The World Turned Upside Down: Revolutions in the Microcosm and Macrocosm and the Crystalline Humor in the Three Eyes of Early Modern Optical Anatomy

Part I. The Three Fleshly Eyes of Early Modern Optical Anatomy

Augustine famously discusses the three eyes of a perceiver. He details that, first, there is the eye of the flesh. Second, there is the eye of the spirit. And third, there is an eye of the intellect. All three eyes converge and interact to constitute sensation and perception’s interrelation with thought. The fleshly, bodily, and corporeal eye, consisting of the bodily organ, experiences the physical vision of things present before it. The spiritual eye, consisting of the faculty of the mind responsible for internal vision, mentally imagines or reconstructs things not immediately present before the corporeal eye. The intellectual eye, consisting of the Christian as well as spiritual soul, attends to knowledge acquired by the other eyes and also to spiritual matters and God. While all three of Augustine’s eyes have a bearing on early modern understandings of vision, for this post, I will focus on three very different eyes in early modern optical anatomy.[i]

The three eyes that I will discuss in this essay are all bodily eyes. Representations of the bodily eye, responsible for sensation and, in many theories, for perception, underwent a major shift during the course of the sixteenth century and into the seventeenth. The changes in ocular anatomy from 1543 to 1619 occurred at an alarming rate as anatomists turned their eyes from classical authorities and dissected non-human animal eyes to the eyes of the human animal. It is possible to debate the elite science’s sphere of influence upon popular beliefs and cultural practices, and while new theories of vision and models from optical anatomy took a long time to establish themselves in scientific and popular thought, it is my contention that they led to fundamentally different theories of a perceiver’s relationship with the world and to themselves. The eye, like the heavens to which it was often compared, became a conflicted space that underwent a radical theoretical reorientation and reconfiguration by the early seventeenth century.

In a period when natural philosophers found reflections of the divine ordering and structure of the universe, the macrocosm, in the body, the microcosm, and even in its parts, the conceptual framework often depended upon analogical and anagogical thinking that read similarity as a bearer of genuine connection. Astronomers and anatomists challenged the traditional ordering of both the macrocosm and the microcosm of the eye from the mid-sixteenth century and developed new models by the early seventeenth.

The German polymath, Johannes Kepler, played a key role in the revolutions in both the macrocosm and the microcosm. Perhaps most famous for his contributions to astronomy when he defended and elaborated upon Nicholas Copernicus’ hypothesis that the universe revolved, not around the earth, but rather around the sun, Kepler made important contributions to theoretically reorganizing the structure of the cosmos, and his work helped replace a Ptolemaic geocentric model of the universe with a Copernican heliocentric one.

At the level of the microcosm, Kepler made another important contribution to yet another revolution. Arguably the most important development of early modern physiology, his 1604 Astronomiae Pars Optica argued that the bodily eye’s lens focuses light and projects it onto the retinal screen at the back of the eye. The problem for Kepler and for theorists of vision and optics for some time following was that if the lens focuses the visual field and projects it upon the retina, the image within the eye would be inverted with respect to vertical orientation and flipped with respect to horizontal orientation. 

The importance of this revolution in the microcosm should not be understated. A. C. Crombie argues that Kepler’s discovery of the eyes’ function constitutes an achievement that rivals, if not surpasses, William Harvey’s discovery that the heart operates as a pump that circulated blood. Crombie argues that a theory of “mechanization” of the body preceded Harvey’s discovery and that this “mechanized” view of the body helped lead to Kepler’s revolution in optical anatomy.

Historian of vision, David C. Lindberg, challenges Crombie’s argument that Kepler was a revolutionary figure. Lindberg ultimately concludes that Kepler represents “the culminating figure in the perspectivist tradition,” “strenuously object[ing] to Crombie’s and Straker’s attempt to view him as a revolutionary figure who transformed visual theory by ‘mechanizing’ it” (Lindberg 207). While Lindberg objects to Crombie’s arguments, I do think Kepler’s theory of vision was revolutionary at its core. To me, the very idea of postulating an eye that did not see either as the visual field before it or as the mind perceived it was a revolutionary move that had the effect of turning the world upside down with respect to the eye. In order to understand the groundbreaking nature of Kepler’s revolution with respect to ocular anatomy, I will use this essay to explore the representations of ocular anatomy and the eye’s functioning preceding and immediately following Kepler’s.

