L779L
 1839
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LECTURES
ON
PSYCHO-PHYSIOLOGY
BY
^MARTIK LITTLEJOHN, Ph. D., LL.'D., F. S. ge. & F..R. S. L. (Lond.)
/V
(P^r-
PROFESSOR OF
Physiology and Psyc.
■s.\
COPYRIGHT, 1899.

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AMERICAN SCHOOL OF OSTEOPATHY,
     Kirksville, Missouri.
     1899
WEEKLY ADVOCATE PRINT,
  KIRKSVILLE, MO-'.
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£ 
NLM 0055^33^4 7
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L-179L
)$ 53
ANHUJ
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U.S. NATIONAL
     LIBRARY
           OF
    MEDICINE
WASHINGTON, D.C
NLM005593347
9930 
 
 
PSYCHOLOGY  OB PSYCHO PHYSIOLOGY.
                           Introductory.
    We begin to-day a course in Psychology for the first time  in this  institu-
tion.  It marks an important departure in the curriculum of a medical school.
In very f rw medical schools in this country or elsewhere do we find this subject
dealt with.   And yet it is a most important branch of  knowledge.   Its intro-
duction marks   the recognition  of the unity of man in   his tripartite being of
body, soul and spirit.   If medicine—I use it in the wide  sense denned in the
beginning of physiology—professes to preserve the health and life of man and
to cure diseased conditions that threaten to destroy his health and life, then it
must recognize that the  materia medica of medical science must apply not alone
to purely bodily and material elements of life but also to that other and not less
important part of the human system,  the psychic  nature.  Recognizing that
Osteopathy wishes to be a perfect as well as an exact  science, we  introduce
into our curriculum the study of the mind, mental conditions  and operations
and mental phenomena  because these have  an important bearing upon  health
and the comfort of life.
    Modern psychology has been chiefly developed in  Great Britain and Ger-
many and the United States. There have been three lines  along which psychology
has developed, (1) along the empirical line, based upon so called experience. (2)
Speculative,  chiefly in Germany, originated by the philosophy  of Kant who
made  reason  the central element  in psychology.   His conception  of  reason
is centralized in the imperative of duty laid down by reason as the basis  of all
intellectual  and moral  development.  (3) Scientific, this represents the new
movement in  psychology which received  its first and main impetus from the
evolution school of philosophy.   English  psychology was mainly  an analytic
consideration of consciousness as its phenomena were  manifested in experience.
German  psychology before Herbart was mainly a psychological analysis of
speculative  conditions associated with  a semi-mythical  reason,  culminating
in Hegeliauism which represents the climax of speculation.  Kant discussed the
faculty of reason in regard to cognitions independent of experience.   Accord-
ing to Hegel self-consciousness is the ideal unity in reference to which the en-
tire world must be explained, thoughts like things being parts of a whole, stages
in a process,  in fact thought is that  process  itself.  Herbart,  whose work is
known to every scholar, wrought a revolution in German thinking  by setting
aside the speculative and introducing  that of experience, laying the foundation
for the union of English and German thought in the scientific school.   He rep-
resented that spirit of experimental research which has animated German phil-
VS b'b O   ~folA>r\  t "=f)^ q 
9
osophy during this century, himself  attempting to  build up  a psychology of
mind based  upon the mechanic  and static.  Thus,  to Germany belongs  the
honor of first treating the mind  from a true experimental  standpoint.
     In America, psychology has been controlled  up till quite  recently by  two
currents of thought, (1) the theological,  and (2) the educational.  After  the
struggle for existence had finally settled the political independence of America,
philosophy began  to assert itself  but it was in alliance with  theology.   For a
long time the Jonathan Edwards idea of the free  will dominated psychology as
it did theology.   At first the pedagogical influence was simply a help  to  theol-
ogy,  largely due to the  denominational activity  in education,  especially  the
Puritan conception of the close relation of   the  church and the school.   The
philosophy which these  conditions produced was one closely akin  to the Scot-
tish  school of realism.   This  was due to religious inflluence and  especially to
the prominent place occupied by Princeton  College,  two of  whose  presidents,
Witherspoon and McCosh,  were called to their position from Scotland.  This
realistic philosophy was that taught by Reid and  Hamilton in Scotland, the  ba-
sis of which was the observation  of  the facts of  consciousness.  By the a pos
tenori method a priori principles are discovered, observation taking in the field
of consciousness as well as that of sense and co-ordinating the  facts of  experi-
ence in both fields. Realism  as adopted in America led to the recognition of
mental reality, established consciousness, giving  to mind a realistic conception,
that  gave to consciousness a place almost equal to  deity.   It was  this that  led
up to the Hamiltonian idea of the absolute as the  unknown and the unknowable.
German philosophy then  made its way to America chiefly through the  writings
of Coleridge  and Emerson.  On  the religious side Channing,  and on the phil-
osophical side Emerson   laid the  foundations  of mental  activity deep in con-
sciousness.   "Mind is the only reality of which man and other natures are bet-
ter or worse reflectors."   The world is transferred into consciousness for "na-
ture, literature,  history are only subjective   phenomena."  All things  are be-
held in the mind, for they aTe  all  in the intellect.   He made the mind real  and
in this Emerson   was the precursor of  modern psychology.  He it was who
helped to free  psychology from  theology  and education and make it indepen-
dent.
     Since L880 psychology has been  separated  from  metaphysics,  theology
and  pedagogy and the  divorce has had  happy  effects so far as psychological
development is concerned.  After Herbart it  was  realized  that the facts in
the life of  consciousness were  of importance  aside from other questions of
being,  immortality and  education.  The Germans began to discuss the ques
tion  which Locke, Des Cartes  and Reid had anticipated, that of the relation ol
the mind and the brain.  It was asked  whether  brain and mind can be sub-
jected to modification.   The Germans concluoleiljbhat the modification of  the
brain led to the  modification of  the mjn^sA Here #Q$ji£?gNsaw the possibility of


                                       NEGATE
 
3
using the scientific  method, experiment, in researches into the mind.   It was
Lotze who first discussed this question in his "Medical Psychology" (1852)
by formulating the  experimental plan.   It was  Wundt  who first gave it de-
finite form, experimenting extensively and establishing definitely for all time
the relation of the .nind and the brain, a position he has ably defended in his
"Physiological Psychology"  (1874).  Fechner  shortly after Lotze gave pub-
licity to the methods of the new  science and the  results of extended experi-
ments in regard to  sensation  states, in  his "Elements  of  Psycho-physics"
(1860).  This represented  the  first great revolution in Psychology, namely,
giving to it a  definite basis in Physiology and preparing the way for its util-
ization in the  field  of  medical  education and practice.  The entire basis of
psychology is changed  so that now it is  entitled to the term scientific.   The
second great revoluion  in the psychological  field came from England,  tiie
home of the evolution philosophy where Spencer gave to it a new trend in his
psychological works.
     Both of these currents have been  adopted in America.  Just as in the
peopling of America from an ethnic standpoint  it represents the blending of
the best elements of Europe,  so in the  psychological field we find these two
lines of revolution  clearly set forth.   The psychology of  America to-day  as
compared with the  older psychology up  to ten years ago may be briefly sum-
marized under f\vo  particulars:  (1)  It  is functional, that is, psychology re-
gards mental functions rather  than the older mental faculties.  (2) Under the
influence of evolution these functions of the mind are regarded as developed
and  developing rather than as formerly, existing ready  made.  Instead of con-
sciousness being intuitive the functions of the mind develop. So long as every
mental operation  was  regarded as a mental faculty,  each faculty was inde-
pendent of every  other, so that under the old  system  memory was a faculty
or power of the mind;   so was  thought, imagination, etc.  Now the mind is
regarded as  a unit and  it  is  looked  upon as acting in this unit capacity,
adapting itself to functional action in  adaptation  to the materials before it.
The  mind is one.   Mental action is a psycho-physical  or physiological pro-
cess.  There are no longer divided and  distinct  faculties,  for the mind is  un-
divided and indivisible, but the single mind has several functions in connec-
tion  with its adaptation to varying conditions under which it acts. The mind
has in addition developed to its present  condition, both  from childhood to
maturity in the individual sense and from the lower to the higher in the scale
of civilization  among  conscious  and thinking beings.   To understand mental
facts, both  of  these points of view must be kept constantly in view.   It is to
Lotze that this standpoint of psychology is  traced  back, because he was the
first to speak of "the  nervous conditions of the mental processes."  Fechner
carried out this idea by correlating the  functional idea in both psychological
and  physiological application.  Wundt elaborated these ideas in application 
4
 to the mental phenomena and founded the psychological laboratory at Leipzig
 in 1879 for the investigation experimentally of these phenomena.
     In America the  evolution philosophy was introduced mainly through the
 works of Spencer.  Fiske  was one of the first and ablest expounders of evo-
 lution, taking the view that the cosmic process forms  the basis of man's in-
 tellectual, moral and religious being, preferring, however, Weissmann's idea
 of selection and  preformation  to the environment and epigenesis of Spencer.
 The American  School of  Biology assisted in this, led by Edward Cope, ac-
 cording to which  all the modified forms of animal life are to be explained on
 the principle of growth and by the hereditary effects of habit and effort, there
 being a development force that controls the line of development.  This gives
 to the psychical, represented in the universal animal desire and effort to live,
 a priority over the purely physical.   Among the foremost leaders and one ot
 the  most original of American thinkers is George T. Ladd.   He made the
 first researches  and  gave  the first lectures on experimental and physiological
 psychology  in America.   According to him  the science  of mental life forms
 the only possible explanation  of every problem in life.  Associated with this
 new psychology  are Cattel, Baldwin and Sanford, whose work in the labora-
 tory has given  to pyschology an entirely new form which we will discuss in
 the lectures that  follow.
     The line of division in modern psychology arises in connection with the mean-
 ing of mental function, one side claiming that it is simply a form of the cosmic
 process and the other that it is analogous  to the play of forces in the  physical
 world.  In the solution of  this  and other questions of psychology  the physiol-
 ogist has as much to say  in reference to them as the psychologist.  One of the
 prominent ideas is that of  measurement applied to the mind so far as the de-
 termination of time and quantity is concerned.  Of  course this implies experi-
 ments upon  the nervous system  and the changes which are involved in con-
 sciousness. DesCartes long ago tried  experiments in connection with  the emo-
 tions to prove  the fact that the  mind can be  approached  through the body.
 But this  was impossible  until physiology had opened  up the nervous system
 and its connections with the mind through the brain.  Following  on  this ad-
 vance made in the physiology of the nervous system psychology presumes, (1)
 that  the mental  phenomena  are always accompanied by  nervous changes of
 some kind.  The relation of mind and body depends  upon  this presupposition.
 The   physical and the  mental changes  are interpreted  by   results,  and
 these  changes    always   go   hand   in   hand.    (2)    This    established
 relation between  mind  and  body is presumed to  be  uniform, thus fur-
 nishing a basis upon  which to  conduct experiments in reference to the mental
 life.   Having established this relation and presupposing its  uniformity we can
 analyze the  facts of  consciousness,  measure the  facts in  relation to nervous
changes,  notice the modifications which  are found in the facts of conscious- 
ness correlative with the change in nervous stimulation.  By the use of exper-
iment we can  discover the difference  between natural and arbitrary conditions
according as we find the  nervous modification due to stimulation of the nervous
system externally or  subject to abnormal conditions of the  organism.   Here
we come to  those diseased conditions of the nervous system  characteristic of
certain ci rebral conditions, mental changes  accompanying  organic  nervous
changes.  It is here that mental  diseases come up for consideration.  This is
physiological psychology  and pathology.  Experimental  psychology  presents
the results of experiments  in connection with the stimulation of  those organs
that affect the nervous system as the medium of mental activity, whether these
refer to the  normal  or abnormal conditions of the mind and the nervous system.
This term we will discuss  psycho-physiology and next term  psycho-pathology
and psychiatry.
     In order to understand psychology  we must dig deep  into biology and to
follow out the subject fully we  must investigate physiology,  neurology, physics
and  chemistry.     The method that  we adopt is observation aided  by experi-
ments.   Hence we  hope   to find and build up  a science consisting  of definite
principles and considering definite problems.  It finds its basis or field in the
human body,  particularly the  nervous system.  Action  impresses the brain
through  the organs of sense.  The impulses  are executed through the  motor
apparatus in connection  with the muscles and bones.   Psychology  lays down
two axioms,(l) that every mental phenomenon is based upon some brain activ-
ity ;  (2)  the mind does not possess by nature  any perception of number,  quali-
ty or space.   No  appreciation of these exists  coeval with mental  existence but
all perceptions,  apprehensions and  discriminations  mark the mental growth.
The brain develops  and  so does the mind,  both of these developments  being
inseparably  connected.   To understand  the present mental status we  must f( 1-
low its genetic progress from the simplest form.   We must  study this growth
in order to reach the laws of mental  development, these lawt  representing the
mental progress which is in harmony  with  all nature's  evolution.   From tl e
animal upward we find this progessive development.   The instinct of the chi< k
exhibits itself  on the 3d  day of life so  that instinctively the chick will  follow
after any moving object and  thereafter adhere to  its leader no matter who,
everv other  moving object creating a  feeling of anxiety  and producing fear.
If this period of instructive development is suppressed or allowed to pass by it
will never thereafter  be  developed.   This is an  important   psychic principle,
that there is an order and a period  for the proper development of  psychic na-
ture.  In man  we find a  greater number of instincts  than in any  other animal
and these all develop in their proper order.   These instincts and the  emotions
associated  with them  represent  the  most  powerful  of nature's  influences.
There are various types of human thinking and association.   People think and
form memory  mental pictures in different ways, the type being individual,  the 
6
capacity generic.  This is illustrated in the methods of visual observation, the
forms of vocal utterance and the manner of audition.  Some  people visualize,
others vocalize, while others embody in auditory expressions all their thoughts.
These represent  the three types of mental embodiment in the  activity of the
mind.  This seems to rest on the basis of  imitation which is as much instinct-
ive in man as in the lower animals. In order to imitate there must be formed in
the mind a definite conceptand there mustbepowe/ to carry out the concept. The
mind thus formulates and through the medium of the brain,  the nervous  sys-
tem and the body, executes its plans.
    In another direction we find the same  idea of the connection  of  brain  and
mind, viz., in.speech.  In the brain we find two lobes,  each lobe  governing the
opposite half  of the body.  The right  hand is controlled by  the left part of the
brain.   In the left part of  the  brain  we find the speech center,  close to the
hand region.  Anthropology and primitive  philology have proved  that the lan-
guage of the hand or sign language existed prior to vocal  language.  In  hand
language the  right hand   is the prominent instrument.  In line  with  this we
find that right handedness and speech are  not found in the animals  lower than
man.
    In line with this  animal brain development  is normal  and there is no
variation  in  one lobe  as compared with another.  This indicates that the
speech organs; the prominent use of  the right hand and what they represent
brain centers in the same region and lobe of the brain have an  intimate rela-
tion to one another.  The question of whether this relationship is natural or
acquired  and  therefore a hereditary acquisition has  been much discussed in
the light of   development  as applied to  the mind and the brain.   This indi-
cates at least that for mind and mental activity we have a solid and definite
basis in the  human brain and  that there exists a close relation between the
mind and the body, both of  them developing and in their development being
inter-dependent and influencing each  other.
    It is that makes psycholgy of value in  the medical field.  In the  past
physiology and medicine have gone on the assumption that the  body is some-
thing quite distinct from the mind.   Psychology  had the same  view of the
mind.   Modern  psychology and physiology  regard  man as a  unity in  mind
and body, body being the  instrument and  medium of mental manifestation,
so that one of the first essentials of health is a mind and consciousness deter-
mining the body condition.   While the body is a machine,  it is  not a machine
that is wound up and capable of going for a  number of years wholly under
external  influence.   The moulding and  shaping of  the  body proceed from
within.   Mental function is at the basis  of every physical function.  Behind
the physical acts  involved in digestion, respiration  and  circulation there is
the mental state which determines the body  condition.  It is a  notorious fact
thut civilization has increased disease and body weakness.   This is due to the 
 fact that along with  civilization  conies a  mental  excitement that is not con-
 ducive of body health.  There is  involved a higher mental effort,  a greater
 struggle for existence which cause the normal development of mind  and body
 to be lost sight of and involve the bcdy in numberless disturbed conditio us
 and diseases.  We do  not  raise the cry, back to savagery; but we do s:iy,
 back to that condition which it represents on a low plane, viz.:  The absence
 of those mental  disturbing conditions which create bodily wrecks,  intensify
 nervous disorders and bring  on disease and death.  Recognizing the  osteo-
 pathic principle  that drugs  are unnatural and that all nature's remedies  are
 stored up in  the human system, we have this psychic law of the mind's as-
 cendancy and to carry it  out  in the removal of these diseased conditions,  the
 beginning must  be made within.   The adjustment must be made by  the mi::d
 and the mental condition must first be adjusted to the  body  conditions of
" perfect health.   The  only prescription that can be given  is to  cultivate and
 perpetuate  mental equilibrium.  Sudden emotions wre know affect the  circu-
 lation, the  heart rhythm,  the respiration, destroy the secretions, impair di-
 gestion and even cause death.  If such  emotions become  chronic how is it
 possible to  have  a perfect nutrition of the system.  Physiological chemistry
 has demonstrated that such a chronic condition produces toxic substances
 that interfere with every normal body process.   So long as these exist health
 is impossible,  and there cannot be physical immunity from disease, because
 the system  is laid open to all kinds of germicides.   Such conditions whether
 inherited or acquired  form the basis of  all kinds of disease and weakness,
 both physical and mental.  Ill health from this  standpoint intrudes upon a
 physical and mental being  that ought  to be immune and that can be so only
 when it is well balanced  and calm.  To heal the mind and  give it that  place
 of appointed vantage  in the human system, which instead of depressing will
 elevate, instead of wearing out will  tone up and instead of laying, open will
 raise above all sorts of  disease ravages, the human body, such is the design
 that psychology has in entering the field of medicine.
     Psychology in its modern form is largely indebted to other scien ces.  Just
 as physiology was revolutionized  when explained in the light of  physical and
 chemical processes, so psychology is indebted to physiology, physics  and even
 astronomv.   Helmholtz  nearly half a  century  ago  measured  the speed the
 of nerve  impulses.  But  the  peripheral  nerves represeut only a part of the
 nervous svstem,  the brain representing the  special  medium  of mental mani-
 festation. Associated  with the mental activity there are certain brain processes
 and as the individual knows his experience  in connection with certain stimuli,
 stimulation  has been applied to different parts of the  body  with the result that
 the time necessary for a response  in  muscular action  could  be measured.
 Closely connected with these investigations have been the  researches into the
 nerve functions in connection with the  nerve terminal organs, so that the sen- 
s
 sory functions are  clearly understood  in their relations  to mental actions.
 Kvery experience is based upon some physical basis and here physics demon-
 strates the possibility of connecting sensation, emotion and volition with such
 external  objects  as  are subject to physical laws.   These  physical sciences
 have thus opened the way  for psychic  consideration of the mind from the
 physiological standpoint.   Psychology  begins with the  nervous system, es-
 tablishing correlations between the mind and the brain and  opening the way
 for observing psychological  laws.  The brain requires  to be differentiated,
 the nervous paths must be traced and the molecular action and interaction of
 the nervous  elements  must be definitely known.   The study  of the central
 nervous system is of great importance because here only can psychology find
 its perfection.
    Plato considered  that Deity formed sublimary creatures from the devine
 nature, these sublimary beings  creating the animal body and imparting to it
 this divine part as  the  immortal element.   In the soul we  find,  according to
 him, spirit the seat of  intelligence; the animal and material part, the seat of
 passion,  including courage and also the  seat of appetite.   The spirit was
 localized in the brain  passion in the heart and  appetites including desires in
 the lower body parts.   In Aristotle  we find the psychic operations classified
 as imagination, judgment  and sensation, the heart being with him the mental
 seat, the brain  acting the part of a  heart cooler.   Erasistratus was the first
 to identify the nervous system as a definite system ascribing to it the function
 of  mental phenomena.   Regarding the  air as the vital force,  he traced its
 passage into the lungs through the heart  and  then to the  brain where it be-
 came vital spirit  or animal  spirit.   In this way the mind and the body were
 closely connected,  mental phenomena being  inseparably  related to nervous
 functions.  Galen  by the  discovery  of the fact that the blood was the essen-
 tial of life said that the animal spirit must be in the blood.   Yet he regarded
 the brain  as the  principal nerve structure, the seat of volition and sensation,
 the purely physical body system in its muscular  mechanism being entirely
 dependent upon the nervous system.  This  marks the acquisition of knowl-
 edge until comparatively  recent times.   Willis in England is entitled to the
 honor of presenting more  than 200 years ago the genesis  of the modern ideas.
 The brain he regards  as the seat of  the human soul, the principal  mover is
 the animal mechanism,  the source of all motion and conception.  The brain
 convolutions he regarded  as cells or  storehouses which mark the limitations
 of the motions of animal spirit, the cortex being the seat  cf ideas and the cen-
 tral organ of motion and conception.   Newton,  from the  physical standpoint
 supplemented this discovery by declaring that the impulses are  propagated
along the  nerve paths as vibrations.   Added to this is the fact  hinted at by
 Willis  that the nervous system is the basis  of  reflex action and that this ad-
dition to neurology in regard to the differentiation and  localization of  func- 
9
tion due to the researches of men from Bell to Ferrier in these we have the ba-
sis of psychological  action in connection  witth  the brain and the  nervous
system.   Gradually in history we have reached our present knowledge.
    While the nervous system is the basis as well  as the medium of the men-
tal operations, we must not forget that the higher field of psycho-physiology
the mind is the ascendant power and that in a healthy physiological life noth-
ing less  than a healthy  mind can  secure that  vigorous condition  of body
which is so much desired by all, health and the comfort of  lile, happiness.
The physiologists  have largely limited their investigations  to the separate
parts of  the central nervous system without  attempting  to formulate any
plans of systematic  action on the  part of the  system as a whole.  This has
produced in physiology a tendency  to over estimate the importance  of spec-
ialization of function, overlooking the fact that there is a solidarity and unity
of action on the part of the entire system.   It is probable that  every active
operation of the nervous system affects the whole human system;  in this way
there must be constant activity on the part of the nerve cells accompanied by
continual impulses entering and  leaving  the cells. This forms the  basis of
"the continuity of  conscious experience."  Behind consciousness, at least,
from a morphological  standpoint  there lies  the anatomical  structure of the
nervous system; but as yet no one has been able to solve the problem of their
relations.  The region of consciousness has been gradually moving  upwards
with the development of physiological theories until, as one  physiologist has
said, it  has had to take refuge in the only  remaining region after the sensory
and motor areas have been localized, namely,  in the anterior portion of the
gray matter Df the cortex.
    Ancient philosophers  did not  limit  the mind to the brain.   With the
dawn of the modern Psychology the center  of conscious mental,  emotional
and volitional  phenomena was associated  with the medulla,  in  more recent
times to  be localized in the frontal area  of the cortex, largely  because this  is
the only portion of the brain  left for its  localization.  Even if we could under-
stand all the changes taking place in this region we should be unable to  bridge
the chasm oetween the purely subjective  and the objective; much less would we
be able to resolve mental phenomena into their  preceding causes.   Physiology
has divided mainly  into  two schools,  the  one materializing the mental phe-
nomena by  ascribing  them  solely to  physiological and   physical  causes and
the other idealizing them  by calling them figurative names which in reality give
no explanation  of the phenomena themselves.  By the combination of both of
these  ideas we have a  fundamental, physical  and physiological basis for the
ideal  interpretation of these  phenomena.   If we enter  into the realm of the
transcendental  and premise the existence behind all these phenomena, whether
physical  or mental, of metaphysical essence,  then an  explanation becomes
more clear, because  these phenomena of mind and body became  simply mani- 
LO
testations of this inner, deeper and truer existence.  The difficulty in this case
is that such an essence which metaphysics would identify with soul  cannot be
proven in any possible way by science.  At best it is  simply a  metaphysical
conception.
    Without attempting to solve this question there is an important  physiolog-
cal  question, whether physiology has any ground  for localizing consciousness
and the entire psychic phenomena in the frontal area of  the brain.   If we  can
interpret aright  the facts of comparative  physiologists then  this theory  is not
founded upon  fact.  Physiologists localize in the brain sensation, that is, here
terminate all those impulses which result in consciousness.   Yet the other por-
tions of the nervous system which convey  the impulses to  this sensonum may-
have as much  to do with  consciousness as does the sensorium itself.  In  the
lower animals  whose brain development is very simple, possessing none of the
characteristic cortical convolutions associated with  mental phenomena in  man,
we find consciousness.  This view ie based upon the perfect unity of the body
and especially of the nervous system   It gets over the difficulty which modern
physiology emphasizes of perfect localization of the different functions.
    In the earliest conditions associated with cell development we find the sin-
gle  cell subject  to stimulation, undergoing  certain molecular changes,  these
changes sending  out impulses to other cells and also along nerve paths to  the
surface of the body.   If the first cell which  is more  or less differentiated in
in function by reason of the capacity of receiving   and transmitting impulses
becomes  more fully specialized, by continued  stimulation so  that its changes
are  accommodated to this special kind of  stimulation and respond to such ex-
ternal stimuli as it has become accustomed to have, we have the first beginnings
of consciousness and also  of  memory.   Consciousness even  here  is not the
product of the changes that take place in the cells,because even a knowledge of
all the internal changes would not involve consciousness, as the  consciousness
would only arise in connection with some external  manifestations. Some  have
explained this by assuming that there is associated with matter a consciousness ;
but  this cannot be, because we find no connection line between physical matter
and psychic consciousness.  Therefore we find two seeming  opposites  neither
of which   is the cause of or is caused by the other,  this connection has  been
completed by some who have  identified energy of some kind with the causation
of consciousness.  Energy, however, is a physical  attribute in  virtue of which
certain matter or matters  possess  the power of  acting, this action   depending
upon the  active  changes  taking place in  the  constituent  elements.  If these
changes which we suppose to  take place in the cells upon the basis  of  molecu-
lar activity form the basis of consciousness, then consciousness must be  a  ma-
terial and  not a psychic  quality because the result  cannot contain more  than is
found in  the cause.  The  simple substance-changes or matter-movements can-
not  therefore explain consciousness. 
11
     Consciousness is therefore inexplicable unless we hypothecate the psychic
as we do the physiological, each one in its own sphere forming the basis of  its
own characteristic activity.   If we  consider the nervous system as  consisting
of a complexity of nervous  mechanisms, each mechanism  in its oimple form
constituting an activity in which there is consciousness, then the entire ner-
vous system would represent a complex  series  of conscious  states from the psy-
chic standpoint.  Consciousness must exist then not only  in the case of  the
entire brain but in all the cells that constitute the complex brain.   If stimula-
tion is applied to a sensory part of the body an impression is  carried into  the
central nervous system, a reflex movement of some  kind resulting.   There is
here a reflex action which  has no volition, at least from the  brain center and
yet there is a consciousness of the  changes taking place in connection  with the
reception and distribution  of the impulses.  The center of reflex action outside
of the brain has a close connection with the cells in the gray matter of the brain
so that every senbory area  of the body  has  a connection with some portion of
the brain.  Impressions may pass outward reflexly  from these cerebral centers
to other centers  resulting  in involuntary movements,  but impulses may also
pass from these  sensory centers  in  the cortex to  the centers of volitional  im-
pulses resulting in voluntary  movements.  Every  voluntary action in however
essentially  a reflex action depending upon afferent stimulation either at the time
when the action is called forth or at some prior period.
     The impressions made upon the cells or combinations of cells are retained
thus constituting memory so that, when the impulses are aroused, volition has
a basis upon which to act.   If we  add  to this the fact that  by means of vision
when an image is  formed  upon the  retina the optic nerve transmits it  to the
corpora quadrigemina where  co-ordination takes place from whence it is car-
ried to the  optic  region in the cortex.   This  image  when  impressed upon the
cell constitutes a memory picture,  which under the influence of impulses, may
be awakened in consciousness so as  to call forth activity.   These sensory im-
pressions may, however, not only be aroused to consciousness in the  cerebrum,
but also in  the cerebellum,  where co-ordination takes place.   It is probable that
sensory regions are  found both in the cerebrum and cerebellum.  If this is so
then the convolutions of the  cerebrum and the cerebellum represent, the latter
the seat of regular  rhythmic movements  that are not dependent upon volition,
whereas the former represents the voluntary element in all movements.   When
different sensations are produced by the action of an  object or objects as stimuli
upon different  parts  Of the  sensory surface, molecular  changes are  set up  in
different cortical regions,  these regions being connected together by the fibers
of association so that when consciousness receives these different impressions
they are combined to form a single  idea.  Instead of  being combined,  how-
ever  in the mental  picture ; these combined impulses may give rise  to muscle
movements, the  movements depending-largely upon the stimulating causes. 
 12

 When the stimuli are strong the impulses  pass to the nerve cells  in the  bram
 where, on  account of their strength, they  make a  vivid impression upon the
 cells so that after the stimulation has passed away  the  impression  continues,
 being subject to recall upon a slight stimulation either external or internal.
     Here we have the  physiological basis of  the association of  ideas  which
 occupies such a prominent place in  psychology and also the basis  of memory
 and recollection.  By the constant  repetition of  these processes the impres-
 sions become so closely associated  with  the  cell  body that they form an in-
 herent part of the cell  life so that by heredity these are transmitted from gen-
 eration to generation  forming  the  physiological  basis of mental  intuitions.
 These intuitions  represent modifications of the brain  under the influence of
 mental development,  each  brain  representing  its  own stage of progress in
 evolution.  Where we have a great number and variety of impressions we find
 great variation in the cell changes and a corresponding variety in  the mental
 phenomena.  When   these impressions are  so fixed in the brain that  a stimulus
 from another part of the brain  can call forth a  response, we have  a fully de-
 veloped mental condition.  In this way the pictures of scenes seen by the sense
 of vision or objects  brought into contact with the sense of touch may be  stored
 up within the brain cells to be awakened at the call of some mental stimulus.
     Some physiologists  say that they  may be aroused spontaneously.   This,
 however, is probably incorrect as what seems to be spontaneous awakenings
 are dependent upon   weak stimulation, often indirect.   The sight of an  object
 may arouse impressions  formerly associated with such an object or with one
 analogous  to it, the   simple call being  sufficient  to  arouse dormant impres-
 sions.  In  this  way we find that phenomena which at first seem purely  vol-
 untary and arbitrary become purely reflex  or at least cease to be associated
 with conscious  volition.   In  the case of  the  child  persistency of  effort en-
 ables it voluntarily to walk.  After childhood  these movements  may be  quite
 unconsciously  performed.  In the same way mental  phenomena may become
 purely unconscious,  so much  so that  certain actions are often spoken  of as
 Uing done instinctively.
       It is generally conceded  that  there may be unconscious mental activity,
 the result  of this mental  action  later becoming  conscious.  Mental develop-
 ment implies the receptive condition  of  the nerve  cells and  also  the  active
 operation  of  these cells in the  changes involved in  molecular  development.
 These are  regulated somewhat  by the capacity  of  selection in the case  of
 different impressions, by  the  concentration   upon particular  impressions to
 the exclusion of  others,  by the  activity  of  the cells  in connection with the
particular impressions and the  power  of  associating these  impressions.   Each
 of these elements has a physiological basis  in the central nervous  system,  and
 they  may become  more stable by  discipline,  the brain development depend-
ing largely upon the proper exercise  of it.  This implies that individuals differ 
13
 from each other in the original constitution  of their nervous system this  form-
 ing the basis of different degrees of  intelligence and psychic  initiatives as  we
 find these among different individuals.   These,  however, are based primarily
 upon hereditary acquisition handed down  along with the system itself from
 ancestors.
     Thus to each one is  given by birth not only a body but also a mind, the
 basis of mental character and development.  When man starts out from this
 initial point in his mental history his development is determined largely by
 environing conditions and  educative processes.   The power of volition may
 also be increased  by exercise so that the  inhibitory power  depends largely
 upon these same educative influences. It is this that  we mean when we speak
 of the mind as being a unit, consisting of certain operative functions  which
 mark the stage of mental development, capacity for still further development
 being the characteristic of every normal mind.
     Method.—As we have said physiology and psychology are combined so that
 the  method must  be of a dual nature.  Physiology represents the means to be
 used in building up the psychic science, in other words it is psychology with the
 physiological method.   The older definition  of psychology referred to it as  the
 science of the human soul.  Some make it more specific by way of limiting the soul
 to the subjective spirit;  as Erdmann does, only by claiming that it is the basis of
 the spiritual life.   Here we are taking for granted the existence of a metaphyis-
 cal entity,  whereas we have no means of establishing its existence.   We realize
 that it is  difficult  to define a science, particularly a  new science, so that we
 must not make the mistake of adopting an  ideal  definition and  then trying  to
 bring the facts up to our definition.   Psychology, therefore, we  shall describe
 rather than define, as that branch of science  which investigates from  a psycho-
 physiological standpoint  by physiological 'methods the phenomena  of human
 consciousness.   Here we have data that cannot be defined, namely, conscious-
 ness and its phenomena.
     If we understand phenomena aright we may give them the technical name
 psychoses or conscious states.  Experience alone can  discover these phenom-
 ena ; hence to describe these phenomena  as  they are, to  attempt  to  discover
 their relations,  how the phenomena came to  exist and to be associated with one
 another, is the  subject  matter  of our present investigation.  Phenomena,  of
 course,  imply  something  primal  behind.   Hence we cannot investigate the
 phenomena without implying  the existence  of a  sentient being who can say
 Ego or I.   What is this Ego?  In the abstract we say he is soul, but he practi-
cally exists and feels in  body.   To man, however, pure materialism  is  an impos-
sibility, for there is only one real world,  the world of thought.   Thinking and
thought create their own environments.  It is fiom the subjective standpoint
that man establishes his objective relations, so that matter whether taken  from
the vegetable or animal scale becomes moulded after  the  soul likeness and by 
14
 the soul power of the person himself.   In this way by the  constructive power
 of  experience man establishes to himself his personal identity,  the recollection
 of  this personal equation of being forming the connecting link in his ever vary-
 ing life experiences.   This  leads man  inferentially to conclude  that  there is a
 subject within which  underlies  all  the  phenomena of  consciousness.  In this
 light man regards his experiences as his own, his responsibility as  his own and
 not another's, and that this identity or ownness belongs to himself  and contin-
 ues the same from day to day.  Hence the word mind  or  soul is  used in this
 sense as identical with the subject  of  conscious  phenomena.   We   prefer the
 word mind because it is in a sense free from the prejudices associated with soul
 and it has no particularly embarrassing relations with the social or religious life.
 According to this physiological psychology is the science  of  the  human mind
 investigated from the standpoint of its physical and physiological relations.
     Physiology is the science that deals with the  functions  of  life as we find
 life embodied in the physical organism.   In  psychology we deal with the  phe-
 nomena of consciousness  as these are manifested in connection with  the  nerv-
 ous mechanism and also in  connection with  body movements and actions,  so
 that we must deal with relations and correlations established between the struc-
 ture and functions of  the nervous system  and the bod}? mechanism and the
 phenomena of consciousness.  The nervous system is regarded as a mechanism
 which has intimate relations with,  and through  these relations controls the
 entire body system.   Psychology takes the physiology of  the nervous mechan-
 ism in its origin and  structure, consisting of material  particles, subject to in-
 ternal stimulation in connection with adjacent  particles and  also  to external
 stimulation in connection with external forms.  There is thus the action and in-
 teraction of molecules constituting the living substance and representing defiuite
 relations and influences.  These  influences  and relations represent  not only
 physiological functions but also psychic phenomena.
     In regard to the method  we have said that it must be  dual.  In the blend-
 ing of two sciences both scientific methods  must be adopted.  Introspection is
 ihe only method that  can  be used in connection with consciousness and its phe-
 nomena.  Observation and experiment represent  the physiological  method  in
 dealing with structure, functions and development.   As there are thus two sets
 of facts to be dealt with the two methods must be followed.  The only scientific
 procedure is that of building up a science from  particular facts or the  use  of
 the inductive method.   Hence we must discuss and discover (1) the  phenom-
 ena that are associated with consciousness; (2)  attempt to bring these into cer-
 tain definite relations and associations so as to find out the laws that govern the
 production of the phenomena;  and (3) rise from  the phenomena and the prin-
 ciples regulating their relations to  the nature of  the thinking subject which
 underlies the phenomena.  Here the method is dual because  there are two sets
of phenomena and the laws regulating  the two sets of  phenomena are—if not 
15
 different have at least different applications to the physical and psychical—of a
 different order, the one being subject to the necessity of material conditions and
 the other regulated by a free mind.  Here it is that we must establish, not rela-
 tions, but correlations between the two orders  of  phenomena by bringing them
 together and discovering wherein lies the secret of  harmonious correlation  be-
 tween the physical and psychic.   We have accomplished this we have a psycho-
 physical  basis on which to rest the mind and a psycho-physical standpoint from
 which to  discuss the nature of  the mind  itself, its  origin and destiny and  its
 claims to be a permanent existence.
     As science is knowledge and scientific method the  most rational means of
 acquiring that knowledge, there can be nothing secret or mysterious.   Juvenal
 says, '-from  heaven  the precept  was sent, know thyself."  Consciousness
 and conscious methods are rationally used to find the primal facts of conscious
 life, to analyze these facts into their factors, and to trace their development from
 the simple to the complex as well as their  connections, never losing sight of  the
 initial fact that man is a living  unity.   Man  is not a  disembodied spirit or a
 mindless mechanism  of material  particles.   The introspective method of con-
 sciousness is  ^looking  into one's  own mind."  Herbart  has  objected to this
 method that in looking at these phenomena the facts themselves are torn from
 their necessary relations and become  abstractions.  According to Comte  the
 mind is both  subject observing and subject  observed, each tending to annihi-
 late the other, because to observe one's  self activity must  cease, and here you
 obliterate what you wish to observe.   These, however, forget  that  in modern
 psychology the nervous system represents the condition  and the medium of men-
 tal activity, so that in observing phenomena we are observing  how the mental
 life expresses itself or bow the mental  phenomena "graft  J.hemselves upon the
 more general  manifestations of  physical life."  Introspection  does introduce
 error iuto the observation, but all observation  does the same thing.   If I wish
 to concentrate my observation upon one fact I must withdraw it from its neces-
 sary relations, and in  abstraction I observe it.  This would be true of any
 observation.
    Brain and mind are not  exactly identical.   Mental phenomena and  bram,
 or at least nervous changes, may be correlative, but an idea cannot be explained
 by simply analyzing the brain or nervous changes that  accompany it.  We can
 never resolve  mental states into brain conditions, however close the relations be-
 tween them  may be.  In other words, brain functions may correspond to mental
 operations, but they cannot be identified.  We find a psycho-physical parallelism.
 "Mental life is a chain  of events parallel to another chain  of physical eveLts."
 It is claimed by some that  the mental phenomena are too complicated to find a
parallel in the neural mechanism.   If this parallelism is of any value it must be
complete, and it must be complete  in the development of both,  from the  orio-in
to the close.   If these are psychic processes, which are  not dependent  upon  or 
16
correlative to neural processes, then these belong to the field of  metaphysics.
So far as we are concerned the mind is viewed from the standpoint that it has
a physical basis and that the phenomena of consciousness would be non-existent
for us if such a physical  basis  did not exist.
    Consciousness.—Before entering upon the main discussion of the subject
we must  make  a  preliminary study of consciousness.   In the stream of con-
sciousness  that  is marked by phenomena  there is  the  unity of  mind.  Tnis
unity, however, must not be pressed too far.   Every mental phenomenon is  at
the same time associated with three mental processes associated withintellect,feel-
mg and conation, these forming the basis of the triune mental nature. As these
represent  the elementary psychic activities  they must  he  at  the foundation  of
all mental activity,  the more complex processes being simply the result of the
combination of these elementary processes under the influence of  development.
While this is true there must be some general  term  applicable to  all  the phe-
nomena.  Hence we call them  the phenomena of consciousness.
