A Letter from Mr. Anthony Leewenhoeck Fellow of the Royal Society, Dat. Apr. 14. 1684. Containing Observations about the Cristallin Humor of the Eye, etc.

A Letter from Mr. Anthony Leewenhoeck Fellow of the Royal Society, dat. Apr.14. 1684. containing Observations about the Cristallin humor of the Eye, &c. In mine of September the 7th, 1674. I communicated my Observations concerning the Cristallin humour of the Eye; which I find to have been inserted by Mr. Oldenburg, in the Phil. Transactions Num. 108. p. 178. where I say, that the Cristallin Body (or humour) of the Eye, is in hardness much like a preserved Nutmeg; which with a Razor I cut in too, and so observed the same in parcels, and found it to consist of many Orbicular scaly parts, lying one on the other, which had their beginnings from the Center; all which parts consisted again of Cristallin Globules: And having suffered the said Cristallin humor to dry for 3 dayes, it became so hard, that in the cutting, it broke in pieces: as if it had been hard Rozin. And observing again, these parts, I found therein, not only the aforesaid Orbicular scaly substance; but further, that each scale, was again composed, of other Ring-like parts, and that these second were contrary posited to the other: Thus much I observed, on the Cristallin part of the Eye; to which, I add, that I compared the scaly parts to a Globe, made out of a number of thin papers, lay'd the one on the other, and that every paper or scale, was again constituted out of so many parts, as there may be lines drawn upon a Globe, reaching from one Pole to the other. I have sometime since, again made several observations, concerning the Eyes of Oxen and Cows; for that often since my first observations, I have thought, that I had not yet discovered the make of the Cristallin humor of the Eye, so thoroughly as I might have done. I therefore first examined the Film or Membrane which encloses it, and separates it, from the other humors of the Eye; and conceived that it was constituted of Threds; but at another time, tho there were great diligence used, I could observe none at all. In these Inquiries, I have seen (though seldom) the impressions of the thred-like substance, of the outermost scales, of the Cristallin humor, in the forementioned Membrane; whence I concluded, that one use thereof might be, to fill up all the unevennesses caused by the threds in the superficies of the Cristal, and so to constitute a perfect Round. Another use of it, may be, by compressing the Cristallin humor to alter its figure, and make it part of a greater or lesser Circle: and this being so, it may not improperly be called a Muscle. Although (as before is said) it did not plainly appear, that the Film is constituted of threds woven together; I notwithstanding, make but little doubt thereof; because formerly, in the thinnest Membranes I have seen these thred-like appearances, and also for that I examined the parts thereabout and found a great many streakes or Lines, seeming to be Lymphatick Vessels, designed for the nourishment of the humours of the Eye; these I traced till they entred into the coat of the Cristallin humour, and then they grew so small that I lost the sight of them. I further observed, that the aforesaid Cristallin body, was compounded of thin scales, placed upon one another: These seem'd about 2000 thick, for the Axis, where it was longest, was \( \frac{2}{3} \) of an Inch, so that the distance from the Center to the Circumference is as \( \frac{1}{3} \) of an Inch: now the length of an Inch being six hundred hairs bredth, (as I have often said) \( \frac{1}{3} \) must be 200 hairs bredth, which being multiplied by 10. (the number of Scales equal to the bredth of a hair) make 2000. Scales, the thickness of this Cristallin body. I have further observed, that each of these these scales, is constituted of threds, which in a very neat order, lye by one another, so that each of these scales, is the thickness of one of the threds, the appearance hereof to view, I have represented, as well as I could, by Lines drawn in a Circle, Fig. 1. ABC. is the Cristallin Body, of the bigness it appeareth to the naked Eye, B, is the part lying next the Cornea Tunica; but these I have magnified, that I might the better represent the threds constituting every scale. Fig. 2. KEIGHIL is represented, as if the aforementioned Fig. Num. 1. lay with the round B next the Eye: and altho I have here drawn many Lines, which represent as many threds, yet is their number nothing to those, in the Circumference of the Cristallin humor of an Oxe, which are above 12000. For 10 threds lying close together side by side, making not out one Diameter of an hairs breadth, now if the whole Axis (as before is said) is 400 hairs breadth long, then is it long 4000 of those threds. And this computed by the common Rules, amounteth to 12571\(\frac{3}{4}\). the number of the threds lying side by side, and which make out the whole circumference of the Cristallin Body. Hence may be perceived how thin these threds are, and how wonderfully they run not through the Axis, as I heretofore conceived, but taking 3 several wayes out of the point L, (the imagined Axis.) These threds do not approach the Axis, on the other side of the Cristallin body, as they do on this, but turne back, with a small bent making there the shortest threds. For example, the shortest threds here, viz. MK. HN. and OF. reach up to the Axis on the other side, and fill up the place; (as is here represented at L,) now the threds MK, having filled up their place, in the Axis of the other side, (as the threds ELI doe here) they returne from thence back, and are here the shortest threds HN. These HN place themselves again, on the other side near the Axis, and returning back again, are then OF. and OF coming from the other other side nigh the Axis, is here again KM. To conclude, those which are here the shortest threads, are on the other side the longest; and the longest on the other side, are here the shortest. To present this yet clearer to view, I have drawn with lines, the threads composing one of the scales of the