ORGANISM AND MECHANISM 139 



personal experience had led him, the practical conclusion 

 is that we must keep as close as we can to the observable 

 realities, for it is in touch with these that we are most likely 

 to get fresh light. 



SUMMARY. 



Chemically considered, the organism is of a piece with its sur- 

 roundings (though very much more complex than any mere thing) ; 

 it may be usefully studied by chemical methods; it exhibits many 

 chemical processes which can be studied in isolation. Similarly, 

 many well-known physical processes occur in the living body, and 

 there is in its activity no known contradiction of the law of the 

 conservation of energy. A chemical and physical (i.e., theoretically 

 mechanical) description can be given of much that goes on in the 

 living body, and this kind of description will certainly extend its 

 scope. At the same time, there are difficulties in this chemico- 

 physical description; some vital processes do not illustrate Van't 

 Hoff's rule and it sometimes seems as if the organism were able to 

 effect some evasion of the second law of thermodynamics. 



But while chemical and physical (ideally mechanical) description 

 has its place and usefulness in the organic realm, it is inadequate to 

 answer the distinctively biological questions. It does not cover 

 the characteristic facts of life. 



If we consider the everyday functions of the body, we find that 

 there has not been given any chemico-physical description of any 

 total vital operation, such as the contraction of a muscle. We 

 cannot satisfactorily describe in mechanical terms either the con- 

 catenation of events in a function or the correlation of one set 

 of events with another set. This is still more marked when we 

 consider animal behaviour, with its co-ordination of acts in an 

 effective series. 



As to individual development, we cannot give a mechanical de- 

 scription of the condensation of the inheritance into a germ-cell, or 

 of the differentiation of the embryo, or of the regulation-phenomena 

 observed when an embryo rights itself after the building materials 

 of its living edifice have been seriously disarranged, or of the way 

 in which many developing parts seem to conspire towards one result. 

 Similarly, as regards organic evolution, we cannot offer a mechanical 