    Consciousness  is almost impossible of definition.  It is  impossible to con-
ceive of unconsciousness  in regard  to  the mental life, for from the psychic
standpoint it is  a  negative idea.  Complete  unconsciousness  would be the
absence of mental states  or processes.   It is possible that the mind  is capable
of certain  metaphysical processes that are above consciousness, but these states
are beyond the psychic phenomena.   Hence from the  psychic  standpoint un-
consciousness is entirely negative.   The mental life is conceived as a stream  of
consciousness, in other words,  the life of the mind has no points of separation,
marking off definite boundaries, as we find in the case of objects in space.   In
addition to this in the mental  life no  lines can  be set up as  separating one
period from another so far as  the processes are concerned. The life is continu-
ous without any breaks that are absolutely complete between  the mental pro-
cesses.  Neither is  consciousness to be  regarded as ever  simply in  a passive
condition, for the simplest mental condition is tnat of activity.  The varying
mental processes must themselves be subjected to mental activity before they
ean be recognized.  An unrecognized condition  has no  psychic  meaning,  for
example, a prick with a pin that is not discriminated as such represents a physi-
ological, not a psychological phenomenon.   Ladd has defined consciousness  as
"synonymous with psychical  state, regarded as discriminated, however faintly.
in respect of content and related, however  imperfectly, to the stream of mental
life."   The phenomena  of consciousness represent  mental activities.  To  be
conscious is to be conscious of this psychic activity, consciousness  being con-
sidered  "as a form  of functioning."   To analyze the mental states implies that
consciousness discriminates, and to discriminate conscious  states involves the
activity of the  mind, which  is itself consciousness.   Hence consciousness is
the recognition of mental activity from the standpoint of psychic unitv in rela-
tion to the conscious states.  Some identify it with self-consciousness as "the
power by  which the soul knows its own  acts and states.'"  (Porter.) 
17
    The German psychologists  argue against  this theory, because they say
every psychic phnomenon does not involve this self-knowledge. Both of these
views are extreme, for while consciousness is associated with all the psychic
phenomena,  there can be no knowledge of these without a  more or less dis-
tinct self-consciousness.   Self-consciousness arises whenever the subject rec-
ognizes that the psychic states are related to  one another and  to conscious-
ness.   Consciousness involves the  physiological basis found in the nervous
mechanism consisting of the central system, the nerve  paths and the terminal
organs.  Upon these in a healthy condition involving the proper nutrition of
the brain and nerve paths depends the functional activity of the conscious life.
Consciousness  is not limited to a single  fact at one time as there is always
involved in it a group of facts or objects.   Consciousness varies considerably
in different individuals from the standpoint of intensity and even the rapidity
of the mental  processes.   These can only be understood in the light of  con-
scious development.  In the child there is no self consciousness and no con-
sciousness of facts or objects such as we find in the matured individual.  The
mind is undoubtedly the same in both stages but by development the power
of discrimination has been so minutely refined by the processes of mental activ-
ity, in comparison and contrast, that the conscious knowledge has been great-
ly enlarged.  To be conscious then is to live a mental life, this mental life de-
veloping  as the  mental  functioning becomes  more perfect.   In this psychi?
development, the difference  between "1"  and "not I" marks the  principal
feature of the evolution,  accomplished by comparison  and contrast.  As this
field of consciousness becomes differentiated and separated in  consciousness
from the conscious subject the mind reaches that higher consciousness that is
characteristic of its matured condition.   We  must remember that throughout
the entire history of consciousness,  it "does not continue to exist  when the
processes of which we are conscious have passed away; it changes constantly
with their changes, and is not anything that can be distinguished from them."
(Wundt.)

    PART I.  PHYSIOLOGICAL BASIS OF THE MENTAL PHENOMENA IN THE
                           NERVOUS MECHANISM.
    Thomas Brown says,  "that  which perceives is a part of  nature as truly as
the objects of perception which act on it, and as a part of nature is hself an ob-
ject  of investigation purely physical."  This seems  an entirely  different idea
from that of Schelling when he defines life  as the "principle of individuation."
And yet these are not irreconcileable, for wherever we have ganglionic cells in
the nervous mechanism there we have the basis of that individuation which rep-
resents the crowning climax of the human   life.   Ziehen in his introduction to
Physiological Psychology says that he accepts  to start with  the antithesis of ma-
terial and psychic phenomena in the hope  of  later finding a bridge  to span 
IS
the chasm of two contraries.  It makes no difference to us whether all  psychic
phenomena  are accompanied by concomitant material processes  or not; to us
from a physiological standpoint  there can be only  psychic processes that  have
their concomitant neural processes,  for if there are any that have no such neu-
ral processes they belong to the field of  metaphysics.  There is sufficient basis
fo/ psvchic activity  in the  physiological organism.   Evolution has  introduced
two new standpoints  from which the organism  is to be viewed.  Every truly
biological idea must conform to two  kinds of adjustmeut, (a) "that of the or-
ganism to its environment;" and (b) "that  of organs to functions." (Comte.)
Eor the present we  are to consider the second of these two adjustments, leaving
for future  consideration the adaptation of the organism  in the development of
the nervous mechanism. We will find that as the organism becomes more com-
plex, specialization  of functions becomes more perfect.  Experiments,  for ex-
ample,  indicate that the  cortical centers  are separated  from one another, and
this separa'ion  has its basis in the brain substance.
    The human body  like that of any of  the higher animals consists of two
parts, (1) the mechanism of the organic life in  connection  with which we  have
the blood and whatever constructs the body tissue,  keeping the  blood in jir-
culation and purifying it; (2) the mechanism of  the animal life, including the
muscles,  nerves and sense organs.  These two are  essential  for the repleteness
of the human organism.  Both of these mechanisms are really under  the con-
trol of the nervous  system,  because through the blood,  respiration, alimenta-
tion and secretion, it displays its force.  In all the higher animals the nervous
mechanism  represents the instrument of all the functions  of  the  animal life,
whether psychic or physical.  Wherever we find a  distinct  nervous system  we
find two elemental parts of the structure, consisting  of nerve trunks which ex-
tend to the different parts of the body and ganglia which  sometimes appear in
small knots along the trunk and in  other parts in large  central cell collections,
the latter being represented by the  brain and spinal cord,  and the former by
the nerve fibers. As distinguished from the plants,all animal  forms, except some
of the very lowest,  have a nervous system.   The  animal  system  represents a
material mechanism designed to to fulfil a purpose.  Nerve  tissue  is character-
istic of animal  life.   The nervous tissue and its functional activity very closely
resembles the   contractility found in muscle  tissue,  the nerve  tissue being
closely connected by end plates with muscle,  at least in the case of the motor
nerves.  There are, however, essential differences between muscle and nerve
tissue, the functions of the nerve tissue  being peculiar  to  itself, esepcially in
relation to the  central system, the brain and the spiual cord.  The first great
function of the nervous system  is to unite the various elements, purely  physi-
cal as well as psycho-physical,  into harmony.  Different parts of the  system,
no matter how  far removed from each other, act in dependence and correlation,
because of the  nervous system.   The entire body mechanism is associated with 
19
the externa  world in the same way.  Mental development  is conditioned upon
nervous conditions.   All our sensations  arise through and our perceptions of
external things have their medium in the nervous system.  The circulation of
the blood,  respiration and all  the  other body functious are  mediated by the
functioning of the nervous system.   When a cold draught strikes the body  the
nerves take  it up, carry impulses that modify the heart, the lungs, and produce
muscular  contractions;  the body secretions are altered  and  even the psychic
balance  may be disturbed.   All this is  accomplished  through the nervous
mechanism,  in connection with terminal organs, conducting nerves and centers.
The sight of an object  is followed  by certain thoughts,  producing action on
the part of the muscles that modify all the physiological actions and relations of
the body.
    Using the term nervous mechanism to describe the physiological basis of
the mental phenomena we have  first to examine into the primal elements of the
nervous system, (1) in regard to the structure, composition and form; and (2)
in regard  to their functions.  Histology, Anatomy and Physiology really  furnish
us with this necessary structmal and functional  basis.  We must begin with
these  because these form the foundation upon which psychology is  built and if
we do not lay a solid foundation in these our psychology will be like a castle
built  in the  air.   Man differs from  animals only in the  development and en-
larged sphere of the functions of the nervous  system.   This development  from
the standpoint of the organism and the organs in adaptation to their functions,
we will consider after we  have considered the fundamental basis in the present
chemistry, anatomy and physiology of the nervous system.
    In  regard to the chemistry of the nervous system  it is not understood be-
cause the  living elements while alive cannot be subjected to  analysis.   Many of
chemical  substances are life products which when death comes cannot be said to
exist  or at least to exist in the form of life.   Besides the  complex and unstable
character  of the combinations  associated  with the nervous system render it more
difficult to analyze the nerve  mechanism  chemically.  There  are  undoubtedly
at every mental change certain correlative changes in the nervous substrgtum,
so that all the mental phenomena are at least manifested in connection with some
change material or vital in the nerve elements.  It is certain that  chemical
changes play a very importautpart in the nervous mechanism. This much we know
in regard  to nerve tissue it contains constituents that are very complex in
character, readily becoming decomposed, the  elements  consisting largely of  C
and H that possess a large combustion value.  How the  synthesis takes  place
we do not know but we  do know that in connection with   nerve tissue there is
such a synthesis, the nutriment  furnished by the blood forming a very unsta-
ble combination of albuminoid  compounds, these being  of high energic value
and during  decomposition furnishing potential  energy to the nerve substance.
It is in this  that we find what Coleridge calls "the inmost principles of its possi- 
20
 bility as a steam  engine."  Nervous tissue  is white  or  fibrous  and  gray or
 vesicular, these differing in specific gravity  from  one another.  According  to
 Daunlewski the specific gravity of the gray matter varies from 1029 to 1039,and
 that of the white matter from 1039 to 1043.  This difference in weight arises
 from the differing proportions of water and solid  constituents.   In  the foetal
 brain thee is found from 89 to 92 per cent of water and in the acult b ain f om
 69 to 84 per cenu,  ;he  white  substance  rep resenting about 69 and the  gray
 about 83. We find vacations in tnese relative amounts in the different  regions
 of  the   brail    and   spiral   co d  the lumbar  region  of   the   cord
 containing   a    larger   proportion    of   wa^er   taan    the    cervical
 region.   In  coinec ion   with  ihe  nerve cenfers  we  find  Ahat more  than
 50 per cent of the solids  :j fie gray matter and about 25 per cent in the white
 matter  consists of  a'buminous  matter.   Such  albumoid  compounds  are al-
 ways present in connection wiih the act:ve living cells,  although  the mture of
 these substances is not known.  In  addition we find cholesterin. neurokeratin,
 cerebrin and lecithin,  cholesterin representing an  alcohol substance found es-
 pecially in the  white matter of the nerves and cerebro-spmal axis; the  neurok-
 eratin is found in the gray substance of  the nerve centers  and in connection
 with the medullated nerve fibers but not  the non-medullated;  cerebrin   is a
 non-phosphorized substance precipitated in connection with the brain substance
 boiled in  baryta water.   These substances have been supposed along with fats
 containing phosphorus to be derived from the decomposition  of protagon.
 Associated with the nervous composition there seem to be  Jiese ph^sphorized
 fats. It is especially in connection with the nerve cente s that these phosphoric
 compounds are found, protagon and lecithin being the chief of these substances.
 Protagon was discovered by  Liebreich in 1865 who called it protagon  because
 he believed it to be the first of the definite constituents of the brain substance.
 It is so  far the only phosphorized  compound in the brain and  represents  the
 only chemical substance   that can be  pointed out as existing in the brain and
forming a chemical basis for physiological and psychological functions.   Hence
 it  is spoken of as one of the proximate principles of :he brain.   Lec^h n xep-
 resents  an organized phosphoric compound  found  in large  p o jortions in che
 nerve tissue, possessing according to some a  larger phosphors prcpo rioi  chan
 protagon.  In connection with protagon or  lecithin  decompose'o:i  we  find
 neurin representing the end product of  changes in the brain.   In connection
 with functional a( ivhy we find ceroain me'uabol'c processes in which there is the
production of \,he  ext-ac ives lactic, kreatin, uric acid, xanthin, together with
formic and acetic  acids.  These arise as  in  muscle in connection wi h func-
tional activity,  so .hat  in the func'ioning of an idea there  is a change in  the
 organized matte which marks degeneration in the  production of  .he  energy
 necessary to thougnc.  Tbs indicates the  close  analogy of nerve to muscle the
end nerve products in the case of activity being the same. Similarly the brain re- 
21
action during rest is neutral, during great activity as well asunder the influence
of putrefactive changes after death  becoming distinctly acid.  In  connection
with mental activity associatedwith brain activity there is a nerve disintegration
going <-n the phosphorus being  thrown off in the form of phosphates in the
urine.
  The cells are largely protoplasmic and for this  reason they are very abun-
dant in albuminous substances.   The gray matter is found to be more defic-
ient in the phosphoric compounds than the white matter, the white substance
of Schwann being very abundant in  the phosphorized bodies and cholesterin.
Almost nothing  is known of the relation of the chemical  composition of the
nervous system  to the nervous  functions  and especially to the  mental phe-
nomena.   Yet its extremely  delicate organization and  sensitive structure in-
dicates its peculiar  adaptation  to its special   kind of  work.  Chemically it
consists   of a  number  of complex and unstable  combinations, indicating
that it is possessed of  great energy  capacity,  yielding  the energy freely
when the molecular motions are aroused. Very freely these substances yield
to chemical changes in connection with the oxygen  supply.  The nerve fibers
require but little oxygen, whereas the nerve centers require a large amount of
oxygen, the oxygen  being necessary  for the great molecular changes taking
place in the cells.   In this way cell activity in the brain  depends upon the
oxygen supply  and this is furnished  by the  great vascularity of the central
nervous system,  which indicates  its great activity and finds its  basis in the
rich oxygen supply.   In this way the phenomena of  consciousness  depend
upon the chemistry  of the brain or upon the supply of oxygen furnished to
the brain in connection  with the respiratory center in  the medulla, the vaso
motor center and the higher brain centers.  As we are coming to know more
of these conscious sensations we are discovering  more chemical  phenomena
behind and at the basis of  all our sensations.   In connection with our color
sensations we are discovering that  color is subjective, the color  fibres being:
in all probability associated with certain chemical  processes taking  place in
connection  to the retina m connection with vision.  As to the  relation of
these processes  with the conscious phenomena  we are unable to trace out any
connections between the purely chemical changes  and the psychic phenomena.
Mind does not represent  the matters that are  thrown  off as waste  elements.
but the energy aroused  in connection with the formation of these products of
nerve activity.  When  function is  active there is a  consumption of matter.
Whether the matter consumed is supplied by the blood directly or is part of
the cell substance cannot  be definitely settled,  although it would seem that in
some way the cell substance  is used up since   activity results in cell exhaus-
tion and when there  is activity  in the form of function there is a definite-de
termination of the cell  substance that forms the basis of the same function to
be exercised in  the future.   The presence of lecithin, protagon, etc., in such 
large quantities in the brain seems to indicate that these substances  are not
simply carried hither in the blood stream but  are found in connection  with
the actual  disintegration of  the nerve cells in the brain.  There  may be a
permanent structural part in the cell but there seems to be certainly a num-
ber of very unstable  compounds which are constantly being disintegrated and
reintegrated again during the brain processes.  What is taken  into the cell
from the blood  becomes a part of the cell substance and in  yielding up  this
part of the substance during activity  the chemical compounds are  broken up
in connection with cell activity.
    In regard to the  structure of the nervous system we  find much light upon
psychology from anatomy.   It is  generally supposed  that  nerve  fibers  and
ganglion cells  represent  the  nervous structure.   This seems, however, to
overlook the fact that the neuroglia, which is not properly connective tissue,
but in some way represents nerve  tissue, may have  an important  bearing
upon  nerve function.   Henle says  it differs  from connective tissue in its
chemical properties,  and from this standpoint has an important chemical rela-
tion to nerve activity.  The nerve  fibers represent paths  of impulse.   The
nerve cells represent:  (1) The  ganglion cells, which form irregular masses
of protoplasm with a nucleus and several nucleoli with one or more processes;
(2) Corpuscular bodies of irregular  shape,  consisting of nuclei alone or of
nuclei with a small amount of  protoplasm, representing  probably developing
ganglion cells; (3) the  neuroglia of granular matter filling the  interstices be-
tween the fibers and  cells.  The  first two  represent the nerve  cells and the
last represents  sustentacular tissue.   The nerve  fibers  are divided  into twro
kinds,  the  medullated and non-medullated, the  former being whitish  and the
latter grayish in color;  the former belonging to the central nervous system
and therefore being of  interest in psychology,  while the  non-medulated are
chiefly found in the sympathetic  system and are of interest as the connecting
link between the emotions and the physiological conditions.   In the medul-
lated fibers we find the primitive sheath of Schwann or the external membrane
with nuclei; the white  substance of Schwann, an interior  layer of  granular
white matter semi-fluid in the living condition; and the axis cylinder, a cyl-
indrical band of fibrillated albuminous substance.  The  axis cylinder is sup-
posed to represent the  real nerve structure  because many nerves  have noth-
ing but the axis cylinder,  the  sheath being regarded as chiefly for protection
and for trophic purposes.   The non-medullated fibres  do not have the  med-
ullary sheath, being  grayish in color with flatfish  nuclei  lying at  intervals
on the surface.   The size of the nerve fibers varies throughout the body, the
non-medullated generally being  smaller than  the medullated.  The number
of  fibers also varies  as we find them in the individual nerves, 5,000 and even
10,000 having been distinguished in an ordinary motor nerve.
    Next to the nerve  fibers we find the nerve  cells which,  while they van-
considerably, have certain general characteristics.  They represent  irregular 
23
protoplasmic masses with a well marked nucleus,  sending off  one or more
processes.   In the gray matter of the brain and of the cord they are  embed-
ded in the neuroglia; in other parts of  the nervous system,  such as  the gan-
glia, they are associated with connective tissue.  In connection with the cell
we may distinguish,  (1)  A mantle of fibrillary form continuing the fibrils of
the axis cylinder; and (2) a finely granular mass of protoplasm with a nucleus
inside of which we  find one or  more nucleoli.  The cells may  differ in size
and shape; they may be unipolar, bipolar or multipolar, the branching processes
determining the size and shape.   The shape is characteristic of  the different
parts of the nervous system; for example,  the motor cells are large,  irregular
cells being  fouud in the  anterior horns of the gray matter of the cord, the
pyramidal in the cerebral cortex and the ovoidal  in  the gray matter of the
cerebellum.   Ranvier has  tried to identify all nerve structures with ganglion
cells as the primitive type of  the nerve cell.   It is said  that all these cells
send out processes, the nerve fibers being regarded by him  as simply exten-
tensions  ol the nerve cells, consisting essentially of the nerve cell substance,
the extension forming the connection betweeen the different cells and between
the cell and the muscle fibers in the end organs,   Th<j ner^e fibers are simply
cell elongations.  This is coming to be accepted more generally  than hereto-
fore, one of  the cell  processes being  regarded as continuous with  the nerve
fiber in some form in connection with the axis  cylinder.
    Having these two  primitive elements in  the nervous system we  are left
to consider what functions these can discharge.  This is important  because
these functions represent  the foundation  factors in the physiology  and psy-
chology of the  human system, namely,  the nerve fibers collected into nerves
and the nerve cells collected into ganglia.   These combinations represent the
entire nerve basis of the psychic phenomena.  We find that they posesss cer-
tain general functions in  common.   In the case of  the cells and  nerves we
find the common function  of  molecular activity  which is distinctly  nervous
in contrast with muscular activity.   When this mobility has been originated
there is the  capacity on the part of the nerves  and cells of transmitting it
from place to place within the neural structure.  In  other words the nerveg
and cells have  the properties of irritability and conductivity,  peculiar to the
nervous svstem.  This is the primal function of  both the nerve elements and
forms the basis of all nerve activity.  It involves the origination,  transmis-
sion   alteration and distribution of  the neural impulse.  It is not  true that
the hio-hest  and most perfect expression of neural activity is the origination
and conduction of psychic  influences; because we are dealing with the physi-
ological basis in a material nerve structure consisting of certain molecules of
a peculiar kind,  and of  this nerve  structure  the characteristic function is
that of neural  excitation and  conduction.  This represents,  it is true, two
distinct  parts in a single  function,   that of excitability and  conductivity. 
24
While there are phenomena associated with the nerve  elements, these  phe-
nomena are not self-caused  or spontaneously generated.   The  neural exci a-
tion originates at a point in the nerve structure by the application of  certain
stimuli.   These stimuli may be external to the nervous system or  internal,
such as variations in the blood due to the presence cr absence of oxygen and
carbon dioxide.  When a nerve responds to external stimulation,  it is said
to manifest irritability, and when  the stimulation gains no further response,
it is said to have lost irritability.   When the stimulus  is internal in con-
nection with the nervous  molecular  composition,  the  nervous  system is said to
be excited.
    When the nerve elements come to the combined into a  system they are
modified in their internal  excitability  and external  irritability,  representing
modifications of function.   The nerves play the part of conductors, the end or-
gans or the central organs performing the functions connected with originating
such stimulation as is subject to conductivity.   Among the   central cells  many
are not  subject to direct stimulation  but  can  only be  stimulated through the
nerves.   External stimuli may be applied to the end  organ, producing an irri-
tation corresponding  with the nature and function of  the end organs itself.
The afferent nerves  are stimulated  by these end organs, conducting the stimu-
lation towards  the  central  system;  while the efferent nerves aroused by the
central organs conduct the impulses to  specific muscles, glands, etc.  While
the function of the  nerve fibers is that of conducting, that  of  the nerve cells is
not so simple because the nerve cells  are,  (1)  conductors   of impulses, repre-
senting the tracts of  the nervous system ;  (2) they act  as  receivers, modifiers
and distributors of  impulses, the  chief  function  of  the cell being that of re-
directing the impulses.  In  this work of  redirection the cells  may classify and
even condense the impulses   or rearrange and divide  the impulses.   The  spec-
ial^functions that are associated with the cells are  said   to  be threefold, (1)
Automatic.  This refers  to the origination of what are called  the vital impuls-
es, independent  of any external stimulus.  This  automatic  action originates
from within but  in what way  is unknown.  This  automatism  according to
Eckhard is twofold, a regular automatic action in connection with the rhythmic
movements of  the  heart  and lungs;  and an irregular automatic  action by
which the muscular tonicity is controlled.   In neither case  can we explain how
the automatism  originates.   (2) Reflex,   When  impulses  reach the  central
cells they  are reflected  back along efferent paths,  the reflection   including
changes that  take place by  way of modifying and  redistributing the impulses.
This indicates definite cell activity and definite metabolism of the cell substance
in transforming an afferent into an efferent impulse.  The reflex  action repre-
sents the simplest nervous process  and according  to Ferrier it does  not differ
f jom the highest intellectual process.   In this  sense it  is  claimed  that  reflex
actions may be so modified and improved  in connection with certain  stimuli as 
2.")
to become automatic, the agency in this development, according to Ziehen being
natural selection.   (3) Inhibition.  Wundt  says that  certain impulses when
they enter the cells are retained there.  This is said to account for the length of
time required to travel along the tracts of the nervous  system.  That nerve
cells have the power of increasing or lessening the power of  impulses when re-
ceived is certain.  If afferent  impulses enter the cell during  cell activity  the
result is  either inhibition or the increase of activity.   By stimulating a muscle
till it becomes tetanized, it is found that the number of shocks and the  number
of muscle vibrations correspond, indicating that the nerve cells control the im-
pulses in connection with the muscles,  this control depending upon nerve  cell
changes.  This forms the basis of the  inhibitory  action of the central  nervous
system.
     The nerves have been classified according to the different functions they
discharge.   They have been classified as nerves of motion, inhibition, secretion,
trophic nerves,  or nerves which have a direct  influence on nutrition, centripe-
tal nerves that have no sensory functions and  sensory nerves, or those the  ex-
citation  of  which  may result in conscious sensation.   A  better  division of
nerves according to their functions  is that of afferent and  efferent. The nerve
impulse  ie presumed to be a  molecular vibration passing in  the form of  waves
associated with  certain definite chemical changes.  The question is, is  this  dis-
tinction of function based upon structure, or does it represent simply difference
in function.  It has been urged   that they differ  in  the processes  that  take
place in  connection with the different functions, this distinction being based
on experiments in regard to the effect of heat and certain  chemical substances
upon afferent nerves, no contraction taking place in  connection  with the mus-
cles supplied.   The afferent and  efferent nerves  seem to conduct the impulses
about the same rate.   The physiological processes taking place in the nerves
seem to  be  almost identical, the variation  in the effect produced  being due to
the cause and origin of the stimulation, the one  being exrited by the end or-
gans and the other by the central organs.   Attempts have been  made to cross
the two  sets of  nerves and so  demonstrate the possibility of  one performing
another's function.   Various  unsuccessful and  partially  successful  attempts
were made   before Bert  was successful in  reversing the course  of the nerve
fibers in a rat's tail,   by  flexing back  the  tail and embedding it  in the back.
When the healing process was complete, the tail was divided close to  the  root
and found  to be sensitive in the order opposite to the natural one.   This seems
to indicate  that  au  afferent  nerve can  when   reversed  transmit affer-
 ent   impulses   along  a  formerly  efferent  path.  Recent   experiments
by    Dr.    Cunningham  of  New    York  in  connection  with  the  dog
 have   proved   that   the    central   part   of   one  motor   nerve   will
unite with the  peripheral  part of  another motor  nerve, the  impulses pro-
ducing  incoordinate  movements  of  the  muscles  supplied  by the  crossed 
26
nerve.  In the case of crossing two motor nerves of muscles with similar func-
tion, the nerves when crossed will unite and the muscle movements will  not be
mco-ordinated to any great extent,  while in the case of muscles  innervated by
crossed nerves where the muscular functions  are entirely different, co-ordina-
tion of movement is lost,  although the nerve fibers when  crossed regenerate.
These later experiments seem to indicate that the  central nervous system  will
not accommodate itself to  changed peripheral conditions of  innervation  so as
to follow the guidance of the peripheral nerves.  In  other words the  impulses
are not accommodated to the peripheral organs.   This seems  to indicate  that
there is a specific difference in the functions of the  nervous system  depending
upon probably structural conditions and the  molecular changes   in connection
with the different  nerves.   When we  add to  this the difference in the organ
from which the stimulus originates, whether the end organs or the  central or-
gans, we have the  modifying conditions that determine  the specific functions
of the afferent or efferent nerves.   This is an important psychic point,  because
it involves the fact that the medium of the conduction  of impulses is  steady
and constant, its functioning being  structurally determined beyond the possi-
sibility of change.
    Hence we conclude that mental activity depends upon the nervous structure
and its proper nourishment in  connection with the  blood supply.  The'  nerve
cells are undoubtedly the centers of mental activity.  They are active in so far
as they are   supported.  Therefore  the support of the nerve  substance is the
essential condition of statical thought, involving mental and nerve equilibri-
um, the thought becoming  dynamic in  connection with the changes in the nerve
elements, these changes leading to mental manifestation.   Thus when a thought
exists in the mind there is a correlative brain change,  without which it could
not exist.  This brain change involves movement, whether in connection  with
rhythmic variations or molecular changes,  the movement forming the basis of
stimulation, and the stimulation producing nervous responses which  lie at  the
foundation of  impulses that  are sent  along the conducting  nerve paths.   In
connection  with these movements  and impulses time  is a necessary  element,
muscular changes,heart rhythm and lung rhythm representing the time element
from the physiological standpoint.  The human system then  is not only a great
neural and muscular mechanism, it is also a psychic mechanism which has  defi-
nite time relations with every  part of the  organism, definite  space  relations
through the peripheral end  organs  with which external objects have contact,
and in these twofold relations we  find clearly established all the  relations  that
the human subject can sustain in  life.
       SYSTEMATIC COMBINATION OF  THE PRIMAL NERVE ELEMENTS.
    We considered last week the primal elements as independent without any
relations and  combinations.   These  however do not exist in abstraction,  so
that wherever we  have analytical  elements of the  nervous  system,  there is 
27
combination into definite organs which are connected together to form a sym-
metrical whole.  The condition and function of the separate parts are depen-
dent upon the condition and function of the entire neural  organism.  "In all
the higher processes  of the  brain," says Foster,  "we must  recognize, that in
nervous material at all events, action determines structure,  meaning by struc-
ture  molecular arrangement  and disposition."   It is true  that we  can exam-
ine microscopically and electrically a nerve fiber and a nerve cell.  But this
represents a separation of the organic relation  it sustains to the  whole system
and therefore a pathological  condition, so that  their normal  function is inter-
fered with.   The nervous  mechanism consists  of the interdependent  relation
of the parts of the system and the interfunctioual  activity af  the combined ele-
ments. We find  the  cells and fibers in very large  numbers in the nervoua sys-
tem, the combinations of these nerve elements  varying considerably in differ-
ent parts,  representing differentiation of function.
     If we take the  nervous system as  a  whole  its main function is to unite all
the diverse body functions, so as to form  a united plan of  organic develop-
ment.  This  involves a  large amount  of work  and a variety  of functions
harmonized.   To unite the different  nerve elements so as  to harmonize these
diverse nerve factors,  represents the supreme function; in other words there is
here an economic division of  labor.  In the case of the amoebic life we find a
small mass  of protoplasm seemingly undifferentiated,  in which  we find a nu-
cleus.  So far as differentiation exists it  is  found  in the division  of the exter-
nal layer  from the internal granular matter.  Small as this organism seems,  it
consists of a great number of delicate molecules,  all of which are combined in
the  discharge of  metabolic, respiratory  and  reproductive functions.   The
chemistry of  amoebic life involves  changes  in the protoplasm, breaking up
the old and forming the new, in connection with 0 absorption and CO2 excre-
tion.  In  connection with the protoplasm we notice irritability and  automatic
mobility,  manifested in amoeboid movements, depending upon the  changes in
the  internal  mechanism.   In  other words it  has  within  it a self-regulating
power, the beginning of a qiind.   As  we  rise  from this lowest of  the animal
forms  to the higher and highest of animal  lives, man, we find increasing com-
plexity of structure accompanied  by increasingly complex  and  varying  func-
tional  development, so that the primary  division we find in the  amoeba of the
external and internal forms  but the precursor  of the  increasing division of  la-
bor manifested in the differentiated  functions of the highest forms  of animal
life.  The  irritability and automatic motion from within found in the amoeboid
molecules simply suggests the differentiation taking place  in which the former
comes to  be associated with answering the external stimuli, and  the  latter with
orio-inating  automatic  impulses that are  closely connected with the vital activ-
ity.   This gives us a superficial  and and  an internal  functional division  but
these must  be united in some way.  How?  To accomplish this we find in the 
28
more primitive nervous system and even in the  highest  organism, C1) *u*  ac®
                 ,                      i  l-   r  /o\  infprnal cells that can
cells which respond to and receive external stimuli; (<s)  internal        tissue
initiate internal impulses, and (3) a  connecting  pathway  of   nerve  l
uniting these two, the external and internal.  In order to complete this union
we must add another element (4) that  the muscles are brought into direct re-
lation  with  these  central  cells and into indirect relation with the  supeinuai
cells so as to  be under the control of automatic  and  reflex  impulses.   1  ese
represent then the four fundamental  elements associated with a combined nerv-
ous mechanism, the basis of mental phenomena.
    When this mechanism becomes still further differentiated in development,
we find (1) that the superficial cells become distinguished from one another by
the special function discharged in the case  of each, representing, (a) the sen-
sory organs,  as the organs of sense, and  (b) the  motor organs like the end
plates and terminal organs of motion; (2) the central nerve cells also become
differentiated, (a) in the reception, modification, classification and distribution
of the sensory impulses after co-ordination from reflex action, (b) in regard to
the initiation of automatic impulses, and (c) in connection with the   conscious
phenomena of the sensitive life;  (3) the fibers and tracts of conduction in  the
union of the external and internal elements of the nervous  system   represent
the sensory, afferent and centripetal and also the motor, efferent   and centrifu-
gal functions.  This represents from the standpoint of psycho-physiology  the
complex development of the human  nervous system as a whole.   It is here  we
we will find the basis of sensation, intellection, emotion and volition all  the
highest functions being developed from the primal sensations and  motions.
     "Every cerebral element," says Hering, "is  subject to the educating  in-
fluence  of   those  sensory  fibers  with which it is automatically connected."
This furnishes the key-note of psychology that begins with sensations associ-
ated with a sensory apparatus as the simplest psycho-physiological  fact.   We
find the nerve fibers collected into nerves and nerve  trunks,  while  the  nerve
cells are collected into ganglia more or less  complex,  such as we  find  in  the
scattered ganglia, in the brain and spinal cord.   We 3nd two great systems, the
sympathetic  and  the cerebro-spinal, the former consisting of neural  cords   one
on each side  of the spinal cord with three great plexuses  in the  thoracic  and
abdominal cavities together with ganglia scattered over the body in  connection
with the vascular system and a large number of distributing and communicating
nerves, the former bringing it into close connection with the  internal  organs
and blood vessels and the latter uniting it closely with the  cerebro-spinal  sys-
tem.   The  three main ganglia represent nerve cell and fiber collections at the
 base of the heart, in the upper portion of the abdominal cavity and anterior to
 the last lumbar vertebra.  According to (Jaskell  the svmpathetic ganglia repre-
 sent its close connection with the spinal system as the posterior  ganglia of  the
 cord.  The sympathetic system forms a link between the sensations,  emotions 
29
and ideas which originate in the molecular condition of the cerebro-spinal cen-
ters and the body organs, establishing close relations with the  heart  and  the
abdominal organs which are closely connected with psychic conditions.   It is
in this way that emotion influences the circulation, heart action,  alimentation,
etc.   Much of the stimulation arising in connection with the thoracic and  ab-
dominal organs passes through the sympathetic system to the  central organs.
Maudsley says that the ganglion cells of the sympathetic system  in  co-ordina-
ting the separate elements in the tissue represent the simplest form of  the prin-
ciple of individuation.
    The cerebro-spinal system is represented by  the two   great  central  ele-
ments,  the  brain and the spinal cord.  Associated with these we find certain
membranes, the dura mater close to the cavity of bone, differing   anatomically
in the cranial and spinal cavities. The cranial cayity is divided by the three dura
mater processes into two halves.  Next we find the arachnoid which  contains
the fluid that fills up  the inter spaces in connection with the area formed by
the dura mater.   Lastly we find the pia mater which  represents  the  vascular
membrane of arteries and veins bound up in fine connective tissue,  containing
the branchings of the blood-vessels as they pass to and  from the   brain  and
spinal substance.   The cerebro-spinal nerve substance is closely  bound togeth-
er and protected in connection with these three membranes, the   pressure  and
blood circulation forming important elements in the brain nutrition.   The spi-
nal cord extending along the spinal canal from 15 to 18  inches  weighs  about
 1 1-2 ounces.   It is divided by the fissuers into two halves, each half being di-
 vided imo three columns, anterior, posterior and lateral.  The two  halves are
 united by the commissures, the anterior white and the posterior gray, the  lat-
 ter being much  larger than the former, except in the cervical and  lumbar pro-
 tuberances where the white is larger.   Along the  entire length  of the  gray
 commissure lies the  central  circular canal lined with ciliated cells.  In the
 white substance of the spina1 cord we find the lymph and blood vessels, togeth-
er with connective tissue and nerve fibers, the chief constituent of these  fibers
 being the axis cylinder, the nerve fibers varying in size and also  in direction,
 the majoritv being vertical,  while others are  horizontal and others  oblique.
 In the gray substance of the cord we find the same elements as  in  the  white,
 together with the nerve cells.  The nerve fibers are non-medullated  and  differ
 from those in the white substance in their minute sub-divisions forming   plex-
 uses.  The number of the nerve fibers is very large, Birge having  counted  in
 the  anterior  roots  of the spmai cord of frogs from 5,!>84 to  11,468.   It is
 impossible to trace the nerve paths in the spinal cord.   As the spinal cord de-
 velops  there is a later development of the medullary substance  of  the  nerve
 fibers so  that these can be distinguished in some cases.  When   divided   from
 their origin the nerve fibers degenerate, the connective  tissue  filling  up  the
 vacant space, so that  the nerve paths can be followed out to a certain extent. 
30
    There have been differentiated two  tracts in the  antero-lateral  columns
called the pyramidal and  direct  lateral cerebellar tract,  the former being
traced from the anterior pyramid of the medulla, the latter lying between the
lateral pyramidal tract  and the external  surface of  the cord.  Other tracts
like the Goll tract, have been traced out.  These facts indicate that the com-
bination of the spinal cord furnishes nerve paths for impulses and also has a
series of reflex centers; the tracts representing the afferent and efferent nerve
impulses and the centers varying points of functional  activity, all  of which
are united in connection with the upper centers.  Here lies the possibility of
connecting the inner and outer.
    The same nervous elements, including cells  and fibers,   with  connective
tissue and neuroglia bound  up in the  encasing membranes are found in the
structure of the brain.  Structurally we find that it consists of (1)  the medul-
la, the enlarged extension of the spinal cord, (2) the cerebellum covering the
upper posterior part  of the medulla and extending on the two sides  beyond
it with a superficial lobular division;(3) the pons Varolii  enlarged to the an-
terior and above the medulla; and (4) the cerebrum above both the pons and
cerebullum,  divided into two   hemispheres and  filling  up the larger part of
the cranial cavity.  In the  medulla we find  as in the cord,  gray and  white
matter,  the gray matter  being here collected into  masses,  the gray matter
continuing that of the cord and also in independent masses.   In the  cerebel-
lum we find the reverse arrangement of  gray and white matter to that  in the
cord and medulla, the gray being external,  the white substance representing
three great nerve collections connected  with the three crura cerebelli.   It
forms a complex  combination of cells and nerves, lying  outside of the direct
nerve tracts and united by the crura to all the other parts of the brain.  The
pons Varolii  represents the common meeting ground  in  connection with the
nerve tracts between the central organs and the  other parts of the nervous
mechanism.   It is really an enlargement  of the wall of  the  fourth ventricle.
The cerebrum represents the larger part of the brain, consisting of a number
of parts,  varying in size and in function.   In it we find the  cerebral hemi-
spheres, the large  basal ganglia, the  corpora striata and optic thalami,  the
corpora  quadrigemina and the pineal gland.  It is divided into  two hemi-
spheres by the median longitudinal fissure.  By dissecting this   fissure  the
hemispheres   are found to be  united at the bottom by the corpus  callosum.
The  external   surface  of  the hemisphere is convex fitting the cranial cavity.
while the internal surface is flattened along the median fissure, separated from
each other as  hemispheres by a process of the dura mater.   The bottom sur-
face is divided from the  cerebellum  and  pons by another process  of the dura
mater.   On the upper surface of the  hemispheres we  find  the gray matter, ar-
ranged in convolutions, these convolutions being  separated  by sulci  or fissures
some of  these being  so well marked as  to form natural dividing  lines of the
brain lobes, the less marked processes dividing the lobe into convolutions. 
31
    it is  this lobular and  convolution  division that gives  the brain cor-
tex its special nervous functionality and its psychic importance.  The gener-
al structure of the cerebrum is similar to the cerebellum, an internal portion
of white matter being surrounded by a superficial cortex of gray matter.  The
two lateral sides of the white matter are bound together by strong fibers  of a
commissural character (corpus  callosum) which is overlapped by the gyrus
fornicatus.  The corpus callosum forms the roof of an internal cavity in each
hemisphere, the lateral ventricles  which are surrounded by a delicate trans-
parent wall and  filled with  ventricular fluid.   At the floor of each of these
ventricles we find the surfaces of the basal ganglia.   Here  is found a large
pear shaped body the  narrow end outward and the large  end projected  into
the anterior cornua of the ventricle, called the  corpus striatum,  the two parts
of which are divided by the internal capsule.  Between the projecting parts
of the corpora striata we find the oblong optic  thalami.  Posterior to and be
neath  the optic thalami we find two pairs  of bodies,  the corpora quadri-
gemina.
