IS THE BODY A MACHINE ? 67 



mental vital powers of the active tissues? 

 Firstly, we must notice that many of the pro- 

 cesses 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 explanation 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 processes to our entire satisfac- 

 tion? Is the difference between what we have 

 called the secondary 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 readily 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 complicated machinery, which 

 confuses the problem, and see if we can find the 

 fundamental units which show these properties, 

 unencumbered by the secondary machinery 

 which has hitherto attracted our attention. 

 We must turn now to the problem connected 



