ORGANISMS AND MACHINES 3 



cation to its environment, and whose action consists in 

 ?ontinual self -adjustment to changes in that environment. 

 What we call the life of the organism consists of the sum total 

 of all the activities which it thus exhibits. The question at once 

 arises : How, then, does a living organism differ from a mere 

 man-made machine ? and this question is one which it is by no 

 means easy to answer. An organism, however, is not merely a 

 piece of apparatus which has the power of maintaining itself for 

 a longer or shorter period in a state of equilibrium with its 

 environment and thereby preserving itself from destruction, for 

 it also has the power of reproducing its kind by a process of self- 

 multiplication. In the case of an artificial machine, where there 

 is little or no automatic adjustment , the forces of the environ- 

 ment very soon get the upper hand ; the metal work becomes 

 corroded by oxidation, or worn away by friction, and presently 

 the whole affair comes to a standstill. Oxidation and friction, 

 and innumerable other chemical and physical agencies also tend 

 to destroy the machinery of the living body, but for a longer or 

 shorter period thev are held in check by automatic processes of 

 repair and renewal, and when the inevitable end does come it is 

 usually not until the organism has produced at least enough off- 

 spring to take its place in the struggle for existence. 



One of the most brilliant writers of the nineteenth century, 

 Samuel Butler, has indulged in the somewhat fantastic sugges- 

 tion that some day the construction of machines might be so 

 perfected that they also would be able to reproduce their kind, and 

 the little steam-engines would be seen playing about the door of 

 the engine shed. It certainly does not seem possible that 

 machines will ever multiply in this way, but should they do so, 

 and should they at the same time be able to feed and grow, it is 

 difficult to see why they should not be as much entitled to be 

 called living organisms as any of the plants and animals which 

 inhabit the earth to-day. They would, however, still be totally 

 different from plants and animals both in structure and 

 composition. 



One of the most remarkable and characteristic features of the 

 living things which inhabit this earth is that they are all com-' 

 posed of very similar materials, whijj^ire very different in their 

 nature from any which we should be likely to choose in the 

 construction of a machine. In making an engine we select those 

 substances which seem best calculated to resist the destructive 



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