If you were to stretch flat all the membranes of an adult [human]'s lungs they would occupy over a thousand square feet [or 93 square metres]; equivalent to the leaf coverage of a fifteen to twenty-year-old oak.from Adventures in Human Being by Gavin Francis (2015)
It's an unsettling experience, projecting an image of someone's inner eye so neatly into your own, retina examining retina through the intermediary of a lens. It can be disorientating too: gazing down the axis of the beam is like looking up into the night sky with an eyeglass. If the central retinal vein is blocked, the resultant scarlet haemorrhages are described in the textbooks as 'stormy sunset appearance.' I sometimes see pale retinal spots caused by diabetes, and they're reminiscent of cumulus clouds. In patients with high blood pressure the branching, silvered shine on the retinal arteries resembles jagged forks of lightning. The first time I looked into the curved vault of a patient's eyeball I was reminded of those medieval diagrams that showed the heavens as an upturned bowl.from Adventures in Human Being by Gavin Francis (2015)
it was believed that magnets had souls, that swallowing them would give you eloquence, and that their property of “action at a distance” was related to the attraction of love. Now we know that eloquence and love, as they are expressed in the brain, do create magnetic fields: each neuron, as it fires, generates a minuscule magnetic field around the axis of its impulse. Imagine these fields as the ripples on a pond after throwing a stone, then imagine the undulating surface sheen of the water stripped off and wrapped around your head. Haloes of magnetic fields ripple from our brains as we talk, think, experience the world.An introductory note on Magnetoencephalography (MEG) from the York NeuroImaging Centre puts the magnetic fields generated by the brain in context:
The magnitude of magnetic fields outside the head generated by the electrical activity of the brain is of the order of femtotesla (10-15T)...tiny in comparison to the magnetic fields that we are exposed to in everyday life which are of the order of tens of microtesla (10-6). Our hearts generate a field in the order of tens of nanotesla (10-9) and a car moving will generate a magnetic field that is still of the order of femtotesla when the field is recorded one mile away from the car.
Magnetoencephalography scanners pinpoint [the] almost impossibly small magnetic fields [inside our brains] with amazing accuracy. They have shown us that only fifteen milliseconds after hearing a sound an impulse has reached the brainstem, and only a few milliseconds later it’s in the cortex. But the computation involved in understanding sounds is much slower: it takes sixty to one hundred milliseconds before large assemblies in the auditory cortex are activated, essentially “looking up” each sound. If the sound is familiar this process is quicker and generates less of a ripple, because the brain does less work to comprehend it. At around two hundred milliseconds conscious awareness begins, but isn’t lexically understood until after more like three or four hundred milliseconds. When we consider languages worldwide, we find that syllables last between 150 and 200 milliseconds—a constant that appears related to the physiology of the brain. It takes us almost six hundred milliseconds—over half a second—to recognize unexpected words, discordant tones in music, or make the looping connections necessary to make sense of discourse.— from a review by Gavin Francis of I Can Hear You Whisper by Lydia Denworth.
It is the episodic squeezing of our heart, the pressure difference between systole and diastole, that give rise to the pulses we feel in our wrists, our temples and our throats. The pulse is the defining characteristic of life. Every so often someone comes up with a design for an artificial heart that pumps without need of a pulse. How would it feel, I wonder, to have blood that moved continuously through the body; not the ebb and flood of a tide, but a ceaseless, circular flow?From Diary by Gavin Francis, London Review of Books, 6 March 2014
