CHAP, in ORGANIC ADAPTABILITY 23 



a series of molecular, presumably chemical, changes. But 

 physiologists for the mor.t part agree in the hypothesis 

 which it is well to ^member is no more than a hypothesis 

 that if we knew ,11 about these changes, we should find 

 them to be only very complicated results of the same set 

 of physical laws in accordance with which the grass bows 

 before the wind. 



Before discussing this question let us look at the broad 

 facts of organic adaptability as we find them, and form 

 from them a conception of what the organism can do. If 

 we assume that the prevailing physiological conception is 

 correct, and that the organism is in fact a cunningly 

 contrived machine, we may remember that every machine 

 has a function and character of its own. It is composed 

 of parts which, taken by themselves, are common to many 

 machines, and work in accordance with highly general 

 laws, yet in their combination make up a machine which 

 may be quite individual, and work in a way peculiar to 

 itself. The machine as a whole may draw a train, or spin 

 cotton, and any one, an onlooker or a purchaser, may be 

 allowed to ask what it does without asking how it is 

 built. If the organism is a machine, if it is made up of 

 parts each of which can be found also in the inorganic 

 world, and acts in accordance with the very same laws 

 which prevail in that sphere, still the combination of these 

 parts may be distinctive, and the work it does may be 

 peculiar. It may be to evolve carbonic acid, or it may be 

 to produce poetry. We can learn something of the 

 character of its work, and of the way in which it does it, 

 even if we can form no satisfactory theory as to the 

 structure of the machine. 



2. The normal life of any organism from highest to 

 lowest is a process of unceasing change. It involves a con- 

 stant interchange of substance with the outer world, an 

 equally constant metabolism or transformation within itself 

 of the substances which it takes up from without, and a 

 no less constant transformation of energy. Such processes 

 are common to all organisms. If we spoke only of the 

 higher forms, many other activities could of course be 

 added. Throughout this unceasing process ojf change, 



