Sight unseen: vision and perception in Leonardo's Madonnas: in the first of two articles on Leonardo da Vinci, Larry J. Feinberg explains how the artist's interest in the way the eyes work influenced his realistic depictions of the Christ Child as a baby learning to see

In recent years a number of scholarly studies have investigated and elucidated the complex intersection of Leonardo da Vinci's art with his other intellectual pursuits. (1) Understandably, these inquiries have concentrated primarily on Leonardo's notebooks and on his major religious compositions. Somewhat overlooked have been ways in which Leonardo's scientific and literary interests, such as those in optics and visual puns, informed a few of his smaller religious works, particularly his paintings of the Virgin and Child.

Careful examination of two of Leonardo's early compositions, the Madonna with the Carnation, of about 1475-78, in the Alte Pinakothek, Munich (Figs. 1 and 2), and the Benois Madonna, of about 1478-80, in the Hermitage, St Petersburg (Fig. 3), reveals his nascent interest in the physiology of vision and of perception--subjects that would, a decade or so later, become central to his research. The awkward naturalism of the anatomy and movement of the babies in the two works, and in the preliminary studies for them, has always been noted, as has Leonardo's evident observation of actual infants. But only brief, bemused reference has been made to the visual and psychological ungainliness of the Christ Child in the Munich painting and of the tentative actions of his counterpart in the Hermitage work. An advocate of experience over theory, Leonardo was determined to record with accuracy what he saw, even though his limited comprehension of the operations of sight could not account for the behaviour of the very young models he studied for the two pictures. In the Munich painting, the artist has rendered the child, eyes straying and unfocused, reaching almost blindly for the Virgin's carnation. In what can almost be regarded as a further elaboration on the activities of the Munich infant, Leonardo portrays the older child in the Benois Madonna as gamely trying to focus his eyes on a sprig of flowers, as he pulls his mother's hand toward him.

[FIGURES 1-3 OMITTED]

Leonardo's sensitive observations of the children's actions resulted in touching and credible portrayals of familial interaction. But for the painter these observations also created a slight conundrum. For no one in the later fifteenth century, including Leonardo, understood the workings of the lenses of the eyes and, therefore, truly comprehended the behaviour of an infant struggling with his eye-hand coordination. In fact, full knowledge of the function of the eyes' lenses would only be attained in the mid-nineteenth century, with the researches of the German psychophysicist H.L.F. von Helmholtz. In his Physiological Optics (about 1856-66), Helmholtz explained for the first time exactly how the human eye focuses, as the ciliary muscles adjust the curvature of the anterior surface of the lens. (2) Moreover, he pointed out how the pupil contracts (limiting light and vision) when the lens accommodates for near objects and when there is a strong convergence of the two eyes--facts no less pertinent to Leonardo's depiction of the child in the Benois Madonna. (3)

Since Helmholtz's discoveries, much more has come to be known about the physiology of sight and the neurological development of the brain and eyes of an infant. Relatively recent neuroscientific studies have shown that a baby's ability to focus has less to do with the development of motor skills than with its body's natural production of the chemical myelin, which is necessary for the conduction of nerve impulses within the brain and to the eye. (4) A child usually does not develop the myelinated nerve tracks (axons) that are required for 20/20 visual acuity until the age of eighteen to twenty-four months. (5)

Of additional relevance to Leonardo's infants is the ongoing research of neurological scientists that is beginning to reveal how the brain processes visual information. (6) This work has determined that separate cortical areas of the brain are responsive to different kinds of visual information--that is, one area of the cerebral cortex is sensitive to the spatial orientation and motion of lines, another acts as the principal receptor for colour, a third area is the main analyser of form, another serves as the chief organiser and analyser of colour, and a fifth registers the movement of objects. (7) Such a complicated, highly-integrated, and interactive system, known as 'modular organisation' (in reference to the individual and distinct modules or subsystems of the brain), requires substantial neurological wiring to function properly. An infant's inchoate neurological state does not permit the full operation of this system. (8) Further, modular organisation also involves the subtle processing of incoming visual data through the filter of experience and memory, in which infants are limited as well. (9)

