William Harvey and Circulation

So in this section we're going to focus on the work of another renaissance thinker who really caused a breakthrough in the medical world in 1628 when he published his book on the motion of the heart and as the title suggests this was about the way the human heart worked and also Harvey was particularly interested in the movement of the blood and he made a number of really significant discoveries on the topic of the circulatory system. Now a little bit about who William Harvey was he was an English physician he studied at Cambridge but then later on went to Padua and Padua is quite significant because if you remember that was where Vesalius had done a approach which included dissection influenced Harvey and Harvey was able to apply a lot of Vesalius's principles to his own work. Now when he comes back to England he marries this is Harvey and not Vesalius he marries the daughter of Elizabeth I's physician so basically he marries the daughter of the Queen's doctor and this really opens up a lot of doors for him so much so that in the year 1618 he becomes the King's physician to King James I and later on to James's son Charles. He also from 1609 works at St Bartholomew's Hospital in London and he conducts a number of experiments to look at the way that blood moves around the body so first of all he does some dissections and he does dissect dead bodies and we have a picture here I don't want to write on top of it so I'll see if I can bring it up there we are and he does experiments where he pushes down on things like arteries and veins and this is an illustration from his book he dissects dead bodies he also dissects the cold-blooded animals because their systems are slower he can see what's happening with their circulatory system and he can watch what's happening while they're still alive as well and then finally he's quite influenced by the development of renaissance mechanisms particularly the water pump and that helps to further his understanding as well now at this time people's understanding of the function of the heart really was based on the and Galen taught that blood was produced in the liver which he saw as the centre of the body and not the heart it was then sent to the heart which pumped it out to different parts of the body where it would basically be used up it would be consumed so blood was made up of food that people ate and it was carried to different parts of the body and then it was used up and the liver had to make some more so according to Galen the liver produces blood and the body consumes it he also taught that blood moved from the right ventricle to the left ventricle of the heart so the different chambers of the heart in tiny little holes through tiny little holes in the wall between them which is called the septum and what's interesting about this is that there was an islamic scholar from 13th century syria called Ibn Nafis who actually challenged Galen on this he said that there were no holes in the septum and that the blood got from the right ventricle to the left ventricle by going around the long way through the lungs which is actually much closer to the truth the thing is that nobody really pays very much attention to Ibn Nafis when he says this and it's only really picked up on in the 20th century when people historians are reading his work but William Harvey makes a number of discoveries over the course of his investigations that lead him to really challenge Galen's view so according to Harvey he measured how much blood was pumping through the arteries at any one time and he calculated that the amount of blood that pumped through a single place in the arteries in one hour was three times the weight of a man and at this rate if the body was consuming all that blood and the liver kept on having to make it Harvey calculated that the liver would need to produce 1,800 liters of blood a day which leads him to the conclusion that actually the liver is not constantly making new blood all the time instead blood circulates through the body and the heart doesn't just pump it to the ends of the body where it stops actually blood is going around the body all the time and this is a massive departure from the teachings of Galen however Harvey then has to prove how the blood we know how it's sent out it was sent out in the arteries but he then had to explain how the blood made it back to the heart and his theory was that arteries and veins were part of the same system so the arteries were sending the oxygenated blood out to different parts of the body and then the veins were bringing it back and Harvey proved that veins were really one way he tried pumping liquid through veins and he found that it would only go in one direction so he proved that veins would always send the blood back to the heart he did have a problem explaining how the blood got from the arteries to the veins and at this point he had to come up with a theory his theory was that there were tiny little blood vessels too small to see that took the blood from the arteries to the veins so he also theorized that capillaries i'm gonna write it in capitals because it's important carried the blood from the arteries to the veins he couldn't prove that though which is one of the many criticisms that people come up with against Harvey a lot of people are very offended that he questions Galen a lot of people think that it shows he doesn't really know what he's talking about and they believe that his ideas are just wrong he himself said that his practice as a physician dropped off a lot because of his and these are his words crackpot theories or crackpot ideas so at the time Harvey's ideas don't really get a lot of approval a lot of people disagree with him and a lot of people criticize him it takes a long time for these ideas to be accepted now it helps that in 1661 a scientist so 1661 there's a scientist called Marcello Malfighi that's an a in case it's not immediately obvious uses a microscope to provide proof that capillaries actually exist so that helps to justify Harvey's ideas but actually Galen continued to be used in textbooks and Galen's theories around this continued to be used until 1651 Harvey's ideas don't make it into textbooks until 1673 so 45 years after he came up with the theory so it doesn't get a very good reception and it doesn't take hold his ideas don't take hold very quickly but ultimately they do take hold and he also gives some valuable impetus to the field of medical research for one thing this really encourages i'm going to do an anachronistic light bulb here because he kind of gives other people ideas he encourages experimentation let's do the yellow encourages experimentation he proves the value of dissection as a way of finding things out about the body and he also inspires further research some people are very interested in what he has to say about the blood and the formation of the blood and they start to look into the dice that into digestion and they start to look at how the body makes blood so he kickstarts a lot of further research as well he also really challenges the use of phlebotomy and bleeding people remember Galen taught that some people have too much blood well according to Harvey they couldn't so this is a real challenge to phlebotomy as well and bleeding and the practice of putting people's veins open so although Harvey's ideas aren't very well received ultimately this is a major turning point in the medical understanding of how the body works