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thereal vibrations produce sight； air waves produce sound； microscopic particles of matter produce smell。 The advantage of the distance ceptors is that they allow time for orientation； and because of this great advantage the majority of man's actions are responses to their adequate stimuli。 As Sherrington has stated； the greater part of the brain has been developed by means of stimuli received through the special senses； especially through the light ceptors； the optic nerves。
We have just stated that by means of the distance ceptors animals and man orientate themselves to their distant environment。 As a result of the stimulation of the special senses chase and escape are effected； fight is conducted； food is secured； and mates are found。 It is obvious； therefore； that the distance ceptors are the primary cause of continuous and exhausting expenditures of energy。 On the other hand； stimuli applied to contact ceptors lead to short； quick discharges of nervous energy。 The child puts his hand in the fire and there is an immediate and complete response to the injuring contact； he sees a pot of jam on the pantry shelf and a long train of continued activities are set in motion； leading to the acquisition of the desired object。
The contact ceptors do not at all promote the expenditure of energy in the chase or in fight； in the search for food or for mates。 Since the distance ceptors control these activities； one would expect to find that they control also those organs whose function is the production of energizing internal secretions。 Over these organsthe thyroid； the adrenals； the hypophysisthe contact ceptors have no control。 Prolonged laboratory experimentation seems to prove this postulate。 According to our observations； no amount of physical trauma inflicted upon animals will cause hyperthyroidism or increased adrenalin in the blood； while fear and rage do produce hyperthyroidism and increased adrenalin （Fig。 44） （Cannon）。 This is a statement of far…reaching importance and is the key to an explanation of many chronic diseases diseases which are associated with the intense stimulation of the distance ceptors in human relations。
Stimuli of the contact ceptors differ from stimuli of the distance ceptors in still another important particular。 The adequacy of stimuli of the contact ceptors depends upon their number and intensity； while the adequacy of the stimuli of the distance ceptors depends upon the EXPERIENCE of the species and of the individual。 That is； according to phylogeny and ontogeny this or that sound； this or that smell； this or that sight； through association recapitulates the experience of the species and of the individual awakens the phylogenetic and ontogenetic memory。 In other words； sights； sounds； and odors are symbols which awaken phylogenetic association。 If a species has become adapted to make a specific response to a certain object； then that response will occur automatically in an individual of that species when he hears； sees； or smells that object。 Suppose； for example； that the shadow of a hawk were to fall simultaneously on the eyes of a bird； a rabbit； a cow； and a boy。 That shadow would at once activate the rabbit and the bird to an endeavor to escape； each in a specific manner according to its phylogenetic adaptation； the cow would be indifferent and neutral； while the boy； according to his personal experience or ontogeny； might remain neutral； might watch the flight of the hawk with interest or might try to shoot it。
Each phylogenetic and each ontogenetic experience by an indirect method develops its own mechanism of adaptation in the brain； and the brain threshold is raised or lowered to stimuli by the strength and frequency of repetition of the experience。 Thus through the innumerable symbols supplied by environment the distance ceptors drive this or that animal according to the type of brain pattern and the particular state of threshold which has been developed in that animal by its phylogenetic and ontogenetic experiences。 The brain pattern depends upon his phylogeny； the state of threshold upon his ontogeny。 Each BRAIN PATTERN is created by some particular element in the environment to which an adaptation has been made for the good of the species。 The _*state of threshold_ depends upon the effect made upon the individual by his personal contacts with that particular element in his environment。 The presence of that element produces in the individual an associative recall of the adaptation of his speciesthat is； the brain pattern developed by his phylogeny becomes energized to make a specific response。 The intensity of the response depends upon the state of threshold that is； upon the associative recall of the individual's own experiencehis ontogeny。
If the full history of the species and of the individual could be known in every detail； then every detail of that individual's conduct in health and disease could be predicted。 Reaction to environment is the basis of conduct； of moral standards； of manners and conventions； of work and play； of love and hate； of protection and murder； of governing and being governed； in fact； of all the reactions between human beingsof the entire web of life。 To quote Sherrington once more： 〃Environment drives the brain； the brain drives the various organs of the body。〃
By what means are these adaptations made？ What is the mechanism through which adequate responses are made to the stimuli received by the ceptors？ We postulate that in the brain there are innumerable patterns each the mechanism for the performance of a single kind of action； and that the brain…cells supply the energyelectric or otherwise by which the act is performed； that the energy stored in the brain…cells is in some unknown manner released by the force which activates the brain pattern； and that through an unknown property of these brain patterns each stimulus causes such a change that the next stimulus of the same kind passes with greater facility。
Each separate motor action presumably has its own mechanism brain patternwhich is activated by but one ceptor and by that ceptor only when physical force of a certain intensity and rate of motion is applied。 This is true both of the visible contacts affecting the nociceptors and of the invisible contacts by those intangible forces which affect the distance ceptors。 For example； each variation in speed of the light…producing waves of ether causes a specific reaction in the brain。 For one speed of ether waves the reaction is the perception of the color blue； for another； yellow； for another； violet。 Changes in the speed of air waves meet with specific response in the brain patterns tuned to receive impressions through the aural nerves； and so we distinguish differences in sound pitch。 If we can realize the infinite delicacy of the mechanisms adapted to these infinitesimal variations in the speed and intensity of invisible and intangible stimuli； it will not be difficult to conceive the variations of brain patterns which render possible the specific responses to the coarser contacts of visible environment。
Each brain pattern is adapted for but one type of motion； and so the specific stimuli of the innumerable ceptors play each upon its own brain pattern only。 In addition； each brain pattern can react to stimuli applied only within certain limits。 Too bright a light blinds； too loud a sound deafens。 No mechanism is adapted for waves of light above or below a certain rate of speed； although this range varies in different individuals and in different species according to the training of the individual and the need of the species。
We have already referred to the fact that there is no receptive mechanism adapted to the stimuli from the _x_…ray； from the high…speed bullet； from electricity。 So； too； there are innumerable forces in nature which can excite in man no adaptive response； since there exist in man no brain patterns tuned to their waves； as in the case of certain ethereal and radioactive forces。
On this mechanistic basis the emotions may be explained as activations of the entire motor mechanism for fighting； for escaping； for copulating。 The sight of an enemy stimulates in the brain those patterns formed by the previous experiences of the individual with that enemy； and also the experiences of the race whenever an enemy had to be met and overcome。 Each of these many brain patterns in turn activates that part of the body through which lies the path of its own adaptive response those parts including the special energizing or activating organs。 Laboratory experiments show that in an animal driven strongly by emotion the following changes may be seen： （1） A mobilization of the energy…giving compound in the brain…cells； evidenced by a primary increase of the Nissl substance and a later disappearance of this substance and the deterioration of the cells （Figs。 5 and 13）； （2） increased output of adrenalin （Cannon）； of thyroid secretion； of glycogen； and an increase of the power of oxidation in the muscles； （3） accelerated circulation and respiration with increased body temperature； （4） altered metabolism。 All these are adaptations to increase the motor efficiency of the mechanism。 In addition； we find an inhibition of the functio