Not only was such information about neurology and the lenses of the eyes centuries beyond Leonardo's reach, but, in the 1470s, the artist had little ability in Latin, and so even the writings of the medieval authorities on optics, Alhazen, Pecham, and Witelo were largely inaccessible to him. (10) Consequently, when he created the Munich and Benois Madonnas, he had only rudimentary ideas about the mechanics of sight, probably learned primarily from the writings of the architect and art theorist Leon Battista Alberti. (11) Following Alberti, Leonardo, at least into the 1490s, adhered to the Platonic theory of emission in the operations of sight--the belief that the eyes emit rays that extend to the object seen. (12) (This is, of course, contrary to the true nature of sight, which involves intromission, the reception of light from all object into the eyes.) Leonardo speaks of these fanciful visual rays in one of his earliest surviving notes on optics, on a sheet at Windsor Castle (about 1483-85; no. 19148): 'I say the eye projects an infinite number of lines, and these attach themselves to or mingle with those that come towards it which emanate from the things seen.' (13) A fuller explanation of this imaginary phenomenon was provided by Alberti in his Treatise on Painting, from which it is useful to quote at length:

   These rays, stretching between the
   eye and the surface seen, move
   rapidly with great power and
   remarkable subtlety, penetrating the
   air and rare and transparent bodies
   until they encounter something
   dense or opaque where their points
   strike and they instantly stick ...
   Vision takes place by means of a
   pyramid of rays ... The base of the
   pyramid is the surface [of the object]
   seen and the sides are the [outer]
   visual rays ]which] are called
   'extrinsic.' [The 'median rays'
   comprise] the mass of rays
   contained within the pyramid and
   enclosed by the extrinsic rays ... We
   call the 'centric ray' the one which
   alone strikes the quantity in such a
   way that the adjacent angles on all
   sides are equal. As for the properties
   of the centric ray, it is of all the rays
   undoubtedly the most keen and
   vigorous ... [T]his ray alone is
   supported ... by all the others, so that
   it must rightly be called the leader
   and prince of rays. [In the distance
   and position of the centric ray are
   changed, the surface appears to be
   altered ... [S]o the position of the
   centric ray and distance play a large
   part in the determination of sight. (14)

Alberti has here applied some of the geometric elaboration of Euclid's Optics to the visual rays (opseis) that Plato described in the Timaeus as an ocular 'fire' mixing in sympathy with external light. (15) Based upon what he had gleaned from Alberti, Leonardo probably assumed that the curious actions of the babies he observed were their attempts to align the flowers before them with the centric rays of their eyes. These rays, according to Leonardo (Codex Allanticus, fol. 85v, about 1483), would have then transmitted the visual information directly to the optic nerve (what he called the 'perforated nerve'), through which the images supposedly passed to a fictive area of the brain known as the 'imprensiva' for processing. (16)

Despite the seductive simplicity of this scheme, Leonardo nevertheless realized that Alberti's visual pyramid offered a model only for a single eye's viewpoint, and not for normal, binocular vision. To help himself understand this complication of sight, he, typically, drew some diagrams--of eyes and optical rays--on a sheet of his preliminary studies for the Benois Madonna, (Figs. 4 and 5). (17) The sketches, along the right side of the recto of a double sided page preserved in the British Museum, were executed in Leonardo's usual right to left manner and should be read accordingly (Fig. 4). The drawing at right represents, schematically, parallel rays emitted from a pair of eyes that look directly forward. The next sketch illustrates the paths of intersecting rays from eyes turned only slightly inward. And, finally, the left drawing shows the intersection point of centric rays from eyes turned markedly inward. (18)

[FIGURES 4-5 OMITTED]

This last diagram is in keeping with the eyes of the Christ Child in the Benois Madonna, who, it would seem, assertively guides the hand of his mother, so that the flowers will be brought into the crossing of his centric rays. This sequence of optical sketches would thus appear to serve as a gloss or technical note on the studies of the Virgin and Child on both sides of the sheet, since those entail a progression in which the flower is brought increasingly close to the child's eyes.

