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and on metabolism in its turn depends the activity of organic
beings. The form and the manner in which the accumulated
potential energy is applied depends on the structure of the
organism. There is a fund of energy in c\ery organic ceil, but
the use made of this fund depends on the structure of the

Thus the principle of the conservation of energy presses its claims;
ever more closely. Vegetative life, the functions of alimentation,,
might perhaps be yielded to it with a good grace. But even the
nervous and muscular systems cannot escape subordination to it-
The energy consumed in all nervous and muscular activity is
stored up during the process of alimentation. The nervous and
muscular systems themselves are only highly perfected (differen-
tiated) apparatus for the exercise of functions which are carried on
in an extraordinarily simple form even in uniform, structureless
protoplasm. Even here an e.xcitation at one point of the organism
can be transmitted through the mass, and can set up movement at
quite different points or in the whole. The increasing division of
labour makes distinct systems necessary in the higher organisms,
but this more elaborate formation (differentiation) is not exempted

1 Cf. Panum, Indlednittg til Physiologien ("Introduction to Physiology"), and ed.
(Copenhagen, 1883); (l\\?ix\t<,V^o\nn, Anatoiiiie it I^hysiologie Cel/u/aiyes (V^r'xi, 1S73),
Introduction; Claude Bernard, /.efoiis siir les Phe>ioinenes tie la Vie (Paris, 1878),
(note especially the following detinite statement : " Quelque soit le sujet qu'il etudie, le
pliysiologiste lie trouve jamais devant lui que les agents mecaniques, physiques, ou
chimiques," p. 52); Exner, Physiologic tier Crosshirnrimie (" Physiology of the Cerebral
Cortex"), 1879 ; Hermann's llandbiich tier Physiologie, ii., 2), pp. 1S9-191.

- The power of forming organic combinations out of inorganic elements is not wholly
wanting in the animal organism, although it is in the plant organism that its most favour-
able conditions are found. Cf. Pfliiger, " Ueber die physiologische Verbrennung " ("Oi
Phyiiologicul Combustion"), Arckiv/iir J'Jtysiologie, xi. p. 345.

D 2


from the general elementary lavvs.^ These still hold good, only
in extraordinarily complex and often impenetrable relations.
Chemically and physically, the action both of nerves and muscles
is different during and after function from what it is before function.
The blood that circulates in muscles when in action, contains
several per cent, less oxygen and more carbonic acid than the blood
in quiescent muscles. The nervous tissue — the fibres as well as the
central organs — cannot function without an ample supply of blood,
which contains the material necessary to the increased change of
matter that results from function. The brain is affected by every
change in the circulation of the blood ; both anemia and hyper-
aemia cause a disturbance in its activity. Brain-work uses up the
organic capital just as much as the activity of any other organ.

What really takes place in the nervous system during its activity
has not yet been made clear. This only is clear, that it can be
nothing material that is transmitted from one end to the other
(such as the so-called " animal spirits," formerly believed in).
Probably the nervous process consists in a change passing through
the nerve fibres, a release of tension, caused by external excitation
(the irritant), and transmitted from part to part, so that one nerve-
element serves as irritant in relation to another. The tensions
thus set free seem to be of a chemical nature ; but there are
various difficulties in the way of a purely chemical theory of the

4. {a) The plant uses up its energies wholly in the life of nutri-
tion. It absorbs and secretes matter, grows and propagates. It
finds what is required for this in its immediate proximity, and must
so find it in order to live. Air, water, light, &c., must bathe the
surfaces of the plant, if it is to keep alive.

The plant is like a foetus, it remains in the maternal bosom of
nature, and has not made its way out to independent, individual
life. The foetus obtains its sustenance directly from the maternal

_ 1 "The nerves are to be regarded in the first instance merely as those points in the
tissue through which the effect of the excitation is most easily transmitted, without its
being necessary for us to suppose that there are from the beginning more mysterious forces
in them than in the other parts. " — Lotze, A llgemeine I'hysiologie des Kdrperlichen Lebens
(l^eipzig, 1850), p. 386. It has been thought a proof of this, that the effect of narcotics on the
nervous tissue differs from their effect on other organic tissue in degree and rapidity only.
Cf. Laycock, " F"urther Researches into the Functions of the Brain " (The British and
Foreign Medico-Chiriigical Review, July 1855), p. 185 ; Claude Bernard, Lefons sur les
Phenomenes de la Vie, p. 289 ; Herbert Spencer, Principles of Psychology, i. p. 631

