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Marine Biological Laboratory Library
Woods Hole, Mass.
Presented by
Dr. Wm. Amber son
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HUMAN PHYSIOLOGY
BY
PROF. LUIGI LUCIANI
TRANSLATED BY
FRANCES A. WELBY
WITH A PREFACE BY
PROF. J. X. LANGLEY, F.R.S.
In 5 vols. Illustrated. 8vo.
Vol. I. Circulation and Respiration. 18s. net.
Vol. II. Internal Secretion — Digestion — Excretion — The
Skin. 18s. net.
Vol. III. Muscnlar and Nervous Systems.
Vols. IV. and V. [In the Press.
LONDON : MACMILLAN AND CO., LTD.
HUMAN PHYSIOLOGY
MACMILLAN AND CO., LIMITED
LONDON • BOMBAY • CALCUTTA
MELBOURNE
THE MACMILLAN COMPANY
NEW YORK • BOSTON • CHICAGO
DALLAS • SAN FRANCISCO
THE MACMILLAN CO. OF CANADA, LTD.
TORONTO
HUMAN
PHYSIOLOGY
BY
PROFESSOR LUIGI LUCIANI
DIRECTOR OF THE PHYSIOLOGICAL INSTITUTE OF THE ROYAL UNIVERSITY OF ROMK
TRANSLATED BY
FEANCES A. WELBY
WITH A PREFACE BY
J. K LANGLEY, F.E.S.
PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OP CAMBRIDGE
IN FIVE VOLUMES
VOL. Ill
EDITED BY
GORDON M. HOLMES, M.D.
MUSCULAR AND NERVOUS SYSTEMS
MACMILLAN AND CO., LIMITED
ST. MARTIN'S STREET, LONDON"
1915
COPYRIGHT
NOTE
THE third volume of Professor Luciani's Human Physiology,
which deals with the muscular and nervous systems, has been
translated from the fourth Italian edition, which has appeared
since the publication of the English translation of Vols. I. and II.
This edition, in which the third and fourth volumes have
been enlarged and corrected in places by Professor Luciaui, wras
brought out in 1913 — on which occasion a commemorative medal
and an album containing the autographs of almost all the world's
most eminent physiologists were presented to the Author.
The English translation of the preceding volumes was edited
by Dr. M. Camis, but as he was unable to act again in this
capacity the Editorship of the present volume has been under-
taken by Dr. Gordon Holmes.
LONDON, 1914.
CONTENTS
CHAPTER I
PAGE
GENERAL PHYSIOLOGY OF MUSCLE . . . . .1
1. Skeletal muscles ; excitability and the conditions which regulate
it. 2. Curves of muscular contraction. 3. Theory of contraction in
tetanus ; the muscle sound. 4. Propagation of excitatory wave along
the muscle on exciting with induced or constant currents. 5. Minute
structure of striated muscle fibres : changes during contraction. 6.
Muscular tone,contracture, and capacity of muscle for active elongation.
7. Chemical composition of muscle in rest and activity. 8. Metabolism
in muscle and sources of the energy developed. 9. Muscular work and
muscular energy. 10. Heat production in muscle. 11. Electrical
changes during rest and activity. 12. Origin of muscular activity.
Bibliography.
CHAPTER II
MECHANICS OF LOCOMOTOR APPARATUS . . . .96
1. General remarks on the structure of the bones and their articula-
tions. 2. Form, attachments, and mechanics of muscles in relation to
bones. 3. Line and centre of gravity of the body in different postures.
4. Mechanics of equilibration in different postures. 5. Movements of
the body in walking. 6. Movements of the body in running. 7. Move-
ments of the body in swimming. Bibliography.
CHAPTER III
PHONATION AND ARTICULATION . . . . .129
1. General observations on the fundamental characters of sounds,
and their formation by different musical instruments. 2. Structure
of larynx as a musical instrument ; functions of laryngeal muscles.
vii
viii PHYSIOLOGY
PAGE
3. Nerves and centres of phonation. 4. Mechanical conditions for the
production of laryngeal sounds ; function of different parts of the
phonatory system. 5. Principal characteristics of the singing voice.
6. Difficulties and natural imperfections of singing. 7. The vowel
system in phonetic language. 8. Theory of physical nature of vowel
tones. 9. System of semivowels or sounding consonants, middle conso-
nants, and mute consonants. 10. Composition of syllables and words.
11. Writing, or graphic language. Bibliography.
CHAPTER IV
GENERAL PHYSIOLOGY OF THE NERVOUS SYSTEM . .175
1. Structural elements of the nervous system. Theory of inde-
pendent neurones, or continuity of neuro-fibrils. 2. Conditions, laws,
and phenomena of conduction in nerve. 3. Rate of conductivity :
diphasic character of the impulse arousing it. 4. Metabolism of nerve :
electromotive phenomena during rest and excitation ; demarcation
current, action current. 5. Excitation of nerve. Natural stimuli and
artificial (chemical, mechanical, electrical) stimuli. 6. Factors in life
and death of nerve : conditions of excitability. 7. Polar effects of
constant current (electrotonus) : correlative changes in excitability and
conductivity. 8. Excitatory action of electrical currents. Laws of
excitation. 9. Theories as to origin of neural activity. 10. General
functions of nerve-centres. Ganglion cells and central fibrillary net-
work. Bibliography.
CHAPTER V
SPINAL CORD AND NERVES. . . .278
1. Grey and white matter of the spinal cord. 2. Extra- and intra-
spinal nerve-cells ; their connections with the root-fibres and tracts
which make up the spinal columns. 3. Spinal roots. Bell-Magendie
law of localisation of sensory and motor tracts. Waller's law of
degeneration after section. 4. Functional relations between afferent
and efferent roots. 5. Segmental arrangement of spinal roots. 6.
Reflex activity of segments of cord ; shock after section of cord. 7.
Short and long spinal reflexes ; laws of reflex spread. 8. Genesis of
spinal reflexes ; central factors that inhibit or promote them. 9. Tonic
and automatic functions of spinal cord ; " knee-jerk " or patellar reflex.
10. Trophic functions of spinal cord. 11. Sensory functions and
Pfliiger's " spinal soul." 12. Spinal cord an instrument of the brain ;
spino-cerebral and cerebro-spinal paths of conduction. 13. Localisation
of principal spinal centres ; phenomena of spinal deficiency (dogs with
amputated cord, Goltz). Bibliography.
CONTENTS ix
CHAPTER VI
PAGE
SYMPATHETIC SYSTEM ...... 359
1. Anatomy and histology of fibres and ganglia of sympathetic
system. 2. Peripheral distribution of sympathetic system to the
organs which it innervates. 3. Physiological arrangement of con-
stituent parts of sympathetic system ; origin and course of efferent
iibres. 4. Origin and course of afferent fibres, o. Function of peripheral
ganglia. Bibliography.
CHAPTER VII
THE MEDULLA OBLONGATA AND CEREBRAL NERVES . . 380
1. General anatomy of the brain : the medulla oblongata. 2. Motor
functions of hypoglossus nerve. 3. Vago- accessory group ; motor
functions of eleventh nerve. 4. Different functions of vagus nerve.
5. The glosso-pharyngeal exclusively a nerve of taste. 6. Functions of
the facial and acoustic nerves. 7. Functions of the oculomotor and
trigeminal nerves. 8. The medulla oblongata as a motor centre. 9.
The medulla oblongata as the central organ of locomotion and posture.
10. The medulla oblongata as a sensory centre. Bibliography.
CHAPTER VIII
THE HIND-BRAIN . . . . ... .419
1. Anatomy of hind-brain : ati'erent and efferent tracts of the
three cerebellar peduncles. 2. Preliminary observations on cerebellar
functions. 3. Dynamic phenomena immediately incident on removal
of cerebellum. 4. Cerebellar ataxy in dogs and monkeys after removal
of half the cerebellum. 5. Cerebellar ataxy after total removal of
cerebellum. 6. Cerebellar ataxy. 7. The cerebellum as the centre of
equilibrium ; 8. And the co-ordinating organ of voluntary movements-;
9. And the organ of subconscious sensations, exercising constant
reinforcing action upon the other nerve-centres. 10. Localisation of
cerebellar 'functions. Bibliography.
CHAPTER IX
MID-BRAIN AND THALAMENCEPHALON . . . .486
1. General structure of the mesencephalon. 2. The thalamen-
cephalon. 3. Effects of total extirpation of fore-, inter-, and mid-
brain in fishes ; 4. In amphibia ; 5. In birds ; 6. In mammals. 7.
Effects of stimulating the mesencephalon. 8. Effects of extirpating
the corpora quadrigemina alone. 9. Effects of dividing the whole or
half the brain stem at level of the mid-brain. 10. Effects of incom-
plete or total removal of optic thalami. Bibliography.
x PHYSIOLOGY
CHAPTER X
PAGE
THE FORE-BRAIN . . . . .526
1. General anatomy of telencephalon. 2. Structure of the cerebral
cortex or pallium. 3. History of cerebral localisation. 4. Excitable
zone of the cerebral cortex ; localisation in dog, monkey, man. 5.
Physiological analysis of motor reactions of cerebral cortex. 6. Inhibi-
tory reactions. 7. Organic reactions of cortical origin. 8. Epilepsy
from cortical excitation. 9. The sensory-motor area, deduced from
effects of partial or total destruction of excitable cortex. 10. Functions
of basal ganglia or corpora striata (caudate and lenticular nuclei).
11. Visual area. 12. Auditory area. 13. Olfactory and gustatory
areas. 14. Association areas ; division of cortex into thirty-six areas,
according to Flechsig's embryological method. 15. Physiological analysis
of speech disorders of cerebral origin. 16. General theory of the
psycho- physical functions of the brain. Bibliography.
INDEX OF SUBJECTS . . . . . .637
INDEX OF AUTHORS 651
EEEATA
Page 24, par. 4, line 5, for " idea- muscular" read " idio-muscular."
,, 38, ,, 3, ,, 6, for " zanthine, hypozanthine " read " xanthine, hypo-
xanthine."
,, 102, ,, 3, ,, 5, for " hypoglossus " read " hyoglossus. "
,, 130, ,, 4, ,, 6, for "phonation (speech) " read "phonation (voice)."
,, 144, ,, 2, ,, 14, for "pitch " read "timbre."
,, 345, Fig. 192, for "dorsal" read "thoracic vertebra."
,, 349, ,, 5, ,, 2, for "controlateral" read "contralateral."
,, 510, ,, 3, ,, 3, for " Macacus rheus" read " Macacus rhesus. "
,, 514, ,, 5, ,, 1, for " opistothonus " read " opisthotonus."
CHAPTEE I
GENERAL PHYSIOLOGY OF MUSCLE
CONTENTS. — 1. Skeletal muscles; excitability and the conditions which
regulate it. 2. Curves of muscular contraction. 3. Theory of contraction in
tetanus ; the muscle sound. 4. Propagation of excitatory wave along the muscle
on exciting witli induced or constant currents. 5. Minute structure of striated
muscle fibres ; changes during contraction. 6. Muscular tone, contracture, and
capacity of muscle for active elongation. 7. Chemical composition of muscle in
rest and activity. 8. Metabolism in muscle and sources of the energy developed.
9. Muscular work and muscular energy. 10. Heat production in muscle.
11. Electrical changes during rest and activity. 12. Origin of muscular activity.
Bibliography.
FROM the physiological standpoint the higher animal organism
may be treated as a system of blood-forming organs, at the service
of a sensory-motor system. The first of these — the vegetative or
involuntary system — subserves the internal life of the body, and
its function is to prepare and keep approximately constant the
mass and constituents of the blood and lymph which provide the
common nutriment : the second — the organic or voluntary system-
subserves the phenomena of external life, and maintains and regu-
lates the relations between the organism and its environment.
But this distinction, proposed by Xavier Bichat, has little
intrinsic value, however useful it may be in the classification of
functions. The two systems do not constitute two separate
organisms, like the two primitive layers of the blastoderm, but
form a single complex indivisible organism, in which the specific
functions of both systems are sharply differentiated and localised.
Bones, tendons, and other forms of connective tissue participate
in the structure of the organs and mechanisms of animal life, and
although they remain passive during the activity of the muscles
and nervous system they make the functions of the latter possible,
and are thus important constituents of the sensory-motor system.
On the other hand motor and sensory elements contribute to
the structure of the organs and systems of vegetative life ; among
the former are amoeboid cells, ciliated epithelia and muscle
fibres, among the latter not only the nerve plexuses of the
VOL. in 1 B
2 PHYSIOLOGY CHAP.
sympathetic, but also the nerve-paths and centres of the cerebro-
spinal system.
Nevertheless the muscular and nervous elements which play
a direct part in the functions of vegetative life have usually
certain morphological and functional characters which distinguish
them from those which make up the organs of animal life, and
regulate the relations of the organism with the external world :—
(a) Voluntary or skeletal muscles are almost always striated ;
involuntary muscles, i.e. those of vegetative life, are almost always
non-striated.
(&) The former are controlled by the will, and only come into
play in response to nervous impulses ; the latter are nearly always
independent of the will, and may even function independently
of the central and peripheral nervous systems.
(c) The voluntary muscles consist of long fibres, grouped into
large masses, each of which is an anatomical unit ; the involuntary
fibres, which are not grouped into separate muscles, almost always
form smooth layers that line vessels or tubes, or constitute sheaths
that surround certain special cavities.
(f/) Finally (and this appears the most important), the first
are almost always skeletal muscles, attached by tendons to bony
levers, by which they can lift weights and overcome resistance,
i.e. perform actual mechanical work ; the second, on the con-
trary, are nearly all visceral muscles, and perform work that is
entirely confined to the interior of the body.
The nerves that control the involuntary system, again, present
certain characters which distinguish them from those that
innervate the voluntary muscles. The latter consist of medullated
fibres which come directly from the spinal roots ; the former are
exclusively non-medullated, and come principally from the sym-
pathetic system, and make at the periphery an exceedingly fine
fibrillary network which surrounds the separate muscle cells.
I. The skeletal muscles constitute the principal mass of the
body. Each muscle is an anatomical unit, a separate organ,
which can assume the most various shapes and sizes, but usually
consists of an elongated mass provided with tendons by which
it is attached to the skeleton. Each muscle consists of fibres
which are generally arranged parallel to its long axis, and converge
more or less towards the tendinous attachments. The muscle
fibres are united into bundles of varying size by connective
tissue, which is connected with the sheath or perimysium that
surrounds the whole muscle ; the blood and lymph vessels and
the nerves run through this connective tissue.
The length and the diameter of the muscle fibres vary con-
siderably. On an average, the length does not exceed 30-40 mm.,
but according to some authors it may reach 30 cm. The diameter
varies considerably even in the same muscle, and still more in
i GENERAL PHYSIOLOGY OF MUSCLE 3
different muscles, as it ranges from O'l to O'Ol mm. The fibres are
cylindrical or prismatic in form, with rounded angles and conical
ends. They consist of a striated substance of soft consistency
(the structure of which we shall presently examine) enclosed in
a tubular, apparently homogeneous elastic sheath, called the
sarcolemma; this is continued at both ends of the fibre into
connective tissue fibrils, which join the tendon or the septa of
the perirnysium.
The muscle fibres alone become active when the muscle
contracts ; the sarcolemma, the connective tissue of the perimysium
and its intermuscular septa, and the tendons remain passive.
During contraction each fibre pulls upon the tendon, either
directly or by means of the interfascicular connective tissue
which is continued into the tendon.
Each muscle has rnedullated and non-medullated nerve fibres ;
the former innervate its fibres, the latter the walls of the blood-
vessels : every muscle fibre is provided with at least one nerve
fibre, which usually forms an end-plate near its middle.
Under normal conditions the skeletal muscles are thrown
into activity by their nerves, and after section of these all move-
ment of the muscle is arrested ; this indicates that neither the
muscles nor the nerves by which they are innervated are capable
of automatic activity. But after dividing the nerve and exposing
the muscle an effective mechanical, thermal, chemical or electrical
stimulus, applied either to the nerve or directly to the muscle,
evokes a contraction of the latter in response ; so that both
nerves, when severed from their centre, and voluntary muscles
manifest irritability or excitability, i.e. a power of reacting by an
explosion of energy to external impulses (Vol. I. p. 44). The
active reaction, or contraction, of the muscle is expressed in its
rapid change of form and displacement ; excitation of the nerve,
on the contrary, is not accompanied by any direct visible change,
and consists solely, as we shall see, in a molecular vibration, by
which the excitatory impulse is transmitted to the muscle.
Since the natural excitation of a muscle is always the effect
of an excitation through its nerve, it is legitimate to assume that
the reaction produced artificially by its direct stimulation is also
due to stimulation of the nerve fibres that run between the
muscle bundles. Many authors, from Borelli and Willis onwards,
have regarded the muscles as the passive instruments of the
nerves, though A. Haller maintained the opposite view in his
famous theory of muscular irritability, which was based on
fallacious arguments (Vol. I. p. 299). Although Haller's view
has now only an historical interest, it is instructive to sum up
briefly the most striking arguments that were, and still might be,
adduced in support of the theory of direct or autonomous excita-
bility of the voluntary muscles.
4 PHYSIOLOGY CHAP.
In 1841, Longet resorted to a very simple method of deciding
the question, by cutting the nerves to a limb of a mammal, and
testing the direct and indirect excitability of its muscles, at
various intervals after the operation. He found that the nerves
lost their excitability to all stimuli (mechanical, chemical,
electrical) after the fourth day ; while the muscles to which these
nerves were distributed reacted to direct stimulation as long as
twelve weeks after the operation. To this argument in favour
of autonomous muscular excitability it was objected that the
degeneration and loss of excitability in the nerve is propagated in
a centrifugal direction, i.e. from the point of section towards the
nerve-endings, and that the end-plates might consequently retain
their excitability after total degeneration of the corresponding
fibres. Microscopical investigation, however, shows that the small
muscular nerves are already altered eight to ten days after the
section, and it would therefore be illogical to suppose that the
end-plates can remain intact several months longer. Clinical ob-
servations confirm this fact ; the muscles of the face, for instance,
preserve their direct excitability several years after the facial
nerve has been paralysed (C. Richet).
Another more effective method of showing that muscular
excitability is independent of the corresponding nerves was dis-
covered in 1850 by Cl. Bernard, and almost simultaneously by
Ko'lliker. The strongest stimuli applied to the nerves of
animals paralysed by curare are unable to excite any contraction
of the skeletal muscles ; but the muscles preserve their direct
excitability. Curare neither paralyses the sensory nerves nor
the nerve-centres, its paralysing action being limited (except
with excessive doses) to the motor nerve -endings. In fact, if
the sciatic nerve of a frog is exposed on the right side, and that
leg, leaving out the sciatic, is ligatured, and curare is then injected
under the skin of the back, the right leg reacts when its sciatic
nerve is stimulated ; but when the left sciatic is stimulated no
reaction of the muscles on that side is obtained because the poison
has been circulating through them, while there are reflex move-
ments from the right leg. The section of a motor nerve abolishes
excitability from the point of section to the periphery, but the
toxic action of curare begins by paralysing the motor end-plates,
and then extends centripetally along the nerve. Curare does not
therefore alter the excitability of the muscle perceptibly (at any
rate in small doses and in the early stages of its action), but it
paralyses motor nerves, by abolishing the conductivity of the motor
end-plates, and thus interrupts the normal link between the nerve
and its muscle.
A simpler and no less conclusive argument was brought
forward by Kiihne (1859). He observed that the sartorius muscle
of the frog has no nerve fibres near its end, for about ^ of its
i GENERAL PHYSIOLOGY OF MUSCLE 5
total length. Yet the muscle reacts by a twitch if it is stimulated
by pinching it with forceps at a point at which there are no nerve
fibres.
Another sound argument for the autonomous excitability of
muscle is the so-called idio- muscular contraction observed by
Schiff. This is seen in fatigued or degenerating muscle, in which
conductivity is lowered. On stroking the exposed muscle obliquely
to the direction of its fibres with a blunt object, or tapping it
with a scalpel, a ridge of contraction appears at the point of
contact. This is obviously a local muscular reaction, independent
of the nerve.
These direct arguments for the independent excitability of
voluntary muscles are confirmed by observations which demonstrate
the automatic and reflex excitability of involuntary muscle fibres.
(See Vol. I. pp. 305-12.)
Muscular excitability, independent of the nerves, is controlled
by the circulation which supplies the muscle with the nutrient
material and oxygen indispensable to its metabolism, and removes
the waste products as fast as these accumulate. Nicolas Stensen
(1687) first observed that after tying the abdominal aorta in
mammals paralysis of the posterior limbs rapidly set in, and dis-
appeared again if the artery were reopened after a short period.
In this experiment, however, the paralysis depends not only on the
fall of muscular excitability, but also on the anaemia of the lumbar
cord which is supplied by the aorta (Schiffer). If instead of the
aorta the iliac and crural arteries of one limb are tied, the ex-
citability of the muscles cut off from the .circulation survives for
many hours (Brown -Sequard) ; as the vitality of the muscle
diminishes it shortens, and finally becomes rigid (rigor mortis).
If the circulation is re-established before the onset of complete
rigor, the excitability of the muscles may be recovered.
Brown-Sequard demonstrated by a long series of experiments
that, after death, excitability persists for a longer or shorter time
in different muscles of the same animal ; that, generally speaking,
it survives longer if the external temperature is low, although the
contrary has been affirmed ; and that the longer the muscles pre-
serve their excitability after death, the longer are they capable
of recovering it on the artificial circulation of arterial blood.
Claude Bernard stated that during muscular contraction in
the living animal the blood flowing away from the muscles is
highly venous. Ludwig further observed that during tetanisation
of the muscles of any limb, by stimulation of its nerves, the flow
of blood from the muscle was accelerated, owing to the active
dilatation of the vessels. Chauveau noted an acceleration of the
circulation in the masticator muscles of calves during mastication,
which was due not only to nervous influence but also to the active
dilatation of the muscular vessels, and to the impetus given to the
6 PHYSIOLOGY CHAR
venous stream by each contraction of the muscles. But in curar-
ised animals also direct excitation of the muscles dilates the
vessels and may produce minute capillary extravasations owing to
excess of tension.
The nutrition of the muscles, and indirectly their excitability,
also depend on the trophic influence continually exercised upon
them by the nervous system. After cutting the motor nerves the
muscles degenerate as well as the peripheral end of the nerves
severed from their centre. Their excitability falls in the first three
or four days, but then rises to mechanical and galvanic excitation
(Erb's reaction of degeneration^), while it decreases still further to
faradic stimulation; after seven weeks muscular excitability is much
reduced, and within six to seven mouths it has disappeared. During
the first week after section fibrillary contractions are observed in
the degenerating muscle, which are due to the excitation of the
contractile elements by intrinsic chemical changes (Schiff).
Use and disuse again have great influence upon the nutrition,
and thus upon the excitability and work-capacity, of muscle. It
is a common observation that exercise develops and strengthens
the muscles, while disuse and a sedentary life render them weak
and flabby. Absolute enforced rest causes the muscles in time to
degenerate and atrophy.
II. The physiology of muscle was not really known till after
the ingenious researches of E. Weber (1846) on the relations
between contractility and elasticity ; and till Helinholtz (1850-52)
applied the graphic method to its study by means of his myograpli,
which traces the entire curve of a muscular contraction (myogram)
and indicates the exact moment of the application of the stimulus
to the nerve or to the muscle.
A Myograpli is an apparatus designed to show by a tracing on a smoked
plate or revolving cylinder the changes in length (or thickness) which a
muscle undergoes during excitation, i.e. the active state into which it is
thrown as the effect of .stimulation.
There are a great variety of these instruments, invented by the different
authors who have occupied themselves with the mechanical functions of the
muscles. One of the oldest is that of Pfliiger, which again is only a simpli-
fication of the original rnyograph devised by Helmholtz. Pfliiger's apparatus
(Fig. 1) consists of an arm LL which moves round a horizontal axis, and can
be brought into equilibrium by the counterpoise C. The other end of the arm
is fitted witli a lever, which also rotates round an axis and ends in a metal
point P, which writes on a moving smoked plate or drum that can be rotated
at varying speeds. The writing-point is kept in contact with the recording
surface by a small weight or spring, but can be drawn back by a thread
fastened to the wheel c. A freshly excised muscle is clamped at the top, and
attached below by a thread and hook to the middle of the lever. Below the
point at which the muscle is attached is a small scale-pin />, on which different
weights can be placed to examine the influence of different loading on the
contractility of the muscle. The latter is kept moist in a glass chamber con-
taining a little wet filter paper.
Instruments of this class give an imperfect record because the myograms
GENEEAL PHYSIOLOGY OF MUSCLE
do not correspond with the true movements of the excited muscle. Owing,
to the weight of the lever and the distance from the axis of the load appliec
to the muscle, tin- entire mass
is accelerated on the rapid con-
traction of the muscle, and the
curve altered, because the ten-
sion in the muscle due to the
load is greater at first, and then
gradually diminishes — instead
of being constant. To avoid this
the mass raised by the muscle
and the height to which it is
lifted must be lessened, so as
to obviate changes of tension
during the contraction. This
is done by using a very light-
lever, and making the height
to which the weight is raised
as small as possible by attach-
ing it, close to the fulcrum, to
a thread which passes over a
wheel fixed at the axis of the
lever. By this arrangement
the acceleration imparted to
the weight becomes negligible,
no matter how rapid and ample
the movement of the lever, and
the passive tension of the muscle
remains constant throughout
the experiment.
Fig. 2 (which is only a modi-
FIG. 1.— Pfliiger's myograph. Explanation in text.
fication of Waller's myograph) gives one of many that have been constructed
on this principle. It is adapted to show on the same muscle the effects
FIG. 2. — Myograph for comparing direct and indirect excitation on the same muscle — loaded or
unloaded. (Luciani.) The frog's gastrocnemius muscle is fixed horizontally over the surface
nf the mercury contained in a hollow of the cork plate. It is connected by a thread with a
jointed lever II, the axis of which carries a small wheel ; a thread passes round this to hold
the scale-pan for the weight ji, which is to load the muscle. The vertical arm of the aluminium
lever, cm which the muscle pulls directly, works the movements of the much longer horizontal
arm, which consists of a straw ending in a writing-point, by which the movement is traced
on a revolving cylinder. The relations between the two arms can be easily adjusted. The
electrodes from the secondary coil of an induction apparatus can be applied by a Pohl's
commutator without cross-wires to the muscle or the nerve, according as the bridge is thrown
over to the left M, or right N.
not only of direct and indirect excitation, but also of different weights
applied to the muscle, from the minimal load of a fine straw employed as
8
PHYSIOLOGY
CHAP.
the lever to progressively increasing weights suspended from the thread and
wheel at the axis.