While this may be one of the first instances in which Leonardo, in his art, considered how intimate, binocular vision affects perception, he continued to concern himself with related issues for decades. Leonardo wrote on another page in the Codex Atlanticus (fol. 136b, about 1483-85): 'If the eye is required to look at an object placed too near to it, it cannot judge it well--as happens to a man who tries to see the tip of his nose. Hence, as a general rule, Nature teaches us that an object can never be seen perfectly unless the space between it and the eye is equal, at least, to the length of the face.' (19) In his short treatise On the Eye (so-called Manuscript D) of about 1508, Leonardo also noted the limits of Albertian optics for binocular vision by pointing out how, when objects are placed too close to the eyes, they will appear either 'transparent' or too small. (20) He described as well the optical distortions, known as the 'blurred-edge' and 'moving-needle' effects, produced when an object comes into very close proximity to the eyes. (21) Despite these thoughtful investigations, Leonardo, like three centuries of scientists who followed him, never came to understand stereoscopic vision, which, somewhat surprisingly, was not discovered until 1838, when the English physicist Charles Wheatstone invented the stereoscope. (22) Thus, for Leonardo, the perception of stereometric volume, like his Christ Child's struggle for ocular focus, ultimately remained a mystery.

Perhaps not coincidentally, in both early paintings, Leonardo's Virgin brandishes an oval, pearl-framed brooch with a large, light-green stone, probably an emerald, which was believed from ancient times through the renaissance to aid eyesight. In his treatise On Stones (about 312 BC), the Greek philosopher Theophrastus, who succeeded Aristotle as head of the Lukeion 'school', alleged that emeralds were good for the eyes, noting that some people carried emerald seals with them for intermittent, salutary viewing. (23) Pliny the Elder, in his Natural History (first century AD), agreed, commenting that 'after straining our sight by looking at another object, we can restore it to its normal state by looking at a "smaragdus" (emerald).' (24) He added that gem engravers kept some emeralds aside on their worktables for refreshing their eyes, 'so soothing to their feeling of fatigue is the mellow green colour of the stone.' Centuries later in renaissance Florence, Marsilio Ficinn expanded the list of objects that held therapeutic value for the eyes to include all smooth, green materials. (25) The belief that emeralds benefitted weak eyesight persisted into the early seventeenth century; in his poem, 'A Lover's Complaint' (1609), William Shakespeare wrote: 'the deepe greene Emrald in whose fresh regard, weak sights their sickly radience do amend.' (26) Thus, the green stone, placed very close to the eyes of the infant in each of Leonardo's pictures, would have been regarded as a ready, corrective agent for the Child's obvious eyestrain. (27)

In the context of the two early Madonnas, Leonardo's notions about the mechanics of vision have interesting implications. Leonardo and his immediate artistic predecessors and contemporaries, such as Botticelli and Raphael, often poignantly treated the theme of divine foreknowledge of the Passion in their Madonnas--the Christ Child is sometimes shown recoiling from, or willingly embracing, a goldfinch (as in the Leonardo-school Madonna Litta in the Hermitage) or some other Passion symbol, and the Virgin is often presented as wistfully prescient of her child's fate. In a sense, Leonardo, the empiricist, in his two paintings sought to break down and analyse the physiology of vision and perception, the connections between sight and insight. In the Munich painting, the Christ Child can hardly see, but seems instinctively aware of the carnation, a traditional symbol for the nails of Christ's cross. (28) The child of the Benois Madonna has yet to respond to the cruciform shape of the flower, because he has yet to see it clearly. (29) Once that happens, the child's hazy curiosity could, presumably, lead to foresight of his sacrifice. By adding this explicit reference to the act of seeing, Leonardo has thus protracted and compounded the tension inherent in portrayals of the Christ Child apprehending his death. Leonardo, who disparaged those who attempted to simplify the workings of nature, would carry on these researches and themes concerning vision and insight in his next major project, the Adoration of the Magi for S Donato a Scopeto (1481, Uffizi).