    The fiber fascicles of the cerebrum connect its  hemispheres, unite these
with the lower parts of the brain and when bound together form the  origin of
some of the nerves.   The crural fibers are formed into two groups divided by
gray matter, the former being continuous with the  longitudinal fibers of the
pons  as these come from the medullary pyramids, terminating in the corpora
striata and passing  through the internal  capsule  to the gray  matter of the
cortex cerebri.  The nerve elements in connection with the basal ganglia are
all arranged in such a way as to prepare this portion of the brain to act as a
co-ordinating center  in connection with all the motor nerve paths  and the
sensory nerve paths, giving to these basal ganglia very characteristic sensori-
motor functions  of  a  reflex and automatic nature, in subordination to the
cerebral centers.   The pathways  to  these higher cerebral centers are found
from the basal  ganglia in connection  with the corona radiata,  formed by the
radiating fibers of the corpora striata,  the optic thalami,  the  internal capsule,
leading direct into the convolutions of the cerebral hemispheres. These con-
volutions of the cerebral  hemispheres from an external standpoint vary  very
much.   In development some of the convolutions are well marked from early
foetal life,  permitting  the division of these convolutions into three classes.
The first represents the  main division of the surface of the hemispheres into
five lobes, the  frontal, parietal, sphenoid, occipital  and central, although the
dividing lines are not clearly marked off from each other.  The second and
third classes represent minor sub-divisions of  these lobes by sulci running in
different directions. The gray matter is uniformly arranged on the surface and
the white matter in the interior of the cortex cerebri but there are marked differ-
ences in the cells and in their  arrangement.   Meynert  points  out  that the
common  arrangement is  that of five  laminal  layers, the entire cortex being 
32
about one-tenth  of  an inch  thick.  These layers consist of a matrix with a
few globular cells, the next two layers having the pyramidal cells; the fo™
layer having a large number of small irregular and  globular cells;  the fifth
layer having the spindle  shaped cells with long branching  processes, these
cells being compactly bound together and sending off lateral processes.
    In the neuroglia are found small corpuscular  bodies and  cells,  repre-
senting simply nuclei.  The white substance all originates in connection with
the gray cortex substance, the nerve fibers being either peduncular, commis-
sural or arcuate, the first connecting the cerebrum and the lower portions of
the brain; the second formerly supposed to connect the two hemispheres but
as the tract lies in the corpus callosum, the fibers intersecting each other on
the way to the cerebrum hemispheres  and therefore forming decussations;
while the third connects the  gray matter of the separated convolutions in the
same hemispheres.   Meynert considers  the gray masses  and the converging
and diverging tracts of the cerebro-spinal  nervous mechanism  as a series of
projection systems,  the sensory nerves being the feelers and the motor nerves
the arms of the cortical  gray substance.   The gray  matter represents there-
fore a sensory and  motor cortex  in which the afferent impulses collect and
the efferent originate and are distributed.  It  forms  therefore  a projection
system in connection with the muscular system.   The gray substance of the
brain lower than the hemispheres, according  to Meynert, represents in con-
nection with this projection system, either interruption masses or a reduction
region in connection with the entire system.  Here we find the nerve paths
from the cerebral cortex broken up and diverging in different directions.  This
represents an important  functional point in establishing  the relations of the
cerebrum with the lower parts of the nervous system and therefore one of the
points of psychic  interest.
    Thirty-one pairs of spinal  nerves and twelve pairs of cranial nerves
bind the cerebro-spinal system to the terminal organs of sense  and  motion.
The spinal nerves arise from the cord, passing out through the intervertebral
foramina,  representing  the  cervical, thoracic, lumbar,  sacral and coccygeal
regions.  The cranial nerves originate  from the cranial base and pass out of
the foramina  on the floor of the  cranium, representing the sensory nerves of
special sense, the first,  second and eighth;  the  motor nerves supplying the
eyes, the face and  the tongue, the third, fourth, sixth, seventh, eleventh and
twelfth; and the  sensorimotor nerves that supply the facial, laryngeal and
pharyngeal muscles and the membranes and internal organs of the body, the
fifth,  ninth and tenth.
     These represent  the complete  systematized nervous mechanism.   The
one conclusion we reach  is that by differentiation, becoming more and  more
complete the entire nervous  mechanism is fitted into the body system,  so as
to discharge  the  distinctly nervous  functions of conducting media, end or- 
33
gans and central functions, which represent the three great  functions of the
nervous system.   While we speak of  these functions as in a sense distinct,
yet as Meynert  says there is but one single  functional energy  inherent in
brain cells that of sensitiveness, the sensory nerves being the keys that reg-
ulate the nervous mechanism and lead to the activity of  the muscles.   ''Spe-
cific energies,"  says Meynert,  "depend altogether upon the peculiarities of
the end organs and  sensitiveness is the only specific  property of brain cells.
Within the forebrain sensitiveness is converted into actual  sensations." It is
here that the anatomy of  relations we  have traced out is  of special  signifi-
cance in  connecting this  seat of sensation with all the rest of   the nervous
mechanism.  Here in the cerebral cortex,  not in any one part of it,  intelli-
gence and consciousness are localized.  Each  hemisphere  consists of "pro-
jection systems"  which unite the cortex with the sensitive regions and also
the motor organs;   the white  substance  forming  "association  systems" of
minute fibers and  nerve collections  which unite all   the parts of  the cortex
and form the basis of  all mental  perceptions  and judgments.   This makes
possible what has been called the "sensations of innervation," in other words
the centers that are identified with definite activities  in connection with the
muscles and body  organs, the sum total of these centers  constituting individ-
uality.  The individuality of psychology consists of this primary physiologi-
cal individuality expanded and developed in connection with the secondary
individuality that springs up out of secondary mental perceptions conjoined
by association.  We see in this how fully mind is conditioned by the nervous
system.                                                    " ; .>
                   THE END ORGANS AND THEIR FUNCTIONS.
    In the general division of labor  that we find in the cells during develop-
ment some of the  more superficial  cells become very  sensitive in connection
with external stimuli.  This results in  the specialization  of these  cells which
are so altered so   as  to  receive  and  modify these stimuli  transforming
them to neural  commotion and transferring  them to  the  conducting nerves.
The end organs,  therefore,  play an important part   in establishing the con-
nection between the stimuli  and the nerves.   In other words  they form the
specialized superficial neural organs adjusted to certain stimnli.   This  neuro-
muscular mechanism therefore represents the  medium in establishing  a rela-
tion between mobility as found in the  relations of the  external and the organ
and the mobility of the neural processes.  In the  end organs the sensory nerve
fibers terminate in close relation with the  muscular fibers  and cells.   Hence
these organs consist of the nerve processes and the arrangements of  muscle,
membrane, bone,  etc., by which the  stimulus is received,  modified and pre-
pared for  transmission to the nerves.   The  sense organs  represent therefore
nervous and  muscular  combinations and  modifications of eell and fiber; the
motor end organs represent similar neuro-muscular adaptations  in connection
with the termination of the motor nerves in the muscles of motion. 
34
    (1) Smell.   The sense of  smell is  associated with  the mucous lining in
  the  upper nasal cavity  in the region of  olfaction.  We  find the cells  in
  two forms,  olfactory  and epithelial,  the former  being  fusiform  in  shape
  with rounded  nucleus  and fine processes,  and the latter greater  with oval
  nucleus covering the epithelial surface.  The olfactory  nerve processes  are
  enveloped in minute granular and neural substances.   In order to  excite the
  sense of smell the irritant must float in the moving air so as to cause its con-
  tact with the lining membrane, the process of inspiration carrying the stimu-
  lating substance in the inspired air to the membrane.
    (2) Taste.   In connection with the  tongue along the margins  as well as at
  the point and root are found  papillary eminences of two kinds,  the oircum-
  vallate consisting of connective tissue that is filled with epithelium.   When
  the epithelium becomes thinner at the  sides  we find a taste zone reaching up
  to where these papillae are not covered by the  lateral wall.   The  fungiform
  papillae represent eminences covered all axound with  epithelium.   Tbe taste
  bulbs which are found in the  fungiform and   circumvallate papillae  are like
  barrels filling up the cavities of  the papillae,  the bottoms  resting in the con-
  nective tissue and the upper portion being elongated like the neck of a flask.
  Each bulb contains a number of cells, these being of two  kinds, the gustatory
  long  and narrow with a definite elliptical nucleus and the  epithelial  being also
  long  and narrow.   The upper parts of the cells develop into minute processes
  that are  continuous  with the gustatory fibrils.  The taste  nerves are the glosso
  pharyngeal that passes to the posterior  part of the tongue entering the papil-
  lae and ending in a granular plexus,  and the lingual which innervates the apex
  of the tongue in  connection  with the trifacial.  The sense of taste is not so
  particularly localized as smell, although smell and taste are intimately connect-
  ed, Kant defining smell as taste at  a distance.
    (3) Tactile Sensations.   The sensory nerves that branch off into the skm
  which give rise to touch  in the more general sense terminate either in con-
  nection with delicate fibrils or in connection with special tactile bodies. We find
  different forms of the sesensory end   bulbs, corpuscles of Pacini  found in lay-
J  ers, the internal  layers being  arranged in  concentric form around a softened
  nucleated matter.   In fine fibril form the axis cylinder enters the  corpuscle.
  These are associated with the palmar portions of the hands and feet.   The  end
  bulbs of Krause are small, nucleated  corpuscles, the fibrils ending in the bulb
  substance.  The Wagner corpuscles represent oval bodies in conical form,  the
  fibers creeping in around the  papillae winding around  the  Corpuscles and
  uniting into coils.   Contact  represents the  simplest  sensation;  this passes
  very  readily  into pressure and pressure soon  passes into the  sensation  of
  pain.   Pain isdefined as  "the prayer of a nerve  for pure blood," a  physiolo-
  gical   truth  which  indicates  that the mechanism  is abnormal in  some way
  signalling a danger  point and indicating the need of repair.  The entire  skin 
35
sensitive  but not to the same degree, sothat the fibrils  terminate in different
ways in the skin, indicatingthat some fibers represent contact, others pressure,
others   heat  and   cold,    while   the  excessive   stimulation    of   any
of these represent pain.  In connection  with the Pacinian bodies   which are
found in abundance close to joints, ligaments,   periosteum we find tactile sen-
sations associated with  the muscular sense  in connection with  flexure,  exten-
sion,  rotation and all  the yoluntary muscle  movements.   Accompanying all
voluntary muscle movements is the sensation of  effort depending on the force
of contraction forming   the basis of the muscular  sensations  the brain being
kept in close touch with the external conditions of the body and the actions of
the contracting muscles.
  (4) Hearing.   The sense of hearing like that of sight  utilizes a part  of the
structure as:a mechanism for  collecting  and concentrating  the auditory ele-
ments so as to present the stimulation to the.neural elements.  The auditory ap-
paratus consists of the eighth nerve in its connections with the  epithelial and
neural elements.   Tne auditory mechanism is divided into three parts, (1.) the
outer ear,  which  consists of a  shell shaped  structure  of value in  judging
the direction of sound waves, and of the outer,meatus, a winding passage lead-
ing from the  concha to the tympanum, protecting it and acting as a resonance
box in the modification of sound  waves, modulating and  intensifying  sounds;
(2) the middle ear, which is a hollow cavity of bone,  connecting the  external
meatus and the inner ear.  At the bottom of the external meatus.is,  the tym-
panic membrane which is the outer wall of the  membrane set in a bone cavity.
The internal  partition dividing the middle and inner ear has two openings, the
oval foramen partl}r filled by the  orbicular membrane and the fenestra rotunda
closed by the secondary tympanic membrane.  Anteriorly there is an opening
into the eustachian tube, a chain of little bones  stretching across from the out-
er to the inner wall.  In the tympanic membrane  are three layers, the middle
mucous membrane representing the vibrating membrane.  In connection with
the tympanum the sound waves  are transmitted  to   the internal ear.  certain
modifications taking place in order to adjust the sound to the  receptive organs.
Whe the sound waves reach the  membrane they have a large extent  and a
small intensity, the vibratory waves producing vibrations of the taut membrane
and changing both amplitude and intensity as the  vibrations strike against the
membrane.   It is  very responsive to these vibrations  that are not in  harmony
with its own and repels those that diverge from its keynotes,  until  it has har-
monized these partial notes.  Hence  the membrane has  no predominant  key
but by reason of its funnel shape iu connection with the malleus whose -handle
attaches at the center  and on account of  the chain of  bones with  which ;it is
weighted so as to dampen any peculiar tene of its own.   In this way it  is able
to take up  and adjust a wide series of tones.   The top of the  funnel points
internaUy so that  the force of the acoustic  waves is pulled in towards a point 
36
of cencentration. The simultaneous vibration of the auditory bones is around a
common center, the  variations depending  upon the nature of  the tones that
reach them in connection  with the acoustic waves,  so that out of  diverging
notes they can form a symphony.   The increase in the tension of the tympan-
ic membrane dampens the movements of the auditory bones, making the mem-
brane capable of  responding to  higher  notes and increasing  the rate of the
auditory sensations.  The eustachian tube which  communicates  between the
tympanum and the  air is partially  open and closed  so that the air  renewal
takes place and by cilia action the mid ear secretion is carried to the  pharyn-
geal opening  and maintaining  a condition of equilibrium in the cavity.  The
auditory bones are moved in connection with the tensor tympani  which con-
tracts only at the beginning of a  sound whereas it  relaxes if the  sound con-
tinues.   When the malleus is pulled in the  tympanic membrane is tightened.
The stapedius dampens the movements of the stapes and the orbicular  liga-
ment in the case of harsh and loud sounds closing  them out from the laby-
rinth.   The fifth nerve  supplies  the tensor  tympani by a branch  from the
otic ganglion, and the  seventh supplies the stapedius, the paralysis  of the
fifth resulting in dull hearing  and of   the seventh  in sensitiveness  to loud
sounds.  The mid ear modifies  the wave vibrations  fitting them for trans-
mission to the  inner ear.   (3) The inner ear.  Here we find  three double
organs consisting of  bone channels and membranes, in the  petrous part of
the temporal bone.   This labyrinth of bone consists of the cochlea or  convo-
luted shell tube divided into two compartments an upper and a lower  in the
central part of which is a spiral pillar, the compartments conmunicating by a
foramen; the vestibule or central cavity, the membranous part forming two
sacs, and communicating with the  scala vestibuli  so that the perilymph is
continuous with the  cochlea;  the semicircular  canals or winding  channels
three in number, opening into the utricle,   the endolymph having  free com-
mumication   with the  vestibule and cochlea.  The three canals  have their
planes at right angles to each other.  The endolymph fills the membranous
portions which are suspended in the perilymph these  having an  important
modifying influence on  sound vibrations.  The end organs terminate  in con-
nection with the membranous portion of the labyrinth.  When the auditory
nerve comes near  the labyrinth  it divides into  a vestibule and  cochlear por-
tion,  the former  dividing again into minute processes that terminate in the
cells, while the latter passes through  the mediolus and  then  distributes its
branches. The function of  the inner ear  is to receive, modify and  transmit
the auditory waves. In the canals the sound vibrations are divided, the move-
ments producing stimulation of the nerve endings.   Sounds that reach the ear
are of two kinds, noises and notes.   Out of these by the sympathetic action of
the auditory apparatus harmonious sounds are produced.   It has be    1 '
that the vestibule and the canals respectively receive noises and  not  I  t  v.* 
:37
has been disproved by recent researches which  seem to point to the  fact that
there is no such  distinction of sounds  physiologically.   According to Helm-
holtz in the internal ear we find a series of resonators  each one capable of an-
swering to a special vibratory note and as all the minute  fibers end  in minute
organs,  the rods of  Corti being vibrating  structures,   the  vibrations being
transferred to the nerve processes.  These  represent  piano keys,   3,000 in
number,  each with a  perceptible pitch.   In his later theory  he lays hold of
the cells  arranged on  the surface of  the  basilar membrane.   Hensen thinks
that the radial fibers in connection with the basilar membrane are all  pitched,
the motions of these stimulating the nerves.  The other theory is that the anal-
ysis of sounds does not take place in the ear  but in the brain, the corti rods or
the minute fibres vibrating as  a whole at  every audible sound, the vibrations
stimulating the nerves giving form to the neural commotion telephoned to the
brain  where the analysis takes place.
    (5) Sight.  Here we have the  sensations of light and  color.  The eye is
an optical disc made in camera form whose lens is self-adjusting, the image be-
ing cast upon  a neural membrane.   We find  three concentric layers  of cover-
ing, the sclerotic a rough fibrous coat, the interior part being white and the
middle part translucent as the cornea; the choroid of  pigmented and vascular
material, consisting of folds and a diaphragmatic  portion which is bathed  in
gequeous humor ;the retina or internal sensitive coating covering the choroid as
layers of  membrane.  The  refraction in the  eye takes  place in  connection
with four media, <"he cornea,  the aequeous humour behind  the cornea, the crys-
talline lens lying between the iris and the fourth medium,  the vitreous humour
between the lens  and the retina,  a semi-fluid mass  enclosed in  the hyaloid
membrane, forming a very transparent  body.  In connection with  these the
muscles aid in the completion of the  structure especially in giving miobility to
the eye  in the process of constructing its field of vision.   The miobility of the
eye is controlled by the recti muscles that have their attachment in connection
with the  bony wall,  while the oblique muscles aid in the  movements of the eye
in different directions.   The  refraction of a  ray of light in  connection with
a curved surface depends on the radius of curvature and the variation in the re-
fraction indices of the two media through  which the ray  passes.  The refrac-
tion indices of the four media are  all greater than air, that of the cornea,  the
aqueous and vitreous humour almost  the  same as water  and that of the  lens
greater on account of the number of layers.   In connection  with these termi-
nal organs of vision we find a structure in connection with which the impress-
ions made upon the organs build up sensations of light and color so that varia-
tions  in  connection with the number, character, color and order of these sensa-
tions  give rise to the  visual picture of the size, form, location and miobility of
the external objects of vision. The important part of the eye from this stand-point
is the retiua, in connection with which the image formation takes place. The  four 
38
 media of refraction represent different surfaces each succeeding surface forming
 an object for the next  succeeding surface.  In the lens we find that each layer
 has its own index of refraction so that the differences  permit of more  refrac-
 tion taking place.  The optical problem therefore is complicated by  the differ-
 ences in the refractive indices and the variations  in  curvature.   The  power
 of accommodation represents the capacity to change the refracting  conditions
 for differing distances.  This is accomplished  by changes in the  convexity of
 the lens particularly on the interior surface.   This takes  placd under  the di-
 rection of the brain  in connection  with the exercise of the voluntary   power.
 According to Helmholtz the resting lens is in a condition of tension depending
 upon the elasticity of the lens and the attached suspensory  ligaments.  The
 ciliary muscle by drawing in the opposite  direction removes the  tension  per-
 mitting the lens to gouge on its  own elasticity.   When the ciliary  muscle con-
 tracts the  vitreous  humor is driven into the  open spaces at the   sides of the
 lens resulting in convexity of the suspensory ligament. The nerve fibres to the cil-
 iary muscle come from the motor oculi nerve through the posterior roots.   Aris-
 ing in the posterior portion of the floor of the third  ventricle  contiguous to the
 origin of the nerve that controls  the internal rectus muscle  in this way  har-
 monizing activity from nerve origin  in connection  with  accommodation.  The
 retina becomes active when the image is formed upon it supplied by  nerve  fib-
 ers from the optic nerve.  After entering, the branching fibers radiate in all
 directions, the filaments being distributed among the cells not of nervous mat-
 ter.  The rods and cones  represent  rows of palisades  side by side, the one
 cylindrical and the other conical in shape, representing the sensitive layer of
the retina,  probably associated  with certain chemical changes when the ray of
light falls  on the retina  resulting in stimulating  the terminals   of the optic
nerve and  producing  impulses  resulting in visual sensations.   The poiut of
clearest vision is the yellow spot with  a depression in the center.   At a short
distance from this to the interior the optic nerve breaks into the retina forming
the blind spot which does not seem to act because  of the absence of  nerve ele-
ments.   The neural process of vision  begins in the  rods and cones,  although
they are  not immediately subject to impression by the light in the production
of the sensations of vision or till certain changes take place  that result  in the
injury of the eye.  In connection with the rods and cones a process of chemical
decomposition is supposed to take place stimulating the nerves.  Light  from a
physical standpoint is a vibration, the vibrations affecting the retina, produc-
ing molecular changes that stimulate the optic nerve.  The light that  enters the
eye is partly absorbed by the pigment and partly reflected.  The rays reflected
return  through the pupil  uniting  with the entering rays to form  a picture.
Thus when an image is reflected on the retinal  surface it is reflected  on the arc
of a spherical  surface.  Color  as distinguished  from   light is a sensation
 aroused by the action of the  rays of light of a certain length upon  the  retina 
39
that is color  depends upon  the rays that  fall on the retina during a  definite
period of  time.  With a  certain number of rays we  get a sensation of red,
and  with about  double that number of  rays the sensation  would be violet
The white light is compound, the waves of red being of such a length that 451
billions of them reach a given point  in one  second  of time, while the waves
that   produce  a violet  are  much  shorter,   764   billions   reaching  a
given   point   in   one   second  of time.  The  waves of   intermediate
length from  the  other   colors   of   the spectrum.   Thus color  is   a
sensation due to a particular kind of stimulus.  It seems therefore that the eye
is a delicate  mechanism adapted  to very complex  physiological  and  mental
conditions.   This forms the reason of  the eye sensations having such a close
relation to psychic activity.
    In connection with the motor  fibers we find the  terminals  in muscles,
glands and electrical bodies.   The nerves branching  among the  fasiculi  of the
muscles divide and subdivide forming numerous ramifications, the  single deli-
cate fibers ending in muscle fibers.   Losing the  medullary sheath the axis cyl-
inder  is divided into  minute fibrils.  The axis  cylinder passes  through the
sarcolemma,  the neurilemma becoming  continuous  with it.  As  these fibers
surround the disc shaped bodies inside the sarcolemma they form the  motor
end plates.   The form and  structure of these vary  in different muscles,  the
terminal characterizing the  particular  muscle.  Thus we  see the close and in-
separable relation of the neryous  mechanism to  the  muscles, bones and liga-
ments, indicating the  close relation of mind and the mental phenomena to the
delicate structure of 4be body,  so that the mind is localized in the body  rather
than in the neural mechanism.
    The Xerve Conductors.  Having discussed the end organs,  we must
now discuss the neural path  between  the end and central organs.  As soon
as the end organs have transferred the molecular process into a  neural pro-
it is sent out over the  nerves as conducting cords.  Excitation represents the
cess origination of the neural commotion.  Conduction  is the continuance by
propagation  from  one point to another so that each nerve  point has some-
thing to do  in the communication of  impulses.  Thus excitability  and con-
ductivity represent the same commotion from a different standpoint, the pro-
gressive  movement taking place along the nerves.  From this  point  of view
all  of the  nerves are  alike  in their conduction  of  impulses.   The  general
physiology of  the nerves looks upon the nerve  in  its abstraction from the
neural mechanism and under stimulation  externally  to itself.   Lach  part of
the nerve can  stimulate the adjacent part and receive stimulation from it.
An attempt has been made to identify  nerve current with electrical current.
But recent investigations have shown  that there are essential  differences be-
tween nerve processes  and electrical  currents.   For the  general physiology
of nerve will must refer you to the results of the electro-physiological exper-
ments discussed in physiology. 
40
     Neural functionality is the important point in nerve conduction and this
depends upon three  important  conditions.  (1) Neural vitality.   In order
that  a nerve may  perform  its function of  conductivity it  must be  alive..
Hence the  function is physiological.   It is not necessary that the  nerve die
when the body dies or even when the  nerve is taken out of the body.   It is
hard to say when  a nerve dies as it has no  rigor mortis.  When the nerves
die they manifest two  distinct phenomena,  (a) as soon as they are divided
there is an increase of  irritability, (b) after which it gradually decreases till
it is lost, these changes varying in different  parts of the nerve.   The lower
part of a divided nerve maintains vitality longest,  hence, the Bitter-Valli  law,
that nerves degenerate from the center to the periphery.  When  a nerve is
divided in its place in the  body its  irritability increases  temporarily, after-
wards gradually losing vitality,  degeneration taking place from the  division
to the  periphery.  Eegeneration may take place  by  the growth  of the  axis
cylinder from the central part piercing out into  the Schwann sheath in the
peripheral portion.  The conductivity of  the nerve is regained earlier  than
its  irritability.   (2)  Neural  conductivity  depends  upon  the proper  nu-
trition of the nerve and this takes place in connection with the O  supplied  in
connection with the arterial blood. O does not seem to be so necessary for the
conducting nerves as  for the central nervous system, because irritability can
be preserved in a nerve in a damp vacuum,  although  some oxygen  seems to
be essential to  the neural vitality.  (3) When  nerves are  exhausted  they
cease to perform their functions, at least efficiently.  It is not easy to sepa-
rate nerve fatigue  from the fatigue  of the central organs or the end organs.
The nerve is much more difficult to exhaust than  muscle,  endurance being a
characteristic of nerve  fibers and neural  tissue.  It is claimed that most of
the nerve exhaustion is simply  muscular exhaustion in connection with the end
organs.  There is a point, however,  where nerve  fatigue may take place,
although this is more   true of  the central system and the end organs.  Even
if neural fatigue  is dependent upon  these it represents a condition that we
find in the  nerve,  in its connection with  the nervous mechanism.
     When a nerve is called into activity in the transmission of a  nerve com-
motion certain  phenomena are found depending on  the nature,  extent and
method of applying the stimulation.   From a psycho-physiological standpoint
it daes not matter very  much what the physical  properties of nerves  are.
Nerves are irritated by all  kinds of mechanical stimulation resulting in  pain
from excessive stimulation  in the case of the sensory nerves and  in  contrac-
tion in the  case of the motor nerves.   Compression may be so increased as to
suspend the power of conductivity if the shock  is sudden.  It is  not known
whether nerves  have  any heat in themselves  or whether  they can conduct
heat,  but heat has an important stimulating effect.  Heat  seems to hasten
the death of a nerve when  removed from  the  body and cold seems to  retard 
41
death.  A great many of the 3hemical substances destroy the nerve, although
changes  in the amount  of water in the nerve composition  seem to affect the
nerve functionality,  the decrease in water intensifying irritability, increasing
contraction until tetanus results.  Nervous stimulation by electricity  has the
same effect on the nerve as in muscle  although in different  degrees.   Nerve
conductivity of an electric   impulse  is about 15 times that of  pure water.
Constant currents if they remain steady do not excite  the nerve,  whereas va-
riations in the  current do excite  the nerve.  The irritation  depends on the
direction  in which the  current goes and also on the strength of  the current,
increasing with the increase in  strength till  a maximal point is reached  It
also depends on the  nerve length subjected to  irritation and also on the angle
at which the application of the  stimulus is  made.   If the current flows ex-
actly at right angles to  the nerve axis it does not stimulate tthe nerve.  It is
considerably influenced by the length of time  during which the current is ap-
plied, no effect being found unless the stimulus is applied for at least .0015
of a second.  When a  nerve is subject to the influence of  a current, the ef-
fect of stimuli applied to any part of the.nerve is increased if we estimate  the
result from the sensations  produced in  connection with the muscles.  This
alteration  in the condition  of the nerve from its  physiological  function is
called its electrotone.   Nerve  irritability when the nerve  is subjected  to a
constant current  is increased at the point where the current leaves the nerve
and it is lessened at the point where the current enters.  Conductivity, how-
ever, is altered in a  different way, for when the nerve is electrotonic, the con-
ductivity   is less at  the point  where  the current leaves than  at the.point
where it enters the nerve,  indicating a  difference between  the beginning of
the nerve  impulse and its transmission along the nerve.
    When the nerve commotion is transmitted through a nerve,  certain pro-
cesses are originated within the nerve itself.   No visible mechanical changes
take place  in the nerve,  although certain changes are found in the nerve cells
as the result of irritation,  prolonged  excitation producing  shrinkage of the
cells in connection with the nucleus and the protoplasm estimated  as amount-
ing to 25 or 30 per cent.  No appreciable thermal changes are found  associ-
ated with  nerve   excitability.  Certain chemical changes, it is claimed, take
place, the nerve  after prolonged exertion or stimulation becoming'acid in reac-
tion.  Some electric phenomena,are also said to arise in connection with nerve
excitement.  By  dividing  a nerve and then  applying  an  electrometer the
normal nerve surface is positive to the cross cut surface.   A current of  rest
flows from the cut end in the direction of the  equator indicating the existence
of electrical variation when a nerve  is stimulated.
    In regard to  the principles that  regulate nerve  conduction almost noth-
ing can be said.   The first principle may be stated as, that conduction takes
place in all nerves similarly.  In trying to compare  the amount of stimulus 
42
 with the amount of the resulting commotion, the only available means is elec-
 trical measurements.   Measured  by the  result  in muscle  contraction it is
 found to be in direct proportion to the stimulus.  Notable exceptions  to this
 principle have been observed.  When the stimulus is increased beyond that
 necessary to secure the initial maximal contraction, there is a second phase
 of the  contraction during which a  second maximal is attained;  sometimes
 this second phase  represents a decreased contraction,  followed by another in-
 crease.   Variations are  found in excitability among different  nerves and
 even in the different parts of the same nerve,  the entering current affecting
 the lower part more and the leaving current the upper part of the nerve  more.
 The nerve commotion passes along the nerve as undulations but in order to pre-
 serve the undulations and prevent their combination, there must  be an inter-
 vening period between  each  stimulus  of about 1-100th of a second.  If this in-
 erval is not preserved they will combine, resulting in tetanus.   By preserving
 this interval the united results may be summed up forming a summation of stim-
 uli in connection with the nerve,resulting in a summation of muscle contractions.
 In regard to the speed of  nerve conductivity Helmholtz says that the speed
 of impulses in the  motor nerves  of frogs is about 86.G  feet per second, later
 researches in connection with the pendulum myograph gave about 89.6.   Un-
 der changes of temperature in the case of the human subject a speed of  OS to
 300 ft. per second  may be obtained.   In the  case of the  sensory nerves the
 speed is placed at  98 to 130,  the speed uepending upon temperature,  nerve
 length and the electrotonic nerve condition.   In  the  spinal cord and brain
 the speed is much  slower than in the nerves on account of the increased com-
 plexity of  the organs and the  number of side paths along  which impulses
 may pass.   In the  cord the rate of  sensory impulses  is placed at 26 1-2 ft.
 and the motor from 36 to 49 ft. per second.  The tactile sensations arise soon-
 er than pain sensations as in the  case of a burning hand, the former being
 about 89 to 160 ft.  and the latter 26 to 48 ft. per second.  The   slightest in-
terference with neural  integrity,  as in the case of a section,  even when the
divided ends are kept close together interferes with the neural integrity of con-
 ductivity.   The neural impulses cannot leap over spaces,  so that to preserve
the conductivity there  must be  neural integrity.   In the  spinal cord and
brain we must remember that the same continuity may not be  necessary as
in a nerve, because in passing through the cells considerable  modification of
impulses takes place and several paths are open for them.
    The Central Nervous  System.  Beflex action arises when  one nerve
is stimulated secondarily  through a centei' by a primary  stimulation in the
 case of another nerve.   Where the primary stimulation originates in a cen-
 ter the action is automatic.   Of this action we  know nothing and the term
simply indicates want  of knowledge on the subject,  As  distinguished from
 these we  have  the voluntary  action  associated  with  the exercise  of will. 
43
There may exist various kinds of  reflex  actions—co-motor reflex,  in which
two motor nerves  are united through a  center; reflex-sensory  where an im-
pulse originating in a motor nerve may be communicated to a sensory path;
co-sensory reflex exists where one sensory nerve is united with  another sen-
sory nerve through a central organ, as lor example, the influence of  light on
looking at the sun producing the irritation resulting in sneezing.  The most
common is the  sensory motor in which the sensory represents  the primary
stimulation and  the motor the secondary through  the center.  The spinal
cord is particularly  adapted to  perform the function  of reflex  centers.   In
connection with the brainless frog we have a reflex nerve machine, the spinal
cord being  preserved alive but  entirely  severed from the brain below the
medulla,   By irritating the side of the frog in this condition there will  result
muscular  movements.  The same experiments have been made in connection
with brainless mammals,  the difference being that immediately after the  re-
moval of  the brain the   responses  are very feeble,  whereas  if  the animal is
kept alive the reflexes become strong.  The age, sex and training of the ani-
mal also  influence the   response.   If stimuli are  applied suddenly  a much
readier  response is given than if applied slowly, and the repetition of stimuli
gives the  most effective response. The nature of the response  depends on the
condition  of the spinal cord and also upon the local  area to which the stimu-
lus is applied.  The  stimulation of a sensory nerve  with a  slight  degree of
stimulation produces reflex movements originating  on the same  side of the
cord as the sensory  stimulation takes place;  if the stimulation is increased
reflex movements may originate from the opposite side;  while a still further
increase in  stimulation  may produce responses on both sides.   The  neural
impulse when it passes into the cord is diffused among the cells and fibers at
the  point of  entrance,   then  it  passes to the  other  side  and finally it is
found on  both sides.
    The spinal cord gives origin to certain automatic  impulses  such as those
associated with muscular tonicity.   This is  questioned,  however,  as all the
muscles are not affected at the same time  and in  the same way, certain sen-
sory impulses in  connection with the skin, even in the brainless frog produce
the tonic  action reflexly.   In some regions of the  cord the motor and sensory
tracts are more closely  connected  than in others,  these  regions being called
the reflex  centers, being dependent  largely upon  individual  habits and specific
functions  of the animal as well as the individual  eccentricities and the previous
functional use of the cord, such as the vaso-motor,  micturition, defaecation,
etc.  centers.   The spinal cord gives a quicker response than when the stimu-
lation takes place through  the brain, because the connection of  the cord with
the brain  involves the  inhibitory  function  of  the brain.  For example the
heat center is in  the upper cervical  region, whereas inhibitory  and  acceiera-
tory centers are in the brain, the cord function being  inhibited or augmented 
44
 in connection with the brain centers.   While therefore the  cord has its  own
 independent  functional powers it is regulated  by the higher brain  centers-
 This is inyolved in the fact that in most of the ordinary activities of life these are
 involved, spinal reflexes, motor reflexes that imply brain  action in connection
 with the sense organs and the special modifications that arise from the distinctly
 conscious acts of volition.
     In the brain the complexity  of function is greatly  increased, the  brain in
 the  human subject being so complex and complicated.   Despite the  difficulties
 arising from the difficulty of experimenting on the human brain much progress
 has been made through  pathology, clinical observations  and surgical  experi-
 ments in cerebral localization.  It is here that the relations  between the body and
 the  mind bring as  closely to  the localized areas of  the  brain.  The  brain may
 be divided into (1) a sensitive area, including all above the cord and below the
 cerebral hemispheres,  and  (2) a conscious area in the cerebral hemispheres.
     (1)  In the sensitive area  we find next  above the spinal cord the medulla
 whose functioning represents the vegetative and lower  animal  life.  The reflex
 motor functions of  the cord are extended into the medulla,  especially in con-
 nection with the heart, vaso-motion, respiration, deglutition, etc.   Automatic
 impulses originate  in the medulla in connection with the blood  circulation reg-
 ulating breathing,   heart  rhythm  and  the blood  circulation.  This  minute
 substance is  full of centers, the  respiratory and vaso-motor  being the  most
 important along with the cardio-inhibitory center. Associated with the medulla
 are the functions of co-ordination the upper portion  being  closely  connected
 with the gray matter of the third ventricle and the semi-eircular canals in con-
 nection with  body equilibrium and the co-ordination  of muscle  movements.
 Hence its reflex  character  is  of greater importance  than its  capacity  to do
 under voluntary control, all of the  centers being more or less  associated  to-
 gether.   Above  the medulla  and  below the cerebral  hemispheres we  find a
 number of varying brain portions that are of considerable  importance.  By the
 removal of the cerebral hemispheres in  the case of the frog or  pigeon inter-
 esting results have been obtained.  It is found that the  animal deprived of
these hemispheres is more or less mindless,  while it  does not  appreciate  mag-
nitude or relation to other bodies except through contact with these  bodies
having no fear and showing no power  of  recognition.  The psychic qualities
seem to be entirely absent.  All of the intermediate parts  between the  medulla
and cerebrum  are   related in function.  They act  independently to  a certain
extent,  and in certain cases they can perform each  other's functions,  having
largely the same sensory and motor connections.   They are  all united  in the
formation of the central part of the nervous mechanism which acts as  co-ordi-
nating centers in connection with the impulses of the special senses and govern
 the motor mechanism.   In the  processes of adjustment  and readjustment in
connection with the animal body they play a very important part.   The cere- 
45
bellum  seems to be concerned in the  adjustment of  the opposite  sides of the
body so as to produce equilibrium,  the sense impulses of sight and touch furn-
ishing the external stimuli that  notify the brain of the body position and rela
tious.  The semi-circular canals are intimately associated with the  cerebellun
in discharging this function.  The corpora  quadrigemiua are united with the
cerebellum, pons and medulla in promoting  equilibrium and sustaining  the
normal body movements,  particularly  in connection with  visual  sensations.
The optic thalami  seem to be associated with the  corpora quadrigemina in the
adjustment  of body  movements in  connection with  visual  sensations and ac-
cording to Ferrier with  muscle  movements in connection with tactile  sensa-
tions.  The corpora  striata have some special  function to  discharge in  the
co-ordination of motor impulses as these originate in  the cerebrum  and cere-
bellum, while Ott regards them  as heat centers,  or regulators of the tempera-
ture of the body,   The nervous matter on the floor and walls of the third ven-
tricle has  something to  do with the equipoise  of the body  in  co-ordinating
motor impulses and  sensory impulses especially  of  touch, and of  sound in
conjunction with the semi-circular  canals, as  well as from   impulses  that arise
from visual changes.   Thus all these intermediate organs between the medulla
and the cerebrum have  some special and  general  functions in connection with
co-ordination as between the impulses originating iu the special  sense  organs
and the muscle movements.
     Normally all these functions are subordinate to the cerebrum.  The indi-
vidual organs represent parts of  an inter-related  whole  which corresponds
with the psychic phenomena of motion resulting  from the  sensory  impulses.
Even in the lower animals when the cerebrum is absent, although  these inter-
mediate parts perform their functions independently,  they do it unintelligentlv
indicating that the psychic qualities of intelligence, feeling  and volition can be
mediated through these lower regions, but  only do they possess  psychic quali-
ties when  they sustain their  normal relations   to the  cerebral hemispheres.
Hence these have an important psychic  bearing   upon the  phenomena of  con-
sciousness and not  incorrectly did we  distinguish between the  sensitive  and
the conscious functions in connection with  the lower and upper Drain.