Oddly enough, although cultural and literary critics and historians have extensively studied vision from the late medieval and early modern periods, no one, to my knowledge, yet theorizes the importance of the very profound differences between pre-modern and modern optical anatomy and the theories of vision to which they are bound. In pointing out this oversight, I am not only referring to critics who anachronistically refer to the retinal image in their discussions of pre-seventeenth-century literature and culture, but also to critics who discuss philosophical skepticism or the early modern sensorium without acknowledging the importance of the way contemporary theories of the senses and vision underwent profound changes in the early modern period.[ii]

Historians of science and historians of the senses, on the other hand, cover some of this ground, but their methods often promote and trace narratives of scientific progress that, in my opinion, have two major shortcomings when viewed from the perspective of a cultural and literary critic. The first shortcoming is that these histories of science often deploy a top-down approach that rarely turns to popular culture to explore how scientific developments and thoughts shape and are shaped by broader historical and cultural concerns and shifts. The second is that the focus on scientific progress leads to blind spots in their field of vision when they only study the major figures without attending to how popular and vernacular works describe the same processes.

Take Lindberg’s discussion of the retinal image, for example. In his discussion of Leonardo da Vinci’s unpublished journals that grapple with the notion of the possible inversion of the image within the eye, Lindberg says with subtle sarcasm, “one of Leonardo’s major preoccupations was with the actual path of rays through the eye. His chief concern was to get the rays to the visual power at the end of the optic nerve without inversion, for he must by all means guard against that absurdity” (Lindberg 166). The lengths to which Leonardo goes to try to right the inverted image makes perfect sense when you consider that proposing an inverted image within the eye would be an unthinkable absurdity. For most of human history, the image within the eye was thought to necessarily conform to the visual field before it and to the way in which it was perceived by the mind.

While Lindberg proves a valuable resource for the study of the history of theories of vision, and while he places our understanding of Kepler’s contributions within the framework of a long history of optics, situating him as tied to the medieval tradition, his work is also directed towards exposing the paths that lead to major discoveries rather than exploring the terrain of how such theories and discoveries shape and are shaped by popular culture. My hope is that by exploring those elite discourses alongside popular discourses, we can come to a better understanding about how vision and our sense of “seeing” is itself culturally contingent and shaped through discourse.

Perhaps the best recent work on early modern vision, the eye’s relationship to the inner senses, and the changes happening in both elite and popular discourses on the eye is Stuart Clark’s fascinating book, Vanities of the Eye. In conjunction with his earlier Thinking with Demons, Clark provides invaluable insight into early modern theories of perception and cognition that straddle the boundaries between elite and popular discourses, and between intellectual histories of vision and cultural criticism. In Vanities, Clark argues that vision was “derationalized” over the course of the seventeenth century, challenging the notion that understandings of the eye became more scientific and rational. Even Clark, though, does not really address the profound changes in optical anatomy from roughly the mid-sixteenth to the mid-seventeenth centuries. It is my contention that the process of de-centering the power within the eye contributes to the process of “derationalizing” premodern conceptions of the eye and orders of vision.

This essay will address the potential revolutionary changes in optical anatomy from 1543 to 1619 in two parts. The first half of this essay maps the terrain of early modern optical anatomy. In this part, I argue that the early modern period had three different stages and models of the eye’s structure. The three early modern eyes I detail in this part trace the de-centering movement of the crystalline humor in theories of vision from its early placement at the very center of the eye to its position towards the front of the eye.

The second half of this essay details the associations established between the microcosm of the eye and the macrocosm. In this part, I argue that the developments I discuss in part one relate to changes in theories of the macrocosm. By exploring vernacular discussions of the crystalline humor and its position within the bodily eye, I show how those symbolic resemblances and correspondences in its de-centering prefigure and reflect the reconfiguration of the cosmos.

