IS THE BODY A MACHINE? 53 



to do once more with the respiratory system, 

 and the process is simply a repetition of the 

 story of gas diffusion, chemical union, and 

 osmosis. It is sufficient here to say that the 

 process is just as simple and as easily explained 

 as those already described. The elimination of 

 these wastes is simply a problem of chemistry 

 and mechanics. 



In the removal of the ash, however, we have 

 something more, for here again we are brought 

 up against the vital action of the cell. This ash 

 takes chiefly the form of a compound known as 

 urea, which finds its way into the general circula- 

 tory system. From the blood it is finally removed 

 by the kidneys. In the kidneys are a large 

 number of bits of living matter (kidney cells), 

 which have the power of seizing hold of the urea 

 as the blood is flowing over them, and after thus 

 taking it out of the blood they deposit it in a 

 series of tubes which lead to the bladder and 

 hence to the exterior. The bringing of this ash 

 to the kidney cell is a mechanical matter, based 

 simply upon the flow of the blood. The seizing 

 of the urea by the kidney cell is a vital pheno- 

 menon which we must waive for the moment, 



Up to this point in the analysis there has been 

 no difficulty, and no one can fail to agree with 

 the conclusions. The position we reach is as 

 follows : So far as relates to the general problems 

 of energy in the universe the body is a machine. 

 It neither creates nor destroys energy, but simply 

 transforms one form into another. In attempt- 

 ing to explain the action of the machine, we find 

 that for the functions thus far considered (some- 



