Sunday, 30 August 2020

Disappointing Anatomy - History of the Brain III




Gijsbert Calkoen has gone down in history as a disappointed man. Immortalized by Rembrandt in 1656, the Dutch surgeon embodies the perplexity of the brain, and the frustrations felt by physicians through centuries.


But to understand his disappointment, we need first to explore an earlier painting by the same artist.

“Anatomy lesson of Doctor Nikolaes Tulp” is considered Rembrandt's breakthrough. At the age of 26, he was invited to depict a public dissection performed by the Amsterdam Guild of Surgeons. At this time, dissections of humans were considered a sin by the church. But a loophole was found by accepting the dissections of criminals - implying that criminals were inhuman. Annually, the public was invited to attend for a small fee, and on this occasion in 1632, the young and promising painter from Leiden was invited to preserve the moment. We know the name of every doctor in the picture, we know the name and the crime committed by the unfortunate corpse, and we guess that the book in the lower right corner is “De humani corporis fabrica” by Vesalius.
But all these details and facts are not what I like about this painting. What I like, is what most people like, and probably what the artist himself liked. What I like, is the fascination of anatomy. Look at how excited these doctors are about the tendons and muscles of the arm. As if they are looking upon the work of creation itself. And indeed, when examining the forearm you get a very palpable idea about how the human body works. You can pull a tendon and see the fingers move, and you can find the insertions of muscles onto the bone and make every joint work. For a 17th century doctor, this anatomy lesson would be a testimony of divinity.
We still admire the elegance of anatomy. Four hundred years later, this painting still fascinates as an example of how easily nature reveals itself. It is easy to marvel in the wonder of the human body while ignoring the inaccessible areas.
But the difficulties of anatomy and physiology were pointed out by Rembrandt just 24 years after the first painting. Now a mature artist, in “Anatomy lesson of Doctor Deijman” Rembrandt focuses on the most complex of organs; the brain.


Although partially destroyed by a fire in 1723, the painting is still beautiful, positioning the unfortunate criminel as a victim in an obvious tribute to Andrea Mategna’s painting “The Lamentation of Christ”. But instead of the mourning Mary, we find to the left the disappointed Gijsbert Calkoen. The Dutch surgeon has been given the appalling task of holding the skullcap of the executed criminal, but this doesn’t seem to bother him much. Instead he is distressed by the inaccessible anatomy of the brain. There’s nothing but a greyish yellow pulp of fat, some fluids and tiny blue vessels.
You almost feel sorry for him. Did he really think he could just open up the skull and see how the brain works, like he did with the arm? Maybe he thought there would be strings and gears and small light bulbs, that he could just pick it apart in some frankensteinian reversed engineering. Well, he was wrong. The brain does not reveal itself by inspection. It would be another two hundred years before we would even begin to peek at the underlying mechanics and functionality of the brain.

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Riegl A: The Group Portraiture of Holland. Getty Research Institute of the History of Art and the Humanities. 1999
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Sunday, 23 August 2020

Pulp Appendix - History of the Brain II




The human brain is a yellowish greyish pulp overspread with small capillaries. You can hold it in one hand like a ball. It is not as soft as you would imagine, and not as light as you might think. You can cut it open, studying the fine structures of white and grey foldings in recognizable patterns. You can fry it with vinegar and garlic, and it will taste like vinegar and garlic. 
What does it do? 
Aristotle thought the function of the brain was to cool the blood. It is easy to see how this conclusion could be reached in an ancient world struggling with the interpretations of physiology. The pounding of the heart as an emotional response would easily prompt the idea that the heart was the seat of the soul. Blood was supposedly warmed in the heart, flowing through blood vessels to heat other organs. With the abundance of vessels in the skull and capillaries spreading out like a delta floodplain around the brain, it must have been an obvious assumption that blood could be cooled in this gooey mass, like hot water flowing over cold rocks.
Other physicians interpreted the anatomy differently. Based on the anatomical observations that the optic nerves connect the eyes with the brain, Alcmaeon of Croton recognized the brain as the organ of perception. Alcmaeon was also the first to identify the eustachian tubes linking the inner ear to the nasal cavity. These observations of pores, tunnels, chambers and canals of the skull must have led him to the obvious assumption that the brain is the centre of the senses.
In Alexandria, Herophilos and Erasistratus mapped the nerves leading from the brain to the muscles and discovered the difference between sensory and motor nerves. Herophilus in an apparently arbitrary insight located the soul to the fourth ventricle of the brain.
No text by Alcmaion or by Erasistratus exists in its entirety, but they are quoted by another important physician, the roman Galen. His teachings on human physiology and humorism would influence Western thinking for centuries. While working as a physician to the gladiators at Pergamon, like the Egyptian battle surgeon milleniums before him, Galen recognized that a blow to the head would cause the gladiator to pass out. He concluded that the brain must be the seat of consciousness. Although an admirer of Aristotle, he opposed the idea of the brain as a cooling organ secondary to the emotions of the heart. And although schooled in the Aristotelian principle of recognizing only what could be experienced by the senses, Galen did publish a lot of unsubstantiated speculations. Fascinated by the rete mirabili, a complex of arteries and veins covering the brain at the basis of the skull, he wrote “[it] is not a simple network but (looks) as if you had taken several fishermen’s nets and superimposed them. [Y]ou could not compare this network to any man-made nets, nor has it been formed from any chance material. Nature appropriated the material for this wonderful network.” He excitedly concluded that vital spirits were produced in the heart, transported by the carotid arteries to the brain, and transformed to the highest spirits of man in the rete mirabili.
Galen could easily have been proven wrong though; had he dissected gladiators instead of sheep, he would have realized that the rete mirabili is found in only some mammals, but not in humans.
The Rete Mirabili. In sheep.


