This blog of mine first appeared in The Embalmer’s Book of Recipes. Recently I have been to the Surgeons’ Hall Museum in Edinburgh as I wanted to find out more about several of the anatomical specimens held in the Collection (I will write more about this in due course) — and I was impressed by the collection of eyes, and information about diseases of the eye, donated in the 1880s by William Walker, who as well as being the first specialist opthalmologist at the Edinburgh Royal Infirmary also had the grand title of Surgeon Oculist to Queen Victoria.
I have also written to Lisa (see the section ‘About’ me) to tell her about James Jack (known as ‘Jimmy’ — but then, of course, he wasn’t a surgeon; he was merely the man in charge of the Museum’s Collection during the Second World War.) Why might Lisa be interested? James was an achondroplasic; in his photo he is looking very dapper in a suit with a flower at the lapel, a flat cap – and a giant-sized cigar.
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An ivory and glass artificial eye, photographed in St Petersburg by Rosamond Wolff Purcell and reproduced on the cover of The Embalmer's Book of Recipes
‘Making Eyes’
White spheres lie on cotton-wool in the compartments of a flat wooden box: blue, brown or green circles, dark centres – pot-boilers, money-spinners: artificial human eyes. On a workbench there are small bottles, pinboxes and wooden trays containing different body-parts: glass tentacles of different shapes and colours, sponge spicules, tiny shells. ‘Mix ’n match’ invertebrates amongst the powdered glass and pigments.
In 1860, Philip Henry Gosse’s Actinologia Britannica was published, illustrated with engravings of coloured sea-anemones and corals. A few years later, an Englishman living in Dresden showed these pictures to glass-maker Leopold Blaschka. ‘Marine creatures preserved in spirits look like grey rubber,’ he said. ‘Why not show their true colours by modelling them in glass?’ Leopold accepted the challenge: he had already modelled orchids, and now he merged his art with science, modelling the exquisite and minute details of invertebrate animals, making them objects for the museum and scientific study rather than ornaments for the drawing-room.
Glass eyes made by the Blaschkas
Later, he and his son Rudolf were to give up animals and Haeckelian embryos for a ten-year commission to make the Harvard glass flowers; but in the earliest days their business was not yet profitable, so they created jewellery, and glass eyes for cosmetic use by the blind.
We don’t know where Frederik Ruysch obtained the glass eyes to fill the orbits of his embalmed and Death-defying Dutch babies in the 17th century, but they obviously did the trick for the babies’ winning looks won the heart of great Czar Peter. The philosopher Jeremy Bentham, who died in 1832, probably had the foresight to choose his own glass eyes, but he clearly had not planned that his mummified head would be stored inside his torso.
Can we defy Death, and preserve and repair our ageing body-parts, can the blind really be made to see again? Human eyes are such complicated balls of cells. William Paley had argued in his Natural Theology in 1802, that the eye, like a telescope, could only have been designed by a Maker. (But the Maker must have been having a visual migraine when he designed the mammalian retina, back-to-front.) Charles Darwin struggled to understand how these ‘organs of extreme perfection’ could have arisen from chance mutations alone. ‘To suppose that the eye … could have been formed by natural selection seems, I freely confess, absurd in the highest degree,’ he wrote. It’s almost enough to turn one into a Creationist or propose the intelligent mind and hand of a Designer. There is the implication that Evolution had foresight and saw its future goal. We know now that Evolution is a conservationist and throws very little away: ‘You want an image-forming retina? There’s a bit of photosensitive pigment kicking around somewhere. A bit of this and a little bit of that, let’s try them in this order instead …’ The ingredients are mixed in a different sequence, to a different recipe.
The ingredient pax6 has never been allowed to rest, we need that gene as much as a flatworm does. In the embryo of a fly the product of pax6 directs the development of the eye. Gosse examined an insect’s eye under his microscope in the 1850s: ‘How gorgeously beautiful are these two great hemispheres that almost compose the (dragonfly’s) head, each shining with a soft satiny lustre of azure hue,’ he wrote. ‘You see an infinite number of hexagons, of the most accurate symmetry and regularity of arrangement.’ Each of those ‘hexagons’ contains a lens, and a careful anatomist with a steady hand can prepare an insect’s eye so as to look through it himself. Van Leeuwenhoek (who lived a mere 50 years from 1675-1725, but achieved so much), looked through his microscope fitted with the prepared eye of a honey bee at a church steeple (‘which was 299 feet high, and 750 feet distant’) and saw multiple inverted images of the steeple. That microscope is in the Boerhaave Museum in Leiden, displayed near a shockingly pink toe injected and embalmed by Albinus (its severed end hidden by a lacy ‘cap’). It scarcely seems possible that Van Leeuwenhoek could have seen and understood so much of the natural world through a handheld instrument that is barely two inches tall.
