ah ladies things may seem unrelated but just keep your eye on the screen we'll come to the heart of the matter later on and these are fish eggs that we are going to put under the microscope and while we're putting them on i'd like mind you that the dogs the men they would pack are the penguin and the fish had one thing in common they had a beating heart and the blood circulation system now we're going to put these fish eggs under the microscope and magnify them very much and see what we can see and that's the various sign of life that we see in a hatching fish a it's the beating heart of the future phage now the fish has a very simple kind of hard compared to that  it's side because the weight is in the face it looks like a bald tie there and as it expands and contracts it forces the blood forward to the gills where it picks up oxygen the circulating system carries that oxygen to wherever it is needed in the fish which means all over the face then back to the heart again to get more oxygen when it is pumped once again through the gills of the fish that's a single chain circulation system within a lead valves and out lead valves in the pumping heart now when we come to the reptiles which is a slightly higher form of life we find that the sofia lading system has become a little bit more to get what you my colleague in another booster shot to pump it around the rest of the animal now there you see that in this hide the blood without oxygen on its way to the lungs and the blood with our kitchen being pumped around the reptile are mixed at one point but in the higher forms of life there is a wall of tissue that grows down like that and separates one half of the heart completely from the other half and in that's the same height that we have in the higher mammals and in the human beings now this is a diagram of this system of circulation of the blood in the human beings you see covered was filled with oxygen i mean it goes out to our extremities to our hands and to our feet into our heads and to our skin all over and as we saw the oxygen the blood flows back again through the veins to the lungs that it is pumped from the right side of the heart into the lungs and here's the double system an operation that goes out around our externalities back to the heart from the heart around the lungs to pick up oxygen and from the heart again out around the fringe of the system so to speak this is the human heart actually in operation here about the hundred thousand times a day in which operation it pumps about ten thousand cords of blood through the human system does that twenty thousand pounds edge ten tons so you can see that in a couple of now this is another closeup of the same system an operation that doubles circulation out around the human frame back to the heart then around the lungs back to the heart and out around again through the arterial system the vein system being the return trip to the right side of the heart minutes and it all depends on how much strain we put on the heart as to how fast it will be for us because it has a limit in beating fast and it also has a low limit beyond which it would cease to be t which case that would be the end of the individual now there are some diseases that can speed up the beating of the heart very much and there are other diseases that slow down the pulse of the building of the heart the danger there of course is that it will slow down to the stopping point his heart and of course it is not only a physical strain that may be dangerous there may be also a mental strain or an emotional strain and if the strain becomes too great then that person becomes a victim of heart disease this is an x ray picture of the human to but we can do better than that with patients these days we can put the patient between a sort of x rays and a flora scope and we can actually see the human heart beating and we can learn a great deal about it we can see whether it's under size or over size or whether it's swollen on one side or nah doctors can tell a good deal by watching the heart in operation another way of checking on a heart is by what is known as an electrocardiogram you know each time the heart beats it sends out an electric impulse and the electrocardiogram has a delicate instrument for registering these impulses and putting them on a strip of film electrocardiogram record of the beating of a patient's heart and it looks to me like a very good heart that a healthy patient with a normal heartbeat but this one below is a very flattering heart and the patient would exercises like this and we watch how the heart responds to the demand for an increase in its pace because the heart is a muscle in fact it's a great deal more than that it's a whole series of intricate criss cross muscles and we know that by proper treatment and by training we can develop our muscles so that we can do things that otherwise we couldn't do with them we can put them under strains and stresses that they very damaging if we had not developed them by training course all the training of athletes has pointed towards that end and notice that before athletes don't put themselves in that tremendous transportation