HEAT, A MODE OF MOTION. ig 



whether it be internal or external to an organism, is, 

 in other words, to affirm a miracle. If this is weighed 

 against the physical view, " which in its perfection re- 

 duces every organic process to a problem of pure me- 

 chanics," it may be done in the certainly impartial words 

 of the naturalist just quoted: "I am of opinion that the 

 mechanical view of organic life is demonstrated only 

 when all the motions in an organism are shown to be 

 the eflfects of forces, which at other times also are inher- 

 ent in the atoms. But similarly I should regard the 

 vitalistic view as proved, if in any case a particular mo- 

 tion actually observed to take place in an organism were 

 shown to be mechanically impossible. At present, neither 

 is to be thought of. Nevertheless, if a decision must be 

 made without full proof, I provisionally profess myself 

 unequivocally in favour of the mechanical view. Not 

 only does it recommend itself a priori by its superior 

 probability and simplicity, but the progress of scientific 

 development raises it almost to a certainty. When it is 

 seen how certain phenomena — such as the evolution of 

 animal heat, which it was formerly believed could be 

 explained only by vital force — are now ascribed, even by 

 those who in general assume the existence of a special 

 vital force, to the universally active forces of the material 

 particles, we find ourselves almost forced to the convic- 

 tion that by degrees all the phenomena of life will become 

 susceptible of mechanical explanation." 



For the elucidation of the example just given of ani- 

 mal heat, let us observe that modern physics have learnt 

 to know heat as a peculiar mode of motion. The motion 

 of the hammer as it falls upon the anvil is not lost, but 

 is transformed into the atomic motion of the places struck, 