As I discuss briefly in a previous post, prior to Kepler and the ultimate acceptance of his theory of ocular anatomy, the lens itself did not focus and project light upon the rear surface of the eye, but, instead, was thought to be the “seat of vision.” This seat of vision, called the “crystalline humor,” received the impressions or species of external objects, transferring them, no matter if vision acquired those impressions through extramission or intromission[iii], to the inner senses. While I have discussed those “impressions,” the objects of sensation and perception, and the internal senses before and most likely will again, for now I want to focus on the ways in which the material organ itself underwent a broad historical shift from the mid-sixteenth century to the early seventeenth century.

The crystalline humor was thought of as the seat of vision. Its important position with respect to vision depended not only upon its function, but also upon its physical location within the organ of sight. At the center of a sphere, the crystalline humor occupied not only a central position within explanations of its function but also a central position within the physical eye itself. Early optical anatomies and theories of sight seemingly depended upon the notion that a physically central component reflected and manifested its nobility and centrality to functioning. Many early optical anatomies distorted the position and shape of the crystalline humor within the eye to make it conform more to the idea that it was the most important component of the eye. As with contemporary theories the macrocosm, the physically central position bore symbolic and real significance. Just as the earth stood at the center of the cosmos, the crystalline humor stood at the center of the eye.

The Galenic Eye and Vesalius

I will turn first to the model of the eye I will refer to as the “Galenic eye.” While its representation has the longest history, my visual example comes from the first widely printed work of early modern anatomy, Andreas Vesalius’ monumental De Humani Corporis Fabrica of 1543.

In Vesalius’ figure, we see the crystalline humor positioned at the exact center of the oracular orb. The shape, too, appears more spherical than it should when compared to the images of optical anatomy from a modern anatomy book, and I will compare this Galenic eye to the modern eye later in this post. First, however, I want to attend to Vesalius’ representation and its subsequent critics.

Vesalius famously took issue with anatomies that were based in the repetition of ancient authorities and upon the dissection of non-human animals instead of upon direct observation of human bodies. Despite his corrective to many classically based misunderstandings of human anatomy, Vesalius errs in his representation of the eye, conforming to a model of optical anatomy that placed the crystalline humor almost in the center of the eye.[iv] While the crystalline humor he positions at the eye’s center is not perfectly spherical, in previous and in many later descriptions of the crystalline humor, natural philosophers often referred to it as a sphere. While not perfectly spherical in the image above, many texts continued to describe the central position and spherical shape of the crystalline humor as evidence of its nobility and its central role in the process of vision well past criticisms of such representations.

In the first widely printed work of modern anatomy, Vesalius followed classical authority in placing what had long been considered the seat of vision directly at the center of the eye. The whole of ocular anatomy’s description of the eye placed the eye’s other parts in relation to the crystalline humor. Vesalius, and many other optical theorists and anatomists, emphasized the importance of the crystalline humor. It was not only physically positioned at the very center of the eye, but also the whole of the eye served its centralized power. The fluids which filled the eye provided the crystalline with “nutrition,” the eye’s coats and its spherical shape were designed to protect and enclose it, and the colors on the inside surface of the eye “refreshed” it. It would seem that the crystalline humor’s unassailable centrality to the eye’s function demanded that it remain physically as well as symbolically central to the organ of sight.         

The figure in De Fabrica maintains the eye’s integrity and analogical link to the cosmos by placing the crystalline at the eye’s very center.  Like the earth at the center of the geocentric universe, the crystalline humor maintained its importance by that centrality[v]. The crystalline humor, analogically, and, often, anagogically, related to its object, the world itself, received likenesses of that world in the form of visual objects. 

Despite his placement of the crystalline humor, Vesalius made at least one important contribution with respect to ocular anatomy. The optic nerve, previously widely reported as hollow, turned out not to be hollow at all. Although the notion of the optic nerve as a conduit for vital spirits to transfer to and from the eye and the internal senses or wits persisted in dominant theories of visual perception, the change might have challenged the understanding that spirits carried the species or images into the inner recourses of the brain.[vi]