The surface of the fruitfly Drosophila’s eye resembles a small raspberry. If the pax6 gene is injected into the embryonic cells that should form a Drosophila leg or an antenna, an eye grows there instead. Even more exciting and astonishing is that the raspberry will also grow if the pax6 equivalent from a mouse is injected into the fly embryo!
The large compound eye of Drosophila, with a small extra (ectopic) eye where the antenna should be. From Halder, Callaerts and Gehring 1995, Science, 267, p1788, and the Gehring pages on the Biozentrum, Switzerland website
A mouse’s eye is like ours, as different from a fly’s eye as is a fly’s wing from a bat’s. And so it is with pax6 from the jet-propelled and predatory squid, an animal that is related to creeping slugs and snails but which has an eye that is superficially like a mammal’s (this time, God designed the retina the right way round!). The Blaschkas’ glass model of a squid is translucent, delicate, with lustrous dark eyes; their red octopus peers at you from above its webbed tentacles.
The eye of a glass squid made by the Blaschkas
The gene is in the living animals, conserved, and put to different uses. Biologists have identified it and its related ingredients, they even know something of the recipe from which a human eye is made, but they cannot reproduce it in a culture-dish; they cannot make eyes. Yet.
Biologists can ‘make’ different sorts of cells. Take a fertilised mouse or human egg and nurture it in a culture dish for several days so that its cells divide and divide again, to form a hollow blastocyst. Imagine a football with a porkpie suspended inside it, and shrink it down in your imagination to the size of a pinhead: that is a 6-day blastocyst and the porkpie is a ball of embryonic stem cells. Stem cells, that each have the complete book of recipes to form any other type of cell in the growing embryo; ‘the secret of eternal life’, a cellular equivalent of a perpetual motion machine, the magic ingredient that will allow us to repair ourselves for ever. Not quite, but they do have their uses. Van Leeuwenhoek looked through his tiny microscope and watched red blood cells circulating in the vessels in a tadpole’s tail: he would have been astonished to know that undifferentiated stem cells taken from a blastocyst could be persuaded to turn into red blood cells in a culture dish; or into nerve cells, or muscle cells. (He would have been even more unbelieving to see how frogs’ eggs could be manipulated to produce clones).
Scientists can persuade corneal stem cells to grow new pieces of cornea; they can even persuade embryonic stem cells to change into one of the sorts of cell found in the retina at the back of the eye. But they cannot yet grow an eye, and if they could, how would they rewire it to the brain? All those millions of wires bound together in a cable, each needing their own connections in the brain. The Designer made an unintelligent muddle with those wiring diagrams, too, crossing over the cable from the right eye’s socket to the left brain, and vice versa.
William Hunter, FRS (1716-1783), anatomist, and man-midwife to Queen Charlotte and the gentry, dissected many corpses throughout his studies and demonstrations of anatomy. As President of the Royal Academy, he also liked to stress the links between science and art, and commissioned paintings and drawings of the three-dimensional structures that he dissected, as aids to surgery and deconstruction. Many of the contents of his London collection were transferred to Glasgow after his death. Upstairs in Glasgow’s Hunterian Museum, on a wooden shelf, are multiple rows of jars containing eyes. Intact, they stare at you while you stare at them and, because they are disassociated from their faces, you cannot tell whether they stare in hatred or fear or even, perhaps, amusement. Why did Hunter collect so many? Were they specimens for an unfinished study of the anatomy and development of the eye?
In the Museum Vrolik, Amsterdam, the Curator’s ‘favourite’ specimen was at one time a little foetus with a fuzz of pale red hair, his arms hanging gently in the preserving liquid as though he is merely resting. He is a little ‘cyclops’, whose genetic recipe made for him only one small central eye. He did not live to see the light of day, nor have the good fortune to enter the Country of the Blind.
(Part of this essay also appeared in The Lancet, in October 2010, under the title ‘It’s the eyes that are important’, by Ann Lingard)