The errors inseparable from the use of a lever (inertia, etc.) have more
recently been eliminated by employing the photographic method (Blix, 1895 ;
Brodie and Richardson, 1897 ; Lucas,
1903, etc.) The principle is that the
contracting muscle deflects a small
I Te^V § IL£ — ^"X. mirror, from which a beam of light is
reflected on to a travelling sensitive
surface so that the movement of con-
traction is photographed.
The myograms best suited for
analysis and study are those ob-
tained from " nerve -muscle pre-
parations " of the frog or other
Fio. 3.— Frog's nerve -muscle preparation. Cold-blooded animal, ill which the
muscle; n, sciatic excitability of the nerves and
t.a.
nerve, with all the branches cut except
that to the muscle ; /, femur ; p, clamp to
fix upper end of muscle with femur ; (.a.,
tenclo Achillis with hook to attach lower
end of muscle to myograph ; c.s/i., extreme
end of spinal cord.
muscles lasts much longer than
in warm-blooded animals (Fig. 3).
Whatever the nature of the
stimulus applied to the muscle or
its nerve, the contraction which is recorded by the myograph may
assume the form of a twitch or of tetanus. The twitch is the
simplest and most rapid form of muscular contraction ; tetanus is
a more complex and persistent contraction which results from the
fusion of a greater or less number of twitches in rapid succession.
Fig. 4 gives the myogram of a simple twitch, obtained on the
momentary stimulation of the frog's gastrocneinius by a break
shock from the secondary coil of an induction apparatus. In
order to determine the exact moment at which the shock is
thrown into the muscle the
recording cylinder itself, at a
certain point of its revolution,
is arranged to open a contact
(Helmholtz), or else an electric
signal which is interposed in
the circuit marks the exact
moment of stimulation upon
the recording surface (Marey
and others).
In Fig. 4 three different
periods can be distinguished:—
(a) The interval a b, in
which no visible change takes place in the muscle ; this is the
time lost between the application of the stimulus and the com-
mencement of the contraction, which Helmholtz termed the period
of latent excitation or latent period.
(b) The interval b c, during which the muscle shortens, at first
PIG. 4. — Myogram of contraction of frog's gastm-
cnemius. Time tracing from tuning-fork, giving
10U vibrations per second, n, li, latent period ;
li, <•, phase of contract-ion ; <•, d, phase of re-
laxation.
GENERAL PHYSIOLOGY OF MUSCLE 9
slowly, then more rapidly, then more slowly again, which repre-
sents the contraction period.
(c) The interval c d, during which the muscle relaxes and
lengthens, slowly at first, then more rapidly, then again slowly,
which is the expansion or elongation period.
According to Helmholtz' first results the latent period in the
voluntary muscles of the frog is about O'Ol sec., but later work has
shown it to be much shorter. According to Yeo it is 0'005 sec. ;
according to Burdou-Sanderson 0'0025 sec. ; lastly, according to
Tigerstedt (who made many comparative experiments on the
frog's gastrocnemius under a variety of conditions) it varies between
0-004 to 0-006 sec,, but is generally (41 per cent) 0'005 sec.
From the theoretical standpoint it is more than probable that
there is really no appreciable interval between the direct stimula-
tion of a muscle and the commencement of contraction, and that
the apparent latency of excitation depends on the fact that the
contraction does not begin simultaneously throughout the mass of
the muscle, but advances gradually like a wave, so that the fibres
which first contract pull upon, and passively extend, the fibres
that have not yet contracted, and thus nullify the mechanical
effect. It is only when, with the advance of the contraction wave,
the active shortening of the mass of muscle exceeds its passive
elongation that the lever attached to the muscle begins to rise
from the abscissa (Gad).
Apart from the latent period, the active reaction or excitation
of the muscle consists in a diphasic process, with distinct phases
of contraction and of expansion, which may vary considerably
under different circumstances. For instance :—
(it) Tracings of a muscle twitch vary considerably in the
duration or velocity of the total movement and that of the two
separate phases, according to the character of the muscles which
are under observation. As regards speed of reaction, there is an
enormous difference between the plain muscles, which react so
slowly that both phases are visible to the eye, and the striated
muscles, which react so quickly that the graphic method is indis-
pensable for their demonstration. The cardiac muscle cells come
midway as regards rate of response between the unstriated visceral
and the striated skeletal muscles. The duration of the contraction
of skeletal muscles is variable, not only in the muscles of different
animals, but even in the different muscles of the same animal.
Contraction is most rapid in insects, less rapid in birds, slower
still in mammals (about O'l sec. on an average), slowest of all in
the cold-blooded animals, especially in the tortoise.
Eauvier (1874) first noted that in certain birds and mammals
two kinds of muscles can be distinguished, red and pale, and that
the latter contract more rapidly than the former, an important
fact subsequently confirmed by other experimenters.
10 PHYSIOLOGY CHAP.
According to Griitzner (1883) each muscle contains rapidly
contracting and slowly contracting fibres, which cannot always be
distinguished by their colour. Speaking generally, he holds that
the latter, which are less excitable and less easily fatigued, are
richer in sarcoplasm, darker and thinner ; the former, on the
contrary, are more excitable and more easily fatigued, less rich in
sarcoplasm, lighter and thicker. Easier (1904-5), in Griitzner's
laboratory, afterwards confirmed and extended these researches.
Paukul (1904), who examined the forms of twitch from almost
every muscle of the rabbit, came to the conclusion that the
different modes of contraction depend on the arrangement of the
muscle fibrils and the intervening sarcoplasm ; those muscles in
which fibrils lie uniformly and are surrounded by little sarcoplasm
contract rapidly, while those in which the fibrils are arranged in
FIG. 5. — Influence of temperature on amplitude of muscular contraction. (A. D. Waller.) 1, con-
traction of normal gastrocnemius ; 2, of same muscle, slightly cooled ; 3, of same muscle, much
cooled.
groups and separated by a large amount of sarcoplasm contract
more slowly.
(6) Temperature, either higher or lower than the normal, has
a marked influence upon the course of the muscular contraction.
Cooling always lengthens the contraction, and raises its height
when the degree of cooling is moderated, but lowers it if more
marked (Fig. 5). Warming constantly accelerates contraction
and increases its height when moderate in degree, but lowers it
when more pronounced. Gad and Heymans found the maximum
height of contraction at 30° C. It is diminished as tbe tempera-
ture falls to 19° C, and subsequently rises again at 0° C.
Patrizi examined muscular contraction in the marmot, both
in the hibernating and in the waking state, which are, of course,
distinguished by great differences of temperature. He found that
contraction is about three times more rapid when the animal is
awake than in hibernation ; and determined the latent period and
duration of the different phases of the twitch, and the stimulation
frequency required to produce tetanus, in both these states, that is,
with both the high and the low body-temperature.
i GENERAL PHYSIOLOGY OF MUSCLE 11
While cold diminishes muscular excitability and renders the
muscle less easily fatigued and more resistent, heat, after a brief
rise of excitability, leads to easy exhaustion. When the rise of
temperature exceeds 40-50° 0. the muscle enters into thermal rigor,
in which it gives its maximal contraction, and does not relax again.
(c) The duration and form of the muscle twitch also depend on
the degree of fatigue. If a series of twitches from a frog's muscle,
uniformly loaded and excited at equal intervals (1-2 sees.), with
uniform shocks from make or break induction currents are recorded
on the drum of the myograph, a fatigue curve will be obtained which
shows a gradual retardation and weakening of muscular activity,
preceded by a short phase of augmentation. Fig. 6 shows that in
a preliminary period, consisting of some ten twitches, the tracings
rise in height, and the duration of both contraction and elongation
is lengthened. In a second much longer period the height drops,
I ;. ti.— Curve of fatigue, with direct stimulation of frog's gastrocnemius. (A. D. Waller.) Tracing
of 125 maximal contractions at H sees, interval. The experiment was stopped before the muscle
became fully exhausted.
while the duration of both phases increases, but particularly that
of relaxation.
Kronecker (1871) showed that when a frog's muscle, excited
at regular intervals with maximal induction shocks, is loaded
only at the moment at which it commences its contraction (after
loading}, the apex of the twitches forms a straight line, which
drops more rapidly towards the abscissa in proportion as the
interval between the single stimulations diminishes. In repro-
ducing Kronecker's experimental conditions it is necessary first
to test the excitability of the muscle in order to find the least
stimulus that will produce a maximal effect ; next, the single
stimuli must succeed each other at long intervals, so that the
muscle shall not be excited again before the phase of relaxation is
fully completed, which takes longer and longer as the fatigue
increases. The apparent rise of activity, often seen at the com-
mencement of muscular fatigue, is probably due to the fact that,
owing to the lengthening of the phase of relaxation, the muscle
receives the next shock before it has completely relaxed. In
this case each new excitation summates with the residue of the
previous contraction, and the level of the myogram rises in conse-
quence (Fr. W. Frohlich, 1905).
12
PHYSIOLOGY
CHAP.
The study of fatigue phenomena in muscle is simplified and
made more complete if, instead of sending in the excitations at
regular intervals, the muscle is stimulated by a make induction
shock directly it has relaxed. The apparatus can be arranged so
that the contraction of the muscle breaks the exciting circuit, and
its relaxation closes it again. The muscle thus contracts and
relaxes continuously (Wundt, 1858 ; Novi, 1879).
Fig. 7 shows the curve of muscular fatigue passing into
complete exhaustion. It exhibits the initial phases that are to
be seen in Waller's incomplete curve, followed by a much longer
Km. 7. — Complete tracing of muscular fatigue from frog's gastrocnemins ; series of successive
contractions which vary in frequency with the varying duration of the contraction. (I. Novi.)
Lines 1, 2, 3, 4 represent successive parts of one tracing, a, b, first, very brief phase con-
sisting of extremely rapid contractions of increasing height ; b, <:, second phase, four to five
times longer, rapid contractions decreasing in height ; c, d, third phase, less rapid contractions,
approximately equal in height ; </, c, fourth phase, longer than preceding, contractions becoming
slower and higher ; e, f, fifth phase, the longest of all, contractions decrease regularly in height,
and become increasingly slower; x, y, slowest of all ; y, /, minimum height, contractions
gradually die away.
final phase, in which the height of the twitches regularly decreases
in a straight line, as shown by Kronecker.
By Novi's method it is easier to analyse the changes in the
functions of muscle which are due to fatigue, and the variations
of the curve of fatigue with variations of temperature, and under
the influence of different drugs and poisons.
When fatigue has been pushed to complete exhaustion by
very frequent stimulation the muscle often fails to regain its
normal length, and remains more or less contracted, thus approxi-
mating to the state of rigor that signalises its death.
If the muscle is left to itself for a certain time after its
excitability is so exhausted that it no longer reacts to stimuli,
it gradually recovers, i.e. regains its excitability. In the living
i GENEEAL PHYSIOLOGY OF MUSCLE 13
body the tired muscle rapidly recovers with rest, owing to the
blood circulation ; but excised muscle, too, is capable of a partial
restoration, although it is cut off from the circulating tissue fluids.
Fatigue is the effect of two factors which act simultaneously
upon contractile protoplasm — the consumption of the dynamogenic
materials of muscle, and the accumulation of waste matters or
decomposition products. Recovery depends on the supply of
further nutritive material and removal of the waste products, as
we shall presently see in discussing muscular metabolism.
(d~) The height of the twitch also depends on the form or
strength of the stimulus. It is advisable in studying these
relations to employ the make or break shocks of an induced
current, which can be easily graduated. If a muscle is rhythmic-
ally excited by break shocks of gradually increasing strength,
it begins to respond only when the stimulus reaches a certain
intensity, the so-called threshold of stimulation. If the exciting
current is then further strengthened, a series of contractions
result that increase in height, step by step, up to a certain point,
after which they no longer increase with the strength of the
stimulus. Stimulation is therefore distinguished as effective and
ineffective according as it produces or does not produce a reaction ;
effective stimuli, again, may be minimal, median, maximal, or
super -maximal. The gradation of the stimuli alters, moreover,
according as the muscle is directly or indirectly excited. When
the muscle is directly excited the interval between the minimal
and maximal stimulus is greater, but as this interval is very small
it requires only a slight increase of the stimulus above the threshold
to elicit a maximal contraction. The gradation of the response to
an increasing stimulus is not, therefore, easy to demonstrate.
Certain muscles, e.g. cardiac muscle, either do not respond at all
or respond to each shock by a maximal contraction — Bowditch's
Law of " all or nothing " (Vol. I. p. 318).
According to Fick's first researches (1862) on the gradation of
response to indirect stimulation of skeletal muscle, the increase
in height of the contractions is approximately proportional to the
increase in strength of the stimulus ; but Tigerstedt has shown,
with direct stimulation of curarised muscles, that with regular
increase in the strength of the current the contractions at first
increase rapidly, and afterwards more slowly, till they become
maximal. The ascending line of the contractions is thus not a
straight line but a hyperbola.
At the maximum height of the muscle twitch obtained on
exciting a fresh frog's muscle with a maximal or supermaximal
stimulus the muscle shortens by \ of its length, as measured in
the resting state.
(e) The height, duration, and form of the contraction are
considerably influenced by the load carried by the muscle, i.e.
14 PHYSIOLOGY CHAP.
the resistance it encounters during its contraction. Generally
speaking, it is said that the weight applied to the muscle impedes
contraction while it facilitates relaxation. It is further assumed
that a muscle which carries no load — i.e. is not influenced by
external resistance, as when it floats on mercury — shortens with
an induced shock, and remains contracted without resuming its
initial length. If this were accepted unconditionally it would be
in open contradiction with a number of experimental observations,
which prove that both contraction and relaxation are active states
of the muscle. Kaiser (1900) showed that if the frog's sartorius
muscle is carefully dissected out without pulling on it, and dipped
in olive oil before being placed on the mercury to minimise friction,
it responds to each shock of an induced - current by a single
diphasic contraction, i.e. after contracting it relaxes at its normal
rate. After the first indirect stimulation the muscle regularly
^D
FIG. 8.— Diagram of isotonic myograph. L, lever connected with the muscle at point A, traces the
movements with writing-point p on the recording surface. The weight P that pulls on the
muscle is fastened by a thread to a little wheel attached to axis « of the lever.
becomes longer than it was before ; but if the stimuli are
applied frequently the expansion is less complete — a muscle, for
instance, 35 mm. long in the initial resting state fails to attain
its original length, but becomes successively shorter by 1, 2, or
3 mm.
It may be said in general that the greater the load or the
resistance opposed to the contractile phase of muscular activity
the less is the shortening and the greater the degree of tension
in the muscle, so that shortening and muscular tension are in
inverse ratio. On stimulating a muscle clamped at both ends,
the tension can be increased to a maximum without any shortening ;
conversely, when a muscle, clamped at one end only and loaded
at the other with a small weight, is stimulated, it contracts
maximally with the least possible increase of tension. A. Fick
(1887) first analysed these two functions of muscular activity,
and devised a comparatively simple method by which it was
possible to a large extent to eliminate the alterations of tension,
while the curve of shortening was simultaneously recorded, or
vice versa to minimise the alterations in the length of the muscle
i GENERAL PHYSIOLOGY OF MUSCLE 15
and at the same time record the curve of muscular tension. To
the first he gave the name of isotonic, to the second of isometric
curves.
Isotonic curves are recorded with a very light lever, the weight being
applied near the fulcrum by a thread that runs over a wheel during the
contraction (Fig. R).
The free end of the muscle is attached by a hook and thread to a point of
the lever at greater or less distance from the fulcrum. The movements of
the muscle are magnified by the writing-point according as the muscle is
fixed nearer the fulcrum. Under these conditions the acceleration of the
weight is negligible, no matter what the amplitude and speed of the move-
ment, and the tension of the muscle remains approximately constant through-
out its contraction.
To obtain relatively perfect isometric curves, the shortening of the muscle
must be reduced to a minimum by causing its lower end to work against a
strong elastic resistance, and magnifying the excursion of the lever by a long
arm (Fig. 9). The muscle is fixed at its upper extremity, and is connected
by a long inextensible thread with a metal wheel, to which a steel spring
M
FIG. 9.— Diagram of isometric myograph. The muscle is directly connected with the wheel, which
carries the spring .V; by pressing on the supports this considerably reduces the rotary
movement A, although the latter is magnified by the long arm of the lever L which records it.
is attached, which rests on a support at its free end. When the muscle
pulls on the thread the wheel moves slightly round the axis and the spring is
stretched against the support. The least movement of the wheel is magnified
by a long light lever, the point of which traces a curve upon a rotating
drum that almost perfectly expresses the tension of the muscle during
excitation, but not its change of form.
Various isotonic and isometric myographs have been invented, but the
principle is the same as in Figs. 8 and 9.
When the tension of the muscle remains approximately constant
during the course of the contraction (isotonic] the height of the
latter generally increases with diminution of the load, at first
rapidly, then more slowly, i.e. not in proportion with the load,
while the work done by the muscle, calculated from the weight
multiplied by the height to which it is raised, increases within
certain limits with each increment of weight (Santesson).
There are, indeed, exceptions to this rule. According to the
observations originally made by Fick, and afterwards confirmed
by others, when the weight applied to the muscle is not great,
and particularly when an elastic resistance is opposed to the
muscle, so that its tension increases constantly during contraction,
16 PHYSIOLOGY CHAP.
the shortening is greater when the weight and the initial resist-
ance are increased. This paradoxical phenomenon is a specific
property of the substance of living muscle, and shows that the
sudden pull of the muscle and increase of tension during shortening
act as a stimulus on the contractile substance, and increases the
effect of the electrical stimulation.
With the isometric method the tension of the muscle pre-
vented from shortening is far greater in the excited than in the
resting state. Comparison of the curves of isotonic and isometric
contraction, obtained from the same muscle under uniform con-
ditions of stimulation, show that the two curves differ very little
at medium temperature. When, on the contrary, the temperature
of the atmosphere is lowered to about 5° C. the two tracings
present distinctive char-
acters. Fig. 10 plainly
shows that the isometric
curve reaches its maximum
more rapidly than the iso-
tonic curve, and that in
the former maximal tension
persists for a certain time,
while in the second it passes
suddenly from the height of
the contraction phase to the
FIG. 10.— Comparison of isotonic (a) and isometric (/-) phase of relaxation.
inyograms from the same muscle. (Gad.) The eor.iv.o-nn /"I QOJA cfnrliprl
isometric curve is reversed because in Gad's myo- \J.yw±) &LUI
graph the lever is pulled down instead of up by foe influence of the load
increasing tension of the muscle.
upon isometric curves by
submitting the muscle to sudden changes of tension during its
contraction. Such changes, whether a temporary or permanent
increase or decrease, always induce marked diminution of tension
in the muscle in a degree which depends not on the magnitude,
but on the abruptness of the change, and is more pronounced
the later the alteration in tension occurs in the contraction.
In the body these conditions of isotonia and isometria are, of
course, seldom realised. A certain amount of contraction is nearly
always needed to overcome the resistance that diminishes or
increases during the course of excitation. The muscles, in other
words, are almost always employed in carrying out an external
mechanical task under various conditions, which differ from the
experimental conditions of isotonia and isometria. The isometric
method is an analytic means of eliminating the complications of
changes of form and internal friction, so as to obtain the simpler
curve of the changes of tension or of longitudinal molecular attrac-
tion, which are the fundamental effects of muscular excitation.
III. The activity of skeletal muscle in the body differs in
another respect from that above described. Under natural
i GENEEAL PHYSIOLOGY OF MUSCLE 17
conditions the movements of our body are not the effects of
simple muscular contraction, due to isolated and instantaneous
stimulations, but almost invariably result from a series of rapidly
succeeding stimuli, which produce in the muscle the state of
permanent and apparently uniform contraction known as tetanus.
Volta (1792) was the first who recognised that frequently
repeated stimuli were able to produce persistent contraction in
muscle. Matteucci (1838) first termed this state of contraction
tetanus, and the interrupted currents which produce it, tetanising
currents. Helmholtz (1854) first demonstrated that tetanus of
the skeletal muscles is the effect of the summation and fusion of
a rapid succession of simple contractions.
On sending two shocks from an induced current into the
nerve of a muscle at very brief intervals, so that the second
stimulus falls 011 the muscle during the period of latent excitation,
the resulting curve does not differ from that produced by a single
shock if the current is maximal, but if, on the contrary, the
Fin. 11. — Diagrammatic superposition of two contractions. (Helmholtz.) The curves a b c and
</ i: / represent two distinct contractions excited by two shocks rr'. The curve a g h i k
represents the superposition and fusion of the two preceding, as if the contractions <l ef rose
from the abscissa line g i, and not from d /.
current is moderate or hardly effective, the height of the curve
is different. Accordingly, two shocks of medium strength act
in this case like a single maximal or supra -maximal stimulus,
showing that there is summation of the two excitations (Helm-
holtz). In the crab's muscles it is possible also to observe latent
summation of several shocks, each of which is ineffective in itself,
that is, incapable of producing any visible sign of excitation
(Richet).
If the interval between two stimuli is such that the second
induction shock falls on the muscle during the contraction
induced by the first, the second shock is superposed upon the
former, as if the muscle were at the moment of its application in
the natural state of rest (Helmholtz). In this case, accordingly,
the two contractions fuse into a single one of greater height and
duration (Fig. 11).
If the interval between the two stimulations is such that the
second contraction is sent in when the muscle is at the height of
the contraction produced by the first, the fusion of the two will be
maximal, i.e. almost double that of the simple twitch. This
VOL. in c
18 PHYSIOLOGY CHAP.
maximal effect of the fusion of the two contractions takes place
when the interval between the two shocks is about oV of a second
(Sewall and others).
Summation of contractions takes place not only with currents
of medium strength, but also with maximal or supra-maximal
stimulation. The maximal contraction of a muscle is therefore
not obtained with a single stimulation, however strong, but only
with repeated stimuli in rapid succession, owing to the summation
of excitation. The interpretation of this phenomenon will be
given later in speaking of Contracture.
When a series of stimuli act upon a muscle in rapid succession,
it reaches the maximum degree of% shortening, owing to summation
of the stimuli, and remains in the state of persistent contraction
known as tetanus so long as the stimuli act upon it. The minimal
•••.:*•••••. '-.. ':,;•••
-
•.-;' s
Fin. 12. —Comparison of tetanus curves from a red (;•) and pale (yi) muscle of rabbit. (Kroneckor
and Stirling.) At A both muscles were excited by ten induced shocks per second ; at B by
six shocks per second.
stimulation frequency necessary to produce complete tetanus
varies in the muscles of different animals. As a rule it is less
in proportion as the active phase of the muscular contraction is
slower. 12-30 stimuli per second suffice for frog muscles, while
20-30 are required for those of mammals. The red muscles of the
rabbit, according to Kronecker and Stirling, may be almost com-
pletely tetanised with 10 stimuli per second, while the pale muscles
of the same animal are only thrown into tetanus with 20-30
stimuli per second. With 6 stimuli per second the pale muscles
exhibit a series of almost wholly isolated contractions, while
the same frequency throws the red muscles into a tremulous
contraction closely resembling tetanus (Fig. 12).
All conditions that make muscular contraction slower, as
fatigue, fall of temperature, etc., diminish the stimulation
frequency necessary for complete tetanus. On the cessation of
the series of stimuli that induced tetanic contraction, the muscle
never resumes its original length, but remains a little shortened
in consequence of the fatigue and the abnormal changes which the
i GENERAL PHYSIOLOGY OF MUSCLE 1.9
contractile protoplasm has suffered. The degree of this residual
shortening is, of course, in definite relation with the duration of
the tetanus.
It follows from the theory of summation of contractions that
in tetanus the shortening of the muscle, and thus the work it is
able to accomplish, is greater than in a simple contraction. To
this rule there is, however, one exception ; according to von Frey
a lightly loaded muscle contracts equally both to a single shock,
and to a tetanisiug current.
The degree of shortening and the yield of work from the
tetanised muscle depend on the frequency and strength of the
tetanising current. When the stimulation frequency exceeds
300 per second, and the current is sufficiently weak, no tetanus
results (Harless, Heidenhain), or at most a single initial twitch
(Bernstein). In order to produce tetanus the current must be
strengthened ; this is due to the fact that after the first stimulation
the excitability of the muscle drops, and consequently it no longer
reacts to subsequent stimuli so long as these remain minimal.
According to Salomonson (1904), on the contrary, this is merely
a physical phenomenon.
The upper limit of the stimulation frequency that can produce
tetanus has not yet been ascertained. Bernstein obtained it with
an acoustic interrupter that sent 2000-3000 induction shocks into
the muscle per second : Kronecker with 20,000 shocks per second.
Tesla and d'Arsonval discovered that high frequency alternating
currents sufficiently intense to render a carbon filament in-
candescent fail to excite a muscle or nerve. While a constant
current of 5 milliamperes excites both at break and at make
of the circuit, an alternating current of 5 amperes, of high
frequency (about one million per second), produces no effect, motor
or sensory. By a special contrivance this current can be passed
through one or more persons and at the same time through a
series of incandescent lamps ; the lamps light up, while the
individuals included in the circuit feel neither sensation nor
motion. Eiuthoven (1900) subsequently demonstrated that it is
possible to evoke muscular contractions by means of indirect
stimulation, even with alternating currents of the highest frequency
(up to a million per second), provided the strength of the current
is enormously increased in proportion with its frequency.
Comparison of the rate of the muscular contractions produced
by an instantaneous shock from an induced current with the slow
persistent contractions by which the skeletal muscles are usually
thrown into voluntary contraction, has led to the conclusion that
the latter are tetanic in character, i.e. are the effects of a series of
impulses from the nerve centres. To support this theory of the
discontinuity of excitation in voluntary contraction, Wollaston
(1810) adduced the sound developed by the muscle in contracting,
20
PHYSIOLOGY
CHAP.
in which one tone predominates. On introducing one finger into
the auditory meatus and then forcibly contracting the muscles of
the arm, a dull murmur is heard similar to that from a distant
vehicle moving rapidly along the surface of a road. He regarded
the tremor often noticed in the muscular movements of old people
as the effect of an abnormal slowing of the muscular vibrations
due to debility and age. From his studies of voluntary muscular
contraction Wollaston concluded that the sound in the contracting
muscle corresponds to a frequency that oscillates between 14 and
15 per second at the minimum, 35 and 36 at the maximum.
