‘The Eyes contain’d within these Orbits or strong Dens, for their better preservation are cover’d with the Eye-lids, as with Curtains, to keep out Dust, troublesome Smoak and Vapors, as also the Excess of Light and the Injuries of the Air, and is moisten’d, wip’d and cleans’d by the Corneous Tunicle to render the Sight more bright and clear’.
Ysbrand van Diemerbroeck, The Anatomy of Human Bodies … Translated … by William Salmon (London, 1689), p. 463.
According to Galen of Pergamon in his treatise ‘On the Anatomy of the Eye’, the eye was composed on seven layers and seven ocular muscles. Vesalius (1514–64), in the main, concurred, accepting Galen’s designation of seven cranial nerves. His work on the eye, and that of the early modern anatomists who came in his wake, demonstrate the difficulty of correctly anatomizing the eye in the early modern period. An example of contemporary knowledge of the workings of the eye may be found in a popular textbook of the period, Ysbrand van Diemerbroeck’s Anatome corporis humani, which Worth owned in a 1669 Genevan Latin edition.
Ysbrand van Diemerbroeck, Anatome corporis humani, plurimis novis inventis instructa variisque observationibus … adornata (Geneva, 1679), Tab XI: how the eye works.
In his textbook on human anatomy, the Dutch anatomist Ysbrand van Diemerbroeck (1609–74) not only outlined his teaching on the structure of the eye, but also commented on how the eye works. Diemerbroek explained the structures of the eye, illustrated in the above plate, as follows:
‘FIGURE I. The Exterior Parts of the Eye.
AAAA, THE Skin turn’d back,
BB, The bigger Muscle of the Orbicular Eye-lid.
C, The Tendon of the same in the wider corner of the Eye.
DD, The lesser Muscles of the Eye-lids.
EE, The Brows of the Eye-lids.
G, H, The upper and lower Eye-lid.
I, The larger Corner.
K, The lesser Corner.
L, The Conjunctive Tunicle.
M, The Corneous Tunicle.
FIGURE II. The Muscles and Nerves of the Eye.
AAAA, The Cranium cut open.
BB, A portion of the dissected Brain.
CC, The Cerebel.
D, The meeting of the Optic Nerves.
EE, Their Progress to both Eyes.
GG, The first Muscle of the Eye, called the Attollent.
H, The second Muscle of the left Eye, called the Depressor.
II, The streight inner Muscles, or drawers to, in each Eye.
KK, The external streight Muscles or drawers from each Eye.
L, The fifth Muscle of the left Eye, or the External Oblique.
MM, The sixth Muscle or Internal Oblique, the Tendon of which passes through the Trochlia, N.
O, The Optic Nerve of the right Eye.
P, The Corneous Tunicle in the midst of which is the Apple.
AA, The Cranium resected.
BB, The Cerebel.
CCCC, The Dura Mater.
D, A portion of the dissected Brain.
EE, The Sprig of the Optics.
F, Their concourse.
GG, Their separation.
H, The general Original of the Muscles.
II, The Muscle of the Eyelid in its place.
K, The streight Muscle drawing the Eye outward.
L, The streight Muscle moving the Eye upward.
M, The third right Muscle moving the Eye-downward.
N, The last right Muscle drawing the Eye to the inner Parts.
OO, Branches of the Motory Nerve inserted into the Muscles.
PP, The Globeous Body of the Eye it self prominent under the Muscle of the Eye-lid.
Q, The upper Eye-lid with its Hairs.
R, The Bone broken off.
S, The Body of the left Eye.
T, The Muscle of the upper Eye-lid, out of its place turn’d back.
FIGURE IV. The Eye-brow and Eye-lids.
AA, The hairy Eye-brow.
BB, The fat of the Eye-brow.
CCCC, The inner superficies of the Eye brows.
DDD, The Gristle of the Eye-brows.
E, The upper edging of Hair.
F, The lower edging of Hair.
AA, The Muscle of the upper Eye-lid in it’s place
BB, The Gristle of the Eye-brow.
