, but more frequently in extream old age, in which both the glassie and crystalline humor may be dried up, as shall be said by and by; whose Eyes appear somwhat wrinkled, which the vulgar ther∣fore are wont to call Crackt, especially when in the A∣gony of Death being now destitute of heat and spirits they flag.

A Perverting of the natural situation of humors, the Chrystalline and glassie (which seeing they are more solid, being restrained by their proper membranes they ought to stick fixt in their proper place) doth also bring hurt to the sight whose places being changed, the watry humor filling up the space left by them easily gives place.

The which somtimes happens in the glassie humor (to which the crystalline humor is set over, and a little way im∣merst in its former part) if the same part of it carried forward be set before the crystalline humor; where also be∣ing oftentimes contained, it may be seen lie a white Speck under the apple of the Eye, for then it is not necessary that blindness do yet happen, seeing the humor is bright as Glass, but some Error; see∣ing it is thicker than the watry humor, as it is wont to come to pass in a Suffusion beginning, as shall be said: unless perhaps so great a quantity of it be fallen thither, that it wholly obliterates the crystalline humor, and presses it backwards, or very much inverts it, for then both humors being troubled, more grievous accidents of the sight are wont to follow, as shal be said in the crystalline humor; but the cause of this may be a blow, or Contusion, or more frequently a puncture in couch∣ing a Catarract, being forced too deep to these humors, and breaking their thin membranes to which they co∣here: for otherwise scarce as they would have it, can a great straining by holding of the breath in going to stool, in Labor, or Convulsions in which the Eyes ap∣pear as if they were thrust forth, cause that intrinsecally in the Eye.

The Crystalline humor being especially hanged like a Sun in the middle of the Cavity of the glassie humor, somwhat distant from the hole of the apple of the Eye looking directly on that with its bulk, and receiving the light through that equally disperst into it, and dif∣fusing it to the cavity of the visory Nerve, or the Net∣like semiglobular, placed in the hinder part of it, so that it fils it every where with its brightness, if it doth very much change this natural situation, it cannot be done without hurt of the sight; which faults of it, seeing the humor it self cannot be seen in the Eye, are no waies conspicuous in it, unless it wholly fall into the apple of the Eye, as hath been said of the glassie humor.

But this comes to pass, if being in some manner inverted by its broader part which is flat like a great Lentil, it is not rightly op∣posed to the hole of the apple but declining a little to the side it looks on it obliquely or trans∣versly; or when being carried upwards or downwards or to the sides from the middle seat of the Eye, it doth somwhat decline from the aspect of the hole of the Apple; the which happening either from the birth in some, in others from some violent cause, as was said even now in the glassie humor, it hap∣pens that either blindness is caused, if the recess be great from the natural situation, or if it be less an obscurity of the sight or rather some Error in which things seem to be either double, or crooked, or bent: moreover some light declination only of the crystalline humor from the center of the apple although yet it doth little hurt the Sight may be the cause of Squinting; for as in Seeing if the crystalline humor be rightly opposite to the hole of the Apple, the Apple also doth directly look upon the external things which it beholdeth, so if the crystalline humor be a little turned from the center of it, that they see with the apple not rightly but obliquely opposite to the things, those troubled with a Squinting do so invert the Eye, that they are judged to look upon somwhat else, than the thing objected; the which not∣withstanding may happen also by reason of the con∣torted situation of the apple as shal be said by and by, which things do thus befall men for the most part from their birth.