Cristallin body, seen on one side, as Fig. 2. R T P S W Q, and notwithstanding it is a flatty round, I have here made it Globular, with consideration, that in this Representation, the threads constituting each scale, may be the better discerned. P and Q are the middle points or Axes, of which P in the foregoing Fig. 2. is denoted by L, the threads issuing out of the point P, in the foregoing Figure 2. L extend to V, where they are the shortest threads, from whence they again extend back to P, where again they are the longest, and from P they again extend to W, where they are again the shortest; and thus also are extended the threads from T to Q, and from thence again to X, and from X to Q, and thus half the course of every one of the threads (since we must suppose this for an half round) is demonstrated. In short the threads LI, in the foregoing Fig. 2. are here PS; and the threads between L and M in the foregoing figure 2. are here the threads between P and X; and the threads between L and O in the foregoing Fig. 2. are here, the threads between P and T. So that the threads in the foregoing Fig. 2. between POLIKE, are here in Fig. 3. the same with R T PS. Here is further to be observed, that the threads constituting the Cristallin Body, are thickest about R and S, and the nearer they approach to P or Q, they are the thinner. To conclude, when we view the forefaid Cristallin body with attention, as it cometh fresh out of the Eye, we find it to excel in transparency the purest Glass, notwithstanding it is composed of so many thousand threads, and that they lie very close compact together, so that one might justly wonder, how the light can pass through them in right lines, which is absolutely ne- cessary; for if it were otherwise, the Cristallin body would appear white, but not transparent. To please some curious persons, and to represent this Cristallin body, yet plainer to their sight, I have taken a small Tennis Ball, and wound the same about, with a very fine Cord, having before stuck in many small pins, in the places where it was to be kept from slipping; then I smeer'd the Ball over with strong Glen, and when it was well dried, took out all the Pins, and this Ball, with the cord wound about it, representeth the Cristallin Body of the Eye. I have heretofore said, that the parts, which I now plainly perceive as threds; are again constituted of Globules; which now in some of the threds I clearly discern. But, for that I always discern it not, I conceived, that as the threds (as here before is said) are very small, and clotted one to the other, that so in the separating of them, some parts of one thred remain fastned to the other, which may appear to my sight Globules: I conceived it might better agree with their Fabrick, to suppose that each thred, was again composed of many other smaller threds joined together, as I have heretofore said, that the Flesh threds although 9 times thinner than a hair of our head, are again constituted of other threds. I further took out of the Eyes of Sheep, Hogs, Dogs, and Cats, the Cristallin bodies, and ordered them, as I had done those of an Ox; but have found not the least variation, either in the scaly parts, or in the course of the threds, composing each of those scales. The same agreement I found also, in the Eyes of Hares, and Rabbets; except that whereas the threds constituting the before-mentioned Cristallin bodies, spread themselves from the Center, in three distant courses; here the threds of each scale, spread themselves but in two courses. Fig. 4. A B C D representeth half the round of the Cristallin body of the Eye of a Hare or a Rabbet; E is the Center, which lyeth extended to the Apple of the Eye; there these threds constituting each scale, which run as through the Center E, are on the other side, the shortest, and appear like unto F or G, likewise F and G, on the other side run through the center. I have also caused the foregoing Figure to be drawn side-wise, the better to represent the thred-like appearance of each scale. I suppose then, that the threds, which in fig. 4. are represented between E and F, are the same with those in Fig. 5. represented by I O. so that the threds, which come from the point I (the same with E in the former figure.) end here, in N and L; where they are the shortest; and those which extend to O, through, or close to the center M, where they are the longest, end there, or bend again on the other side, as the same do here. In short those which here approach the center I, are on the other side furthest from the center. In the aforementioned Observations, I have for the most part, endeavoured also to discover the nature of the Vitreous humour of the Eye; and which surroundeth for the most part the said Cristallin humor, for that I concluded, it was no watry matter, but rather a transparent Muscle; But notwithstanding all the means I thereto used, I could not make the least discovery thereof, for that this matter always changed into a watery substance. I further examined the Cristallin body of the Eyes of Fishes, which are perfect Globes; and found them also constituted of like thin scales, lying one upon the other, as in those other Animals before noted: and each scale also composed of threds, but these threds run not in the same manner, as those of other Animals; yet, notwithstanding all the industry by me used, I could not discover the true course of them, for when the threds approach the center, they appear so thin, and so close joined together, that the sight cannot trace them, and cause such a confusion, that I cannot be certain, whether they end in the center, or return again from thence. By Fig. 6. A B C D. I represent the Cristallin body of the Eye of a Cod-fish, and although the circular lines representing the threads constituting each scale, be only drawn by a pair of Compasses, from the center A, to the center C, and therefore lyse more distant one from the other, then in the foregoing figures; yet are the threads composing each scale, not thicker, except in the middle, as here B and D they are somewhat thicker; and the nearer they approach