384 AIM AND PROGEESS OF PHYSICAL SCIENCE. 



require for the increase of the organic matter of their 

 structures. Meanwhile it is true that exact quantitative 

 determinations of the equivalents of force, consumed and 

 produced in the vegetable as well as the animal kingdom, 

 have still to be made in order to fully establish the 

 exact accordance of these two values. 



If, then, the law of the conservation of force hold 

 good also for the living body, it follows that the physical 

 and chemical forces of the material employed in building- 

 up the body are in continuous action without inter- 

 mission and without choice, and that their exact con- 

 formity to law never suffers a moment's interruption. 



Physiologists, then, must expect to meet with an un- 



! conditional conformity to law of the forces of nature 

 in their inquiries respecting the vital processes; they 

 will have to apply themselves to the investigation of the 

 physical and chemical processes going on within the 

 organism. It is a task of vast complexity and extent ; 

 but the workers, in Germany especially, are both nu- 

 merous and enthusiastic, and we may already affirm 

 that their labours have not been unrewarded, inasmuch 

 as our knowledge of the vital phenomena has made 

 greater progress during the last forty years than in the 

 two preceding centuries. 



Assistance, that cannot be too highly valued, towards 

 the elucidation of the fundamental principles of the 

 doctrine of life, has been rendered on the part of descrip- 

 tive natural history, through Darwin's theory of the 

 evolution of organic forms, by which the possibility of 

 an entirely new interpretation of organic adaptability is 

 furnished. 



The adaptability in the construction of the functions 

 of the living body, most wonderful at any time, and 

 with the progress of science becoming still more so, was 

 doubtless the chief reason that provoked a comparison 



