AIM AND PROGRESS OF PHYSICAL SCIENCE. 335 



features. If the task of physical science be to determine laws, a 

 step of the most comprehensive significance towards that object 

 has here been taken. 



The application of the law of the conservation of force to 

 the vital processes of animals and plants, which has just been 

 discussed, leads us in another direction in which our knowledge 

 of nature's conformity to law has made an advance. The law 

 to which we referred is of the most essential importance in lead- 

 ing questions of physiology, and it was for this reason that Dr. 

 Mayer and I were led on physiological grounds to investigations 

 having especial reference to the conservation of force. 



As regards the phenomena of inorganic nature all doubts 

 have long since been laid to rest respecting the principles of the 

 method. It was apparent that these phenomena had fixed laws, 

 and examples enough were already known to make the finding 

 of such laws probable. 



In consequence, however, of the greater complexity of the 

 vital processes, their connection with mental action, and the 

 unmistakable evidence of adaptability to a purpose which 

 organic structures exhibit, the existence of a settled conformity 

 to law might well appear doubtful, and, in fact, physiology has 

 always had to encounter this fundamental question : Are all vital 

 processes absolutely conformable to law ? Or is there, perhaps, 

 a range of greater or less magnitude within which an excep- 

 tion prevails ? More or less obscured by words, the view of 

 Paracelsus, Helmont, and Stahl, has been, and is at present, 

 held, particularly outside Germany, that there exists a soul of 

 life (' Lebensseele ') directing the organic processes which is en- 

 dowed more or less with consciousness like the soul of man. 

 The influence of the inorganic forces of nature on the organism 

 was still recognised on the assumption that the soul of life only 

 exercises power over matter by means of the physical and chemi- 

 cal forces of matter itself; so that without this aid it could ac- 

 complish nothing, but that it possessed the faculty of suspending 

 or permitting the operation of the forces at pleasure. 



After death, when no longer subject to the control of the 

 soul of life or vital force, it was these very chemical forces of 