C, The place of the Eye-lid cut off.
D, The hairy edging of the upper Eye-brow.
AA, The Muscle of the upper Eye-lid.
BB, The Gristle of the same Eye-brow.
C, The Hairs.
A, The Nerve of Optic.
B, The Motory Nerve.
C, The rise of all the Muscles.
D, The Trochlear Muscle.
E, The Trochlea or Wheel.
F, The string of the Trochlear Muscle.
G, The Internal streight Muscle.
H, The External streight Muscle.
I, The Muscle of the upper Eye-lid.
KK, The remainder of the Eye-lids cut off.
L, The hairy Edgings.
AAA, The Gristle of the Eye-lids taken out.
B, The Hairs of the upper Eye-brow.
C, The Hairs of the lower Eye-brow.
A, The Corneous Tunicle, with the transparent Apple.
B, The streight Muscle Attollent.
C, The streight Muscle depressing.
D, The inner Muscle bringing to.
E, The External Muscle drawing from.
F, The inner Oblique, or Trochlear.
G, The outter Oblique, or lower.
A, The Optic Nerve.
B, The seventh Muscle proper to many Brutes surrounding the Eye.
CCCC, The streight Muscles.
D, The Trochlear Muscle.
E, The lower Oblique Muscle.
A, The Optic Nerve.
B, The Original of the Muscles.
C, The streight lateral Muscle.
D, The upper streight Muscle.
E, The other streight Muscle.
FF, The Fat of the Eye hiding the Muscles and the Optic Nerve.
G, Part of the Skin of the upper Eye∣lid cut off.
HH, The Sclerotic Tunicle of the Eye.
I, The Corneous Tunicle.
K, The Apple of the Eye.
L, The Hair of the lower Eye-brow.
MM, The lower Eye-brow.
The Annate Tunicle separated and out of place, furnished with several minute Veins and Arteries.
The Christalline Tunicle.
The Chrystalline Humour and its Figure.
The Watry Humour.
The Vitreous Humour receiving the Chrystalline in the middle.
A, The Optic Nerve.
BB, The Choroides Tunicle laid bare from the Sclerotic.
CCCC, Veins depressed through the Sclerotic.
DD, The Sclerotic inverted.
E, The Rupture of the Sclerotic.
A, The Optic Nerve.
BB, The Dura Mater surrounding the Optic.
CC, The Sclerotic opened, shewing the Nerves through the Fissure.
A, The Optic Nerve.
BB, The Uveous folded back, and partly separated from the Net-like.
C, Part of the Net-like separated from the Uveous.
A, The Net of the Tunicle bare.
B, The Conjunctive Tunicle, or the White of the Eye.
C, The Corneous.
D, The Apple of the Eye’ 
As the title of his work suggests, Diemerbroek sought to be as up-to-date as possible, incorporating, as the title notes, ‘the most modern discoveries’. However, it was not until Antoni van Leeuwenhoek (1632–1723) trained his microscope on the eye that it began to be correctly described.
William Briggs, Ophthalmographia, sive Oculi ejusque partium descriptio anatomica; nec non, ejusdem Nova visionis theoria, Regiae Societati Londinensi proposita (Leiden, 1686), Tab II, figs 1, II and III.
Worth did, however, possess an important text which, unlike Diemerbroek’s textbook, concentrated solely on the eye. The English oculist William Briggs (c. 1650–1704), originally published his anatomy of the eye in 1676, under the title Opthalmographia and in 1681 communicated a text on his theory of vision to the Royal Society, where it was well-received (and, indeed, well-thought of by Worth’s scientific hero, Isaac Newton (1642–1727)). In fact, James suggests that it was from Briggs that ‘Newton derived his anatomical knowledge’. Worth’s Leiden edition incorporated both works and the above image comes from Briggs’ Nova Visionis Theoria. In it Briggs made valuable comments on the role of the optic nerve in vision, and, as James notes, Briggs tried ‘to show that the fibres of the optic nerve as rising from the two protuberances of the thalami optici are more concerned in vision than either cornea, humours, or retina’.