     (2)  The Cerebral Hemispheres.—We know that the conscious phenom-
ena are very intimately related to the body  organism.  This we gather from
the fact that injuries to certain  parts of  that body  organism involve  mental
conditions that are abnormal.  It is  more difficult to  localize these changes in
connection  with nervous  matter.   We  cannot judge directly regarding the
nervous system but must depend on indirect  indications of changes  taking
nlace in the nervous mechanism.  In the normal  condition  of the nervous sys-
tem there is no tension but everything seems to run smoothly, so that it is only
when we find abnormal conditions we  have any means of   localizing the vary-
ing sensations.  In the case  of the central  nervous  system it is  beyond ordi- 
46
 nary experience and observation so that we  are unable  to gain any  direct
 knowledge of the action of the brain.  In the ordinary life  there is nothing to
 indicate the importance of the central system. Among the ancients very little sig-
 nificance was attached to the brain. Alcmaeon spoke of it as the general rendez-
 vous of the senses within the body while Aristotle regarded it as simply a lubricat
 ing reservoir for the eyes.   We suppose that there exist in connection with the
 brain certain of the conscious phenomena intimately associated with the think-
 ing processes.   Attention is attended with a strain upon the eyes and the other
 sensations arising from the special senses are localized in connection  with the
 brain.  When thought or attention is concentrated the feeling is identified with
 the head, indicated by the attitudes of thought,  meditation,  and anxious con-
 sideration.   The different senses are  popularly associated  with a brain center
 in such a definite way that  the brain  is popularly looked on as the  seat of the
 most intricate processes of  the  psychic  experience.  It is this that led to the
 idea that the soul is seated  in the  brain and the particularly  neurotic character
 of the modern individuality gives added force to  this conception.  These how-
 ever are very indefinite indications of what physiological  researches have tried
 to unravel,  namely, the  localization  of the  cerebral  functions.  There is no
 doubt that the brain  is of the highest  importance,  not only  to the psychic but
 even to the ordinary physiological  life.   The human brain  has a powerful in-
 fluence upon human consciousness.  Without the normal  blood  circulation
 with its abundant supply of  0 the central system could not discharge its normal
 functions.   Hence the amount of  blood that is utilized in the brain represents
 about 12 per cent of the entire blood of the body while the  weight of the brain
 would not amount to more  than 2 1-4 per cent of the body.  If the  blood cir-
 culating in the brain is impure, especially  if certain  chemical substances are
present,the conscious activity is greatly interfered with. To increase the rapidity
 of the circulation by the use of stimulants has a decisive effect upon the rapidi-
 ty of thought.  Changes  in the  temperature of the  brain are associated with
 mental changes, the changes in temperature during wakefulness being  accom-
panied by psychic activity.   Even without sensory  impulses psychic  activity
develops a changed temperature.   It  has been found that  where strono- im-
pressions reach the brain there is a variation of  temperature represented  by
rise and fall in connection with the different areas of the brain,  so that  there
is a localization of these  variations.  In the occipital  region it is found  that
the greatest rise in temperature exists, increasing more in the case of emotional
excitement than in the purely sense  stimulation.   This  seems to indicate the
localization of functions and areas  in the brain.  It is found that where psychic
activity is  great there is  an accompanying  increase  in the amount of waste
matter thrown off; indicating the metabolism of nervous tissue  in the  conver-
sion of potential into kinetic energy.  This means that increased psychic activ-
ity represents an increase in the cerebral cell activity in connection with the use 
47
  of the phosphoric compounds.  Thus  the brain mass becomes more or less al-
  tered during the psychic activity.
      A comparison of the structure and size of  the brain  in  different animals
  indicates the relation of the brain  substance to  mental action.   This indicate,
  the place of the species in the scale of intelligence.   Great variations are found
  in the size and structure of the brain so that no general principles  can be laid
  i°WD; •„ ^r 1S S ^^ deVel°Pment  °f  the  b^in during  the first years of
  the child life.  At the period of  birth the brain  weight to the body  weight is
  in the male according to Tiedeman  1 to  5.85 and in the  female  1  to 6.5   At
  the beginning  of  the third year the ratio is 1 to 14 and one  year later  1 to
  18   There is a gradual increase till about 25 or 30 years  after which  it begins
  to decrease till  old age, about the rate of  1 oz.  for every decade of life   Much
  interesting work has been done in  comparing  the weights of the brain  in the
  different races.  The European and  North American brain varies in  the male
  from 44 to 55  ozs. and  in the female  from 40 to 44 ozs.  The sexual distinc-
  tion is not  simply one of size in comparison with the  body weight, the male be-
  ing about 10 per cent heavier.  Considerable variation   above and  below these
 averages is found in actual experience, without any indication of unusual men-
 tality or  exceptional inferiority.  Brains below 30 ozs.  are usually  associated
 with imbecillity, accompanying the mental weakness  being) a'body  weakness.
 Maudsley says  the superiority of the human subject mentally  over the animals
 is connected essentially with man's capacity of a greater  variety of muscular
 activity.  To such an extent does he think this is so that if  man with  a nor-
 mal brain were  deprived of all the movements  of face,  hands and limbs, be
 would fall into  idiocy.. This  brings out  the close relation between mind and
 body in strength and weakness.  Insanity on the other  hand is not  necessarily
 associated with an altered size of brain, although there is often an abnormally
 large brain found in the insane.   We must remember however that weight is
 not an absolute test.   More  reliable results are  obtained by comparing the
 development  of the cerebral hemispheres in man with that in the lower animals
 particularly in regard to the cerebral convolutions.   As the  convolutions be-
 come more  numerous and complex we rea"h a higher degree of mental life   In
 the development of the human brain from the embryo we find a correspondence
 between the embryonic form and the forms  of fishes,  birds,   etc.  Amono- the
 fishes there is a small cerebellum and cerebrum;  among the amphibia  the cer-
 ebral hemispheres become  more  developed; while in birds  the hemispheres
 have developed  their characteristic mantle form over the  lower brain.   In the
 higher mammals we find occipital development very complete and frontal devel-
 opment more perfect, with  an increasing complexity of convolution develop-
 ment. As the  mantle devolopment becomes more perfect it spreads out over the
intermediate ganglia, the cerebrum leaving behind and decreasing the import-
ance of these ganglia,  indicating the great importance  of the cerebral hemi- 
48
 spheres  in the higher intelligence.  Meynert suggests  that  the  entire  cortex
 cerebri represents a field of projection upon which all the sensory impulses are
 arranged as they come from the periphery, forming the  physical  basis  for the
 distribution of these impulses in connection  with the motor tracts   It cannot
 be said that the cerebral convolutions correspond with the intelligence displayed
 by all the scale of  animal life, so that we are unable to say that  the  less civil-
 ized races have less development in the cerebral hemispheres.   In the imbecile
 there is  poverty of convolutions.   Meynert thinks that in the peduncles we
 have two parts, the one tegmentum in direct relation with the optic thalami and
 and the corpora quadrigemina and the  other  crusta in  relation with  the cere-
 brum through the corpora striata.  As the cerebrum becomes greater compared
 with the  the corpora  quadrigemina, the latter  part of the crura must be larger
 than the former so that the crusta represents   the measure of psychic  develop-
 ment and as this is more fully developed  in man than  in  any other  animals,
 Meynert regards this as the index of mentality.
     Here we find at least the  importance attaching to the cerebral hemispheres
 from the standpoint of psychic activity.  The neural  impulses  pass from the
 periphery along the nervous tracts to the brain;  and in so far as  these are
 converted into  motion they  represent  ideation and conation.  In  this way
 physiology points out the convolutions of the brain as  the ultimate  physical
 basis of both the psychic and physiological life of man, the sensory  and motor
 impulses finding a general meeting ground in this cortex cerebri.   As this is
 cutoff  from the periphery,   sensory and motor impulses are likewise cutoff
 so that the psychic  and physical life are divorced  from each other.   In the
 brainless frog a number of reflexes are possible but without psychic relations;
 if the intermediate brain ganglia are left there is  a definite psychic  element
 in activity.   This has  led to  the  suggestion  that consciousness and its pur-
 posive features are  associated with  the spinal cord  and brain  ganglia, but
 many of  the purposive  actions of the human life,  such as walking,  eating,
 breathing are not necessarily connected  with conscious  mental states.  The
 cerebral hemispheres in man  represent the only parts of the neural mechan-
 ism  associated directly with  consciousness.   Any  localization  then of con-
 scious activities must be in connection with the cerebrum.  Below   the hemi-
 spheres  the nervous system   is not  capable of forming  a physical basis for
 psychic activities.  To say that certain phenomena  manifesting purpose may
 be exhibited after decapitation does  not import into the spinal cord the ele-
 ment of mentality.  The action of these parts of the nervous mechanism de-
 pends upon the relations established between the  different parts of  the sys-
 stem by habit.  In the case of  the lower animals we know little of the rela-
 tions of consciousness to the  physical life, all that we know  being the appli-
cation of  our own conscious experience to their actions.   If we judge from the
 human life, however, many of the vital  phenomena are not  distinctly con- 
4!)
  scious.  As the cerebrum in animals develops there is a greater influence de-
  veloped in  connection with all  the physical activities.  Hence as the cere-
  brum becomes more aeveloped it is more closely related to the entire physi-
  cal and psychic life, so that if it is lost, it represents a greater loss than if the
  cerebral development had been  less complete.  Hence a frog, brainless  can
  do without its brain more than a dog could do deprived of  its brain   and so
  on as we advance in  the scale ol intelligence.  The more  complex  the rela-
  tions established and the more complete the cerebral control,  the  greater is
  the loss of it.   As the  functions become co-ordinated in man,  on a^lower or
  a higher scale,  the psychic activity is more or less intimately connected with
  these  functions,  so that  habit  which is psychic  becomes  phvsiolo-ini
  Hence, the tendency to explain the more complex body activities on a purelv
  physiological basis.   The chief result of the destruction of the cerebral hemi-
  spheres is the elimination of the psychic element from the life, at least in the
 higher  mammals including man, so that the real physical basis of mentalitv
 is in the cerebrum, or rather in the cerebrum as it forms the  ultimate crown
  of the   entire neural  mechanism  and  muscular organism.  The  cerebrum
 which  represents the   most  advanced  development of the neuromuscular
 mechanism is not simple but complex.   It consists of different parts charac-
 terized by want of homogeneity, consisting   of multifarious forms and  rela-
 tions established among the different parts.   The question is, can we local-
 ize these parts functionally?
     On general  physiological  principles there  seems to be an  a priori pre-
 sumption in favor of localization of functions.   In the cerebrum we  find th
 same neural  elements  as are found  in the rest  of the  nervous  mechanism.
 The  combinations  and associations  may be different  and this niav result in
 differences  of functions  but the  substance is essentially  the same.   As we
 have seen localization is carried out in the intermediate parts of the brain  and
 this suggests the possibility  of localization in  the cerebrum.  The doctrines
 of localization are not  yet a quarter of  a century old.   Older  attempts  met
 with no success and the fact that large parts of the brain could be lost with-
 out any appreciable loss of sensory or motor functions assisted in discrediting
 any attempts to localize.  The great physiologists of the first half of this cen-
 tury decided  against  localization claiming  that the different parts  perform
their functions  in relation to the  entire brain.  Broca was  the first to  sug-
gest localization in connection  with articulation associated  with the frontal
lobe.   Meynert claimed  that   the anatomy and physiology of  the brain sug-
gest that the anterior part of  the cerebrum is motor and the posterior  senso-
ry in function.   The experiments of Hitzig and Fritsch   mark the first posi-
tive advance in the science of localization.  They experimented upon the dog
by electricity, finding that the cortex  cerebri is subject to electrical irritation,
that the motor parts are found on  the anterior portion and the  non motor on
f?7 
50
the posterior part of the cortex.  The stimulation  electrically of the niotor
areas produced muscle contractions on the opposite side of the body.     ey
indicated five motor areas, for the neck  muscles,   for the  extension of the
front limb, for the rotation of the fore limb, for the hind limbs and the mus-
cles of the face.   Ferrier followed out these experiments in connection with
the monkey.
    We do not have a physiology of the cerebral hemispheres, because of the
fact that they are so much hidden from observation and so closely connected
with every other function of the body that they cannot be discussed separately
or subjected to observation.   Investigation  seems almost impossible  in con-
nection with the physics and chemistry of  the brain, so that  the physical
and psychic facts that are available in discussing the localization of areas are
most complicated. The evidence has been classified under three heads, exper-
iment, pathological, and anatomical.   In connection with experiments  there
are available, stimulation and destruction of the parts.  By stimulation the
attempt is made to associate certain muscles with  certain definite areas, but
this only indicates a relation between  the muscles and  the localized area and
does not prove that these  areas are solely concerned in  muscular   actions.
The stimulus commonly used  is electricity and objections  have been taken
that electrical diffusion takes   place so that we are unable to say that the ef-
fect is limited to any definite area.  Hence, it is claimed that by stimulating
certain cortical regions, these regions act simply as conductors of the impulse
to other regions of the brain,  particularly in the basal part.   Ferrier answers
this by saying the stimulation of the basal ganglia can be carefully estimated,
so that the effect of stimulating these  ganglia and the cortical regions can be
compared.
    By administering anaesthetics it  is  found that cortical excitability is les-
sened or lost.  This in addition to the  fact that if the gray matter on  the sur-
face is removed the stimulus requires to be stronger in order to excite motiv-
lty seems to prove that somehow the cortical substance is connected with mus-
cular phenomena.  By the  removal of  certain parts of the brain it  is  found
that there is an interference with or loss of motion on the part of certain mus-
cles.   This seems to indicate the relation of these parts to the  muscles in-
volved. This cannot be applied absolutely, because we do not know the effect
upon the brain substance itself produced by extirpation, nor can we follow the
changes taking place  in the brain as  a result of extirpation.   The fact that
these experiments are made upon the  lower  animals lessens their value in ap-
plication to man, as there is not an absolute correspondence between the brain
areas in man and these lower  animals,  and the psychic experience of man does
not correspond with that of the animals so far as known to us.  The pathologi-
cal evidence is of great value because here it bears upon the human brain when
accident, disease and even the  hand of  suicide and murder  open up for exam- 
51
ination the different brain areas.   Difficulties arise because the accidents do not
often secure clean cut portions and the lesions involved do not always represent
complete conditions as to the relation  between sensory and motor disturbances
and the brain  area  involved.  Post-mortem pathology  is  not yet scientific
enough to enable  the  psychologist to get clear and definite oases.   Hence the
evidence is conflicting.  With the advance of modern  surgical science this  is
being remedied, because in large numbers of cases, with  the present imperfect
knowledge of localization,  surgery is skillfully relieving many brain conditions
and thus demonstrating its ability to reason from  the disturbance, which is  a
symptom to the lesion that is the cause.   Physiology and psychology will profit
by these discoveries.
     Anatomy can aid only  in a general way in the work  of  localization by
pointing out the  increasing complexity  of the human brain areas  in compari-
son with animals.  Comparative anatomy can trace  out the  increasing com-
plex areas in the  ascending scale  of auimal life until  it comes close to  man.
Histology  expands this   evidence  by tracing out  the relations of  different
parts  of  the brain.   Microscopy and micro-photography  lend   a  helpful
hand  to histology  in  following up  the  course of the  nerve  tracts into the
cerebrum.  These fields of investigation have  presented a  confused  mass  of
evidence which requires to be carefully analyzed,  compared and  classified  in
order to gain any definite results,  and  only  when all of  these evidences unite
with more or less unanimity do we get certain results.   The first general con-
clusion reached is, that the cerebral hemispheres do not represent a single mass
that plays a part in every psychic  function, but  that they represent a large
number of psychic organs, every one of which has a psychic functioning with a
more or less intimate relation to the physiological  functions of parts or organs
of the body.  The second general principle is that in the attempts to localize
cerebral areas much of the cerebral hemisphere remains as yet unrelated to sen-
sory or motor activities.  There may be the removal of considerably large parts
of the cortical substance without interfering with any of the normal body func-
tions.   The American  crowbar case,  in which a  bar of iron, 3 feet 7 inches
long and  1  1-4 inches in diameter, passed  through the brain of a young man,
entering at the left angle  of the jaw  and passing out at the top of  the head,
without interfering  with sensory motor activity,  may be taken as an illustra-
tion of this point from the pathology of the subject.  This suggests the fact
that all the defenders  of  localization  lay emphasis solely on cases that favor
their theories of  localization  without attempting  to consider  these  negative
cases that  oppose  their theories.   This does not, however, destroy the work
done in localizing such regions.  It has already  borne fruit in modern surgical
cases for in a number  of  cases lesions  have  been removed  by the aid of our
mper'fect  knowledge of localization.  This indicates the possibility of  laying
down certain positive results while we await fuller developments. 
     Recent  experiments have increased rather  than lessened  the  difficulties
that  arise in  connection with the cases  in which large portions of the  brain
substance have been destroyed without interfering seriously either with physi-
ological or mental functioning.  Yet the evidence amassed in  connection with
the three sources of evidence seems  to present a basis  for a more or less con-
sistent theory  of localization.  This theory is  most definite  in regard to the
areas associated  with the motor  functions.   This region is found around the
Rolandic fissure, taking in the  anterior and posterior gyri centrals  and their ex-
tension on the median brain surface  in connection with  the lobulus paracentra-
lis.  In the first  experiments  conducted by Fritscu and  Hitzig we find the
localization of five areas in connection with the cerebrum of the  dog, the stimu-
lation of which resulted in certain movements. These are, areas  for the muscles
of the neck, at  the middle of the   praefrontal  gyrus at the  beginning of its
declivity; for the  extensor and adductor muscles of  the fore limb  at the ex-
tremity of the post-frontal gyrus close to the frontal fissure; for the flexing and
rotation of the fore limb back of the last; for the hind limb in the  post-frontal
gyrus nearer the  median line  than the two preceding; and  the center for the
face in the median part of the gyrus above the Sylvian fissure.  Ferrier by the
use of electrical stimulation in connection with the monkey  found the centers
of motion in connection  with the gyri  centrales and in the adjacent part about the
Rolandic fissure.   Recent experiments in connection with electrical stimulation
have confirmed most of these general results.  It is claimed by some that some
of the smaller areas become  irritable after stimulation  for a time while  others
lose their excitability after stimulation.   In the case of the larger areas  found
in connection with muscle groups it is claimed that certain small portions of the
cerebral hemispheres correspond with the origin of the  nerve fibers  controll-
ing the muscle groups.  Thus as Exner has pointed out  there is an  absolute
and a relative field for the motor actions so that the fibers which  originate at
minute cerebral spots proceed to the  lower portions of the brain.
     By the destruction  of these  regions in  connection  with which   muscular
movements  can be  stimulated it is  found  that there  results  an interference
with the muscle movements.   Hitzig and Fritsch made use of extirpation  as a
means of  confirming the  stimulation experiments.   Munk  experimented very
carefully upon dogs, extirpating  circular layers of brain  substance   3-5 of an
inch in diameter and 1-12 of an inch thick in connection with the surfaces of
the parietal,  occipital   and temporal lobes.   He concluded  that by drawing a
line from  the sylvian fissure  terminal in a vertical direction towards the siekel
like falx between the cerebral lobes it will define an anterior and posterior sphere
corresponding with a motor and a sensory region.   His  general experiments
indicated that  destruction of   portions  anterior and posterior to  this line re-
sulted respectively in motor and sensory disturbances.   The  definite  areas he
discovered correspond generally with the conclusions of Hitzig and  Ferrier 
53
three of his regions, for the head, the arm and the leg being  identical with the
others discovered before.   By extirpating  the area of  the fore limb he  found
abnormal conditions in connection with the limb so that stimulation applied to
the limb even strongly will not call forth any response,or only a reflex result,so
that according to Munk  there  is no cerebral  action  in  connection with this
limb.  Munk rejects the theory  that these cerebral regions are  distinct  motor
areas, that is having the function  of moving in  connection  with volition,  but
he regards them as feeling areas, because the motor action of the higher centers
depends on  the feelings arising  in connection with the  different tactile  sensa-
tions.  From this he concludes that the removal  of the  area  mentioned  before
interferes with the sense of feeling and  may he repaired as soon as restitution
from injury takes place.   In this he is supported by Schiff who claims that the
loss of motion arises in this case from the absence of the tactile sensations. This
he claims is proved by the  non-sensibility of the limb on  its  cutaneous sur-
faces to stimulation.  Goltz claims that extirpating the  cerebral  substance in
the frontal lobe  produces  an indifferent activity in the  limbs on the opposite
side of the body accompanied by diminished tactile sensation  while the mus-
cular sense  is destroyed,  so  that there  is not any permanent loss  of  motivity
in the  muscles.   His idea is that the greater influence  is  exerted  on the psy-
chic element by the removal of a part of the brain  substance.  Bechterew claims
that on extirpating any extensive  part  of the  motor areas the  motivity is not
lost but the adaptive movement  is lost in the extremities so  that  they  cannot
be used as hands or feet, indicating the idea that there  is a separation of these
movements from the purposive force of the will.  More recently  Horsley and
Schae.fer have continued the invesiigatious in connection with localization their
conclusions being the most advanced in this new science.
     It is difficult to attempt to frame a theory upon  such  seemingly indefinite
and contradictory results.   It would seem that we may take it as settled, how-
ever, that  there is a  region that may  be  called  motor, any  interference with
this region  producing a muscular disturbance, the loss being rather that of the
psychic or intelligent power of  adaptation  in the use of   the  muscles.   Asso-
ciated with  the  loss of a large  portion  of the cerebral  substance   we find the
loss of the  tactile and  muscular sensations that  are necessary to the localiza-
tion of everything  external  to the mind, including the body and  external ob-
jects, so that movements  cannot be adjusted.  In other words there is a loss of
voluntary expression  in connection with  movements and a more  or less com-
plete interference with sensation, perception and volition.  Several  explana-
tions have been offered  in regard to the effect of this  loss of sensory-motor
capacity.   Some claim that the  areas extirpated are purely motor, so that there
is an impairment of the relations between the cerebral substance and the pro-
jection  fibers.   Others like (joltz  claim that  the loss is   sensory, the  motor
disturbance  being a manifestation of this sensory loss, so that  the animal  can 
54
 no longer use its extremities on account of loss of sensibility.  It may be ex-
 plained from a psychic  standpoint, due to the impossibility  of keeping before
 the mind the mental picture of the body and external objects so as to  localize
 them definitely, involving an interference with the association fibers.  Thus  it
 is claimed that by removing the association fibers  without impairing the  pro-
 jection  fibers, the loss of  motivity is quite as  complete, indicating that any
 disturbance whether sensory or  motor interferes with  the cerebral  psychic ac-
 tivity, so preventing its control of the  muscles.  In fact Goltz claims that any
 interference with  the brain substance that is extensive   interferes with this
 psychic control and therefore diminishes but does not destroy the sensory and
 motor functions.  Thus  certain   areas of the  brain are of special  significance
 in the muscle movements, these  areas  being found in  the region  around the
 Rolandic fissure and in the paracentral lobule.  In connection  with this region
 there is an anterior region and a  posterior, the former  being motor  and the
 latter sensory.  This general region is divided into local areas  which are local-
 ized in connection with pathology because the experiments in connection  with
 the lower animals cannot be transferred absolutely to the human subject. There
 is a difference in the brain development in the lower animals and in man and
 exact localization seems to depend to a large extent upon the intelligence devel-
 opment, the forward development guiding and determining the localized areas.
 Pathology thus steps in  to mark out the application of the  general principles
 brought out by  experiment  in  connection with the  lower animals   to the hu-
 man subject.
     Here we have no  more careful or thurough examination  of pathological
 data than that  furnished by the work of Exner.   Out  of thousands of cases
 consulted he selected 169 cases that were  test cases, perfectly reliabl" and well
authenticated.   In analyzing the cases he  divided them into three classes, map-
 ping out those  he called (1) negative cases, (2) positive  cases,  (3)  percentage
cases.   In the first he found out the regions of  the cerebrum  not  associated
with sensory or motor functions.  The second class of cases indicated direct
lesions in particular regions and the disturbances associated  with  them.   The
third class of cases indicated the  degree of probability  arising from the dis-
 covery of certain disturbances  associated with  diseases  or lesions in certain
specified  areas, this probability depending on the result of the  majority of
cases bearing on the particular area.  As a  result of his  analytical  researches
he  found 20 cases in  which no disturbance followed  existing  lesions while
there were 67 lesions  in  the right and  101 in  the left hemisphere,  indicating
that his cases presupposed a  larger  latent field on the  right hemisphere    Th
result is that on the right hemisphere only the two  central  e-vri  th^ ,™
                                                          oj ' j Lite paracen-
tral lobnle and small parts of the inferior  and concave surfaces of  the occi     1
lobe represent an  active  field.   There is a much larger active field  on  the 1 ft
hemisphere. This is in line with clinical observations which point out  th 
any
  sibihty of large lesions in the frontal, temporal and occipital lobes without a
  interterence with sensory or motor activity.  It also confirms  the expenmen-
   al evidence from the lower animals that  the region around the figure of Ro-
   and is the motor area of the cerebrum.  Exner divided the  active fields into
   wo classes (1)  absolute in which  whenever  a lesion occurred  there was
  found a chs urbance of functions;  (2)  relative in which in more  than 50 ,er
  cent of the lesions there  was an accompanying disturbance.   In  connection
  with the upper  extremities he found that the absolute  field for the left arm is
  in the paracentral, anterior central and the upper part of the  posterior central
  gyr, and for the right arm in the upper parietal lobe and in part of the median
  surface of  the  occipital  lobe.   It must be  remembered the cerebral regions
  and the corresponding extremities are on opposite  sides.   The relative field
  for the left arm he found to include in addition  to the  absolute field  the pos
  tenor part of the three frontal convolutions and  the anterior part of  the parie
  tal lobe together with  the adjacent  median  surface, and for the right arm in
  addition to the absolute field the larger part of the parietal and occipital lobes
  This is in line with the fact that righthandedness is normal in man and that a
  larger cerebral area is devoted to  the activity associated with the delicate and
  intelligent movements of  the right arm.   In connection with the lower extremi-
  ties he found the absolute field for the left leg in the paracentral lobule," the
  upper  part  of  the anterior central, tne  corresponding parts of the posterior
  central convolutions and part of the  quadrate  lobule,  and for the  right ley the
  paracentral lobule, the upper part of the  posterior central convolutions and the
  upper part of the parietal lobe.   For the  relative field of the left leg he found
 the lower parts of the central and the posterior parts  of the  frontal0gyri with
 the upper parts of the occipital  lobe and the parietal lobules, and for the rio-ht
 leg in addition to the absolute field he designates the  parietal lobe, the median
 surface of the quadrate lobule and  the  cuneate   convolution.  This  indicates
 that cerebration  is less perfect in connection with  the lower  extremities,  indi-
 cating the fact that less psychic effort is devoted to the  lower extremities, and
 that the upper extremities represent a greater and more intelligent develop-
 ment.  According to this the great motor area is around the Rolandic fissure
 and in the paracentral lobule.  In  these  regions  and the adjacent  areas are
 localized the centers of more minute  activities, for example the facial area in
 the lower parts of the anterior central  and posterior  central  convolutions • the
 lingual area is at the   junction  of the middle and lower  frontal  and  anterior
 central convolutions; the muscles of the  head  and neck  in the central convo-
 lutions.   Other experimenters have confirmed the generalconolusions of  Exner
 Charcot claiming that the  cerebrum may be divided into  a motor and  non-mo-
 tor zone, the  former being limited to the ascending frontal  and parietal  gyri
and the paracentral lobule.  Added  to this is more recent surgical experience
which is aiding in definite   localization.   Horsly  has  divided the  arm region 
5(5
into four areas, uppermost the shoulder,  next  the elbow,  then the wrist and
last the thumb. Meynert claims that the sensory paths go more in the direction
of the occipital region and the motor paths towards the frontal region  of the
cerebral hemispheres, this being based largely on  the greater size of the motor
cells on the analogy of the motor paths in the cord.
    The  question is raised,   does not the motor  area correspond   with the
area of tactile and muscular  sensations?  It would seem from  the analogy
of the spinal cord and the lower parts of the brain, that the sensory and mo-
tor apparati are closely connected.  In connection with conscious sensations
it would seem that a close relation exists  between the delicacy of the sensa-
tions experienced  and the delicacy of  the motor activity  depending on the
will.  Pathology it is claimed negatives this idea because many examples of
motor interference exist without any sensory disturbance.   Exner claims that
the tactile sensations  have no absolutely  definite cortical  field, the whole
relative field of motor activity being included in the field of tactile  and mus-
cular sensations.   Hence, he claims that the cortical fields for sensation and
motion are the same, although the right  hemisphere is the predominant sen-
sory area, as the left is the prevailing motor area.   This  is  in line  with the
fact that motor disturbances are more generally  associated with the lesions
in the left hemisphere.  Thus the central convolutions with  the  paracentral
lobule and the adjacent parts represent the cortical field for the sensory func-
tions, these representing  the central areas of the sensory impulses originat-
ing in the muscles and  cutaneous surfaces of   the limbs corresponding with
the motor areas.  In connection with the interferences with sensory  and mo-
tor relations   there is involved a complicated  psychic condition,  which ren-
ders it difficult to separate the sensory and motor disturbances  from one an-
other.   It is  certain  that a very close  relation  exists between the two.  It is
probable  they are not identical  and also  that  the sensory  region extends
more posteriorly  than the motor, possibly including the motor,  certainly
closely related to the motor,  and taking in the gyrus fornicatus and  hippo-
campi, with the quadrate lobe and the posterior parietal convolutions.
    The sensory localization is more difficult because of complicated psychic
relations and physical mechanisms.  The experiments on the lower animals
are of little value here because we  have no knowledge of the facts of conscious-
ness in these animals.  It is possible,  however, to apply the  results of exper-
imentation  in connection with  the  facts discovered in  human  pathology.
Particularly the experiments of Munk are so careful that they  form the basis
of application to the human sensory impressions.   Ferrier has localized  the
visual centers in the gyrus angularis and the occipital lobes.   Munk localizes
the sight area in the  occipital  lobes in the upper  and posterior part, claiming
that the gyrus annularis  is associated with the tactile sensations  of  vision.
According to Munk  the extirpation of   the sight center  in the dog produces 
57
psychic blindness,  that is, it is not able to transform the visual impressions
into mental  pictures.   It does not lose sight;  as it can regulate its  move-
ments by sight but it has no psychic capacity to associate external objects or
beings with its former actions.  If this extirpation  takes place in both hemi-
spheres the psychic blindness is  permanent.   From  this he concludes that
the sight center is associated with visual pictures, the occipital lobules being
associated with sight perceptions.  Pathology  seems to get from these ex-
periments the fact that on the convex surface of the occipital lobes and pos-
sibly on adjacent parts of  the lobe and the cuneate lobe are  to be found the
visual regions.   According to Exner the upper part of the first occipital con-
volution is the most important visual area,  the rest of the occipital convolu-
tions, the cuneate and  quadrate lobules being less important.  It would  seem
that the  sight areas are largely  and  widely distributed over  the cortex, so
that at different points the sight  impulses may be cut off produciug  psychic
blindness.   This may arise from interference with the connection  of the visu-
al perception and the other psychic perceptions or an interference with the
visual perception  alone so that  there  may be a corresponding cerebral dis-
turbance in the regions  representing  the projection and  association fibers.
In this case a large  area of the brain  in the occipital,  parietal   and frontal
lobes is  associated   with vision.   The attempts to  subdivide  this large area
are based  largely  on  histology.   In the human subject the optic nerve has
two systems of fibers,  the one crossing to the  opposite side, possibly in con-
nection  with the optic  chiasm and the other remaining without   crossing on
the same side,  so that the retina of each eye  has cortical relations in both
cerebral hemispheres.   The  two areas on either side of  the median line are
united so  that we have a  large area in the two hemispheres connected  with
each retina,  but as to the minute divisions of that area we are unable to say
anything definite.
      In regard to the other sensory areas much speculation has been indulged
in and attempts have been made  to localize in unassigued  areas the centers of
the mental phenomena  associated with taste,  smell and hearing.   Ferrier lo-
 calizes taste and smell together in connection with  the subiculum of  the gyri
 of the temporal lobe and  adjacent  regions and the  touch area in the gyrus
 hippocampi,  in which Munk  localizes smell.   Ferrier  localizes   the   area of
 audition in the upper convolution of the temporal lobe,  but recent  experiments
 indicate that  it may  be  entirely extirpated without permanently  interfering
 with hearing.   Luciani says that  it includes the entire temporo-sphenoidal lobe
 and  the  cornu of Ammon.   In  connection  with articulation  all  the cerebral
 functions are more or less intimately associated together.   Broca  despite this
 fact claimed that the area of articulate language is in the lower frontal convo-
 lution   In aphasic conditions there is an interference with cerebral functions.
 Great variations are found n  this  condition from the entire  loss of  speech to 
58
 mere inattention.   In some cases there is an entire absence of speech although
 there is the capacity to use written language;  in other cases there may be the
 inability to express thought in written form; in other cases there is  incapacity
 to associate spoken language with intelligent perceptions, called word deafness;
 sometimes there is a  connected disturbance of  vision and speech,   indicating
 the connection of   the visual areas with association fibers connected with the
 speech areas in the temporal and frontal convolutions.  Exner distinguishes,(1)
 cases in which  the words are  not understood;  (2) cases in which  ideas can-
 not be put into language; (3) cases in which the ideas  and words cannot be
 brought together by association.  These  may be combined in different ways,
 the cerebral hemispheres or the  lower brain regions being  affected.  All true
 aphasic  conditions  however involve an  interference in  connection with the
 cerebrum which prevents   the association of ideas and articulate  expression.
 Can we localize in the cerebral cortex any special region where this associa-
 tion takes place?  It  is claimed that in the  majority of cases where  cerebral
 interference is found  there is a  lesion in the posterior part of  the 3rd frontal
 convolution and the adjacent  regions around the Sylvian  fissure, in the pari-
 etal and temporal lobes.   In Exner's cases 30 out 31 aphasic cases represented
 lesions in the left hemisphere and Seguin,out of 260 found 243 associated with
 lesions on the left side.  This has led to the theory that in normal individuals,
 speech is left brained, while in the case of left handed people it is right brained.
 In the left hemisphere the anterior  central  gyrus and the contiguous convolu-
 tions in the posterior  frontal lobe represent  according to the cases the points o^
 aphasic lesions.
    In the scheme of localization the theory has been carried  out by applying
 the same principles to the frontal region.  It seems if localization is to  be car-
 ried out there must be found some  cerebral  region for the mental activities in-
 cluding perception,  memory, volition and  emotion.  The  anatomical signifi-
 cance of the frontal lobes and the fact that the increase of intelligence is marked
 as we rise higher  among   animal   existences  by  frontal  development  seems
 to confirm  this.  Experiments  upon some animals have  indicated that on  the
 removal of the  forebfain there is a  lapse  into imbecility.  Despite these facts
there  is no part of the brain tha' can sustain with less disadvantage the loss of
a large part of the substance.  In addition it is found that injuries in the other
regions, parietal, occipital  and temporal,  involve loss of mentality to a greater
or less degree so that  intelligence can not  be said to  be  confined  to the frontal
area.
    Undoubtedly mentality is associated  with the activities of the sensory and
motor regions.   The loss of mentality does  not mean the  loss of power  in the
intelligence center but may be due  to the fact that no support is furnished to
mentation in  connection   with such  processes as audition, vision  and touch
Hence  all mentation represents an  intelligence that has a basic  foundation  in 
59
sensations and volitions.   This precludes the idea  of  restricting the  intelli-
gence to the frontal or any  other brain region,  (ioltz has demonstrated that
there is no loss of mentality  accompanying  the loss  of a large part of the
brain substance from one side only,but if the loss is extensive from both sides
either in the frontal, posterior or temporal regions, it involves  a loss of  func-
tion amouning  to  lack of  intelligence.  In this way there is an  interference
with all the senses and  with the mental  activity that is at the basis of  thesd
senses.   Hence in the lower animals idiocy is increased  as the amount  of cer-
ebral substance lost increases.
    Even where the cerebral  functions  are only temporarily  interfered with
there is a tendency to imbecillity.  Hence Goltz says that by gradual removal
of cerebral substance it is possible to reduce an animal to a simple reflex mech-
anism so that as the gradual lapse takes place to idiocy no area or areas can be
localized as intelligence, feeling, emotion, volition  and sensation  but these are
associated with all parts of the cerebrum.  Goltz is not opposed to all localiza-
tion, because he admits that extirpation of the parietal lobes  interferes perma-
nently with feeling and the occipital lobes with sight,  in fact the  removal of
the posterior parts of the brain has a more depressing effect than the removal
of part  of the frontal portions.  His theory is  against the  minute area localiza-
tion.   On this  principle it is altogether impossible to follow  out or  define the
local areas that are associated with the phj'sical  basis of the  mental activities
in the sense of restricting  seusation, feeling,  intellection  and  volition to cer-
tain local regions.
     Ladd has  summarized  the conclusions in connection with  localization in
three principles.   (1) The principle of  use and wont in connection  with hab-
it.   In  the nervous meehanism the  individual  parts can  perform their  func-
tions only when in proper relation to each other and when these relations are pre p-
erly established  by use.  This implies an important   psychic  law that   of
functional differentiation and the law of habit which underlies differentiation.
Individual functioning  is not independent, but  dependent on relations to such
an extent that the association and projection  fibers form the fundamental basis
of all activity.  This forms the basis  of  the education of tfie  individual ele-
ments in the nervous  mechanism so that functioning  becomes more specific
by use  and in this way they are better adapted for their purpose.   By habitual
exercise there is developed a facility among the cerebral areas to perform their
parts with ease.   Following from this we find (2)  the special  localization  of
function.  According to the division of labor the neural  elements  have their
individual functions, but in the combination of individual elements  the groups
of elements become also specialized.  In  the spinal  cord and  lower brain we
find localized  area  functions and in the cerebrum the same principle  holds
crood.   The areas or centers are not so specialized however that extension can-
not take place; hence  we find  differences among  the different  individuals in 
60
the same species due to individual peculiarities.   These areas are therefore not
absolutely  the same for all individuals but are capable of individual variation
depending upon their use and association  with other  areas more or  less com-
plete.   (3) It is possible that when an area becomes  incapable of  performing
its proper functions another area may be  substituted for it.  The only essen-
tial of such substitution is  the established  relation between the substituting
and substituted areas.   Hence  in cases where certain  parts  of the  brain are
lost or removed there is a  restoration of the  lost power.   It is  on this princi-
ple that the absolute and relative  fields of  Exner have been built up  and on
this theory Goltz has strenuously opposed the minute localization theories that
have been" defended in  modern  times,  because as he claims the principle of
substitution may take place to such an extent as  to change in  particular cases
the localized areas.
PART II.  THE CORRELATIONS BETWEEN  THE PHYSIOLOGICAL AND PSYCHIC
                              PHENOMENA.
    We have  considered the  individual parts of the neural mechanism lead-
ing up to and finding their culmination in the brain.   Taking the mechanism
as a whole we find that it consists of afferent,  association and efferent nerve
tracts all of which have a physiological connection with the psychic phenom-
ena.  The cortex cerebri  contains those  elements which  form  the  basis of
psychic activity.   In it we find the meeting place of the sensory  organ fibers
so as to form the  basis of perception as it takes place in the brain.  What we
know of these sensory paths is indefinite.   The sensory impulses  pass into
the spinal cord through the posterior roots, passing along the  cerebral tract
in the posterior column to  the restiform body into the cerrebellum; or after
decussation in the cord through the posterior  part of  the pons  into the teg-
mentum cruris,  into the posterior portion of  the internal capsule.  There-
after some fibers enter the optic thalamus, others entering the  white matter
of the cerebrum.   As to the more exact  distribution of impulses  and their
paths, great difference of opinion exists, and it is fruitless to attempt  to fol-
low the difference of opinion.  So far it has been impossible to  localize accu-
rately the areas representing different portions of the body.
     Ferrier claims that because centers have  been localized  in connection
with sight, hearing,  smell and taste   there must be  definite aieas  connected
with all the various elements of  sensibility, including touch,  contact,  pres
sure  and temperature.  He claims that there is  an exact  differentiation of
sensory and motor paths up to the point where radiation lakes place into the
cortex.   So that theoretically there must be such a differentiation also  in the
cortex.   The sensory and motor tracts are distinct in the spinal  cord,  in the
pons and in the crura as well as in the internal capsule.  Ferrier claims that 
61
when cutaneous sensibility is abolished, the muscular sense is also abolished
and that the paths representing the muscular  sense are quite  distinct from
those of volition.  Ferrier concludes that the centers of touch and of pain are
identical, the latter representing simply the excessive activity of the former.
