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thers under the same stimulation； emotion； therefore； secures the final common path and he is unconscious of pain when he lashes； cuts； and bruises his body。 The phenomena of hysteria may be explained on this basis； as may the unconsciousness of passing events in a person in the midst of a great and overwhelming grief。 By constant practice the student may secure the final common path for such impressions as are derived from the stimuli offered by the subject of his study； and so he will be oblivious of his surroundings。 Concentration is but another name for a final common path secured by the repetition and summation of certain stimuli。
If our premises are sustained； then we can recognize in man no will； no ego； no possibility for spontaneous action； for every action must be a response to the stimuli of contact or distance ceptors； or to their recall through associative memory。 Memory is awakened by symbols which represent any of the objects or forces associated with the act recalled。 Spoken and written words； pictures； sounds； may stimulate the brain patterns formed by previous stimulation of the distance ceptors； while touch； pain； temperature； pressure； may recall previous contact…ceptor stimuli。 Memory depends in part upon the adequacy of the symbol； and in part upon the state of the threshold。 If one has ever been attacked by a snake； the threshold to any symbol which could recall that attack would be low； the later recall of anything associated with the bite or its results would produce in memory a recapitulation of the whole scene； while even harmless snakes would thereafter be greeted with a shudder。 On the other hand； in a child the threshold is low to the desire for the possession of any new and strange object； in a child； therefore； to whom a snake is merely an unusual and fascinating object； there is aroused only curiosity and the desire for the possession of a new plaything。
If we are to attribute to man the possession of a governing attribute not possessed by other parts of the animal creation； where are we to draw the boundary line； and say 〃here the ego the willthe reasonemerges〃？ 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 ameba； on through all the stages of animal existence； every action is but a response to an adequate stimulus； and as a result 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 delicate 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 digests them； and ejects the refuse （Fig。 47）。 The ameba 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 innumerable stimuli； for meeting which adequately； innumerable mechanisms have been evolved。 The motor mechanism of the fly…trap is perfectly adapted to its purpose。 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； unimaginable； and intangible force called 〃mind〃 or 〃soul〃？
We have already shown how the nerve mechanism is so well adapted to the innumerable 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 marvelous accuracy the light and sound waves gain access to the nerve tissue and are finally interpreted in terms of motor responses； 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 permanence of an adaptation of the body mechanism depends upon its value in the preservation 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 propagation 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 mussel 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 dangers 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 propagate the species leads brute man by crude methods； and cultured man by methods more refined； to put out of his way sex rivals so that his own life may be continued through offspring。 The life of the species is further assured by the protective action exercised over the young by the adults of the species。 As soon as the youngest offspring is able successfully to carry on his own struggle with environment there is no longer need for the parent； and the parent enters therefore the stage of disintegration。 The average length of life in any species is the sum of the years of immaturity； plus the years of female fertility； plus the adolescent years of the offspring。
The stimuli resulting from these two dominant instincts are now so overpowering as compared with all other environmental stimuli that the mere possession of adequate knowledge of the damaging effects of certain actions as compared with the saving effects of others will （other things being equal） lead the individual to choose the right； the self… and species…preservative course of action； instead of the wrong； the self… and species…destructive course of action。
The dissemination of the knowledge of the far…reaching deleterious effects of protracted emotional strain； of overwork； and of worry will automatically raise man's threshold to the damaging activating stimuli causing the strong emotions； and will cause him to avoid dangerous strains of every kind。 The individual thus protected will therefore rise to a plane of poise and efficiency far above that of his uncontrolled fellows； and by so much will his efficiency； health； and happiness be augmented。
A full acceptance of this theory cannot fail to produce in those in whose charge rests the welfare of the young； an overwhelming desire to surround children with those environmental stimuli only which will tend to their highest ultimate welfare。
Such is the stimulating force of tradition that many who have been educated under the tenets of traditional beliefs will oppose these hypotheseseven violently； it may be。 So they have opposed them； so they opposed Darwin； so they have opposed all new and apparently revolutionary doctrines。 Yet these persons themselves are by their very actions proving the efficiency of the vital principles which we have enunciated。 What is the whole social welfare movement but a recognition on the part of municipalities； educational boards； and religious organizations of the fact that the future welfare of the race depends upon the administration to the young of forceful uplifting environmental stimuli？
There are now； as there were in Darwin's day； many