140 NATURE AND LIFE. 



is the far more perfect machine. While the best-made 

 steam-engines only utilize -^^ of the disposable force, the 

 muscular system of man, according to Him, accounts for 

 T^jAr- On the other hand, the animated motor has this 

 peculiarity, that its sources of heat and its mechanical 

 arrangements are intimately commingled, that its heat is 

 produced by organs in motion with a sort of general diffu- 

 sion, and that the machine itself becomes in turn trans- 

 formed within itself into heat ; an incredible complication, 

 of which science has succeeded in unraveling the simple 

 laws only by dint of the united efforts and resources of 

 physics, chemistry, and biology. 



As some physiologists hold, heat must not only be the 

 source of motion in the system, but must also undergo 

 transformation into nervous activity. The functional action 

 of the brain must be a labor, exactly like that of the biceps. 

 Mind itself should be regarded as engendered by heat. 

 Late experiments by Valentin, Lombard, Byasson, and es- 

 pecially Schiff, would seem to prove, it is thought, that 

 there is a proportional and constant relation between the 

 energy of nervous functions and the heat of the parts in 

 which they are effected. Gavarret boldly concludes, from 

 his researches, that heat has the same relations to the 

 nervous system that it has to the muscular system ; only, 

 in the case of the muscles, the force produced exhibits it- 

 self externally by visible phenomena, while in that of the 

 nerves it is exhausted internally in profound molecular 

 action, which eludes any exact measurement. A given 

 sum of heat developed in the system would thus be on one 

 side a mechanical equivalent, and on the other a psycho- 

 logical equivalent. Gavarret, who is a cautious savant and 

 true to experimental methods, doubtless does not go so far 

 as to maintain that thought and feeling can be estimated 

 in heat-units ; he even asserts that there is no common 

 measure between intelligence and heat; but less timid 