Even in its unfinished state, the highly-ideated conception of that work (Fig. 6), which is spatially organised according to the perceptions of the actors and their degrees of enlightenment, is apparent. The three Magi, who recognise the infant as the Saviour, form a compact triangle with the Virgin and Child on the surface (or picture plane) of the painting; those with an instinctive but unspecified awareness of the infant's divinity create a semi-circle, excavating a shallow space, around this triangle--some appear disoriented, others seem blindly to gaze, eyes shielded, into a bright light; the heroic figures at each corner of the composition search for answers to explain this mysterious spiritual presence: the older man at left, iii deep contemplation, looks within; the young man at right, possessing less knowledge of the world, looks without. At centre, one figure recoils as a young tree springs from age-old rocks, a double allusion to the wooden cross on Golgotha and the new spiritual life on earth under Christ. Removed from the sacred knowledge and geometry of the lower half of the composition, the background figures co-exist within a discrete and mathematically-generated perspectival space, unobservant and wholly ignorant of the historical event before them. (30) The themes to which Leonardo alluded in his early Madonnas now serve, in a brilliant summation, to integrate the entire structure and narrative of his work.

[FIGURE 6 OMITTED]

I would like to thank Start Siegele, Dr John E. Gedo, and Allan M Burke MD, as well as Constance Markey, Elizabeth Stepina, and Kristine Nielsen for their assistance in the preparation of this article

(1) Prominent among them is Martin Kemp, Leonardo da Vinci: The Marvellous Works of Nature and Man, London, Melbourne, and Toronto, 1981

(2) James RC Southall (ed.), Helmholtz's Treatise on Physiological Optics, translated by the editor, New York, 1962, vol. I, pp. 143-61

(3) Ibid., vol. I, p. 161, vol. II, pp. 395-96, and vol. III, p. 55.

(4) Eric P. Kandel, James H Schwartz. and Thomas M. Jessell. Principles of Neural Science. New York. 2000. pp. 22-23, 68-86, and 500-501

(5) Creig S. Hoyt. Bonnie Lynn Nickel, and Frank A Billson,

'Ophthalmological Examination of the Infant. Developmental Aspects', Survey of Opthamology. Vol. XXVI (January/February 1982). Pp. 181-82 Studies indicate that an infant usually establishes binocular ability (use of both eyes in coordination) by the age of 2 months, full accommodation (operation of the lenses) by 3 to 4 months, and complete usual acuity after 18 months (see pp. 179. 181-82, 185) Because, for obvious reasons, very limited experimental research has been performed on infants, our knowledge of the timing of this development is imprecise.

(6) Kandel, et al., op. cit., pp 492-589.

(7) Ibid, pp. 496-505, and Makota Iwata, 'Creativity in Modern Painting and the Cerebral Mechanism in Vision', in Jerome A. Winer (ed.), The Annual of psychoanalysis, Hillsdale, New .Jersey and London, 1996, pp. 113-16.

(8) Hoyt, et al., op cit., pp 181-82.

(9) See Kandel, et al., op. cit., pp. 492-96 and 504-505 for the roles of memory and gestalt in perception. That vision cannot exist without prior knowledge and Judgement was recognised by the medieval Arabic scholar Alhazen (see The Optics of Ibn al-Haythan, translated by A.I. Sabra. London. 1989. vol. II P. 62

(10) Kemp. op. cit., pp. 103-106 and 130-31. By the 1490S. Leonardo had some familiarity with these medieval sources As D S Strong was the first to point out, the artist closely paraphrased the opening verses of Pecham's Perspectiva communis on a page in the Codex Atlanticus (fol. 203r) of c. 1492. See Donald Sanderson Strong. Leonardo on the Eye. PhD thesis. University of California. La 1967. Now York and London. 1979. pp XLIII-XIIV; Edward MacCurdy. The Notebooks of Leonardo da Vinci. New York., 1938. vol. II, pp. 36.5-86; and David C. Lindberg, John Pecham and the Science of Optics: Perspective communis, Madison, Milwaukee, and London, 1970, pp. 60-61.

