1861.] Conservation of Force applied to Organic Nature. 355 



place, then also mechanical work is done. The mechanical work is 

 very different according to the different kinds of muscular exertion. 

 If we walk only on a plane surface, we must overpower the resistance 

 of friction and the resistance of the air ; but these resistances are not 

 so great that the work which we do by walking on a plane is of 

 great amount. Our muscles can do work in very different ways. By 

 the researches of Mr. Redtenbacher, the director of the Polytechnic 

 School of Carlsruhe, it is proved that the best method of getting the 

 greatest amount of work from a human body is by the treadmill, that 

 is, by going up a declivity. If we go up the declivity of a hill we 

 raise the weight of our own body. In the treadmill the same work is 

 done, only the mill goes always down, and the man on the mill remains 

 in his place. 



Now we have researches on the amount of air which is taken in 

 and of carbonic acid given out during such work in the treadmill, 

 made by Dr. Edward Smith. He found that a most astonishing 

 increase of respiration takes place during such work. Now you all 

 know that if you go up a hill you are hindered in going too fast by the 

 great frequency and the great difficulty of respiration. This, then, 

 becomes far greater than by the greatest exertion of walking on a 

 plain, and really the difficulty is produced by the great mechanical 

 work which is done in the same time. Now, partly from the experi- 

 ments of Dulong and Desprez, and partly from the experiments of 

 Dr. Edward Smith, we can calculate that the human body, if it be in a 

 reposing state, but not sleeping, consumes so much oxygen, and burns 

 so much carbon and hydrogen, that during one hour so much heat is 

 produced that the whole body, or a weight of water equal to the weight 

 of the body, would be raised in temperature one degree and two- 

 tenths centigrade (two degrees and two-tenths Fahrenheit). Now 

 Dr. Edward Smith found that by going in the treadmill at such a rate 

 that if he went up a hill at the same rate, he would have risen during 

 one hour 1712 feet, that during such a motion he exhaled five times 

 as much carbonic acid as in the quiet state, and ten times as much as 

 in sleeping. Therefore the amount of respiration was increased in a 

 most remarkable way. If we now calculate these numbers we find that 

 the quantity of heat which is produced during one hour of repose is one 

 degree and two-tenths centigrade, and that these are nearly equivalent 

 to rising 1712 feet, so that therefore the amount of mechanical work 

 done in a treadmill, or done in ascending a hill at a good rate, is equi- 

 valent to the whole amount of heat which is produced in a quiescent 

 state. The whole amount of the decomposition in the living body is 

 five times as great as in a reposing and wakeful state. Of these five 

 quantities, one quantity is spent for mechanical work, and four-fifths 

 remain in the form of heat. Always in ascending a hill, or in doing 

 great mechanical work, you become hot, and the production of heat is 

 extremely great, as you well know, witliout making particular experi- 

 ments. Hence you see how much the decomposition in the body is 

 increased by doing really mechanical work. 



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