- Cf. h. Hermann, Allgemeine Nervenphysiologie, 1879 (Hermann's Handbitch der
Physiologie,\\., i), pp. 186-1^3; Panum, Nerve^'dvets, de kontraktile Viivs og Nerze-
systemens Pysiolo^ ie (" Physiology of the Nerve-Tissue, of the Contractile Tissue, and of
;)ie Nervous System") (Copenhagen, 1883), p. 56.


organism. Animal life proper is conditioned by not having evcrj'-
thing thus prepared for it. The animal must search, work, and
fight in order to satisfy its wants ; it must therefore face the ex-
ternal world as a whole, must be able to gather together its energy,
and to apply it in definite directions. At the same time it must be able
to take into account relations and facts which do not directly affect
it at the moment. These requisites are supplied by the nervous
system ; through it the various parts and departments of the organ-
ism are brought into close mutual relation, so that the organism
becomes a whole in a stricter sense than can be said of the plant ;
and the nervous system makes it possible for the relations of the
external world to determine the movements of the organism, not
only directly but also indirectly.

It is true that it has not yet been possible to establish the exist-
ence of nerves in the lowest animal organisms, while on the other
hand many plants execute functions similar to those which in the
higher animals are executed by means of the nervous system; still,
speaking broadly, the plant and the animal may be described as
two types of life, the one of which stands only in direct, the other
both in direct and indirect, inter-relation with its surroundings.
The higher we come in the scale of animal life, the greater is the
part played by the nervous system, because the inter-relation with
the external world extends in ever wider circles, and thus grows
less and less direct and momentary.

{b) The simplest form of nervous activity is the so-called reflex
movement, where an excitation is carried along an afferent
(centripetal) nerve-fibre to an internal centre (a ganglion), and
there in its turn frees an impulse which, through an efferent
(centrifugal) nerve-fibre, sets in motion a muscle or some other
organ {e.g. a gland). Here we have the simple schema, which
seems to be repeated at all stages in the development of the
nervous system, only in extraordinarily numerous co-ordinate
and subordinate strata. As a rule, the ganglion not only send?
outward-going fibres to the organs in which movement is to be ex-
cited, but inward or upward-going fibres also pass from it to higher
centres, which in this way receive impulses from several sides-
impulses which may in part strengthen, in part inhibit, one another.
The ganglion itself exercises an inhibitory influence on the impulse,
for, as can be shown by experiment, the course of a nervous process
is much slower in the brain and spinal cord than in the peripheral
nerves. This inhibition seems to make it possible that the impulse,



before he\n^ transmitted further, may be changed by the influence
of other impulses. And to this central elaboration of peripheral
excitations is due the fact that the movement which they set free is
determined, not merely by local and momentary influences, but
alio to a certain extent by influences from the whole organism.
The central nervous organs are therefore modifying and combining

We have a very simple example of this relation in the suckers of
the cuttle-fish. Each sucker on the arm of this animal has its
own special ganglion, and so can be made to contract and. suck
when an object is brought into contact with it alone. This may happen
e\en if the arm is separated from the rest of the animal. There is
here a nervous function in its simplest form— transmission of the
excitation to a simple central organ, and in this organ the setting
free of an impulse towards contraction. But now the ganglia of
aU the suckers are connected both with each other and with the
liighest centres of the animal (the caruncle), so that, in taking
hold of an object with the whole arm, the animal may set all the
suckers in action at once. The single elementary nerve-function
then takes its place as member of a whole system of functions.

This relation between subordinate and principal centres can be
established also in the case of higher animals, though the closer
connection and interdependence of the organs make it more diffi-
cult to survey the relations, the higher we ascend in the scale of
development. The independence of the subordinate centres is
greater in cold-blooded animals (as for example the frog, which on
this very account is the frequent subject of physiological experi-
ments) than in warm-blooded, and among the latter it is greater in
birds and rabbits than in the ape, and much greater than in man.
The complete removal of both cerebral hemispheres can be survived
only by animals in which the cerebrum has not attained any great
degree of development. The higher forms of mammalia, on the
contrary, perish quickly when deprived of the entire mass of the
cerebral hemispheres.