Hence,  he concludes  that the falciform lobe taken  as a whole represents the
center of  tactile sensation for the opposite  side of the body.  This center is
connected with the motor centers by association  fibers, this association form-
ing the basis of the muscular-sensory localization.   The center for  sight has
been localized in the angular gyrus  round  about the posterior portion of the
parallel  sulcus,  and in the occipital lobe.   By the removal of both of these,
hemiopia for the opposite field of vision results;  and if the angular gyrus on
one side only is removed total blindness in the opposite eye results.  Ferrier
thinks that each hemisphere is  related to the corresponding   half of the two
retinae and that the semi-decussation of the optic tracts is maintained in the
cortical centers and that the angular gyrus is the center of clear vision for the
opposite eye.   The nerve  of  audition  represents not only hearing  but also
has a share in body equilibrium on account of its relation to the semi-circular
canals.   It springs from two roots,  a large anterior root from which  the ves-
tibular nerve arises and a small posterior root from  which the cochlear nerve
proceeds, each of these roots arising from a median and lateral nucleus. The
cerebellar fibers are connected with  equilibrium.   The chief part of the coch-
lear nerve fibers crosses and enters the corpora quadrigemina, the internal gen-
iculatum and pass to the temporo-sphenoidal lobe.   Ferrier localizes the cen-
ter for hearing iu the first  temporo-sphenoidal convolution.   Munk says that
total destruction of this region produces deafness in the opposite ear, wh le par-
tial destruction produces incomplete deafness, which is psychic or word deafness.
The  auditory centers are found to be most perfectly developed in the  left hemi-
sphere, but complete deaf ness will not result without destruction of the centers
on both hemispheres.   The center of  smell is localized in the anterior portion of
the temporo-sphenoidal lobe,  Ferrier finding that destruction of this part pro-
duces loss of the sense of smell on the same side.  The olfactory bulb and tract
represent parts of the cerebrum, triangular in shape, consisting of white mat-
ter enclosing  a gray neuroglia  matter.  It is found in the  olfactory sulcus
parallel to the longitudinal median  fissure.  On the anterior it is continuous
with the olfactory bulb and receives the olfactory nerves.  Posteriorly it is
found to divide into two roots, the mesial and lateral,  which  diverge from each
other as  they  go backwards;  the mesial root subdiving into two  branches
whose course is  unknown.   The taste  center is  localized   beside the smell
center according to Ferrier, in the  lower extremity of the tempora-sphenoidal
lobes '  The taste tract crosses in  the posterior portion of  the  internal cap-
sule   Gowers says that  taste impulses reach the brain  solely  through the
 oots of the 5th nerve and not at all in  connection with the glosso-pharyngeal, 
62
 although he admits that the taste nerves to the posterior part of the  tongue
 are distributed along with the glossopharyngeal through  the optic ganglion.
     The motor tracts concerned in mechanical movements pass from the mo-
 tor cortical areas through the  white matter of  the cerebrum to   the internal
 capsule, in connection with the fibers of the face and tongue are found in the
 knee of the capsule, the arm fibers in the anterior third of the posterior limb,
 those for the leg in the  middle third.   Crossing under the optic  thalamus to
 the crusta of the crura they enter the middle third, the faoe fibers being found
 close to the median line, next the arm fibers  and then the leg fibers.  They
 then pass to the pons on the same side where the face  and tongue fibers cross
 to the nuclei of the facial and hypoglossal nerves of the opposite side, the  arm
 and leg fibers passing   to the medulla in  connection with the  anterior pyra"
 mids,  the greater number  crossing in connection with the  formation of the
 crossed pyramidal tracts, while a smaller number continue on the same  side
 in the direct pyramidal tract.   The pyramidal fibers  are related to the mul-
 tipolar nerve cells in the gray matter of  the spinal cord, from which the an-
 terior roots of  the spinal nerves originate.  The motor cranial nerves  take a
 similar course,  and after passing from the internal  capsule and crusta they
 cross  to the nuclei on the  opposite side from which  the fibers   pass  to the
 muscles that are supplied by these nuclei.
     According to Meynert there are three projection systems.  (1)  Those fibers
 that connect upward and downward with the cortex cerebri, radiating through
 the corona radiata, some passing  through the basal ganglia  and others being
 connected with the central gray matter.  Connecting the two hemispheres are
 the commissural fibers, and also the associating fibers uniting the different re-
 gions of the same hemisphere  together.  In the corona there are fibers from
 the corpus striatum, the lenticular nucleus, the optic thalamus and the corpora
 quadrigemina.  (2) Fibers that pass longitudinally down to the central gray
 canal, some of the fibers terminating in the grey matter and others  descending
 to the lowest spinal nerves.   Here  we have fibers  from the caudate and lenti-
 cular nuclei  passing  to the medulla and pons  through the crusta, from  the
 optic thalamus  and  corpora quadrigemina to the spinal cord through the leg-
 mentum.   (3)  Fibers  that  include the sensory and motor peripheral rterves.
 According to Meynert in connection with the medulla three fiber svstems are
found,  the  projection,  commissural and association.   The  projection  fibers
represent elongations of the  cerebral cell  axis  cylinders.  The  commissural
fibers represent the transverse fibers of  the  corpus callosum and the anterior
commissure, the former  arising from the cortical cells either directly or indi-
rectly,  the different  parts of  the two  hemispheres  being united  by diffused
fibers through the commissure.   The  anterior  commissural  fibers unite the
 temporal lobes of the two hemispheres and  the olfactory and hippocampal areas
 on opposite sides.  There is considerable  variation in the asso«iation fib 
63
According to Meynert the short fibers unite contiguous convolutions, the long
fibers are united in bundles, forming  connections between the frontal and oc-
cipital lobes, the front and exterior of the  temporal lobe, the  temporal and
occipital lobes, the frontal and temporal  lobes,  the  hippocampal and callosal
convolutions,  the inferior parietal and the fusiform lobules. In this way there
is established a close  connection in the nerve mechanism.
    In the application of localization to the  mental  functions  it is claimed by
some  that every nerve cell in the gray matter represents a  psychic elemeut  so
that the  cell becomes the psychic  unit.  In  opposition  to  this  minute lo-
calization others claim that the brain must be taken as the unit.  In the same
sense  in which the mind is in the body, the mind is in the brain.   The brain
represents a neeessary medium in tne correspondence between mental phenom-
ena and peripheral changes and it also forms the physical basis in connection
with which ideation and volition take place.   If a limb is  amputated  there is
still a feeling  of its movement  indicating that  the ideas  and feelings are  not
localized in the limb.  It is claimed that  the  existence of a certain  amount of
purposive adaptation  in the lower centers indicates that  intelligence cannot be
limited to the higher centers.  This led Ferrier  to conclude  that  there  is  not
an essential distinction between the simple reflexes of these lower  centers and
the highest psychic centers, the  difference  being one of  degree.   But in  the
case of man there is less of this adaptive action than in lower animals, besides
in  man consciousness does not extend to the impressions of the sense  organs,
so than conscious activities may  be regarded as limited  to the  cerebral  hemi-
spheres.   The meutal funotions seem to be connected with the  cerebral  hemi-
spheres, at least from the standpoint of the motor execution of  them.  We
have no data on which to localize the mind in any one area or in some areas  of the
brain  as there may be a loss of considerable parts  of the  cerebral lobes without
mental impairment.   The cerebral hemispheres therefore seem  to  operate aud
co-operate as a unity  in the exercise  of the  mental  functions. According to
some  psychologists the consciousness represents simply the sum total  of indir
vidua! sensations in a successive series, so that the individual  nerve  elements
supply their quota to the whole conscious experience.   But  this sacrifices psy-
chic unity.  The  mental processes coincide with cerebral  processes and  so
consciousness cannot be bound up in any single cerebral area.   Meynert  claims
that when we consider the intricate meshwork of  fibers  in the grey  matter we
must  admit that there is a possibility of independence of function.   The corti-
cal distribution of the grey matter renders it possible according to him that cor-
tical regions may act independently.   Waller indeed claims that  the  distinc
tionof sensory and motor regions is false, claiming that every center  must be
really sensori-motor so that as he says  "between centripetal and  centrifugal
impulses I see a single psychical  process, one and indivisible.  All that  I can
recognize in a center is an organ of elaboration  receiving and giving out im- 
64
pulses."  Hence he claims that a central process is not properly sensory or mo-
tor but senso-motor.  Meynert really  coincides  with this view,  although he
expresses it differently.  According to him there is no real motor capacity either
in the nerve cells or fibers.  The cerebral hemisphere is wound up by  the sen-
sory keys resulting in the activity of the muscular mechanism through  the cer-
ebral mechanism.  Hence he  claims that  "sensitiveness is the  only  specific
property of brain cells."
     It would seem  from the experimental evidence already referred to that the
removal or injury of certain regions involves the loss of sensori-motor  func-
tions, but this may refer simply to an objective loss  and does not  necessarily
involve the loss of the subjective psychic activity.  At the same time the  fact
that adaptiveness characterizes movements or actions does not of necessity in-
volve psychic guidance or  conscious control.  From  these  two  standpoints,
therefore, we may conclude  that the  sensori-motor  localization does  -not in
volve the proof  of their relation or correlation to the psychic element  of con-
sciousness.   The cerebral  processes have been explained  on the principle of
reflex  action.  But this does not seem to explain why some of these processes
involve  consciousness  while others do not.  Jackson  has attempted an  expla-
nation by claiming that the  sensori-motor mechanism of the  cerebral hemi-
spheres is subject to the control of a higher re-representative area.  According
to him the mental proocesses represent the  subjective  correlate of the  sensori-
motor processes.  There are numerous  sensori-motor phenomena that have no
correlate in consciousness.  It may  be that sensitiveness which characterizes
the lower centers becomes more  delicate as we  ascend  higher in  the  scale of
centers.  In paralysis there is an involvement of  the  sensori-motor  apparatus
without of necessity any psychic accompaniment.  The same is true of  sleep,
epileptic and hypnotic conditions.   Hence the consciousness of man  seems to
be placed above the most highly sensitive conditions of the purely physiologi-
cal sensory motor processes, and as such cannot be localized  in any  one part
of that sensori-motor  cerebral apparatus, unless we localize it in a higher area!
Ferrier  contests this hopothesis because it has  no experimental  evidence.  He
regards the theory as  valueless from the purely psychic standpoint.  He claims
that in the sensori-motor areas there is a physiologieal  basis for sensory  per-
ception  and ideation and for the  voluntary acts and emotions   He prefers the
theory of higher and lower degrees of  complexity in  the sensory and  motor
areas.   It is true we have found  tracts  along which  stimuli may pass  to these
brain regions, but this of itself does not prove the existence  of such  areas as
substrata of psychic actions.   Spencer says that different parts  of the  cortex
have different functions in the mental  phenomena,  but these  different  parts
like all  the rest of the organism are subordinate to mental activity, they  sub-
serve but do not serve.   According  to Spencer a perception can be  localized
jn a nerve center only diffusively, and the  single  fiber  cannot produce  con- 
65
sciousness;  consciousness  implying diffusion  in connection  with a plexus of
nerve cells and fibers.   Wundt  repudiates the  idea of  localization of  sensa-
tions in isolated areas of the sensori-motor regions, claiming that in the  fron-
tal region we find the organ of apperception, and not in the complicated mass
of sensory  and motor  tracts.   Waller  vigorously  opposes  this idea on  the
ground that we have no evidence of any  such higher centers above the  senso-
motor.   Really there is no proof on either side.
    In the frontal region  we find a non-excitable area, anterior to the region
for the head and eyes.   Most psychologists regard this as the special seat of the
mentation processes.   According  to Meynert in  the forebrain   sensitiveness
which characterizes the lower centers is transformed into actual sensation.   In
it we find nerve tracts that carry all the impressions to this  higher region  con-
verging them into the phenomena of sensation.   Intelligence is limited to this
forebrain so that it controls all the rest of the mechanism.  By extirpating the
forebrain according to  Goltz there is a  serious  interference  with intelligence
resulting in idiocy.  This is due according to Meynert  to the  fact that intelli-
gence  is based on perceptions arising in connection with the  sensations of the
nervous mechanism in  which the forebrain is specially  active.  Hence the ex-
ercise  of every part of the brain cortex depends  on the aetivity of  the forebrain,
all the different parts of  which are  connected  by means of association  fibers
not only to each  other,  but to the other parts of the brain.   The Spencerian
principle is really the  most generally  accepted along this  line in  connection
with psycho-physiology, the ratiocination being dependent  upon definite corre-
lations.   Hughlings—Jackson has propounded a theory   that is  interesting.
Evolution represents the  moyement from the well organized centers up to the
most highly  developed centers, while  at the same time it is from  the lowest
well organized up  to the  highest less organized, in other words from  well  es-
tablished relations to less organized relations.  In this   evolution  there is a
passage from the  automatic to the voluntary.   Thus in these highest centers
which  represent the culmination of nerve evolution constituting  the  physical
basis of the mind we have  three elements, the least organized, the most  com-
plex and the most  voluntary and on the basis of these the  upbuilding of the
neural mind takes place.  The lowest centers are found in  the spinal  cord and
in the nuclei of the cranial motor nerves.  They represent the lowest cerebral and
cerebellar  centers and any interference  with them cuts off the  motor system
they represent from the higher central system.   The next  centers are the mo-
tor areas localized in the cerebral hemispheres  and the ganglia  below,  repre-
senting larger body areas than   the first centers.  The highest  centers repre-
sent  motor areas anterior to the motor convolution  regions the entire anterior
portion  of the brain being  motor.   These highest  centers represent the most
complex centers and yet  they are least organized, representing the widest body
regions. Hence from the lowest to the  highest centers we have, (1) increas- 
66
ing  complexity and (2) this involves  increasing representation   so  that the
highest centers represent the co-ordination of all the  movements of the body
embraced in the lower centers.   Hence the three may be called,  representative,
re-representative, re-re-representative.   In regard to the sensory   centers  ami
their relation to the motor, he says (1) that the highest sensory centers in the
sensory region and the highest motor   regions represent the physical  basis on
which  consciousness rests, and (2) that consciousness embraces the entire psy-
chic field just as the physical basis of it includes the entire physical being, rep-
resenting movements,  impressions and sensations of the entire body.  In other
words  the highest centers are representative of the entire person  physical  and
psychic.
     Meynert has attempted to establish a sequence in the  development  of as-
sociation, the intensity of associations  established  depending  upon their  fre-
quent reiteration in consciousness.  Hence the difference between accidental
association and this association based upon causation in which  the recurrence
of external stimulation establishes a  permanent cerebral  association.  In the
development of the association imitation is an  important  principle as one in-
dividual may grow through the imitation of psychic association in others,  but
before  development can take place it must become an individual association of
ideas.  Hence in the individual projection  and association  represent the two
principles of cerebral   activity and these form  the  basis not only of the purely
receptive capacity of the brain but also of its creative capacity.  The associa-
tion fibers are said to be connected at the two ends with the cortical  cells,  the
projection fibers being found in connection  with the corona radiata diffusing
therefrom into the forebrain leading into the cortex the impressions of exter-
nal  stimulation and  dividing them among  the sensory  centers.   Here is the
physiological  basis of the  correlation of the  physiological  and the psychic.
Waller has tried to show that all neural processes are similar if not identical
so that the neural process   includes within it from the  centripetal  standpoint
and in  the  order of  sequence   impression, sensation and perception; the  im-
pression here exists external to consciousness,  the sensation being a  conscious
impression and perception the conscious result of a  conscious  impression.   All
that is  claimed for it is that this sequence represents the possible elements in a
neural process and hence the basis of a neural induction.
    The objection to this   inductive  method of viewing  the mental operation
is that the physiological organism  is made to subserve what seem to be primar-
ily psychic activities  without attempting to prove that the correlation on this
basis is real.  It is true that the  objective  phenomena  form  the data upon
which the neural processes are based,  but whether we are justified in regarding
both the presentations  and representations  in consciousness  as correlates to
the purely  physiological  activities  we have not yet  determined.  From  the
physiological side we  have definite activities associated with excitations and re- 
67
flex actions ;   on the psychic side we have certain  elements in consciousness
which form the premises of  mental activities ; to complete the  chain we  must
say that the sum of the physiological activities pas* into the conscious exper-
ience as  the contents of consciousness,  so that from the standpoint  of con-
sciousness the conscious subject views these  coutents which are  psychic and
not the physiological activities..   In this way the nervous mechanism is brought
into close relation to  the contents of consciousness.  When  this takes  place
there is, or seems to be,  a subjective ego which considers all of these conscious
phenomena,  unifying  the diversified experiences but in what  way we cannot
tell.   The central nervous system therefore can receive  and  distribute deter-
minate neural commotions,  exercising some modifying influence over  its own
neural  activity.   How this is accomplished is unknown and may be left to met-
aphysics to discuss.
    Schaefer by  separating the  praefrontal  lobes from the rest of  the brain
showed that  no  appreciable mental change took place in the  case of monkeys,
disproving as he claimed,   the older  conclusions of Ferrier,  who found fol-
lowing  extirpation  conditions   of  apathy  and idiocy  at least  temporarily.
Schaefer claims  that the frontal  lobe is not essential to  the mental  life,.   The
pathologicai  evidence seems to show that injured or diseased conditions of the
frontal region do not impair the sensory or  motor  functions,   so that this re-
gion cannot  be regarded as necessary to the sensory and motor phenomena of
consciousness.  This implies that if the functions of these regions which are said
to subserve consciousness are preserved, then injuries involving the region that is
said directlvto serve consciousness do not impair the mentality.  Ferrier cites the
case of a man who died from a  brain  condition in the full  possession of all
mental capacities, the post mortem examination of his brain  showing the entire
absence of the right hemisphere from  suppuration.  As  we said  before the at-
tempts to explain conditions of   th    air affecting the use of  language  seem
fO indicate that,  the entire   cortex is associated in some way  with language.
Similarly in  the case  of insanity  it would seem that the  entire  cortex seems tc
be influenced more or less in insane conditions,  indicating that the  mental and
conscious influences are distributed  over the entire cortex.   All we can  say is
that the iniud is correlated with the external world through the medium  of the
neural mechanism and injured or diseased conditions of that mechanism either
imnair or interfere with the correlation.  The view of Meynert seems to be the
most reasonable, th,at the highest centers  simply represent arranging  mechan-
isms for the representation  of impressions coming in from below and for the
connecting of  the different mechanisms in connection  with this process  of ar-
     • „   Theidea of James is  in line with this, that impressions arrive  from
the organs of sense arousing certain arrangements, these in turn arousing oth-
      until the motor  mechanism is stimulated, all of these processes being in
    sciousness.   But this  does not describe  or  analyze the  mind.   It   would 
68
 seem then that sensations  represent states of  consciousness  the  brain repre-
 senting the medium through which stimuli reach the mind.
     An attempt has been made to identify different elements of the mental op-
 eration with  definite  localities in the cortex.  This has been  done  chiefly in
 aphasic conditions, but the observations made may simply indicate an interfer-
 ence with the physiological substrata and  not with the psychic.  Mental  activ-
 ities are complex so that it is difficult,  if not  impossible, to  identify distinct
 parts of the neural mechanism with the definite mental factors of an  operation
 of the mind.  Kirchhoff thinks that consciousness includes all the internal pro-
 cesses, so that no individual elements of  consciousness can be identified ;  and
 that the entire nerve mechanism, not simply  the cortex, is engaged in these
 processes.  While this is true we  must remember that there is a  more direct
 relation of the brain cortex with mental processes than that of any other part
 of the mechanism.  James thinks that there is a form of  consciousness in the
 cortex that may be regarded as the sole consciousness  of man,  any conscious-
 ness in the  lower centers being  directly  subservient to  the self consciousness
 of the cortex.  Jackson seems to confirm  this view from his evolutiouary stand-
 point,   in which he claims that every part of the organism must have represen-
 tation   in connection   with any unit of the cortex,  this  representation  taking
 place undoubtedlyjin consciousness. Meynert and Munk seem to oppose this idea
 in claiming that sensitiveness   is the common  property  of the  individual cells
 As the cells possess this specific energy, so soon as there is a  neural sensation,
 we have the conscious  intelligence everywhere in the cortex,   so that conscious
 movement may originate from any point.   Hence, according to Meynert, mem-
 ory  represents a common characteristic of all cortical cells.  This does not  ex-
 plain and seems to  take no account of the unity of consciousness.   It does not
 tell how cell activity,  which  is fundamentally  chemical,  and physical actions
 can give us  the phenomena of consciousness.   Hence we may conclude that
 the external world of objects and the physiological  neural mechanism  are botn
 necessary to our conscious states; that  the physiological and psychic  represent
 each a  universe within itself,  so that  we  cannot  make the two convertible; at
 the same time the correlations  are so  close that the  psychic  activity is  mani-
 fested only through the physiological.
     Cabanis concludes that the brain   secretes thought just as the liver secretes
 bile. Here of course the analogy is rudely original and uncouth, although there
 is  a certain element of truth in it.  The mind considered  as a natural force cannot
 be subjected to observation but can be understood only from the manifesta-
tions of its  activity in and through matter.   There are no  doubt correlative
changes in  the material substratum corresponding with the  mental activities
Every mental phenomenon is in some  sense the result of certain chants  tak
ing place in connection with  the neural elements.  The mind does not  repre
sent simply the material  products of cerebral activity but that wonderful de" 
69
gree of energy that cannot be brought under observation.   The results of the
activity of the brain as these can be  observed in  passing from the  biain  in
connection with the blood for further processes of assimilation  and  excretion
do not represent  the mind.   The question of tue consumption of the nerve
cell in the mental processes is not definitely settled because it may be  simply
in the matters furnished to the cells by the blood that the changes take  place.
If this latter were the case why does the performance of a certain function im-
ply the impression made upon the neural  substance in such  a way  that there
is a predisposition to perform the  same  function  again.  This  cannot  be ex-
plained unless on the basis of some  neural decomposition which is renewed  by
the process of nutrition.   Among the older writers the vital spirits were sup-
posed to be  secreted in the  brain in  connection  with  the blood  so that these
became exhausted by  frequent or  continued use.  There is  no  doubt that the
nerve substance is nourished in connection with the blood, a  secretory process
furnishing to the nerve cells the nutritive materials and that in  this process of
nutrition  the elements are exhausted and  waste matters are  thrown off.  It is
quite possible that in connection with the nerve cell there is a  permanent and
a transitory element, the former representing the essential structure  while the
latter  represents what is used up in functional activity.  To cut off a nerve
cell from  its nutrition   would mean its destruction, so that its  functional  use
depends upon  its established relations  with the blood  and in  this  sense the
blood  is essential to mentation.
     Popularly mind represents  an abstraction, although  it is a  generalization
based upon the abstract idea gathered from the mental  phenomena.  We ob-
serve the mental phenomena and then by abstraction form the general concep-
tion of mind in connection with these phenomena.  It does not  follow however
that because we  have this general idea of the mind that  it is capable  of  an  in-
dependent existence apart from the brain  and the brain nutrition by the blood.
The human mind  however, tends to  translate the  idea into  real  form  and
hence the mind which originally arose from an abstraction  becomes  an entity.
Into this entity is infused life and spirituality so that popularly  it is  regarded
as havino-  an independent existence.  There is no doubt that mind depends on
the brain°and the entire  nervous mechanism in order to secure its manifesta-
 tion the brain being the organ in connection with which mental existence and
 activity are  displayed.  The power of the  mind must  be  regarded as some-
 thing that is matured in connection  with the  progressive development of the
 neural mechanism.  It differs from  the organs like the heart  in the  fact that
 at its birth period it is incapable  of any of  the highly organized functions of
 b ain life.   It certainly has organic capacity even from an  embryonic condi-
      of controlling the organism as a whole but its specialization as  the organ
  f the higher life of man depends upon education.  This educational develop-
   ent applies not alone to the individual but has a bearing upon the  race as a 
70
 whole.   The acquirements of preceding generations form the  inheritance  of
 the brain and mind, and these are brought to bear  upon the mental develop-
 ment in such a way as to train up the child mind in the very sphere of acquired
 experience, so that the individual  subjected to environmental experiences may
 be able to make the most of his individual life.  The very form of education,
 including its language and the appliances it uses, represents the embodiment of
 numberless stages in historic progress brought to bear upon the individual life.
 The brain development therefore is something that takes place  aftei birth and
 as the brain becomes  differentiated it is correlative with the development of the
 intelligence.  And yet the  mental activity  eannot be separated from the nerve
 structure and its proper nutrition in connection with the blood.   Here we have
 the primary correlation between brain existence and  nutrition and mental ex-
 istence and development  that forms the fundamental  basis of  all  the other
 correlations found  in a mental science.   The nervous system consists of myriad
 cells localized in the brain  and these form the  initial foundation  of brain activ-
 ity.  Out from this region we find ganglionic masses of cells which  form  the
 centers of  functional activity on  the part  of the internal organs of the body.
 They do not represent exhaustless centers of generating force for their capac-
 ity depends upon what supports their cell life.  Hence in  the cell there takes place
 a transformation of potential  niatter into kinetic force, the nerve  cell becom-
 ing the center of the correlation of matter and energy, the resultant being the
 manifestation of the highest  degree  of vital force.  Thus  to preserve this cor-
 relation represents the necessary condition upon which  the existence of think-
 ing and  thought  depends  so that it involves the two forms  of thought, (a)
 statical  thought  which is  dependent  on  nerve cell maintenance;  and (b)
 dynamic thought  which manifests itself through the  changes that take place
 in connection with the  metabolism of nerve tissue  and the changes  that are
 involved in the response of nerve tissue to stimulation.
     From  this  standpoint, therefore,  in establishing  a correlation between
 mental phenomena and the  neural mechanism certain  preliminary  principles
 may be laid down  as the basis of those  correlations.  (1) In connection with
 the origin of thought there must of necessity be a  correlative variation  in the
 grey  substance  of the brain. No thought  can sustain  any relation  to the
 body mechanism without this correlation.   (2) This brain alteration representa
 a variation that falls  under the  phySleaLprinciple of  motion.   According to
 Unzer these Drain movements represent material ideas,  of which  there are two
kinds, the object presentative and th* ofeject  representative, the former origi-
nating externally  and the latter inteVftally,  When originated the  direction is
determined by the  nerve tracts in  the relation of nerve cell and fiber.  (3)
These motions taking place  in connection with the   neural substance  may be
interrupted by the  interference  with nerve  continuity arising either  from
mechanical pressure or injury to  the nerve tissue  or from an  interrupted or 
71
abnormal blood supply, or from the accumulation of waste products that pro-
duce exhaustiou.   Thus the essential movements associated with mental and
brain  activities depeud  upon  normal  physiological conditions.  (4) These
motions require time, representing the  time relations that are  established in
connection with the ueural and mental processes.  The question that comes up
for discussion is not that of the functional relation of mind to brain but rather
those conditioning processes involved  in cell activity and the bearing of these
processes on the  mental  phenomena.  If  we  consider  the  lowest forms of
animal life in which nerve tissue manifests itself it will be  evident that the con-
ditions of neural activity are very simple ; whereas  in  ascending the  scale of
existence we find increasing complexity in the action of these nerve cells, indi-
cating that side by side with increasing by complex neural activities we find in-
creasing by complex mental activities.
    In the entire  realm of nature there is not found any deep chasm  between
nature's  productions; so in the realm of animal life one  form passes into an-
other on  a gradually ascending scale from the lowest up to the highest.  This
same principle is  applicable  to the development of  individual man from the
embryonic to the  adult condition.  Man, as he  develops, is found to progress
through stages found in the lower  vertebate animals,   the difference being
that the permanent stages which  mark the highest development in  the lower
animals form the  transitional stages in the human evolution.  He represents
not only  the climax of all lower development,  but in miniature we find in his
progress the  steps in the march upwards  among the lower animals,  so that
man unites in himself the perfect stages of all  the perfect  forms of  develop-
ment,  himself the ideal.  The human ovum  is not distinguishable  from the
ovum of  one  of the lowest animals and its  stages of  embryonic  development
are also similar.   What is true of the body evolution is  equally  true of the
brain.   At the fifth or sixth week the human brain in the foetus is  found in
the form of a series of small sacs, the anterior one divided into two parts rep-
resenting the cerebrum, the posterior one being larger and representing the
cerebellum.  Anterior to the cerebellar vesicle is the vesicle representing the
corpora quadrigemina, another vesicle being found between this and the frontal
one corresponding  with the optic thalami.  Here the foetal brain is compar-
able to the fish brain, on account of the lack of cerebral development  and of
the convolutions.   Five or six weeks  later  the foetal brain is comparable to
the brain of the bird, on account of the increased cerebral development, the
mid brain vesicles being partially concealed by the  cerebral hemispheres, al-
though  as yet the  convolutions are  lacking,   with an anterior  commissure.
Shortly after this the foetal brain is  marked by the still further cerebral de-
velopment with the commissural development in conection with the corpus
callosum,  although  limited to the anterior part of the hemispheres and so
comparable to the stage of growth found in the Marsupialia.   About the sev- 
72
 enteenth week  in the foetal brain  the middle vesicles are developed poster-
 iorly con2ealing  the corpora quadrigemina,  the posterior lobes  developing
 also backward over the cerebellum.   At the same time as the development of
 the posterior  lobes is  taking place the  frontal lobes are being  enlarged to-
 wards the forehead until we find the highest (animal  human condition of the
 brain.  It is easy to see that if  the development is arrested at any stage,  the
 brain may be left in the condition of a purely animal brain;  in line with this
 it is found that in congenital idiocy there is an  arrest of brain  development
 represented by the lower animal condition.
     Man is  thus in  his development a "compendium of animal nature," "par-
 alleling nature in the cosmography of himself," as Browne puts it.   In  this
 way we can discover in the  human being  the activities of  all the different
 forms of nerve potentiality as they are found in the animals.   Hence we have
 the scattered  ganglion cell activity  of the sympathetic  system which repre-
 sents the simplest mode of neural activity in man; thus we have co-ordination
 of the different tissue and organ elements under the sympathetic ganglia cells.
 Then we have the ganglionic nerve cells of the cord  so  combined as to form
 independent centers in connection with the most important and complex body
 movements. Next  we have the sensory  ganglia in which  are found large
 numbers]of  differentiated nerve cells combined together in the brain.  Lastly
 we have the cerebral  hemispheres in which  specialization is most perfect.
 Thus in the human brain we have  a synthesis of the  best brain conditions in
 the  lower animals,  the combination  representing a  harmony of  functions
 which constitute  brain and also  mental vitality in man.  From  this stand-
 point of  correlations there are therefore in the human subject  four centers
 that require to be taken acount of, (1) the primary centers found in connec-
 tion with the gray matter of the cerebral convolutions, associated with  idea-
 tion; (2) in  subordination to these we find the  secondary centers  in the gray
 matter between the pyramidal decussation and the floors of the lateral ven-
 tricles,  associated with sensation;  (3)  in subordination to these higher cen-
 ters we find the tertiary centers in the gray matter of the. spinal cord, asso-
 ciated with reflex actions; (4) Subordinate to all the higher centers  we find
 the organic centers associated with the ganglia  of the sympathetic system,  in
 the ganglionic cells in the region of the  viscera with  established connections
 by communicating fibers  with the cerebro-spinal  system.  In this  chain of
 centers there is subordination on the  part of the lower to the  higher centers,
 although  each class of  centers has   its own independent  function.  All of
them are in  subordination to the primary  centers   esp3cially in unfolding
 the consciousness of the will that marks the most perfect  co-ordination of  the
 fuuctions of the body and the greatest manifestation of the principle of  indi-
 vidual activity.   The sympathetic cells  in co ordinating  the activities of the
 different organic elements mark the simplest form of this individual activity! 
73
this sympathetic co-ordination is transferred to the  cerebro-spinal system in
which the vital  organization of  the lesser elements takes place.  When we
remember this close relation established among the different centers  of ani-
mal and organic life we are not surprised to find psychic  factors all through
the entire organic life of man.
    In this connection then mind becomes the  most perfect development of a
harmonized physiological life or  vital force and to  its existence  and  vitality
all the lower natural forces  contribute,  while  this vital  force is dependent
upon all the   lower forces that contribute to its vitalizing energy.   Setting
aside all the purely abstract  definitions of  the mind, such as,  "that which
thinks, reasons,  wills,"  physiology answers that it is associated with the
brain substance.   As we study mental phenomena we become  convinced that
mind is to our knowledge at least non-existent apart from the brain, because
all we know of itin its phenomena is in connection with the brain.  From this
standpoint mind simply represents the highest functioning of the brain associ-
ated with consciousness, this functioning  assuming the forms of intellection,
emotion and  conation.  The human brain  represents a  living  organ with
functious higher and more perfect than those of  any other  body organ,  the
nature of whose existence and operations we only know through the manifes-
tations given us in the mental phenomena of life.
     Many of  the reflex  actions asssociated with  the spinal, cord  play a mos
important part in the human activity and therefore form the basis upon which
psychic functions rest.  In the  spinal cord  we find  the power of  retention
corresponding with memory in the higher centers,  in virtue of which  an ac-
 tion done once becomes easier  afterwards because  of the power  imparted to
 the second action from the first.  In this way by  the principle of association
 certain  movements may be so closely   connected  in the nerve centers  as to
 render it impossible to  separate them.  Hence the  reflex acts of the   spinal
 cord represent the acts of an organized mechanism so  that whatever  tenden-
cies have been inherited in the system predispose the actions in a definite di-
rection.  On a higher scale in the sensory ganglia we find the  capacity to re-
 spond to stimulation by adaptive movements apart from consciousness,  con-
 sciousness not being brought into play unless  at the same time as we have
 the sensation or subsequent to it there is a perception;  in this latter  case the
 stimulation   has passed beyond  the sensory and into   the higher  cerebrai
 spheres.  The sensory centers lie intermediate between the spinal and higher
 cerebral centers and thus manifest not only the reflex functioning but  also ex-
 hibit  the rudimentary elements of those functions  that attain  their climax of
development in the cerebral convolutions.  In this  sense they  represent more
 complex actions than  the spinal centers,  particularly connected  with the re-
ception and co-ordination of impulses,  in which  they manifest the germinal
evidences of a higher  intelligence.   But it is in the countless nerve cells in 
74
the gray matter of the cerebral hemispheres that we find the centers of ideation.
These two hemispheres  represent two large ganglionic masses superadded
to the sensory  and motor areas bound  together by numerous   fibers for  the
purpose of translating sensory impressions into ideation.  In the evolution of
the human intelligence the mind of  man has undergone vast  changes before
attaining the climax of development, the princiole of specialization  associated
with the increasing complexity of the brain  mechanism being at the  basis of
this correlation.  In this ideational development there is also the  emotional
and the volitional progression.  Phrenology has long attempted  to localize
the different mental  functions,  mapping  out the cerebral surface into well
defined areas, assigning to each area a mental function.  But  these attempts
although aided by the genius of the ancient Greeks and fostered by the philo-
sophic  enterprise of  men like Comte have been entirely  discredited because
they have no foundation in anatomy or pathological observations.   The local-
ization of  the motor-sensori areas is quite a  different matter.   It is certain
that the frontal portion of the convolutions is associated with  the movements
and sensations, from which  we get our sensori-motor intuitions, and that the
posterior part of these same convolutions is associated with the purely se  sory
from which arise the sensory  factors in ideation.  This gives  us  the reflex
arc in psychic acts.  Activity aroused in  the sensory area passes to  the senso-
motor area from which it receives intelligent expression in movements,  lan-
guage, etc.  This represents the most  simple  form of the psychic  activity.
This represents  the  ideo-motor arc as  distinguished from the   purely senso-
motor arc,  representing the climax of and containing within itself the poten-
tialities of all the lower neural arc processes.  In this 'highest reflex the af-
ferent impulse is represented by an idea  or  perception and the efferent by a
perceptive  movement or volition.  Within the cerebral hemispheres we find
an innumerable number of these reflexes all  bound together by internuntiant
connections so that numerous complicated  plexuses are formed, the basis of
numerous complicated mental processes.  In the development  of  the brain
and mind correlatively there is not only an income  of sensation  correspond-
ing with every outgoing of  motion, but in the progress of experience percep-
tions become capitalized so  that the out going of  motor impulses represents
not merely the present and transitory sensory impulses but an  accumulation
of such ideo-senso-motor experiences.
    According to Haller  ideas are traced upon the brain as  actual impres-
sions;  but according to Bonnet the ideas represent molecular changes trans-
mitted as vibrations  along the nerve paths.  It is on this principle that when
a vibration has passed along a path  once a  modification is  supposed to take
place  in the  nerve  substance which  renders it very responsive  to similar
changes in the future, something being retained that disposes  it to the same
functional activity,  forming the basis of differentiation of  function.  In its 
  revival again if  in consciousness it  embodies recollection,  if  not in  con
  sciousness  it is simply a neural predisposition.  Hence there  is retention
  not only in consciousness but also in unconsciousness, the nerve process be-
  ing its psychic  correlate  in both.
      This principle of retention  lies behind memory, in  fact behind every psy-
  chic function as the physiological basis of these  functions.   Here we have the
  distinction of  Unzer, ideas  of presentation  and representation, those repre-
  sented by the former being stronger  than the latter,  because  aroused in con-
  nection with the accustomed external stimulation  so that the sensory  and mo-
  tor elements are both strong.  On the other hand when they  are brought to
  the internal attention their activity may  be intensified, even to the extent of
  reacting upon the  sensory medium so  as to produce  an illusion or hallucina-
  tion.   In connection with perception we have the  grouping  of several sensa-
  tions in connection with a  single idea.  When this organization  has taken place
  any or the sensations that  produced  the idea may arouse it to mental activity
  From this standpoint the perceptions  represent symbols  which depend upon
  the different senses,  the impressions received from  these different senses form-
 ing the basis of our idea of the object.  Hence the idea  is  organized as a men-
 tal object but it  does not have any correlate in a  single external object.   To
 us then psychically the idea is not presentative, but representative  of various
 preventative objects  introduced  to us through  sensations.   The ideo-motor or
 perceptive centers  then idealize what aomes  to us through the sensory or senso-
  motor channels  so that there is  a subjective field of ideation in some ' sense
 correlative with the objective field of sensation, although different from it be-
 cause mentally constructed from  objectively perceived  phenomena.   Ideation
 has its  progressive evolution on  the basis  of differentiation  and integration
 differentiating those elements  that are unlike and  synthetizing those  that  are
 alike.   In this development of ideation the progress is marked   by increasing
 complexity towards  the abstract, parallel  with the increasing  complexity of
 the brain;  so that in the uncivilized races we find a lower stage of psychic de-
 velopment in which abstr^cti >n is almost entirely  absent, while  in  the highly
 civilized abstraction becomes more perfect.  Hence in analyzing  abstract  con-
 ceptions we must trace back the devolution process to the concrete  through ihe
 less abstract,this representing  the true process of analytical  thought. Hence we
 find from this  standpoint the  absurdity of innate ideas,  except in the sense
 that an  individual born in civilization  inherits  certain  predispositions found
 embodied in  cerebral conditions that are waiting to be called  into functional
 activity.  Hence  in man we  find in the cerebral  convolution development  the
 cerebral substrata  which represents from  the physiological side  the  capacity
 psychically to acquire ideas that are   impossible in  lower animals  that do  not
possess the same  cerebral convolutions.
    In regard to  the mechanism of ideation  we only know it hypathetically. 
76
 It is supposed to consist of a neural .circuit  in which certain  cells are  united
 so that in the passage of a molecular variation through  this circuit  perception
 takes place by the stimulation of the points which mark the perceptive centers.
 This stimulation can  only take place  at the cell  junctions in the  circuit, and
 hence any sensation that was  engaged in forming the  perception can  arouse
 it.  In passing from the percept to the concept or from the abstract idea form-
 ed in connection with the sensations to the abstract idea formed in connection
 with the perceptions by their comparison and  differentiation,  we must increase
 the complexity of this nerve circuit.   This is accounted for on the  physiologi-
 cal basis  of  complexity found in   connection with the cerebral  hemispheres.
 In connection with  ideo-motion we find a sensory  impression, a motor  result
 and a cerebral process along a cerebral circuit, this entire process being  essen-
 tial to the formation of the idea, so that the correlate of the mental idea  is the
 whole process.   This may be modified by development so that when complete
 organization has taken place in the cerebral substrata any part  of the  neural
 process  may result in ideation, just as the mind emphasizes the sensory or mo-
 tor part of the process.  The idea however is really  correlative with the entire
 neural excito-motor process.  Thus we find in the central system a neural sub-
 stratum capable of great native capacity and developed adaptation, on the basis
 of which harmony is  established between the   internal functions  and the ex-
 ternal surroundings, this harmony forming the basis of the correlation  of all
 the physiological and psychic phenomena.