The Mediate Early Modern Eye

Vesalius’ distortion of ocular anatomy, however, did not go unrecognized for too long after the publication of his book. It was Vesalius’ possible successor at Padua and eventual rival, Realdo Colombo, who corrected Vesalius’ optical anatomy, pointing out and partially amending Vesalius’ error in Colombo’s only publication, the De Re Anatomica, published in 1559. Colombo claims that, like many of the errors Vesalius corrected based on classical anatomists’ dissection of animal bodies, Vesalius’ error derived from the anatomy of large animal eyes, most likely bovine, instead of human eyes. As Colombo puts it,

At aliorum animalium oculi non sunt undique orbiculares, sed vel oblique, vel depressi: neque id mirum est, cum hominis figura tanto interuallo a reliquis distet animantibus. Scito praeterea neminem ante me hominis oculum descripsisse, sed omnes beluinum oculum descripsere, magno & turpi errore, in quem ipse quoque Vesalius incidit, in eius universa pene formatione cum aliis Anatomicis deceptus. Quod verum, esse facile perspicies,si Galeni,vesalii, aliorumque Anatomicorum historiam de oculo cum nostra contuleris. & profecto non leviter hi homines accusandi sunt, Galenus praefertim,& post ipsum Vesalius, qui tantam rem, tam illustrem, tam optatam, tam negligenter scribendam putarent, beluinum oculum pro humano dissecates. (397).

[But the eyes in other animals are not perfectly orbicular, but are either oblique or depressed: it is not difficult to tell the difference of human eyes from the eyes of beasts. Know that no one else before me describes the human eye, but instead described the eye of a beast, and this is the great basis of Vesalius’ error. Vesalius fell into deception with the others of his training in Anatomy. That this is true, it is easy to see clearly, if Galen, Vesalius, and others compare their history of the anatomy of the eye to mine. Many prefer Galen [before] and Vesalius after him that they accept such a thing, so illustrious, so longed for, to be negligently written, taking a dissected beast’s eye for a human eye.][vii]

Colombo goes on to note other errors in Vesalius’ anatomy of the human eye, saying later,

Erroresque Vesalii in historia de oculo nullo negocio deprehendes … nam non modo in musculis & membranis, sed in humoribus quoque decipitur, & tota errat via, existimans cristallinum humorem in centro oculi exquisite situm esse. (405).

[Errors in Vesalius’ history of the eye are not difficult to find … for he is deceived not only in the muscles and membranes, but also in the humors, and he completely errs [in positioning] the crystalline humor in the eye’s center.]

Detailing Vesalius’ errors, Colombo notes that Vesalius’ most grievous concerns the placement of the crystalline humor at the very center of the eye.

While criticizing Vesalius for distorting human optical anatomy through animal dissection rather than human dissection, Colombo distorts the eye in his own way.  He maintains a largely spherical eye, and while he moves the crystalline humor towards the front of the organ, he does not place it just behind the pupil at the front of the eye. But despite not placing the crystalline where modern anatomists situate the lens and while maintaining its centrality in the perceptual process, Colombo de-centers the crystalline humor within the organ.[viii] Even once Colombo’s de-centered crystalline humor became the norm, popular anatomies continued to stress the importance of its centrality to the eye as well as the importance of its and the eye’s spherical shape.

Colombo’s observations led to a new model in early modern optical anatomy which I will refer to as the “mediate early modern eye.” My second image comes from the tables attached to the 1583 edition of Felix Platter’s De Corporis Humani Structura Et Usu.

Felix Platter, who challenged theories of vision that argued the crystalline humor was the vision’s seat as early as 1583, follows Colombo in positioning the crystalline humor more towards the front of the eye. Platter was the first to argue that the crystalline humor was not the seat of vision, arguing instead for the primacy of the optic nerve and the retinal image. Kepler probably drew upon Platter’s description, but Platter did not, at least not in his text, discuss the inversion of the retinal image.  I will return to Platter’s contributions to the retinal image below, but, for now want to discuss the representations of the mediate early modern eye like his which were the most popular representations of optical anatomy from the mid-sixteenth to early seventeenth centuries.

What follows is a series of what I am calling the mediate early modern eye taken from popular vernacular anatomies printed in English from the sixteenth and early seventeenth century.

 

 

 

By far the most popular image of ocular anatomy, the mediate early modern eye persisted in various forms and copies. Most of the above examples represent copies or close approximations of one another, but George Bartisch’s 1583 German work on ophthalmology, Opthalmodouleia Das ist Augendienst, contains a flap anatomy of a very similar construction of the eye.

