PART I. 



THE RUNNING OF THE LIVING MACHINE. 



CHAPTER I. 



IS THE BODY A MACHINE? 



THE problem before us in this section is to find 

 out to what extent animals and plants are ma- 

 chines. We wish to determine whether the laws 

 and forces which regulate their activities are the 

 same as the laws and forces with which we ex- 

 periment in the chemical and physical laboratory, 

 and whether the principles of mechanics and the 

 doctrine of the conservation of energy apply equal- 

 ly well in the living machine and the steam engine. 



It might be inferred that the proper method of 

 study would be to confine our attention largely to 

 the simplest forms of life, since the problems 

 would be here less complicated, and therefore of 

 easier solution. This, however, has not been nor 

 can it be the method of study. Our knowledge 

 of the processes of life have been derived largely 

 from the most rather than the least complex 

 forms. We have a better knowledge of the physi- 

 ology of man and his allies than any other ani- 

 mals. The reason for this is plain enough. In 

 the first place, there is a value in the knowledge of 

 the life activities of man entirely apart from any 

 theoretical aspects, and hence human physiology 



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