LIFE 329 



inevitably bound to physics by the fact that life is never 

 found apart from physical associations. Mechanism, on 

 its side, does not as a theory involve a discussion of 

 biological phenomena, but biology without a discussion of 

 mechanism is necessarily incomplete.^ 



" The elements of living matter are identical with 

 those of mineral bodies ; and the fundamental laws of 

 matter and motion apply as much to living matter as to 

 mineral matter ; but every living body is, as it were, a 

 complicated piece of mechanism which 'goes,' or lives 

 only under certain conditions." 



So wrote Professor Huxley in 1880. 



The use of physical terms abounds in biology, often, I 

 fear, with scarcely accurate definition. Nageli talks of 

 the " known forces of the organism, heredity and varia- 

 bility " ; Weismann speaks of the impossibility of the egg 

 being " controlled by two forces of different kinds in the 

 same manner as it would have been by one of them alone " ; 

 he further talks of " forces residing in the organism " 

 influencing the germ-plasm, which imperceptible entity he 

 halves and divides as if it were a physical quantity." 

 Lankester speaks of " that first protoplasm which was the 

 result of a long and gradual evolution of chemical 

 structure and the starting-point of the development of 

 organic form." Biologists lay the greatest weight on the 

 " chemical structure " of protoplasm and the chemical 

 processes which are or accompany physiological functions, 

 while free use is made of such terms as " unit-mass of 

 living matter," " resultant of organic forces," " molecular 

 stimuli," " continuity of organic substance," " conditions of 

 tension and movement," " physical constitution necessary 



1 From the author's standpoint, of course, conceptions as representing the 

 products of the perceptive faculty are largely conditioned by the perceptive 

 faculty of an individual genus, man (pp. 82-87, ^77)> ^"d therefore their 

 nature may be uUimately elucidated by biological, in particular psychological, 

 inquiry. 



^ If Spencer can be included in the list of biologists, it will be found that 

 he uses force without special definition in the following senses : (i.) As cause 

 of change in motion ; (ii.) as a biological process ; (iii.) as a name for kinetic 

 energy ; (iv. ) as a name for potential energy; (v.) as a general name for 

 physical sense-impressions, such as light and heat, etc. ! 