(11) Leonardo's interest in optics is manifest as well in other details of the Munich picture. In what was in certain ways a standard, Verrocchio-workshop product, Leonardo sought to demonstrate his mastery of optical effects--in the rendering of the atmospheric perspective of the distant landscape, in the light-refractive, crystal vase, and in the translucent glass spheres hanging from the corner of the pillow.

(12) Kemp, op. cit., pp, 130-31, and idem, The Science of Art, New Haven CT, 1990, pp. 44-47.

(13) Kenneth Clark and Carlo Pedretti, The Drawings of Leonardo da Vinci in the Collection of Her Majesty the Queen at Windsor Castle. London and New York, 1969, vol. III, pp. 56-57, and see Martin Kemp, 'Leonardo and the Visual Pyramid', Journal of the Warburg and Courtauld Institutes, vol. XL, 1977, p. 129, and James S. Ackerman, 'Leonardo's Eye', Journal of the Warburg and Courtauld Institutes, vol. XLI, 1978, p. 127. Leonardo reiterated this opinion several years later on a page in the Codex Atlanticus (c. 1485-90; fol. 270 v.c.); see MacCurdy, op. cit., vol. I, p. 249, and Kemp, op. cit. in n. 1 above, p. 130.

(14) Leon Battista Alberti, On Painting and Sculpture, edited and translated by Cecil Grayson, London, 1972, p. 41.

(15) Elaheh Kheirandish, the Arabic Version of Euclid's Optics, New York, 1999, vol. I, pp. 2-4, vol. II, pp. 15-19; and Plato: Timaeus, Critias, Cleitophon. Menexenus, Epistles, translated by R.G. Bury, Cambridge, Mass., and London, 1999, line 45, pp. 101-102.

(16) Kemp, op. cit. in n. 1 above, p. 130 and fig. 17; idem, op. cit. in n. 12 above, pp. 46-47, fig. 77 and p, 50, fig. 85; end Leonardo da Vinci, II Codice Atlantico della Biblioteca Ambrosiana di Mileno, transcription by Augusto Marinoni, Florence, 2000, fol. 232, vol. I, p. 365. Also see Leonardo's notes on fol. 270 of the Codex Atlanticus in MacCurdy, op. cit., vol. I, p. 252: and Kemp, op. ctr. in 1 above, p.130, fig. 17. In reality, visual information is not transmitted to the area where the optic nerve attaches to the retina, which is called the 'blind spot,' but to the 'yellow spot' (fovea) located on the retina above the entrance to the optic nerve. For Leonardo's ideas and drawings (Windsor 12603, 12626, and 12627 [c. 1493-94], 12602 [c. 1504-08], 19052 [c. 1489], and 19070 [c. 1508], and Schlossmuseum, Weimar [c. 1506-1508]) concerning the transmission of visual information to the imprensiva, see Clark and Pedretti, op. cit., vol. I, pp. 122, 123, and 130, vol. III, pp. 22 and 29; Kenneth D. Keele and Cado pedretti, Leonardo da Vinci: Corpus of the Anatomical Studies in the Collection of Her Majesty the Queen at Windsor Castle, London and New York, 1979, vol. I, pp. 164-67; Kenneth D. Keele, Leonardo da Vinci's Elements of the Science of Man. New York and London, 1983, pp. 69-71 and 76, figs. 2.32, 2.33, and 2.40; and Kemp, op. cit. in n. 1 above, pp. 125-31. In Leonardo's imaginative, neo-Aristotellan, three-ventricled scheme of the brain, the imprensiva, supposedly the receptor of impressions, may have been his designation for the cingulate gyrus. Alberti, op. cit., p. 41, chose to avoid the issue of post-ocular transmission.

