in ORGANIC ADAPTABILITY 31 



It is possible, again, to take up those points of difference, 

 and urge that each can be matched in the inorganic world. 

 The pendulum, for example, is in fact constantly oscil- 

 lating about the equilibrium point, and its existence as a 

 pendulum may not unfairly be said to depend upon its so 

 doing. But the continued motion of the pendulum de- 

 pends upon an outside force. It has no power of accumu- 

 lating afresh the energy which it loses at each swing. It 

 is not like the organism, self-maintaining. That is to 

 say, it does not of itself find the means of maintaining the 

 process which constitutes its existence. 



This last point of contrast is, indeed, challenged by 

 Dr. Verworn, 1 who compares an organism with a steam 

 engine in its need for being supplied with energy from 

 without. The steam engine is supplied with fuel, and 

 this, he urges, is analogous to the supply of energy to the 

 organism, through its food. But here, again, the analogy 

 seems only to carry us a part of the way. The steam 

 engine does not go to look for coal when it runs short, nor 

 would it dream, as the engineer has dreamt, of substituting 

 oil in case coal were not available. 2 The case of machinery 



1 Op. cit. p. 123. 



2 A similar criticism applies to an ingenious example adduced by Dr. 

 Verworn to show that continuous metabolism, by which a body is con- 

 tinually being built up from certain materials which are as constantly 

 broken down and excreted, is not peculiar to living organisms. 



" A simple example of this is found in the behaviour of nitric acid in 

 the production of concentrated sulphuric acid. If nitric acid be mixed 

 with sulphurous anhydride, which is obtained in the manufacture of 

 sulphuric acid by roasting sulphur ore, the sulphurous acid withdraws 

 oxygen from the nitric acid and passes over into sulphuric acid, while the 

 nitric acid becomes nitrous acid. If the constant entrance of fresh air 

 and water be provided, the nitric acid is constantly reformed from the 

 nitrous acid and gives a part of its oxygen again to new quantities of 

 sulphurous acid, so that the molecule of nitric acid is continually being 

 alternately broken down with loss of oxygen and built up with absorption 

 of oxygen. In this manner, with the same quantity of nitric acid, an 

 unlimited quantity of sulphurous acid can be changed into sulphuric 

 acid." Op. cit. p. 125. 



This continuous process can be maintained under certain uniform con- 

 ditions. An organism will maintain a number of such processes at once, 

 digesting, respiring, secreting, and at the same time adapting its actions 

 to the acquisition of new material, and all under more or less varying 

 conditions of the outer world. Could the nitric acid adapt itself to a 

 change of diet ? Of course, the adaptability of the organism is also 

 limited. But the point seems to be this : If we change the conditions 

 which affect the nitric acid, we shall inevitably increase or decrease its 



