24 THE STORY OF THE LIVING MACHINE. 



up in his body material for future use; while if he 

 loses in weight, this means that he is consuming 

 his own tissues for fuel. Careful daily records of 

 his weight must therefore be taken. Estimates of 

 the solids, liquids, and gases given off from his 

 body must be obtained, for to carry out the ex- 

 periment an exact balance must be made between 

 the income and the outgo. The apparatus devised 

 for such experiments has been made very delicate ; 

 so delicate, indeed, that the rising of the individual 

 in the box from his chair is immediately seen in 

 a rise in temperature of the apparatus. But even 

 with this delicacy the apparatus is comparatively 

 coarse, and can measure only the most apparent 

 forms of energy. The more subtile types of energy, 

 such as nervous force, if this is to be regarded as 

 energy, do not make any impression on the appa- 

 ratus. 



The obstacles in the way of these experiments 

 do not particularly concern us, but the general re- 

 sults are of the greatest significance for our pur- 

 pose. While, for manifest reasons, it has not been 

 possible to carry on these experiments for any 

 great length of time, and while the results have 

 not yet been very accurately refined, they are all 

 of one kind and teach unhesitatingly one conclu- 

 sion. So far as concerns measurable energy or 

 measurable material, the body behaves just like 

 any other machine. If the body is to do work in 

 this respiration apparatus, it does so only by break- 

 ing to pieces a certain amount of food and using 

 the energy thus liberated, and the amount of food 

 needed is proportional to the amount of work done. 

 When the individual simply walks across the floor, 

 or even rises from his chair, this is accompanied 

 by an increase in the amount of food material 



