IS THE BODY A MACHINE? 25 



broken up and a consequent increase in the amount 

 of refuse matter eliminated and the heat given 

 off. The income and outgo of the body in both 

 matter and energy is balanced. If, during the 

 experimental period, it is found that less energy 

 is liberated than that contained in the food assimi- 

 lated, it is also found that the body has gained in 

 weight, which simply means that the extra energy 

 has been stored in the body for future use. No 

 more energy can be obtained from the body than 

 is furnished, and for all furnished in the food an 

 equivalent amount is regained. There is no trace 

 of any creation or destruction of energy. While, 

 on account of the complexity of the experiment- 

 ing, an absolutely strict balance sheet cannot be 

 made, all the results are of the same nature. So 

 far as concerns measurable energy, all the facts 

 collected bear out the theoretical conception that 

 the living body is to be regarded as a machine 

 which converts the potential energy of chemical 

 composition, stored passively in its food, into ac- 

 tive energy of motion and heat. 



It is found, however, that the body is a machine 

 of a somewhat superior grade, since it is able to 

 convert this potential energy into motion with less 

 loss than the ordinary machine. As noticed above, 

 in all machines a portion of the energy is converted 

 into heat and rendered unavailable by radiating 

 into space. In an ordinary engine only about one- 

 fifteenth of the energy furnished in the coal can 

 be regained in the form of motive power, the 

 rest being radiated from the machine as heat. 

 Some of our better engines to-day utilize a some- 

 what larger part, but most of them utilize less 

 than one-tenth. The experiments with the living 

 body in the respiration apparatus above described, 