Helmholtz (1864) investigated the subject of the muscle sound
with better methods. He observed that if in the dead of night
the auditory meatuses are stopped and the masseters forcibly
contracted, a murmur is heard in which there is a ground tone
that lasts as long as the voluntary contraction, and does not
change materially with increase of muscular tension.
n
s
,VAV/ fsrsfW\W't*w AMAA AAA*WWy / A- AM/ ./AAA/NAA/ / A/. W\ '/ //v%A'V////>lAA''/-'////y/'^/yA'lAA/-/Wyv/v/yv.//1A/W
Fn:. 13. — Vibrations of biceps muscle of rabbit's femur on stimulating the spinal cord or sciatic
nerve with forty-two induction shocks per second. (Kronecker and Stanley Hall.) The middle
line s gives the vibrations of a tuning-fork in TJn sec. ; the upper line n is the tracing of the
vibration of the muscle during stimulation of the sciatic ; the lower line in, the vibrations of
the muscle during stimulation of the cord. Both tracings were obtained by applying a
sensitive lever to the surface of the exposed muscle.
The same tone is heard on firmly contracting the eye-muscles
or applying the stethoscope to the arm-muscles during voluntary
contraction. Helmholtz pointed out that the vibrations which
give rise to the sounds did not follow in regular sequence like
those of a musical tone. To determine the frequency objectively,
he applied watch springs or strips of paper to the muscles which
were vibrating in unison, and found the vibrations to be 18-20
per second. He confirmed the fact previously observed by Du Bois-
Keymond, that vibrations of the same frequency as those of
voluntary contraction are produced when a tetanising current of
high frequency is applied not only to the nerve or muscle but
also to the spinal cord of an animal. Subsequently, Helmholtz
pointed out (1864) that the tone perceived by the ear corresponds
not to the effective number of muscular vibrations, but to the
resonance tone proper to the ear of the observer, which corresponds
with the first over-tone or the octave of the fundamental tone of
the muscle, and is difficult to determine, because it lies at the limit
of the perceptible tones. He stated in effect that the tone heard
on voluntary contraction of the masseter muscles corresponds to
i GENERAL PHYSIOLOGY OF MUSCLE 21
36-40 vibrations, while the natural vibration of the human muscles is
only 18-20 per second. Similar results were obtained by Kronecker
and Stanley Hall (1879), who registered the oscillations in the
mass of the exposed femoral biceps of the rabbit by applying the
lever of a Marey's tambour to its surface, and tetanising the spinal
cord with an induced current of 43 shocks per second (Fig. 13).
Later work on this subject, particularly by Loven, von Kries,
Schafer, Wedensky, and Stern (1900), however, yielded different
and apparently contradictory conclusions in certain particulars,
while confirming the fact that all voluntary contractions, and
those due to strychnine and to reflex or direct stimulation of the
cerebral centres, are discontinuous phenomena, i.e. are due to the
summation of a series of impulses emanating from the centres and
transmitted to the muscles.
It is difficult on the generally accepted theory of Helmholtz,
that the sound heard from a muscle either in tetanus or in per-
sistent voluntary muscular contraction depends essentially on the
displacement of the contractile substance, to explain the fact that
simple twitches or contractions, such as the cardiac systole, can
give rise to a murmur.
Lastly, it should be added that Briinings (1903) made an
accurate analysis of the muscle sound produced by direct and
indirect stimulation with faradic currents of varying frequency.
He found that it always has the character of a simple tone, and
that its frequency never differs from that of the stimulus. But if
on direct stimulation the frequency of the faradic currents is
constantly increased, the intensity of the muscle sound grows
proportionately less, until it disappears altogether after reaching a
certain limit of frequency, though the tetanus still continues.
This maximal limit is higher in proportion to the strength of the
stimulus and the freshness and the temperature of the muscle.
Its relation to the temperature in particular is surprisingly
regular. While, e.g., at Y'5° C. 3 stimuli per second is the maximum
at which an isorhythmic murmur can be obtained, no sound being
heard at any higher frequency, at 35° C. the highest perceptible
tone is observed with 435 vibrations.
IV. To complete the analysis of the mechanical effects of
excitation we must further consider the variations in thickness of
the muscle and the propagation of excitation along its fibres. In
excitation the long axis of the muscle shortens, and its transverse
axis increases, while the surface of the muscle diminishes during
the contraction and increases in relaxation. But the question was
long disputed as to whether the volume of the muscle also varied
during contraction, and diminished during tetanus. This question
was experimentally investigated long since by Borelli, Glisson,
Swammerdam, and subsequently with better methods by Barzel-
lotti, Erinan, Joh. Mu'ller, E. Weber, and many others. The
22
PHYSIOLOGY
CHAP.
results were contradictory. Many observers were unable to dis-
cover any variation in the volume of the muscle, while others saw
a more or less marked diminution in volume during tetanus.
Among the former we must
mention Barzellotti (1795-96),
who invented the method of
introducing the muscles of a
frog into a closed vessel full of
water, which carried a capillary
tube: among the latter, Erman
(1812), who with the same
method observed a marked
diminution in volume. An
Fin. 14. — Myograph suitable for man, to record
increased bulk of the muscles. (Marey.) Con-
sists of a capsule covered with a rubber mem-
brane, pulled out by a spiral spring. A metal
rane, pue ou y a spra sprng. mea , . 11
button in the centre of the membrane carries the exhaustive research by
exciting current to the skin immediately above /1oq7\ wVir> riprfppfpH "
the muscle to be explored. The compression of ViO° ' )> wn
the air in the capsule flunns the contraction lis lottl's method with nce a-
tiansimtted by a rubber tube to the lever of a . .,
recording tambour. JUStUientS, aiSO jailed to Obtain
even minimal variations of
volume in a muscle during tetanisation.
The muscle therefore changes in form and extent of surface,
but not in density and volume, during activity. Were they not
sanctioned by use it would be better to give up the inappropriate
expressions " contraction " and " relaxation," to indicate the two
phases of muscular activity.
The state of contraction in a muscle can also be studied by
tracings of the area of its cross-section. Marey invented special
myographs for this purpose which can be applied to man in
physiological and clinical research. The simplest of these are
shown in Figs. 14 and 15. Curves of simple contraction and of
FIG. 15. — Exploring tambour that can lie used as a myograph to transmit the phases of increasing
thickness of a contracting muscle to a tambour with writing lever.
tetanus recorded by this method closely resemble those we have
already analysed in the corresponding changes in the length of a
muscle. But there is one important difference ; while the former
record the algebraic sum of the changes in length in all tbe
different parts of the muscle, the latter only trace the changes in
i GENEKAL PHYSIOLOGY OF MUSCLE 23
thickness of the particular portion of the muscle to which the
myograph is applied.
The rate of propagation of the contraction wave can be calcu-
lated from the interval between the contraction of two different
points of an isolated muscle, traced by two myograph levers placed
on the muscle at a known distance from each other, and writing
on the same drum. The sartorius muscle of the frog, in which
the fibres were parallel to one another, is the most suitable for
this purpose. Before dissecting it out, the frog should be curarised
to eliminate the action of the stimulus upon the intramuscular
nerves. When an induced shock is applied to one end of the
muscle, the contraction spreads in wave-form to the other end, at
a velocity which can be calculated by means of the two curves.
Fig. 16 shows that the second curve rises about 0-06 sec.
after the commencement of the first curve : in passing over the
Fir,. 16.— Two myograms of thickening from the same frog's muscle, obtained by applying two
/(/'/UTS myographiqves at a distance of 15 mm. to measure the velocity of the excitation wave.
(Marey.) Time tracing in T£n sec.
part of the muscle between the two rnyographs the wave of con-
traction therefore occupied 0'06 sec. As the distance between the
two levers was 15 mm., the wave travelled at a rate of about 1 m.
per second.
The length of the wave can also be calculated from the
duration of the thickening of the fibres (in Fig. 16 about seven
vibrations of the tuning-fork = O07 sec.), and from the rate at
which the wave is propagated. Bernstein stated that the duration
of the twitch in any segment of the muscle (which must be dis-
tinguished from the duration of the twitch of the whole muscle,
which usually takes longer) is from 0'05 to 01 sec. Assuming
Bernstein's calculations of the rate at which the wave travels—
3-4 m. per second, to be correct — then the length of the wave, or
the part of the muscle over which it passes in O'05-O'l sec., is on
an average 200-300 mm.
As the length of each muscle fibre rarely exceeds 40 mm. the
entire length of each fibre is usually involved in the contraction.
It is only at the beginning and towards the end of the contraction
that one or other end of the fibre is not active; throughout the
24 PHYSIOLOGY CHAP.
greater part of the duration of the wave, each segment of the
fibre will be in some phase of activity, which is more advanced in
the segments nearer to, less advanced in those more distant from,
the points at which the stimulus is applied.
The rate of propagation varies considerably in the muscles of
the same animal according to the method adopted. According to
Aeby (1860), who first applied the graphic method to this research
in the gracilis and semi-membranosus muscles of the frog, it is
about 1 m. per second (1'2-1'G in.). Yon Bezold's and Marey's
results were much the same, while Bernstein, who compared the
moments at which successive waves, travelling in the same
direction from different points, reached a particular spot at a
known distance from each of them, obtained much higher values
(3'2-4'4 m. per second). Hermann who excited the two sartorius
muscles in a curarised frog at two different points, and simultane-
ously, gave the rate as 2-7 m. per second.
Just as the velocity of the muscle twitch differs considerably
in the muscles of different animals (cold-blooded and warm-
blooded), and in different muscles (pale or red, quick or torpid), so
the velocity at which the wave of excitation or contraction travels
also varies. In the retractor collis muscle of the tortoise the rate
at which excitation is transmitted varies between 05 and T8 m.
(Hermann and Aeby) ; while in the sterno-mastoid muscle of the
dog it is equal to 3-6 m. (Bernstein and Steiner).
The rate of propagation of the wave may v/iry greatly in the
same muscle with the strength of stimulus, still more with the
state of its excitability, which varies largely according to fatigue
and with the temperature. Schiff (1856-58) first studied the
interesting phenomenon known as the ideo-muscular contraction,
which directly shows the transmission of a contraction excited by
mechanical stimuli along mammalian muscles exposed shortly
after death. A ridge or weal forms when the muscle is tapped
or stroked with a blunt object, and persists for a certain time ;
two contractile waves start from it, and spread towards the
two ends of the muscle, where they are reflected back towards
the spot stimulated, and collide with secondary waves from the
weal. As the excitability of the tissue is exhausted, the velocity
of this wave conduction also diminishes.
These observations on the propagation of the contraction wave
through the muscle refer to artificial direct stimulation at one
end. With natural or indirect stimuli, when the excitation
reaches the muscle through the end-plates of the motor nerves that
lie towards the middle of each fibre, the contraction must invade
the total length of the fibres in a much shorter time. In fact we
assume that the contraction is propagated from the end-plates in
two opposite directions towards the two ends of the fibres, and
therefore has only to traverse half its length.
GENERAL PHYSIOLOGY OF MUSCLE
25
When, instead of using make and break shocks from an
induction coil, a muscle is excited with the constant current,
it contracts at each closure or opening of the current, but is
relaxed during the passage of the current. This law usually holds
good if a current of medium strength is employed, but if the
strength of the current exceeds certain limits, the make or break
of the current is immediately followed by a tetanus (closure or
opening tetanus). This fact, which was first noted by Wundt,
can also be observed on man, by sending a strong galvanic current
into a muscle, or even a comparatively weak current when the
muscle is degenerated.
Curarised muscles react more readily to the closure and open-
ing of a constant current than to the
more transitory make and break shocks
of an induced current. Hence in ex-
amining the rate of transmission of
contraction, the constant current is pre-
ferable.
The excitation at make of the con-
stant current is greater than at break,
as can be seen by varying the amount
of current passed through the muscle,
by means of a rheochord.
Von Bezold, Engelmann, and Hering
showed that the "law of contraction"
which Pfliiger formulated for nerve (see
Chap. IV.) holds for muscle also : the
closing contraction always starts from
the negative pole, while the opening
contraction is set up at the positive
pole ; in other words the make excita-
tion is kathodal, the break excitation is
anodal. This law may be demonstrated by placing two myograph
levers far apart on a curarised muscle, to the two ends of which
the two electrodes are applied. At make and break of the
current the two contractions are recorded at brief intervals, but
the kathodal always precedes the anodal at the closure, and the
anodal the kathodal at the opening, of the current.
V. In order to understand the changes in form which the
muscle undergoes during activity, it is necessary to examine the
structure of the muscle fibre under the microscope, and the
changes which it undergoes during contraction.
Each muscle fibre consists of soft protoplasm enclosed in an
elastic tubular sheath, the sarcolemma. This membrane is so
resistant that it is uninjured by a pull strong enough to rupture
the muscle substance (Fig. 17). Oval nuclei parallel with the
long axis of the fibre generally lie immediately under the sarco-
Fi
}. 17. — Sarcolemma of mammalian
muscle. (Schafer.) Highly magni-
fied. The sarcolemma is left clear,
owing to rupture of the muscular
substance.
26
PHYSIOLOGY
CHAP.
lemma, but they belong to the muscle substance, and not to the
sarcolemma. Each muscle fibre may be regarded as a very
elongated cell, provided with several nuclei, the sarcolemma
representing the cell membrane. The diameter of the fibres
usually varies from 30 to 40 /*, but may be greater or less in
different classes of animals.
The substance proper or protoplasm of the fibre presents a
double striation, longitudinal and transverse, owing to the fact
that it consists of a bundle of numerous primitive fibrils arranged
parallel, each of which has a complex transverse structure.
On examining a fibre in cross-section, each primitive fibril
appears as a rounded spherical granule, comparatively dark in
colour, surrounded by a lighter non-differentiated substance — the
sarcoplasm. The amount of sarcoplasm may vary considerably in
s ,
Fio. 18. — Traiivi'rsi- section of two striated muscle fibres of rabbit. (S/.ymonowk-z.) Magnified
1000 diameters. At A the primitive fibrils (.S) are equally distributed in the sarcoplasm (S^).
At B they form polyliedric segments known as Cohnlu-im's areas (Cc).
different muscles, just as the mode of division or grouping of the
primitive fibrils within the sarcoplasm also differs (Fig. 18).
On examination of a fre^h muscle fibre in serum, a longi-
tudinal striation is seen owing to the parallel arrangement of the
primitive fibrillae. A series of light and dark striae at right
angles to the longitudinal axis of the fibre are also visible, which
are due to a double series of light and dark parallel bands that
alternate regularly through the entire length of the fibre. The
dark striae are broader than the light, and show at the boundary
of the clear bands a darker layer which seems to consist of a series
of dots.
On teasing out dead muscle fibres hardened in alcohol, it is
possible to separate the primitive fibrils. This is easiest in
animals which have the most abundant sarcoplasm (Fig. 20).
Under a high power, each fibril is seen to consist of alternating
light and dark bands of approximately uniform width. But in
the middle of the clear band there is a very fine dark line,
GENERAL PHYSIOLOGY OF MUSCLE
27
which was first described by Aniici, but is generally known as
Krause's membrane. Krause regarded this as a delicate little
membrane, dividing the fibrils into a series of segments which he
called sarcomeres. In the muscles of certain insects as well as
those of some mammals, a further differentiation is visible with
strong magnification in both light and dark bands, for the
description of which the reader must refer to text-books of modern
histology.
From the physiological point of view the different refracting
:::::::- •••••.
:, !;ij;;;;;;;
is
•iiffjj in I,
tmfl &aiwis
ii-j 3 !»»MwFfi» ;
Dun --/(({"'V't'/
jllHll '."iinimTf/ -,
-.'!'!'.'» BjrnjHifijf /'
ufff unniTinm /
FIG. 19. — (Left.) Muscular fibre of a mammal examined fresh in .serum. (Schiifer.) Highly
magnified.
FIG. 20. — (Right.) Fragment of frog's muscle fibre in which a few fibres have been isolated.
(Szymonowicz.) Magnified about 650 diameters, n, nucleus ; fp, primitive fibril ; is,
isotropous layer; an, anisotropous layer; A, Amici's striae or intermediate disc.
power of the respective light or dark bands of muscle fibres is
more important. Boeck of Christiania was the first who pointed
out that certain tissues, among them the muscles, were doubly
refracting or anisotropous, but Briicke (1857) showed that the
whole fibre is not anisotropous, a portion of its substance being
singly refracting or isotropous. When the fibres are viewed by
polarised light, the dark striae show up light on the black ground
formed by crossed Nicol prisms : the light striae, on the contrary,
appear dark. The former are doubly, the latter singly refracting.
To obtain a clear idea of the changes which the striatiou of
the muscle fibre undergoes during contraction, it is necessary to
fix the muscle as the contraction wave crosses it, in order to study
PHYSIOLOGY CHAP.
all the details of its appearance under the microscope. This is
easily accomplished if a fresh muscle from an insect's leg is
dropped into absolute alcohol or solution of osmic acid. These
reagents excite a series of waves in the muscle fibre, and fix it at
the same time, so that on teasing out some bundles of fibres for a
few minutes and examining them under the high power, the so-
called "fixed wave of contraction " can be seen in the form of
nodes or fusiform swellings. In some fibres it is also possible to
see the so-called " lateral waves," due to contraction of one surface
of a fibre which is relaxed on the opposite side, and intermediate
parts between the two surfaces show gradations of all the
intermediate stages between the phases of contraction and of
relaxation.
Engelmann (1878) made the most important contributions to
this subject. He found in the muscle fibres of an insect (Thele-
pliorus melanurus) treated as above, that the optical properties
and the breadth of the isotropous and anisotropous bands altered
inversely to the changes in the form of the fibres during contrac-
tion. As shown by Fig. 21 the isotropous layers become ?is a
whole more refracting, i.e. more compact and darker, while the
anisotropous layers become less refractive, i.e. more fluid and
Lighter. The breadth of both layers diminishes during contraction,
but more rapidly in the isotropous than in the anisotropous bands,
so that the latter increase in volume at the expense of the former.
Thus, according to Engelmann, we must assume that during
contraction the anisotropous substance subtracts water from the
isotropous.
The same fact is more evident in Fig. 22, which represents a
lateral contraction wave, observed by Eollet near a motor end-plate.
Ranvier (1880) employed an ingenious method for determining
which bands of the sarcoplasm contracted, and which behaved
passively, when stimulated. He put two muscles of a frog or
rabbit into a condition of absolute isometry, and then fixed them
by absolute alcohol while one was inactive, the other in tetanus
produced by an induced current. On then comparing the muscles
under the microscope, he found a reduction in the breadth of the
dark anisotropous discs in the fibres of the tetanised muscle, which
were now perceptibly equal to the clear isotropons discs, while
in the inactive muscle they were considerably broader. He
further pointed out that there was in the fibres of the tetanised
muscle a considerable increase of the interfibrillar sarcoplasm,
which appeared to break up the fibre into fibrils.
According to Eanvier, therefore, the layers of anisotropous
substance diminished in volume. Contrary to Engelmann's
results, water does not pass from the isotropous to the anisotropous
substance during tetanic tension, but diffuses from the latter into
the interfibrillary substance.
GENEKAL PHYSIOLOGY OF MUSCLE
29
Since the experimental conditions adopted by the two authors
are essentially different, these apparently contradictory conclusions
may not be irreconcilable.
Both Engelmaim and Eanvier agree, though from different
FIG. 21. — (Left.) Fixed wave of contraction in muscular fibre of insect. (Engelmann.) The right
half of the figure shows the fibre examined under polarised light; the doubly refracting bands
look light on a dark ground with crossed Nicols. R, segment of fibre at rest ; //, segment
beginning to contract ; C, contracted segment, a, intermediate disc of Amici ; b, accessory
disc of clear or isotropous layer ; c, dark or anisotropous layer.
Fio. 2'2. — (Right.) Fixed wave of lateral contraction near a motor end-plate (Pin) obtained by
Rollett from a muscle fibre of Cassida eifuestris. Very high magnification.
reasons, in regarding the anisotropous disc as the only contractile
part of the muscle fibre. Engelmann based this conclusion on a
long series of observations which showed that contractility and
double refractivity appear simultaneously during the ontogeiietic
development of the muscle cells, and that the contractile force is
greater in proportion as the double refractivity is more intense.
30 PHYSIOLOGY CHAP.
Kanvier draws the same conclusions from the fact brought out
directly by his experiments, viz. that the anisotropous discs are
the only ones that change in form and diminish in volume during
the state of isomeric tetanisation.
More recently Schafer (1891) and Hiirthle (1901-4) have
studied the microscopic variations in the muscle fibres during
contraction, by photography and cinematography. Schiller's
observation in particular, according to which minute canals,
parallel with one another, run in the anisotropous layer in the
direction of the fibres, is important. During contraction the
isotropous substance penetrates these canaliculi, which dilate so
that the muscular segment becomes wider and shorter.
It is in any case certain that the transverse striatiou due to
the separation of the doubly refracting from the singly refracting
tibres is not indispensable to the contractility of the elements,
because the unstriated muscle cells are contractile although much
more sluggishly so than the striated fibres. Kanvier assumes in the
latter that the separation of the doubly refracting substance into
distinct masses facilitates and makes possible a quicker displace-
ment of the fluid from the surrounding parts into the contractile
layers.
VI. We must next consider the phase of relaxation, in which
the shortened muscle elongates and describes a curve which
closely resembles the curve of contraction. The sole difference
between contraction and relaxation lies in the fact that the latter
is, generally speaking, more variable in its duration and rate of
drop towards the abscissa.
Formerly the elongation of the contracted muscle was regarded
as a physiologically passive phenomenon, due to the cessation of
the process of contraction. Very few admitted that both the
shortening and the lengthening of the muscle were due to
converse physiological processes : yet this theory of the con-
tractive and expansive activity of skeletal muscle, which we have
maintained since 1871, agrees with the corresponding theory of
the properties of amoeboid protoplasm, cardiac muscle, and the
musculature of the vessels and gut, which was discussed at length
in Vol. I.
The length of any skeletal muscle in the resting state is not
constant, but varies under different intrinsic and extrinsic
conditions.
When any muscle or the tendon by which it is attached to
the bone is divided in the living animal, the two segments draw
apart or retract,- as though the muscle were normally in elastic
tension and the distance from the points of its insertion were
greater than the natural length.
Cut muscles also retract after death, so that the tension of
normal skeletal muscle is partly an effect of the elasticity of the
i GENEEAL PHYSIOLOGY OF MUSCLE 31
muscle and the stretching to which it is mechanically subjected.
One advantage of this extension is that, even if fully relaxed, the
muscle on contraction immediately approximates its two points
of insertion, without any loss through mechanical causes.
The elastic tension of the resting muscle under normal con-
ditions is not, however, explained solely by this passive traction.
During life it undergoes marked oscillations under various
conditions. This tension of the muscle, which is not passively
determined by the distance between its points of insertion but
is the expression of muscular activity, is known as its tone.
Many facts show that the natural length of the resting
muscle, on which its natural tone depends, is directly dependent
on the nervous system. We shall elsewhere study the mechanism
of this constant tonic influence which the nerve exercises upon
the muscle : here we must confine ourselves to describing the
classical experiment of Brondgeest (1860) which demonstrates it.
If the lumbar plexus of a frog is cut on one side, after its spinal
cord has been divided higher up so as to paralyse voluntary
movements, and the animal is suspended vertically by its head,
the two hind-limbs of the animal take up essentially different
positions. The leg of the side on which the nerves were cut
hangs fully extended, i.e. the muscles are flaccid, while that of
the other side, on which the nerves are intact, is slightly flexed
owing to the tone of the muscles. A similar phenomenon is
observed on man in the fairly frequent cases of facial paralysis ;
the distortion of the mouth and nose, which is very pronounced
in speaking, is also obvious even in the state of absolute inactivity
of all the facial muscles ; it is due to loss of tone in the muscles
of the paralysed side and its persistence in the muscles of the
sound side, owing to which the latter pull on the former.
In certain abnormal conditions of the nervous system — as in
hysteria, somnambulism, and hemiplegia of long standing — the
tone of the muscles may be enormously exaggerated and become
contractured (Brissaud and Eichet). This condition is essentially
different from tetanus, which is due, as we have seen, to summation
and fusion of muscular contraction. Simple twitches and even
a true tetanus can be obtained from contractured muscles, by
suitable electrical stimulation, as in the normal resting muscle :
and the characteristic muscle sound can be heard during tetanus,
that is absent in simple contracture (Brissaud and Boudet).
Independently, again, of the nervous system, contracture may
result from intrinsic alterations in the muscle, caused by certain
poisons. This is a tonic state, quite distinct from the rapid
contractions which can also be evoked from the muscle by means
of make or break shocks during contracture. Among the poisons
capable of producing this phenomenon, veratrin has been the
most studied, particularly by von Bezold, Fick, Bohm, and others.
PHYSIOLOGY CHAP.
If one muscle of a lightly veratrinised animal (frog or toad)
is detached, fixed to the myograph, and stimulated with an
induction shock, the resulting curve will be very different from
that of the normal twitch (in Fig. 23), as the rapid contraction is
followed by a long contracture which slowly diminishes.
Fick endeavoured to explain this phenomenon by assuming
that the rapid primary contraction depends on the indirect
excitation of the muscle transmitted by the intramuscular nerves,
and the subsequent contracture on the direct excitation by the
poison. fBut this interpretation is contradicted by the fact that
it is possible to obtain the same form of curve from animals that
have previously been curarised. Griitzner proposes another
explanation, and suggests that the rapid primary and slow
secondary contraction depend on two distinct species of fibres
FIG. 23. — Contracture of gastrocnemius muscle of veratrinised toad, produced by simple break
shock from an induced current. (Bottazzi.) The tracing shows that the veratrin contracture
is preceded by an ordinary contraction, which is suddenly interrupted at the commencement
of the relaxation. Time tracing in half-seconds.
(pale and red, rapid and torpid) in the muscle. This hypothesis
is contradicted by the later observations of Carvallo and Weiss,
according to which both the pale muscles and the red exhibit
the characteristic veratrin contracture. The most probable
explanation is that of Bottazzi, who regards the coexistence of a
rapid and a slow contraction as due to the presence in the
muscle fibres of two distinct contractile materials, endowed with
different degrees of excitability — anisotropous and isotropous
substance.
The hypothesis that the singly refracting substance of the
sarcoplasrn is capable of causing positive and negative variations
in the tone of the muscle, independently of the simultaneous
rhythmical excitation of the doubly refracting substance, explains
the phenomenon discovered by Fano in the auricular musculature
of Emys europea (Vol. I. p. 319), which exhibits rhythmical
oscillations of tone, on which the ordinary cardiac rhythm is
superposed. The plain muscles of the oesophagus in toad, fowl,
i GENERAL PHYSIOLOGY OF MUSCLE
Aplysia (Bottazzi), aud those of the dog's stomach also show
automatic rhythmic oscillations of tone, similar to those in the
tortoise auricle, and may be explained by contractility of the
sarcoplasrn, which certainly predominates in these muscles.
