Bloody perceptions – Blood series, Part I

Science HeaderWith the opening of the Science Gallery’s latest exhibition, BLOOD, I thought it would be interesting to take a look at how the perceptions of blood have changed over the years, and how they are still changing today.

Early thinking
The first personality to examine is Hippocrates, the founder of medicine as a rational science. Hippocrates devised a medical system that didn’t attribute every disease to some supernatural cause. Instead, according to his system, the human body is filled with four humours (bodily fluids) that are black bile, yellow bile, phlegm, and blood. Diseases arose when these humours were out of balance. Following on from this idea, Hippocrates proposed that menstruation was a way for the female body to eliminate excess blood in order to prevent the humours from becoming unbalanced, and in this way, menstruation provided the inspiration for bloodletting, a treatment where blood is taken from a patient to help treat illness.

In comparison to many other historical views, Hippocrates’ thoughts on menstruation were fairly reasonable. As an idea of just how utterly ridiculous some opinions were, Pliny the Elder, a naturalist from the Roman Empire, wrote that: “So magical is the power of women during their monthly periods that they say that hailstorms and whirlwinds are driven away if menstrual fluid is exposed to the flashes of lightning.”

It seems to me that this depiction of blood would not have been so dominant in a less patriarchal society. Blood is much more commonplace in the life of women, so it seems reasonable to suggest that they wouldn’t have thought of it as this supernatural, mystical substance. Even centuries later, blood in general was still imbued with a spiritual quality. For example, in 1651, William Harvey, the first person to describe the systemic circulation of blood wrote; “The blood therefore is a spirit by reason of its most excellent powers and virtues. It is also celestial because in that spirit is housed a nature that is the soul”.

Moving forward
So how did we move away from this conception of blood towards the view that we have of it today? To find out, we’re going to move to London in 1667, seven years after the foundation of the Royal Society, nowadays recognised as a collection of the finest scientists in the world. The Royal Society began from groups of physicians and natural philosophers joining together, with early members including Robert Boyle, Christopher Wren and Robert Hooke.

This assortment of learned minds became fascinated with blood so naturally they decided to devise experiments in order to reveal its true nature, experiments which included the first animal to human transfusion. For this test, it was proposed that the blood of a lamb be transfused into a madman to hopefully render him as docile as the sheep. A man named Arthur Coga was offered a guinea by the Royal Society to participate in the study. Coga was described as being “debauched, frantic and somewhat cracked in the head”. In other words, he was a perfect candidate.

On the morning of the experiment, Coga was led into a hall and sat down beside a table, upon which a lamb was tied down. Two Fellows of the society cut a slit across an artery in the sheep’s neck. Coga tasted the blood of the lamb and liked it so much that he became much more eager to proceed. The Fellows then cut a vein in Coga’s arm before joining the two vessels by means of a metal tube.

After the injection of about 12 ounces of sheep’s blood, Coga reported feeling much improved. A witness reported that “the patient was well and merry, and drank a glass or two of canary, and took a pipe of tobacco”.

Unfortunately, a second transfusion caused Coga’s health to decline with one witness stating that “the wildness of his mind remains unchanged.” Soon afterwards, reports came in from all over Europe that the experiment had been tried several times elsewhere, often with fatal results. It was at this point that the conception of blood in purely biological, mechanical terms began to become more prevalent.

Modern treatments
Indeed, this all seems fairly preposterous to us now and we might think it strange that these great minds could ever have possibly proposed such outlandish experiments. What is perhaps even stranger however is that they might just have been onto something after all. I say this because research conducted recently in San Francisco has the potential to change our perceptions of blood and what it can do. Saul Villeda is a neuroscientist who experiments on mice. There is a very well-known experiment known as the Morris water navigation task where a mouse is placed in a large pool that contains a platform which the mouse cannot see but which it would love to get onto in order to escape the water. The mouse is repeatedly dropped into the pool so as to determine how quickly it can learn and remember the location of the platform. Young mice learn the location of the platform after six or seven tries and once they’ve learned it, they don’t forget it. In contrast, old mice just never learn, no matter how many times they try.

Saul used this experiment to test if blood can affect learning and memory.He took blood from old mice and put it in young mice and repeated the water maze test only to find that these mice did much, much worse. They behaved as if they had suddenly aged dramatically, wandering aimlessly around the maze. This suggested that the old blood had changed their ability to learn. In the follow-up trial, young mice were given old blood and vice versa. This time, the researchers examined the brains of the mice to see if there was a change in the prevalence of so called “baby” neurons. These neurons are constantly being made by our brain when we’re young but as we age, less neurons are made.

When the results were analysed, it became clear that in the young mice that had been given old blood, there was a 25% decrease in baby neurons. With the old mice that were given young blood, there were two to three times as many neurons and furthermore, they looked much healthier than you would expect in an older mouse. Even more importantly, there was a 20% increase in connections between brain cells. These connections normally decrease as we age which limits the extent to which neurons can communicate. This is thought to be the mechanism by which problems in learning and memory arise.

The researchers believe that the young blood contains certain chemicals which old blood lacks and that once the old mouse gets more of these, the aging process is reversed. It remains to be seen if the same effect would occur in humans but if it did, this could lead to new ways of treating conditions such as Alzheimer’s and Parkinson’s. For example, the relevant chemical factors in young blood could be isolated and used as a preventative therapy. If the cost of production was sufficiently low, one could imagine a scenario where products containing those factors become as prevalent as multivitamins. While such a product may be well in the future, the new exhibition in the Science Gallery is open right now, so be sure to check it out!

Image: Incept Saves Blog