132 THE STORY OF THE LIVING MACHINE. 



there any forces in nature which are of a sort as 

 to enable us to use them to explain the building 

 of machines? Plants and animals are the only 

 machines which nature has produced. They are 

 the only instances in nature of a structure built 

 with its parts harmoniously adjusted to each other 

 to the performance of certain ends. All other 

 machines with which we are acquainted were 

 made by man, and in making them intelligence 

 came in to adapt the parts to each other. But in 

 the living organism is a similarly adapted ma 

 chine made by natural means rather than arti- 

 ficial. How were they built ? Does nature, apart 

 from human intelligence, possess forces which can 

 achieve such results ? 



Here again we must attack the problem from 

 what seems to be the wrong end. Apparently it 

 would be simpler to discover the method of the 

 manufacture of the simplest machine rather than 

 the more complex ones. But this has proved con- 

 trary to the fact. Perhaps the chief reason is that 

 the simplest living machine is the cell whose study 

 must always involve the use of the microscope, 

 and for this reason is more difficult. Perhaps it is 

 because the problem is really a more difficult one 

 than to explain the building of the more complex 

 machines out of the simpler ones. At all events, 

 the last fifty years have told us much of the 

 method of the building of the complex machines 

 out of the simpler ones, while we have as yet not 

 even a hint as to the solution of the building of 

 the simplest machine from the inanimate world. 

 Our attention must, therefore, be first directed to 

 the method by which nature has constructed the 

 complex machines which we find filling the world 

 to-day in the form of animals and plants. 