More recently (1901) Bottazzi lias endeavoured to extend his
hypothesis to all contractile protoplasm, including the striated
muscles of the skeleton. Why, he asked, should the muscular
tetanus due to the fusion of elementary twitches reach a height
considerably greater than that of a single twitch obtained from
the same muscle with maximal stimulation ? This is explained
by assuming that owing to the tetauising stimulus and the
weight applied to the muscle the muscular tone is exaggerated
into a contract ure, which represents a form of " internal support "
maintained as long as the muscle remains shortened, while the
rhythmical contractions rise above the level of this contracture
(v. Kries, v. Frey, Griitzner). v. Frey (1877) had demonstrated
Fin. 24.— Myogram of frog's gastrocnemius loaded with 10'5 grins, (v. Frey.) t, t, myograms of
tetanus; *•. i. , s.i. , myograms of .simple contractions obtained with single shock of the same
induced current; x.in.s., myograms of a group of contractions obtained with the muscle
supported, i.e. relieved of the weight during relaxation.
that on exciting the muscle of a frog by a series of induction
shocks, while the muscle is so supported that in relaxing it is not
stretched by the weight which it lifts in contracting, the con-
tractions rise in proportion as the lever-support is raised by a
screw, till they eventually reach the same height as the tetanus
of the same muscle, loaded and not supported (Fig. 24).
But v. Frey's explanation is not sufficient. We still ask-
on what does the contracture depend '{ It cannot be due to
activity of the same contractile substance as that on which muscle
twitches depend, for it would then be unable to function as an
internal stimulus. Bottazzi holds that it can only he interpreted
on his hypothesis of the contractility of the sarcoplasm. He
assumes that the rhythmical faradic stimuli (and in our opinion
the weight which stretches the muscle as well) are capable, in
addition to the rapid twitches that su inmate in the curve of
tetanus, of evoking a further excitation and contracture of the
sarcoplasm, which constitutes an internal support. If after induc-
ing " veratrin contracture " in a muscle it is excited with a maximal
induction shock, the resulting twitch rises above the level of
VOL. Ill D
34 PHYSIOLOGY CHAP.
contracture to the same height to which it rose above the abscissa
of the base line, previous to contracture (Fig. 25). Probably,
therefore, the rapid shortening of the muscle in contraction is
independent of the slow and persistent shortening in contracture.
The former, depends on the activity of the anisotropous, the latter
on that of the isotropous substance.
The fact that the tetanus-curve of a muscle rises normally
above the maximal twitch is, however, capable of a far more simple
interpretation. We have seen that the excitation spreads over
the muscle like a wave. Hence even after a maximal shock all parts
of the muscle cannot be simultaneously thrown into contraction.
On the contrary, the parts first excited already begin to relax before
the others reach the maximum of contraction (Fig. 16, p. 23). So
that with maximal shocks the extent of the muscular shortening
FIG. 25. — Two contractions of toad's gastrocnemius, before (1) and after (2) veratrin contracture
(I') on exciting by maximal induction shocks. (Bottazzi.)
depends on the point of excitation, the rate at which the contrac-
tion wave travels, and the rapidity with which the individual
portions of the muscle contract and relax. If, on the other hand,
a series of excitation-waves are sent in rapid succession through
the muscle, all its parts will finally be in maximal contraction at
the same time, which must obviously result in a much more
pronounced contraction (Fr. W. Frohlich).
The general conclusion that can be deduced from this discussion
of the tone of the skeletal muscles is that tonicity may undergo
positive or negative oscillations, which are probably the expression
of corresponding changes in the elastic forces intrinsic to the
muscular protoplasm. These changes may be due to the tonic
influence exercised by the nerves 011 the muscles, or to stimuli
acting directly on the latter. After section or paralysis of the
nerves or motor end-plates the tone of the skeletal muscles is
abolished ; it is normal in healthy individuals in whom the
antagonist muscles exert reciprocal traction ; it becomes more or
less strongly exaggerated under certain special abnormal conditions
i GENERAL PHYSIOLOGY OF MUSCLE 35
of the nervous system, some of which may also he produced
artificially in healthy subjects, and by curtain poisons which act
directly upon muscle.
It should be added that muscle tone may be inhibited under
special conditions ; i.e. it may suffer a negative variation in which
the length of the muscle is exaggerated beyond the normal.
An interesting example of obvious lengthening of the muscles
after direct excitation of their motor nerves was first observed by
Eichet (1882) on the muscles of the crab's claw. This organ for
the capture of prey and weapon of offence and defence consists of
two arms, one of which is fixed, the other movable by means of
two muscles of antagonist action, the one a very delicate abductor,
the other a much thicker and stronger adductor. If the rigid
branch of the claw be fixed in a clamp, and a thread attached to
the movable arm, it is easy (either by direct transmission to a
writing-lever, or by indirect transmission through a couple of
Marey's tambours joined together) to record on a moving drum
the reactions of the claw-muscles to induced or constant currents,
acting directly on the nerves of the claw, or on one or other of the
muscle.?.
On exciting the nerve with a weak current, Eichet saw that
the claw opened ; on exciting with a strong current, on the
contrary, it closed. In the first case the action of the abductor
prevailed, in the second, of the adductor.
Eichet's observation was confirmed by Luchsinger, and
elucidated by further experiments of Biedermann (1887-88). If
the abductor is divided before exciting the nerve of the claw, the
result is the same as in Eichet's experiments ; with weak stimula-
tion the claw opens, with stronger excitation it closes. In the
first case, therefore, there is elongation or relaxation of the adductor,
in the second, contraction. If, on the contrary, the adductor be
cut, a weak current causes opening of the claw, or contraction of
the abductor, a stronger current closing of the claw and lengthen-
ing of the muscle. The elongation of the muscle apparent in the
first experiment with weak stimulation, in the second with strong,
was interpreted by Biedermann as an inhibition of muscle tone,
similar to that produced in cardiac muscle by excitation of the
vagus.
Piotrowrski (1893) confirmed the fact already noted by Bieder-
mann that to produce the inhibitory effect it is essential that the
preparation should be in a state of considerable tonic excitation ;
in fact it can never be obtained in summer, when the tone of the
muscles is low. He noted further that the same current may
evoke now contraction and now inhibition, according as the tone
of the preparation is low or high. Temperature has a marked
effect on the phenomenon ; high temperatures abolish the
inhibitory effect ; low temperatures favour it ; the optimum for
36 PHYSIOLOGY CHAP.
obtaining the inhibitory effect is about 8° C. For both claw
muscles he saw that the latent period of the inhibition produced
by a minimal stimulus is shorter than that which precedes con-
traction evoked by a similar stimulus. Lastly, he found on
stimulating the nerve with simple induction shocks that when the
tone of the muscle was very pronounced the contraction was
preceded by a brief depression of tone. The same was noted by
(lad, and later by Nagy von Eegeczy and by Cowl, for nerve-
muscle preparations of the frog under special conditions.
All these researches on the reaction of striated crustacean
muscles to stimuli present numerous analogies with the phenomena
of cardiac muscle. Certain histological observations of Biedermann
justify the conjecture that there are two different species of nerve-
fibres in the crab's claw-muscles, as in the heart, some of which
may excite the assimilatory or anabolic processes, others dis-
similatory or katabolic changes. The former function like the
vagus fibres, the latter like the sympathetic fibres, on the heart.
Mangold (1905) has recently confirmed this hypothesis of a double
in nervation of these muscles.
VII. Alterations of form (contraction and relaxation, positive
and negative variations in tone) are only the external expression
of the physiological processes that take place within the muscle.
To obtain a clear idea of these, we must next investigate the
chemical composition of muscle, and the changes which it under-
goes during activity and in rest.
Muscle undergoes a profound physico-chemical alteration after
death, which is termed rigor mortis. Muscles excised from the
body of the living animal, or merely cut off from the circulation,
become rigid after a certain time (varying from ten minutes to
several hours) i.e. they are less soft and elastic, less extensible and
at the same time shorter, thicker, darker, and less transparent.
Their alkaline or neutral reaction becomes acid. As early as 1833
Sommer regarded cadaveric rigidity as a coagulation phenomenon.
Briicke accepted the same theory, but proof was afforded for the
first time in 1859 by Kiibne. He showed that when the living
muscles of the frog were completely deprived of blood by an
endovascular injection of salt solution, and gradually cooled to
- 7° C. rubbed into fragments and squeezed under high pressure, it
was possible at a temperature of 0° to separate off a fluid which
filtered slowly, was of syrupy consistency and slightly alkaline
reaction, which he termed muscle plasma.
At the temperature of the air, muscle plasma clots as easily as
blood plasma, and takes on a gelatinous consistency. A fluid
afterwards separates out, owing to the contraction of the clot.
The substance that clots was termed my o sin by Kiihne, and the
liquid that separates off, muscle serum. Muscle plasma, like blood
plasma, begins to clot at the points of contact, and the process of
i GENERAL PHYSIOLOGY OF MUSCLE 37
coagulation is accelerated by agitation and by rise of temperature.
Cold checks coagulation ; above 0° C. it proceeds very slowly ; at
higher temperatures it becomes faster, and at 40° very rapid.
Addition of distilled water or acids causes instantaneous co-
agulation.
It is obvious that the coagulation of muscle plasma corresponds
to the rigor that develops after the death of the muscle. Muscle
plasma indeed contains the whole of the soluble proteins of living
muscle, and as on cooling muscle to - 7° C. its excitability is not
abolished, but merely becomes latent, it may reasonably be
concluded that extraction of muscle plasma at a low temperature
destroys its structure, but produces no chemical alteration in the
substance of living muscle.
Kiihne's discoveries on frog's muscle were extended to the
muscles of warm-blooded animals by Halliburton (1887), who nob
only employed cooling to check the coagulation of muscle plasma,
but also added neutral salts (sodium chloride, sodium and
magnesium sulphate), as in the preparation of salted blood
plasma (Vol. I. Chap. V.) The addition of water to salted muscle
plasma causes it to coagulate like blood plasma when the fluid
is at body temperature, while it does not clot at 0° C. When
coagulation sets in the reaction of the plasma becomes acid. In
blood plasma fibrin is formed from fibrinogen by the action of an
enzyme, and similarly in muscle plasma myosin is formed by the
action of an analogous enzyme from a mother-substance, which
Kiilme and Halliburton termed myosinogen. As in blood,
fibrinogen, not fibrin, is pre-existent, so in muscle myosinogen pre-
exists, not myosin. 0. v. Fiirth (1902-3), however, denies this
analogy between the coagulation of blood and of muscle, as he
failed to obtain experimental proof that the rigor mortis of muscle
depends on the action of any ferment.
Myosin has the same chemical composition as globulin ; it is
insoluble in distilled water, soluble in solutions of neutral salts
(sodium chloride, sodium and magnesium sulphate), and it coagu-
lates at a temperature of 55°-60° C. Myosin when dissolved in
neutral salts has all the properties of myosinogen, and can easily
be reconverted into myosin on simple dilution (Halliburton).
The fact that myosin dissolved in a weak salt solution at a low
temperature is doubly refracting in polarised light, justifies the
assumption that the anisotropous discs that are actively concerned
in muscular contraction are principally composed of myosinogen
(C. Schipiloff and A. Danilewsky).
Halliburton succeeded by means of fractional heat coagulation,
and by salt solutions of different concentrations, in separating five
different proteins from the muscle plasma, four of which are
coagulable at different degrees of temperature, and one is un-
coagulable. This last is a proteose, and is apparently identical
38 PHYSIOLOGY CHAP.
with the eozyme which effects the coagulation or transformation
of myosinogen into myosin. Of the four coagulable proteins, two
(inyosinogen and the paramyosinogen or musculin of Hammarsten)
form the clot, while the two found in the muscle serum (myo-
globulin and -myoalbumiii) closely resemble or are identical with
those present in blood serum.
Muscle serum holds the pigments to which the muscles owe
their colour in solution. The normal pigment of the red muscles
is due to haemoglobin, identical with that of the erythrocytes, as
was proved by Kiihne (1865) from the spectrum of muscles
(diaphragm) that had been entirely freed from blood by prolonged
washing with saline. MacMunn (1884-87) afterwards investi-
gated the muscles of different classes of vertebrates and inverte-
brates, and found that they exhibited a variety of absorption
spectra, due in his opinion to a group of pigments which he
named myohae matin. According, however, to Hoppe-Seyler and
Levy (1889) myohaematin is only a decomposition product of the
haemoglobin of the muscle. That haemoglobin is an intrinsic
product of the muscle cells or fibres is shown by the fact that it
exists in the muscles of invertebrates which have no haemoglobin
in their circulating fluids.
When the muscles of recently killed animals are treated with
boiling water the proteins coagulate, and the extract contains all
the soluble nitrogenous and non-nitrogenous organic substances of
the muscle. The first form a group of compounds which represent
different disintegration products of the proteins (creatine and
creatinine — zanthine, hypozanthine, carnine, uric acid and urea—
taurine and glycocoll). The second belong to the carbohydrate
group and its derivatives (glycogen, dextrin, glucose, maltose,
inosite, lactic acid, and lactates).
Quantitatively speaking, creatine and glycogen (which we have
already discussed, Vol. II. pp. 391, 310) predominate among these
groups of substances in the muscle.
Nothing definite is known at present about the physiological
importance of creatine and creatinine. They are certainly formed
by katabolic processes from the proteins in the muscle. In fact
they are more abundant in muscles which have been overworked
previous to the death of the animal (Monari, 1888) than in muscles
analysed after rest. Nawrocki and Sarokin, however, found that
the creatine-content is no larger in tetanised than in resting
muscle. Another striking fact was discovered by Demant (1879)
in Hoppe-Seyler's laboratory. In the muscles of pigeons starved
until they have consumed all the non-nitrogenous reserve materials
contained in the muscles, so that metabolism proceeds at the
expense of protein disintegration, the content of creatine and
creatinine amounts to three times that in normal pigeon muscle.
Glycogen and its derivatives are the principal reserve material
i GENERAL PHYSIOLOGY OF MUSCLE 39
utilised by the muscle during work. Nasse (1869) first poiuted
this out, as he found that the glycogen content of muscle is in
inverse ratio with the work performed. The best evidence for it
lies in the fact that all muscles prevented from working by section
of their nerves or tendinous attachments contain an excess of
glycogen, as compared with the symmetrical muscles that have
remained intact (MacDonnel, Chandelon, Manche, Weiss, E.
Krauss). At the same time it is a striking fact that muscular
glycogen diminishes far more slowly than hepatic glycogen in
fasting (Weiss, Aldehoff, Luchsinger) ; this is not due to the fact
that the liver normally supplies the muscles with glycogen, since
even when the liver has been excised the glycogen-content of the
muscles can be increased by feeding with cane-sugar. Muscles
have therefore an amylogenic and glycogenic function which is
perfectly independent of that of the liver (Prausnitz).
Helmholtz (1845) observed that during tetanus the extractives
of muscle which are soluble in water diminish, while those soluble in
alcohol increase, which depends at least in part on the reduction of
glycogeu and increase of glucose coincident with muscular activity.
Lactic (or sarcolactic) acid is an important constituent of
muscle; during rigor mortis it may amount to O'l-l'O percent
(Bohm, Demant). Living, resting muscle has a neutral or feebly
alkaline reaction, while rigid muscle has a distinctly acid reaction.
Muscle plasma, too, is first neutral or feebly alkaline, and becomes
acid after coagulation. The cause of this reaction has been the
subject of much controversy. Some authors have tried to replace
Liebig's early theory (1847) that it is due to a development of
lactic acid, by the hypothesis that the acidity of muscle is caused
exclusively by mono-phosphate of potassium. This can only be
proved by excluding the formation of lactic acid during the life of
the muscle. It may, however, be assumed that the free lactic
acid, acting on the potassium bi-phosphate of normal living
muscles, is converted into potassium lactate, by reduction of the
neutral into acid phosphate, which may partly account for the
acidity of dead muscle.
It was formerly, and is still sometimes held (Araki), that
lactic acid arises from disintegration of the glycogen. But this
is obviously controverted by the work of Bohni and of Demant.
Bohm (1880) showed that the amount of lactic acid formed during
the death of the cat's muscle is in no relation with the glycogen
content, since the latter gradually disappears during starvation,
while the proportion of lactic acid is not less than normal. Demant
(1879) showed that glycogen entirely disappears in the pectoral
muscle of pigeon after eight days of fasting, while there is a free
formation of lactic acid. From these results they concluded that
the mother-substances of the lactic acid formed by muscle must
be sought in its proteins.
40 PHYSIOLOGY CHAP.
Lactic acid has been proved experimentally to be one of the
normal katabolites of muscle, formed not only in dead but also
in living muscle during rest, and still more during work. On
artificially circulating defibrinated blood for three hours through
the muscles of the lower limbs of a dog, the amount of lactic acid
that can be extracted from the blood that has repeatedly passed
through the resting muscle amounts to about 1-5 grms. Tetanisa-
tion of living muscle certainly increases lactic acid formation ;
the amount of lactates present in the blood (Spiro) or excreted by
the kidneys (Colasanti and Moscatelli) increases. The muscles
do not, however, acquire an acid reaction, because the lactic acid
is given off as fast as it is formed to the blood - stream, where
it is saturated with alkali. When, on the contrary, a group of
muscles previously cut off from the circulation is tetanised they
become acid owing to accumulation of lactic acid, while the
corresponding, non-excited muscles of the opposite side remain
neutral or alkaline and contain little lactate (Marcuse, Werther).
In excised frog's muscle slight electrical excitation, which causes
no violent contraction, suffices to convert the neutral into an acid
reaction (Gotschlich).
From these and other experimental researches it may be con-
cluded that the formation of lactic acid is associated with the life
of muscle, and not with its death, as many believe. The con-
vincing evidence of this lies in the fact that when a muscle with
normal circulation is tetanised, then excised, it forms less acid
during its death than the corresponding muscle which was not
excited, showing that the mother-substance of the acid has been
used up, and that the amount of acid developed by a muscle in
dying corresponds with the quantity of mother-substance con-
tained in it.
In addition to protein and glycogen the fats may be regarded
as reserve materials; these are found not only in the inter-
muscular connective tissue, but also within the fibres and in the
sarcoplasm, and especially in the fibres of the red muscles, in the
form of droplets which give them a turbid appearance (Ph. Knoll).
Some of these droplets stain black with osmic acid, others remain
unstained and probably consist of lecithin. During starvation
they disappear, and return on feeding. In morbid degenerative
changes, as after phosphorus poisoning, the amount of fat in-
creases enormously, and it must therefore be due not to storage,
but to regressive metamorphosis of the proteins.
The part played by the fats in muscular metabolism is un-
known. The small fat-content of normal fibres is no reason for
regarding it as unimportant, since in all probability fat does not
accumulate normally because it is consumed as soon as formed.
According to Bogdanow the fat of muscle-substance is richer in
volatile fatty acids than that of the interniuscular connective
i GENERAL PHYSIOLOGY OF MUSCLE 41
tissue. It seems to us uot improbable that tbe development of
latty acids contributes to the acidification of muscle during its
death.
The inorganic compounds of muscle are water and the salts
contained in the ash.
The amount of water in human muscle is not less than 70 per
cent and may rise to 72-74 per cent. It varies to some extent
in different classes of muscle. Generally speaking, embryonic
muscles and those of young persons are richer in water than
those of adults and old people. During starvation the water
diminishes considerably ; it is increased, on the contrary, by work,
which suggests that during the discharge of the energy accumu-
lated in the muscle water is one of the end-products of the carbo-
hydrate metabolism.
Of the mineral salts contained in the ash of muscle the pre-
dominance of potash over soda among the bases, and of phosphoric
acid among the acids, is remarkable. According to Bunge the
ash of 100 parts of muscle contains on an average :—
K,0 . . . 4-407 Fe.,03 . . . O057
Na.,0 . . . 0-790 P.,63 . . . 4-612
C.,0" . . . 0-079 01 ... 0-682
MgO . . . 0-396 S03 . . . 0-100
It is certain that in living muscle these mineral compounds are
not all present in the form of simple solutions, but are in organic
combination. The sulphuric acid is formed from the sulphur of
the proteins during combustion. The phosphoric acid is only pre-
existent to a very small extent in living muscle, the greater part
arises from the combustion of the lecithin and the nucleins.
The ferric oxide results from the disintegration of the muscular
haemoglobin.
The gases of muscle consist in a considerable amount of carbon
dioxide and traces of nitrogen. The mercury pump has failed
to separate any trace of oxygen from muscles when carefully
washed free of blood, obviously because the oxygen combined with
the haemoglobin is dissociated and carried away in the washing.
According to Hermann (1867), 2-74 per cent free, and 1*95
per cent combined C02 can be extracted from muscle which is
bled, minced up, and triturated previous to the onset of rigor.
Stiutzing found that on prolonged boiling of muscle another
substance decomposes, which gives rise to a free development of
CO.,. It is probable that the carbonic acid developed in tetanus
and" during rigor is derived from the same substance as is decom-
posed by boiling.
We have already reviewed the principal facts of muscular
respiration (Vol. I. p. 393). The important fact is that the gas
exchanges of muscle are exaggerated during activity, i.e. both
42 PHYSIOLOGY CHAP.
elimination of C02 and absorption of 02 are increased ; but the
CO
value of the respiratory quotient — p increases also, because the
2
output of C09 is greater than the intake of 0., (Ludwig and
Sczelkow, 1862, Ludwig and Schmidt, 1868, v. Frey, 1885).
Hans Winterstein (1907) demonstrated that the rigor mortis
of mammalian muscle is essentially due to the loss of oxygenation,
owing to arrest of the vascular circulation ; it is thus an asphyxia
phenomenon. In fact, if a mammalian muscle, excised from the
body, is kept in Einger's solution at an oxygen pressure of 2-4
atmospheres, at a temperature of 36-38° C., its excitability may
be preserved for twenty-seven hours after dissecting it out, with
no appearance of rigor. If rigor sets in, it may be kept off by
successive strong doses of oxygen. When it is once established,
however, further oxygenation is useless.
VIII. There can be no doubt that the chemical processes
which come into play during the activity of muscle are the source
of the physical energy which the muscle develops, and the external
mechanical work which it performs. This is a direct corollary to
the law of the conservation of energy. Muscular excitation is the
most classical instance in the living world of the explosive dis-
charge of energy, i.e. the rapid transformation of potential chemical
energy iuto kinetic energy, in the form of work, heat, and
electricity. As in the steam-engine the mechanical work depends
on the combustion of coal, so the mechanical work of the muscular
machine results from the katabolic processes of disintegration and
oxidation of the organic compounds which build up the muscle.
Having now discussed the chemical changes that go on in
living muscle during rest and in activity, we must next turn to
the problem of the origin of muscular energy, that is, which of the
food stuffs introduced into the body and assimilated by the muscles
furnishes the necessary energy for their activity.
Starting from the fact that proteins represent the chief con-
stituents of muscle, and that a full meat-diet increases the work-
capacity of muscle, while a diet poor in protein depresses it,
Liebig (1857-70) assumed that the source of muscular energy
must be sought in the proteins. There can be no doubt that the
nitrogenous exchanges of muscle are very active, much protein
being consumed both in rest and in activity ; but Liebig showed
no direct experimental proof that the activity of muscle depends
mainly upon increased protein metabolism.
Bischoff and Voit (1860) thought the question could be solved
by comparing the urea content and the total nitrogen content
of urine during hard muscular work, with that eliminated during
rest, the same quantity and quality of food stuffs being ingested.
In both man and dogs they obtained a nitrogenous equilibrium after
a few days of uniform dieting, i.e. equivalence between the nitrogen
r GENEKAL PHYSIOLOGY OF MUSCLE 43
introduced and that eliminated with the urine. They found that
this equilibrium was not much affected by days of rest, as com-
pared with working days, i.e. no perceptibly greater quantity of
nitrogenous substances was consumed during work.
This result was confirmed by the later and more accurate
researches of Voit (1870-81). He found not only in dogs kept on
a constant diet, but in starving animals also, that the amount of
nitrogen excreted was not much increased by work, and that the
increment was in no case in ratio with the amount of work done.
Experiments made on themselves by Fick and Wislicenus
(1685) supported this result. They climbed the Faulhorn, 1906 m.,
in six hours, during which time they collected all the urine passed.
During the twelve hours preceding the climb and on the ascent
they took no nitrogenous foods, and lived solely on starch, fat, and
sugar. From the amount of nitrogen contained in the urine they
deduced the amount consumed during the climb. They further
calculated the amount of mechanical work accomplished by the
leg muscles of each, multiplying the body-weight by the height of
the mountain ; the work done by the other muscles was not calcu-
lated. From the combustion heat of the protein consumed during
the ascent they calculated the maximal yield that could be
obtained if the whole of the protein in the body were burned up.
The result showed that the work done on the climb far exceeded
that which could be performed by the decomposition and oxida-
tion of the protein consumed. From this they concluded that the
non-nitrogenous substances introduced with the food or stored in
the body as reserve materials supply energy which can be utilised
during work.
The direct proof that it is principally the non-nitrogenous
substances (carbohydrates and fats) that are consumed during
work is derived from experiments on the respiratory gas-exchanges,
which show that while the elimination of nitrogen does not
increase perceptibly the excretion of carbonic acid and absorption
of oxygen do increase considerably during work (Pettenkofer and
Voit, 1866, and others). This agrees perfectly with what was
stated above in regard to the consumption of glycogen and fat in
muscular activity.
What part, then, does the protein of muscle play in the per-
formance of its functions ? Since muscle consists principally of
proteins, which are the fundamental substrate of all living tissues,
it must be recognised that these substances play an active part in
all the internal processes that go on in muscle.
Traube suggested that the proteins of living matter have the
task of carrying oxygen to the nou- nitrogenous combustible
materials, but are not themselves decomposed. This agrees with
PHiiger's general theory of the oxidation processes of the animal
body, according to which the intra-molecular oxygen, chemically
44 PHYSIOLOGY CHAP.
bound up in the molecules of living matter, is the source of the
disintegrative and oxidising changes that go on in all the tissues.
We may therefore assume that the proteins of muscle absorb and
combine with oxygen during rest, and pass it on during activity
to nitrogen-free molecules, while they once more take up fresh
oxygen in the resting period which follows. On this hypothesis
the proteins of muscle fulfil the same function as an enzyme
during work. But the inadequacy of this explanation is evident
from the fact that muscle, independently of rest or activity, is the
seat of an active nitrogenous metabolism, which must therefore be
heightened during work. Further, intense muscular work is
possible on an exclusively flesh diet. Voit showed that dogs can
be kept alive under normal conditions on an exclusive diet of
meat. In his latest researches (1892) Ffliiger fed a great Dane
of 30 kgrm. for nine months on horseflesh, which was almost free
of fat, and made it do hard work for weeks by dragging a heavy
cart for 13 km. in two to three hours. During this time the
animal remained exceptionally well and vigorous. Under these
conditions almost the whole of the energy developed in the
animal's muscles must be derived from disintegration of protein,
since the small quantity of glycogen and fat ingested is negligible.