But especially if the crystalline humor have its seat a little in the hin∣der part of the Eye to∣wards the Netlike nerve it is the cause of this

sight in which they cannot rightly discern things more distant, the which happens to many from their Birth, that the Crystalline Humor doth not reside more towards the fore parts at the Apple, as it is naturally wont to do, but hath its Scituation exactly in the middle of the Eye, and it is so common, that Anatomists for the most part have described its Natural Scituation in the midst of the Center of the Eye; whence it is no wonder that this sight which we have called the youthful, doth befal many from their Birth, that they can discern things neere righ∣tly and acutely, but not things distant, and that when the Spectacle is too much inclined backwards from the things which we behold, which therefore will be suffici∣ently illustrated only with those neerer, but from those Images objected at a distance, unless being collected by the Mediation of a thick Spectacle made of Crystal they be so offered to the Eye more effectually, they cannot suf∣ficiently illustrate that: And hence it happens that see∣ing the Scituation of it doth so continue, this seeing is no waies altered the whol course of life, unless this be from some other Causes.

And also if it be yet more removed from the middle of the Eye towards the hinder parts, they are forced yet to apply far neerer to their Eyes, the things which they would see, and use a thicker Spectacle: the which yet is not very common, and happens only in them, which we have said are cal∣led Myopes or Purblind.

Which truer Causes, which happen by reason of the In∣strument vitiated, and therefore may be corrected by a∣nother Instrument to wit a Spectacle, he had rather alledg then to refer them to the Spirits, which in those young Folkes, with whom this fault is familiar, and who see most acutely things neer, are neither defective nor chan∣ged, because they may be mended by a Spectacle.

And also for the contrary Cause, after a different manner, there ariseth an Impediment of the sight, to wit when the crystalline Humor from the said Natural Seat doth more in∣cline forwards, towards the Apple, for then with a greater dis∣commodity they less see things neer but the same removed far from the Eye, they behold more rightly, unless they correct this defect, by applying a thin Glass Spectacle, which as it performing the place of the Crystalline Humor and re∣ceaving and differing the Images of things, and through the Crystalline representing them greater to the Eye, and therefore they have alwaies need of a Spectacle to read and see acutely; the which happens to most people growing old, to some sooner, to others later, not by reason of the defect of Spirits as they have thought, seeing so there would follow rather a weakness of the sight, as also of the other Senses, which a Spectacle could no waies mend, nor suggest new Spirits; but because by that bow∣ing down of the Head which the whol time of our age we must needs cast down our Eyes, in reading, and in what Business soever proposed to our Eyes, and acted by our Hands, the Crystal Humor by process of age together with the glassy is carried by degrees to the fore parts, and at length subsisting there, brings this defect to the sight, especially if in them also, the watry Humor being somwhat wasted no∣thing do resist it, and the glassy Humor lying upon it, do more strongly depress it; which defect and a far more grievous, Blindness or Weakness of the sight do follow, if the crystalline Humor wholly falling down to the Apple, be manifestly seen to stick there, and to stop up the Eye: which is wont to be more frequently the Cause of the hurt of seeing, in Horses and other Creatures, which go with their faces downwards: the which as it happens by degrees by reason of age, so somtimes suddenly after a Blow.

The substance of the Humors of the Eye changed doth also bring a fault in the sight, as it comes to pass, if the Crystalline Humor be too much har∣dened, as it may happen either by reason of age or other Causes, but with which, not unless the Body be vehemently & a long time dryed; and then be∣cause it looseth its Transparentness either in part or wholly (as it appears being boyled) it is the Cause of Blindness or Dulness of sight, which as in that so also it may happen af∣ter the same manner in the glassy Humor.

But if yet by its Natural Conflitution or progress of age, it become more solid or obscure, because then it hath need of a greater light that it may be illu∣minated, it comes to pass that they cannot see perfectly but by a ful light, and when that fails, though it doth a little clear, with the splendor of light, yet they see not rightly, and thence follows the said Nyctalopy.

But that is the watrish Humor whose substance is more easily changed, seeing it is wont oftentimes to ac∣quire a Tenacity by which by degrees growing to the hole of the Apple, and at length drawn out and turned into a skin by breeding Clouds first, and aferwards a Suffusion, it makes blind: which fault being very common, and to be seen outwards also, shall be explained in the grapy Coat.

