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the theatre of the Meath Hospital in Dublin, performed upon a poor 

 man, in whom, from various circumstances, I felt an interest. I was 

 merely a spectator at the operation, therefore I had leisure to witness 

 a remarkable phenomenon, and to draw inferences from it, which I 

 could not have done if I had been actively engaged. In the course of 

 the operation, a large artery was cut in a very unusual place, and, 

 therefore, some delay occurred in tying it. The blood spouted in jets 

 from the wounded artery for a minute, or two minutes, before it could 

 be tied. When the operation was over, I examined with care the 

 height of the table on which the man lay. The floor, which had been 

 recently cleaned, was covered with spurts of blood which had fallen 

 from the wounded man, and, by the application of a little geometry to 

 the problem, 1 was easily able to ascertain, by taking the height of the 

 table and the farthest positions of the spots of blood on the floor, the 

 velocity with which the blood issued from the wounded artery. The 

 curve described by the blood is a parabola, and, given two points on 

 the parabola, every geometer knows that we can construct the para- 

 bola and calculate the angle of elevation and the velocity with which 

 the fluid is projected. As soon as I had made this calculation, I found 

 that if I had cut the artery of a man, and allowed the blood to spout 

 directly into the air, it would spout to the height of 2,58 feet. Taking 

 the mean of all Dr. Flales's experiments upon horses, I find that 2.53 

 feet is the height to which the artery of a horse will spout. We now 

 have a most important and valuable result. We cannot compare 

 directly the hydrostatical pressure inside the human heart with the 

 hydrostatical pressure inside the heart of an ox, or of a cow, or of a 

 horse : but we can, by this determination of the velocity of spouting 

 blood, show a close relationship between the circulation in our own 

 frames and the circulation in these animals, and, therefore, we may 

 apply with confidence the coefficient of resistance which we find in the 

 horse and the ox to our own cases. When this coefficient of resistance 

 is used in the case of man, and the calculation is completed, we find 

 the hydrostatical pressure inside the human heart to amount to 9.923 

 feet of blood ; and, by using the number of times the heart beats — 

 seventy times each minute — and the quantity of blood projected from 

 the heart at each contraction, we can calculate, by very simple and 

 elementary processes, the work done in a given time by the human 

 heart. Now this work I shall represent for you in a form extremely 

 easy to remember — a form which will show you the extraordinary 

 amount of work that is done. I shall suppose that I cut out an ounce 

 of muscle from the heart, and that I ask myself this question. What 

 number of pounds can that contracting muscle lift in the course of a 

 minute ? I find that the contracting muscle, a single ounce in weight, 

 of the human heart, will lift 20.576 pounds through the height of one 



