326 



THE ANIMAL AS A PRIME MOVER. 



The efficiency of the thought-machine, as tke " brain worker" of modern 

 times has become, can not be estimated with even so much of accuracy 

 and certainty as that of the same organism employed as a vital prime 

 motor and mechanical engine. The considerations presented in the 

 last sections and in some ot the earlier portions of this discussion 

 would seem to indicate that the energy demanded by the brain for 

 transformation, presumably, in the operation of the apparatus as 

 the instrument of the mind and the tool of thought, may be fairly 

 taken as between 5 per cent for the case of the workingman giving all 

 his energies to his task, with little time and no strength for mental 

 labor, and for the nonintellectual creatures most nearly approaching 

 man in their constitution and structure, and 10 per ceut for the aver- 

 age intellectual product of civilization, up to perhaps 15 per cent in 

 the case of the steadily working professional brain worker. This is 

 mainly to be deducted from the energy applied by the laborer with his 

 muscles to his daily task, and the efficiency account would, in such 

 case, stand as a first and a rough approximation, perhaps, as follows: 



The intellectual machine — Receipts and expenditures — Efficiencies. 



Received food-content. 



Energy util- 

 ized. 



Per cent of energy 

 available. 



Total receipts (foot-pounds) 8, 500, 000 



7, 000, 000 



82 



100 



Waste, nonassimilation 1, 500, 000 



Available and applied 



1, 000, 000 

 3, 000, 000 

 2, 000, 000 

 1, 000, 000 



12 

 35 

 23 



12. 



14 



43 

 29 

 14 











This estimate makes the efficiency of the mental machine 14 per cent 

 if based upon the energy actually offered it in the circulatory system, 

 or 12 per cent if based upon the total food supply. If the exercise 

 taken can be made also commercially useful, the efficiency, on this 

 assumption, becomes 28 or 21 per cent, and if the essential work of the 

 machine is taken as that of providing its operator with heat and brain 

 power it becomes 57 or 47 per cent, the internal work as here denomi- 

 nated being the only waste except that of nonassimilation of food. 



Whatever may be taken as the proper method of reckoning efficien- 

 cies from the utilitarian standpoint, it is obvious that, in one form or 

 another, the machine — this vital engine — converts 80 or 90 per cent of 

 the energy received by it into new energies by transformation, and, 

 taking the real waste in the scientific sense as that of the heat rejected, 

 the efficiency for comparison with heat engines — in which but one pur- 

 pose exists, that of providing a single form of energy, transforming all 

 received into the mechanical form, so far as practicable — it is fair to 

 say that the former, with its efficiency as thus stated at 57 to 65 per 

 cent, excels the perfect heat engine of our time enormously, has twice 

 the highest theoretical efficiency of the best steam engine yet pro- 



