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Let us start today’s episode by getting to know our master of microscopes
James a little more…up close and personal.
Your screen is currently awash in James’ blood.
Fortunately, this was a planned affair. James didn’t accidentally cut himself on a slide and bleed all over it.
He simply placed a drop on the slide, and let the cells do the rest.
And so in observing his blood under the microscope, James is joining a
long tradition of scientists who have examined blood belonging to themselves, to other animals,
and to other organisms, so that we can decipher the role this fluid plays in keeping us alive.
It’s been hard for us as humans to miss the fact that blood is
important to our bodies. But understanding the nature and mechanisms of it has required
untangling the macroscopic structures that send blood coursing through our veins,
and the microscopic details that make blood what it is.
One of our early methods of describing and categorizing the body were the four humors,
a system developed by ancient Greek physicians who believed our body
could be described as the interplay between yellow bile, black bile, phlegm, and blood.
But blood is more than just the substance itself. The fluid is nothing without a way to use it.
And so our understanding of blood is tied up in our understanding of the whole system,
the circulatory system. To get to what that means,
let’s start by looking at the blood of something a bit different from us: daphnia.
One thing that makes daphnia handy for our purposes is that you can, you know, literally see
right through them. And with a microscope, you can observe the rapid beating of its heart and
the flow of blood cells through its body. Daphnia are also an invertebrate, and like
many other invertebrates, it passes cells and ions and other important molecules throughout its body
using a watery fluid called hemolymph. Their hemolymph isn’t constrained to veins or arteries.
Instead, it’s pumped into an open cavity called the hemocoel,
where it then comes into contact with the organs it needs to deliver nutrients to.
This is an open circulatory system. Vertebrates like us, on the other hand, use a closed
circulatory system where blood is directed throughout our body in a contained network
of blood vessels. That system allows for more efficiency in delivering oxygen throughout our
body, but it’s also more complex and requires more energy compared to the open circulatory system.
Now, it took us quite a while to piece together what our circulatory system would look like. The
second century physician Galen theorized that blood is made in our livers using the remnants
of digested food. And when blood arrived at whatever spot it was needed, it was then consumed.
Galen’s hypothesized path mistook the nature of blood and the structure of the heart,
and yet it was a theory that would prevail in medicine for centuries.
In the 13th century, the Arab physician Ibn-al-Nafis
drew on his study of animals to correctly describe how our circulatory system works.
And yet his revolutionary work was not widely known until 1924, when an Egyptian physician
found a copy of it in the Berlin State Library while working on his dissertation.
In the 17th century, English physician William Harvey came to draw the same picture of the
circulatory system, turning to demonstrations on dissected animals to gruesomely illustrate
his point. And his work would, in turn, go on to change our understanding of blood,
emphasizing that it is a thing made and circulated by our bodies, and not--as
Galen predicted--a product of our digestion. So what are some of the pieces that make up our
blood? It’s complex and variable, of course, but let’s focus on the color. For many invertebrates,
the hemolymph is either clear or tinted yellow with pigment molecules. And you
might be thinking right now, “ I’ve squashed a fly before! And there was a lot red!”
And yes, perhaps there was red. But that was actually due to the pigments
in the insect’s eyes, not the blood. But biology does love an exception,
which takes us back to the Daphnia, as well as to another invertebrate called Artemia.
Both of these invertebrate’s blood contains a protein that is familiar to us: hemoglobin.
Hemoglobin is the four-part protein inside our red blood cells that makes them red. And more
importantly, hemoglobin attaches to oxygen. When a red blood cell gets to our lungs, the hemoglobin
binds to oxygen, turning the red blood cell into our own personal oxygen transport machine.
Now there are other oxygen-binding molecules used by other animals, but Daphnia and Artemia both
turn to hemoglobin when times get tough. When the waters around them get low in oxygen, they
adapt by producing more and more hemoglobin so they can capture more of that precious resource.
As they produce more hemoglobin, the populations of Daphnia and Artemia become
visibly redder—like they’re blushing—which might explain why they don’t just have hemoglobin lying
around in large quantities all the time. Not only does it take energy to make hemoglobin,
it makes the animals more visible to predators. When you look at James’ blood cells, you can see
the red of the hemoglobin. But as we said at the start of this episode, James is one
of a long line of scientists who have examined their blood under the microscope. Some of the
early microscopic studies of human blood relied on samples taken from clots or a recently fed louse.
James has actually made a note on the script here. It says, “Glad I didn’t have to do this.”
But of course one of the early adopters of the self-study approach was none other
than the early master of microscopes, Antoni Van Leeuwenhoek, who described
the “sanguineous globules” of his own blood in a letter to the Royal Society of London.
Centuries later, Dr. Karl Landsteiner would collect samples from six of his co-workers
and himself to study how these different blood samples and the antibodies within them reacted
to each other. These observations would lead him to describe the human ABO blood grouping system.
We have always known that our blood was vital, in both senses of that word. And though we have
now teased apart much of its true nature, it’s significance reaches beyond scientific
understanding. We talk of blood relations, and of being hot blooded or red blooded. Blood
is always available to us, both for science and symbolism, for medicine and metaphor.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
We’d like to also say thanks again to Skillshare for supporting this video.
You can learn many many things on Skillshare, even
how to make your own blood! Well, digital blood at least.
With classes like “Animating Blood Flow in a Vessel with Cinema4D”, you’ll learn,
unsurprisingly, how to animate blood flow in a vessel in Cinema4D, but you’ll also learn
skills like modeling, texturing, lighting, animating, rendering, and compositing
that will help you across any other 3D animation project you hope to tackle in the future.
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If you want to see more from our Master of Microscopes James Weiss,
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