IS THE BODY A MACHINE? 53 



That a muscle is a machine in the sense of our 

 definition is beyond question. But the problem 

 of why a muscle acts is not answered by showing 

 that it derives its energy from broken food ma- 

 terial. There are plainly still left for us a num- 

 ber of fundamental problems, although the sec- 

 ondary ones are soluble. 



What can we say in regard to these funda- 

 mental vital powers of the active tissues ? Firstly, 

 we must notice that many of the processes which 

 we now understand were formerly classed as vital, 

 and we only retain under this term those which 

 are not yet explained. This, of course, suggests 

 to us that perhaps we may some day find an ex- 

 planation for all the so-called vital powers by the 

 application of simple physical forces. Is it a fact 

 that the only significance to the term vital is that 

 we have not yet been able to explain these pro- 

 cesses to our entire satisfaction ? Is the differ- 

 ence between what we have called the second- 

 ary processes and the primary ones only one of 

 degree ? Is there a probability that the actions 

 which we now call vital will some day be as read- 

 ily understood as those which have already been 

 explained ? 



Is there any method by which we can approach 

 these fundamental problems .of muscle action, 

 heart beat, gland secretion, etc. ? Evidently, if this 

 is to be done, it must be by resolving the body 

 into its simple units and studying these units. Our 

 study thus far has been a study of the machinery 

 of the body as a whole ; but we have found that 

 the various parts of the machine are themselves 

 active, that apart from the action of the general 

 machine as a whole, the separate parts have vital 

 powers. We must, therefore, get rid of this com- 