 

 

 

Bartisch’s figure shows a perfectly spherical eye, but also includes flaps that show the mediate positioning of the crystalline humor as well as by the aqueous humor before it and the vitreous humor behind it.

This mediate early modern eye is by far the most common in early modern anatomies from the late sixteenth century and well into the seventeenth. Not quite placed in its modern position just behind the pupil, but no longer positioned directly in the center of the eye, anatomists positioned the crystalline humor there for quite some time. What remains peculiar is that although most late sixteenth- and seventeenth-century anatomy books include representations of this mediate early modern eye, their descriptions often draw upon the Galenic eye even when they correct the errors found in the descriptions and representations of the eye like those found in Galen and Vesalius.

Even the printed version of Kepler’s manuscript conforms to the model established by this mediate early modern eye.

While Kepler himself did not provide an illustration in his manuscript, this published text did include an image that resembles the ones I posted above. I will return later in this post and in subsequent posts to the importance of Kepler’s discovery of the retinal image, but it is important to note that the figure appearing in his 1604 Ad Vitellionem paralipomena Quibus Astronomiae pars optica traditur contains the image of the mediate early modern eye.

Despite the mediate early modern eye appearing in the printed version of his Paralipomena Kepler famously challenged the primacy of the crystalline humor, arguing instead for the importance of the retina and the retinal image. As he puts it,

Visionem fieri dico, cum totius hemisphaerii mundani, quod est ante oculum, & amplius paulo, idolum statuitur ad album subrufum retinae cauae superficiei parietam. (Kepler 168)

[I say vision is accomplished, when the whole hemisphere of the world and a bit more which is before the eye, an idolum is placed on the curved, reddish-white retinal wall.]

Unseating the crystalline humor’s primacy within the eye and in the process of vision, Kepler offers the retinal image in its stead. Before I discuss Kepler more extensively, however, I would like to turn to some early modern textual descriptions of the eye as they embody the tensions between the representations of the Galenic eye and the mediate early modern eye.

Even in texts which represent the mediate early modern eye, the verbal descriptions often draw upon the Galenic eye for the significance of the organ of sight. Despite acknowledging that the crystalline humor was not at the center of the eye or in the shape of a perfect sphere, later anatomical treatises often laud it for its centrality and spherical shape. In his 1578 The Historie of Man, John Banister does the same while simultaneously registering Colombo’ corrective contribution to ocular anatomy when he describes the crystalline humor as follows:

The second humor of the eye is Christalloides; or Christallinus, called so, for because it shineth like light, and in pure clearenes comparable to the christall. The place where it is sited is towardes the forepartes, almost in the centre of the eye, beyng amplected olf the hinder part with the vitrious humor, hauyng no other Membran interiacent or lyeng betwene: but before couered with Aranea. The figure of the christalline humor is round, but in the fore part depressed: where it respecteth the watrish humor, it is lyke the kynde of a pulse called a lentill. The substaunce, of this humor is somewhat hard. The vse therof is exiellent & most noble: beyng almost the principall member of sight, pleasaunt to be marked, and worthy to be knowen, not iniuriously therfore called the idole, or Image of seeing. (Banister 102).

In Banister’s description of the eye, we see that he has corrected his optical anatomy in accordance with Colombo’s observations, but he also partly conforms to the notion that the crystalline humor lies more central to the eye and that it has a round shape though depressed on the forepart. Banister does acknowledge that the chrystalline humor only “almost” sits in the center of the eye, and notes that the lens is round but is “in the fore part depressed,” but the legacy built up around the crystalline humor’s centrality to the organ of sight remains strong in Banister’s description. Banister notes that the crystalline humor is “excellent & most noble” partly based on the notion that its centrality confirmed the nobility both of the humor and of vision in general.