The Humors are scarce infected with a strange Colour, seeing no veins or other vessels carrying the humors do enter into the inward parts of the Eye, or touch its Humors: the which notwithstan∣ding they have delivered doth sometimes come to pass from the moistures of the Eye, in the Crystalline Humor, and that as also the glassie humor is dyed with a grayish co∣lour, and therefore they have called it Glaucoma, and they have writ that the sight is then vitiated as if they saw thorough a Cloud; when notwithstanding the Ancients made a Glaucoma the same disease with a Suffusion, then especially calling that so, when the Skin being not yet well confirmed, it appeared to the Beholders like a thick Glass, of a greenish, or azure Colour, and was not yet white.

The sight is hurt by reason of the Membranes constituting the Globe of the Eye, if that do consist in that part which appears darkish or black by reason of the Apple or Hole opening the inward Chamber of the Eye which is black and opa∣cous, which Hole seeing it doth transmit the outward light into the inward part of the Eye thorough a trans∣parent Horn spread over it, if it be so obliterated in any part that the Passage of the light into the Eye is hindered, it must needs hinder the sight; the which happens either by reason of the outward thick Membrane, bestowing a Horn on the Eye, or of the grapy Coat under it, that makes the Hole, those giving occasion for this thing either severally or joyntly.

This happens by reason of both Membranes, if an Impediment be ob∣jected out of the Eye, which may in∣terrupt the light, that it cannot come to the seat of the Eye to which it ought, as it is wont to come to pass the Eye-brows being shut, with the Hands and other things.

But from this following fault also that may happen, if the seat of the Eye which is pervious and transparent is hindered by the Neighbouring parts that seeing cannot rightly be perfor∣med; as it comes to pass if the Ap∣ple be not placed in every fore part of the Globe of the Eye, bare and in that middle, but declining from it, is more to the sides of the Eye, which befalls some from their Birth in a squinting in one side of those Eyes, for that rea∣son

there appears more white; so that every one by that may know that they look a squint; and because when they would look upon things, wreathing the Eye that they may oppose the apple right to the things, they make such a stern aspect.

Although this may happen also, the apple consisting in its natural place, by Convulsion of the Muscles of the Eye, the Eye drawn somwhat to one side and so in∣verted that the apple do rather look that way; whence it comes to pass, that when they would look upon any thing would direct the apple to it, either they bend their head aside, or draw back their Eyes by the oppo∣site sound Muscles, that the apple may be redu∣ced again some way to the fore parts: as they also whose eyes have a natural situation after this manner drawing them aside purposely, can express the eyes and looks of Squinting, which Convulsion unless it befalls the eyes in a true Convulsion of the whole body, to wit, an Epilepsie, in which they shew the like aspect, for the most part it befalls the Squinters from their birth; the Muscles being somewhat contracted rather, then convelled, and continuing in that situation. And that hath been explained by others to be the only cause of Squinting, when notwithstanding that very thing as hath been said may come to pass, the apple being im∣prest on one side and the crystalline humor being re∣moved out of its natural place that they behold things by distorting their eyes after the like manner: all which notwithstanding do hurt the sight only on this account, that the Eye being left in its seat, they see those things rather which they meet with sidewaies, then those which are placed before their face, til the Eye being re∣duced so far, that 'tis opposed to the things placed right before the eyes, they behold them•• also.

But this rare and memorable thing befell one from a wound made neer the inner Angle of the Eye by which the Globe of the eye was so inverted, that the apple being brought even to the great corner, and covered with the Skin of the wound healed, he was forced to see through the cavity of his Nose, and he could see, nothing any more, unless through the hollow of his Nose as through a pipe, whence he must needs direct his Nose to that, which he would see, which by the relation of men worthy to be beleeved, is apparent was done in our time.

The private faults of the horny coat, do then preju∣dice the sight, when they possess that part of it which is set over the apple like glass or a transparent horn and either only stick there or are dispersed further through the white of the eye; which then may be ma∣nifestly seen and known when it is spotted or covered.

