THE ANIMAL AS A PRIME MOVER. 1 



By R. H. Thurston. 



PART I.— THE HUMAN ANIMAL AS A VITAL PRIME MOVER AND A 

 THOUGHT MACHINE; THE ENERGETICS OF THE VITAL MACHINE; ITS 

 TRANSFORMATIONS. 



The vital engine, the body of every vertebrate animal — from the 

 human ruler of all, down to the lowest organism having- a cartilagi- 

 nous frame — is to-day well recognized as, in the engineer's classifica- 

 tion, a ''prime motor," in which the latent forces and energies of a 

 combustible "food," of a fuel, as many suppose it, are evolved, trans- 

 ferred, and transformed to perform the work of the organism itself, to 

 supply heat to keep it at the temperature necessary for the efficient 

 operation of the machine, and for the performance of external work. 

 The value of .the machine as a prime mover is dependent upon the rela- 

 tion between this external work, so far as it can be applied to useful 

 purposes as labor, and the costs of its production in fuel or energy 

 supply, and in wear and tear and replacement, precisely as with any 

 other machine of the class, whether the source of power be chemical, 

 thermal, electrical, or vital. 



The work of the machine is, however, a very different quality and is 

 vastly different in quantity, useful work being compared with supplied 

 energy, and incidental expenditures from that of any other known 

 motor. In the water wheels and windmills, the office of the motor is 

 simply that of transfer of energy of flowing currents of fluid, of water 

 or of air, and without transformation, to mechanism suitable for giving 

 it useful application. The heat engines develop energy previously 

 "latent," potential, as the modern nomenclature would call it, into the 

 kinetic form of thermal motion, and, by transformation, so far as may 

 be practicable, into the dynamic form, make it available for work. 

 Electro-dynamic machinery similarly makes available by transforma- 

 tion the energy of the electric current, and none of these machines 

 has any other function than that of making useful some one energy 

 previously stored by the operations of nature in such form as to be 

 readily applied to his purposes by the hand of man. 



1 From the Journal of the Franklin Institute, Vol. CXXXIX, Nos. 829 to 831, Jan- 

 uary, February, and March, 1895. 



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