Other attempts were made. Leonardo da Vinci contributed to neuroanatomy with impressive drawings, beautiful and with an unmistakably Leonardian attention to detail. Using hot wax, he casted the ventricles of the brain, producing unprecedented anatomical insight. He’s idea that three ventricles held sensation, intellect and memory respectively, was however pure speculation and guesswork. 
For centuries the comprehension of the human mind was based on anatomy alone. It would require the combination of anatomy and clinical findings to localize cognitive functions and substantiate our knowledge of the brain.

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Finger S: Origins of Neuroscience: A History of Explorations Into Brain Function. Oxford University Press 1994
Porter R: The Greatest Benefit To Mankind - A Medical History of Humanity from Antiquity to the Present. HarperCollinsPublishers 1997
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Violent Beginnings - History of the Brain I

Violent Beginnings - History of the Brain I

Remember when you were a child playing with your parent's books? You would pull them out of the shelf, stacking them like bricks into towers or castles or raising them like walls. You probably knew that these books were important, but you lacked the skills to understand why. You probably understood that their texts held some kind of wisdom, but that it was out of reach. You may have realized that it was incomprehensible to you now, but that you might later could learn to understand the content of these bricks. 
That is the paradox of neuroscience. Trying to grasp the importance of what is right in front of you, knowing well enough that you cannot possibly hope to understand all of it. You simply lack the skills to see through the bricks and read the text.
Our understanding of the mind is limited by our own cognition itself. Our insight into psychology and neurology is too often limited by our lack of knowledge. Our understanding of the brain is halted by our own insufficient mental capacities.

This paradox of neuroscience is appropriately illustrated by the story of Edwin Smith. And by the unknown author of the papyrus that holds his name.
In 1862 in Luxor in Egypt, Edwin Smith purchased a papyrus from the antique dealer Mustapha Aga. Although an egyptologist, Smith's knowledge of the hieroglyphs on the papyrus was insufficient, and he was unable to read the text. Like so many other scientists, he could not penetrate or interpret the subject before him, simply because he lacked skills. Edwin Smiths was unable to realize the value of his purchase.
He kept the papyrus in his own possession until his death, at which point his daughter donated it to New York Historical Society where the task of translating the hieratics was given to James Henry Breasted. It was soon realized that the papyrus was a medical text describing the diagnostics and treatments of 48 traumatic injuries. Dated to 1600 BCE, it is speculated that the papyrus may have been a manual of military surgery. The text not only includes the first recorded mention of the brain, but holds also the first neurologic examinations and diagnostic findings.
In much the same way it is argued that war is the catalyst of civilizations, it must be admitted that the neurological sciences are based on deficits and injuries of the brain. The Edwin Smith Papyrus illustrates this discouragingly well; written as a military necessity, it is violence and traumatic injury that passes knowledge of the brain through more than three millennia to our present.

Case 6:
If thou examinest a man having a gaping wound in his head, penetrating to the bone, smashing his skull, (and) rending open the brain of his skull, thou shouldst palpate his wound. Shouldst thou find that smash which is in his skull [like] those corrugations which form in molten copper, (and) something therein throbbing (and) fluttering under thy fingers, like the weak place of an infant’s crown before it becomes whole [...] (and) he discharges blood from both his nostrils, (and) he suffers with stiffness in his neck, [thou shouldst say]: An ailment not to be treated.

In the commentary, Breasted cannot conceal his excitement of identifying the word:
 
as being “the earliest reference to the brain anywhere in human records.” The description is however rather disgusting, and the importance of this pulpish organ slips the author of the papyrus. Nevertheless, the text realizes that a trauma of this severity cannot be treated with any favorable outcome. It is an ailment "not to be treated," as so many battlefield surgeons have experienced since then. 
The papyrus holds plenty of interesting details. In cases concerning head trauma, neck stiffness is often mentioned as “he suffers with stiffness in his neck, so that he is unable to look at his two shoulders and his breast.” This could easily be interpreted as the well known observation that head traumas with subarachnoid haemorrhage will cause neck stiffness in the patient. This finding is still a key diagnostic in clinical neurology today.

It also describes epileptic seizures following head trauma as a patient “shudders exceedingly”, realizing that this is “an ailment which I will contend. [...] thou shouldst not bind him, (but) moor (him) at his mooring stakes until the period of his injury passes by.”

And in case 20, like the child playing with books, the battlefield surgeon authoring the papyrus was on the brink of a very important realization. Describing a head trauma penetrating the temporal bone, it is noted that “if thou ask of him concerning his malady [...] he speak not to thee.” The description of speechlessness is exclusively limited to the traumas at the temple, and the conclusion that the temporal part of the brain holds the capacity for speech, seems imminent. However, this concept of cortical localization was missed by the author.
The Edwin Smith Papyrus reflects our current knowledge that the centre for speech is located in the temporal lobe of the human brain. But the idea that certain areas of the brain controls specific mental functions, slips the author. The concept of cortical localization would not emerge until the late 19th century. At that point it would be exactly the temporal lobe and the localization of speech that fascinated anatomist Paul Broca.

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Breasted JH: The Edwin Smith Surgical Papyrus. Published in facsimile and hieroglyphic transliteration with translation and commentary in two volumes. The University of Chicago Press. 1930.
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