Optograms: images from the eyes of the dead

On a cloudy fall morning in 1880, Willy Kuhne, a distinguished professor of physiology at the University of Heidelberg, waited impatiently for 31-year-old Erhard Reif to die. Reif had been found guilty of the reprehensible act of drowning his own children in the Rhine, and condemned to die by guillotine. Kuhne’s eagerness for Reif’s death, however, had nothing to do with his desire to see justice served. Instead, his impatience was mostly selfish—he had been promised the dead man’s eyes, and he planned to use them to quell a bit of scientific curiosity that had been needling him for years.

For the several years prior, Kuhne had been obsessed with eyes, and especially with the mechanism underlying the eye’s ability to create an image of the outside world. As part of this obsession, Kuhne wanted to determine once and for all the veracity of a popular belief that the human eye stores away an image of the last scene it observed before death—and that this image could then be retrieved from the retina of the deceased. Kuhne had given these images a name: optograms. He had seen evidence of them in frogs and rabbits, but had yet to verify their existence in people.

Optograms had become something of an urban legend by the time Kuhne started experimenting with them. Like most urban legends, it’s difficult to determine where this one began, but one of the earliest accounts of it can be found in an anonymous article published in London in 1857. The article claimed that an oculist in Chicago had successfully retrieved an image from the eye of a murdered man. According to the story, although the image had deteriorated in the process of separating the eye from the brain, one could still make out in it the figure of a man wearing a light coat. The reader was left to wonder whether or not the man depicted was, in fact, the murderer—and whether further refinements to the procedure could lead to a foolproof method of identifying killers by examining the eyes of their victims.

Optograms remained an intrigue in the latter half of the 19th century, but they became especially interesting to Kuhne when physiologist Franz Boll discovered a biochemical mechanism that made them plausible. Boll identified a pigmented molecule (later named rhodopsin by Kuhne) in the rod cells of the retina that was transformed from a reddish-purple color to pale and colorless upon exposure to light. At the time, much of the biology underlying visual perception was still a mystery, but we now know that the absorption of light by rhodopsin is the first step in the visual process in rod cells. It also results in something known as “bleaching,” where a change in the configuration of rhodopsin causes it to stop absorbing light until more of the original rhodopsin molecule can be produced.

In studying this effect, Boll found that the bleaching of rhodopsin could produce crude images of the environment on the retina itself. He demonstrated as much with a frog. He put the animal into a dark room, cracked the windows’ shutters just enough to allow a sliver of light in, and let the frog’s eyes focus on this thin stream of light for about ten minutes. Afterwards, Boll found an analogous streak of bleached rhodopsin running along the frog’s retina.

An optogram Kuhne retrieved from the retina of a rabbit, showing light entering the room through a seven-paned window.

Kuhne was intrigued by Boll’s research, and soon after reading about it he started his own studies on the retina. He too was able to observe optograms in the eyes of frogs, and he saw an even more detailed optogram in the eye of a rabbit. It preserved an image of light coming into the room from a seven-paned window (see picture to the right).

Kuhne worked diligently to refine his technique for obtaining optograms, but eventually decided that—despite the folklore—the procedure didn’t have any forensic potential (or even much practical use) at all. He found that the preservation of an optogram required intensive work and a great deal of luck. First, the eye had to be fixated on something and prevented from looking away from it (even after death), or else the original image would rapidly be intermingled with others and become indecipherable. Then, after death the eye had to be quickly removed from the skull and the retina chemically treated with hardening and fixing agents. This all had to be done in a race against the clock, for if the rhodopsin was able to regenerate (which could even happen soon after death) then the image would be erased and the whole effort for naught. Even if everything went exactly as planned and an optogram was successfully retrieved, it’s unclear if the level of detail within it could be enhanced enough to make the resultant image anything more than a coarse outline—and only a very rough approximation of the outside world.

Regardless, Kuhne couldn’t overlook the opportunity to examine Reif’s eyes. After all, he never did have the opportunity to see if optograms might persist in a human eye after death and—who knew—perhaps optograms in the human eye would be qualitatively different from those made in the eyes of frogs and rabbits. Maybe human optograms would be more accessible and finely detailed than he expected. Perhaps they might even be scientifically valuable.

Reif was beheaded in the town of Bruschal, a few towns over from Kuhne’s laboratory. After Reif’s death, Kuhne quickly took the decapitated head into a dimly-lit room and extracted the left eye. He prepared it using the process he had refined himself, and within 10 minutes he was looking at what he had set out to see: a human optogram.

Kuhne’s drawing of The image he saw when he examined Erhard Reif’s retina.

