Septembee 18, 1908] 



SCIENCE 



355 



a certain insight into the reactions of 

 plants which we should not otherwise pos- 

 sess. This is, I allow, a very dangerous 

 tendency, leading to anthropomorphism, 

 one of the seven deadly sins of science. 

 Nevertheless, it is one that must be used 

 unless the great mass of knowledge accum- 

 ulated by psychologists is to be forbidden 

 ground to the physiologist. 



Jennings^ has admirably expressed the 

 point of view from which we ought to deal 

 with the behavior of the simpler organ- 

 isms. He points out that we must study 

 their movements in a strictly objective 

 manner : that the same point of view must 

 be applied to man, and that any resem- 

 blances between the two sets of phenomena 

 are not only an allowable but a necessary 

 aid to research. 



What, then, are the essential characters 

 of stimuli and of the reactions which they 

 call forth in living organisms? Pf offer 

 has stated this in the most objective way. 

 An organism is a machine which can be set 

 going by touching a spring or trigger of 

 some kind ; a machine in which energy can 

 be set free by some kind of releasing 

 mechanism. Here we have a model of at 

 least some of the features of reaction to 

 stimulation. 



The energy of the cause is generally 

 out of all proportion to the effect, i. e., a 

 small stimulus produces a big reaction. 

 The specific character of the result de- 

 pends on the structure of the machine 

 rather than on the character of the stimu- 

 lus. The trigger of a gun may be pulled 

 in a variety of different ways without af- 

 fecting the character of the explosion. 

 Just in the same way a plant may be made 

 to curve by altering its angle to the verti- 

 cal, by lateral illumination, by chemical 

 agency, and so forth; the curvature is of 

 the same nature in all cases, the release- 



' " The Behavior of the Lower Organisms," 1904, 

 p. 124. 



action differs. One of those chains of 

 wooden bricks in which each knocks over 

 the next may be set in action by a touch, 

 by throwing a ball, by an erring dog, in 

 short by anything that upsets the equilib- 

 rium of brick No. 1; but the really im- 

 portant part of the game, the way in 

 which the wave of falling bricks passes 

 like a prairie fire round a group of Noah's 

 Ark animals, or by a bridge over its own 

 dead body and returns to the starting- 

 point, etc. — these are the result of the 

 magnificent structure of the thing as a 

 whole, and the upset of brick No. 1 seems 

 a small thing in comparison. 



For myself I see no reason why the 

 term stimuhis should not be used in rela- 

 tion to the action of mechanisms in gen- 

 eral; but by a convention which it is well 

 to respect, stimulation is confined to the 

 protoplasmic machinery of living organ- 

 isms. 



The want of proportion between the 

 stimulus and the reply, or, as it has been 

 expressed, the unexpectedness of the result 

 of a given stimulus, is a striking feature 

 in the phenomena of reaction. That this 

 should be so need not surprise us. We 

 can, as a rule, only know the stimulus and 

 the response, while the intermediate pro- 

 ■ cesses of the mechanism are hidden in the 

 secret life of protoplasm. We might, 

 however, have guessed that big changes 

 would result from small stimuli, since it 

 is clear that the success of an organism in 

 the world must depend partly at least on 

 its being highly sensitive to changes in its 

 surroundings. This is the adaptive side 

 of the fundamental fact that living proto- 

 plasm is a highly unstable body. Here I 

 may say one word about the adaptation as 

 treated in the ' ' Origin of Species. " It is the 

 present fashion to minimize or deny al- 

 together the importance of natural selec- 

 tion. I do not propose to enter into this 

 subject; I am convinced that the inherent 