Giovanni Battista Verle, Anatomia artifiziale dell’occhio umano, inventata, e fabbricata nuovamente (Amsterdam, 1680), Fig II and p. 52; and the artificial eye made by Giovanni Battista Verle of Venice., now in the Wellcome Collection. Attribution 4.0 International (CC BY 4.0).
Worth also possessed a rather more unusual text on the eye, Giovanni Battista Verle’s Anatomia artifiziale dell’occhio umano, inventata, e fabbricata nuovamente (Amsterdam, 1680), in which Verle, a seventeenth-century Italian instrument maker, turned his attention to producing an artificial eye. With the assistance of Antonio Molinetti (d. 1675), a professor of anatomy at the University of Padua, he had produced a model in Venice, and subsequently produced one in Florence at the behest of the librarian of the Grand Duke, Antonio Magliabecchi (1633–1714), and Giuseppe Zambeccari (1659-1729), a professor of anatomy at the University of Pisa. This Florentine eye, which Verle presented to the Grand Duke of Tuscany, Cosimo III de Medici (1642–1723), was modelled in ivory and is now among the collections of the Wellcome Trust.
Clastic model of the eye with a glass vitreous chamber and lens, late 19th century. Courtesy of the Old Anatomy Museum, School of Medicine, Trinity College Dublin.
Model makers employed a variety of materials to represent the anatomy of the eye; wax, plaster, and wood were often used, as well as papier-mâché and cork, but none was quite as suitable as glass. The designer of this Bock-Steger-Lips model of the eye incorporated blown glass to represent the vitreous body and the ocular lens. This primarily polychrome plaster model is clastic, meaning that it can be taken apart to reveal inner structures. While not sophisticated in detail or precision, this type of model would be useful to educators teaching the basic structure of the human eye to students.
Bock-Steger was a manufacturer of scientific models based in Leipzig, Germany, active in the late nineteenth and early twentieth centuries. Models made by the company can be found in medical heritage collections all over the world, including Trinity College Dublin (see Tongue), and the Harry Brookes Allen Museum in Melbourne.
Text: Dr Elizabethanne Boran, Librarian of the Edward Worth Library, Dublin, and Ms Evi Numen, Curator of the Old Anatomy Museum, Trinity College Dublin.
De Laey, Jean J., ‘The eye of Vesalius’, Acta Ophthalmologica 89, no. 3 (2011), 292–300.
James, R.R., ‘William Briggs, M.D. (1650–1704), ‘The British Journal of Opthalmology, 16, no. 6 (1932), 360–68.
Kaplan, Barbara Beigun, ‘Briggs, William (c. 1650–1704), physician and oculist’, ODNB, 2004.
Spencer, Lucy, The Artist’s Knife: The art and science of plaster anatomical models at the Harry Brookes Allen Museum of Anatomy and Pathology, The University of Melbourne, A Historiography and Catalogue, School of Historical Studies, Monash University, Public History Project.
Van Diemerbroeck, Ysbrand, The Anatomy of Human Bodies … Translated … by William Salmon (London, 1689).
 This English translation is not in the Edward Worth Library.
 De Laey, Jean J., ‘The eye of Vesalius’, Acta Ophthalmologica 89, no. 3 (2011), 292.
 Van Diemerbroeck, Ysbrand, The Anatomy of Human Bodies … Translated … by William Salmon (London, 1689), Sig. d1v-d2v.
 James, R.R., ‘William Briggs, M.D. (1650–1704), ‘The British Journal of Opthalmology, 16, no. 6 (1932), 361.
 Ibid., p. 366.
 Spencer, Lucy, The Artist’s Knife: The art and science of plaster anatomical models at the Harry Brookes Allen Museum of Anatomy and Pathology, The University of Melbourne, A Historiography and Catalogue, School of Historical Studies, Monash University, Public History Project.