(c) The vegetative organs are connected by afferent and
efferent fibres with the spinal cord and brain, and are regu-
lated from these centres. Nevertheless, there appear to be
special nerve-centres, of a certain degree of independence, either
within, or belonging to, some of these vegetative organs. If the
heart of a frog is cut out, it continues to beat for several hours,
thus proving its relative independence of higher centres. Experi-

II] MINI) AND 130DY 39

ments (on dogs and rabbits) have shown that the pulse beats
faster when, through section of the nervus vagus, the heart is
freed from its connection with the medulla oblongata. In moments
of violent terror the heart of the rabbit stands still, then beats
faster than before : after section of the nervus vagus, no influence
upon the beat of the heart is perceived. The same holds good
of the intestines. The peristaltic movements may continue, after
the connection with higher centres is broken.^

The spinal cord is an important seat of reflex movements. In a
headless frog rellex movements in all directions can be set up
by a sufficiently strong stimulus on any part of the skin. What
is remarkable in these movements is their co-ordination and
purposiveness. So far as it has been possible, by section of the
spinal cord and application of the stimulus below the division, to
produce reflex movements in mammalia, these have seemed to be
to a certain extent co-ordinated, but not so purposive as in the case
of frogs. The spinal cord seems in the higher animals to act more
and more exclusively as the connecting link between the brain and
the peripheral parts of the organism."

In the viedulki oblongata are localized a number of centres of
importance to the continuance of life. These centres can act in-
dependently of the higher parts of the brain, and can reflexly set
in motion very complicated mechanisms. This is so, for instance,
with the respiratory centres, the centre for regulating the nervous
system of the heart, for the secretion of saliva, for deglutition, and
for the excretion of urine. '^

A frog deprived of the cerebrum, but still retaining the mesen-
cephalon (the brain-ganglia situated in front of the medulla oblon-
gata), proves itself still in control of the motor apparatus required for
independent movements ; but it appears to move only when stirred
up by a definite sensory excitation. It lacks the power of taking
the initiative. It has this supeiiority over the mere spinal frog, that
it can be moved by slighter excitations, and is consequently not so
passive. While the spinal frog is of course not susceptible to light,
-and sinks when thrown into the water, the mesencephalon frog
avoids a very dark shadow, and wnen it is thrown into the water,
the stimulus given by the movements of the particles of water

1 M. Foster, Text-hook of Physiology (London, 1877), p. 81 ; Eckhard, Physiol, ties
Riickcnmarks (^^ttxm^wn, ii., 2), p. 71 ;" Exner, Physiol, tier Grdsshirftriniie (HeTnoinn,
ii., 2), p. 289.

2 M. Foster, p. 420. [Cf. Ferrier, Functions of the Brain (2nd ed. 1886), ch. 11. ( rr.)]

3 {Cf. Ferrier, ch. iii. (Tr.)]



causes it to swim. But some outer impulse is always required to
set it in motion. Similar features are found in birds and mam-
malia, when these survive the removal of the cerebral hemispheres.
They cannot take the initiative, or help themselves in cases of any
difficulty, but, on the other hand, single elementary excitations
call forth movements, some of which are very complex. The
physiological significance of the cerebellum is not yet certain. It
is thought by some to help in the co-ordination and combination
of movements.^

{d) The special work reserved to the most important part of the
brain — the cerebrum — can be no other than this : to elaborate and
combine the elementary excitations received in the medulla oblon-
gata and in the brain-ganglia, and to employ, in accordance with
the result of this elaboration, the apparatus lying ready in these
lower parts of the brain. The cerebrum forms the keystone to the
ingenious structure of the nervous system. The nearer it is
approached, the more complicated become the relations, the more
numerous the nerve-cells and connective fibres. Here are laid
down lines which render possible the most complex interaction
between different impulses. When we reflect that every excitation
works through release of tension in organic cells, and that the
result of this release in the individual cell may be connected in the
cerebrum with results similarly obtained from millions of other
cells,''^ we grow giddy at the thought of the combinations which are
here possible.