(17) British Museum, no. 1860-6-16-100. See Carmen Bambach et al., Leonardo da Vinci: Master Draftsman, exh. cat., Metropolitan Museum of Art, New York, 2003, no. 20, pp. 296-300. The studies are executed in matalpoint, pen and ink, and wash. The optical diagrams are executed in the same leadpoint as the underdrawings of the Virgin and Child studies on both recto and verso and so most likely preceded Leonardo's application of pen and ink. I am grateful to Dr. Bambach and Hugo Chapman for permitting me to examine the sheet closely after its deinstallation from the Leonardo exhibition at the Metropolitan Museum.

(18) These early optical sketches would seem to be the less evolved predecessors of the diagrams concerning binocular vision that appear on sheets at Windsor (fols. 19102r, 19117r, and 19147v) and in Manuscript D (fols. 4r and 8v). See Clark and Pedretti, op. cit., vol. III, pp. 40, 46 (reproduced upside-down), and 56-57; and Strong, op. cit., pp. 58-59 and 80-81. The two drawings beside the optical diagrams on the British Museum sheet--a design for Some sort of instrument with wires or strings that (by means of a sliding mechanism?) can be manipulated to form various angles, and a crude sketch that resembles half of a spoked wheel (with a complete central circle)--are similar to small studies on one of the Windsor sheets (tel. 19117r). Because those Windsor diagrams illustrate Leonardo's understanding of physiological diplopia, or double vision, one must wonder if the study for the variable-angle contraption and 'spoked half-wheel' (eye emitting rays?) sketch relate to Leonardo's optical investigations as well. See Keele, op. cit., pp. 208-10, and for other optical diagrams similar to the 'spoked haft-wheel', see Codice Atlantico/Marinoni. fol. 331r, vol. I, pp. 572-73; and A. Philip McMahon (ed.), Leonardo da Vinci, Treatise on Painting, translated by the editor, Princeton, 1956, vol. I, pp. 95-96, and vol. II, fol. 70v.

(19) Jean Paul Richter, The Literary Works of Leonardo da Vinci, London, 1883, vol. I, p. 20, no. 25; and Codice Atlantico/Marinoni, fol. 380, vol. II, p. 662.

(20) The 'transparency effect' is described in Manuscript D (fol. 6v); see MacCurdy, op. cit., vol., I, p. 239, and Kemp, op. cit. in n. 1 above, pp. 326-27, fig. 92. The problem of objects appearing too small at very close range is noted by Leonardo in the margin of tel. 4r of Manuscript D. See Strong. op. cit., p, 59.

(21) For the 'blurred-edge' effect, discussed In Manuscript D (fol. 10v) and in the Trattato della Pittura, see Kemp, op. cit. in n. 13 above, p. 147; Strong, op. cit., pp. XXXV and 92-93; and Kemp, op. cit. In n. 1 above, pp. 326-27, fig. 93. For the 'moving-needle' effect (MS D, fol. 6v), see MacCurdy, op. cit., vol. I, p. 240, and Kemp, op, cit. in n, 1 above, pp, 327-28, fig. 94. In Manuscript A (c. 1492), Leonardo presented other examples of optical distortions caused by close viewpoints. See Ackerman, op. cit., pp. 110-t4.

(22) Brian Bowers, Sir Charles Wheatstone FRS, 1802-1875, London, 2001, pp. 45-54.

(23) Earle R. Galley and John F.C. Richards, Theophrastus on Stones, Columbus, Ohio, 1956, lines 23-24, pp. 50, and 97-100; and see Georgia L Irby-Massie and Paul T. Keyser, Greek Science of the Hellenistic Era: A Sourcebook, London and New York, 2002), p. 229. The faint, muddied appearance of the green stones in Leonardo's Madonnas is probably due to the Painter's use of a copper-green pigment, which has changed with age. Of the green pigments available in the renaissance, Leonardo in his Treatise on Painting discusses only copper green, emphasising its fugitive nature. See McMahon (ed.), op. cit., vol. I, pp. 91-92 and vol. II, pp. 67v-68v. Neither the Hermitage nor the Munich museum have conducted pigment analyses of the Madonnas, and se our speculation concerning the chemical composition of the paint has not been confirmed.

