THE LIVING MACHINE BUILDING FACTORS. 201 



SUMMARY OF NATURE'S POWER OF BUILDING 

 MACHINES. 



Let us now notice the position we have reached. 

 Our problem in the present chapter has been to 

 find out whether nature possesses forces adequate 

 to explain the building of machines with their 

 parts accurately adapted to each other so as to 

 act harmoniously for certain ends. Astronomy 

 has shown that she has forces for the building of 

 worlds ; geology, that she has forces for making 

 mountain and valley ; and chemistry, that she has 

 forces for building chemical compounds. But the 

 organism is neither a world, nor a mass of matter, 

 nor a chemical compound. It is a machine. Has 

 nature any forces for machine building ? We have 

 found that by the use of the three factors, repro- 

 duction, variation, and heredity, nature is able to 

 produce a machine of ever greater and greater 

 complexity, with the parts all adapted to each 

 other. Now the difference between a machine 

 and a mass of matter is simply in the adaptation 

 of parts to act harmoniously for definite ends. 

 Hence if we are allowed these three factors, we 

 can say that nature does possess forces adequate to 

 the manufacture of machines. These forces are 

 not chemical forces, and the construction of the 

 machine has thus been brought about by forces 

 entirely different from those which produced the 

 chemical molecule. 



But we have plainly not reached the bottom 

 of the matter in our attempt to explain the 

 machinery of living things. We have based the 

 whole process upon three factors. Reproduction, 