This diaphanous seat of the horny coat being steined with a strange color, so that it is not any more bright and cleer, but obscure and colored, it either stops the brightness which in seeing ought to enter into the Eye, like a foul glass which lets in the light, or offers some∣thing false to the sight.

And this chiefly comes to pass, if it be infected with an obscure or white color with which somtimes the whol seat of the horny coat appears changed, and brings the said darkness especially in old men, to whom this chiefly hap∣pens; but if that only in some part of it such a white speck do grow it is called Albugo; in which fault if the speck be perfectly white and spred over the whole region of the apple, there ariseth blindness; but if it first begin to grow white, it darkens the sight as if it were hindred with a Cloud drawn over it, or if it comprehend a little space of the apple, or from that incline more to the Circle, it breeds a certain error in the sight.

But such an Obfuscation or whiteness of the horny coat ariseth either from the driness and hardness of the whol horny coat: or if there be only a speck from the driness and and in duration of that part only which is seen white. For as we see other things which are trans∣parent as the white of an Egg and the crystalline humor in the Eyes of creatures being dried by boyling do be∣come white and lose their transparency, so it happens here to the horney coat that by old age in which the membranes are wont to be dried, or by a disease of the eyes after Ophthalmies, Epiphories either it being wholly dried up, or driness being left only in certain places of it, it doth allor in part become white; the which also we may see somtimes come to pass from the thicker part of the nourishment with which it is nourished, being carried thither, and remaining there, and leaving a white Speck, as in the Nails, which in the like manner are marked with white specks som∣times are superficial, and other times being more deeply imperinted they penetare the whol horny coat.

And also from a Wound or Ulcers of the eyes espe∣cially after the smal pox in Infants, a Skar or Callus being left, higher somtimes deeper and thick for the most part causeth such a white Speck in the white of the Eye, sometimes large somtimes oblong which is cal∣led a Skar, which doth obliterate the fight either whol∣ly or in part, or if it be long and narrow, it cuts it in two as it were and divides it.

Besides these discoloring of the hor∣ny coat we meet with red specks or somtimes yellow, from blood rushing from a blow of the Eye, or from an infusion of choler in those troubled with the Jaundise, but for the most part appearing only in the white part of this coat, which the adnate coat carrying the vessels doth only invest, and then they do not prejudice the fight. But if they reach so far as to the bright part of the horny coat (where oftentimes a red speck is con∣spicuous a long while, the blood persisting in the sub∣stance of the horny coat without corrupting, as it were an insect in Amber) they represent to the sight the same color, either red, or yellow in all the Images the Eye seeth.

The same transparent part of the horny coat is extrinsecally invested with a new coat growing to it; which somtimes wholly growing to it grows in one, or adheres to it without any connexion, unless where it ariseth, and in the compass, on the other part 'tis only spred over; somtimes proceeding from the greater corner of the Eye, and somtimes from the less, and being first spread over the white of the Eye by and by it covers the black of it, either in part or all: and it is at first thinner then growing thicker it becomes fleshy interweaved with many bloody veins and 'tis called a Pannicle. And oftentimes it is so augmented that it may be laid hold on by the fingers, and a little way be elevated from the Eye; and somtimes a part of it hath been cut off, that hath weighed two ounces. But at o∣ther times being hardened it grows white and then it is called Ungula, Unguis, Pterygium, Zebel, putting out the

sight wholy or in part, as it occupies the Black of it more or less.

The which growing out either from a Spontaneous afflux of Blood, or after Exulcerations tis called a Hy∣persarcosis or Chymosis: otherwise from a private fault offensive especially to the Membranes, it very often befals the Elephantiacal as shall be explained there, o∣therwise seldom betiding man: as I have often seen it befal Fishes if they be kept a long time in Fish ponds in foul water, the mud growing to them and blinding them. Somtimes the said Unguis grows from the Su∣perficies of the horny coat corroded, when part of that nourishment then breathing forth, doth concrete into a matter like unto that which resembles a Horne or Nail, only tis not transparent; as the Periostia of the Bones being corroded we have said elsewhere that Knobs are generated, and from the Skin wounded, Skars, from the Juyce that was wont to nourish them.