(24) Pliny, Natural History, translated by D.E. Eichbolz, Cambridge, Mass. and London, 1971, book 37, lines 63-64, vol. X, p. 213. According to Pliny (book 37, line 64, vol. X, pp. 214-15), the Emperor Nero used an emerald 'to watch the fights between gladiators'. It is unclear whether the ancient writer means that Nero cast his eyes down on a gem to view the battle in reflection and relieve his eyes from the sun or--as this passage has traditionally been Interpreted--looked through emeralds, which functioned as eyeglasses or sunglasses. Elsewhere, Pliny (book 11, line 144, vol. III, p. 523), comments on the emperor's poor eyesight. The medieval writers Marbodus and Albertus Magnus claimed that emeralds not only aided sight, but also acted as amulets to preserve the chastity of the wearer and could help one scry into the future. See Marbodus, Poeme des pierres precieuses (Liber Lapidum: late 11th century), translated by Pierre Monat, Grenoble, 1996, pp. 25-28, and 31; and Albertus Magnus, Book of Minerals (Mineralia; c. 1260), translated by Dorothy Wyckoff, Oxford, 1967, pp. 119-20 and 148. Leonardo was familiar With the work of Theophrastus and possessed copies of the writings of Pliny, Albertus Magnus, and, possibly, Marbodus. See Codice Atlantico/Marinoni, fol. 318, vol. I, p. 546; MacCurdy, op. cit., vol. II, pp. 569-70, 572, and 574; end Jean Paul Richter (ed.), Carlo Pedretti, The Literary Works of Leonardo da Vinci, Berkeley and Los Angeles, 1977, vol. n, pp. 357, 360, and 363. There may be a physiological reason for the effect of the colour green and green wavelengths of light on the mood health of an individual. Clinical studies conducted during the past several years, though inconclusive, strongly suggest that light in the green portion of the spectrum suppresses the secretion of the hormone malatonin in patients and significantly decreases depression. See George C, Brainard, 'The Biological and Therapeutic affects of Light', in Kurt Nassau (ed.), Colour for Science, Art and Technology, Amsterdam. 1995, pp. 256 and 266-68. From antiquity through the renaissance, the designation 'emerald', a variety of beryl, was also applied to other, translucent green stones, such as malachite. Therefore, worthy of consideration is Castelli's suggestion that the gem is a greenish opal, although there is no indication in Leonardo's painted jewel of the brilliant, refractive 'fire' usually found in that stone. See Patrizia Castelli in Maria Grazia Ciardi Dupre Dal Poggetto (ed.). L'Oreficeria nella Firenze del Quattrocento, exh. cat., Florence, 1977, no. 232, pp. 349-50. Less plausible are Heydenraich's tentative identification of the stone of the Munich Madonna's brooch as an amethyst and Kustodieva's suggestion that the Benois Madonna wears a rock crystal. See Ludwig H. Heydenreich, 'La Madonna del Garofano' and Tatiana Kustodieva, 'Madonna Benois e Madonna Litta' in Pietro Marani (ed.), Leonardo: La pittura. Florence. 1985, pp. 34 and 50.

(25) Marsilio Ficino. The Book of Life (1489), translated by Charles Boer. Woodstock CT, 1980, book II, chapter 14, p. 62.

(26) The Nonesuch Complete Works of William Shakespeare: Poems, London and New York, 1953, lines 213-14, p. 212.

(27) Leonardo's brooches are modelled on those in the sculpture, paintings, and drawings of Verrocchio and his shop, such as the master's terracotta relief of the Madonna and Child (c. 1475) in the Bargello, the metalpoint Study of a Female Head (c. 1470-75); Musee du Louvre, Departement des Arts Graphiques), alternately attributed to Verrocchio or Perugino in his workshop, Lorenzo di Credi's Madonna di Piazza (c. 1478-85; Pistoia Cathedral), and his Madonna of the Pomegranite (c. 1475; National Gallery of Art, Washington) and the preparatory study for it (Kupferstichkabinett, Staatliche Kunstsammlungen, Dresden). See Andrew Butterfield, The Sculptures of Andrea eel Verrocchio, New Haven and London, 1997, figs. 109, 111, and 248, and David Alan Brown, Leonardo da Vinci: Origins of a Genius, New Haven and London, 1998, figs. 144, 150, and 152. Leonardo substituted the green gemstone for the rubies depicted in the Verrocchio school works.