     1.  Analytical Cokkelations from  the Standpoint of the Neiko-Mental
 Pkocesess. In the world of experience we find a great number of things  which
 come to  be known by us on account of their possessing certain characteristic
 properties.  These objects are perceived by us in their common properties and
 they are apperceived under time, space and action  relations.  In the ordinary
 life the attention is fixed on certain things  but even then the  attention  is di-
 verted from the objective things in themselves  to the sensations aroused in us
 in virtue of the relations of these things  to us through the senses.  The unre-
 lated sensations come to be classified  primarily in conneation  with the senses
 through  which these come to be related to us.  Hence the fivefold classification
 of sensations in connection with smell, taste, hearing, sight and touch.  There
 is a sub-classification made  among the sensations that belong to a particular
 sense but this classification is  not particularly  important.   The sensations are
 found to  be of different degrees and they are always  regarded  from the stand-
 points of time and space, as  well as depending upon  different modes  of stimu-
 lation and  having associated with them certain  molecular, chemical and  other
 processes which form the  basis of the  special forms  that they   assume.   In or-
der to  have a scientific account of this field of sensations we  must, (1) separate
simple sensations from the complicated objective experience that  alone forms
the basis of popular  consciousness; (2)  distinguish the  varying quality and 
i (
quantity of sensations so as to  form some  idea of the  principles which deter-
mine the  relation of stimulation and  resulting sensation;  (3)  trace out  the
transformation of sensations into sense presentations  in  sccordance with the
psychic conditions of time, space and action;  (4) trace out the  relations of the
higher psychic activities to these sensations and sense  presentations and find
out if they are subject to the same principles.   Modern  psychology along these
lines has done almost all its work and  has gained  au insight  into  human ex-
perience impossible under the  old  psychology.  It is here  that  analytical in-
vestigation has been very carefully made to discriminate between the ideal and
the real and to separate  one form  of sensation from another so  as  to form a
purely physiological foundation for all  sensations.
    In the starting of this investigation it is  necessary to distinguish  simple
sensations from sense presentations including tlie complicated  objective exper-
ience  that really depends upon  a synthetic psychic procese^s. The simple sensa-
tion is unreal from the standpoint of  developed  experience.  They cannot be
examined independently and yet they are important elements in  the  sense pre-
sentations.   Any sensation  that is incapable  of analysis in  respect of  qualita-
tive distinctions and which from this standpoint does not consist of  more sim-
ple parts in a simple sensation.   A sensation represents an important element in
connection with an external object as related to us.  Hence every sensation is
a mental affection which we associate with some extra self ooject or subject in
connection with our own sense  activity.   The simple sensations therefore are
the simple elements of  sensations from which our sense presentations are built.
Our knowledge of the objective world of experience therefore represents the as-
sociation of these simple elements on the basis of definite space relations.   In
discussing the quality of sensations Ladd  says four questions arise,  (1) in re-
gard  to the  localization  of the particular sensations  in connection with the
body organism ; (2) in  the regard to  the  nature of  the stimulus   and how it
produces a specific form of  sensation in connection with the special senses; (3)
as  to the difference of the conscious  sensations produced  by these different
kinds of stimulation; and (4)  the principles  underlying the  sensations in  re-
lation to the  producing stimuli.   These questions  cannot  be fully  answered,
because of the complicated physiological and psychological processes associated
with  the production of all sensations.
     One law is taken for granted in these  discussions, namely the law of specif-
ic nerve energy.  The nerves  undoubtedly process certain common  functions;
   t the sensations involve in their  characteristic  distinctions  distinct neural
  \   ent« in order to furnish the  basis for the qualitative  difference of sensa-
       This differentiation is based essentially on characteristic properties of tl e
   a  ' yans and  the nerves, at least in their neural relations with the nerve
          What forms the basis of this differentiation is not known.
     s. }  Smell.   The smell  sensations  are  farthest  removed from psychic 
78
conditions and are much more difficult to consider scientifically  than the ot er
sensations.  The portion of the mucous membrane spoken  of as  regio-o ac-
toria embodies the smell end organs.   The  olfactory nerve is  diffused in bis
region.   This organ can be stimulated  only by substances carried upon the air.
In order to act on this organ the stimulation must be gaseous, as  substances
without any odor like arsenic when acted upon by  heat produce the smell sen-
sations.  Weber claims that the pouring of a fluid into the nasal cavities  does
not stimulate olfaction, probably because the fluid prevents stimulation Dy con-
tact, preventing  the odorous  substances from stimulating  the organ.   Some
claim that in fishes olfaction can be produced by pouring  into the nostrils cam-
phor solutions.  It is claimed by others that mechanical stimulation can arouse
the sense of  smell, such as is found in the case of extended  sneezing.   Ritter
claimed that by thrusting  pieces of graphite or zinc  into the nose  the sense of
smell could be excited.   Similarly the placing of the positive pole in the nose
produced an ammonia odor and the negative  pole a sour  odor.  It is probable
that in these cases other senses like the  tactile and feeling  sense are aroused.
We have no evidence that heat stimuli will  produce any  sensations of smell.
There is no direct evidence  that the  injection of odorous  substances into the
blood will  arouse the sense of smell.   Pathology  furnishes evidence that tu-
mors pressing upon  the nerve  of olfaction  may  give rise to odor  sensations
and undoubtedly in  some  cases of  insanity there arise subjective smells in con-
nection with the  diseased conditions of the nervous  system, especially  of the
brain.  We do not  know of  any special  property that must be possessed by
substances in order to excite  this sensation,  as we find in plants some odorous
during the day, others during the night. The principle element seems to be cap-
acity of vaporization readily  and  readiness to  diffuse in the air.   All bodies
that have an odor have the capacity, particularly when in contact with a  moist
medium, to arouse motivity in the medium so as  to produce  diffusion in the
air.   The sensations of  smell must be  carefully  distinguished from  the sensa-
tions of taste, for example ammonia  acts upon both  the trigeminal  and olfac-
tory nerves arousing the feeling sensations.  No successful classifications have
been made of smell sensations.
     (b)  Taste.   Our knowledge of taste sensations  and their stimulation is
very indefinite.  The stimulus necessary is  a tastable substance and it  must
act on the  end organs under definite conditions.  The substance must be  liquid
or soluble  in liquid as substances that are insoluble  are tasteless.   This may
arise from  the hidden position of the internal cells of the  taste  bulbs   which
can be reached only by soluble substances.   Not all soluble  substances  have
taste and no law can be laid down to distinguish between tasteless  and tastable.
It is disputed   whether the gases  can directly  stimulate the end  organs.  A
stream  of  C02 allowed to act on the tongue if in a  dry condition  has a sweet-
ish taste mingled with sourness.   It is difficult to state whether a tastable sub- 
79
stance excites all parts of the organ of taste.   The general conclusion is that
the tip of the tongue is the region of sweetness and sourness and the roots of
the tongue of bitterness and alkalinity of taste.  It has been found that  some
sugar derivatives produce bitter sensations at the root  of the tongue and sweet
at the tip of the tongue.  Here there are undoubtedly  individual peculiarities
which make it difficult to  limit the area of stimulation.  It is  questionable if
the sense of taste can  be stimulated  mechanically.   Some regard these sen-
sations as associated with tue general feeling accompanying mechanical  press-
ure of the  tongue  surface.   Electricity is found to  be the excitant  of  taste
sensations.   Rosenthal found that if the tongnes of two persons are in contact
while one holds the positive and the other the  negative electrode of a battery
there will be developed  in connection  with the  one  acid  and the  other an
alkaline taste.  In regard to the production of  taste sensations there seems to
be some  chemical relation between   the stimulating substance and sensation.
It is claimed that the simplest form of this relation is found in the case of acid
substances.  The compounds of  carbon seem to have the taste of sourness and
the soluble chlorides the salt taste while many of the alcoholic substances have
a sweet taste.   It is claimed that tastable  substances are carried  in a vibrating
medium  the vibration arousing a sensation in  connection with the sensative or-
gans, the vibration determining the quality of the sensation.   Certain  com-
pounds vibrating in a particular way produce certain sensations,  the  varia-
tions being caused partly by the inability of the tongue to analyze  directly the
compound  sesult.   It is usual to classify taste sensations under  the four heads
of sour,  sweet, salt and bitter.   Wundt adds to these other  two, the  metallic
and alkaline, all the other tastes being compounds of  these simple  tastes.  It
is questionable if this classification can be made to conform with experience,
because  many of the sensations  of taste cannot be analyzed into these simple
sensations, and the relation of taste  sentations to those of  smell and  touch is
such that it is very difficult to clearly differentiate them.
     (c)  Cutaneous and Muscular Senses.   The   sensations  of  tempera-
ture and pressure are localized  in the skin.  Other sensations supposed to be
localized in the skin,  called the common sensations,  including pain, pleasure
and  the  delicate forms of tactile sensations,  are all  more or less  closely re-
lated to  pressure and  temperature.   Some of  these are undoubtedly to be lo-
calized in the cerebrum arising from the  combination of  a variety of the sen
sory impulses, the  combination taking place cerebrally.  The pressure sensa-
tions are aroused by the stimulation  of the sensory cutaneous nerves.  If  the
main trunk of these nerves is stimulated  painful sensations  result but these
are distinct from the  localized sensations.   Tue normal stimulation  consists
of compression or extension  through contact  with something   external,  the
degree of the stimulation depending upon  the nature of the pressure  and its
continuance.  There  is really no scientific classification of these  sensations, 
80
although sometimes they are distinguished as simple touch and  pressure or
weight.  This distinction however  is one simply of degree.  The  pressure
sensations arise in connection with the slimualtion of small pressure  areas,
which  are found in chains radiating from a cen. '*al point,  being  found most
abundant in the  skin where it is extremely  sensitive  to pressure.   Two
quite different sensations are distinguished in connection with pressure.  It
a very delicate pointed instrument touches the skin it will arouse a sensation
only at special points,  resulting in a gentle prickling sensation.   If the pres-
sure is increased the  sensations are altered,  so that the feeling  produced is
that  of   a solid substance  pressing  against the skin.  If the  intervening
points between the pressure spots are stimulated only an indefinite and char-
acterless  sensation  results.  In  quality  sensations of pressure cannot b"
classified,  the complex as distinguished  from the simple  sensations involv-
ing, muscular and articulation sensations, the difference being  in the inten-
sification  of the complex as  compared with the  simple.  Some have  identi-
fied the simple  pressure sensations  with those of temperature,  cold sub-
stances in contact with  the skin having the feeling of a heavier  weight  than
warmer substances.  It is claimed that a  silver dollar at 25 ° F is as heavy
as two dollars at 98 °  to 100 ° F.  Certain minute  areas and those only are
subject to irritation of  a kind to result in sensations of heat and cold.  It has
been found  that small wood  discs at  122 ° F have the feeling of a greater
weight than larger discs quite cold.  The fact that the pressure spots and the
temperature spots may be stimulated by  the same excitation  does not prove
that they are identical.  Hence the temperature sensations are quite  distinct
from the pressure sensations  and are aroused only in connection with minute
cold and heat spots.  These  minute spots of  sensation are  distinguishable
from one  another on the cutaneous surface.  Their localization  is not sym-
metrical on the different parts of the body and they are found to  be  different
in different  individuals.   They are found in radiating chains of spots radi-
ating around the roots of the hairs.  The  cold spots are more abnndant than
the heat points.  Some spots  are aroused by  a temperature that would not
effect others.  When the spots have been aroused the sensations become  spe-
cific, the sensations having,  it is claimed, a certain dependence  on  the tem-
perature of the stimulus.  Hering claims  that when the stimulus at  a point
in the  skin has a temperature higher than its own zero-point there  is a heat
sensation, and vice versa a cold sensation.   The zero point  of  the skin applies
to the temperature which will not produce a sensation of either cold or heat,
differing for the different cutaneous parts.  Hence the tip of the nose rep-
resents a cold part  because there is in connection  with it a  loss of  its own
heat by radiation.   Hence  there is a   mechanism of  adjustment  regulated
mainly by the  blood supply   and the principle of  evaporation.  Hence heat
may be induced,  by checking the radiation,  being in contact with a  higher 
SI
  temperature and the passage of  heat from the  interior to the exterior  of the
  body; cold may be induced by promoting radiation from the skin,  by contact
  with a lower temperature and by diminishing the internal  temperature of the
  body.  It is almost impossible to reconcile the psychic principles of tempera
  tare sensations and the  physical principles of  physical heat  and cold at the
  basis of which is motion.  The psychic  principles have a great deal  to do in
  determining the character of the sensations.  The sensations of temperature
  depend on the temperature of the stimulus,  the rise and fall of temperature
  and the principle of nerve fatigue,  particularly applicable to the terminal or-
  gans,  bring out many of  the phenomena of  sensation.   Weber thinks that
  wherever there is a rise in the  skin  temperature  the feeling of heat results
  and vice versa.   Goldscheider however  proves that by holding the  hand for
 ten seconds in water at 104 o  p and theu pladng both jlands in ^ water ^
 hand that is cool will feel the cold water  more distinctly  than the  warmed
 one.  The perception of variations of  temperature is keener for a  tempera-
 ture close to the normal,  although we do not know why  it is so.   It is  pos-
 sible that certain chemical  changes or electrical  variations take place on the
 basis of heat changes in connection with stimulation.  It is certain  that sen-
 sitiveness to heat continues after the  cold sensitiveness  is lost.
     It is much disputed whether excitation of the sensory  nerves in connec-
 tion with the muscles gives rise to muscular sensations.  We  localize in  con-
 nection with the muscles certain sonsations particularly in connection  with
 movements and the vision.   This is clearly observed in lifting  weights  and
 changing body positions in which muscles are brought into play that are not
 used  normally in ordinary  movements.   There  are undoubtedly  muscular
 sensations in connection with the conscious mind, these muscular  sensations
 supplying the  sensations of pressure in connection with the skin with greater
 definiteuess as the basis of movements.   It is impossible to account for  deli-
 cate muscle movements on any  other basis.  In case of  loco-motor  ataxa
 there is often little absent but these muscular sensations.   There may be a  loss
 of skin sensibility without interfering  with the power of lifting weio-hts   and
 distinguishing their masses.  It is not known how the  muscular  sensations
 arise, possibly  it  may consist of some chemical or  mechanical  stimulation.  It
 is impossible to analyze and classify these sensations because to the  conscious
 subject they are complicated  processes associated  with pressure and tempera-
 ture   sensations   and   also   with   the  sensations  of   sight.   These
 muscular   sensations   differ   in   quantity   rather  than   in   qual-
 ity  from  each  other.  In  connection  with  the  body we also find artic-
 ulation sensations particularly valuable in body movements.  It has been found
 by experimenting in connection  with the index finger that sensations   arise in
connection with  the joints that deteimine  our perception of movements.  It
has been found that  manifold cutaneous sensations exist over the surface of the 
82
 body,  great variations being found at  different points,  when a  uniform cur-
 rent of electricity is passed over the surface,indicating the variety of the forms
 assumed by sensations in connection with the body surface, all of these bewil-
 dering sensations being analyzed and combined  in consciousness.
     (d) Sound.  In connection with these sound sensations many  investiga-
 tions have been carried on since the time of  Helmholtz.   It has not  yet been
 definitely  settled where the  stimulation takes place  in connection  with  the
 neural mechanism nor in what way. Sound implies vibration and this  vibration
 in some way produces a stimulation that affects consciousness through  the nerv-
 ous mechanism,  involving the excitation of the auditory nerve  and the  cere-
 bral auditory apparatus.  Psychologically sound is therefore purely subjective
 although the ear possesses the capacity of analyzing sound as perceived but this
 does  not give us any means of analyzing the  process of aduition or the way in
 which vibration  excites it.   Sounds  are divided  into two classes,  noises and
 musical notes.  In the former is the  lack of periodicity in stimulation  such as
 we find in the latter.  It is true that in  all tones there is an element of  noise
 and even in the most ungainly noises a trained ear could detect  musical notes-
 According to Helmholtz noises are characterized by rapid and alternate  varia-
 tions in different  sounds.   According  to Hensen  there are three  classes of
 noises, beats that interrupt musical tones; crackling and hissing sounds.  The
 musical notes differ in quality and also  in quantity depending on the  extent of
 the vibrations causing them.  In regard  to quality they are  either simple or
 complex as they are produced by one set or  more sets of periodic  vibrations.
 In tne complex sound there is not such  absolute, blending of simple sounds as
 to be incapable of  analysis  on   a simple basis.  The complicated  sound pro-
 duced by this blending of simple sounds in contrast with one another is termed
 clang.  From  the  standpoint of the simple  sensations  we have  the  pitch
 which represents the quality of the sounds,the pitch varying as we give our sen-
 sations a particular place in  consciousness and compare them objectively  from
 the standpoint of  the number of  vibrations producing  them.  The  complex
tones  of our experience also  vary in quality, this variation being  called the tim-
 bre which depends on the pitch,  the number and intensity of the simple tones
 of which it is composed.  The pitch  of  the tone produced  by the voice or the
piano is the same, but its timbre is different  depending on  overtenes that are
associated with it in connection with the fundamental tone.  The pitch  is de-
termined in the case of a simple musical tone by the posttion we give it in the
scale, so that the pitch is either high  or low.  The pitch however  depends on
the rate of  the periodic vibrations producing the  notes or the   length of the
sound  waves.  Vibrations that are beyond or below a certain limit of vibration
per second give no musical sounds or  at least sensations of  them.  The pitch
is regulated by the measurement of  the number of  vibrations required to pro-
duce some fundamental sound  which is taken as a keynote,  the other sounds 
S3
being determined in  relation  to this one.   The German scale  fixes its key at
440 vibrations per second,  the French scale 435  and the English  512.   It is
difficult to determine the limits of sounds that produce  sensations on account
of individual "idiocyncrasies.   Helmholtz considered  that the sound begins to
die if the vibration is below 34 per second,  while Preyer could hear sounds at
16 and also at 40,000.   For normal ears the  limits may be set at from 28 to
22,000, although variations  may be  admitted  for 20 to 50,000 vibrations per
second.  The normal ear would be capable of  heanug a  little over 9 octaves
of pitch.
     Great differences are found in the sensitiveness  of  individual eais to dif-
ferences of pitch, some being  entirely deaf to differences in pitch.  Those who
are not sensitive to a difference of a half  tone are said to be incapable of dis-
tinguishing one note from another.   Sensitiveness  can  be cultivated  very ex-
tensively and to such  a high degree that variations  may be detected of one-
third of a simple vibration.   There is also great difference in individuals in the
power of discriminating the intervals between notes.  The delicacy of  the sen-
sations of sound may be illustrated in the fact that the  discrimination  between
two notes from the standpoint of pitch is independent of everything outside of
the sensations produced by them  Hence the mind must possess  the power of
immediately discriminating between differences in pitch, although training may
considerably intensify this  power of  judgment.  This training may be  aided
by the delicacy of the muscular sensations which arise in  connection  with the
larynx in the act of singing.   These sensations however of themselves  could
not supply  the basis of judgment, the variations in the quality of the musical
tones supplying the means for bringing them together in a series  called a scale.
The symbolism made use of in connection with varying  positions in a straight
line  depends on sensations arising in  connection, with touch,  vision and the
muscular sense, on  the basis of which we call the sounds high or low and des-
ignate certain intervals  between the notes.  In  the lower tones  the  sound is
produced in  connection with  depressed  vocal organs, in the higher tones the
vocal orgaus are elevated.  Hence lower notes in connection with consciousness
impress the mind with ideas of breadth and gravity, more time  being necessary
for their entrance into and passing from  consciousness.   By sounding a note in
connection  with the voice or an  instrument there is a clang,  producing by the
summation  of the simple note qualities in connection with consciousness a sen-
sation which is complex, the result of a complex undulation sound.  Hence the
clan^- represents the blending in consciousness of the simple  tones  found in
      '  i    ,„,TO   When simple  tones by their vibrations are related to one an-
a complex wave.  »* u^"   r        ^
other tbev produce in  consciousness the pleasing sensation accompanying a har-
        •f the combinations however are related in an  unharmonic   relation they
m°n^ -e the  unpleasaet sensations caused  by noises   If severul   clangs  are
Pr   i  i of tb« same time a complex  sensation  follows, which may represent
sounded <n- i" 
84
 consonance or the complex fusion of pleasant sensations, and may also  repre-
 sent dissonance or the complex fusion of unpleasant sensations  Thus we have
 complex sensations psychically corresponding with the chords and discords of
 sound.  Helmboltz thinks this depends on the  fact that  beats are present or
 absent, consonance resulting from the absence of beats.   To this is added the
 idea that consonance involves pleasure  because of the  "recognition of rela-
 tions."  In other words consciousness recognizes the  relation of the sound to a
 fundamental note  and  also recognizes in the consonant notes a harmonious
 action arising in  eonnection  with the notes themselves.   From this we may
 infer that the ear as the organ of hearing represents the most acute and analy-
 tical of all the senses to appreciate these minute auditory differences.
     (e) Sight.  The sensations of sight are the  most complicated of all the
 sensations.  There is really a two-fold sensation  involved in sight,  that of
 light and color;  and as there exist different shades of color and  many vari-
 eties of light  sensations,   the sensation of sight  comes to  be very complex.
 Qualitative changes depend upon a number of causes that  are indistinguish-
 able in consciousness.  The quality of the sensations also depends  upon the
 quantity of the white light that is brought to bear on the  eye in connection
 with any specific  color.  Limiting the  investigation  however we  enquire
 into the sensations arising in connection with the  stimulation of  a small part
 of the central portion of the retina when the light k normal.  This will give
 us the normal visual sensations.   Light is the normal stimulus, but the same
 results may be produced by electrical or mechanical stimulation.   The retina
 is said to be  continuously active  and thus possesses  its own  characteristic
 light which varies considerably in quality and degree.  As  it is  preserved in
 a tonic condition of stimulation, this depends upon the blood supply  and the
 chemical changes taking place  in the terminal organs and the brain in connec-
 tion with the blood supply.  It is in connection with the rods and cones that
 the light sensations are produced.  This retinal layer consists of a large num-
 ber of distinct elements each of which is sensitive, the one side of which is
 stimulated and the  other responds in connection with the sensations of  light
 and  color.  There must be the irritation of two contiguous retinal elements
 in order that two visual sensations  may be seen separated  from each other,
 so that stimulation must  take place over a  retinal surface equivalent to the
 distance between two such  retinal elements.  The trained   eye  can attain a
 degree of accuracy according to the size of the retinal elements, so that in dis-
 tinguishing two objects there requires to be a separation of 60 to 70 sees, the
 angle represented by  this distance  being about the siee  of one of the retinal
 elements.   If on  a  dark surface white  lines  are  drawn so as to come closer
 to each other than this retinal limit to the vision they will appear  distorted.
This arises from the effect produced by the stimulus in connection with the
rods and cones. 
85
    In connection wTith sight sensations we require to consider the wave lengths
that  are associated vrith the different kinds of colored light and the component
elements of the colored light in connection with white and colored light. There
is a marked difference in color tones,  light being the normal stimulus  upon
the end organs of vision.  In the  case of the rods and cones the real stimu-
lus is the photo-chemical changes taking place  in connection with  the light.
These changes producing  sight sensations  may be aroused by mechanical
pressure or by electrical  stimulation,  while in  some cases a sound  heard by
the ear produces the eensation of a particular color.  Color tone is spoken of
as pure in  case it is not  mixed with the other color tones,  this distinction of
pure color  tone being obtained only in connection with the  spectrum.  In the
use of it the compound white light may be analyzed into its component  color
tones, so that the compound of sunlight rays in connection  with the stimula-
tion of sight sensations consists of several  constituent elements which rep-
resent vibrations of a certain magnitude varying from  370 to 900 billions per
second.  According to Frauenhofer light rays consisting of less than 450 bil-
lion  oscillations per second, give rise to the sensations of red, varying slight-
ly in quality up to 470 billions; after 470 billions is reached we have orange
yellow varying up  to 526 billions when the characteristic yellow is produced;
above this  the green sensations originate until  589 billions is reached, when
the sensations begin to become blue varying in  quality to 640  billions;  from
this  up to  722 billions the variation of blue to violet takes place above which
there is the characteristic violet.  There is the gradual variation from the red
to the violet so that no  sharp distinction  can be drawn between the spectral
colors.   In the ultra red the rays do not excite  retinal action.   In the  ultra
violet Helmholtz discovered the lavender  grayish color,  and  in more recent
times the X radiance represents the  ultra violet color.  The sight  sensation
represents an  image of   external things which  comes into  consciousness
through the optic avenue to the brain.   Hence all the sensations coming  from
vibrations must be purely psychological.  Light reveals wonders  of the uni-
verse and  yet it  is itself the greatest wonder.  The eye is not as expansive as
the solar universe  of radiation.  Hence we find  in the ultra violet  spectra of
color unknown to  vision.   Stokes points out ten variations of color ultra vio-
let and Muller has pointed out twTo ultra red, these representing a fluorescence
created so as to render the light visible.   Hence Tyndal claims "beyond the
extreme   violet    of    the    spectrum   there   is   a   vast   efflux   of
rays  which   are   totally   useless   as   regards   our  present  pow-
  is of  -vision."   Lenard  regards   the   cathode   rays   as   essentially
  f  the  same nature   as  the ordinary  light  rays  and  Hertz has proved
that the cathode rays pass  through the delicate metal  sheets inside the tubes,
  . ssinir through substances opaque  to ordinary light.   Hence in this ethereal
   dium «e find  the perfect adjustment of molecular relations.   In  the X ra- 
86
diance we  have an  anti-cathodic ray ©f light arising  from the  spot of fluo-
rescence on the glass surface opposite  the cathode plate.  This light cannot
be utilized by ordinary vision without the aid of  a phosphorescent  medium,
demonstrating  the existence of  other  media  for the  transmission  of light
waves to the end organs of light sensations than simply the retinal rods and
cones.  The color sensations originating in connection with the green-yellow
of   the  spectrum  are   brighter than  the  other  eolor  sansations,
this  being   generally   acknowledged   to   be  due  to    the   retinal
structure  and  its   sensitiveness  to  these   color  rays.  We   find
also  different  degrees of  sensitiveness in the retina  to different  and very
slight variations  in the quality of the color tones.  The  sensations of  color
are not  simple but complicated and the  analysis of these complex sensations
is impossible,  because they retain in consciousness the characteristics of the
color tones.  When only  slight  variations exist  in  the wave  lengths of
two colors the variations can be recognized as  shadings of  the colors.  There
is not a difference in the color  impressions resulting  from a mixture of  the
colors,  the character of the color impressions  depending on the  spectral po
sition from which the color tones are taken and on the intensity of these color
tones.  According to Newton an octave of seven colors is  distinguishable by
vision, red,  orange,  yellow, green, blue, indigo and violet but there is no
foundation  for the analysis,  because some of them  like indigo and  orange
really represent  semi-color tones and not color  tones.   A great number of
color tones are discernable in vision so  that if  all differences are considered
many thousand color tones may be  distinguished.  By uniting  certain color
tones on the retina there is a resulting color  sensation quite  different from
the sensations of  the two separate; the former sensation is called white and the
separate sensations complementary.  The mixture may take place by placing
one spectral ray upon another,  by the fusion of the  reflected images of two
colored  wafers or by the fusion of colors in connection  with a revolving cylin-
der.
    If the light intensity approximates  to  the highest or lowest  point there
is an  important variation in the quality  of the sensations that does not depend
on the changes in the wave lengths.   When the  stimulus reaches its maxi-
mum there i3 an entire loss of  color tone,  the sensation being that of  white
light,  before the maximal  point is attained red and green tones become yel-
low; when the stimulus is at its minimum all the color  tones except red cease
to possess color, if upon a dark background.   There are color tone variations
when the period of the stimulation of the retina by the light falls to its low-
est point.   A certain duration of time is necessary  for the light  sensations.
If the color is saturated sensations  may arise  from an instantaneous  spark,
but if the light intensity decreases a longer period is necessary.   The quality
of the sensation also varies with the part of  the retina which  receives the 
ST
light or color stimulation.  The whole retinal field is divided into three areas
called central, middle and outer.  The same stimulation may produce sensa-
tions varying in quality and intensity.   The  retinal sensitiveness  is intensi-
fied towards the outer part,   the lower portion being less  sensitive than the
upper part,  possibly because the rodlike structures mirror the light.
    In some individuals defective vision  is found the whole retina being found
to be similar to the outer portion of the retina, and hence  imperfect in retinal
function.  Among some persons the retina is either partially or wholly  non-
sensitive to  the red lays, confusion being found between the red and  the yel-
low or green.  Among others the retina is either partially or wholly non-sen-
sitive also to the various shades of green.   Hence  according  to Kries color
blindness exists either in regard to red or green. The e^e vision may be modi-
fied in connection with the retinal condition either as found before or  during
the time when  the rays  of light  fall  upon the eye.   In these cases  there is
usually a brain condition behind this abnormal variation in the  sensation that
is itself abnormal, although  it is claimed  by some  that it depends on  the
chemical nature of the stimulation. By fixing the eyes  on an object particular-
ly if bright colored and then  closing the eyes there is still kept before the eyes
a picture of  the object, called a positive after  image, which  only gradually
fades from the vision. By a continued consideration of this image the colors are
changed, white becoming greenish blue, then indigo blue and then a deep vio-
let color.   If the eye is fixed  for a length of time on a  green  object and then
changed to  a  white  object,  the color  of vision becomes red.  This image is
called the negative after image and depends on the law, that  the color of the
image is the complementary color of the object, that the blending of the colors
of the image and the object would produce white.  These after  images are said
to depend upon   fatigue of   the nerve elements  so that when the color is pro-
longed in its relation to the retina the retina becomes insensitive to that color
uutil the exhaustion is removed.  If a bright object is surrounded  by a darker
medium it appears brighter and vice  versa.  This depends on the  principle of
contrast.  If colored light takes the place of white light then the clmplemental
colors are found. The explanation of these facts seems to depend on the physiolog-
ical principle that when one point of the retina is stimulated there is a radiation
of excitation to  neighboring parts of  the retina, while at the  same time any
one point on the retina is modified by the surrounding retinal parts.  In addi-
tion to this  there is undoubtedly an influence exerted  by the cerebral centers
in connection with the optic  connection.
    On account cf the complication involved  in  the visual sensations  it is  diffi-
cult to find   a theory  that will take  in all the  phenomena.  There are many
facts that require to be explained,  for example the principles  upon  which the
  ' 'tive colors can be built  up into color tones; the relation of the color tones
   tl e light  intensity; the relation of  complementary colors to white  light and 
 the phenomena of after images and comparison.  Among the theories propound-
 ed the most interesting  is  that  known as the Young-Helmholtz theory.  It
 originates from the fast that the mixture  of certain  primitive colors  produces
 all the other color tones.  According to  this there  are three  primitive  colors
 green, red and violet or according to Fick blue.   On this basis  it is claimed
 tbat three nerve  elements are found associated with every  part of the sensi-
 tive  retina, so  that  the  stimulation  of  any of these elements singly would
 produce a primitive color tone, so that in the retina we find the  green, red and
 violet color elements producing corresponding sensations.  In  every  visual
 sensation  we find a complexity of  elements so that  the complex  sensation de-
 pends upon the relative intensity of the  constituent  nerve elements.  In this
 theory we find a very plausible explanation  of the visual sensations, particular-
 ly in  connection with the  mixture of colors.  The greatest difficulty  arises in
 the attempt to explain color  blindness which according to some is  irreconeile-
 able with this theory.  It is  claimed  that the lacking colors do not correspond
 with  any of the fundamental  colors, as persons  who are red blind  ought to
 see the  white  color  tone as green-violet.   According  to Hering  who rejects
 this theory, the variations in the sensations of gray color from white to black
 correspond with the quality of sensations produced by the eye  looking upon the
 different color tones that  shade into each  other.  Hering claims  that we have
 three double primitive colors the mixture of which produces all the color tones
 black and white, blue and yellow, green  and red.  According  to him  a con-
 structive process  produces the  first color  tone of  the pairs, black,  blae and
 green; while a destructive process produces  the second color tones of the pairs
 white, velloTv and red. Hence he bases the double color tones in  each pair on
 the principle of antithesis.  According  to Wundt the  processes  differ  rather
 than  the  primitive elements of  the retina.  According  to  him the  retina  is
 continually in a condition of  stimulation or  tonic contraction,  corresponding
 with the sensation of darkness or the color tone of black.  When this is mod-
 ified by an external stimulation  there are two processes  found in  connection
 with the retina, the one a chromatic or color  process, the other an  achromatic
 or colorless process,  both of them  depending on the  length  of the waves
 while  the latter varies only in intensity. Thecolorless process retains throughout
 the same character, being  photo-chemical, yellow representing its maximum and
 the two ends of the spectrum  variations  towards a  minimum.  The color pro-
 cess is also photo-chemical and varies with the wave lengths.   When the stim-
 ulation  takes place in connection with a stimulus, the stimulation stops  before
 its effects cease in  connection with  the  irritation  of the  nerve  elements and
 continues the irritation until the  nerve  elements are exhausted in  connection
with this form of excitation.   Contrast is explained according to Wundt on the
basis of relation in connection with the activity of the  cerebral  elements, the
positive and negative  after images depending on the continuance  of the retinal 
89
the comparison is limited to variations  in the sensations of the  same sense.
There is an interdependence of quantity and quality which makes it more dif-
ficult to make such a measurement  but this does  not abolish  the scientific
analysis of the elements of our sensations in the ordinary experience.  Exper-
ience however analyzes these sensations in a very inexact way; we may be able
to say that one sound is louder than another, but  precisely what  the variation
is   it   is   difficult   to   determine.   This  complication   is   increased
when  we  consider   the  variations   in  quality  and   the   comparative
intensities   of   the   sensations   of   different   senses.  It  is   only   in
musical   tones   that   we   can  analyze  and   compare  the  quality  and
quantity  variations.  If   sensations  are  quantitative however  they  must
admit of  some  degree  of  measurement.  The  sensations  however repre-
sent not   objects  but modes of mental action that are aroused in  connection
with nerve activity.  In connection  with the quantity of sensations we must
find out the limitation imposed upon variations in connection  with the sensa-
tions as they belong characteristically  to the  special senses; and  inside these
limits there must be certain principles  regulative  of the  variations in  sensa-
tious.  The  sensations,  although  they cannot be  measured  by  the physical
yardstick, are yet the result of  certain stimuli that are brought to bear on the
stimulation  and the retinal exhaustion.   According to Kries the visual sensa-
tions are photo-chemical and this prevents us from regarding the  changes as
Wundt does as simply qualitative.  There are certain components at the basis
of all color sensations and the proper combination  of these components gives
the color-tone.  This adjustment takes place in connection with the central sys-
tem, but in what way we cannot tell.
     Many attempts have been made to invent a  scheme for the  purpose of
visualizing the colors so as  to  represent them to  the eye.  Among these we
have the color triangle and the color wheel; in the former the color  tones are
represented as lying around a curved  line ranging  from the  one end  of the
spectrum to the other; in the latter case the color tones  are represented by two
concentric circles, the  complementary colors being contiguous in the corres-
ponding arcs of the two circles.   These symbolic representations  however are
of little value from a psychological standpoint.
     The Quantity of Sensations.   Not only do we find variations  in  quality in
sensations but  also in quantity.  The sensations  when they  appear in con-
sciousness  not only  differ as to their  production but  also in the degree  in
which they  absorb the conscious attention. When a sound is heard like that of
a church bell as we come near to or more away from it, we perceive variations
in the intensity.  The  same element of quantity  in sensations is  found  as-
sociated with  touch, pressure,  temperature, etc.   These quantitative changes
depend upon changes in the specific character  of  the sensations.  The meas
urement of these varying quantities in sensations  cannot be exact, even when 
90
 nervous mechanism, the variations m sensations corresponding  within certain
 limits to the intensity  of the stimulation.   The  changes of stimuli can be
 measured, and the resulting sensation changes  can also be  measured by  dis-
 criminating the intensities of the sensations.   We must in order to  solve  this
 problem, (1) determine  the maximum and  minimum  stimulation  that  will
 occasion the  maximum and minimum sensation, in order to settle the limits of
 variation in sensations;  (2) try  to find a principle that will  determine the re-
 lations of stimuli and resulting sensations.  Here of  course  great difficulty is
 met with because it is difficult to measure subjectively the sensations  in inten-
 sity and objectively the quantity of the stimulus.  It is  possible to determine
 in the case of two sensations of the  same quality  produced by a quantitative
 stimulus that is the same or nearly alike in both  cases, the resulting  intensi-
 ties of the two sensations in consciousness, so as to determine what  is called
 the minimum of  observable difference.   This  is taken to be the great  question
 of quantitative analysis of sensations, namely, the observatiou of the minimum
 observable difference  in quantity for the different kinds of  sensations.  This
 minimum of observable difference is itself an ideality and must be regarded as
 such in its bearing upon mental processes.   In determining the  minimum of
 stimulus necessary to produce a sensation, a stimulus that is slightly  stronger
 than that necessary in the production of a sensation  may be  applied, gradu-
 ally lessening the stimulus till the point is discovered where the  stimulus pro-
 duces  no sensation ; on  the other hand a  stimulus may  be applied  that pro-
 duces  no sensation and we  may increase  it gradually  to the point of producing
 a sensation. In determining the maximum stimulus which produces a sensation,
 we meet with the difficulties associated with fatigue and  over-exertion, as well
 as the elements of  pain that make it impossible  by experiments to  determine
 this higher limit.
     In connection with the determination of the minimum  of observable dif-
 ference in sensations,  Ladd mentions three methods.   (1) According to Wundt
 there are two ways of  applying  the method of least  observable difference,
 either by the  formation of a gradation series of stimuli with intervals  of time
 corresponding  with the  intervals  between the sensations,  so as to  determine
 the variation  of stimulus necessary  to divide the  interval of time  in two  con-
 tinuing this process of division  until the least  observable difference is   found •
 or we may construct a scale of stimuli  with varying  intensities just sufficient
to give a variation in the resulting sensations.   (2) The average  error method
first determines a standard sensation produced by a  definitely known stimulus
after which an attempt is made to determine another  stimulus that will give a
sensation of exactly similar intensity.   By making an average of  these combi-
nations determination is made of the least observable difference.  (3) A given
stimulus is taken  with  a resulting sensation, sight additions and  subtractions
are made so as to vary the  stimulus,  with the view of  guessing at the result 
91
associated with the changing stimuli.  All these methods attempt to  measure
the mental  sensitiveness to small variations  in the sensations corresponding
with variations in the stimuli, without taking account of the other elements
aside from purely  objectiye changes that  determine the  sensitiveness of the
mind.   Weber has formulated a law based upon many experiments and Fech-
ner  has enlarged and  corroborated  it.   This represents the only scientific
statement we have  on this subject, namely, that our consciousness  of the dif-
ference   quantitatively between  two  sensations is  not  in direct proportion  to
the difference of stimuli, because the intensity of the stimulus increases  more
rapidly  than the  resulting  sensation.  If the minimum observable  difference
it regarded as constant, then  in order to  get an  increase or decrease of sensa-
tion, there is required the addition or subtraction of a larger amount of stimu-
lus  in  the upper  than in  the  lower scales.   The law of  Weber  attempts  to
measure the difference.   It claims that "the  difference of any two  stimuli is
experienced as of equal  magnitude in case the mathematical relation  of these
stimuli  remains unaltered ;" "if the intensity of the sensations is to increase by
equal absolute magnitudes, then the relative increase of the stimulus  must re-
main constant, the strength of  the stimulus must ascend in a geometrical pro-
portion in case the strength of the  sensation  is to increase in an arithmetical
proportion."  The law seems to be applicable to a certain field in  the scale  of
sensations,  but  inapplicable  to the  larger  portion of the  field in  connection
with the higher and lower limits of sensations.