The faults of the grapy Membrane hurt the sight, when its hole, which they call the Apple, being pervious in that part of the Grapy coat which lies under the hor∣ny coate, yet no waies grows to it, and letting in that light into the Eye, is either stopt up with some humor, or filth, or is Contracted, or Dilated; all which may be seen and known, Extrinsecally also in the Back of the Eye and its compass, whenas the horny coat which is seated over it, is transparent, although the hurt lie un∣der it.

Somtimes this hole is stopt by a Humor and the Passage for the sight is intercepted; and this come to pass somtimes from the proper humors of the Eye the Crystalline and glassy falling in∣to it; as from the change of the Scituation of the Humors as hath been said, and from the too great largness of the Apple as shall be said, it may come to pass, and the sight may be so hindred; which is seen then also when it appears lik an Albugo, in that seat of the Eye.

The same may come to pass from blood infused by a blow not only into the horny coat as hath been said before, but also penetrating even unto this emp∣ty space, between the Horny and Grapy coat, and filling up that either wholy or in part, and stop∣ping up the Apple, which being red at the first, but then growing livid, by and by blackish, it appears that it lies there (because blood infused into the spaces of the Body is presently corrupted, otherwise then when the horny coat drinks it up, where without any change it persists red oftentimes for a long while, as hath been said) and then it either depraves or darkens the sight: more or less, as it Possesses a little or the whol space and tis properly called Hyposphagma, a sugillation of the Eye.

The sight also may be hindered by matter collected in that seat, and then that Disease is called Pyosis, in which if the matter collected plentifully do seem to possess all the black of the Eye, or to fill up the whole space of the Circle, and to shine thorough the Horny Coat, it is called Hypopios; but if a small portion of that said seat do seem onely to shine through like the pairing of a Nail, it is called Onyx or Unguis, the Nail.

The Cause of the collection of which Matter for the most part is wont to be, Blood fallen into the Eye, as hath been said, and at length converted into Matter; or an Inflammation of the Eye going before, and leaving an abscess behind it, not that, in which the horny Coat is corrupted too, and being broke it pours forth the hu∣mors of the Eyes, as hath been said formerly, but in which the Blood being discust after an Inflamation, or External cause: this collection of matter also is som∣times caused after pains of the Head; which when it comes to pass, tis probable this was done, by the wa∣try humor so suppurated and ripend, as we have else where shown, that matter may be generated by the like humors; because the Blood otherwise can scarce be brought hither, unless the horny coat be contused by violence, the Veins as hath been said, no waies rea∣ching thither.

A Tenacious snivel sticking in the compass of this hole, or on the brink of the Apple, and spred over it, and by degrees thickening, for the most part only in one Eye although the other somtimes also doth presently begin to be affected in like manner, the seeing doth most commonly suffer a Blemish; and, because it is suffused or poured out on the Apple, it is called Suffusion, Hypochyma: which at the beginning seeing it is yet a transparent snivel and doth transmit the Light, yet by reason of its thickness it breeds an Impediment and Error in the Sight, as if it were darkned with a Cloud spread over it, and things were seen with many Atomes slying as hath been said, whence then it is called Imagination and a little Cloud, as hath been shewn: and this is not yet wel con∣spicuous in the Eye, but that the black of it, which they cal the Star, doth not appear exactly black as it ought to be wholly black, but somwhat troubled; by which also, if this be seen only in the Eye, the other being yet pure, it is distinguished from that Imagination and Clouds which by reason of Vapors offer themselves to the Eye almost in the like manner, except that they do affect both Eyes equally.

