IS THE BODY A MACHINE? 23 



perimental demonstration it would be necessary 

 to make an accurate determination of the amount 

 of energy an individual receives during a given 

 period, and at the same time a similar measure- 

 ment of the amount of energy liberated in his 

 body either as motion or heat. If the body is a 

 machine, these two should exactly balance, and if 

 they do not balance it would indicate that the 

 living organism either creates or destroys energy, 

 and is therefore not a machine. Such experiments 

 are exceedingly difficult. They must be per- 

 formed usually upon man rather than other ani- 

 mals, and it is necessary to inclose an individual 

 in an absolutely sealed space with arrangements 

 for furnishing him with air and food in measured 

 quantity, and with appliances for measuring accu- 

 rately the work he does and the heat given off 

 from his body. In addition, it is necessary to 

 measure the exact amount of material he elimi- 

 nates in the form of carbonic acid and other 

 excretions. Such experiments present many diffi- 

 culties which have not yet been thoroughly over- 

 come, but they have been attempted by several 

 investigators. For the purpose of such an ex- 

 periment scientists have allowed themselves to be 

 shut up in a small chamber six or eight feet in 

 length, in which their only communication with 

 the outer world is by telephone and through a 

 small opening in the side of the chamber, occa- 

 sionally opened for a second or two to supply the 

 prisoner with food. In such a chamber they have 

 remained as long as twelve days. In these experi- 

 ments it is necessary to take account not only of 

 the food eaten, but of the actual amount of this 

 food which is used by the body. If the person 

 gains in weight, this must mean that he is storing 

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