Banister even refers directly to Colombo’s critique of Vesalius, translating Colombo’s attack almost verbatim. He says,

The fashion of the eyes in man is rounde: which if you marke well, you shall finde that nothyng elles in the body hath a direct rounde proportion. But in other creatures the eyes are not directly round, no, rather oblique or depressed. Neither is that marueilous, whilest the figure of man differeth from all other creatures in no small poynt. Neither more openly, then worthely, hath Realdus Collumbus reproued such as hitherto haue made description of the eyes, by frequentation of brutish Anathomies: which clearely he noteth in Galen, and after him Vesalius, whose skilfulnes in matters Anathomicall no man neglecteth: yet with no small negligence is he spotted in this point, since, so carelesly to write in a matter so great, excellent, and oft wished he blushed not. (Banister 102).

Again, Banister notes the spherical shape of the eye, going further to suggest that no other part of the body comes as close to the shape of a perfect sphere. It was the perfectly spherical shape and the crystalline humor’s centrality within it that reinforced and confirmed the eye’s connection to the macrocosm’s ordering of the heavenly spheres.

Similar to the English Banister, the same tension appears in popular works on the eye translated into English towards the end of the sixteenth century. The French physician Jacques Guillemeau, in the English translation of his One Hundred Thirteen Diseases of the Eye, describes the crystalline humor as follows:

His seat is in the middest between the waterish and glassie humor, not onlie ministring nourishment and moisture, and so preserving from drinesse, but also to helpe and preserve the same, and to moderate & appease the rage of spirites and colours, which might hurte it. The fashion of it is rounde, whiche more easily resisteth outward injuries: for this figure is hardlie hurt, because it hath no corners. It is true that the roundnesse of it is somewhat pressed and pinched before and behind, but so that therby it remaineth more sure and stedfast in the place, whiche was harde to bee done in a round figure. (Guillemeau Chapter 4).

Guillemeau does not include any illustrations, but his description appears to place the crystalline directly in the center of the eye like the Galenic eye. Even if Guillemeau is referring to the mediate early modern eye, his verbal description could give a potential reader the impression that the eye was arranged in accordance with the Galenic model. He, too, notes the centrality of the crystalline humor, providing an explanation as to why the seat of vision is not perfectly spherical.

Nearly every other work published in English on the anatomy of the eye I have found from the late sixteenth century into the early seventeenth century, when they include images, represent the mediate early modern eye, and, when they describe optical anatomy, describe the crystalline humor as the eye’s primary part, but also note its centric, or nearly centric, position within the orb of the eye. This includes works by Englishmen like John Banister, Helkiah Crooke and popular works translated from French into English like Pierre La Pimaudaye’s The French Academie, André du Laurens’ A Discourse of the Preservation of the Sight: of Melancholike diseases; of Rheums, and of Old Age, Jacques Guillemeau’s A Worthy Treatise of the Eyes, and Ambroise Paré’s Workes among others.

The crystalline humor’s centrality to a spherical eye trailed clouds of significance. I will return to some of those elements below when I discuss the treatment of the eye as a microcosm, but here want to discuss one description that casts the crystalline humor’s position in heroic terms. In 1594, French physician André du Laurens first published his Discours de la conservation de la veue: des maladies meloncholiques des catarrhes, which the English Richard Surphlet soon translated. With good reason, I quote the beautiful 1599 Surphlet translation at length:

Loe thus all vailes, shadowes and covert being taken away, it is now time to make a plaine and open shew of the most precious jewell of the eye, that rich diamond, that beautiful christall, which is of more worth than all the pearles of the East. This is that icelike humour, which is the principall instrument of the sight, the soule of the eye, the inward spectacle: this is that humour which alone is altered by colours, & receiveth whatsoever formes the things that are to be seene. This is that chirstalline humour, which in more hardie wise then Hercules, dares to encounter two at once, namely, the outward and the inward light. This is that onely christalline humour, which all the other parts of the eye acknowledge their sovereigne, and themselves the vassals thereof: for the hornie tunicle doth the office of a glasse unto it: the apple, the office of a window: the grapelike coate is as a fayre flowering garden, to cheare and rejoyce the same after wearisome labout: the cobweblike coate serveth as lead to retaine such formes as are offered: the waterish humour as a warlike foreward, to intercept and breake off the first charge of the objects thereof, assaying all upon the sudden, and with headlong violence to make breach and entrance: The vitreous humour is his cooke, dressing and setting forth in most fit sort his daily repast: The nerve opticke, one of his ordinary messengers, carrying from the braine thereto, commandment and power to see, and conveying backe againe with all speede whatsoever hath been seene: The muscles are his loftie steedes and couragious courses, whereup being mounted it advanceth it selfe aloft, casteth it selfe alow, turneth it selfe on the right and left hand: and finally in every such sort, as seemeth best unto it selfe. In briefe, this is the principall part of the eye, which I intend to describe… (Du Laurens 34).

