THE ANIMAL AS A MOTOR. 



41 



radiation to surrounding objects, the total amount of 

 heat produced by such combustion would vastly ex- 

 ceed the quantity discharged from the body in any 

 given time. This discrepancy is greater in cold-blooded 

 animals than in warm-blooded ; and, in many in- 

 stances, the heat given out is probably too small in 

 amount to account for combustion of any important 

 fraction of the aliment of the system. The animal ma- 

 chine is not thermodynamic in the usual acceptation of 

 that term, even if it be in any sense. 



Mon. J. Beclard was probably the first to attempt to 

 measure the relation of quantity and of transformation, 

 thermodynamically, if such energy-transformations 

 actually occur, in the animal machine. But he reached 

 no definite result. Herdenheim suceeded little better; 

 but Hirn found ways of investigation which gave real 

 quantitative results of importance. A certain corre- 

 spondence was found between work performed and 

 heat exhaled ; but nothing in his experiments gave in- 

 dications of the method of production of that heat ; and 

 it is still impossible to say whether the heat is the direct 

 product of oxidation of food, the result of oxidation of 

 worn muscular and other tissue, or due to a number of 

 thermal and other interactions occurring within the 

 body and as yet beyond the reach of scientific observa- 

 tion. The disappearance of heat unquestionably estab- 

 lished by Hirn's researches may or may not have been 

 due to thermodynamic transformations. Whatever 

 form of energy-transformation characterizes the vital 

 machine, the wastes of energy take the final form of 

 heat, and its quantity would, in any case, be reduced by 

 the production of mechanical energy and the perform- 

 ance of work within and without the body. 