Nevertheless, on comparing the amount of nitrogen given off
by the animal in periods of work and of rest, Pfliiger could only
confirm the fact that it did not vary conspicuously, and that the
increase was never in proportion with the work performed.
To explain this fact he assumed that the excretion of nitrogen
does not increase definitely after work, because though the muscles
consume more protein, other tissues consume less, by a sort of
adaptation due to the lesser amount of protein circulated.
Verworn, however, pointed out that this hypothesis cannot
explain Voit's observation on the dog, that even in the fasting
state when the amount of circulating protein at the disposal
of the muscles and other tissues is minimal, nitrogen elimination
does not increase proportionately with hard work (making a wheel
revolve on its axis).
Pfliiger suggested later that the increased disintegration of
protein effected by the muscle during work does not show a
larger excretion of nitrogen in the urine, because the nitrogenous
waste products are regenerated synthetically into the complex
molecules of protein, by combining with non-nitrogenous atoms
lost during the work, at the expense of nutrition, or of the reserve
materials. In other words, it is possible and even probable that
the nitrogenous products of proteolysis, which is increased in
muscular work, do not leave the body like the non-nitrogenous
products, which are excreted principally in the form of carbohydrate
and water, but are stored up and partially utilised again in the
synthetic regeneration of protein : this is to some extent analogous
i GENERAL PHYSIOLOGY" OF MUSCLE 45
to the process by which the proteoses and peptones are regenerated
into protein by the intestinal epithelium, and the amino-acids
(which are the final products of the digestive decomposition of the
proteins) restore and build up the tissues, after being reabsorbed
into the lymph and blood. So that muscular proteolysis, which
is stimulated or increased by work, in its turn promotes the
genesis of protein — and consequently the quantity of nitrogenous
products in the urine does not materially increase during work.
This hypothesis appears to us acceptable in view of recent
researches on the complex structure of the proteins which build
up living matter, and the different cleavage products that can be
isolated by the action of enzymes. Pick's studies (1899) on the
proteolytic products into which fibrin can split under the action
of pepsin are of first importance. Of these products he was able
to isolate :—
(a) A proteoalbumose, which contains no carbohydrate group, but
has much tyrosine and indole, gives off no glycocoll among its
decomposition products, and holds sulphur only in unstable
equilibrium.
(&) A heteroalbumose, which contains no carbohydrate group
and hardly any tyrosiue and indole, is rich in leuciue, with some
glycocoll, and holds sulphur only in unstable combination.
(c) A deuteroalbumose, which contains no carbohydrates.
(V) Two deuteroalbuminoses rich in carbohydrates.
(e) Two peptones containing carbohydrates.
The importance of these results consists in the fact that it is
comparatively easy to separate the protein molecule from the
carbo-hydrate group (which is oxidised during muscular work)
without loss of the fundamental chemical properties of the pro-
teins, which therefore retain their capacity for synthetic regenera-
tion into protein under the influence of the anabolic activity of
the living tissue -cells. If we admit an anabolic proteogenic
activity in the intestinal epithelium, it seems reasonable also to
assume that it exists in muscle (Vol. II. p. 328).
IX. We have said that muscular contraction is the most
classical and hence the best investigated instance of an explosive
discharge of energy in the living world. The potential chemical
energy stored up in the muscle is converted during excitation
into kinetic energy, which appears in the forms of mechanical
work, heat, and electricity, each of which must be considered
separately.
The work done by muscle is measured by the product of the
weight raised by the muscle into the height to which it is raised,
w x h. If, therefore, the muscle contracts without lifting a weight
or overcoming any resistance, it performs no mechanical work.
This supposition is, however, purely theoretical since the muscle
always has to carry its own weight, which may indeed be reduced
46
PHYSIOLOGY
CHAP.
to a minimum if the muscle is laid horizontally on mercury, after
first dipping it into oil to diminish the surface friction.
Again, the muscle does 110 work when it is loaded with such
a heavy weight that it is unable to raise it. In the first case the
energy developed by the excitation is exhausted in the contraction,
in the second in the tension of the muscle ; but in both cases
no external mechanical work, but only internal mechanical work
is done.
On calculating the external work done by a muscle in raising
regularly increasing weights, it is found that it increases quickly
at first, and then more slowly, until it reaches a certain maximum,
after which it diminishes again and finally becomes nil on reaching
the weight which the muscle is unable to lift.
Fig. 26 illustrates
grms. 0
• i 50
.. 100
.. <50
.. 200
.' 250
" 300
.. 350
•i 400
.. 450
>, 500
min. 5
6
5
4
3
2 5
2
grin. mm. 0
.. 550
» .. 700
.. 900
,.«000
N<000
•> i. 900
" •• 675
ii ., 800
•• ,,675
,, BOO
Fio. 26. — Diagram showing work done by muscle — frog's gastrocnemius. (A. D. Waller.)
these experimental results, which can be verified on every muscle
that is loaded and stretched before contraction, or merely while it
contracts.
It may thus be stated that there is a given weight for every
muscle, at which it reaches its maximal yield of work, and that
with diminution or increase of the load the work becomes
gradually less till it finally reaches zero. This law of course
applies also to all groups of muscles which co-operate in the work
performed.
The resistances encountered by the different muscles concerned
in complicated action vary ; the degree of shortening which they
undergo varies also. Generally speaking, the strength of a muscle,
i.e. the weight it is able to lift, increases in proportion to its
diameter, that is, the number of fibres it contains. Since work is
the product of the weight and the height to which it is raised, it
follows that, other things being equal, the work of a muscle is in
proportion with the product of its length and cross-section, viz.
GENEKAL PHYSIOLOGY OF MUSCLE
47
the volume or mass of the muscle. These relations between the
size of a muscle and the energy it is capable of developing :
between the length of a muscle consisting of parallel fibres and its
degree of contraction ; and finally between the weight of the
muscle and the useful work it is capable of yielding — were all
noted by Borelli in the early half of the eighteenth century, and
were fully considered and cleared up by Weber in 1845.
The absolute force of a muscle is measured by the minimal
weight that it is unable to lift under maximal excitation (Weber).
Since it is proportional to the cross-section or diameter of the
muscle, a universal standard is obtained by calculating the absolute
force of a square centimetre of the muscle section. The absolute
force of the muscles varies in
different animals and even in
different muscles of the same
animal. It varies for a square
cm. of frog's muscle between 7
and 8 kgrms. (Henke and Knorz)
or even 9 and 10 k grins. (Koster,
Haughton).
Attempts have also been made
to determine the absolute force
of a sq. cm. of human muscle by
measuring the cross -section on
a dead subject of the same
physique and muscular develop-
ment as the subject of experi-
ment. Here, again, the values
obtained were very different :
2-8-3 kgrms. (Eosenthal), 5-10
kgrms. (other experimenters). It
should be noted, however, that these experiments on man were made
not with artificial tetanisation, but with a voluntary yield of work,
in which the energy developed may be double, or at least a third
more than that developed on stimulation with a tetanising current.
From the clinical point of view, investigation of the relative
strength of certain groups of human muscles is far more practicable.
The dynamometer is usually employed for this purpose. It consists
of a strong oval steel spring, which is compressed by the hand, while
an index moves along an empirically graduated scale to indicate
the amount of compression and thus of the power developed in the
group of muscles which come into play when the hand is closed.
The figures obtained by this instrument are, however, of little
value, since they can be modified by practice, attention on the part
of the subject, and, above all, degree of voluntary effort, which may
vary considerably, even independently of the conscious will of the
subject.
FIG. 27.— Dynamograph. (A. D. Waller.)
48
PHYSIOLOGY
CHAP.
Morselli added a contrivance for air- transmission, which made
it possible to record the compression of the spring upon a revolving
cylinder, and which transformed the dynamometer into a dynamo-
graph, by which the tracing of a series of maximal voluntary
contractions of the flexor muscles of the hand, at regular intervals
measured by the beats of a metronome, can be recorded. Such
FIG. 28.— Tracing from Waller's dynainograph, to show elli-cls of fatigue and recovery.
curves show not only the comparative force of the muscles, but
also their resistance, or the ease with which they become fatigued.
Still more simple is Waller's dynarnograph (Fig. 27), in which
the pull of the hand upon a strong steel spring is registered
directly by a long lever. Fig. 28 shows the tracing of six groups
of maximal contractions, at regular intervals ; between each group
Fn.. '_".!. — Mosso'x c] i;oi;Tapli.
there is a uniform pause for rest. The drop in the
line uniting the apices in each group shows the
fatigue of the muscle ; the return to the original
executed height in the next group represents its
recovery during rest.
The dynamographs of Morselli and Waller are
based on the isometric method, and consequently record the maxi-
mal tensions of the flexors of the hand, and the correlative internal
work ; Mosso's ergograph (Fig. 29) is an instrument based on the
isotonic method, and it records the maximal contraction of the
GENEEAL PHYSIOLOGY OF MUSCLE
49
flexors of the middle tinger, on loading with a given weight, and
therefore the external work (in kilogranimetres) performed during
maximal voluntary effort. The arm is placed in the supine position
and h'xed to a horizontal support. A leather ring is applied to the
middle finger, which carries a string that runs over a pulley and is
weighted at the end. Raising the weight displaces a lever, the
point of which records the amount of flexion of the finger. Mosso
attached a supporting screw or stop to the indicator of the ergo-
graph, by which the flexor muscle of the finger can be relieved of
its load during rest, and the weight only pulls on the muscle
during its contractions.
FIG. 30. — Two tracings of different types from Mosso's ergograph, taken from two boys of the same
age and habit ; in both a weight of 3 kgrms. was lifted every two seconds.
The most striking results obtained in the earliest researches
of Mosso and his collaborators (1890) by the study of the ergograph
tracings in a series of voluntary maximal efforts at regular intervals
are as follows :—
(a) There is no common type for the ergograph fatigue curve,
but each individual has a personal type — i.e. under good physio-
logical conditions, in a state of repose, with a given load and
definite rate, each individual — even at long intervals — exhibits
the same fatigue curve, although the amount of external mechanical
work may vary widely (Fig. 30).
(6) The personal type of the fatigue curve persists even when
the fatigue is produced, not by voluntary effort, but by rhythmic
electrical stimulation of the nerve or muscle.
(c) Pronounced mental fatigue or fatigue of all the muscles of
VOL. in E
50 PHYSIOLOGY CHAP.
the body produces rapid exhaustion on the ergograph, even if the
curve is obtained by electrical excitation.
(oT) Ergograph work may alter the elasticity of the muscle,
increasing or diminishing it ; in certain individuals it may excite
contracture, which is the more readily produced in proportion with
the strength and frequency of the stimulus, and the weight the
muscle has to raise.
The ergograph curve depends on the combined effects of
fatigue of the nerve-centres and fatigue of the muscle, though the
latter always predominates. " The characteristic phenomena,"
Mosso writes, " are peripheral, since the muscle exhibits its char-
acteristic fatigue curve even with artificial stimulation. ... It is
not the will nor the nerves, but the muscle that is weakened after
arduous brain-work."
Maggiora subsequently brought out the great importance of
the varying conditions under which external mechanical work is
performed on the ergograph :—
(a) There is a certain weight which elicits the maximum of
utility ; with weights below a certain value, no sign of fatigue is
perceptible.
(6) With every load, the slower the rhythm of contraction the
more external work can be performed, and the more the onset of
fatigue is delayed. For any given weight there is a rate at which
the contractions can proceed for a long time with no trace of
fatigue.
(c) If a muscle is contracting at a given rate slow enough to
allow of its complete recovery at each contraction, and the load is
then doubled, it is not sufficient to reduce the rate to half its
original frequency in order to obtain the same yield of mechanical
work from the muscle.
(d) The interval which must elapse between two ergo-
graphic curves in order to obtain normal fatigue curves during
the whole day is from 1| to 2 hours. The weight of the load is a
matter of indifference between certain limits (2-4 kgrms.).
(e) The work performed by a muscle that is already fatigued is
far more injurious to that muscle than a greater amount of work
performed under normal conditions.
In these studies Mosso, Maggiora, and other investigators, in
calculating the work effected by the muscle, neglected the end
part of the tracing — which consists of low, long-drawn-out con-
tractions. Lombard (1890) investigated this terminal phase,
and discovered that when the ergogram appeared to stop, it
usually continues as a new series of contractions, in which the
rise and fall of the curve were approximately regular. According
to Lombard these periods are only to be seen in the voluntary
ergogram, and are due to spinal fatigue.
Owing to the ease with which the ergograph can be used it is
i GENERAL PHYSIOLOGY OF MUSCLE 51
employed by psychologists and clinicians as well as physiologists.
The method is universally allowed to make functional isolation of
a limited group of muscles possible ; average weights (.'5-4 kgrms.)
should be used to ensure the better graduation of the work and
curves that are neither too short nor too long ; and it is assumed
that the output of work with this load and under the right experi-
mental conditions for the ergograph is a true expression of the
physiological capacity of the muscle in relation to the weight.
Above all, psychologists and psychiatrists sought - - on the
strength of Mosso's results, and obviously going farther than he
originally attempted — to emphasise that both central and peri-
pheral or muscular fatigue were shown in the curve. Kraepelin
affirmed that in the ergographic curve the height of lift expresses
muscular fatigue ; the number of contractions, on the contrary,
gives the measure of mental fatigue. This proposition includes
the conception that the cessation of the ergograph curve is due to
muscular exhaustion, i.e. functional incapacity of the nerve-muscle
apparatus, caused in all probability by the curarising action
of the fatigue products, owing to which the psychical impulses
encounter an increasing resistance.
In fact, the experiments of many workers upon the influence
on the ergograph curve of different external conditions (as
temperature, pressure, time of day, etc.), as well as of many internal
states (state of nutrition, period of digestion, special diet, exhibi-
tion of stimulating agents, of organic extracts, etc.), have always
yielded very uncertain results. The output of external mechanical
work never varied perceptibly from the ordinary physiological
limits.
U. Mosso attempted by a series of experiments to determine
whether the administration of foods — sugar in particular — could
restore the potential capacity of the muscle depressed by work.
The most definite conclusion was that the action of sugar was only
beneficial with the ergograph when the individual was in a condition
of extreme fatigue.
Generally speaking, the ergograph is not suitable for solving
these questions — Zuntz and his pupils utilised it, but only as an
index to the state of fatigue on certain occasions when the subject
was executing a definite piece of work that involved the musculature
of the whole body. If the subject is made to do a known quantity
of work in the interval between the ergographic records, a per-
ceptible recovery is seen in the next ergogram if small quantities
of food are administered.
The value of the ergograph curve as an index of muscular
fatigue on the one hand and mental fatigue on the other, as
Kraepelin has used it, is very doubtful.
In 1898 Treves, working in the Physiological Institute of
Turin on the laws of muscular activity in man and animals, made
52
PHYSIOLOGY
CHAP.
certain modifications in the methods of investigation, and obtained
results which frequently contradicted previous conclusions. His
first experiments were carried out on the rabbit, with direct and
indirect excitations of the muscles once a second. The tendon of
the muscle was not separated from its insertions, but the resistance
cjr. 1150
Fio. 31. — Ergogram of rabbit's gastrocnemius, loaded with 1150 gnus, (maximal weight). The
sciatic was excited every two seconds. (Treves.)
of the weight was transmitted to the muscle by means of the
natural bony lever of the rabbit's leg, the end of which is connected
with the writing point of the ergograph. He used maximal
tetauising stimuli of very brief duration, in imitation of voluntary
impulses. Before taking the ergograph curves, Treves ascertained
at what weight the muscle was able to contract, with maximal
FIG. 32.— Ergograph tracings from same muscle as preceding figure. The initial maximal weight was
gradually diminished so as to determine the maximal terminal weight at which the rhythmic
lifts no longer make a descending curve, but form a horizontal line (constant phase of ergogram).
(Treves.)
excitation, so as to serve up maximal work. As he did away with
the supporting screw of Mosso's ergograph, the weight pulled
continuously upon the muscle, and not merely during contraction.
Under these conditions Treves obtained an ergogram in which
the height of the contractions regularly diminished, but more and
more slowly, till they became almost inappreciable, and below
GENERAL PHYSIOLOGY OF MUSCLE
53
this they showed no tendency to further diminution (Fig. 31).
On the usual interpretation of ergograph curves it would be said
that the muscle had become incapable of any further work at this
point. But this is not the case ; the muscle is still capable of
serving up a considerable amount of external work. For if the
weight is gradually reduced, the height of the contraction again
increases until a new maximal weight is found which yields
Fn:. 33.— Ergograph tracing of rabbit's gastrocnemius, after ten minutes' rest, during phase
of constant work. (Treves.)
the maximum of work (Fig. 32) and corresponds to about
400 grms., i.e. much less than the original weight, which was
1150 grms. If the rhythmical maximum excitation is continued
with this new load (which may be called the terminal maximal
load), an endless series of contractions is obtained, which correspond
with the production of constant work. The series of contractions
following on a falling curve exhibits similar constancy, irrespective
of the load which is carried. Fig. 32 reproduces a few cm. only
of the tracings obtained with different loads in testing for the
Fin. 34.— Ergogram of rabbit's gastrocnemius, loaded with 600 grms., after twenty minutes' rest,
during phase of constant work. (Treves.) Before resting the muscle gave at each lift a
constant yield of 400 grms. x 4 mm. = 1600 grm. mm. After resting the maximal work was
600 grms. x 11 mm. =6600 grm. mrn.
terminal maximal load — in the second phase of the ergogram.
This constant phase may preserve its regularity at a rhythm of
1 sec. for over 2000 consecutive contractions, each representing
work that may amount to 2500 gr. mm.
If the muscle is allowed a longer or shorter pause for rest
during the period of constant work, the maximal work of which it
is capable at each contraction increases again, in proportion as the
resting-pause has been longer. This partial recovery of power is
shown in the capacity of the muscle to trace a new ergogram with
54 PHYSIOLOGY CHAP.
diminishing heights of contraction which is followed by the
constant phase with uniform values (Figs. 33 and 34).
If the falling portion of the ergogram is obtained with a
sub-maximal load, the tracing passes into the constant phase
without altering the weight, in which case each contraction
represents a sub-maximal yield of work (Fig. 35).
The level of constant work may be maintained for several hours
without any sign of the characteristic modifications of fatigue
Fn;. 3.x — Kilogram of gastrocnemius showing decreasing and constant phase, at a
sub-maximal load. (Treves.)
(Fig. 36), but finally there comes a moment at which the muscle can
no longer yield any mechanical work owing to the gradual onset of
rigor.
In the ergogram of the gastrocnemius obtained with electrical
stimulation and an initial maximal load, the curve of the contraction
heights sinks rapidly to zero, or to a very low level., because after
a certain number of contractions the load becomes super-maximal.
If the weight could be gradually adjusted as the muscle weakens
so as to be maximal at each fresh contraction, the ergogram would
show no intervening stage of complete or almost complete cessation
of work, which is solely due to imperfect mechanical conditions.
A more important curve would stand out as a whole — namely the
FIG. 36.— Ergograph tracing of rabbit's gastrocnemius (phase of constant work) after two hours'
rhythmical maximal excitation. (Treves.) The tracing shows a slight irregularity of the base
line of the contractions, but the work remains fairly constant.
work curve, represented by a series of rhythmical contractions
executed under conditions of maximal work. Treves endeavoured
to approximate to such conditions in his experiments, and con-
structed a diagrammatic work curve} the course of which recalls
the form of a muscle twitch, with an ascending and a descending
phase, passing gradually into the period of constant work.
Treves was the first to apply these methods of research to the
human subject. He did away with the support of the ergograph
lever, and made the subject lift a weight of 4-5-6 kgrms. (accord-
ing to the individual) every two seconds by a voluntary maximal
effort. In consequence the constant level was always obtained on
GENERAL PHYSIOLOGY OF MUSCLE 55
the ergogram, and forms an essential part of it. This proves that
supporting of the ergograph lever creates artificial work conditions,
which, together with the variations in elasticity and tone which
the muscle suffers during work, cause a more or less rapid
decline in the successive contractions, and shorten the ergogram
prematurely.
In extending his investigation to voluntary work, Treves found
it necessary to alter his system of loading, and to apply the
principle of maximal loading in this case also — that is of gradually
altering the weight as the muscular power declines. In this study
he employed the flexor muscles of the forearm, and invented a
new ergograph for the purpose which may be studied in his
original memoir.
A minute analysis of Treves' results is beyond the scope of
this text-book. We must confine ourselves to a few of the most
important principles that can be deduced from them :—
(a) During voluntary work on the ergograph the height of
contraction remains constant so long as the conditions of work are
favourable, and above all so long as the load is not excessive.
(6) The maximal load that can be raised by voluntary effort
corresponds with the load which necessitates the maximum of work.
(c) The maximum load diminishes gradually in a hyperbolic
curve till it reaches a value which varies with the rate of work, but
is practically constant. The curve of voluntary work, like that
obtained by artificial stimulation, consists of two phases — a
descending and a constant part. The differences seen in the two
curves arise from the fact that in the case of work elicited by
artificial stimuli the stimulus is constant ; in voluntary work, on
the contrary, the effort varies since it diminishes independently of
the will, according to the resistance experienced in carrying out
the movement.
(d} The ergograph tracing consists of a series of vertical lines
approximately equal in height, with no feature characteristic of
the individual or of the experimental conditions. The true
ergogram is the line according to which the work diminishes with
the maximal load.
(e) The main factor which determines the rapid fall of the
curve with a constant load is the appearance of unfavourable
mechanical conditions. To obviate this the muscles must be left
perfectly free to contract, and the contraction of other muscles
connected with those under investigation must not be hindered.
It suffices to see that the graphic apparatus records only the
movements of the bony lever in question. Further, the normal
conditions under which the muscle acts must be respected, and
the gradual unloading of the muscle during contraction permitted,
as would happen by the displacement of the bony lever on which
the muscle naturally works.
56 PHYSIOLOGY CHAP.
(/) The will as a psychical factor has no influence on the fall
of the curve with a constant load. Directly the load is adjusted
the tracing is prolonged by an unlimited number of contractions
with a considerable production of work. All other hypotheses are
superfluous, on which the functional incapacity which appears in
the ergograph curve only with the constant load has been
explained by assuming a sort of antagonism between the height
and the number of the contractions.
(<?) In order to elicit the whole work of which a muscle is
capable, in regard both to time and to amount, care must be taken
that the muscle is always engaged in maximal work. At whatever
load the work begins, the time necessary for attaining a constant
level is always the same. Still the muscle working under the
influence of the will with sub-maximal loads economises part of
the materials at its disposal, and may accumulate a fresh supply.
(h~) Given uniform conditions, the value of the initial maximal
load is constant in the same person on different days, and the
height of the contractions varies but little. The work curves
vary very slightly in the amount of work that can be obtained
with the initial maximal load, the terminal maximal load, and,
lastly, the total amount of work.
(i) Fasting does not perceptibly alter the value of the initial
maximal load, but it accelerates the fall of the curve, and lowers
the value of the terminal maximal load considerably. Practice
and training, on the contrary, render the muscle capable of accom-
plishing much more work. After practice the initial maximal
load increases within limits, while the value of the terminal
maximal load increases from day to day, without, however, delaying
the fall of the curve to the constant level.
(A-) If the work is begun with the maximal terminal load
as determined by the previous experiments, the ergograph curve
forms a horizontal line. From this we must not conclude that
work under these conditions produces no appreciable fatigue in
the nerve-muscle apparatus. Fatigue, according to Treves, can
be studied simultaneously with the production of external work,
by determining the manner in which the nervous energy
diminishes. This is represented by the product of a given weight
into the time in seconds for which the weight can be held up by
the voluntary tetanus, continued to exhaustion, of a given group
of muscles. The line indicating the alterations of nervous energy
falls much more rapidly than that showing the variations of
the maximal load, and is in a marked degree independent of the
production of external work.
At the Fifth International Congress of Physiology at Turin
Treves proposed certain modifications of his original ergograph,
by which he wras enabled to control these observations and to
extend his research to the flexor muscles of the fingers (Fig. 37).
GENERAL PHYSIOLOGY OF MUSCLE
57
In the first place he investigated the conditions which determine
the spontaneous rhythm of contraction in voluntary ergograph
work. This rhythm depends essentially upon perception of resist-
ance, and not upon the amount of work accomplished by the
subject nor his state of fatigue.
Fie. 37.— Treves' new ergograph, in which the weight can be gradually reduced, to obtain a tracing
under constant conditions of maximal load and maximal work. Platform (a) to support the
forearm, and Mosso's recording apparatus (l>) are retained, but the contrivances for fixing the
arm and fingers that are not working are discarded. The arrangement for applying the weight
is altered. The cord passes over the pnlley d, the axis of which ends in a small crank which
revolves round the axis with the flexion of the middle finger. The lower part of the apparatus
serves to graduate the weight h and keep it maximal by running it along a metal bar one metre
long, which moves upon the axis k. It is obvious that the resistance opposed to the flexion of
the finger must decrease regularly, in proportion as the weight is farther from the point 100,
and nearer the zero at axis /,-.
The " constant phase " of the work curve was investigated by
other authors, and appreciated at its proper value. Some physio-
logists, however, while recognising the theoretical accuracy of the
isotonic method and Treves' application of the principle of the
maximal load, regard the isometric method as more practical and
better adapted to the study of voluntary muscular activity.
58 PHYSIOLOGY
CHAP.
Schenck justly remarks of Treves' method that, while it corrects
certain faults of the original ergograph, it introduces new corn-
plications. Obviously, as Treves himself admits, contractions
against different loads cannot be compared, because with variations
of the weight raised the energy of inner vation must also vary,
other conditions being equal.
Schenck resumed the study of muscular fatigue (1900) in
voluntary effort by applying the isometric method to the abductor
of the index finger. For this purpose he used the apparatus
devised by Fick in 1887 (Spannungszeichner), with the addition
of certain useful modifications. The subject, working by the
beats of a metronome, throws this muscle into maximal tension
for one second, and relaxes it for the next second. Each series
lasts for twenty-five minutes, and therefore consists of 750 alter-
nate contractions and relaxations.
The results of these researches may be summed up as follows :
The curve of the isometric contractions of the abductor indicis,
made with maximal voluntary effort, generally presents three
distinct stages :—
(a) In the first stage the tension which the muscle reaches in
the first contractions (which may exceed 14 kgrms.) diminishes
rapidly, and drops to about two-thirds (i.e. to 8400 grms.) after
about five minutes.
(&) In a second much longer period (about fourteen minutes)
the tension reached by the muscle is approximately constant.
(c) In a third period the tension drops again, but slightly (to
about 7700 grms.)to the end of the series, which may exceed twenty-
five minutes, without any further evidence of fatigue in the muscle.