to A and C, they are the thinner. Fig. 7. is the true bigness of the Cristallin body of the Eye of a Cod-fish. I have also examined, the Cristallin bodies out of the Eyes of Birds, only to view how the threads of the scales, constituting also the Cristallin body, run; and after many observations, I have discerned, that the threads constituting the Cristallin body of a Turkey-cock, are extended like those in fish; but as the Cristallin body of a Fish's Eye is perfectly Globular, those of Birds are a flattish round: as Fig. 8. posited with its flattish side D towards the Cornea Tunica. And when from without the Cristallin body of the Eye of a Turkey-Cock, I had with a very sharp knife, taken off many of the scaly parts, to bring it to a smaller Globe, it changed its Figure, and became an Oval; as Fig. 9. where E, is the same point with D, in fig. 8. the threads being, where they meet, so thin and small, that at last they are not distinguishable. From whence we may conclude, that the threads of the scales, which lyse nearest the center, are in the midst thin; as in Fig. 6. at B and D is shewed, and make thus an Oval figure: and that when the Cristallin body increaseth in magnitude, the threads become then in the midst thicker; and thus constitute a flat round; as I have perceived it, for the threads in the Cristallin body of a Turkey cock, in their thickest part, were thicker than those in an Oxe, Hog, Sheep, &c. Before I leave this discourse, I cannot but mention, that I have by several wayes and means, been with my naked Eye, Eye, a threddy substance, like that whereof the Cristallin humor consists: I shall only mention two of them, viz. I take a clean wine Glass, and hold the Rim thereof close against the Pupil of one of my Eyes, while my other Eye is closed; and looking thus, firmly through the Rim of the Glass, against the flame of a Candle, or other light, I perceive the thred-like appearance above named; as if through a Microscope, I had beheld a piece of a scale of the Cristallin Body of the Eye. Or closing one Eye, I hold the fingers of my hand, before the other Eye, to close together, that they leave but a small opening between them: this small space between the fingers, through which the Eye receiveth the light of the Candle, will present a like thred-like appearance, as in the former instance. I have often been aware, of a moisture lying on the outside of the Pupil of the Eye, containing some few very small Globules; which as oft as we close our Eye Lids, change place: From hence may be learnt, the necessity of the Eye Lids in us; and why Fishes which continually live under water, need them not, but should Men and other Animals, that live out of the water, not have them, they would soon be blind: For if the Eye Lids by their closing, did not constantly moisten the Eye, the superficies thereof, would dry up and Rumple: and that chiefly in the Sun, or before a hot fire. Also it is not improbable, that from the inner part of the Eye a moisture continually issueth through the Cornea Tunica, which by Eye lids is cleansed off; for when I had examined several Hogs Eyes, which had been scalded with hot water, to get of the hair, I for the most part observed, that a thin Film, which was on the Cornea Tunica of the Eye, was somewhat singed; whereby it was easily separated, from that film, that was immediately under it; and when I then pressed the Eye, a little, between my fingers, I perceived in several places, a thin watry matter to soak through through the Horny film, and lye like a watry damp on a Glass; and when I continued this pressing for some time, this watry damp increased into small Drops, and at length run like water in a stream. This ought not to seem strange, considering the parts of the Horny Coat to be made of hollow vessels, like veins; very thin, and spread about in Branches. I have lately taken the Horny coat of an Ox's Eye, and have separated from it, seven films, extremely thin, in each of which, were a number of interwoven, very clear, and transparent streaks; which I judge to be, many of them, blood Vessels; but so small, that they contain none of the Globules, which cause the redness in the blood. By the rubbing of our Eyes, with our hand, we may so press these blood vessels, until they become so stretched out, that some of these bloody Globules, may get in, and remain there, for some time, which may cause that redness in our Eyes; which comes by our rubbing of them. But to return again, to the Eye lids. As our Muscles and other parts of our bodies rest not, unless posited as they lay, when we were yet in the Womb; (as I formerly said) in like manner, the Eye lids, are not at rest, till the Eyes are closed, and therefore we cannot long continue the Eye lids open, but with force; and, that the same might not be wearied, we often close them, although we mind it not. I have seen People, that listening with attention, to a Discourse, have closed their Eye lids according to my Calculation 6000 times in an hour; whereas others, standing by them, closed them not, above 2000 times in the same time. Since I wrote unto Mr. Oldenburg, in the year 1673, that the matter, causing the redness of our Blood, was constituted of Globules; I examined the blood of Oxen, Sheep, and Rabbets; and observed no difference in magnitude, between the Globules of those Animals, and those of Men: so that I conceived, that that matter which in general general made all blood red, was Globules. But, after I had tryed the blood of a Salmon, a Cod, of Frogs, &c. and found that the matter, which caused the redness therein, was made of parts oval, and flattish, (as I have before laid) I examined the blood of several Birds; and have also observed, that the matter causing the redness of their blood, was also composed of like Oval flattish parts, with those of Fishes: so that I now concluded, that all Animals, whether Birds, Fish, or other Creatures that live in the water; have the parts causing the redness of their blood, consisting of the said Oval flattish parts, and if hereafter I chance to find the contrary, I will advise you thereof. A dif-