INTRODUCTION 5 



either without change of the atomic groups (physical phenomena), 

 or with changes in the same (chemical phenomena). 



These great empirical laws of the Conservation of Matter 

 (Lavoisier, 1789) and the Conservation of Energy (J. R. Mayer, 

 1842 ; Helmholtz, 1847) dominate living as well as non-living 

 Nature. A living being objectively considered may be conceived 

 as a machine transforming the matter and energy it derives from 

 the external world. As a physico-chemical science of life, 

 physiology will have fulfilled its task when it is able to provide 

 an adequate mechanical representation of the inner processes which 

 underlie the vital somatic phenomena, that is, when it succeeds 

 in giving a satisfactory explanation of these phenomena, and in 

 describing the processes on which they depend as links in the 

 causal chain of the grand Procession of Nature. 



The immense value of atomic and molecular mechanics, 

 considered as the basis of vital phenomena (i.e. Physiological 

 Materialism in the modern and scientific sense), is best appreciated 

 in reviewing the vast and rapid progress made by physiology, 

 since it has applied the positive methods of physics and chemistry 

 to the study of life, and has abjured the vain abstract speculations 

 used and abused at the beginning of the last century by the 

 so-called " natural philosophers." 



At the same time no sincere worker in the positive or scientific 

 direction can deny that the specifically vital somatic phenomena, 

 i.e. those by which living beings are differentiated from inorganic 

 bodies, are inexplicable by the known laws of chemistry and 

 physics, and that the psychical phenomena (of sensibility and 

 consciousness), which for each individual constitute the culminating 

 point of life, are altogether remote from any mechanical explana- 

 tion : they cannot in any way be regarded as necessary links 

 in the chain of cause and effect in the natural processes of Nature. 



It is probable that not a few of the still unexplained physio- 

 logical phenomena will become intelligible in the further progress 

 of physics and chemistry ; but even so, such phenomena as are 

 specifically vital, and psychical phenomena, will remain refractory 

 to any mechanical explanation. 



The dynamic finality proper to living beings (which is essenti- 

 ally distinct from the static finality of the cognate parts of a 

 machine created by human industry) ; the capacity for repro- 

 duction, reintegration, adaptation ; the innate tendency to evolve, 

 to progress, to become perfect, with relative independence of 

 environmental conditions, these and other specific phenomena of 

 living beings must, to all who are emancipated from theoretical 

 dogmatism, appear irreducible to a simple play of physical and 

 chemical energies, irreconcilable with the iron necessity of 

 mechanical laws. This is the position assumed by Neo-vitalism, 

 which starts from this affirmation and transcends the earlier 