So was this the revolutionary discovery that would change ophthalmic and forensic science forever? Clearly not, or murder investigations would look much different today. Kuhne made a simple sketch of what he saw on Reif’s retina (reprinted to the right in the middle of the text from one of Kuhne’s papers). As you can see, it’s a bit underwhelming—certainly not the type of image that would solve any murder mysteries. It confirmed that the level of detail in a human optogram didn’t really make it worth the trouble of retrieval. Kuhne didn’t provide any explanation as to what the image might be. Of course any attempt to characterize it would amount to pure speculation, and perhaps the esteemed Heidelberg physiologist was not comfortable adding this sort of conjecture to a scientific paper.

This experience was enough to deter Kuhne from continuing to pursue the recovery of human optograms, and it seems like it would be a logical end to the fascination with optograms in general. The idea of using them to solve murders, however, reappeared periodically well into the 1900s. In the 1920s, for instance, an editorial in the New York Times critiqued a medical examiner who had neglected to take photographs of a high-profile murder victim’s eyes, suggesting that an important opportunity to retrieve an image of the murderer had been lost.

But as the 20th century wore on and our understanding of the biochemistry of visual perception became clearer, interest in optograms finally dwindled. Those who studied the eye were not convinced of their utility, and that opinion eventually persuaded the public of the same. It’s intriguing to think, though, how different our world would have been if optograms really had lived up to the hype. It certainly would have simplified some episodes of CSI.

Lanska DJ. Optograms and criminology: science, news reporting, and fanciful novels. Prog Brain Res. 2013;205:55-84. doi: 10.1016/B978-0-444-63273-9.00004-6.

History of neuroscience: Julien Jean Cesar Legallois

The idea that different parts of the nervous system are specialized for specific functions has been a pervasive concept in brain science since ancient times, perhaps best exemplified by the belief---dating back to the 4th century CE---that the four cavities of the brain known as the ventricles each were responsible for a different function, e.g. perception in the two lateral ventricles, cognition in the third ventricle, and memory in the fourth ventricle. By the early 1800s, however, there was still no definitive experimental evidence linking a particular function to a circumscribed area of the brain.

Image showing the medulla oblongata, the region of the brainstem that Legallois found was essential to respiration.

Image showing the medulla oblongata, the region of the brainstem that Legallois found was essential to respiration.

This changed with Julien Jean Cesar Legallois, a young French physician who was driven to identify the parts of the brain and body that were essential for maintaining life. The thinking at the time was that the heart and brain were both integral to life, but there was some debate about where the life-sustaining centers in the brain were located. Some, for example, considered the cerebellum to be the organ that controlled vital functions like heartbeat and respiration. Research conducted in the second half of the 18th century by the French physician Antione Charles de Lorry, however, had suggested that the area of the brain most critical to life was found in the upper spinal cord. Legallois would take Lorry's research a step further by conducting a series of gruesome experiments with rabbits that would help him to specifically pinpoint the center of vital functions in the brain.

Before detailing these experiments, it's important to mention that Legallois' studies were done at a time when the ethical treatment of animals in research---and indeed ethics in research at all---were not given much thought. Legallois was a vivisectionist, meaning that he performed surgery on living animals in his experiments. Legallois' work would not be likely to be approved by a university or research institution today, and indeed when you read Legallois' own impassive descriptions of his grisly experiments they sound like something a budding serial killer might have dreamed up before he moved on to human victims. But this was a different time, when thoughts about animal welfare were not as well formulated as they are now---and Legallois was far from the only vivisectionist of his day. Indeed, a great deal of our current neuroscience knowledge was developed using experimental methods we would consider unjustifiably cruel today. 

Legallois' method of exploring the centers of vital functions in the brain primarily involved the decapitation of rabbits. Legallois observed that after a decapitation made at certain levels of the brainstem, the headless body of a rabbit could still continue to breathe and "survive" for some time (up to five and a half hours according to Legallois). Decapitation further down the brainstem, however, would cause respiration to cease immediately. This observation was in agreement with Lorry's. Legallois then set out to isolate the particular part of the brainstem where these respiratory functions were located.

To do this, Legallois opened the skull of a young rabbit (while the rabbit was still alive), and began to remove portions of the brain---slice by slice. He found that he could remove all of the cerebrum and cerebellum and much of the brainstem, and respiration would continue. But, when he reached a particular location in the medulla oblongata---at the point of origin for the vagus nerve---respiration stopped. Thus, Legallois surmised that respiration did not depend on the whole brain but on one circumscribed area of the medulla. He concluded that the "primary seat of life" was in the medulla, not the cerebellum or cerebrum.

Legallois published the details of his seminal experiment in 1812. We now consider the medulla to be a critical area for the control of respiration as well as the regulation of heart rate, and the region is often considered to be a center of vital functions in the nervous system. Indeed, Legallois was influential in establishing the hypothesis that the brain is involved in the regulation of heart rate as well (prior hypotheses had emphasized the ability of the heart to act alone---without the influence of the brain). While Legallois was not the first to hypothesize that vital functions are localized to the medulla (he was preceded by Lorry), he was the first to provide clear experimental evidence linking the medulla to such functions, and he greatly refined Lorry's estimation of where the vital centers were located. In the process, Legallois gave us our first clear evidence that linked a function to a localized area of the brain.