If these results are compared with those of Treves, it is seen
at once that Schenck's first stage corresponds with the descending
phase of Treves' ergogram, and the second stage with the constant
phase which Treves obtained with the so-called " terminal maximal
load," with this difference, that in Schenck's method the maximal
energy of innervation is exerted from the beginning to the end,
while in Treves' method the energy of innervatiou gradually
declines. Accordingly, there is never any sign of fatigue after
the constant phase, and the third stage, which is prominent in
the isometric method, does not appear.
The functional constancy, that is, the comparative non-fatigu-
al >ility and inexhaustibility of muscle, contracting rhythmically
both with Treves' ergographic and Schenck's isometric method,
recalls the continuous rhythmic activity of the heart and respira-
tory muscles. This certainly depends on the blood-supply that
restores the muscle and nerve-centres as fast as they become
fatigued, and carries off the waste-products. In fact, when excised
muscles of the frog are used, the so-called fatigue curve passes
into complete exhaustion (Fig. 7, p. 12).
i GENERAL PHYSIOLOGY OF MUSCLE 59
This exhaustion depends on the absence of a proper supply of
oxygen and nutrient material to repair the waste of substance in
the active muscle and nerve-centres, and to the accumulation of
metabolites which paralyse the tissue owing to the arrest of the
blood and lymph circulation. Ranke, in fact, showed that, on
merely circulating a saline solution that contained no nutrient
restorative matters through fatigued frog-muscle, the signs of
fatigue disappeared. If, on the other hand, an aqueous extract of
the fatigued muscle of one frog were circulated through the fresh
muscle of another, fatigue phenomena at once set in.
Mosso continued these researches on warm-blooded animals,
and showed that transfusion of the blood of a fatigued into the
vessels of a normal dog induced symptoms of respiratory, cardiac,
and general fatigue in the latter. Clearly, therefore, the waste
products of muscular activity act as toxic substances, and cause
muscular fatigue and exhaustion.
The inexhaustibility of the flexor muscles of the middle finger
or the abductors of the index linger, under the experimental
conditions adopted by Treves, Schenck, and others, is not sur-
prising, and seems indirectly to confirm Eanke's theory of the
causes of muscular fatigue and exhaustion.
X. Only a small part of the potential energy liberated in
muscular contraction is used up in the form of external work ;
the other, considerably larger, part is converted into internal work,
which is accompanied by the development of heat.
It is a common observation that after vigorous effort or
repeated contractions of the muscles the temperature of the body
rises ; every one knows that muscular activity is the best way of
warming oneself in cold weather. In walking and running the
rectal temperature may rise some tenths of a degree. In tetanus
the fever may reach a high degree (45 '3° C., according to Wunder-
lich). The same is seen in strychnine poisoning (44° C., Vulpian).
On the other hand it has long been known that in a state of
absolute muscular rest, as in sleep, the internal temperature falls
about half a degree centigrade, and rises again rapidly on waking.
The mere immobilisation of an animal, or its curarisation, cools it
to 30-7° C. (Ricliet), and a subsequent injection of strychnine is
no longer able to evoke spasms or to raise the temperature, which
must therefore depend on the tetanising action of the strychnine.
Since the muscles represent about 40 per cent of the total body
weight in vertebrates, and after removal of the skeleton (which
can only develop a negligible amount of heat) certainly represent
more than 50 per cent, and since katabolism is more active in
muscle than in any other tissue, we are justified in assuming
that the muscles have a preponderating influence on the heat pro-
duction of the body, in comparison with that of all other tissues.
We shall elsewhere discuss thermogenesis and the thermal
60
PHYSIOLOGY
CHAP.
balance of the organism as a whole ; here we must confine our-
selves to the study of muscle as a thermogenic organ by the direct
examination of its temperature both during contraction and in the
resting state.
The first observations were made in 1835 by Becquerel and
Brechet. They attached one couple of a thermo-electric battery
to the biceps muscle of a human arm, while the second couple
was kept at constant temperature. After a few contractions the
temperature of the muscle was raised 05°, and after five minutes
of energetic alternate contraction and relaxation (working a saw)
1° C. Gierse (1842) was the first who noted in the dog, with the
v_
Fio. 38. — D'Arsonval's thermo-electric couples with sheathed junctions, to avoid the electrical
currents liable to be set up by the contact of two different metals with fluid. 1, Section of
finely-pointed conical tube of German silver, into which an iron wire has been soldered ; 2,
section of cylindrical tube of German silver, closed and pointed at one end at the junction
with an iron wire, and protected above this by a non-conducting sheath ; 3 and 4, a pair of
thermo-electric needles composed of two wires, iron and German silver, soldered together at
the points, and covered with an insulating varnish.
thermometer, that the cutaneous temperature of a limb rose during
the contraction of its muscles. Zienissen (1857) and Bee-lard
(1860-61) observed the same on man. The objection that the
rise of temperature depends on increased flow of blood to the skin
may be met by saying that the skin becomes warmer, but not
redder, during the contraction of the subjacent muscles. Another
objection, that the heating may depend on the hyperaernia of the
muscle during its contraction, is less easily met.
The ordinary thermometric or thermo-electric methods are used in investigat-
ing muscular thermogenesis. If the bulb of a highly sensitive thermometer
covered with a thick layer of non-conducting material (cotton-wool) to prevent
the dispersion of heat is applied to the human skin above the muscle to be
examined ; or better, if the bulb of the thermometer is inserted between the
muscles of the animal, it is possible to measure the alterations of temperature.
i GENERAL PHYSIOLOGY OF MUSCLE 61
Baudin has recently carried tlie construction of mercury thermometers with
small bull >s for physiological purposes to such perfection that he has obtained
a scale in which each degree is divided into fifty parts. But even with an
ordinary clinical thermometer, divided into tenths of a degree, it is possible
on reading the scale under the microscope to estimate differences of a hundredth
of a degree.
The thermo-electric method has, as compared with the thermometric
method, the great advantage of almost instantaneously indicating rapid
alterations in the temperature of the muscle. On the other hand it is more
difficult and delicate of application, and may lead to fallacies if not employed
very cautiously.
The thermo-electric method is founded on the following principle : If two
different metals united by two junctions are included in the circuit of a
low resistance galvanometer, the heating or cooling of one of the junctions
gives rise to an electric current, which deflects the needle of the galvanometer
in the positive or negative direction, in proportion with the rise or fall of
temperature in the first junction, if that of the second remains unchanged.
To investigate muscular therniogenesis it is best to take needle-shaped
thermo-electric couples (Fig. 38), which are plunged into two symmetrical
muscles of the frog, one of which is at rest, the other contracting (Helmholtz).
(HUM
mmn^nmx^f "^""^'^^^tHasnr:
FIG. 39. — Photograph of positive and negative variations of temperature obtained with two
thermo-electric needles pushed into the two gastrocnemius muscles of a frog, and connected
with a low resistance galvanometer ; the sciatic nerve was excited alternately on either side.
(A. D. Waller.) The excursions of the galvanometer mirror are photographed by a beam of light
reflected on to the sensitive surface of a moving drum. Each tetanising excitation of the
sc-iatics, respectively, lasted one minute as indicated by the break of the abscissa line. During
tetanus the curve falls or rises, according as the right or left sciatic was excited.
To measure the rise of temperature developed in a simple twitch a Melloni's
thermopile is used, which consists of several elements, the two muscles of
the frog being placed in contact with the two surfaces at which are the
junctions of the elements of the pile (Heidenhain).
If a mirror is attached to the magnet of the galvanometer, its deflections
can be photographed by the reflection of a ray of light upon a sensitive
surface (Waller, Fig. 39).
The first experiments that proved incontestably that muscle
is concerned in the production of heat as well as motion were
performed on cold-blooded animals by Helmholtz (1847). By
employing the thermo-electric method he saw that the muscles of
the frog's thigh developed heat during indirect or direct tetanisa-
tion (0-14°-0-18° C.).
In later experiments (1864) Heidenhain measured the rise of
temperature (1-5 hundredths of a degree) in the isolated gastro-
cnemius of the frog after a simple twitch.
There is therefore no doubt that muscular contraction is
accompanied by a development of heat, which is due to an increase
of exothermal processes within the contractile organ, by which the
greater part of the store of accumulated energy is dispersed.
62 PHYSIOLOGY CHAP.
Even in rest, however, muscle develops more heat thaii other
tissues. An indirect proof of this is obtained from the experi-
ments in which Claude Bernard attempted to estimate the oxygen
content of the hlood flowing respectively to and from the muscle,
in rest and during tetanus. According to Bernard the blood of
the artery of the anterior rectus muscle of the dog's leg carries
9'31 c.c. oxygen, the blood that flows from the veins 8'21 c.c. when
the muscle is at rest, 3'31 during tetanus. During its activity,
therefore, the muscle consumes much more oxygen than during
rest ; but even in the resting state it consumes a certain amount,
and must therefore develop heat.
These results were confirmed in Ludwig's laboratory by Meade
Smith (1881), who made numerous direct estimations of tempera-
ture, both on the blood of the artery and vein of the muscle, and
on the resting or tetanised muscle itself. The general conclusion
was that the temperature in the artery is less than in the vein
and in the muscle in the resting state, and that the difference
increases considerably during tetanus.
Beclard was the first who studied heat production in muscle
from the point of view of the mechanical theory of heat (1861).
He tried first on the frog by the thermo-electric method, and then
on his own biceps muscle, to estimate with an air-thermometer,
graduated in fiftieths of a degree, the amount of heat developed
during static (isometric) contraction, in which the mechanical work
is nil, with that produced during dynamic (isotonic) contraction,
which is accompanied by mechanical work that can be measured
in kilogrammetres. He stated positively that when the muscular
contraction results in muscular work, much less heat is evolved in
the muscle than when a contraction of the same strength is not
accompanied by external mechanical effects.
This fact, despite the imperfections of Beclard's method, proves
that muscular activity is subject to the great law of the conserva-
tion of energy. When the whole of the energy liberated by the
muscle is expressed in the form of heat, more heat is evolved than
when part of the energy is converted into muscular work.
Beclard further demonstrated that the amount of energy trans-
formed into mechanical work during the lifting of the weight by
the muscle is reconverted into heat when the raising is succeeded
by the lowering of the weight, i.e. when the positive is followed
by negative work. The experiment consists in comparing the
heat developed when a certain weight is held up for a given time
by the static contraction of the biceps, with that developed during
the same time when the arm loaded with the same weight makes
up and down movements. Under these conditions (according to
Beclard) the development of heat indicated by the thermometer is
equal, whether the arm be kept in equilibrium or executes move-
ments. The positive work of raising the weight is therefore
GENERAL PHYSIOLOGY OF MUSCLE
03
cancelled by the negative work of lowering it, so that in this case
the heat production in static contraction is equal to that in dynamic
contraction.
But apart from the imperfections of the method Beclard's
results were incomplete. He neglected the influence exerted by
differences of load on muscular thermogenesis, as well as the degree
of stimulation and the state of fatigue of the muscles. In 1864
Heidenhain investigated the question again from a wider point of
view and by more exact methods. He employed the isolated
muscles of the frog, with different loads, and recorded the height
of the contractions, from which he calculated the work, and
measured the changes of temperature with a thermo-electric pile.
Since we know that with increase of load the mechanical work
of the muscle increases within certain limits (Fig. 26, p. 46) it
seems natural to suppose that the simultaneous development of
heat takes place inversely and diminishes with increment of work,
so that the sum of energy liberated by the katabolic processes in
the muscle remains constant for the same stimulus, its division
into work and heat alone being variable. Heidenhain's researches,
however, demonstrated that when the intensity of the stimulus
remains constant, the sum of energy developed by the muscle
increases up to a certain point with increase of load, i.e. the
increase of work is accompanied by increased heat-production.
This important conclusion is represented by the following
table, which gives Heidenhain's data from one of his experiments
on the gastrocuemius of the frog loaded with different weights :—
Increased warmth
Number
of test.
Weights applied
to the muscle.
Summated
height of three
contractions.
Mechanical
work of the three
contractions.
of the muscle
expressed in
degrees of the scale
of the thernio-
multiplier.
1
grms.
10
mm.
10-6
gr. mm.
106
8-5
2
30
10-4
312
11-5
3
90
8-5
761
18-0
4
60
9-6
573
11-5
5
30
10-6
318
9-5
6
10
10-8
108
7-0
During three successive contractions the muscle was loaded
with the weight during both contraction and relaxation ; thus the
mechanical work given out by the muscle during contraction was
restored to it in the form of heat during relaxation. The rise of
temperature shown in the table therefore expresses the total sum
of the energy developed by the muscle during the three successive
contractions. This is not a constant but varies with the external
mechanical work : it increases with the increment of this work
64 PHYSIOLOGY CHAP.
and declines with its decrement. The facts collected by Heiden-
haiu, however, show that the rise and fall of temperature in the
muscle are not strictly proportionate to the increase and
diminution of the mechanical work which it performs ; generally
speaking, the thermal increase is much less than the increase of
work. This proves that the muscle works more economically
when it lifts a moderate weight than when it lifts a lighter one.
The property which the muscle possesses of adjusting the
quantity of energy which it develops under a constant stimulus
to the greater or less resistance which it has to overcome, is very
important. If the strength of its reaction depended only on the
strength of the stimulus, and was independent of the load, then
the development of muscular energy — the nerve impulses remain-
ing uniform — would not be in proportion with the external work
that had to be performed. Heidenhaiu's discovery that the total
sum of energy developed by the muscle depends on the degree of
tension due to the resistance it encounters in contracting, shows
that it possesses a mechanism in itself which is capable — inde-
pendently of the nervous impulses — of partially regulating its
intrinsic metabolism according to the needs of the moment.
Again, when the load remains constant, and the strength of
stimulation is progressively increased, the development of heat
increases — within certain limits — with the height of the con-
tractions and the mechanical work performed, till it reaches a
maximum. So that the metabolism and heat production of
muscle are regulated not only by tension, but also by the nervous
system, owing to the varying intensity of the impulses which it
transmits to the muscle.
It should, however, according to the results of Heidenhain and
Nawalichin, be observed that, just as we have seen with constant
stimulus and increasing load, so too with a constant load and a
progressively increased stimulus, the increase in heat and work
development are not parallel, but the maximum production of heat
is always reached before the maximum of work, i.e. the heat pro-
duction increases more rapidly than the height of the contractions.
This proves that the muscle works more economically whenever it
is more strongly excited from the nerve, and forced to do more
work.
But when the same amount of work is performed by a muscle,
on the one hand by many small contractions, on the other by
fewer but larger contractions, less heat, according to Heidenhain,
is developed in the first case than in the second. This agrees
with the common observation that it is more fatiguing to ascend a
rapid incline with long steps, than a less steep slope of the same
height, with shorter steps.
Heidenhaiu brought out another interesting fact which is not
easy to explain. When the same amount of work is performed by
i GENERAL PHYSIOLOGY OF MUSCLE 65
a fresh muscle and a fatigued muscle, the former develops more
heat than the latter, as if the chemical activity necessary for
developing the same amount of useful external work were greater
in the fresh muscle and less in the fatigued. In a series of
successive contractions of equal height, carried out by a muscle
loaded with the same weight, so that each contraction performs
the same amount of work, the development of heat diminishes
between the first and the last of the series. This shows that
fatigue can be detected in the diminished heat-production before
it becomes evident in the lessened height of contraction. Accord-
ingly, as it becomes fatigued, the muscle functions more economi-
cally— i.e. a less amount of energy is transformed into heat.
When the impulses that reach the muscle follow so rapidly as
to give rise to tetanic fusion of the contractions, the production of
heat increases progressively up to a certain maximum, in propor-
tion to the increasing height to which the weight is raised.
The heat developed in tetanus increases with increment of the
load and corresponding tension of tjhe muscle. When the weight
is so great as to inhibit contraction altogether, more heat is
developed than when the load is less and the muscle can shorten
a little. During the development of tension the heat production
is greater than when the tetanic rise is complete. During a brief
tetanus the same amount of heat is liberated at each instant. But
during the contraction, and possibly during the relaxation, that
precede and follow tetanus, a much larger quantity of heat is
developed.
Heidenhain's work on muscular thermogeuesis was extended
and completed by Fick and his pupils. Fick in his first experi-
ments (1884) resumed the study of the question already investigated
by Beelard. Heidenhain's discovery that the sum of the energy
(work and heat) developed by the muscle is proportional to its
tension during its activity, does not contradict Beclard's view, as
Hermann also pointed out, that with constant tension the sum of
energy developed by the muscle (work and heat) is in direct ratio
with the intensity and duration of its activity, so that, caeteris
paribiis, the energy liberated in the form of work is inversely
proportional to that liberated in the form of heat — conformably
with the law of conservation of energy.
In order to prove this theory experimentally, Fick employed
Heidenhain's method on the excised muscles of the frog. To
compare the thermal production in useful work with that of con-
traction by which no external work was performed, he invented
an ingenious apparatus which he termed " Arbeitssammler." This
is a small windlass which the muscle turns on contracting 'against
the constant resistance of a weight, which can be prevented from
dropping again during relaxation by putting a brake on the wheel
(Fig. 40). When this is applied the muscle is unloaded, i.e. freed
VOL. in F
66
PHYSIOLOGY
CHAr.
from the weight, when it begins to relax, and the work done in
contraction is utilised ; when the break is removed, the work done
is cancelled and converted into heat when the muscle relaxes.
Tick's results confirmed Beclard's hypothesis. In a series of
contractions produced by stimuli of uniform strength, while the
muscle is performing useful work, less heat is evolved than in a
Fir.. 40. — Kick's Arbeitssammler, by which the muscle is loader! with a weight during contraction,
and unloaded during relaxation. While contracting, the muscle (frog's gastrocnemius) lifts
the lever r rj, which in itself offers little resistance, as it is almost balanced by the small
counterpoise /. But owing to the support /(, which presses on the edge of the graduated disc
m M (which revolves round the same axis as the lever), the disc turns as the lever rises, along
with the concentric pulley that carries the thread to which the weight is attached. The
muscle is thus loaded during contraction, and lifts the. weight to a height that can be exactly
measured by the degree of rotation of the disc shown on the scale ./'. In relaxing, the muscle
is freed from its load, because the disc and pulley cannot drop back owing to the stop /ij.
The weight remains up, and the lever sinks to its original position owing to the slight pre-
ponderance of arm r over arm )-j. At each succeeding contraction the weight is lifted higher,
so that from the total rotation of the disc it is easy to calculate the total sum of work per-
formed by the muscle in a given number of contractions. When the stop /ij is removed from
the edge of the disc, the apparatus can be used as a simple isotonic lever. At each contraction
the muscle rotates the disc and lifts the weight ; but at each successive relaxation the work
done is cancelled, because the disc retracts with the lever owing to the pull of the weight.
second series of uniform contractions, produced by stimuli of the
same strength, in which the muscle performs no useful work.
The later work of Danilewsky, Blix, and Chauveau leads to the
same conclusion.
On comparing the heat developed by a series of maximal
muscular contractions in a given time without useful work, with
that developed by the same muscle in the same time with maximal
i GENERAL PHYSIOLOGY OF MUSCLE 67
stimuli so frequent as to produce complete tetanus, Fick observed
that in the first case there was a much greater development of heat
than in the second. From this he concluded:—
(a) That the amount of heat developed at each contraction
during tetanus is in inverse ratio to the frequency of the stimuli.
(b) That in a series of single contractions due to momentary
stimuli, the theriiiogenetic effect of each twitch far exceeds that
of each contraction of a series of such frequency as to result in
tetanus.
Fick tried to express the amount of heat liberated during
muscular activity in absolute values. He found that the maximum
heat which a gram of muscle may develop during a simple con-
traction may reach the value of 3'1 microcalories, a microcalorie
being the amount of heat required to raise the temperature of
1 mgrm. of water 1° C. With his pupils he determined the relative
rates at which the development of heat and of work increased, by
a series of tests on frog muscle excited with maximal stimuli, and
loaded with regularly increasing weights.
The general result as a rule was that the greater part of the
potential chemical energy liberated by the muscle during its
activity appeared in the form of heat. But with increase of load
the ratio between heat and work alters regularly, as an increasingly
larger part of the potential chemical energy is set free in the form
of work, and a comparatively smaller part as heat. This proves
that the muscle in doing more work functions more economically
than in doing little work.
Zuntz, Lehmann, and Hagemann (1889) tried to ascertain what
proportion of the total energy developed in the muscles of warm-
blooded animals is utilised in the form of mechanical work. This
question has only been solved approximately by calculating the
total chemical energy developed by the estimation of the reciprocal
gas-exchanges which take place in any given work of the muscles.
It was shown by experiments on horses that about J of the
energy is transformed into work, and f into heat. If we con-
sider that in the best steam-engines man is able to construct
only jL or TV part of the energy liberated can be utilised in
mechanical work, all the rest being lost in the form of heat, we
see that the muscle is a living machine which functions more
economically than any steam-engine. On the other hand, an
electric motor fed from a battery is capable of utilising y9^
of the energy developed by the oxidisation of the zinc of the cell
in external mechanical work, so that it is a more perfect machine
than the muscle. We must not, however, forget that in homoio-
thermic animals the development of heat must not be regarded as
a loss, since it is as useful to the organism as mechanical work.
A muscle is not merely an apparatus for the production of external
work, but it also serves to heat the body of warm-blooded
68 PHYSIOLOGY CHAP.
animals, and raise their temperature to a given height, inde-
pendently of the variations of external temperature. From this
physiological standpoint it may be held that the muscle utilises
all the energy which it develops, either in the form of work or of
heat.
XL A portion of the potential chemical energy liberated
during the activity of the muscle appears not as heat, but as
electricity.
A discovery of great importance in physics — galvanism, and in
physiology — animal electricity, originated in Galvani's observations
that muscles of a recently killed frog were thrown into convulsions
on closing the circuit between the muscles and the nerves by
means of two metals. From this Galvaiii concluded that the
muscles of the frog were normally charged like a Leyden jar, with
positive electricity inside and negative electricity outside each
muscle. Hence he assumed that on making connection between
the inside and outside of a
muscle, a current was produced
which gave rise to the con-
traction.
Volta at once recognised
that this interpretation was
erroneous, because the circuit
FIG. 41. — Galvani's second experiment, without • • j-™» t i
metais. comprising two different metals
in itself contained a source of
electromotive force. The long controversy between Volta, who
affirmed the existence of metallic currents, and Galvani, who
maintained the contrary and endeavoured to explain everything
by muscle currents, is certainly one of the most remarkable
incidents in the history of experimental science. The contrary
statements of the two protagonists were true ; their negations
were false. Volta's theory led to the discovery of the pile ;
Galvani's to the first demonstration that living tissues in general,
and the muscles in particular, may, under given conditions, be the
seat of the development of electrical currents.
The observation of Galvani and his nephew Aldini was
based on the fact that contraction takes place in the muscles of
a recently killed frog, not only when a circuit is made between a
muscle and its nerve by a bridge consisting of two metals or even
of one metal, but also — though in a less degree — when the circuit
is made without any metal. This experiment, famous in the
annals of medicine, consists in laying the nerve-muscle preparation
of a frog upon a glass plate (Fig. 41), and bringing the surface of
the muscle into contact with the end of the freshly-cut nerve by
a glass rod. At the moment of contact the muscle contracts.
Eepeated and confirmed by Valli (1794) and Alexander v.
Humboldt (1798), this experiment underlies the general theory
i GENEEAL PHYSIOLOGY OF MUSCLE 69
that living tissues are under special conditions the seat of
electromotive forces, which may excite muscular contractions on
the closure of non-metallic circuits.
Direct proof of this was not available till after the invention
of the galvanometer by Nobili (1824), when it became possible
not only to demonstrate the existence of the comparatively
weak currents present in living tissues, but also to measure them.
In 1827 Nobili made use of Schweigger's rnultiplicator to demon-
strate the so-called " natural current " of the frog, directed from
the foot towards the head.
On repeating and varying Nobili's experiment in different
ways, Matteucci (1838-40) discovered the phenomenon known
later as the "current of rest" in muscle. He amputated the
thigh of a skinned frog by a transverse incision, and brought it
into the circuit of a galvanometer, by applying one electrode to
the cut surface and the other to the outer surface of the thigh
muscles. On closing the current the galvanometer needle was
Fin. 42. — Matteucci's experiment of secondary contraction and tetanus.
deflected, showing a current in the muscle from within outwards,
i.e. from the cut surface to the natural surface of the muscle, in
the galvanometer circuit from the natural to the cut surface.1
In 1842 Matteucci communicated to the Academic des Sciences
in Paris another discovery, which Biedermann reckons among the
most important in experimental physiology. When the nerve of
a frog's leg is placed on the muscle of the opposite leg, and the
nerve of the latter is excited by certain stimuli, a vigorous primary
contraction results in the muscles of this excited limb, accom-
panied by a less vigorous secondary contraction in the muscles of
the other limb (Fig. 42).
This observation was the first demonstration of an electrical
phenomenon concomitant with the state of muscular activity.
Matteucci interpreted it wrongly ; the true explanation was only
possible after the law of the current of rest in muscle and its
negative variation had been discovered by du Bois-Keymond (1843).
1 To avoid the confusion that frequently arises between the current in the
outer (galvanometer) circuit and that flowing within the tissue, it might be well,
as suggested by Waller, to replace the ambiguous term " negative " (more correctly
" electro-positive ") by the term "zincative," which would serve as a reminder that
the current flows from the excited to the unexcited portion of the tissue, as from
zinc to copper in a Daniell cell. — Translator.
70 PHYSIOLOGY CHAP.
Du Bois-Keymond's researches began in 1841, shortly after
Fin. 43. — Thomson's galvanometer. To the left is the galvanometer, in the centre a .shunt, to the
right the scale, illuminated by a beam reflected from a lamp to the galvanometer mirror.
those of Matteucci.
Jl
FIG. 44. — Diagram of galvano-
meter, n s and s n, pair of
magnets with opposite poles,
circular mirror fixed to upper
magnet ; 1 1, end of wire that
surrounds the magnets ; N S,
third magnet, which controls
the two lower magnets.
equilibrium
theory ").
He devoted many years to the study of
animal electricity, and his great merit lies
in the introduction of exact methods. His
discovery of unpolarisable electrodes, com-
bined with the method of compensating
by means of a rheochord, enabled him to
separate the tissue currents from those of
metallic origin, and to measure them, both
in the resting state of the muscles and
nerves and during their activity.