The question whether the cerebrum functions as a whole, or
whether the several functions are localized each in its special tract,
has received conflicting answers, and is even yet a subject of
dispute among physiologists. Gall, the founder of phrenology,
maintained a very far-reaching localization of all the higher and
lower mental powers, but brought the idea of localization into
disrepute by his uncritical method and his fantastic cranioscopy.
The reaction against his doctrine is represented by Flourens, who
argued from his experiments that any part whatsoever of the cere-
bral hemispheres may be injured or removed without detriment
to the brain-functions.

This theory prevailed for about half a century, during which

] 1 Kerrier, chs. iv. vi. (Tr.)]

- Meynert and Kain independently calculated the number of nerve-cells In the cortex of
the human cerebrum to be a thousand millions (Meynert, Zitr l\lechanik desGehirnbnues
(Vienna, 1874), p. 7). — "A portion of grey matter upon the surface of a convolution,
not larger than the head of a very small pin, will contain portions of many thousands of
nerve-fibres " (Beale, quoted by Maudsley, Physiology of the Mind, p. 117).

n] MINI) AND liODV 41

time it was placed in doubt only by Broca's discovery (1S61) that
the seat of the most important central organs of speech and
discourse is in the third frontal convolution of the left hemi-
sphere. A new period of brain physiology began with the experi-
ments undertaken by Fritsch and Ilitzig (1870). These investi-
gators thought it possible to prove that stimulation of definite
points on the surface of the cerebrum sets up definite movements
of definite parts of the body. Later, Hermann Munk in parti-
cular has tried to prove the existence in the cerebrum of distinct
organs for the apprehension and recognition of the elementary
sensuous impressions (a sphere of sight, a sphere of hearing, &.C.).
There would thus be grounds for again believing in a localization,
a division of labour in the cerebrum, but with this great difference,
that only the elementary activities of the mind would be localized, not
thought proper or " intelligence." ' Hut c\ en with this limitation, the
new theory of localization is not undisputed.'- Goltz enters a
protest against it, taking up an intermediate position between
Flourens's doctrine and the new theory. He does not deny the
possibility of a localization of the various cerebral functions, and
he disputes the justice of Flourens's assertion that any part of the
cerebrum can act vicariously for any other. The removal of large
parts of both hemispheres gives rise to permanent weakness. But
the weakening of definite sensory and motor functions, which
accompanies the removal of certain parts of the surface of the
cerebrum, Goltz explains partly as phenomena of inhibition
due to the operation. If the injury is not too extensive, the
animal recovers, a fact of which the localization theory gives only
the forced explanation that new special centres are formed in
brain-tracts where no such centres previously existed.''

"W'hile it is still disputed how far a localization of the special
sensory functions exists in the cerebrum, the disputants agree that
the higher mental manifestations arc not tied to definite cerebral
tracts. Both Cioltz and Munk unite with Flourcns in thinking that
the most important cerebral functions, the actions from which we
conclude intelligence, feeling, passion, and natural impulse, cannot
depend on definite sections of the cerebrum.''

' Intelligence has its everywhere in the cerebrum, and nowhere in particular ; for
it is the abstraction and the resultant of all ideas springing out of sensuous perceptions." —
H. Munk, l/e/'er i/i'r J-'ii)iA-(i0ftr>/ i/tr Crvss/iiryir/mfe {her'an, iS8i), p. 7-5.

- [The reference to Soltman, given in the Ciernian ed., is here omitted at Dr. HOflfding's
request, later experiments having led to contrary results. (Tr.)]

•* Cloltz, in yjh'iger's Archiv Jiir Physiologie, vols. .\.\. to .\.\vi.

•• Goltz, in Pjh'ii^t-r s Archh; xxvi. p. 35. fA full discussion of the question oflocaliza-
liou will be found in Ferrier, ch. vii. scj. (Tr.)]


