Bicycles, Wound Healing and Munch’s Optical Illusions

I had my PhD viva two weeks ago now. I’m pleased to say it went very well – I passed! An unexpected consequence is that every time I say something a bit geeky my friends patronizingly say “Yes, Doctor,” and whenever anyone is trying to win an argument they ask, “What does the Doctor think?” I’m sure it’ll pass. A good consequence is that I have bought myself some new shoes to celebrate, and other people buy me things – I have two large bunches of flowers in my living room, and have actually run out of vases. My husband bought me a bicycle.

I hadn’t ridden a bicycle since I passed my driving test, almost 15 yrs ago, but nevertheless we chose the first outing to be a 16 mile bike-ride from Bristol to Bath with lots of friends. It was a beautiful day: we had lunch in the Jolly Sailor at Saltford Lock, and later went for a swim in the River Avon. To cut a long story short, we got to Bath, there was lots of beer in several pubs, it started raining and I fell off of my new bike.

As always, my injuries looked worse than they actually were. My entire lower leg was covered in blood, but once this was cleaned up it was established that I had only a graze on my ankle and a cut on my knee (pictured above). It’s funny that whenever I hurt my knees I have a strong sense of being a child – like injuring my knees is deeply related to childhood memories. Another funny thing about this injury is its location – in the photograph above you can see two white scars on my knee, a large one above and a smaller one below the new injury. Can you guess how I got these? That’s right, I fell off of my bike.

I was about the age of 10, cycling back from my friend’s house – it wasn’t far. I stopped in front of the park, probably to shout at my brother, and somehow got my leg caught on the crossbar. I fell down, knee first, bike on top of me. One of those really stupid things you do and have no idea how you do them. What was worse, however, was that at the exact place my knee hit the ground there was a pile of clear, broken glass.

I limped home, probably crying. My parents took me to the hospital. I remember that the doctor X-rayed my leg. I think he took some of the glass out with tweezers, but I have a distinct memory that some was too deep and so was left in. I often think about this and wonder whether one day it’ll work its way to the surface of my skin. I wonder whether it would able to still be seen, if I had my knee X-rayed now. Surely glass would not decompose in my leg.

Alternatively, I wonder how real the memory is. Perhaps there was never any glass left behind in my knee, but instead this is all a fantasy, made up by my childhood mind.

Although having a knee injury triggers a regression to my childhood, as an adult my recovery from such an injury couldn’t be more different. The best part about having a big wound on your knee as a child was picking bits of the scab off – undoubtedly why the scars are still so prominent today. Now, it’s knowing about how our bodies work, and how, within seconds of injury, particular processes under the skin become activated to minimise blood loss, prevent infection and begin the healing process. As a teenager, I remember this was the first molecular process that caught the imagination of my friends and I whilst studying GCSE Biology.

When a blood vessel is damaged, the immediate response of the smooth muscle cells is to constrict, to limit blood loss. Within seconds, platelets build up at the site of injury, become sticky and adhere to one another and the vessel wall. Next, fibrin strands create a mesh, a big net that binds blood components together to form a blood clot. Two enzyme cascades are activated, one when blood comes into contact with the injured vessel wall, the other when blood is exposed to the products of damaged tissue. The two pathways converge and are responsible for the cleavage of prothrombin to thrombin, which initiates the polymerisation of fibrinogen to fibrin strands, trapping plasma and blood cells to form a clot, and binding the edges of the damaged vessel together.

When the bleeding has finally stopped, and the blood coagulated, the clot slowly begins to shrink over a period of several days. This is when serum (clear or yellow in appearance) is extruded from the clot, and is what is happening in the photograph above.

When I was deciding whether to post a picture of my wounded knee here, I was reminded of an earlier post I had considered writing. Last month I went to see Edvard Munch: The Modern Eye at the Tate Modern in London. Munch is one of my favourite painters. His paintings and drawings are always so powerful to see in ‘real-life’. The aspect of Munch’s painting that caught my attention on this occasion was his use of optical illusion: in his paintings from the 1910s he exaggerated perspective to heighten the sense of distance, used unusual viewing angles, and truncated figures or pushed them to the edge of the composition.

In 1930, Munch suffered a haemorrhage in his right eye. He documented recovery from the injury through a series of drawings entitled ‘The artist’s injured eye’. He may have been exposing his eye to bright lights or direct sunlight to promote the formation of interesting shapes of light on his retina. ‘The artist’s injured eye: six optical illusions’ shows six circular shapes that appear more like small tissue masses than any of the other drawings. Some look like the flesh inside an oyster or mussel shell, coloured blue and red. Later drawings show landscapes or interiors dominated by a dark circular mass: the pooled blood obscuring his vision. In two drawings, Munch describes the injury as looking like a bird, and charts the changing distance between the bird’s beak and a new beak that has appeared. As much as these drawings document what can be seen past the injury, and what the blood mass does to the passage of light, they also tell us about the shape of the haemorrhage itself.

It is interesting how images of injured body parts are so unsettling to us. Perhaps none more so than an injured eye.

Subconjunctival haemorrhage. Someone else’s eye.

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