August 29, 1913] 



SCIENCE 



293 



where are we to draw the boundary line, 

 and say " here the ego — the will — the rea- 

 son — emerges "? What attribute, after all, 

 has man which in its ultimate analysis is 

 not possessed by the lowest animals or by 

 the vegetable creation, even? From the 

 amceba, on through all the stages of ani- 

 mal existence, every action is but a re- 

 sponse to adequate stimulus; and as a re- 

 sult of adequate stimuli each step has been 

 taken toward the higher and more intricate 

 mechanisms which play the higher and 

 more intricate parts in the great scheme of 

 nature. 



The Venus fly trap responds to as deli- 

 cate a stimulus as do any of the contact 

 ceptors of animals, and the motor activity 

 resulting from the stimulus is as complex. 

 To an insect-like touch the plant responds ; 

 to a rough contact there is no response ; 

 that is, the motor mechanism of the plant 

 has become attuned to only such stimuli as 

 simulate the contact of those insects which 

 form its diet. It catches flies, eats and di- 

 gests them, and ejects the refuse. The 

 amoeba does no less. The frog does no 

 more, excepting that in its place in creation 

 a few more reactions are required for its 

 sustenance and for the propagation of its 

 species. Man does no more, excepting that 

 in man's manifold relations there are in- 

 numerable stimuli, for meeting which ade- 

 quately, innumerable mechanisms have 

 been evolved. The motor mechanism of the 

 fly trap is perfectly adapted to its pur- 

 pose. The motor mechanism of man is 

 adapted to its manifold uses, and as new 

 environmental influences surround him, we 

 must believe that new adaptations of the 

 mechanism will be evolved to meet the new 

 conditions. 



Is not this conception of man's activities 

 infinitely more wonderful, and infinitely 

 more comprehensible than is the conception 

 that his activities may be accounted for by 



the existence of an unknown, unimagina- 

 ble, and intangible force called "mind" 

 or " soul "? 



We have already shown how the nerve 

 mechanism is so well adapted to the in- 

 numerable stimuli of environment that it 

 can accurately transmit and distinguish 

 between the infinite variations of speed in 

 the ether waves producing light, and the 

 air waves producing sound. Each rate of 

 vibration energizes only the mechanism 

 which has been attuned to it. With mar- 

 velous accuracy the light and sound waves 

 gain access to the nerve tissue and are 

 finally interpreted in terms of motor re- 

 sponses, each by the brain pattern attuned 

 to that particular speed and intensity. So 

 stimuli and resultant actions multiplied by 

 the total number of the motor patterns in 

 the brain of man give us the sum total of 

 his life's activities — they constitute his life. 



As in evolutionary history the perman- 

 ence of an adaptation of the body mechan- 

 ism depends upon its value in the preser- 

 vation of the life of the individual and 

 upon its power to increase the value of the 

 individual to the race, so the importance 

 and truth of these postulates and theories 

 may well be judged on the same basis. 



The fundamental instincts of all living 

 matter are self-preservation, and the prop- 

 agation of the species. The instinct for 

 self-preservation causes a plant to turn 

 away from cold and damaging winds 

 toward the life-giving sun ; the inert mus- 

 sel to withdraw within its shell; the insect 

 to take flight ; the animal to fight or to 

 flee ; and man to procure food that he may 

 oppose starvation, to shelter himself and to 

 provide clothes that he may avoid the dan- 

 gers of excessive cold and heat, to combat 

 death from disease by seeking medical aid, 

 to avoid destruction by man or brute by 

 fight or by flight. The instinct to propa- 

 gate the species leads brute man by crude 