Du Laurens positions the crystalline humor, which he later states is “placed in the middest of the eye, as in his center, to the end it may equally and indifferently intertaine and admit of both the lights” (34), as a Herculean hero and sovereign of the eye. The whole of optical anatomy serves the crystalline humor as its master, and that master engages in a mythological epic battle between two different assailants, the outward and inner lights.

The centrality of the crystalline humor to the eye reaches a metaphorical apex in du Laurens’ description, and his wonderful elaboration also exposes how the crystalline humor was seen as a type of sovereign as well as how the physical arrangement of the space within the eye could take on analogical and significance. The physical centrality and the functional centrality of the crystalline humor are intertwined not only in du Laurens’ elaborate metaphorical riffing but also in the anatomical descriptions of the eye itself. The sovereign of the eye must be spherical and central to its kingdom. Kepler would play an important role in de-centering its power further and culminating in its regicide. Before that time, however, the crystalline humor, as in du Laurens’ description, ruled the eye from a centralized seat of visual power.

I will return to the significance of metaphors du Laurens deploys below, but, before I do, I first want to discuss the final early modern eye or, simply, the modern eye. It was not until 1619 with the publication of Jesuit Christoph Scheiner’s Oculus hoc est: Fundamentum opticum that an anatomically “correct” image of the eye was printed.

This crude figure of the eye more closely resembles the eye of modern anatomy.[ix] Here, we see an eye that is not a perfect sphere with a lens that is no longer close to being central to the organ. Clearly towards the forepart of the eye, the lens nestles just behind the pupil, focusing and reflecting light on the curved surface of the retina at the rear of the eye. As I mentioned above, even Kepler’s work contains an image of the eye that differs dramatically from modern representations.

Scheiner’s work on optics verified Platter’s and Kepler’s earlier contentions that the retina rather than the crystalline humor was the central component of the eye.[x] Not only did the retinal image now dominate optical theory, but also completed the de-centering and dethroning of the eye’s previous seat of power, the crystalline humor. From this point forward, in elite science at least, the formerly mighty crystalline humor was relegated to a subservient role with respect to the retina and its retinal image.  

One can see this modern representation of ocular anatomy in my final visual example which comes from René Descartes’ text, probably the single most recognizable image of early modern optical anatomy. In this image, we find an eye must closer to the ones we find in a modern anatomy book. Not only is the lens placed much closer to the forepart of the eye, but the eye itself is no longer represented as perfectly spherical.

I will return to Descartes’ conception of vision and the importance of this figure in the second half of this essay, but his representation stands as a good example of what I will call the “modern eye,” despite the fact that it still differs in some aspects from what we think of when we turn to contemporary books of human anatomy. Descartes not only compared the human eye to a camera obscura, but also claimed the eye worked in the exact same way as the device and effectively was a camera obscura.

Descartes, like Kepler before him, accepted the retinal image and its inversion. Unlike Kepler, Descartes did not stop his investigation at the retinal image, theorizing the image from the eye at least as far as the pineal gland, and explaining that “it is the soul which sees, and not the eye; and it does not see directly, but only by means of the brain” (Descartes, Selected Philosophical Writings 68). The retinal image contributed in no small degree to Descartes’ philosophical skepticism. The disconnect established between sensation within the eye and perception in the soul dismantled theories that expressed their relationship and connection. While Descartes borrows many of his skeptical arguments from prior skeptical models, it is the retinal image that creates slightly different epistemological horizons for philosophical skepticism.[xi]

I do not mean to suggest that either Kepler or Descartes were singular geniuses that emerged from historical vacuums. Kepler continued to promote a quasi-Aristotelian understanding of the sensitive soul and Descartes not only adapted earlier skeptical motifs but also reiterated the quasi-Aristotelian model of the sensitive soul even if he pushed it beyond the pineal gland. Both figures shaped and were shaped by theories of perception available at the time of their writing.