But at last that Snivel by degrees being more and more thickned and loosing its perspicuity, is easier known by the sight, and doth commonly manifest it self, by a grey or ash Colour, as the Oculists call it, and somwhat blotting out the black of the Eye, then also it doth more offend the sight: because when it is yet more soft and watrish, it cannot yet be deprest with a Needle, as shall be said; which the ancients have named Glau∣coma, from the grey colour which is a fault of the Cry∣stalline Humor, and because the Crystalline Humor being dyed with this Color doth carry before it a shew of an immature Suffusion, some not knowing that, have made a Glaucoma properly called, the same with a Sussusion.

But last of all, the forementioned Snivel, being whol∣ly incrassated and made white as we have formerly said that bright things by drying do becom white, and loose all their perspecuity, so it happens here also, and then the sight being wholly taken away, a perfect Blindness follows: unless by chance as I have often seen, a very little of the black do still appear pointing or circularly in some part of it, or in its Compass, thorough which the Sparks of a little Light, do still illustrate the Eye with an obscure Light, by which notwithstanding they can judg rightly of nothing; and this is called a confir∣med Suffusion, which they are wont to call ripe, if so be it can be exactly seen, because then first of all the Chyrurgion may take it in hand; and they common∣ly call it a small Skin and Web, because being spread before the Apple like a Coat it intercepts the Light: not unlike in Colour and Tenacity to the skin grow∣ing

to the white of an Egg that is boyled; and though of it self it seems to be of no moment, yet it is wont to bring so great calamity to many men in the loss of their fight.

They refer the cause of this snivel growing to the ap∣ple to the rising of a Vapor, or influxion of a humor, but it hath been shewed formerly that from a Vapor this Suffusion is not caused, but those simply called Imagi∣nations, and how that comes to pass, and truly it were the work of a man too much at leisure, to confute with many words so vain an opinion.

But all the rest do think that it is caused by an influx of humor, and do vainly apply all their care to turn away this, as shal be explained, and therefore they foolishly call this affect a Catarhact, others a discent of waters into the Eyes; the which notwithstanding can be pro∣ved by no reason, nor shown by demonstration. For first of all if it were caused from an afflux of water or humor into the globe of the Eye, not only this small matter would grow, and scarce as big as a Lentil, but the whol Globe of the Eye would be distended, and swell as it were Hydropical; besides that there is found no empty space in the Eye which can admit this water, seeing it is all every where so filled and distended with its proper humors bred there from the birth, that there is not room for one strange drop, or can the horny coat by any means be distended or dilated more: and then by what way I pray, shal this water flow into the Eye, when that cannot be through Veins and Arteries which as hath been declared formerly, do no waies en∣ter the inward parts of the Eye: but they say this comes to pass through the Optick Nerve, an excellent shift indeed, to hold so noble a part fit to conveigh these excrements, through which nothing can pass be∣sides the aethereal animal spirit. But grant that humor doth descend through this Nerve, How I pray can it be the hole of the Apple? when neither the Net-like Nerve can come to admit it into its cavity, which is wholly filled with the glassie humor, neither can it pass through the Grapy Coat which every where about grows transversly to the horny Coat with browy pro∣cesses: the which certainly, they who do patronize such like opinions, contesting with sense and reason, if that the fabrick of the Eye were throughly known and perceived by them, with that dilgence as is meet, they ought first to consider and rather to search out the true waies through which the humors may be carried, than being ignorant of the proper causes of Diseases al∣waies to fly to that common refuge of Ignorance, De∣fluxions, and I know not what transpirability of the body.