     In regard to the tactile sensations of pressure the minimum of observable
difference is subject to much  variation, in< luding the  effects of the muscular
and temperature sensations the  region of fhe application  of the stimulus and
the time intervening between the stimulus and the sensation.  Experiments
indicate that the sensitive quotient for pressure sensations depends upon the al>
solute weight values that are made use of.  As the  weights increase  the quo-
tient varies and  the observable  difference varies with the  rapidity  of the rise
of the  weight.  The  differences of sensitiveness in the  different parts of the
skin depend on  sensitiveness of the  nerve elements, skin thickness, skin ten-
sion  etc   In regard to the temperature  sensations it is almost impossible to
findout what is to be measured, the  zero point of  the skin  varying so much.
It seems that greater sensitiveness exists in  the skin close to the zero point,
the least observable difference being found slightly above and below the zero
   • t    Temperature sensitiveness depends on the extent  of the surface  irri-
tated and its  localization on the body surface.  The differing degrees of sen-
sitiveness can be  mapped out in  connection  with the cold and hot spots.
H      the intensity of sensitiveness is great to cold  on the forehead  and on the
,   i  •  tMflp tn  heat on the chest except the sternum, equally intense to cold
back, intense iu  u
   ri h  t on the hands.   In regard to the sound  sensations the  variations in
the se
ations do not  correspond directly with the  changes of stimuli,  other- 
92
 wise delicately shaded musical sounds  would be impossible.  If the intensity
 of a sound is increased the timbre is modified.  The Weber law  does not seem
 to be generally applicable, as in the  upper and lower   limit it fails altogether.
 Aural sensitiveness for minute tone variations is  much greater  than for  noise
 changes.  The minimum of observable difference in sound depends on the con-
 dition of the medium, so that if almost absolute stillness  prevails very minute
 variations may be detected.  The psychic  element of  habit  explains the fact
 that some sounds fail of detection that would  otherwise attract  attention.  In
 regard to sight sensations, the astronomers early pointed out that the  minimum
 of observable  difference  in connection with two  sight sensations  is less for
 those that possess the minimum of intensity.   The fact that  the retina has its
 own light and that qualitative variations   tend to hide  the quantitative  varia-
 tions makes it difficult to  measure  the sight  sensations.   The back ground in
 connection  with   which the color tones are  exhibited also is very important.
 According to the early  application of the  Weber law the  minimum  of observ-
 able difference is .01, more recent experiments indicating a variation from .015
 to .005.   In regard  to the  light and color  sensations  Weber's  law maybe
 said to apply generally when the stimuli are in  the middle of the scale and in-
 applicable in the  upper and lower limits.   In connection with the taste sensa-
 tions such variations are found in the  stimuli conditions and  the  individual
 element is so  strong that nothing  definite can be stated  in regard to the min-
 imum observable difference.  In the  seusatious of smell very  minute differences
 can be detected, so minute as to  indicate  almost  inappreciable  points of dis-
 crimination, the  element of quantity in  the stimulus   being capable  of very
 fine differentiation.
    According to the Weber-Fechner law  there is a variation  in the  quantity
 of sensations arithmetically and in the quantity of the stimuli  geometrically.
 This represents only one principle  that may apply within certain  sensation
 ranges when no external disturbing  elements are found.  Fechner applies this
 law to interpret  the relations of the bodily and spiritual activities,  making
 this the foundation of many of the relations of mind and matter; others apply
 it as a physological statement of a neuro-physical relationship between stimu-
 lation applied to  the body and the neural  commotion   resulting from simula-
 tion.  Undoubtedly the organism is  excitable and this would represent  one of
 the modes of stimulating the organic elements to activity.  In addition to this
 there is a psychic side, because all of the mental states are definitely correlated,
 so that the value of one mental state  can be determined only by considering this
 correlation.  The mind  appreciates the  variation in sensations  but so  many
 elements of  a psychic nature are  involved, including attention, judgment, habit,
that it is  difficult  to reduce it to arithmetical form. The relation of the internal
and external variations undoubtedly  exists, but we cannot as yet  at least form-
ulated in precise language.   Where interruptions exist between these or abnor- 
93
mal conditions are found in the correlations of mind and body such as  we find
in insanity, we have here a plrysiological  basis for Osteopathic  education ap-
plied to the organism with the view of the re-establishment of the normal corre-
lations that are at the basis of sane life.
    Sense Perception.   The sensations and their interpretation imply very
different things.   The sensations imply the  consciousness of the affection of
the nervous system.  But the  affecting objects are considered as real  things
and hence are said to possess objective existence.   Hence sensations  represent
psychic conditions which have   no space  form, but the objects  giving rise to
these sensations  are regarded  as  having a space form.   The   mind is sub-
jected to the influences of certain stimuli and it interprets these stimuli by giv-
ing to them certain qualities as objects of perception.   The perception of such
objects is not native to the mind but the result  ot certain educative process in-
volving a knowledge of time and space relations.   In order to mental  percep-
tion there  requires to be  a  constructive process for  things  can  only be per-
ceived when formally constructed.   This  construction process   is not indivi-
dual only but hereditary and racial.   It is impossible  to formulate a  theory of
perception that will account for all the processes associated  with our knowl-
edge of the external world, because it is impossible to  analyze all the complex
processes by which  the individual  has constructed  this world of experience.
Hence the contents of consciousness cannot all be traced to their genesis.  We
must try to find if any physical  basis can be  found for this constructive  pro-
cess by which psychically the field of perception assumes its  spatial form.
     Sense perception involves so many complex processes that its analysis is
impossible.  When the eye looks upon a  scene there is  the  consciousness of
something being impressed upon us mentally that has  an  exact  counter part
outside of us. Commonly  these external factors in experience are  adjudged the
only basis of mental perception.  These external   things and beings  however
do not explain psychic perceptions but only   furnish stimuli that  may or  may
not affect us.  This affection takes place in  connection with the  nervous sys-
tem but there must  be in addition certain  psychic activities to   construct the
mental perceptions.  The old theory of spiritualized  or ethereal  transforma-
tions of the external passing through  the senses and  forming the basis of psy-
chic perception has no foundation.  The conditions and processes of the body
itself cannot furnish any adequate explanation of the perceptions.  The physi-
ological theory according to which the physiological changes produce  the  psy-
chic changes is also inadequate.  The  retinal image for example  is a  physio-
   •   l    idition of perception but it is not a picture for the mind  itself.  Psy-
 •h^ictures cannot be constructed  out of physical or physiological elements.
°'- 1C-i   - 't is inadequate   to localize space in  connection   with the peripheral
        "   „„flC in  connection with  the external stimulus, because in this case
sensory nerves m  ^
      ■* i m.i«t be regarded as  diffused over the entire body  area.  Hence the
the mi1*'1 muish      H 
94
 space form is not perceived in connection with the localization of space through
 the fibers or skin areas.  The true theory of perception  must be characteris-
 tically psychic, because no process can translate the  physical into the  psychic.
 Hence sensations both  simple and complex must be regarded as mental factors,
 The constructive process is therefore a psychic  one and depends upon mental
 evolution.  Whatever  qualities  are found to   inhere in  the  presentations of
 sense are associated with the object by a mental action bringing the object in-
 to relation with the mind through the  nervous system.   Hence  the objects of
 perception have space relations, these being the  mental stroma  into which the
 sensations are fitted as  these arise in experience.
     In connection with the theory of perception we  must recognize, that there
 takes place a synthetic  combination or association  of two or more  sensations
 differing in quality.  Hence in the existence  of the  different senses  we have
 the basis of those qualitatively different sensations which give us perception.
 When  a series of sensations  are found in connection  with the  mind arising
 from the stimulation of different parts of the sense organ   we have the spatial
 series.   Such arise  in  connection with vision and the muscular sensations,
 while others like the sensations of smell no not  give  rise to any  spatial idea.
 In the sense organs we find locally different parts  giving rise to  different psy-
 chic sensations, so  that the difference  in  location gives rise to a  difference in
 the mental representation.  Hence in the variation of the  part to  which stim-
 ulation is applied to  the  end organ  we have the basis of the local  calibre of
 the sensation, giving us a complex of  sensations, differing from one  another,
 the difference arising from the local signs of the organ.
     Perception is an educative process, not one that is native or instinctive
 In the construction of the field  of vision and of touch  we have the  education
 of the mind and the senses in  harmony with each other to  construct  such a
 united field.   In connection with the educative  process we find that  there is,
 first the tendency to localize at different points in  connection with  the body
 organ the production  of  the sensation and to render objective  the  sensations
 by giving to them an objective existence as related to the body.   In  the educa-
 tive perception process  the mind is constantly active, localizing certain sensa-
 tions as belonging to particular parts of the body, and projecting the body ex-
 ternal to  itself in the  localization of pure extra-bodily  objects.  The mind is
 thus active in  constructing or  synthetizing in  connection with the  sensations
 originating from  the stimulation of certain organs or parts  of organs, so that
 the physical basis of such psychic construction exists in the physiological stim-
 ulation.   Hence there must be in  perception a psychic as  distinguished from
 a purely physiological element.  It is not correct to speak of the purely neural
 and physical processes  as if these were the  exhaustive elements  of mind.   To
 say what mind is it is impossible; it  is better to recognize the psychic  reality
as shrouded  in mystery, because  here is the limitation  ^)f all  scienoe, even 
95
  exact physical sciences which cannot relieve themselves of the burden of the
  unknowable.
      The theories of perception have been classified as two-fold,the nativistic and
  the  empmstic. The differences arise in regard to the self-reality of the psychic
  the nativistic school emphasizing the primitive and intuitive mental chamois'
  tics,  while the empirical repudiates native intuition depending upon the exner-
  iential elements that are introduced into the mind through the stimulations of
  the neural mechanism in connection with the  external world  According to
  the genetic school  the space form  represents a native framework   into which
  experience is fitted, while the empirical  regards it as the  product of inter-re
  lations between the mind and the external world through  the nervous system
  In both theories we find an  element of truth.  Our sense perceptions  are noi
  simple native elements, but very complex products, implying not  only native
  capacity but the  experience involved in the   exercise of memory, association
  and judgment.  Yet the most simple sensations must be regarded as involving
  an intuitive capacity on the part of the mind  and its organ the nervous  system
  to be stimulated.   Hence the complex  perceptions must involve the  synthetic
  action of the  mind and the  action of the nervous  mechanism  as the basis of
  stimulation.
     We must first  of all find out the difference in the quality  of sensations
 which adapt them to become the basis of perceptions in connection with men-
  tal synthesis.   It is not sufficient   to say that sensations must originate from
 the  stimulation of contiguous  parts  of the  sense organ.   In the  case of the
 eyes, for example, there are double organs of vision, the retinal elements be-
 ing found  in the two eyes.   The  cerebral action  must take  place  in order to
 unite the elements of the picture so  that it is not necessary that the  different
 parts of the sense  organs  stimulated are  related to each  other  on a definite
 space basis.  In order that this unity may be  found in the  sense  perception it
 is necessary that the  elemental sensations  be capable of  combination into a
 series in the formation of complex sensations, in other words the single sensa'
 tions  must have  the characteristics of the  space series.  In  order to this  th
 sensations in the space series must  be similar in quality and must  be canabl
 of repetition in an order different from that found in any single series   In  th
 case of the eye and the skin  we find this capacity of variation with  rapidity
 and precision  such  as will give the spacial series, slight variations being possi-
 ble sufficient to give varying combinations of  the series of sensations.   In the
 case of the  muscular sensations  we find the same peripheral  mechanism capa-
 ble of  giving a  series of repeated sensations.   Taste and  smell do not give
 such a series of sensations that can be repeated.   In the case of hearing the
 ear does not  represent an organ whose surfaee can be  accommodated  to an
external stimulation and the normal aural sensations do not consist of a  series
that  shade  into each other, capable  of  repetition, so  that hearing  is not a 
96
geometrical sense.  In addition to this different series of space sensations must
be capable of  comparison with one another and  associated together.  Hence
in the  use of the  eye there are  simultaneous sensations  associated with the
muscles, skin,  etc., so  that the qualities possessed by  the one series of sensa-
tions may be compared   with those aroused by the other  series of sensations.
In eonnection with the tactile  sensations the contact of the body  with foreign
bodies at different points gives the idea of  contact, this idea of contact  giving
the spatial sensation.
     These sensations associated on the the basis of space relations are differ-
entiated by means of  symbolism.   When stimulation takes place at a particu-
ar part of the  organ  there is a similarity in the sensations arising from the
common local origin, this local origin  according to Lotze furnishing certain
local signs.  According to  this it seems necessary  that each minute area in
connection with the sense organs, like the eye or skin, possess peculiar shad-
ings in virtue of which,  when stimulated, certain graded sensations  arise.
Hence, the stimulation  of different elements in connection with the organs of
sense seems to produce  a grading of sensations depending  on quality relative-
ly to the point of the organ stimulated.  When such stimulation takes  place
it involves the simultaneous stimulation of  several parts,  resulting  in com-
plex sensations that differ according to  the number of  local points  stimulated.
According to Bain, all of  these local signs simply represent symbolic differ-
ences arising in connection with the muscular sense, simply symbolizing signs
of things.  This would  make them really lllusary.  In connection  with these
local shadings there are various forms of mixed sensations depending  on the
specific energy of  the nerve  elements aroused by active stimulation.  Hence,
the location of  a  visual image  depends on the retinal image and  also on the
impression  made  upon  the skin,  the head, etc.,  the image depending  on the
sensation in its complexity originating  from all of these combined.  Hence,
the local sign will  give  to the complex  sensation  its peculiar shading   and it
arises in connection with the complicated activites of various nerve  elements
stimulated  by different organs and at different  points.   This is  provided
for in the  almost  infinite variety of the nerve  elements  producing in con-
sciousness  an almost infinite  variety  of  shadings  of sensations.  In con-
nection with  our complex experience  we  find   Ihe complication of  the
processes  that  are  involved  both  sensational  and  perceptual.  In  the
transformation out of sensations  into perceptions  we have seen that  this is
done chiefly by localization and objectification,  the former being limited to the
body  according to  which  we get a knowledge of our own body  and the
latter giving  us  the knowledge of our  own  body in relation  to the  exter
nal objects.   Hence,   the  process  of perception  depends  on  very com-
plicated psychic processes, involving the combination  of a number of sensa-
tions on  the basis of  mental principles independent of the physical laws of 
objects  external to ourselves and even  laws of our own physiological  being
as  found in the organs  of sense.  Hence, perception is purely sabjective and
relates to the field of  existence that  subjectively  exist, not being concerned
with the material things and beings of the external world, ej.cjpt in so far  as
the sense data are furnished from an external world and brought td conscious-
ness in connection with the stimulation of the organs  of je.ise,  arousing the
activity of the nervous system.
    Our perceptive knowledge  arises in connection   with the special  senses
and to this  perceptive knowledge  we must turn.  (1) In  connection  with
smell there are no qualitative space  ideas.  Localization cannot  take place in
connection with the olfactory sensations alone, the localization of such sensa-
tions taking place in connection  with the tactile  and muscular  sensations.
(2) In connection  with taste  there is no localization  limited to taste  seusa-
tious, hence, they have no local qualities.  These taste sensations are so close-
ly allied to touch that the tactile sensations give localization to tastes.   (3)  In
regard to perceptions of hearing there is not a direct  localization of the acous-
tic sensations,  the localization   taking  place in  connection  with  the other
senses of vision and touch.   Acoustic sounds  that  originate in or  near the
ear are  transmitted by  the tympanum and the perceptions  are  formed by
means of judgment in connection with other sensations.  In some cases the
power to discriminate  between these  internal and other external sounds is
lost,  There are great differences among individuals   in the power to localize
sounds in relation to the body,  these differences depending  on the  sensitive-
ness of the external meatus  and the tympanum and the position  of the  semi-
circular canals.  The nervous connection of the ampulla possibly has  some-
thing to do  with localization  of sounds.  Ra^leigh  proved that if  a tuning
fork is sounded before or behind it could  not  be so  distinctly  localized as if
held to  the right or left.  Our'perception of  distance  in reference  to sounds
depends on the quantity and quality of the sonnds. Our perceptions of sound
then depend upon complicated processes associated with the sensations of vis-
ion and  touch as interpretations of the sound sensations.
     (4) In regard to the perceptions of touch there is a construction of a tac-
tile field  on the   basis of mental activity  in relation  to tactile  sensations.
Weber mapped out the body surface into localized areas by means of the del-
icate points of a compass.  He  took it that  the minimum distance at  which
two localized sensations  could be felt represented the standard of  sensitive-
ness in  connection with the different areas.   He estimates it  for the tip of the
tongue 1 mm, for the volar  side of the last finger phalanx 2. for the red part
of the lips 5, white of the lips 9,   back of the hand 31,  fore arm and fore leg
40  skin in the middle of the back 08.   These areas  represent sensation cir-
•1' or ellipses,  with a long axsis up and down.  Our knowledge of  the field
Vtouchdepends upon   these sensation ellipses.  By dividing the two com- 
98
pass, points less than is required to give* the minimum at a certain part of the
body and then gradually moving  the compass with the same separation to a
more sensitive part, the points of, the. compass will be felt to become separate
more than on  (a less sensitive part.  Hence,  it;is  inferred that  the mental
picture of the senstiveness is inversely  proportional to the size of  the sensa-
tion ellipses.  Different  individuals have  different degrees of  sensitiveness
and this may be cultivated by practice,  as in the case of blind  persons, who
have a very fine space perception by means  of touch.  The explanation of the
difference between the sensitiveness of one part of the skin-and  another part
depends upon the fact as Weber points out that each of these ellipses contains
a number of isolated nerve fibers, one at least being  sensitive and  several un-
excited.  It also  depends upon the fact already  referred  to that there is a
minimum of observable difference in regard to sensations, so that there must
be an observable  difference in the  coloring of  sensations.  The. differences
found,in the tactile perceptions depending on different parts of the body de-
pend on the nature of the skin, the nerve supply, the relation of the cuticle to
the underlying tissue or bone and the tension of  the skin,  as well as upon
habit in. cultivating fineness of perceptive appreciation.  Functional  activity
and mobility  are also said   t>  determine the  delicacy of  perception as in
the case of  the arm it said to increase from  the  shoulder towards  the finger
tips.  According to Goldscheiderithe delicacy of  discrimination in  connection
with the  skin depends on the pressure spots.   Hence, it is only  when two
such spots are excited  by the two  compass points that the two  points are lo-
calized, and the perception of  two such spots is^niore acute if the  two points
belong to different  chains of  pressure points.  In the use of the  compass a
number of   these pressure spots  are touched  arousing a number of complex
sensations, the  variation in perception  following the variation in the pressure
spots upon  the skin, depending upon the distribution of the nerve fibers.
    Associated with this perception of  space,in connection with the  skin is
the perception of  motion, depending on the-successive stimulation of a paFt of
the body so as to produce sufficient variation  in the local coloring of the sen-
sations, these sensations passing into each other.   Hence, the  perception of
motion is keener than that of simple space.   The sensibility to  motion differs
over the body surface and does not correspond  with  the sensation ellipses.
Hall says that when a m^tal point 12 mm. in diameter moves ov**r the skin at
a velocity  of 2 mm. per sec. in  order to  discrimination of direction   it must
move over  .2 mm. on the forehead, .44 on the forearm, and .85 on the back.
The motion can be reduced to such a slow  movement that no discrimination
of direction takes place.  This is in line with the theory of  localized signs so
that perception of motion depends on complex sensations differing in quality,
degree and rate of mobility.  Associated   with sensations  of  pressure and
motion we find the temperature sensations,  the cold and hot spots  forming 
99
  the basis of:tliis perception.  Both the cold and warm  sensations  are local
  J*ed aS p ints iQn;fihe surfaceof the ^   AU of ^^ gen             °^

  forming  of perceptions in the regard to the  position of the body.  In ^
  dmon of ;skin  insensibility it is  difficult, if not impossible,  if the  eyes Z
  closed  to locaUze theposition of the parts of the body.  In  Edition toth 2
  Male  sensations wemust take acconnt of articulation sensations in ^onnec
  tton witb jomte and tendons, the movements associated with these materially
  helping m localization of the body  in space relations.              materially
      The  muscular  sensations also represent an  important complex  of sensa
  tout ,n connection with peripheral body localization in contact with external
  objects.  Some  claim that such  purely  muscular  sensations do not   x
  V  undtcbuns that tW as  far as they differ from tactile  sensations are 8m
  ply<eerebral feelings; while others like Weber and  lLaddchum  there are Z
  cific-sensations dependent on neuro-muscular apparatr that determine! the TT'
  cepuons of body relations to a large extent.  The sensations arising fromThe
  muscular reuse depend upon the mass of  muscles called into  activity   Hence
  thesensations that depend upon the  skin  and the joints are  supplemented bv
  muscular  sensations, these depending upon the extent to which the muscles are
  moved ,n  exploring  the object.  In the case of  lifting a weight, if the eves
  are closed our knowledge  of the weight becomes.more  definite if it is  hf'ted
  quickly so that the muscles  become cognizant  of  the sensation  Direction
  seems to be determined also largely  by complex  sensation arising  in connec-
  tion with  the semi-circular canals, giving us a.perception of the body relations
  to space.  Tnere is a difference between,the sensations arising while the body
  is at rest and those  arising when the   body is moved as in the  movements of
  the head or  body  certain  changes are found in the  endolymph.  Iu this wa -
 the mind synthetizes  the qualitatively different  sensations in  the  construction
 of a field of  tactile perception.   In the normal individual the tactile and m
 cular sensations  give rise to a complex of perceptions that  enable us to local
 ize the body  in  its space relations,  but these are dependent to  a  large extent
 upon the leadership and discrimination of the sense of vision,  which witl
 cision and  rapidity moves  over the  entire field of sensation and   by deli >
 discrimination localizes the space relations of the body.
     5 The Visual Perceptions.  The eye represents the most complex or<rai
 associated  with perception.   It is naturally provided  with a very  delicate *'
 chanism for furnishing to the mind the data of sense presentation ^o that ve - '
 minute discrimination is possible both in relation to quantity and qnalfty   Th
 eye is endowed  with native  capacities at a very early period  of  life  and it
 psychic relations are  established  very early in life.   Many changes and var-
 iations take place in connection with the eye and these  variable "experience"
form the basis of a complexity of psychic interpretations.  There are also fi^
tile and muscular sensations  associated with the eye  movements that  give ns" 
100
to certain judgments which aid the vision.   If there is a local color tone arising
in connection with the retinal nerve elements, then there  must be local  signs
in connection  with the visual sensations at the  basis of the  visual  space per-
ceptions.   The question is raised, at what point in the  perception  process of
vision does the visual sensation posess extension  as distinguished  from inten-
sion.   In order to have the most primary visual perception there  must be sen-
sations of light and color; these must be different in quality and intensity, but
must  exist in consciousness  in  relation to one another  and at the  same  time;
these must be related  to each other on the  basis of local signs in  connection
with the retina and brought into relation with other sensations  arising  from
tactile and muscular senses.
    The increased complexity of the visual  perceptions depends  upon the fact
that the eyes are double, although the double organs represent but one  sense.
Although there are two sets  of retinal signs, retinal images and retinal motions,
yet they act together in such a way that the one is constantly  influencing the
other  whether normal  or abnormal.   Experience has involved  in such  com-
plexity the visual  perception that we must   analyze experience in  order  to at-
tain the elements out of which  to construct a theory.   We must follow nature
from  the most simple case to the more complex visual  experience.   According
to Wundt we have three stages leading up to a complex  visual  perception, (1)
while the eye is resting we have a retinal image involving complex  sensations •
(2) as one eye moves certain variations are found corresponding with this sin-
gle motion; (3)  when the two eyes unite in  common action there are still fur-
ther variations.  In connection with  these three stages we find  the three visual
fields the retinal, monocular  and binocular,  which give us the  perception based
(1) on the arrangement of the sensations of light and color arising  iu connec-
tion with  the retina and  its  nerve elements; (2)  on  the sensations  associated
with a single eye, and (3) on  the sensations associated with  two eyes.  The
retinal  and monocular visual  fields are imaginary and are of value  only as a
basis for analyzing  the sensations in the field of  binoncular  vision.   If both
eyes are covered and kept perfectly still, there will be perceived  an extensive
mass  of light and color sensations, depending upon feeling rather than  vision.
The points of distinct color may be localized but there  is no definite localiza-
tion, unless iu so far as  these depend upon past  experience.   By moving the
face upward the extent of the visual  sensations moves above us and  by moving
the face downward, the extent of the sensations passes down towards the feet.
This apparent depth  is due  to the variations in the color  tone  of the  minute
field elements.   Even  this  perception  depends on experience of tactile and
muscular sensations.   While the eyes are closed, if  pressure is made  upon the
eyeball, then there is a change iu  the  visual  field.  By  opening one eye then
the field of retinal vision passes into the field of vision  of the single eye.  If
strong pressure however is made upon the  closed eye so as  to produce  phos- 
101
phenes the field of monocular vision is absorbed in the retinal field.  The re-
tinal field depends upon the muscular sensations that arise in connection with
the accommodation and movement of the two eyes. In order to pereceive  posi-
tion and localized areas there must be even in  the retinal  visual  field  the re-
calling of former experience of muscular, tactile and  visual  sensations.   This
would seem to indicate that the  perceptive value  of the visual  sensations de-
pends upon   experience.  Hence in the child there is no knowledge  of space
qualities or relations intuitively.   As against the empiristic view it would  seem
that the retina possesses a native  perceptive capacity in regard to space; but
this depends upon the fact that when  each part of the nerve elements is irri-
tated  there is a  local sign in consciousness.   Added  to this is the fact  that
spatial judgment is limited by the definite limits of the retina.  This seems to
indicate that the perception of  space from the standpoint of vision is native to
the eye, as it represents the mental organ, the mind sjnthetizing the sensations
that are qualitatively different  as they originate  from the  stimulation of the
different retinal elements.
    The sensations aroused  by simultaneous irritation of the retinal  elements
assume spatial form  in the mental interpretation, at least in  the normal adults
the mind being natively active in the synthetizing process.   This  involves ex-
perience in the movement of the  eyes in the simplest case.   In order to  have
a clear vision of an object,   the image requires to  be fixed in connection with
the fovea centralis, the point of  the object that corresponds  with the image
point falling on  this central  point being called   the regard point, this point
being constantly changed in order to get a clear vision  of the object.  Iu or-
der to accomplish this the eye requires  to be rotated around a central point,
these rotations representing changing axes.  This center of rotation has been
fixed as 1.24 to 1.77  mm.  posterior to the middle of the optical  axes.   The
six eve muscles rotate the eye around three axes, the anteroposterior, the ver-
tical and the transverse.  If a line  is drawn from the  point of regard  to the
center of rotation it is called the line of regard, each  eye having  its own line
of regard, so that the plane of regard is represented by a line passing through
the two regard lines.  The primary position of the eye is found  in the  erect
position of  the head and the lines of regard  are horizontal.  In eye move-
ments without torsion there  is rotation of  the eye on the  vertical and trans-
    e axes   When the rotation on the antero-lateral axis is combined  with
vertical displacements,  the eye assumes an oblique  position and is in a con-
dition of torsion.  Helmholtz gives  the law regulating these torsion  move-
    ts  ''when the line of regard passes from its primary  position  intoany
         ;f,-™  Hie torsion of the eye. as measured by the angle of torsion, in
other position, me                                                     >
         i r^«ition is the same  as if the eye were turned about  a faxed axis
the second pobm""              v  ^.^     ^ ^ ^      ,           £
st a
of
ie second position is inc ^—  „u „ —....  ...._„      -----   .. „.wt aA1J,
   lin«- perpendicular  to both the first and the second  positions of  the line
      % ?'   The  details of  the  movements of the eye in vision  belong to
f regard.    Luc 
102
physical optics rather than physiological psychology.  It is of  importance  to
remember that in constructing the field of vision the eye wanders over the ob-
ject  surveyed,  the point of regard  representing  this  movement,  while the
mind interprets and synthetically constructs a visual field out of the different
sensations.   The field of vision in its general form and the relation of differ-
ent objects in it to one  another depend  upon and are determined  by the eye
movements.  Only objects seen by direct vision are seen in the actual position
they occupy, the objects of indirect vision are seen at the place in which they
would be found by transferring the retinal images  corresponding with the ob-
jects to the point of  regard.   Hence,  the retinal  image lines   do not  corre-
spond to the objective lines,but are constructed  by the eye in connection with
a number of sensations  that have  local  signs and  in  connection with certain
muscular sensations aroused by  the different eye  movements.   The  muscular
sensations that originate from the movements of the eye in accommodation  to
distance when harmonized with tactile sensations form an important element in
visual perception.  In connection with binocular vision  we must take account
of the fact that we have two retinal images in relation to one  another and de-
termined  by the  eye movements.  Normally the two  eyes are in  activity so
that  two images are prseeut; while each eye is an  independent  instrument iu
combined action they  represent a unity.   Hence the two eves  move and act as
a unit.  If  we found iu the two  eyes  perfect symmetry then  the  elements
might be regarded as two perfectly similar retinas upon which  identical im-
ages could be  formed.  Perfect symmetry however  is not found, and other
points than those called primary are brought into common action, these points
being called  corresponding  rather thau  identical  points on the two  retinas.
These corresponding points upon which the two images of a  point in  an object
fall,  act together iu the visual perception,  so that  each separate  image covers
the other image.  In some cases points that do  not correspond act  together,
these points covering each other, so that  here substitution takes place  among
the different points of the two retinas.  If the  regard  lines are  parallel in the
horizontal meridian plane of the  retinas, there is no correspondence iu the ver-
tical meridians.  This produces nnsymmetry in the eyes.  When an object is
imaged upon corresponding points of the two retinas,  the object is  seen as a
single object, although double  in the retinas.  By  fixing the eyes on a  distant
object and  pointing the finger at  the same object, there will  be noticed two
pictures very transparent of the finger,  indicating the double vision of a sin-
gle object.   If the eyes become changed from their primary position,  there is a
change in the two images.  By converging  the eyes on an object, the  images
cast on the central parts of the retinas exactly correspond, so   that the  vision
of the object is single.  But the points that lie close to these central  spots are
also seen to be single, because they represent corresponding points which have
been  accustomed to  act together in  binocular vision.   All other points  away 
103
from this point of visual fixation however  give double  vision of  objects, be-
cause they  do not fall upon corresponding retinal points.  The sum of all the
[joiuts seen single by the two retinas while the fixation point remains the same
represents the horopter.  Much  speculative  discussion has taken place in re-
gard to what it is but it cannot  be determined, because it is a psychic matter
and depends on  experience, so  that it cannot be reduced to  mathematical or
physical precision.  When the  eyes are fixed in  the primary position, the
horopter is found in a plane  perpendicular to the  median line of  vision.  In
the case of all points nearer iu the primary plane it  is found in a line that in-
clines towards the person observing, the inclination being towards the plane of
vision.  If the visual plane is turned upward  or downward,  the inclination of
the horopter increases or decreases.   In the act of fixing the  point of  regard
in binocular vision of a near object, the visual lines must  converge on  the ob-
ject, the eves rotating in this  convergence on  the axis in opposite directions.
In looking  on  distant objects the visual plane is  raised, the lines  of regard
diverging to the  parallel position.  The convergence is symmetrical where the
two lines of regard  turn in at equal angles,  the point of  regard being fixed in
the median visual plane; it is not symmetrical where  the point   of regard lies
outside the median  plane, the eyes  being turned inward at unequal angles, or
the one in  and the  other out at an acute angle.   Accompanying these varia-
tions are variations iu accommodation,  these changes  furnishing complex sen-
satioiis of great importance in the space perceptions.  In connection with con-
vergence attention  is necessary.  If the attention is  arrested  the two eyes are
combined as a single optical apparatus, the sensations aioused by the  nervous
stimulation of the muscles in connection with convergence  forming the basis of
feelings of innervation which are cerebrally associated  with the initiation  of
motor impulses originated in the central system.  Some claim that there is an
equality in the innervation of the two eyes even when  the eye  movements are
unequal.   Even  so the  psychic  representation  of the different movements has
an important bearing on perception.
     In these ways the eyes are capable of stereoscopic vision, that is  of com-
bining the rays of light  that furnish  two pictures iu  such a way as  to foim  a
single"image.   If the two eyes were  not active such a  result would  not be pos-
sible  From this standpoint binocular vision  is the  only normal  vision and
monocular vision mav be taken to represent simply a plane of vision,  without
any perception or at least direct perception of depth.   In the normal  condition
of the eye it is true in the adult by a single  eye such  stereoscopic vision  takes
nlace but-this depends upon experience, and in addition to experience  certain
            „a  vn,-h as vacations in intensity of light,  for the purpose of es-
means are useu, nu*-'" "k
  , .■ v.-   ^lotions to form the  basis of complex sensations.   From this staud-
tablishmg reiauou^ i"                             ...
            liditv of  objects  is perceived and appreciated in connection  with
P°U)    e  *.  f,qf.h eve having its own vision of the object, the right  eve  look-
tile two e.y 
101
ing at it more towards the light and the left eye  towards the left  side.   Hence
a series of partial images are perceived  and  in the fusion of  these lies  the pos-
sibility of the  perception of solidity  in an object.  By the movement  of the
eyes there is a uniting and  separating of a series of double images which en-
ables us to localize objects.  Eye movements are not necessary for  the adult
eyes in connection with stereoscopic vision.  This is proved by the fact that a
visual field can  be constructed by the  illumination of  an electric spark which
does not  permit of any movements in the eyes in connection with convergence.
But this depends upon  past experience  associated with the  movements of the
eyes.  In connection with visual perception of the distance of objects and the
solidity of  objects,  it is necessary to have  two eyes in motion.  In order  to
have such a perception Hering claims  that, "all the lines or  points whose im-
ages lie, with a given position of the point of regard, in the vertical horopter,
appear clearly defined on a surface which is either plane or slightly cylindrical;
and all the lines or  points lying this side of the vertical horopter and  whose
images have a crossed disparateness appear in front of this surfaee ; while those
lying beyond the horopter and whose images have an uncrossed  disparateness
appear behind  the surface on which  whatever lies in  the  horopter is seen."
This  law implies that to  interpret the images in connection  with  the eyes
when at rest  in the perception  of distance and solidity  there is  a past experi-
ence of local  signs in connection  with the eyes  iu motion and  accompanying
tactile and muscular  sensations.   According to the  older  psychology the per-
ception  of distance and solidity  depended upon muscular and  tactile sensa-
tions of the body in conjunction with visual sensations, the former  being nec-
essary to such a perception.  Newer psychology  has demonstrated the possi-
bility of perceiving distance and solidity  by sight, in  connection  with the two
eyes in movement.
     In addition to the primary visual  perception, the vision of distant objects
depends  upon stcondaiy aids in  the ooustiuctk.n of the visual field.  Such sec-
ondary vision is distinguished  from primary  vision by the added  element of
discrimination,  although  even  in the  immediate, primary  percepiual  vision
there is also the element of  judgment.  The main distinction is found in the
fact that  in  addition to  what  is associated  with  normal  binocular vision,
there is a judgment of space relations  depending on the variations of position
in more distant  objects.  The muscular sensations do  not  furnish sufficient
variation if the objects of vision are over 30 or 40 feet  distant from the eyes.
Hence  the necessity of subsidiary aids in connection with  stereoscopic vision.
When the eye  is in motion  it sweeps over an object in different directions con-
structing  certain  lines of limitation in  regard to the  object,  and these lines
determine  our  perception  of distance  and  solidity.   When these  lines run
counter to previous experience there is confusion in our perception, especially
if the lower lines of limitation are obscured.  These limiting lines  determine 
10o
  the contour of an  object and from this standpoint  form an  element in per
  ception.   In addition to this the mathematical  angle of vision  in connection
  with an object aids in its perception.  This angle gives us the relative distance
  from the eye and  also the  size of the object.  If the objects  are quite remote
  from the eyes, then the light reflected from them  requires to pass  through an
  extended atmosphere, varying the contour of the objects and the color  shad
  ing; with the result that if the air is clear the objects appear nearer, if dim and
  hazy more  distant.   When  the shadows are  increased, as  in the  case of a
  morning or evening light, objects appear to be more remote  from  virion the
  distance being increased.   Hence  the relation of  shadows of objects to'one
  another gives an  important aid to visual  perception.  In the movements of the
  eye  there are called  forth certain series  of sensations  that differ   from  each
  other,  the number of these and their intensity  furnishing a means of  determin-
 ing the size and  form of objects.  As the sensation  series increases our per-
 ception of the object  gives  us an increase in its size ; with  tue increasing in-
 tensity of the sensations there is an increase apparently in the size of the object,
 as is seen when  an object is looked  at with tired  eyes;  as the  length of  time
 occupied in the perception increases there is also an increase in  the size of the
 object.  In  adult vision  memory furnishes  important data,  because when the
 eye furnishes an  indistinct outline  of an object  memory—pictures fill up the
 lacunae.   In addition  to this the eye sees very much the  object it is  looking
 for.  Attentim to an  object makes the object   clearer in   vision, so that by an
 effort  of will the  sweep  of the  eye can be determined  and consequently by
 cnoice  the mind interprets the data furnished in the visual sensations.  Hence
 experience plays a very important part in perception.   Psychic laws  govern
 our perception of  visual magnitude, so that our knowledge of visual  lines   and
 objects is relative, variations depending on the  different  positions  of the eyes
 as well as of the objects.
     Ocular  discrimination  is more  delicate  in the case of  horizontal than
 vertical distances, and  is more accurate if  the distances compared  lie in  the
 same direction.   Hence, in deciding  distances,  the local retinal signs in con-
 junction with memory pictures and variations in muscular  sensations depend-
 ing on accommodation movements are most important.   The apparent size of
 an object  is judged from the visual angle of  the image and the surface stimu-
 lated  by the  rays of light  in connection with   the reflection upon  the retina.
 The real size is definitely determined  by the standards fixed by the mind in
 connection with visual and  tactile sensations.   In connection with these there
 is the determination of the  distance of the object from the eye.  the  distance
 being determined  in interpreting the  real size from the apparent size.  Hence
apparent and real size with the distance of  the object from the eye  form the
three necessary elements in the visual perception of an object.
    These form the basis of our perceptions of motion in relation to its  di- 
106
rection and velocity.  There are  certain  perceptions  that are primary,  the
elements of which  cannot be consciously  distinguished,  whereas other per-
ceptions are secondary,  according to which there is consciousness of  the ele-
ments of perception,  the perception itself being inferential lrom movements
of a body or object.   In the judgment of motions of  an object,  some point is
fixed, variations by movement from which, form the basis of our perception
of motion. Perception of movement in objects may arise in one of two ways,
(1) there may be a change in the  object's position in the visual field,  adjoin-
ing retinal areas being stimulated in succession so that all the images formed
are alike; (2) the same retinal areas may be successively excited,  resulting in
the production of different images.  In all perception  of movement the eyes
follow the body in motion; if the eyes  move so that the point of  regard con-
tinues fixed on the object, our perception  of motion  depends on the muscular
sensations of the eye  movements;  if there is a movement of the head or neck
or both,   there is added the muscular sensations  arising from head   or neck
movements.  The perception of   bodies in motion implies the  perception of
bodies  at rest and the  complex  sensations involved  in eye  movements.
These complex sensations involve the construction of  images,  these images
remaining as after images in the mind.  In all of  these perceptions  there is
more or less of discrimination  and judgment and hence   liability to  error.
In distinct vision we must always have  psychic interpretation  of complex sen-
sations, hence, the presentations of sense are not exact copies of  external ob-
jects of  sense.  These errors of visual   perception  may arise from  mistaken
perception of the relation of the double images, depending on  whether the two
retinal images correspond or not; from the mistaken or obscure perception of
lines, surfaces and  angles in connection with the  object;  from the mistaken
perception of  the different elements found  in the visual field;  from the liabil-
ity to synthetize the different sensations in a manner already familiar in con-
nection  with memory  images,  habit or imagination.   These  may arise from
confusion in regard to physiological conditions or psychological principles in
connection with the activity of  the brain centers.  Hence,  psychologically
complicated processes are involved that are not as yet understood.