Cheung T. 2013. Limits of Life and Death: Legallois's Decapitation Experiments. Journal of the History of Biology. 46: 283-313.

Finger, S. 1994. Origins of Neuroscience. New York, NY: Oxford University Press.

For more about the medulla oblongata's role in vital functions, read this article: Know your brain - Medulla oblongata

History of neuroscience: Charles Scott Sherrington


To many, Charles Scott Sherrington is best known for providing us with the term synapse, a word we still use to describe the junction where two neurons communicate. While Sherrington's work to understand synapses and neural communication was important, however, his studies of reflexes, proprioception, spinal nerves, muscle action, and movement were much more expansive and probably even more influential.

Regardless, his observations concerning synapses are representative of the meticulous care with which he investigated and made deductions about the nervous system and its function. His writings on the synapse came at a time when Santiago Ramon y Cajal was beginning to convince the scientific community that the brain consists of separate nerve cells (which became known as neurons in 1891) rather than a continuous "net" of uninterrupted nerves. One thing missing from this theory was an understanding of how neurons might communicate with one another.

In writing on that issue, Sherrington proposed a specialized membrane---which he termed a synapse---that separates two nerve cells that come together. Microscopes of the day couldn't actually observe the separation found at synapses (which is minutely small), so Sherrington was forced to describe the synapse as a purely functional separation---but a separation nonetheless. He based his hypothesis on observations he made in his own research like the fact that reflexes (which he studied extensively) weren't as fast as they should be if they involved simply conducting signals along continuous nerve fibers. Sherrington had originally planned to use the term syndesm to describe the functional junction between neurons, but a friend suggested synapse, from the Greek meaning "to clasp," since it "yields a better adjectival form." 

Thus the term synapse was born, but for Sherrington his observations about the synapse were really just one part of a much greater investigation into reflexes and nerve-muscle communication. He made an important contribution in this area when he helped to elucidate the mechanism underlying the famous knee-jerk reflex (which you've likely experienced when a doctor has tapped just below your kneecap to cause your leg to kick outwards).

His work on spinal reflexes also led Sherrington to another seminal hypothesis. He proposed that muscles don't just receive innervation from nerves that travel to them from the spinal cord but that they also send sensory information about muscle length, tension, and position back to the spinal cord. Sherrington believed that this information is important for things like muscle tone and posture. He hypothesized that there are receptors in the muscle that convey this type of information, and he specifically identified muscle spindles and golgi tendon organs as potential receptors that send information about stretch and tension, respectively (this would later be confirmed). To describe the information these muscle receptors send, Sherrington coined another termproprioception. He chose this term because proprius is Latin for "own" and he wanted to emphasize that the sensory information sent from these muscle receptors comes from an individual's own body, and is not initiated by an external stimulus (as is common with other receptors).

Among Sherrington's many other contributions to understanding movement and muscle function, he also helped to develop a better understanding of the mechanism underlying something called reciprocal innervation. Reciprocal innervation refers to the way in which the activation of one muscle influences the activity of other muscles. This is a common and necessary response. As we walk across the floor, for example, when the muscles involved in the extension of one leg are activated, the muscles involved in the retraction of that same leg must be inhibited. Otherwise, our muscles would constantly be competing with one another, which would result in complete rigidity and make movement (or even standing in one place) impossible. Sherrington didn't discover the phenomenon of reciprocal innervation, but he spent years studying it and in the process gave us a better understanding of how it works. His investigations of reciprocal innervation led to a number of experiments on complex reflexes involved in movements like walking, running, and even scratching. His work helped us to understand how some reflexes involve chaining together several simple reflexive actions to create a seemingly complicated behavioral display.

Sherrington's focus on spinal nerves and reflexes led him to map the motor nerves traveling from the spinal cord to the muscles and the sensory nerves traveling from the muscles to the spinal cord---a task which took him almost ten years. He also explored the functionality of these nerves, helping to create a map of the area of the body served by a single spinal nerve (areas known as dermatomes). And he mapped the ape motor cortex, expanding on previous maps that had been made with dogs and monkeys.

Thus, although Sherrington may be best known for his naming of the synapse, his other work---which was broad but focused a great deal on muscles, movement, and reflexes---was probably even more valuable to our overall understanding of the nervous system. Sherrington won the Nobel Prize for Medicine in 1932 just as he was entering into his retirement, as recognition for his wide-ranging contributions to neuroscience. He continued to write into retirement, and branched out from scientific writing to publish a collection of poems as well as a book that focused on philosophical themes like the relationship between the mind, brain, and soul. He died in 1952 at the age of ninety-five.

Finger S. Minds Behind the Brain. New York, NY: Oxford University Press; 2000