In 1807 Hermann's investigations
opened up a new chapter in electro-
physiology. He overthrew clu Bois-
Reymond's theory, according to which
electrical currents are pre - existent in
normal living tissues in the resting state
(" pre-existence theory"]. By the experi-
ments we are about to discuss, which were
to a large extent confirmed by subsequent
observers (Hering, Engelmaun, Bieder-
mann, and others), Hermann proved that
muscles and other tissues, so long as
they are at rest and intact, give off no
currents to the galvanometer. When
currents appear they are due solely to
the effects of artificial alteration of the
tissues, or to the disturbance of chemical
which accompanies functional activity (" alteration
GENEEAL PHYSIOLOGY OF MUSCLE
71
Owing to (lie high resistance of animal tissues (which is millions of times
greater than the resistance of metals) and their low potential, it is necessary
in electrophysiological research to employ galvanometers or multipliers with
FIG. 45. — Various forms of unpolarisable electrodes. D and C, du Bois-Reymond's pattern ;
E, Burden-Sanderson's ; B, von Fleischl's ; A, d'Arsouval's.
astatic magnets, so as to render the vibrations as
have a high internal resistance
the instrument can be decreased
These galvanometers
of
,9,99
1 oTFu
many coils and with
a-periodic as possible.
(5,000-20,000 ohms). The sensitiveness
by a shunt, which cuts off -j9^, -fifa, or
of the current. The principle on which gal-
vanometers are constructed is that a magnet,
suspended and surrounded by a conducting
wire, is deflected in the direction of a current
passing through the wire, in proportion to
the strength of the current.
Both in Wiedemann's (with detachable
and interchangeable spools) and in Thomson's
galvanometer (Figs. 43, 44) the deflections of
the magnet suspended by a thread of raw silk
are more or less magnified by a mirror which
reflects a ray of light on to a horizontal scale.
These deflections can be photographed on a
moving sensitive surface.
The ends of the galvanometer wires must
not be directly applied to the tissues, on
account of their polarisability. Unpolarisable
electrodes are indispensable in experimenting
with muscle and nerve (du Bois-Eeymond).
These usually consist of a little rod or disc of
amalgamated zinc dipping into solution of
zinc sulphate in a glass tube, the other end
of which is closed by a plug of china clay
saturated with physiological saline, which is in contact with
protects it from the caustic action of the zinc sulphate (Fig. 45).
Nowadays, however, all these imperfect electrodes may be replaced by the
so-called "normal electrodes" of Ostwald, in which potassium chloride is
FIG. 46. — Ostwald's normal electrode,
adapted to physiological research
by Oker Blom.
the tissue and
PHYSIOLOGY
CHAP.
substituted for sodium chloride. A suitable adaptation of these to physio-
logical purposes is the model of Oker Blom (1900). Two glass tubes are
sealed at the bottom in the flame, with a little mercury on the base, by which
contact is made with two platinum wires that pass through the sealed ends.
Pure calomel is placed on the mercury, and above that physiological salt
solution, which is brought into contact with the muscle by a tag of cotton
saturated with the solution (Fig. 46).
The galvanometer can be replaced by Lippmann's capillary electrometer,
which has the advantage of reacting to very rapid oscillations of current, with
FN;. 47. — Lippmamf s capillary electrometer. A, viewed as a whole (pressure bulb, capillary, and
microscope) ; 1', tube (Hg) and capillary (<•) which dips into the tube of sulphuric acid
(HoSO.|) ; C, mercury in capillary tube under the microscope.
no lost time and no periodic vibrations. Moreover, as the resistance in the
capillary is enormous and the current passing through it is practically abolished,
nnpolarisable electrodes can be dispensed with. As seen in Fig. 47, the
instrument consists of a glass tube drawn out in the flame at one end to a
capillary 20-30 mm. diameter. This tube is filled with mercury and joined to
an apparatus by which the pressure can be regulated. The open end of the
capillary dips into 10 per cent sulphuric acid solution. Two platinum wires con-
nect the mercury and sulphuric acid, respectively, to the points of the organ under
investigation. Under the microscope the excursions of the mercury meniscus
—which is brought into the field by means of the pressure apparatus — can be
seen plainly on closure of the circuit. The meniscus advances or recedes towards
the end of the capillary according as the potential rises or falls on the side of
the mercury tube, and vice versa as regards the reservoir of sulphuric acid.
In the capillary electrometer the excursions of the meniscus do not
i GENERAL PHYSIOLOGY OF MUSCLE 73
indicate the strength of current, but the electromotive force or <li (Terence of
potential between the two electrodes. It is thus an electrical manometer,
the sensitiveness of which is so great that it reacts to TUT&UTT volt. The dis-
placements of the mercury surface can be photographed.
Eiiithoven (1905-6) introduced the string galvanometer which has distinct
advantages over its predecessors.
This instrument has a fine thread of silvered quartz or platinum stretched
between the two poles of a strong magnet. On passing a weak current
through the string, it moves laterally in proportion to the strength of the
current. The poles of the magnet are pierced by holes so that the thread may
be illuminated by an electric light from the one side, and observed from the
other by means of a microscope ; or a magnified image may be thrown on a
screen, or moving sensitive surface on which it is photographed.
Einthoven devised this apparatus for the special purpose of studying
the electrical variations of the human heart. But it may be substituted
advantageously for all purposes instead of the apparatus described above.
We will briefly consider the principal electromotive phenomena
in muscle, keeping distinct the electrical manifestations of the
resting and the active states.
When a muscle with parallel fibres, e.g. the frog's sartorius, is
dissected out, and the tendinous end trimmed neatly with a razor,
a regular cylinder of muscle substance is obtained, with a natural
longitudinal surface and two artificial cross-sections. If any two
points of this muscle are connected with the galvanometer by
unpolarisable electrodes there is nearly always a deflection of the
galvanometer needle, showing that the two points led off are not
isoelectric, but that there is a difference in potential.
If the electrodes are applied to points on the natural
longitudinal and the artificial transverse surfaces, the former is
found to be " positive" in relation to the latter, which is " negative."
Du Bois-Keymond made a minute study of the different degrees
to which the galvanometer needle was deflected by altering the
position of the electrodes upon the muscle cylinders, and drew up
the following laws of the muscle current :—
(a) Strong currents appear on leading off to the galvano-
meter from the natural longitudinal surface and artificial cross-
section of the muscle. The current is strongest when a point in
the equatorial median line of the longitudinal surface is connected
with the axial point of an artificial cross-section, and decreases
regularly with increased distance from these points.
(&) Weak currents are obtained when two points at unequal
distance from the equator of the longitudinal section are united ;
still weaker currents when two points of the cross-section at un-
equal distances from the ends of its axis are connected.
(c) No current is obtained on connecting two points of the
equator or any two points at equal distance from the same ; nor on
connecting the two axial points of the cross-section, or any two
points of the cross - section equidistant from the axial points
(Fig. 48).
74
PHYSIOLOGY
CHAP.
These observations show that the natural surface of the muscle
has a positive electrical charge, which is maximal along the
equatorial Hue and decreases regularly away from it; and that the
two artificial cross-sections have a negative electrical charge which
decreases regularly from the axial point of the muscle cylinder,
4-
•f
! +
— t —
Fie. 48. — Diagram of direction of currents that
can be led off to a galvanometer from
different points of the surface of a muscle
cylinder.
-f
Fia. 4;t. — Distribution of positive electrical
charge on natural longitudinal, and negative
electrical charge on artificial transverse
sections of a muscle cylinder.
where it is maximal, to the more peripheral points of the cross-
section (Fig. 49).
If the section is made obliquely through the muscle cylinder,
the potential at the different points of the natural surface and the
artificial surfaces varies according to another law. The galvano-
meter shows that the most positive points of the longitudinal
surface lie much nearer the obtuse angles of the rhombus, and the
more negative points close to the acute angles. The strongest
current is obtained on leading-off from these opposite points ; on
4-
\
FIG. 50. — Diagram of direction of currents led
off from surface of a muscle rhombus.
-f- +
Kici. 51. — Positive and negative electrical
charges at longitudinal and transverse
sections of a muscle rhombus.
connecting points more remote from these the currents become
increasingly weaker ; lastly, there is no current on joining up
honionymous points on the natural or artificial surfaces (Fig. 50).
There is thus in the oblique muscle cylinder a displacement of
the isoelectric equatorial and axial points in the direction indicated
in Fig. 51.
The longitudinal surface of a muscle shows a positive charge
i GENEKAL PHYSIOLOGY OF MUSCLE 75
as compared with the artificial transverse or oblique section, even
when it is not the natural external surface covered with periinysium,
but the surface of a bundle of fibres artificially dissected out, but
otherwise intact. On the other hand, the natural transverse or
oblique section, consisting of the ends of the fibres where they are
connected with the tendon or aponeurosis, is not — like the artificial
surface produced by a cut — negative to the longitudinal surface.
The negative charge first makes its appearance after removal of
the tendon, i.e. on the formation of an artificial cross-section.
The gastrocnemius muscle, which is generally employed for a
nerve-muscle preparation from the frog, shows marked differences
of potential at different points of its natural surface, which do not
altogether conform, to the laws of the current of rest in straight or
oblique muscle cylinders. This is due to the complicated structure
Fio. 52. — Measurement of electromotive force of current of rest in muscle by method of compensa-
tion. V )•, rectilinear rheochord (monochord) consisting of a long wire connected at the ends
to the battery. The runm-r *• is movable along it, so that any fraction of the battery current
can be thrown into the galvanometer to compensate the muscle current which is opposite
in direction.
of the muscle, which consists not of parallel fibres, but of fibres that
run obliquely (Kosenthal).
The electromotive force which a frog's muscle is capable of
developing may be measured by the compensation method, i.e. by
introducing into the circuit that connects the two oppositely
charged points of the muscle with the galvanometer a current
from a Daniell cell in the direction opposite to, and of the same
strength as, the muscle current. This is easily effected by means of
a rheochord (Fig. 52). The electromotive force has been known to
exceed O'OS volt (du Bois-Eeymond, Chapman). But it may be
concluded that the portion of the current led off to the galvano-
meter is only a small fraction of the total current developed
within the muscle, which we are not in a position to measure
(Bernstein).
The electrical phenomena of the resting muscle depend on the
state of vitality of the tissues. Muscles that are dead or in rigor
mortis are electrically inactive. Muscles treated with ether vapour,
76 PHYSIOLOGY CHAP.
or swollen with water, which are totally inexcitable and apparently
dead do, on the contrary, manifest differences of electrical
potential.
Another important fact discovered by Hermann and confirmed
by Biedermann and others is that wholly uninjured muscles
are isoelectric, i.e. manifest no difference in potential at their
surface in the resting state. When the hind -leg of a frog is
very carefully skinned, precaution being taken to avoid contact
between the cutaneous secretion and the exposed surface of the
muscle, no current can be led off from the latter to the galvano-
meter. When, on the contrary, an exposed muscle is injured at
any point of its surface by cauterisation, chemical burns, partial
poisoning with potassium salts, mechanical crushing, etc., the
injured spot invariably becomes negative to the intact parts of the
surface. So that injured points react like transverse or oblique
surfaces produced by section. Hermann, therefore, formulated the
general law which is applicable to all cases, that " In every injured
muscle fibre the surface of demarcation between the living and
dead portions of the fibre is the seat of an electromotive force
directed towards the living part." He gave the name of demarca-
tion current to the so-called " current of rest," because it does not
pre-exist in the normal muscle, but first appears when any part of
the latter suffers alteration. [Current of injury : Hering.]
Another phenomenon brought out by Hermann is that a
general rise of temperature increases the strength of the demarca-
tion current up to a certain limit, beyond which it decreases
again, till it disappears with the onset of heat rigor. A drop in
the temperature, on the contrary, lowers the e.m.f. Again, in
intact muscle heated points are electro-positive to cooler parts
(Hermann and Worm-Mliller). Finally, fatigue from protracted
muscular activity weakens the demarcation current (Eb'ber), and
abolishes it if pushed as far as rigor.
Another fact in favour of Hermann's views is that in muscle
prisms or cylinders freshly cut with a razor and connected with
the galvanometer the demarcation current is absent, or almost
absent, during the first moments, but increases rapidly to its
maximum. This phenomenon can only be explained by assuming
that the surface of the section alters with exposure to air, and
that its negative potential increases in proportion with this
change. The alteration shown in the acidification of- the muscle
gradually extends over the whole, till it becomes perfectly rigid.
The demarcation current as shown on the galvanometer suffers
a parallel slow diminution, till it eventually disappears.
We must next study the phenomena of active muscle. If the
nerve of a muscle-nerve preparation that is showing a demarcation
current on the galvanometer is tetanised, the current is diminished
—the galvanometer needle swings back towards the zero of the
i GENERAL PHYSIOLOGY OF MUSCLE 77
scale during the tetanus. This is the " negative variation " referred
to above. On a sensitive galvanometer it can be shown during
single twitches as well as in tetanus. If the current of rest is
compensated, and the nerve is then excited, the negative variation
will appear on the galvanometer as an autonomous current, in
the opposite direction to the current of rest — showing that the
e.m.f. of the muscle is diminished by excitation (du Bois-Pieyrnond).
The phenomena of secondary contraction, or induced contraction
as it was termed by Matteucci, and secondary tetanus, which can
be seen in a frog's leg when its nerves are laid across the muscles
of another leg, so that the muscle current produced in the latter
on contraction passes through the nerves of the former (Fig. 42),
depend, as du Bois-Eeymond showed, on the exciting action of
the negative variation of the current. The secondary twitch is
the simplest and most convincing proof that a single contraction
can elicit a negative variation of sufficient intensity to stimulate
the nerve. Secondary tetanus further shows that the negative
variation of the primary tetanus is a discontinuous process,
although the variations in the current are too rapid to be
followed by the galvanometer needle, and their mean value only
is recorded.
The oscillating character of the muscle current in tetanus can
also be demonstrated by the telephone, which Hermann regards
as more sensitive than the " galvanoscopic leg." When the
muscle current is led off to a telephone, a sound is heard during
tetanisation which results, as Bernstein and Wedensky demon-
strated, from a number of vibrations equal to the rate of the break
or make shocks of the tetanising current.
Bernstein was able by an ingenious apparatus known as the
differential rheotome to analyse the negative variation during a
simple contraction.
The negative variation in a nerve-muscle preparation during
tetanus can be photographed by reflecting a beam of light from
the galvanometer magnet on to a sensitive surface moving by
clockwork. Fig. 53 records the tetanic contraction and accom-
panying negative variation.
The galvanometer does not react quickly enough to show the
oscillations that accompany tetanus, but if the capillary electro-
meter is used, they can be photographed by letting the shadow
of the meniscus fall on a slit behind the sensitive paper, which
travels in a direction vertical to the oscillations of the mercury
(Burdon-Sanderson and others).
The negative variation increases to a maximum with the
intensity of the tetanising current. According to Bernstein it
never reaches the zero point, i.e. never cancels the demarcation
current. According to Gotch and Sanderson, on the contrary,
the negative variation may pass beyond the zero point, and
78
PHYSIOLOGY
CHAP.
exceed the value of the demarcation current ; for instance, the
demarcation current may equal O04 volt, the negative variation
0'08 volt. The negative variation also increases up to a certain
maximum with increase of the elastic tension or load of the
muscle, parallel with the development of work and of heat.
In order to understand the nature of the negative variation
of the demarcation current in muscle when the nerve is tetanised,
FIG. 53.— Myogram of tetanic contraction of frog's gastrocnemius (white line on black ground) ,-md
simultaneous photograph of negative variation (black line on white ground). (A. D. Waller.)
u, gradually diminishing demarcation current; &, its sudden decrease during tetanus (negative
variation) ; c, subsequent positive variation on cessation of tetanus ; d, return of slowly
declining demarcation current.
it must be remembered that in consequence of stimulation the
whole mass of the muscle undergoes an explosive chemical change
associated with the passage from the state of rest to the state of
activity, which is greater in the normal than in the altered parts
of the muscle. This effect of excitation sets up a difference of
electrical potential and gives rise to the action current, which
neutralises the demarcation current, and may even exceed it
(Gotch and Sanderson).
GENEEAL PHYSIOLOGY OF MUSCLE
In studying the current of action developed by stimulation
it is best to employ an intact muscle with no current of rest,
for as this would pass in the opposite direction, it would be
unfavourable to the demonstration of the action current, which
would then seem to be only the negative variation of the current
of rest. When the galvanometer electrodes are applied to both
ends of an intact and freshly excised muscle, as in Fig. 54, A, B,
and the muscle is stimulated at C by an induction shock, the
reaction does not take place simultaneously all over the muscle,
but it is propagated, as we saw above (Fig. 16, p. 23), like a wave
from the point stimulated to the more distant points. So that
the end A of the muscle which is near the point of application of
B
Fir:. 54. — Apparatus for study of diphasic-
action current.
FIG. 55. — Myogram of a contraction of frog's gastro-
enrmius, in m, and simultaneous photograph of
diphasic electrical variation, e e. (A. D. Waller.)
the stimulus C will be thrown into activity first, and the end B
last. Since the active points of the muscle become galvano-
metrically negative to the inactive points, the galvanometer needle
reacts in a diphasic oscillation. In the first phase A will be
negative to B, in the second phase B will be negative to A. The
first phase coincides with the transmission of the contractile wave
from A to B ; the second phase coincides with the contraction of
B, as A begins to relax. The slower the transmission of the
wave along the muscle, the more prolonged will be the negativity
of A at the beginning, and of B at the close of the contraction.
Hence the diphasic variation of the action current is more easily
demonstrated on the frog's heart, where the systolic wave is
propagated on an average at O'l m. per second, than in skeletal
muscle, where the wave of contraction is propagated at about
1 m. per second.
Pig. 55 gives the myogram of a contraction produced in the
frog's gastrocneuiius when an induction shock is sent through
80
PHYSIOLOGY
CHAP.
the sciatic nerve, with a synchronous photograph of the diphasic
current of action. In this case the muscle was indirectly stimu-
lated, and the contractile wave started from the end-plates which
usually lie about midway in the fibres, and spread from there
towards the two ends, one electrode connected with the sulphuric
Fir;. 56. — Cardiogram of spontaneous beat of frog's heart, It, and simultaneous photograph of
diphasic variation, e. (A. D. Waller.)
acid of the electrometer being applied near the middle of the
muscle, and the other, connected with the mercury, to the
tendinous end. Fig. 56 gives the spontaneous cardiogram of the
frog's heart with a synchronous photograph of the diphasic
variation, the sulphuric acid electrode being applied to the apex
FIG. 57. — Apparatus for leading off diphasic action current from the muscles of the human fore-
arm. (Hermann.) To light of figure an unpolarisable bracelet electrode ; r, »•', points of
stimulation of brachial plexus.
of the heart, and the mercury electrodes to the base of the
ventricle. In the first experiment there is a positive oscillation
of the electrometer at the first phase, and a negative oscillation
at the second phase, because in the first phase the end of the
muscle is positive to its middle part, which was first thrown
into contraction — negative to it in the second phase. In the
GENERAL PHYSIOLOGY OF MUSCLE
81
experiment on the heart, on the contrary, there is a negative
oscillation in the first phase, which expresses the negativity of
the base to the apex at the commencement of systole, and a
positive oscillation in the second phase, which expresses the
positivity of base to apex at the close of systole and commence-
ment of diastole.
Hermann succeeded in demonstrating the diphasic variation in
I
I
Fie;. 58. — Distribution of electrical potential to different parts of the human body at the moment
at which the diphasic action current of the heart arises. (A. D. Waller.) A, apex ; B, base of
ventricles ; 0 0, equatorial line or plane in which the electrical potential is nil ; a, a, a and
6, ft, b are the equipotential curves of A and L.
the muscles of the fore-arm of a man by stimulating the brachial
plexus in the axilla. The current was led off by special electrodes,
applied one between the middle and upper third of the fore-arm,
the other to the wrist or elbow (Fig. 57).
In the first case there is a descending-ascending, in the second
case an ascending-descending diphasic current, as shown by
arrows 1, 2 of the diagram. This diphasic action current is the
only electrical phenomenon which can be positively demonstrated
for skeletal muscle on living man.
The ascending current in the arm after a voluntary contraction
of the muscles (du Bois-Eeymond) is not a muscular action
VOL. Ill G
82
PHYSIOLOGY
CHAP.
current, but a secretory skin current, as was shown by Hermann
and Lucb singer.
A. D. Waller succeeded in demonstrating the electrical changes
that accompany contraction of cardiac muscle in intact animals
and man. He used Lippmann's capillary electrometer, by which
he was able to record not only the diphasic variation that accom-
panies the beats of the human heart, but also the simultaneous
distribution of electrical potential in the remainder of the body.
In connecting the different points of the cutaneous surface witli
the capillary electrometer, he obtained the results shown in
Fig. 58. If the two electrodes are placed on the two points A
and B, or other more remote points ab, situated at either side of
the oblique equatorial line 00, along which the potential is zero,
the mercury of the capillary moves synchronously with the beats
FIG. 59.— Cardiograms of human heart, c c, and simultaneous diphasic variations. (A. D. Waller.)
Time tracing, 1 1, in T\, sec. The electrode connected with the sulphuric acid went to the
mouth, that with the mercury to the left foot.
of the heart. This does not occur if the electrodes are applied to
two points on the same side of the equatorial plane. If the
oscillations of the mercury are closely watched or photographed
it can be seen that a diphasic variation corresponds with each
systole (Fig. 59).
We have elsewhere described Gaskell's important discovery on
the cardiac muscle of the tortoise when arrested by Stanuius'
upper ligature (Vol. I. p. 332). He found on leading off a
demarcation current excited by injury of the surface to the
galvanometer, and then exciting a branch of the vagus, that the
variation was not negative, but positive, i.e. the demarcation
current was reinforced, not weakened. From this observation he
concluded that the vagus has an anabolic action on the heart, as
opposed to the katabolic action of the sympathetic. As dis-
integrative explosive stimuli produce a negative potential in the
active segments of the tissue as compared with the non-active, so
integrative processes which spread as a wave of inhibition, after
GENERAL PHYSIOLOGY OF MUSCLE
83
stimulation of the diastolic nerves, produce a positive potential in
the inhibited segments in relation to those at rest.
At the International Congress of Physiology in Turin (1901)
Fano communicated another interesting observation on the tortoise
heart, which agrees well with Gaskell's theory, and also helps to
interpret the diphasic character of the current of action. If while
the photograph of the normal diphasic current or electrical beat
of the heart is being recorded the vagus is excited by a slight
stimulus, which does not arrest the heart completely but only
FIG. 60. — Electrical beat of right auricle of tortoise heart, and its reversal during excitation of
vagus. (Fano.) Ad, photograph of beat of right auricle ; Pe, photograph of its electrical beat
or diphasic variation ; Vd, line showing duration of gentle stimulation of right vagus.
slows down the beat and diminishes the amplitude of the systole,
there is usually a profound alteration in the form of the photo-
graph, which consists in the marked diminution, sometimes the
almost total disappearance, of the negative phase, with a simul-
taneous increase in the second or positive phase. There is, in fact,
a complete reversal of the electrical beat of the heart (Fig. 60).
The same sometimes occurs after, instead of during, the
stimulation of the vagus, when the systolic wave is gradually
increasing towards its normal.
This reversal of the electrical beat during or after vagus
excitation depends on the inhibitory or diastolic action of this
nerve, since it does not occur after the application of atropine to
the heart.
84 PHYSIOLOGY CHAP.
According to Fano the reversal of the diphasic curve proves
that it does not depend solely, as is usually assumed, on a wave of
negativity spreading from the near points to those more remote
from the stimulus, but is due to a wave of positivity immediately
following the former. In the normal electrical tracing, too, the
relations between the two phases, negative and positive, vary—
the first predominating in some cases, the second in others. It is
not improbable that these different types of the electrical curve
depend on the relations between the katabolic and anabolic
processes of cardiac muscle, and that stimulation of the vagus
exaggerates the latter.
XII. The innumerable physical, chemical, and histological
researches 011 muscle which have thus been briefly summarised
have yielded an extraordinary wealth of physiological data, from
which some solution of the difficult problem of the origin of
muscular force may be constructed — some hypothesis able to
explain the internal mechanism on which the contraction and
relaxation of the muscle depends, or more generally, its capacity
for passing suddenly from the state of comparative rest to that of
activity, and vice versa.
An exhaustive theory of the mechanism of muscular excita-
bility must cover a series of difficult problems, among which are
the following :—
(a) How is the excitation of the nerve end-plate transmitted
to the muscle fibre ?
(6) On what does the sudden contraction (isotonic) and elastic
tension (isometric) depend ?
(c) What process gives rise to the sudden relaxation of the
muscle, i.e. the cessation of the elastic tension on which shortening
depends and the production of the elastic tension to which lengthen-
ing is due ?
(rf) How are the excitatory impulse and the wave of contraction
and relaxation conducted along the muscle fibre ?
Speaking generally, it may be said that these and other
problems have at present received no proper scientific solution,
so we must confine ourselves to a critical investigation of the
principal hypotheses that have been put forward.
It is now universally agreed that the physiological combustion
of certain chemical constituents of the tissue which are bound up
with the protein molecule or intimately connected with it, are the
prime source of muscular energy, and that the transformation of
potential chemical energy into mechanical energy, either in the
form of elastic tension or in that of external work, is performed
according to the law of the conservation of energy. There is a
general tendency to consider the chemical state of the resting
muscle substance as one of unstable equilibrium, in which the
atoms of oxygen and the groups of combustible atoms which form
i GENERAL PHYSIOLOGY OF MUSCLE 85
part of the great protein molecule are so close together that a very
weak stimulus suffices to bring about an explosion, in which most,
of the oxygen atoms combine with atoms of carbon and hydrogen
to form carbonic acid and water. It is more difficult to explain
why the explosion is confined to a small part of the explosive
mass instead of discharging it completely, as in the case of a
loaded tire-arm. But the universally accepted principle is that
the potential chemical energy of the muscle substance is the primary
source of muscular energy in all its manifestations.
How does the explosive reaction of the muscle produce its
shortening or elastic tension ? The answers to this question are
by no means unanimous, and physiologists differ, according as the
one or the other sign of muscular activity receives the more con-
sideration from them.
We need not discuss the earlier hypotheses which are collected
in the classical text-books of Haller (1792) and Johannes Miiller
(1844), but may confine ourselves to the later and more probable
theories, commencing with that of E. Weber.