But we having throughly searcht into these things a long time and much, and by long observation having more neerly contemplated innumerable suffusions and their beginning, encrease, and pricking, we have found that the cause of this snivel doth proceed, from the wa∣try humor acquiring some tenacity: for that as hath been said formerly in the explication of that and other humors) seeing from the birth it is more tenacious (for we have seen also oftentimes that those new born have brought this fault with them into the world, or it hath presently followed upon them) either being dri∣ed by process of age, in old age, in which it often hap∣pens; or arising from very hot Diseases after Burning Feavers or Inflammations of the Eyes or from a vehe∣ment external heat in those who perform most business sitting by the fire and looking upon it; or the watry hu∣mor being thickened by the use of Collyries too hot & drying, and being made more viscous as hath been said, by degrees it grows to the brink of the membrane of this hole which it continually washes, and by little and little thickening in that part where it stops up the hole, as we see the said Skin grows on Frumenty, for that reason as it hath been shewed being hardened it looseth its brightness, and successively but in a long time being converted into a Skin it takes away the sight: which if it be deprest, as shal be afterwards explained, the remain∣ing portion of the warry humor, on whose superficies it grew, being yet transparent, the Sight presently returns, but if that also by much drying hath already lost its brightness, as most commonly it happens, although the superficies of it be taken off, nevertheless they re∣main blind, and by reason of that the Oculists labor wil be in vain.

The too much narrowing or Immi∣nution, as they call it, of that hole in the Grapy Coat wich is called the Ap∣ple, doth scarce take away the Sight, when even thorough the narrowest hole the light may enter the Eye, and illuminate it, as much as is sufficient for seeing; whence we have observed that those, who from their birth have happened to have a very small Apple, nevertheless do see as acutely, as those that have it large, may sometimes more acutely, and things more distant: and as we can behold the Sun through a little hole with less offence to the Eye, so they are less offended than others, by an external brightness and great light; of which seeing they have a more abundant need to see wel, beyond others; it comes to pass that a little before night, or darkness som∣what growing on, they see less, than by a ful light, & this is the chief cause of that Nyctalopie in which they see not sufficiently, by a sleight brightness of the Moon, Stars, or light set up: although this also as hath been formerly explained, may happen by reason of an ob∣scuration of the horny coat or humors, because then al∣so they have need of a greater light, that they may be illuminated, neither is a smal Apple observed in all those that are Nyctalopous or cannot see in the Night.

Which as it is born with some, so it can scarce come to pass, as some teach, that by reason of the spirits di∣stending the Eye, or so great driness of the Globe of the Eye, that by that means the Apple may wholly fall together; as somtimes it happens from a wound of the Eye, the humors flowing forth, and the coats falling together, they become wholly blind, as hath been de∣clared formerly.

A Dilatation of the Apple called Mydriasis by shedding plenty of light into the Eye, hinders the cleerness of the sight, darkening it with too much brightness; and if the enlarging of it be great, in a light somwhat more ob∣scure and darkish they see more rightly than in that too much shining, and that by reason of the internal brightness of the Eye, sufficiently illuminating the Air for seeing: as we have had an example of this rare dis∣ease, in a certain Foundling living in our Hospital the year 1625. who by day time, and in presence of light was blind, but by night and in the dark, did see the smallest things; hence we have observed that amongst Birds, the Owls; and amongst Animals the Cat which also do see by night, can by twinckling contract the hole of the Apple, and of their own accord dilate it a∣gain, and so streighten it at the brightness of the Light, or a Candle, that only an oblong black cleft doth ap∣pear, but by night and in the dark, dilate it so, that the whol former region of the Circle seems black, and for that cause Owls also receive obscure Images, with a very

open Eye, and in the day time, that they may not be hurt by them too much appearing, they joyn them a∣gain, and covet darkness. For otherwise this largeness or narrowness of the Apple, makes little for the seeing things distant, better, or less, as some have thought; seeing these defects of seeing which we have called the yong & old mens Sights, may happen as we have often observed, both to those endued with a long and a nar∣row Apple, and what I have observed in many, and in my self, that though the Apple of one Eye be far lar∣ger in the same man, than that of the other Eye, yet the seeing is alike in both Eyes; neither could we observe yet, that though such a dilatation of the Apple do hap∣pen, the things which are seen should be represented less than they are, as some have been opinionated.

