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udied under these divisions were interrelated。 Always； however； the conflict between votaries of these sciences has been sharp； and the boundary lines between them have been constantly changing。 Since the great discoveries of Darwin； the zoologist； biologist； and physiologist have joined hands； but still the soul…body…spirit chaos has remained。 The physician has endeavored to fight the gross maladies which have been the result of disordered conduct； the psychologist has reasoned and experimented to find the laws governing conduct； and the priest has endeavored by appeals to an unknown god to reform conduct。
The great impulse to a deeper and keener study of man's relation； not only to man； but to the whole animal creation； which was given by Darwin； has opened the way to the study of man on a different basis。 Psychologists； physicians； and priests are now joining hands as never before in the great world…wide movement for the betterment of man。 The new science of sociology is combining the functions of all three； for priest； physician； and psychologist have come to see that man is in large measure the product of his environment。
My thesis to…night； however； will go beyond this common agreement； for I shall maintain； not that man is in _*large measure_ the product of his environment； but that environment has been the actual CREATOR of man； that the old division between body； soul； and spirit is non…existent； that man is a unified mechanism responding in every part to the adequate stimuli given it from without by the environment of the present and from within by the environment of the past； the record of which is stored in part in cells throughout the mechanism； but especially in its central batterythe brain。 I postulate further that the human body mechanism is equipped； first； for such conflict with environment as will tend to the preservation of the individual； and； second； for the propagation of the species； both of these functions when most efficiently carried out tending to the upbuilding and perfection of the race。
Through the long ages of evolution the human mechanism has been slowly developed by the constant changes and growth of its parts which have resulted from its continual adaptation to its environment。 In some animals the protection from too rough contact with surroundings was secured by the development of an outside armor； in others noxious secretions served the purposes of defense； but such devices as these were not suitable for the higher animals nor for the diverse and important functions of the human race。 The safety of the higher animals and of man had to be preserved by some mechanism by means of which they could become adapted to a much wider and more complex environment； the dominance over which alone gives them their right to be called 〃superior beings。〃 The mechanism by the progressive development of which living beings have been able to react more and more effectually to their environment is the central nervous system； which is seen in one of its simplest forms in motor plants； such as the sensitive plant and the Venus fly…trap； and in its highest development only in the sanest； healthiest； happiest； and most useful men。
The essential function of the nervous system was primarily to secure some form of motor activity； first as a means of securing food； and later as a means of escaping from enemies and to promote procreation。 Activities for the preservation of the individual and of the species were and are the only purposes for which the body energy is expended。 The central nervous system hag accordingly been developed for the purpose of securing such motor activities as will best adapt the individuals of a species for their self…preservative conflict with environment。
It is easy to appreciate that the simplest expressions of nerve response the reflexesare motor in character； but it is difficult to understand how such intangible reactions as love； hate； poetic fancy； or moral inhibition can be also the result of the adaptation to environment of a distinctively motor mechanism。 We expect； however； to prove that so…called 〃psychic〃 states as well as the reflexes are products of adaptation； that they occur automatically in response to adequate stimuli in the environment； that； like the reflexes； they are expressions of motor activity； which； although intangible and unseen； in turn incite to activity the units of the motor mechanism of the body； and finally； that any 〃psychic〃 condition results in a definite depletion of the potential energy in the brain…cells which is proportionate to the muscular exertion of which it is the representative。
That this nerve mechanism may effectively carry out its twofold function； first； of self…adaptation to meet adequately the increasingly complicated stimuli of environment； and second； of adapting the motor mechanism to respond adequately to its demands； there have been implanted in the body numerous nerve ceptors some for the transmission of stimuli harmful to the mechanism nociceptors some of a beneficial characterbeneceptors； and still others more highly specialized； which partake of the nature of both bene… and nociceptorsthe distance ceptors； or special senses。
A convincing proof that environment has been the creator of man is seen in the absolute adaptation of the nociceptors as manifested in their specific response to adequate stimuli； and in their presence in only those parts of the body which throughout the history of the race have been most exposed to harmful contacts。 We find they are most numerous in the face； the neck； the abdomen； the hands； and the feet； while in the back they are few in number； and within the bony cavities they are lacking。
Instances of the specific responses made by the nociceptors might be multiplied indefinitely。 Sneezing； for example； is a specific response made by the motor mechanism to stimulation of nociceptors in the nose； while stimulation of the larynx does not produce a sneeze； but a cough； stimulation of the nociceptors of the stomach does not produce cough； but vomiting； stimulation of the nociceptors of the intestine does not produce vomiting； but increased peristaltic action。 There are no nociceptors misplaced； none wasted； none that do not make an adequate response to adequate stimulation。
Another most significant proof that the environment of the past has been the creator of the man of to…day is seen in the fact that man has added to his environment certain factors to which adaptation has not as yet been made。 For example； heat is a stimulus which has existed since the days of prehistoric man； while the _x_…ray is a discovery of to…day； to heat； the nociceptors produce an adequate response； to the _x_…ray there is no response。 There was no weapon in the prehistoric ages which could move at the speed of a bullet from the modern rifle； therefore； while slow penetration of the tissues produces great pain and muscular response； there is no response to the swiftly moving bullet。
The response to contact stimuli then depends always on the presence of nociceptors in the affected part of the body and to the type of the contact。 Powerful response is made to crushing injury by environmental forces； to such injuring contacts as resemble the impacts of fighting； to such tearing injuries as resemble those made by teeth and claws （Fig。 9）。 On the other hand； the sharp division of tissue by cutting produces no adaptive response； indeed； one might imagine that the body could be cut to pieces by a superlatively sharp knife applied at tremendous speed without material adaptive response。
These examples indicate how the history of the phylogenetic experiences of the human race may be learned by a study of the position and the action of the nociceptors； just as truly as the study of the arrangement and variations in the strata of the earth's crust discloses to us geologic history。
These adaptive responses to stimuli are the result of the action of the brain…cells； which are thus continually played upon by the stimuli of environment。 The energy stored in the brain…cells in turn activates the various organs and parts of the body。 If the environmental impacts are repeated with such frequency that the brain…cells have no time for restoration between them； the energy of the cells becomes exhausted and a condition of shock results。 Every action of the body may thus be analyzed into a stimulation of ceptors； a consequent discharge of brain…cell energy； and a final adaptive activation of the appropriate part。 Walking； running； and their modifications constitute an adaptation of wonderful perfection； for； as Sherrington has shown； the adaptation of locomotion consists of a series of reflexes ceptors in the joints； in the limb； and in the foot being stimulated by variations in pressure。
As we have shown； the bene… and nociceptors orientate man to all forms of physical contactthe former GUIDE HIM TO the acquisition of food and to sexual contact； the latter DIRECT HIM FROM contacts of a harmful nature。 The distance ceptors； on the other hand； adapt man to his distant environment by means of communication through unseen forcesethereal vibrations produce sight； air waves produce sound； microscopic particles of matter produce s