    Visual space involves the  existence of complex sensations of  light and
color,arranged and synthetized by the mind.   This arrangement and  synthe-
sis involve the inherent activity of the  mind in conjunction with  the activity
of the body organism. It also implies psychic  development  especially  in
connection with experience.   Visual perception  is developed  in connection
with the synthetization of sensations which are aroused in relation to the ac-
tivity of the organs of vision.   The visual  field is purely subjective  and per-
ception  depends on the formation of the retinal image, the formation  of the
retinal image depending  on the reflection of   the  light ra> s from an  object.
Hence,  we have the connection established between the mind and the object 
107
the spatial form of  all perception  being  purely psychic,  so that the visual
field is subjective.
    The Time Element in  Sensation and  Perception.  The  sensations
not only have their special relations but also a time element or form.   It is
not possible either physiologically  or psychologically to explain time because
even when the order and relations  in time of the sensations have been grasped
we are unable to interpret the meaning of  these relations.   Hence,  in explain-
ing the order of succession we simply take for granted the idea of  succession.
Many experiments have been made in this field of psychometrical calculations
in connection with delicate  instruments to find out the periods of time necessa-
ry for nervous and mental processes.   ~No general principles can be laid down
aside from the fact  that time is essential to all the processes of mind and body
and that the amount of time required is determined by the complexity of the
object, the nature of the sensation  and the condition  of the bodily and mental
mechanism.  The experiments all aim to establish the same point,  namely,
the amount of  time occupied  from the period of  stimulation in  connection
with an end organ of sense to a consequent movement.   The  electrical cur-
rent is used to determine the exact periods when the  stimulation and  motion
take place.  Hence, in the case of a spark of electric light  or the sounding of
a bell we have the stimulation, and in the giving of a signal,  the motion of a
finger or foot  or the utterance of  a vocal sound we  may have the resulting
movement.  By the repetition of these experiments in connection  with the
same or different persons a great variety of conditions and  circumstances may
be found modifying the results. The value of these  experiments, dissociated
from particular  circumstances rests in the indications given of the complex
psychic and psycho-physical processes involved. The  starting point in all such
experiments  is the determination  of  the reaction  time,  which  includes the
period elapsing between the  stimulation and the resulting  movement.  This
reaction time is found to be simple in the case of a single sensation resulting
in a single movement.   Even here, however,  the period of  reaction is com-
plicated by the stimulation of  the peripheral organ,   the nerve conductivity,
the spinal conductivity, co-ordination in the lower part of the brain, transfer-
ence from sensory to motor, efferent conduction and  liberation of the efferent
impulse in motivity.  In connection with psycl oh-gy  the most important of
these change* is the transformation from the  sensory to the motor  process in
the cerebrum, the time occupied in this process being  psycho-physical.   Ac-
cording to Wundt it consists of three elements, (1) its passage  into the  con-
scious field resulting in perception;  (2)  its passage  into the attentive  field,
resulting in apperception; (3) the stimulation of the will which gives rise to
    i   , ,.,- imimlse in the  cerebral organ that produces movement.   Time is
avolum iiy mipuist- m              o
     . rv  for each of  these factors; and  in the time relations  we  find both
"h *■'Tolo«dcal  and psychic  elements or processes,  so that the  physiological 
108
question according to Wundt is to differentiate the perception,  apperception
and will time-periods and the  corresponding  physiological and psychic pro-
cesses involved.
    Preliminary to the determination of the psychic periods and fundamental
to their existence is the activity of the nervous system. In  the nervous system
we find different elements, hence, time is necessary  not only for  the stimula-
tion but also  for  the production of definite effects in connection with the stimu-
lation.  In regard to latency we do not find the necessity for the  ssmereriod
as in the case of the muscles, but in the  case of the neuro-muscular  terminal
organs certain definite stimuli are required and also definite time relations in
these stiuuli iu  order to produce the desired effect,  the terminal organs differ-
ing on the basis of the  special senses.   If these time relations  are not of a
particular kind there is a fusion of the closely related and successive stimuli.
Experiments  have been  made for the different senses to determine  the mini-
mum interval of  time.  For the visual  sensations it is found  that the inter-
val is greater.  It is found that the light sensations are capable of being sep-
arated as stimuli at an  interval of .025  of a second.  In the case of  a stimu-
lus falling on the fovea centralis  and another on a retinal point  6 mm. dis-
tant the minimum  interval is  about .075 of   a second.   In connection with
color perception it is found that very  slight variations exist in regard to the
minimum interval of time.  The recent  researches  indicate that the time re-
quired for color to act on the retina in order  to produce a visual sensation is
increased in arithmetical proportion as the light intensity diminishes in  geo-
metrical proportion.  In the tactile  sensations it is found  that the minimum
interval between  two or  more sensations differs considerably  under different
conditions from 500 to 700 being  distinguishable as appreciable stimulations
per second.  In the case of  auditory sensations it is found  that the number
of sounds discern able in a second is about 500, these sensations being capa-
ble of separation.  The period necessary  to distinguish different  successive
stimulations in the case of the different  senses is very difficult to determine.
Much depends on the intensity of the sensations themselves and on the senses
that are discriminated.   In the comparison of sight and tactile sensations the
minimum interval between two sensations is placed at .05 of a  second;  iu the
case of sensations of sight and audition  .06 of  a second,   and sensations  of
sight and tactile impressions when the sensation of  sight precedes .16.   The
firit determination is the reaction time but  this is subject to variation  in dif-
ferent individuals and even in the case of the same individual.  In connection
with experiments the  period occupied  by the cerebral process  is brought  as
close as possible to zero and in this  way the purely mechanical action of the
processes is determined.  In connection  with  various experiments  it is found
that the  reaction  time varies  from about 1-10 to 2-10   of a second.  If the
stimulus is increased then the rea tion time is diminished  within certain  lim- 
109
its.  The same thing is true if, preceding the stimulation there is expectancy
of the stimulus, on account of the fact that the cerebral centers are aroused to
sensitiveness awaiting the stimulation, so  that very prompt action takes place
in connection with the response.  If, on the other hand, the attention is over-
strained, there is an excessive amount of  stimulation sufficient to counteract
the effect of expectancy.   If the nature of the  impression expected is known
but its intensity is not known there is a tendency to increase the period of re-
action.   The same thing is true if the psychic condition of inattention exists,
because time is required to concentrate   attention and this increases the re-
action period.
    Many attempts have been made experimentally to find out the rapidity of
the psychic processes in connection with  perception.  It is necessary  to de-
termine the reaction time in the case of apperception and then deduct from
this the simple reaction time.  If an image of a special color is  permitted to
fall on the retina and then the image of a bright object is permitted  to fall on
the retina after a brief period,  if the period intervening  is too short then the
first perception is lost in the  second an'*  no comparison takes  place to form
apperception.  Hence  the apperception  time depends   on the complicated or
simple character  of the actions involved.   This does not enable us to deter-
mine the time of apperception because no  account  is taken of the  time occu-
pied during the process of nerve conduction.
    Other experimenters have been tried to find out the time occupied between
the stimulation and the consciousness of the result of the stimulation in con-
nection with a definite action or  the determination not to act.   These  inves-
tigators took it for granted that the will time was not involved,but that by find-
ing out the entire  reaction  time  and deducting  from it the  simple reaction
time, the balance represented the apperception time.   Hence,  in connection
with the apperception of sound it was found that .015 to .070 of a second was
necessary.  It must be  remembered, however,  that we are simply finding out
or trying to find  out the time necessary   to enable us to connect  a sensation
with a definite movement on the basis of habit.  On this basis the psychic pro-
cess becomes simply apperception with the discriminative process eliminated.
This eliminates the  will time altogether and to reach a  decision in regard to
reaction there is necessary the exercise of volition.  Hence, another method
is suggested by Friedrich.   Preintimation  is given of stimulation in connec-
tion with a number of colors without the definite  knowledge of what color is
to be expected.  In this case the determination  of the color is a matter  for in-
dividual judgment and the individual  is  required  to signal  the  moment of
     ception.  When the  complete reaction time is obtained   the simple re-
   t' u time  is deducted  and the balance  is said to represent  apperception
t•   ,   A mean apperception time is deduced from a number of  experiments
•^connection with  different colors   varying from .047 to .086 of  a second. 
110
Thus we find that the apperception time varies with the conditions involved
in the simple or complex circumstances the variation of  time being from .03
to .OS of a second.  In order to distinguish the intensity associated with dif-
ferent sensations a longer process is necessary.  If,  for example, reaction is
required in the case of the more powerful of two tactile sensations, time  is re-
quired to discriminate intensity and time to determine  the reaction.   In con-
nection with the finding out of apperception time we must consider  whether
the element of expectancy  is associated  with the action and to what extent
this expectancy exists, for if the attention is divided  between the expectation
of a particular sensation and the readiness to  reach them there is a difference
in the time involved.  In the case of several  objects there is also necessary a
longer time than  in the case of a single  object.  This depends  on habits in
association and comparison of a number of objects.
    According to Donders the time occupied  by the  will in  connection   with
the solution of a complicated problem is shorter than  that  involved in the ap-
perception period.  Having determined the simple reaction time Merkel inquires,
what  length of time is necessary to liberate a voluntary impulse.   According
to him following apperception there is a will period whether longer or  shorter.
First  of all  the simple  reaction time is determined;  secondly  the time  re
quired to compare two impressions and give the result of the comparison is found;
and lastly there is a determination of the time of reaction in the case of the ex-
ercise of will involving choice in regard to reaction and the nature of the reac-
tion.  From these experiments it was found in the case of teu persons that the re-
action time in the case of choice of two alternative courses was.024 to .015 of a sec-
ond.  By the increase of the alternative courses there is an  increase of the time
of reaction.  It is found that there is an increase depending  upon the individual
characteristics, these increasing as the choice is increased to five and decreased
from fiye to ten.
    We are not able on the basis of existing experimental knowledge to speak
of the psycho-physiological time with any degree of defiuiteuess or to analyze
its elements.  According to Wundt there is an appreciable  period  occupied in
apperception and willing; but according to recent experiments  it seems  possi-
ble so to arrange conditions as to make the entire peiiod including appercep-
tion and  will time very little if any longer than the simple reaction time.  This
means that habit or practice can appreciably  lessen  the psycho-physiological
time,  as we become able to  perform the  most complicated  and discriminating
movements without almost any cerebral  deliberation.  According to  Donders
apperception time is almost equal to will-time,  the former being represented by
.039 and the  latter .036 of a  second.   This indicates  that the discriminative
and voluntary actions occupy about the same periods of time, but in  cases of
the succession of discriminative and  voluntary actions the former  are capable
of very great acceleration over the latter.  Attempts have been made to compare 
Ill
our subjective idea of  time formed from the succession of subjective processes
with the objective time standards.   It has been found that the  mind is able to
appreciate in connection with a number of reactions intervals as small as one
hundredth part  of a second.  The rapidity with which the impressions  pass
into consciousness, however, does  not exactly correspond  with  the  rate of ex-
ternal stimulation.  In  connection with sound for example,Wundt has proved,
that in hearing a sound it is almost always heard  either before or  after the
physical sound takes place.  If there is a condition of  mental  expectancy the
sound seems to be heard before it  occurs.   This is called the positive and neg-
ative lengthening or displacement.  Great variation is  found in the  discrimi-
nation of  minute  intervals depending on  the length  of the intervals.  It is
found for example that minute differences are appreciated most accurately at
intervals of  seven or eight tenths of a second.   The sensitiveness is diminish-
ed as the intervals  become longer or  shorter, so that at longer intervals the
period is considered as  too short and at shorter intervals  as too long.   In  the
case of longer periods  no definite principle can be laid down as individual  pe-
culiarities seem to form the necessary coudition of such  variations.   The most
accurate way of considering these  variations is in connection with sensations in
succession whose intervals are definite and can be  definitely determined in con-
nection with the chronoscope so as to be accurately  counted.   It is found that
2 clicks can  be appreciated if the interval  is .0523 of a  second, while 3 or 4
can be appreciated if the interval is  .0K!»5.   This  seems  to indicate that when
the period between the  sensations falls below the  briefest period  of reaction,
some of the  sensations will not enter consciousness.
    In connection with the more complicated mental  actions involving the  as-
sociation of ideas and memory in reproducing mental pictures it is found that
these processes form the fundamental basis of all such discrimination as is  in-
volved in apperception.   Time to necessary for the process of association, the
association  depending upon  habitual connection or else natural  association of
objects on the basis of internal relations of  quality or property.   In the ap-
prehension of single words it is found that the reaction time varies from .05 to
.17 of a second.   The   association time varies  according to the nature of the
association involved, the order in which the  ideas are presented and the amount
of mental action preceding the association.  Very  great  differences are found
in different  individuals these  depending on the time that  is required  for  the
exercise of memory, for completing the chain  of  association, etc    In regard
to the number of impressions that may  be found in the conscious  field of per-
ception at the same time, some  claim that  only a single object can be before
the mind at any moment of time, while others regard it as certain on account of
the re'ativity  of knowledge that at least  two impressions  must be  in con-
        -,-, ,-r, rtrder to the possession of  such a  knowledge.   Experiments have
 '•lousncjss in oiuci  <      i
         de  to  determine how many successive impressions of  sound may be
S(
been 
112
formed into a single picture so as to form  a distinct series.  It is found that
all states of consciousness are relative and that the elements in these states are
relative, so that a close  and  inseparable relation exists among the  different
elements.   It is possible thus to name isolated letters or words  if a number of
letters or  words occupy the   field of consciousness  at the   same time.   It has
been supposed that the unity  of the mind precludes it from having  before it as
the same time more than a single object.  Experience however proves that the
mind can perceive  a number of objects and even give attention to those objects
at the  same time.  Different  persons  are capable   of attending to a varying
number of objects, the most favorable   circumstances permitting of  attention
to about 10 or 15 impressions in the  one conscious field.
     In  connection  with all  these experiments in regard to time relations ex-
ercise  increases the capacity  and exhaustion diminishes the capacity  of the
mind rapidly to perceive and will.   It has been found that exercise lessens the
will time in the choice between two alternative motions  one third.   In the ap-
perception time it is found  that exercise diminishes the time  even  after the
simple reaction time has entirely ceased.  If the nervous system is  exhausted
the reaction time is increased.  In the case of insanity and  kindred conditions
there is involved an increase  in the  reaction time   Alcohol is found  to pro-
duce variations  in the reaction time but these are not  constant.  The  use of
coffee is found generally to decrease  the reaction time, indicating the beneficial
effect it has upon the strengthening and intensifying of the  psychic processes.
The results we have observed indicate that physiology and psychology  are not
aole to  explain our time relations.  It is possible to  describe the order of our
ideas and their relations  from the standpoint  of time but it is impossible to
explain what is meant by succession such  as is found at  the  basis of time.
Time is necessary for any and every sensation, for  every act of  will,  so that
in sensation and resulting motion we have a  definite succession.   Succession
it is said is based upon association but how to classify the  associations is still
a problem unsettled psychologically.
    The Lower and  Htgher  Psychic Functions.   Here we  are  passing
from the purely experimental stage of  psychology into the more  dogmatic
field.  In regard to the physical foundation of the  higher  psychic  functions
and the mental development  opinion seems to be the principal   guide.   In re-
gard to the psychology of feelings very little of a definite character is at pres-
ent known because the phenomena of feeling are very  changeable, depending
on such variable changes in connection  with the central  nervous mechanism.
The attempt to investigate feelings from the standpoint of  self-consciousness
and the attempt to  condition the feelings by  physiological processes  do not
yield any satisfactory results.   Many very different  opinions have been form-
ulated in regard to the nature of feeling.  The word feeling has been used in
a very indifferent sense.   In some cases  it is used in  the general sense of feel- 
113
 ing as localized iu connection with the skin, in  regard to contact, pressure or
 temperature; at other times it is applied to complicated sensations,  involving
 pleasure and  pain, religious emotions ' and even moral duty.  The  theories
 formulated in regard to feelings may be classified as threefold, one  laying the
 principal stress upon the original and primary nature of feeling, on account of
 which feeling is not definable, the attempt to define feeling resulting in idealiz-
 ing it; the other theories regard feelings as derivative in  character,  the deri-
 vation being either purely psychic or purely physiological.  These latter theo-
 ries only differ in the point of view from which the derivative character of feel-
 ings is looked at, both of them being essentially ideal.  From  the physiologi-
 cal standpoint feeling is  regarded as the consciousness  of certain  conditions
 associated with the nervous mechanism.  In the activity of the different nerve
 elements we undoubtedly find the physical  basis of  many of  the pleasurable
 and painful feelings, but this does not imply that all of the feelings  can be re-
 duced to physiological  conditions.  Lotze  first attempted to distinguish feel-
 ings on  the basis of psychic conditions  involving pleasure or pain from those
 complex sensations which arise iu connection with the indifferent elements of
 perception.   The basis of pleasurable feeling is  the agreement and  of painful
 feeling the disagreement between  the results of the stimulus and some condi-
 tions associated with the  expression of physical or psychic  life.  According to
 him feeling  represents "the  measure of the  partial and  momentary  concord
 between the effect of the stimulus and the conditions of vital activity."   This
 principle however cannot be  applied in explanation of feelings  because they
 cannot be explained  as derived forms of consciousness.
     In the case of  any form  of stimulation  where the stimulus is excessive
 there  results  a painful  feeling.   Tnis excessive stimulation  involves  some
 thing that is  in opposition  to the vital  processes.  This does not  mean that
 the  amount of danger to the organism can be measured by the  degree  of pain-
 ful feeling.   In  the case of  some persons any intensification  of the smell
 taste or  auditory  sensations results in a disagreeable feeling.  In the  case of
 the  higher class of disagreeable sensations  associated with intellectual,  moral
 or aesthetical feelings we cannot analyze these sensations into the  consciousness
 of nervous stimulation in excess of what is advantageous  to the vital activity.
 In some   cases where  this kind of  stimulation is  excessive it is pleasurable
 rather than  painful, this  being determined from a purely subjective standpoint
 by habit, association or will.   In connection with sensation we  are able  to de-
 termine  the relation  of pleasure or pain to  the degree of nerve  stimulation.
 If the sensations are not  excessive they are usually agreeable; after  the sen-
 sations become painful on  account of excessive  stimulation we   find the dis-
 agreeable feeling.  The  degree  of disagreeable  feeling does not correspond
 with the degree of sensation ; on this principle Wundt claims that a feeling be-
comes pleasurable to the  maximum degree as the sensation ceases to  increase 
lit
in proportion to the increase of stimulation.   If painful feeling  depends  on
the consciousness of overstimulation of the nervous system, then  there can be
no painful feeling independent of the intensity of stimulation.  This cannot
be the case because to some persons all degrees of  stimulation involve painful
feelings.  According to Bain  pleasurable states  depend on  an increase and
painful states on a  decrease of the vital processes.  According to Allen this
theory  should  be modified to the  extent  that pleasure is  associated  with  the
healthy vitality of the body or of  its organs supplied by sensory  nerves, pro-
vided the functional activity is limited to the  recuperative capacity of the sys-
tem and  its  organs.  Here pleasure will depend   on  the normal  activity,  not
necessarily   simply vital, found in connection with the end organs of sense.
Here  there  is a limit, because  we cannot say that  the slightest  disagreeable
feeling involves an  intensitv  that is beyond the  ordinary powers   of repair.
Pain in a large  number of cases is the signal  of excessive stimulation  but this
does not cover all cases;  for we are unable definitely to determine what amount
of stimulation is necessary for and compatible with normal  function.
    Distinguished from  and iu opposition to  the physiological school we find
the school of psychic feelings.   Nahlowsky  distinguished between feeling
and sensation.   When sensations  are pleasant  or disagreeable  they do not
constitute or give us feelings but depend  upon the effect  of the  stimulation
upon  the vital organic functions.   Pain represents a sensation, not a feeling.
Feelings represent  those conditions  that arise from  the simultaneous exist-
ence of  certain ideas in the mind;  if these   ideas harmonize,  the feeling is
agreeable; if  they do not harmonize the feeling is disagreable.   Thus  feeiings
are derivative,  depending on ideas, feeling being the direct  consciousness of
the raising or depressing of individual psychic action among the mental ideas.-
Hence sympathy and love are feelings as distinguished from the purely physi-
ological sensations  of fatigue,  hunger, thirst.   In  this sense we find  the Her-
bartian idea  of  feeling that of the  "immediate consciousness  of the rising
and falling of one's power of ideating."  It is thus derivative, depending on
the reciprocal relation of ideas;  as distinguished   from the  consciousness of
separate ideas,  it involves the correlation of ideas to  the extent of furthering
ideation in case the feeling is  pleasant and hindering ideation if it is  disagree-
able.   This theory  falls short of explaining agreeable and disagreeable sensa-
tions, and for this reason is unsatisfactory.  In addition to this, feeling cannot
be regarded as  a derived activity.  In the most primitive  forms  of  child life
feeling seems to be  inseparably associated with the organism.  Some feelings,
such as desire  and the self-feeling  are coeval with  self-consciousness.  The
two theories  therefore that we have considered, the one physiological and the
other psychic, represent  the two conditions, physiological and psychic, under
which feelings exist,  but they do not, even  when combined into one theory
give us a satisfactory explanation of feeling. 
115
    As distinguished from  these theories,  the true theory is  that feeling is
primary and not derivative,   representing  a eonscious activity of  the mind.
It is not capable of definition, because knowledge of feeling can be gained only
from feeling itself,  and as feeling is associated with all psychic activitj^,  both
from the standpoint of sensation  and perception, it is  complicated by its asso-
ciation with the psychic processes.  Undoubtedly many of the feelings depend
on the stimulation ol  the nerve  elements.  We find special nerve  elements
that need to be stimulated to produoe pain  and the difference in  the  painful
feelings depends on the  difference in the  stimulation.  What produces the
difference in the tone of the feeling in pleasure or pain we  are unable  to de-
termine definitely.   As we have  seen  there is not considered  to be a special
pain mechanism, the same mechanism that gives us the pressure  and temper-
ature  sensations,  under excessive   stimulation,  giving painful  sensations.
But recent  researches  seem  to indicate that as   pressure and  temperature are
quite distinct in the terminal organs, and as in some cases tactile sensation is
not lost when  the pain sensations are lost, there is a physiological distinction
between the ordinary sensations and the sensations of pain.   This seems to be
closely related to the fact that feeling is primary rather  than secondary.   It
is very difficult, if not impossible,  to classify the feelings.   In order  that the
feelings may be judged in consciousness there must be differences in the feel-
ings themselves.  Tliere are so many variations in the phenomena  and these are
so closely inter-relatud to the physiological  and psychic phenomena that their
analysis is  very difficult.   In dividing feelings on the basis of pleasure and
pain we require to settle the question of indifferent feelings; if we admit such
indifferent feelings then we must determine the dividing line, while if we deny
the existence of indifferent feelings, then we must  recognize almost  nnmber-
le^s variations in the pleasure and  pain feelings.   These differences in feel-
ing cannot be  absolutely determined, because one shades iuto the  other.  It is
difficult, for example, to say that purely  ethical feelings are absolutely sepa-
rated from nhysical conditions so that we are unable to state the difference be-
tween these two classes.
    Feelings  can be classified only, if at all, in connection with other psychic
activities.  * According to the physiological theory  feelings have been classi-
ged into (1) those associated  with sensation, and (2) the aesthetical  feelings,
if the end  organs are,  or are not,   directly  associated with vital functions.
According to  the psychic theory, feelings have been divided into (1) formal,
      V i<r on the form of the representation of ideas;  and (.2) material,  de-
nendin^on the content of the ideas.  According to  the theory of  feeling as
   a  ■ ° l  the feelings may best be classified on the basis of the ps.ychic activ
un  eriv      ^ accompany.  It is from this standpoint that we get the four-fold
lties w        .      j.   commonly given (1)  sensuous, depending on sensa-
       /0,  ooethetic  depending on the conscious  forms associated with per-
tions:  (*)  aeM" 
116
ception and imagination;  (3) intellectual,  depending on the higher  thinking
functions; and  (4) moral,  depending on the volition and desire.   Depending
on and arising from complex  combinations of  these simpler feelings we find
(5) higher feelings, depending on the complicated social relationships.
    Among  the  different  feelings  we find variations depending  on tone,
rhythm, matter and intensity.  Feelings are  acknowledged by all to  be either
pleasant or painful  and from  this standpoint  it is claimed that  they can be
classified in the pleasure-pain  series,   taking an ideal point  to represent the
point of indifference.  So far as consciousness seems to indicate there  are no
feelings which do  not possess in some degree the element of  agreeable or dis-
agreeable,  so that  the tone would represent some shading  of these two quali-
fies.  Feelings have time  relations like all  other psychic  phenomena  and
hence have rhythm,  the rhythmic movement being determined by variations in
the nerve conditions or the ideational element?.  Some claim that feelings can-
not be distinguished on the basis of content, as all feelings are determined by
the quantity of pleasure or pain.   This, however, is contradicted by our con-
scious experience.   Feelings  differ in quality and these qualitative differences
depend on differences in the  body organism or in the  ideational  elements of
the mind, forming the basis  of  the differences in content.  Feelings  differ in
strength,  the strength of  feeling often passing  through rhythmic variations,
the differences in strength being determined  by the condition of the nervous
mechanism and of the  termimal organs, and  the ideas of the  mind.
  (1)  Some feelings are so closely connected with sensations that  it is diffi-
cult to separate them.   Yet sensations and feelings are  distinct.  There must
be a stimulation of  the terminal organ  in order to  produce a  sensation,  the
sensations reprepresenting the factors of perception.   Feelings are in  all prob-
ability different from  sensations,  at least to the extent of being  pleasurable
and painful,  although  it is  possible  some feelings may be  neither charac-
teristically agreeable or disagreeable.  There are constantly impulses passing
from the peripheral parts of the body to the  cerebral centers, some being too
weak to arouse or pass into consciousness,  while others excite consciousness;
both of these classes  of impulses  give rise to  feelings which  are associated
with the psychic life.  It is  difficult to tell where  the  sensuous  of  feelings
pass into the aesthetic feelings.  The   distinctive  aesthetic  feeling depends
however on  raising ourselves  above   the purely  sensation  basis,  the true
aesthetic  feelings  arising in connection  with perception and imagination.
These purely aesthetic feelings  originate iu connection with the application of
space and time relations to the purely  sensuous feelings.  This  takes place
in connection with audition   and vision.   Audition represents  the chief sense
in connection  with  which the  seusation feelings  become aesthetic  from the
standpoint  of time,  and vision the  chief sense in connection with  which  they
become aesthetic from  the  standpoint of space.  In connection with feelings 
117
 there is the blending of certain  intellectual elements,  these elements  deter-
 mining  the character of the feelings.   Feeling is closely  connected with all
 psychic activity, pleasure being associated with time  relations of  ideas that
 are not excessive and do not involve any strain  upon attention; while painful
 feelings are associated with  excessively slow or rapid mental activity involving
 a psychic strain.  Feelings  are largely  dependent  upon association,  all the
 forms of feeling, sensuous,  intellectual  and aesthetical being governed by as-
 sociation.   It is here that we are able to account for complex individual and
 natural eccentricities of feeling, as well as the higher feelings.
     When feelings are accompanied by an  increased intensity in consciousness
 they are associated with organic and  functional  body  changes, these changes
 reacting on the feelings and modifying the feelings to  such an extent that the
 feelings are regulated  by body changes.  Affections and  emotions  represent
 such feelings subjected to intensification under  the action and reaction  of or-
 ganic changes; passions represent states of feeling which are entirely depend-
 ent on some excited or abnormal condition of the organism  or its  parts.  All
 the  emotions and  passions  arise in  impulse, experience associating the im-
 pulse with perception and psychic activity,  this  forming the basis  of the emo-
 tion or passion.  These  impulses are   either those of attraction or repulsion,
 these two varieties of instinctive impulse forming   the basis of  the opposite
 emotions and passions.   All the emotions  are dependent on some  sudden var-
 iation in  the time  relations  of the  ideas, involving an interference with  the
 even and steady flow of  ideas, and resulting in that abruptness that character-
 izes the emotions and passions.  This disturbance reacts on the psychic activ-
 ity and introduces  an element of interference into the  conscious life,  indicat-
 ing a molecular  disturbance of the body  organism, an interference  with the
 body processes and excitation of the sensory, motor and  senso-ideo-motor
 centers  of the brain.  The emotions have been classified as they affect the dif-
 ferent parts of the organism, for example, fear or shame  upon the blood cir
 culation; anxiety and strong  hatred  affecting  the  secretory and  nutritional
 actions.   As a complex of these feelings and emotions  we find mental moods
 when the general character of   feeling,  sensation  and perception  affects the
 psychic life.  Moods are determined by the abnormal sensations arising from
 different parts of the  organism, these being  accentuated by cerebral  action in
 connection  with an abnormal train of ideas, abnormal feelings, etc.
     Closely connected  with   feelings are the feelings  of innervation associated
 with the body position and the attitude of the different parts of the organism to
 the body and to one another.  These feelings depend on development, arising
 primarily  from complex sensations   involving  the  muscles, tendons, joints
 skin, etc.  Thus the feelings associated with the body  position seem  to arise
 peripherally, being rather mixed sensations than feelings, localized under the
 strono- influence of perceprion and association.  In body movements we find the
 influence  of conscious states in  automatic or voluntary  movements  and the
absence of  consciousness in purely reflex movements.  There is a  constant 
118
tendency  either into  or away from consciousness, indicating that the  peri-
pheral processes  which give rise to these movements either  tend  to  pass into
cerebral activities or tend to fall away from cerebral activities.  There  is thus
a close relation between  these movements and both feeling and  ideation.   The
influence of feeling  and ideation may be found  in  connection with  the modi-
fication of  innervation, emotion or  ideation  reacting upon the  muscles and
nerves through the cerebral centers.  The  same effect is found in connection
with the association of sensations that are analogous, the combination  of  such
sensations producing  intensification  of impulse  to  movements.  By develop-
ment certain particular movements  come to be associated  with special  percep-
tions, these being illustrated perhaps best in the gesticulations and movements
employed by dumb persons as signs of ideas.
     In  regard to the higher psychic functions very little  satisfactory work
has been done from the standpoint of psycho-physiology.   In these fields the
introspective method  has  yielded the best  results, but when we  try to apply
the results to  the brain  processes we come  to  a standstill.  We must accept
the phenomena of consciousness on the evidence of  consciousness  itself, at-
tempting thereafter to find a physiological  basis for these facts  in the  cere-
bral hemispheres.  Here the  brain processes  cannot be observed and there-
fore nothing definite can be formulated regarding them.  In  entering the high-
er psychic field we  first meet with consciousness.   We   cannot define it but
take it to represent the existence of  a psychic life,  which is  represented by
different particular states of consciousness.  Hence, consciousness is not gen-
eral but particular as  applicable at a particular moment  and in a  particular
state of the mental life.  From this standpoint   consciousness represents the
condition implied in all our inner experience.  When we are conscious we are
conscious of possessing a certain form of psychic life  and this  must  be dis-
tinguished from our consciousness of self-existence in  which the  conscious
state is attributed to  some existing ego.  Thus  self-consciousness represents
a form of  consciousness in which the ego  bears the prominent  place.   The
cerebral hemispheres are  regarded as the seat of  consciousness,  but this
simply implies that the  cerebrum represents the center of those molecular and
nervous processes which are associated with the phenomena of consciousness,
so that changes taking  place  external to the brain become  conscious to the
brain centers by being represented  in the brain changes  themselves.  Hence
the conditions of  consciousness are associated  with the blood  supply  to the
brain and the  normal  activity of the brain substance.
     Memory represents a psychic function  which it  is  claimed has  three dif-
ferent aspects,  retention, reproduction,  and recognition.   Eetention and re-
production must be  associated with recognition in order that  they may be
recognized as psychic  processes.  Letention does not represent a psychic ac-
tivity, but rather depends upon either   a brain movement or  movements,  a
cerebral impression or  a tendency  to movement or impression in connection
with the brain.  It is  difficult to  distinguish  between after  images in the 
119
case of a sensory impression and the memory picture of this sensory  impres-
sion.  We have seen that some images of sensory impressions perist for a long
time after the cessation of the impressions themselves.  The nerve cells con-
nected with  psychic processes become permanently modified as a result of stim-
ulation ;  this is the basis of all the adaptations found in connection with the
development of the complex neural mechanism.  If we take it that this  com-
plex neural mechanism is subject at all times to this general biological prin-
ciple, then as this modification  becomes perpetuated under the  influence of
nutrition, molecular changes and heredity,  we find the basis for retention in
these modifications of the nervous system.   In regard to the reproductive as-
pect of memory we must presume  the existence of association  in connection
with the perpetuation of the neural modifications.   At the same time we  must
remember that all the molecular changes are not perpetuated,   hence  the for-
getfulness of certain phenomena involves the dissolution  of certain  associa-
tions that might have been held fast.  Memory cannot be localized in any one
organ or part of   an organ,  like the cerebral  areas.  Hence Newman   says
'•there are a hundred memories,"  each psychic function having its  own defi-
nite association.   Attempts  have been  made  to formulate  and  explain the
laws of association at the basis of the memory  power of reproduction.  Some
claim that all laws of association may be reduced to a single principle like the
law of contiguity.  From  a physiological standpoint  there is no foundation
for such a  supposition, because  the mental processes are  multiform and no
single iron-clad principle regulates all these processes.
     In regard to the will much discussion has taken place from a psychological
and psycho-physiological standpoint as to its nature and action.  Here we are
apt to fall into the ethical and theological  controversies.   Will is used in the
sense in which it is applied to those psychic phenomena which imply the con-
scious activity involved in body movement or mental action.   Here the phys-
iological basis is to be sought in the automatic action of the nerve cells in the
central system, in virtue of which molecular changes are originated independ-
ent of the impulses derived from external stimulation.  This automatic power
is inherent  in some sense in the cerebral centers, all of these  centers capable
of originating molecular changes having this independent will power.  While
the nower of origination is general,  its exercise  is particular.  Hence,  vo-
lition  takes place only in connection  with  definite movements or definite
mental activities.  Hence  the physiological  basis of volition   is  found in the
n tivitv of these cerebral centers which are concerned in  ideational  activity.
From the standpoint of psycho-physiology there is will of different  degrees of
f   i      There are acts of will  in which  there is the absence of  conscious-
  p«f«inHreedom of choice; ori the other  hand there are acts of  will involving
5 Vh * tion freedom of choice and determination to act in a  particular way.
deliDerat   ,^    ^ freedom  of will depends on development,  the  physical
ijromw   hich is a brain passing through the different stages of  evolution,
     b?e of adapting itself to the developing conscious life and also  capable of 
120
manifesting  its activity  in varying shades of reflex and automatic actions.
Hence the act of will involves the blending of a number of  physiological pro-
cesses under the direction of  the cerebral centers.  All the  lower elements,
including sensation, perception, feeling, attention and memory contributing to
and enforcing  that choice which is essentially  at the basis  of will.   Choice
represents that element of the psychic activity without which will would not be
possible,  tnat climax of  mental influence exerted  over the body.  We find
certain conscious states determined by  the will becoming the basis of certain
molecular variations in the higher cerebral centers and  here the physiological
basis  of volition is to be found.   Choice is accompanied by the feeling  that a
strain has been removed,  indicating the presence of conflict in the nerve com-
motions and the  over-mastery of one of these.   The choice represents some-
thing psychic that adjusts  certain  physiological conditions of  the organism.
    In regard to the nature of the mind it is difficult to state anything definite
from  a purely psycho-physiological  standpoint.   Mental reality and  the na-
ture of this psychic  entity belong to  metaphysics rather than to psychology.
And yet in summing up the results of our investigations it is necessary to take
some definite stand in regard  to mental reality.   Materialism denies that the
mental phenomena can be  attributed  to a really  existing mind, the material
nerve substance forming the only basis of reality in connection with  mental
phenomena.  The  mental  phenomena according to this represent  phenomena
of the  brain substance.  Here  however we are attributing phenomena that are
psychic to a physical substauce and for  this reason among others we are draw-
ing a  false conclusion.  We  must remember  that although  conscious  states
are associated with molecular changes in the brain substance we caunot identify
these.   Sensation, perception  and ideational states are  entirely different from
chemical or physical changes in the nerve substance.  Yet at  the basis of all the
psychic phenomena there are physiological changes.  This does not mean that
the mind is the product of brain changes, although the mental phenomena are
in> some way associated with variations in the centers  and nerve fibers found in
the nervous mechanism. All the changes in  the centers depend upon previously
existing  conditions  in those centers  and in the  neural and  neuro-muscular
parts  of the  body  organism,  the mental  variations  depending upon  these
changes and also to a certain extent at least governing these changes.  Hence
from a physiological standpoint we must take  account  of the  existence and
activity of a real mind, even although its existence requires to be demonstrated
by metaphysics.  The reality of the mind is undoubted.   Materialism claims
that the mind represents simply a  series of phenomena associated with and
produced by changes in the cerebral centers.  It is true'that all  psychic   life
is based upon senso-motor activities, but these activities represent  psychic as
well as physiological changes.  From the psychic standpoint  it represents those
elements of  sensation, perception, apperception,  etc., associated with all our
knowledge and activity.  There is as we have  seen a close correlation between
the physiological and the psychic activities,  the nature, intensity and coloring 
121
of the psychic being determined by the  nature, intensity and  coloring  of the
physiological.  But these correlations do  not exhaust the  description  of the
mind.   We find mental phenomena that  cannot be classed under  the head  of
senso-motor activities, because these are purely psychic activities.   Percep-
tion represents a knowledge of things  and complex sensations do not give us
a correct idea of things.  To account for this there must be primarily a knowl-
edge of the self and a recognition of the subjective actiyity of the mind.   What
applies to perception applies  equality to the entire psychic  life.   Hence be-
hind all the activities both psychic and physiological lies the mind.   It is true
that in all science observation is the method of  investigation, but iu order to
carry out this method there must be psychic activity.
    In connection with this real mind there is a real mental  development.   It-
does not represent simply a series of complicated sensations,  becoming  more
complex as  the process of  development progresses.   There is a plan  in the
development and  this plan  has its history.  In every form of development,
even the pnysical, there are underlying psychic  factors, which cannot  be re-
garded  as simply atoms of existence.  The field of  consciousness  is being en-
larged in connection with  development, and  every newly  developed  field of
consciousness exists in relation to that  self-consciousness  that  underlies  all
the states of consciousness.  Hence development applied to mind is different
from development applied to the organism or its organs, because we are  deal-
 ing with psychic factors that cannot be  limited by  purely material  progress.
 Hence the mental development represents the progressive  manifestation of the
inner self in consciousness, this inner self unfolding itself in the physiological
 activities associated with the body  organism.   This mental  reality  underlies
 all attempts  to gain knowledge of the  external wprld.  Associated with this
 attempt to gain knowledge is the synthetizing  function of  the mind in  virtue
 of which the mind  unites all phenomena into a synthetic whole,perception and
 apperception unifying in this way the numberless phenomena  of the sensitive
 life.  This unit being depends upon self-consciousness and memory, underly-
 ing which we find the knowledge  of self, this self being associated ryith differ-
 ing states of consciousness, all of  these states  being  unified  in the  self.   If
 this  unity  is lost,  then,  memory,  self-consciousness  and  reason no  longer
 possess the power of self development.  Whatever unity is imparted to the ex-
 ternal world is the subjective unity of the mind.
     In regard to the origin, ultimate  nature and final destiny of the mind we
 cannot enter into the discussion of these topics because physiological  psychol-
 ogy throws  no light  upon them.  It is evidently  non-material and  real, but
  1  il   this involves the  further fact that mind  is spiritual  and to what ex-
 tent it  is purely spiritual the physiological and psychic  processes  give us no
 light. 
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