(28) The second part of the Latin name for the carnation--Dianthus ceryophyllus--derives from the Greek word for 'nail', which was employed as a botanical term by Pliny in the Nature/History (XII, 30), vol. IV, pp. 22-23; he and others made this appellation because the buds of carnations (end of flowers of related species) resemble nails. The French name 'giroflee', comes from carophyllum, and the German word for carnation, 'nelke', is a form of the term 'Negele (Nagel)', or nail For the medieval-renaissance association of carnations with the nails of Christ's cross, see Ingvar Bergstrom, Den symboliska nejlikan. I senmedeltidens och renassansens konst, Malmo, 1958, pp. 27 and 72-73; Robert A. Koch, 'Flower Symbolism in the Portirrari Altar', Art Bulletin, vol. LVI, March 1964, p. 73; and Margaret B. Freeman, The Unicom Tapestries, New York, 1976, p. 148, According to an obscure legend, carnations grew from the tears shed by the Virgin on the road to Calvary. See Diana Apostolos-Cappadona, Dictionary of Christian Art. New York. 1994. p. 72. In some renaissance depictions of the Virgin and Child, a red carnation, appropriately of Middle-Eastern origin, may have been substituted for the rose--the traditional symbol of Mary--because the latter flower increasingly had become associated with Venus and profane themes.

(29) Although the painted plant is usually identified as jasmine, it could actually represent a wallflower (to which the structure end pattern of the leaves are more similar) or some other species of the cruciferous family. See Everett Fahy, The Legacy of Leonardo: Italian Renaissance Paintings from Leningrad, exh. cat., National Gallery of Art, Washington, and Los Angeles County Museum of Art, 1979, p. 13; and William A. Emboden, Leonardo da Vinci on Plants and Gardens, Portland OR, 1987, pp. 120-21. In fact, wallflowers are perhaps more commonly depicted than the relatively exotic jasmine in late medieval and renaissance art, as the Unicorn Tapestries (c. 1500) In The Cloisters, New York. See Freeman, op. cit., p. 127. Whatever the species of flower in the Benois Madonna, Leonardo has the petals to make the blossoms more cross-like. Leonardo's followers seem to have been aware of the master's concern for the babies" eyesight in the Munich end St Petersburg works. Having already made a drawing (Uffizi, no, 1197E) after the child in Leonardo's Munich picture, Lorenzo di Credi painted a Virgin and Child (c. 1485: Galleria Sabauda. Turin) in emulation of the Benois Madonna and its visually-challenged. Francesco Napoletano also executed a Madonna (c. 1478-83; Brera, Milan) based on the Hermitage picture, in which the child is presented as having difficulties with hand-eye coordination. See Gigetti Dalli Regoli, Lorenzo di Credi Pisa, 1966, no. 5, fig. 6, and no. 36, fig. 24; and Giullo Bora et al., The Legacy of Leonardo: Painters in Lombardy 1490-1530, Milan, 1998. pp. 201 and 204, fig. 79.

(30) The background scene depends on Leonardo's preliminary study with perspectival grid, executed in silverpoint and pen and ink, which is preserved In the Uffizi (436Er); for a reproduction, see Carlo Pedretti, I disegni di Leonardo da Vinci e della sua cerchia, Florence, 1985, no 8, pp. 56-68.

Larry J. Feinberg is Patrick G. and Shirley W. Ryan Curator in the Department of European Painting at the Art Institute of Chicago. His second article, which explores issues of art and perception in an investigation of Leonardo's visual puns, will be published in APOLLO next month.

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