The three corporeal eyes I discuss in the first half of this essay present the range of ocular anatomy from before 1543 to 1619, and I have shown the predominance of the mediate early modern eye in this period. Lindberg wonders what took so optical theories and ocular anatomists so long in coming to the realization that the crystalline humor functioned as a lens that projected light upon the retina when the relevant geometry and understanding of lenses were present for a long time previously. Part of the reason it took so long to discover the retinal image and correctly represent ocular anatomy has to do with the “absurdity” of claiming that the image within the eye was upside down and horizontally flipped.

In the next section, I explore the analogical and anagogical relationships developed in late sixteenth- and early seventeenth-century popular vernacular discourses that help explain what made de-centering the eye’s seat of power difficult and potentially revolutionary. These cultural beliefs, I suspect, made recognizing the correct position and function of the crystalline humor so difficult even beyond the absurdity of the retinal image and its inversion.

Broader cultural beliefs and practices shape early modern discourses on vision. The very notion that the eye must contain a species or image that conforms to the visual plane before it or as it is perceived in the mind was the biggest obstacle for early modern theorists of optics to overcome, but other discourses shaped their own perception of the eye. One wonders, for example, why Colombo and those who represented the mediate early modern eye not only emphasized a perfectly spherical shape to the human organ of vision and why, even when de-centering the position of the crystalline humor, they continued to place it, not towards the forepart of the eye, but more towards its center.

One explanation is that when early modern anatomists looked at the eye’s interior, they saw a radically different eye than modern anatomists. They saw within it a microcosm of the macrocosm. They saw an organ whose central functional component should occupy the organ’s physical center, and whose other parts were arranged in relation to and served this “sovereign” within the eye. The legacy of discourses that proclaimed the crystalline humor’s superiority and sovereignty shaped their own perception of the anatomized human eye. Even when they recognized, following the period of Vesalius, that the crystalline humor was not in the exact center of the orb of the eye, cultural discourses shaped their thought and perception in such a way as to construct the mediate early modern eye.

The anatomists’ shaping of sense also influenced and affected the recognition of the retinal image and its inversion. Not only did they see the crystalline humor as the eye’s seat of vision, but it was also imperative that the image within the eye conform to the orientation of the visual field and the way in which the mind perceived that visual field, and such an a priori stance obstructed the retinal image and its inversion’s acceptance. Even though many theorists of optics were probably aware of the camera obscura, they did not directly argue that the eye worked exactly like a camera obscura until much later since it was known that the camera obscura projected an inverted image upon a screen placed behind it. In the next section, I will go on to discuss the retinal image and inversion as well as the ways popular vernacular discourses published in or translated into English shaped and were shaped by ocular anatomy.

Works Cited

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Clark, Stuart. Vanities of the Eye. Oxford: Oxford University Press, 2009.

Colombo, Realdus. De re Anatomica libri XV. Paris: Apud Andream Wechelum, sub Pegaso, in vico Bellouaco, 1562.

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Lindberg, David C. Theories of Vision from Al-Kindi to Kepler. Chicago: University of Chicago Press, 1981.

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Platter, Felix. De Corporis Humani Structura et Usu. Libri III. Basil: Per Ambrosium Frob., 1583.

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Spruit, Leen. Species Intelligibilis: From Perception to Knowledge. Volume Two: Renaissance Controversies, Later Scholasticism, and the Elimination of the Intelligible Species in Modern Philosophy. New York: Brill, 1995.

Summers, David. Vision, Reflection, & Desire in Western Painting. Chapel Hill, North Carolina: The University of North Carolina Press, 2007.

Tachau, Katherine H. Vision and Certitude in the Age of Ockham. Optics, Epistemology, and the Foundation of Semantics. Amsterdam: Brill, 1988.

Tomkis, Thomas. Lingua, or the Combat of the Tongue and the Five Senses for Superiority. London: G. Eld for Simon Waterson, 1607.

Vesalius, Andreas. De Humani Corporis Fabrica. Venice: Apud Franciscum Franciscium & Joannem Criegher, 1568.

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