But for the most part this dilatation of the Apple be∣falls certain living Creatures from the birth, as those for which it was convenient to see by night; and unless it altogether exceed a mean, otherwise than hath been said, it doth no waies prejudice the seeing, but rather seems to bring some benefit, as one hath declared unto me; who seeing he had a most large Eye-ball, he could comprehend and know by his sight without moving his head, not only those things which were before his face, but those things vhich were far apart on one side, which could not be seen by others, unless by bending the head that waies; the which I did so much the easi∣er beleeve him telling me, seeing this hath happened to me my self in my youth, and at one look at the Ta∣ble I was able to see at once many sitting round about, and to take notice of their gestures; but if that by a wound or some other hurt, the apple of the eye be ra∣ther dilacerated than dilated, than upon that account, because the humors are too much carried to the fore∣parts, as hath been formerly expounded, it sooner of∣fends the sight than it can bring a change after that manner as hath been said; from influx of humors as they have thought, it hath already been declared that it cannot come to pass; but from a vehement impulse of of the spirits by straining, if the eye being dilated, the apple also were inlarged, yet the same ceasing it would by and by return to its natural largeness.

Notes

• The part affected.
• The Cause of the Hurt of seeing in the Brain.
• A cold Distemper of the Brain, is the Cause of Blindness, or weakness of sight.
• A hot distemper of the brain is the cause of error of the sight and of Imagination.
• A malignant distemper in the brain is the cause of error in the sight.
• A dry distemper of the Brain is the cause of blindness.
• The Contusion of the visory Nerve in the brain is the cause of blind∣ness.
• The solution of continuity in the visory Nerve of the Brain is the cause of Blind∣ness.
• A Weakness of the Brain the Cause of weak Sight.
• A preturbation of the spirits of the brain by vapors is the cause of error and Imagination with an alienati∣on of mind.
• The too much agi∣tation of the spirits of the Brain the cause of a Vertigo.
• The Fluctuation of a watry flegma∣tick humor in the Brain is the cause of a Vertigo.
• The Visory or Net-like Nerve in the Eye is the cause of the hurt of see∣ing.
• A Privation of the animal spirit in the Net-like. Nerve is cause of Blindness or darkness of sight.
• A Privation of the Object in the Net∣like Nerve is the cause blindness or dark sight.
• The humors of the Eye the cause of hurt of sight.
• A flowing forth of the humors of the Eye, is the cause of blind∣ness.
• A Consumption of the watry hu∣mor is the cause of Blindness or Darkness.
• The perversion of the situation of the glassie humor is the cause of error.
• The situation of the crystalline humor in∣verted or departing from the middle to the sides is the cause of error and strabism.
• The situation of the crystalline humor drawn backwards or for∣wards is the cause of that sight, in which they see not things unless very neer or things di∣stant better than neer.
• The hardning of the chystalline Humor is the cause of defect of sight.
• The Obscurity of the crystalline hu∣mor is the cause of a Nyctalopy.
• A Tenacity of the watry humor is the cause of want of sight in a suffusion
• A discolouring of the crystalline Hu∣mor breeding error.
• The Membranes or Globe of the eye are the cause of the hurt of sight.
• The shutting the eye is the cause of the sight taken away.
• A Perversion of the Apple or black ap∣pearing in the Eye is the Cause of squinting.
• A perversion of the apple, the cause of a won∣derful affect in the sight.
• An obscurity of that transparent seat of thehorny coat, arising from an obscure co∣lor or white Speck of it in darkness, Albu∣go, a Skar, is the cause of want of sight.
• A red or yellow discoloring of the bright part of the horny coat is the cause of error.
• The horny coat being coverd by a little Skin or Ungula is the cause of blind∣ness.
• An obstruction of the hole of the Grapy coat or the Apple from the proper Humors of the Eye is the cause of Er∣ror in sight.
• An obstruction of the Apple from Blood and matter in a Hypospha∣gma and Hypopion is the Cause of Error or defect in the sight.
• An obstruction of the Apple by snivel at length concre∣ting into a Skin, called a suffusion is the cause of want of Sight.
• The narrowness of the Apple is the cause of a Nyctalopy.
• A Dilatation of the Apple or a Mydriasis is the cause of an evening sight.