(e) One or two examples will serve to indicate the physiological
relation of the cerebrum to the remaining nerve-organs. The
study of disturbances of speech seems to lead to the conclusion
that, in the parts of the brain which lie below the surface of the
cerebrum, only the arrangements for the mechanical execution and
combination of sound-producing movements are to be found ; while
the formation of syllables and words, belonging to speech proper,
takes place in the surface of the brain. The primitive sounds
of the little child may perhaps have in the medulla oblongata alone
the conditions of the mechanism which controls them, while the
fully formed sounds of a language, which are joined in syllables
and words, and are conditioned by the development of intelli-
gence, involve the action of higher centres.^ The movements set
up from the mesencephalon, medulla oblongata, and spinal cord
have the character of involuntary movement. On the other hand,
actions which are directed by the will, inasmuch as they involve
more or less distinct ideas of movements, can be executed only
with the co-operation of the cerebrum." While, as above noted,
elementary sense-excitations exercise their influence even upon
animals which have been deprived of the cerebrum, the proper
grasp and comprehension of the excitation is possible only where
the cerebrum is uninjured. After extensive injury to both the
cerebral lobes at the back of the head, a dog no longer grasps the
significance of what he sees and hears. He does not turn when
threatened with the whip, does not notice his food unless it is set
in the usual place, is not startled by noise, does not obey when
called, remains unaffected by tobacco smoke, and will eat a dead
dog without any sign of disgust. On the other hand, a dog in this
condition goes round obstacles lying in his way, and avoids
dazzling light. Goltz and Munk give much the same account
of the animal's condition, but disagree as to the explanation.
According to Munk, this " soul blindness," as he calls it, is
connected with the injury to a certain definite portion of the
surface of the brain. According to Goltz, any extensive injury to
the cerebrum produces a similar condition. Munk explains it
psychologically through the loss of the memory-presentations, by
which new excitations may be recognized and understood, while
Goltz explains it through a general intellectual dullness, espe-
cially perhaps want of attention. Both explanations bring oui

1 Ad. Kussmaul, Die Sldrungeii der Sprache (Leipzig, 1877).
- Munk, p. 51 sc}. ; cf. Goltz, in F/liigers Archiv, x.wi. p. 6.

ri] MINI) ANT) UoDY 43

the importance of the cerebrum in relation to the subordinate

liut the cerebrum stands not only in a positive, but also in a
negative, relation to the subordinate nerve-organs, inasmuch as it
is able to inhibit their activity. The vegetative functions are for this
reason carried on more vigorously during sleep, when the cerebrum
does not interfere so strongly as in the waking state. Even in the
lower animals, where its position is by no means so prominent as
in the higher, this inhiliiting influence is noticeable. When the
headless frog recovers after the operation, its mobility becomes
even greater than before. The subordinate centres respond to
excitations more readily than the higher. This is a simple
consequence of the fact that in the higher centres excitations
have to go through along process — must be confronted, so to speak,
with so many other claimants, that the individual excitation cannot
get its own way so easily and absolutely as in the less complex

The increased vigour of the subordinate nervous processes after
the removal of higher centres is explained by some as due to the
fact that the quantity of nervous activity which an afferent
nerve arouses in the lower centre is now spread over a smaller
sphere, and must consequently produce speedier and stronger
effects. But all the phenomena cannot be thus accounted for.
Strong cerebral activity, as in sudden and powerful stimulations
of sense, in agitation of feeling, in the exercise of thought, seems
to influence subordinate centres immediately, preventing direct
excitations from taking effect as they would otherwise."

Through such inhibiting activity that which passes in the higher
centres becomes of importance to the lower. We know, to take
a simple instance, how sneezing may be prevented by a sudden
sense-excitation. A violent emotion or pain inhibits the action
of the heart (under the influence of the brain through the medulla
oblongata and the nervus vagus) and so causes fainting. Great
dread may pre\cnt secretion of saliva, a circumstance which lay
at the bottom of the " ordeal of God," in which the accused person
was held to be guilty if he could hold rice in his mouth without
welting it. Weeping can be prevented by a sudden, gripping
stimulus ; peristaltic motions, by an affection of the nervus
splanchnicus. It is not only by single sense-stimuli that inhibiting

1 Goltz, ill Pfliigers Archiz>, xxvl. p. 42 seg ; Munk, p. 29.
■- Eckhard, Physiol, des Riickenniarks (Hermann, ii. 2), p. 37.


forces arc liberated in tliis way : more complicated brain functions
exercise a similar influence ; and in a later chapter we shall see
that an important part of the supremacy of the will is connected
with this. All that need be noted at present is, that the phenomena
of inhibition are the stronger the fuller the organism is of life,

Online LibraryHarald HøffdingOutlines of psychology → online text (page 5 of 41)