40 



My object in determining the musical note of a muscular contrac- 

 tion was to calculate by a second process a coefficient which would 

 represent the amount of work that an ounce weight of muscle would 

 be able to perform. The manner in which I conducted the experiments 

 was as follows. I held my arms horizontally, asking a friend to see that 

 they neither rose above nor fell below the horizontal line. I held them 

 in that position until I was completely tired ; then I placed different 

 weights on my arm in the same position, and I tried the experiment on 

 many other persons. You will be astonished, if you try the experiment, 

 how short a time you can hold out your arms perfectly horizontal. In 

 this way, if I knew the rate at which muscular contraction takes place 

 in the arms so held out, it was easy for a mathematician to calculate 

 the amount of work done by each ounce of muscle engaged in holding 

 up those arms. I had found that the musical note of the muscle vibrated 

 thirty-five or thirty-six times in the second ; and, having first got that 

 fact, from the experiments made with holding weights in my extended 

 arms, I was able to determine a second coefficient to be compared with 

 the other which I had previously deduced from the hydrostatical pres- 

 sure ; viz. , 20.576 lbs. This second coefficient came out exactly 20 lbs. ; 

 that is, the weight that can be lifted by an ounce of muscle of the heart 

 through one foot in a single minute. This result I believe any experi- 

 menter on such subjects will admit to come in a reasonable degree close 

 to that which I obtained from the hydrostatical pressure of the heart. 

 I am, therefore, entitled to consider that somewhere about 20 lbs. can be 

 lifted by every ounce of my heart in a single minute. But this conveys 

 to your minds no adequate conception of the enormous amount of work 

 which that represents. If I said 40 lbs. or 50 lbs. it would convey no 

 impression to your minds ; I therefore devised a plan for the purpose of 

 showing you in this lecture how much you ought to wonder at the great 

 work performed by the heart. I obtained from Mr. Robert Main in 

 Oxford, and Mr. Maclaren, the celebrated trainer, the length of the 

 Oxford and Cambridge boat-race course, and the cross-sections and 

 plans of the Oxford eight- oared boat. The average time in which the 

 race is rowed (it has been rowed twenty-one times in twenty-one years 

 over the same course) is 23 minutes 3^ seconds, and the length of the 

 course 154.31 miles. From these data, and from the plans and sec- 

 tions of the boats kindly supplied by Mr. Maclaren, I was enabled, 

 by using Professor Rankine's well-known formulse for the resistance of 

 ships, to determine the amount of work done by the muscles of the 

 young men who pull in this hardly contested race. I find that during 

 the twenty-three minutes the race lasts, every ounce of muscle in the 

 arms and legs of the rowers works at the rate of 20. 124 lbs. lifted 

 through one foot each minute. This comes out to be very much like 

 the amount of the work that my heart is doing at this moment ; indeed, 



