200 NO SPONTANEITY IN PROTOPLASM. 



Nor if we look upon it as, what indeed it is, a compound of 

 high potential energy capable of evolving force and thus 

 moving itself by the rearrangement of its constituent atoms, 

 does that help the question ; for the possibly very small initial 

 force required for that change is just as impossible to conceive 

 without adequate cause, as the whole force for moving it and 

 keeping it moving for ever without equivalent communication 

 of force. Some have suggested that the revival of the theory 

 of Lucretius as to the dynamic state of all matter above spoken 

 of, may help us here. But it helps nothing, for these move- 

 ments are all in equilibrium, and to change the motion of a 

 body already in motion requires an adequate cause just as much 

 as to start it from rest. So we are compelled to admit the 

 existence of an exciting cause in the form of some force from 

 without, to give the initial impulse in all vital actions ; this is 

 the stimulus. When this is once given the amount of action or 

 work depends on the potential energy of the protoplasm and 

 pabulum which are decomposed and may bear no calculable 

 proportion to the initial impulse, just as a spark may explode 

 any mass of gunpowder, or the nutter of a bird's wing start an 

 avalanche. We thus see how the stimuli apparently produce 

 results far beyond the intrinsic energy conveyed by them. It 

 is on the whole question of stimuli that Dr. Beale differs so 

 widely from other physiologists, and especially from Fletcher, 

 who is, above all others, careful to keep the essentiality of them 

 in due prominence. Dr. Beale does not even represent cor- 

 rectly the position of the stimulus. He says* that if you call 

 the development of the egg a consequence of the action of heat 

 as a stimulus, you may as well say that a steam-engine is a con- 

 sequence of the coal that takes part in generating the steam 

 that turns the lathes that are used in its construction. This is 

 not a correct statement of the position that the stimulus gives 

 merely the initial impulse to a substance like protoplasm, which 

 has not only a store of potential energy, but the directing power 

 of using it by virtue of its marvellous molecular organization. 

 Tke true analogy is with a steam-engine having its boiler 

 charged, and the stimulus is, as it were, the power which turns 

 * " Protoplasm," 3rd edition, p. 270. 