Schwann had already suggested that muscle acts by elastic
forces, but Weber was the first to clear up the obscurity that
prevailed as to contractility and elasticity in his classic work on
Muskelphysik, published 1846. According to the theory formulated
by Eontana elasticity is an inherent physical property which tends
to preserve the natural form of the muscle, and thus acts in the
contrary sense to contractility, i.e. it limits the contraction and
brings the muscle back to equilibrium as soon as the active state
ceases. But Weber pointed out that the natural form of the
muscle which depends on its elastic equilibrium is not constant,
but rnrii-s freely with the external and internal conditions of the
life of the muscle. As a metal rod lengthens when heated, and
shortens again on cooling, because different degrees of temperature
alter the equilibrium of its atoms and produce a reaction of its
elastic forces which expand in the first case and contract in the
second, so the molecular arrangement differs in the muscle accord-
ing as it is at rest or excited, and its external form differs
accordingly. The active muscle is short and thick, the inactive
long and thin, and in suddenly passing from one state to the
other the muscle contracts or expands, not against the elasticity,
but by an elastic reaction in order to assume the natural form of
equilibrium which corresponds to its active or inactive state. On
Weber's view the extension of a muscle by a weight is not com-
parable with the shortening due to a stimulus : the weight stretches
the muscle against its elastic forces ; the stimulus, on the contrary,
causes a sudden alteration in its chemical equilibrium, and therefore
in the elastic forces, which are the immediate cause of contraction.
Weber was the first who submitted the elasticity of muscle,
and the changes it undergoes in various conditions, to strict
86
PHYSIOLOGY
CHAP.
investigations. He found that muscle has a low but perfect
elasticity ; it can be readily extended by small weights, but
promptly returns, under normal conditions, to its initial length,
when the extending force ceases to act on it. He recognised
that, unlike inorganic, but like certain organic substances, the
elongation of the muscle is not proportional to the weight, and
becomes less so as the load increases ; so that the curve of extensi-
bility obtained when the weights are plotted on the abscissae,
and the elongations taken as ordinates, is not a straight line but
a curve, which Wertheim subsequently recognised as a hyberbola.
Weber compared the elasticity of the resting hyoglossus
muscle of the frog with that of the same frog 'when tetanised, by
m
FIG. 61. — Diagram to show elasticity of muscle in rest and in activity. A B, length of unloaded
resting muscle ; A b, same muscle in activity. A' B', A" B", length of resting muscle loaded
with regularly increasing weights ; A' b', A" b", length reached by active muscle loaded with
same weights. The line B B' B" . . . y x gives the elasticity curve of resting, b If b" . . . y, of
contracting muscle.
comparing the curves of extensibility to regularly increasing
weights during rest and in tetanus. He found that the active
muscle is less elastic, i.e. more extensible than the inactive
(Fig. 61). '^Therefore the extensibility curve of active muscle
falls more rapidly than that of resting muscle. With progressive
increase of load a point is reached at which the two curves meet.
This happens when the weight is sufficiently great to hinder
contraction, i.e. when the elastic tension in the muscle due to
the weight is in complete equilibrium with the opposite elastic
tension which is actively set up by the stimulus. If, after
reaching this point, the muscle is further overloaded and then
stimulated, there will not only be no contraction, but, on the
contrary, a certain degree of elongation due to the decrease in
muscular elasticity after stimulation, so that the elasticity curve
of the active state crosses the elasticity curve of the resting state
(Weber). But this has not been confirmed by later workers, who
i GENEEAL PHYSIOLOGY OF MUSCLE 87
hold with Tick that the two curves tend to converge asymptotic-
ally without meeting.
These studies of Weber on the elasticity curve of resting and
active muscle were subsequently confirmed and extended with
better methods by Marey (1868) and Blix (1874) on excised frog
muscles ; by Bonders and Van Mansvelt (1863) and by Chauveau
and Laulanie (1899) on human muscles.
Other work on muscular elasticity has shown that it varies
under the influence of different toxic and medicinal substances.
In this connection Eossbach's and Anrep's observations (1880) on
the frog are striking. These showed that the changes which the
elasticity of muscles loaded with low weights (2 grms.) undergoes
by the action of certain poisons may be utilised as a good method
of toxicological analysis. They found that curare and cocaine,
which paralyse the motor or sensory nerve -endings, produce
elongation of the muscle (lowering of tone) without perceptibly
affecting elasticity ; pliysostigmine, in addition, causes an increase
of elasticity by acting on the contractile substance ; digitaline
causes elongation of the muscle and increase of its elasticity,
independent of the action of the nerves, i.e. by direct action on
the contractile substance ; veratrin (injected in doses of 1-5 mgrms.)
produces first elongation, then contracture of the muscle, inde-
pendently of the nerve, and in both stages depresses the elasticity
and makes it imperfect ; lastly, potassium salts shorten the muscle
and simultaneously increase its excitability, while sodium salts in
the same dose and same concentration produce no visible change
either in the length or the elasticity of the muscle.
Progressive muscular fatigue, too, alters elasticity in the same
way as poisons, raising it in the first stage, and subsequently
decreasing it in proportion as contracture sets in. After death,
when rigor mortis begins, muscle is highly elastic, that is, but little
extensible, and its elasticity simultaneously diminishes, for when
the traction is removed it no longer returns to its initial length.
All these and other experimental observations confirm Weber's
theory, and show that elasticity is not a constant physical property
of the muscle, but is perhaps the most variable and least stable of
all its properties.
But Weber's assertion that the contraction of the muscle
is only the result of a sudden change in its elasticity, due to
the chemical changes produced by excitation, is no more than
a schematic restatement, whatever its theoretical value. Its
simplicity, however, signalises a considerable advance in mechanical
notions of muscular activity ; for, by excluding Fontana's theory,
which assumes contractility and elasticity to be two opposite or
antagonistic properties, it leads on logically to the formulation of
a more exact idea, harmonising better with the facts, of the process
by which relaxation follows on the contraction of the muscle.
PHYSIOLOGY CHAP.
By many authors muscular relaxation has been, and still is,
regarded as a simple effect of the cessation of contraction. This
is Fontana's theory that contraction throws the muscle into
elastic tension, so that when the contraction ceases the muscle
lengthens owing to its elasticity. But if contraction is not con-
trary to elasticity, it is plain that the muscle can only relax by a
chemical process which is opposed to that of contraction, owing
to which its form changes in a direction opposite to that of the
contraction phase. As early as 1874 \\e pointed out this logical
consequence of Weber's theory, and added further, " If the con-
traction, which is due to a fresh molecular arrangement to which
a shorter natural form of the muscle corresponds, be termed actin ,
we are equally justified in calling the elongation of the muscle
active, since it too is associated with a new molecular equilibrium
which accompanies the process of relaxation." Years after (1887)
Gaskell made the important discovery that electrical phenomena
accompany the inhibition of cardiac muscle by the vagus, and
disproved the hypothesis that the contraction of this muscle is
due to kat<tl>»/ir and its relaxation to un<tl>uli<: chemical processes
(Vol. I. p. 332). More recently Fano (1901) extended this theory
(see p. 83), which in our opinion applies not merely to the heart,
but to all other muscular tissues.
No special advance upon Weber's hypothesis has been made
by the physiologists who refer the transformation of the potential
chemical energy developed in muscle after excitation into
mechanical energy, to the direct effect of a special form of
chemical alteration. Pfliiger, in his famous memoir,1 accepts
this theory of the origin of muscular energy without enlarging
on it. Pick 2 expresses himself more clearly, and states that " the
chemical forces of attraction must a 2»'iori be more or less pre-
disposed in the direction of the mechanical action which is to
follow, and participate directly in the same." Chauveau 3 remarks
that "muscular contraction is a derivative of chemical work."
This theory seems no less artificial than that of Weber.
According to Engelmann, moreover, it is irreconcilable with the
fact that during contraction an infinitely small portion of the
muscle substance is chemically active as compared with the total
mass of the muscle which remains passive. He points out that
the muscle contains 70-80 per cent water, and that the greater
part of the 20-30 per cent of the organic substances and minerals
of which it is composed take no chemical part in the process. Of
the carbo-hydrate group associated with the protein molecule,
which gives rise during excitation to the formation of C02 and
H.,0, only small proportions are simultaneously affected. On
1 Ueber die pJiysiologische Verbrennung in den lebcndif/en Organismen (1875).
2 Mechanische Arbeit und Wcirmeentwickluny lei der Muskcltatiykeit (1882).
3 Publications on Muscular Work and Energy (1891).
i GENEKAL PHYSIOLOGY OF MUSCLE 89
Engelmanu's calculation the source of the energy necessary to
produce a contraction amounts to about four uiillionths of the
entire mass of the muscle. It is inconceivable to Engelmann
that the movement of the relatively enormous mass of inert
substance should be effected by the direct chemical attraction of
this minimal fraction of active substance, no matter what the
natural form or magnitude of the vibrations or the particular
arrangement of the few active molecules. He further objects that
the hypothesis of direct chemical attraction does not take into
account the tibrillary structure of the contractile apparatus, the
differentiation of the fibrils into isotropous and anisotropous
portions, the opposite variations in volume, form, refrangibility,
extensibility, etc., of these parts, and a number of other facts
which are in more or less open contradiction to it.
Engelmaun holds the thermodynamic theory propounded by
J. K. Mayer (1845), according to which the muscle is compared
with a steam engine which transforms the heat evolved in com-
bustion into mechanical work, to be far more probable.
In reply to Solway's criticism that the muscle works more
economically than any engine, Engelmann remarks that the
muscle is an apparatus whose combustible materials burn in
direct contact with the parts that perform the mechanical work,
so that it works under far more favourable conditions than Watt's
thermodynamic machine.
Another, apparently more serious, objection to the theory of
the thermal origin of muscular energy put forward by Fick (1882),
and repeated by Gad, is that it is irreconcilable with the second
of Glausius' fundamental laws of thermodynamics. According to
this law, heat can only perform work when it passes from a warmer
body (A} to a cooler body (B}, and its potential is proportional to
the difference of temperature between A and B. So that before
we can assume that muscle works like a thermodynamic machine,
we must first prove that there is in it a marked difference between
A and B, or between the source of heat and the surrounding
medium.
Fick held that this is not the case with muscle, which only
exhibits slight differences of temperature, proving conclusively
that it does not act as a thermodynamic motor.
Engelmann replied to this objection that Pflliger had already
pointed out in 1875 that body-temperature is only an arithmetic
mean which comprises innumerable very different temperatures
at innumerable different points of an organ, and that the molecules
formed in physiological combustion have, at least at the moment
of formation, an extremely high temperature, which they lose at
once by giving off heat to the cooler matter that surrounds them.
Pfliiger's conclusions in so far as muscle is concerned are con-
firmed, according to Engelmann, by the fact that the combustion
90
PHYSIOLOGY
CHAP.
of a comparatively small number of molecules suffices to produce
contraction, which can only be explained on the assumption that
at the moment of oxidation they acquire a temperature so high
that their minute size and low number are perhaps the only reason
why they do not appear
b incandescent. The rise of
temperature in the total
mass of the muscle, even
granting that it only
amounts to O'OOl0 C. for
one contraction, is when we
consider the great specific
heat of the muscle sub-
stance--i.e. the large
quantity of heat necessary
to raise its temperature-
conceivable only on the
supposition that each heat-
producing molecule has at
its birth an enormous tem-
perature in comparison
with the immense mass of
substance able to conduct
and permeable to heat, by
which it is surrounded.
In this assumption it is
implicitly recognised that
the muscle presents to a
high degree the funda-
mental condition for the
conversion of heat into
mechanical work. This
conversion — according to
Engelmann — is effected by
the anisotropous substance
which forms the positive,
doubly refracting elements
with one axis parallel to
the direction of contraction
which he terms inotagmata.
He supposes that in mus-
cular excitation the inotag-
mata, warmed by the heat
generated in the thermogenic molecules, swell up and shorten,
owing to imbibition of the more fluid isotropous substance that
surrounds them. This alternate swelling and shortening of the
inotagmata arranged in longitudinal series results in the whole
Fio. 62. — Engelmann's apparatus for imitating the con-
traction and relaxation of muscle on a violin string.
A string 5 cm. long soaked in water is fixed by its
lower end a to a rigid support b, and connected above
by a strong silk thread to the short arm of the lever
H, which moves round the axis c. By means of the
movable weights d and d' the string can be thrown
into the desired tension, and the position of the lever
regulated by screw e. The string is surrounded by a
thin platinum wire /, which turns spirally round it,
and is soldered at the end to thick copper wires con-
nected with the poles of two Grove or Bunsen cells.
The string, platinum wire, and support are placed in
a wide low beaker filled with water, into which a
thermometer is introduced. When stretched by at
weight of 25-50 grms. the string after a few minutes
ceases to expand, and the end of the lever remains
steady. If a current is then passed through the
spiral for a few seconds, the lever rises at once with
great rapidity, and on breaking the circuit it returns
almost to its original level, while the thermometer is
either stationary or shows a hardly appreciable rise
of temperature.
i GENERAL PHYSIOLOGY OF MUSCLE 91
muscle in the formation and propagation of the contraction wave,
by which a part of the heat is transformed into mechanical work.
To strengthen this ingenious hypothesis Engelmann devised
an experiment, in which the contraction of the muscle, owing to the
swelling and shortening of doubly refracting particles in the long
axis in accordance with the therrnodynamic law, is imitated on
a violin string. He started from the fact that the property of
contracting in heat is not peculiar to muscle, but is inherent in
different degrees in all living tissues, and even in other organic
substances that contain a doubly refracting substance, e.g. a violin
string or specially prepared string of non- vulcanised indiarubber.
Engelmann's model is shown in Fig. 62. He proved that under
definite experimental conditions a moistened violin string, thrown
into tension by a weight, thickens and shortens and does a certain
amount of work when heated by a coil of platinum wire traversed
by an electrical current, and lengthens again on cooling when
the current is interrupted. In this experiment the violin string
which contains the doubly refracting substance represents the
inotagma or anisotropous element of the muscle ; the vessel
filled with water the aqueous, isotropous muscle substance; the
platinum coil the thermogenic molecules; the closure of the
galvanic current the excitation of the inotagrnata which gives
rise to contraction ; the opening of the circuit the cessation of
excitation from which relaxation results. Nothing but the
transmission of excitation along the series of inotagmata which
causes the transmission of the contractile wave is absent in this
ingenious model.
On recording the contractions and subsequent elongations of
the violin string on a revolving drum, Engelmann obtained
chordogra/ns which resemble myograms to a surprising degree
(Fig. 63). This proves that they depend on a cyclic process — as
after the warming which leads to shortening, the string lengthens
and returns (at least approximately) to its initial state on cooling.
It may be objected to Engelmann's theory that it takes no
account of the electrical phenomena that occur in the muscle.
Before meeting this objection it is well to consider the different
hypotheses that have been put forward in favour of an electrical
origin of muscular energy.
Prevost and Dumas, Meyer and Amici compared the muscle,
owing to its striated structure, with a Volta's pile, which also
consists of discs. Voit, starting from the negative variation,
assumes that the muscle current diminishes in contraction, because
a part of the electricity developed in the muscle is transformed
into movement. Krause and Kiihne compared the motor end-
plates to the electrical organs of Torpedo, and the action of nerve
on muscle to the discharge of a Leyden jar. According to du
Bois-Reymond, on the contrary, it is the wave of negative
92
PHYSIOLOGY
CHAP.
variation (i.e. the current of action) which causes the transmission
of excitation from the nerve to the muscle, and the spread of the
contraction in the latter. According to d'Arsonval the thermal
phenomenon and mechanical work of the muscle are the effects of
the electrical phenomenon ; the chemical energy is transformed
FIG. 63. — Chordograms obtained by Engelmann with the apparatus described in preceding figui '<',
with the violin string loaded with 50 grins, and a lever that magnified fifty times. /, At a a
strong current was passed through the spiral for 2-3 sees. ; at b a weak current for a longer
time, a shows a shorter latent period, a sharper and more rapid rise, and a steeper descent
than b. II and ///, Uniform strength of current, but the temperature of the water was 35° C.
in //, 45° C. in ///. IV, After removing the water the warmth of the spiral was conveyed to
the string by the air which was at a temperature of 1S° C. At a a stronger current was passed
than at b. As the cooling of the string had been accelerated, it expanded more rapidly.
]', The curve falls still more rapidly, owing to accelerated cooling of the string due to a
stronger current of air. Time marking = 0'5 sec.
into electrical energy, and this again into thermal and mechanical
energy.
All these hypotheses are too vague and indefinite, and they
neglect certain well-established experimental facts.
G. E. Miiller of Gottingen (1889) put forward a pyro-electrical
theory of the origin of muscular force, which, although partially
i GENERAL PHYSIOLOGY OF MUSCLE 93
founded on arbitrary hypotheses, is certainly more definite. He
attributes the contraction of the muscle to the electrical attraction
and repulsion of the doubly refracting crystalloids, the poles of
which undergo a change of electrical state owing to the heat that
is generated. On this theory the muscle shortens as its tempera-
ture rises ; and when the temperature of the crystalloids becomes
constant it lengthens, because the electrical changes subside.
Engelmann's experiments show, however, that the length of the
muscle does not depend on the rate at which the temperature
rises, but on the absolute temperature present at the moment in
the doubly refracting discs. They further show that when the
temperature in these discs is constant, the muscle does not
lengthen, but remains indefinitely shortened.
Certain well-authenticated facts prove that there is a direct
association between the electrical and mechanical phenomena in
muscle. As long ago as 1855 Helmholtz showed by an exact
chronometric method that the electrical wave precedes the
mechanical in skeletal muscle. The same fact was demonstrated
in 1856 by Kiilliker and H. Miiller by the experiment of secondary
contraction, and by Bernstein with his differential rheotome. In
the nerve-fibres, in which no sign of mechanical phenomena can
be detected, and little heat development or chemical activity,
electrical phenomena similar to those of the muscle occur, which
proves them to be quite independent of the phenomena of con-
tractility. Certain important researches of Biederniann (1880)
favour the same conclusion, since they prove that frog muscles
which have lost their power of contracting by imbibition of water
or the effect of ether vapour preserve their electrical excitability
and capacity for conducting intact. From this Biederrnanu
concludes that the capability of actively changing its form at the
seat of direct stimulation is not an indispensable condition of the
excitation of muscle.
The independence of the electrical phenomena from muscular
contractility is also demonstrated by the fact that the majority
of electric and pseudo-electric organs develop at the expense of
the striated muscle fibres, and that during this development,
according to Ewart, contractility is gradually lost, while the
electromotive function develops in proportion. According to
Baglioni (1906) the chemical composition of the electrical organs
differs fundamentally from that of the muscles.
On the strength of all these facts Engelmann founded his
hypothesis that in muscle the particles on which the development
of the electrical phenomena depends are quite distinct from those
which supply heat by combustion (thermogenic], and those which
subserve mechanical work (inogenic particles').
The first are solely concerned with excitation and its con-
duction and propagation, as Hermann also concluded from the
94 PHYSIOLOGY CHAP.
fact that the wave of negativity at the point of the muscle
stimulated appears hefore and precedes the wave of contraction.
These particles probably lie chiefly in the isotropous layers which
take no active part in contraction. The thermogenic particles,
on the contrary, are in close contiguity with the inogcnic particles,
which are represented by the doubly refracting elements of the
anisotropous layers, on which the specific function of the muscle,
i.e. contraction, depends. According to Engelinann's theory this
is due to the conversion of heat into work.
Verworn (1895), starting from a hypothesis put forward by
Berthold (1886), has formulated another theory of contraction,
which includes all the movements of all forms of living matter,
from amoeba to muscle. On this theory movement is due to
changes in the surface tension of the histological elements of
which the muscle fibrils consist (isotropous and anisotropous
discs) ; these changes in surface tension are due, according to
Verworn, to chemical processes.
A similar theory, by which muscular contraction is referred to
changes of surface tension, has been put forward by other physio-
logists, as d'Arsonval, Imbert, Bernstein, Jensen, and Galeotti.
Galeotti holds (1906) that the changes in surface tension of the
different muscle elements are due to electrochemical phenomena.
None of these theories, however, take into account the whole
of the active changes concomitant with muscular activity.
BIBLIOGRAPHY
Structure of Muscle and its Visible Changes during Activity :—
ENGELMANN. Pfliiger's Archiv, xi., 1875, xxv., 1881.
RANVIER. Lemons d'anatoniie gunerale sur le systeme musculaire. Paris, 1880.
ROLLET. Denkschr. der AViener Akademie, xlix. and li., 1885, Iviii. 1891.
Mechanical, Thermal, and Electrical Activity of Muscle: —
HERMANN. Handbuch der Physiologic, i. 1879.
CH. RICHET. Physiologic des muscles et des nerfs. Paris, 1882.
BIEDERMANN. Elektrophysiologie. Jena, 1895. (English translation by F. A.
Welby, 1896.) Ergebnisse d. Physiol., II. Part 2, 1903.
A. FICK. Mechan. Arbeit und Warmeentwickelung bei der Muskeltatigkeit.
Internat. wiss. Bibliothek, 1882.
ROSENTHAL. Allgemeine Physiol. der Muskeln und Nerven. Leipzig, 1899.
W. EINTHOVEN. Pfliiger's Archiv, lx., 1905 ; Arch, intern, d. Physiol., iv. 1906.
I. BERNSTEIN. Pfliiger's Archiv, Ixxxi., 1901.
G. GALEOTTI. Zeitschr. f. allg. Physiol., vi., 1906.
HOFMANN. Pfliiger's Arch., xciii., xcv., ciii., 1902-4.
BORUTTAU. Pfliiger's Arch., cv., 1904.
0. FRANK. Thermodynamik des Muskels. Ergeb. d. Physiol., III. Part 2, 1904.
Chemical Composition and Metabolism of Muscle : —
HALLIBURTON. Text-book of Chemical Physiology and Pathology, 1891.
NEUMEISTER. Lehrbuch der physiologischen Chemie, 1895.
H. WINTERSTEIN. Pfliiger's Archiv, cxx., 1907.
v. FURTH. Ergeb. d. Physiol., I. Part 1, 1902 ; II. Part 1, 1903.
i GENEKAL PHYSIOLOGY OF MUSCLE 95
Ergograph work :—
A. Mosso. Arch. ital. de biologic, xiii., 1890.
A. MAGGIORA. Ibidem.
P. W. LOMBARD. Ibidem.
PATUIZI. Archives ital. de biologic, 1892, 1893, 1901.
Z. TREVES. Ibidem, xxix., xxx., xxxi., 1898-1900.
F. SCHENCK. Pfliiger's Archiv, Ixxxii., 1900.
General Theory of the Genesis of Muscular Force, in addition to the treatise by
Hermann, see : —
TH. W. ENGELMANN. Snr 1'origine de la force mnsculaire. Archives neerlandaises,
xxvii., 1893.
VERWORN. Allg. Physiologie, 4th Ed. Jena, 1903.
JENSEN. Pfliiger's Arch., Ixxx. , 1900.
BERNSTEIN. Pfliiger's Arch., Ixxxi., 1901 ; cv., 1905. Die Krafte der Bevvegung
in der lebenden Substanz. Brunswick, 1902.
GALEOTTI. Zeitschr. f. allg. Physiol., vi. , 1906.
Recent English Literature :—
MAoDoNALD. The Structure and Function of Striated Muscle. Quart. Journ. of
Experiment. Physiol., 1909, ii. 5.
LANGLEY. On the Contraction of Muscle, chiefly in relation to the Presence of
"Receptive" Substances. Journ. of Physiol., 1907, xxxvi., 347; 1908,
xxxvii. 165 and 285 ; 1909, xxxix. 235.
KEITH LUCAS. On the Refractory Period of Muscle and Nerve. Journ. of Physiol.,
1909, xxxix. 331.
KEITH LUCAS. All-or-None Contraction of the Amphibian Skeletal Muscle Fibre.
Journ. of Physiol., 1908, xxxviii. 113.
KEITH LUCAS. On the Relation between the Electric Disturbance in Muscle and
the Propagation of the Excited State. Journ. of Physiol., 1909, xxxix. 207.
A. V. HILL. The Absolute Mechanical Efficiency of the Contraction of an Isolated
Muscle. Journ. of Physiol., 1913, xlvi. 435.
BANCROFT.. The Electrical Stimulation of Muscle as dependent upon the Relative
Concentration of the Calcium Ions. Journ. of Physiol., 1909, xxxix. 1.
LILLIE. The Relation of Ions to Contractile Processes. Amer. Journ. of
Physiol., 1909, xxiv. 459.
KEITH LUCAS. Summation of Adequate Stimuli in Muscle and Nerve. Journ. of
Physiol., 1910, xxxix. 461.
MINES. Summation of Contractions. Journ. of Physiol., 1913, xlvi. 1.
KEITH LUCAS. On the Transference of the Propagated Disturbance from Nerve to
Muscle, with special reference to the apparent Inhibition described by
Wedensky. Journ. of Physiol., 1911, xliii. 46.
MAcDouoALL. Mental and Muscular Fatigue. Reports, 80th Meeting, British
Assoc., 1911, 292.
BURRIDGE. An Inquiry into some Chemical Factors of Fatigue. Journ. of Physiol.,
1910, xli. 285.
KEITH LUCAS. On the Recovery of Muscle and Nerve after the Passage of a
Propagated Disturbance. Journ. of Physiol., 1910, xli. 368.
A. V. HILL. The Energy degraded in the Recovery Processes of Stimulated Muscle.
Journ. of Physiol., 1913, xlvi. 28.
HILL. The Heat produced in Contraction and Muscular Tone. Journ. of Physio!.,
1910, xl. 389.
MEIGS. Heat Coagulation of Smooth Muscle. Amer. Journ. of Physiol,, 1909,
xxiv. 1.
CHAPTER II
MECHANICS OF LOCOMOTOR APPARATUS
CONTENTS. — 1. General remarks on the structure of the bones and their
articulations. 2. Form, attachments, and mechanics of muscles in relation to
bones. 3. Line and centre of gravity of the body in different postures.
4. Mechanics of equilibration in different postures. 5. Movements of the body
in walking. 6. Movements of the body in running. 7. Movements of the body
in swimming. Bibliography.
THE muscles are the active organs — the bones, cartilages, ligaments,
etc., which build up the skeleton to which the muscles are attached
represent the passive organs — of a highly complex system to which
Marey correctly applied the term animal machine. In industrial
machines also it is usual to distinguish between the active parts
which are the seat of the production or development of the energy
destined to be transformed into useful work, and the passive parts
which transmit it, and which consist — as in the animal machine—
of levers, pulleys, inclined planes, pumps, etc.
Our principal task in this chapter will be to study the complex
motor apparatus, consisting of an elaborate system of skeletal
muscles, on the co-ordinated action of which depend the loco-
motor movements, i.e. the different forms of displacement of the
body as a whole. These are distinguished from the partial move-
ments or displacements of the limbs, by which the relations of the
different mobile parts of the body are altered. In the former the
base of the body is displaced ; in the latter it may remain immobile.
In the study of these motor functions the physiologist's task is
to a large extent linked with that of the anatomist. It is, in fact,
impossible to form a clear conception of the mechanism of a move-
ment carried out by the active participation of many different
muscles without first knowing the points of attachment of each
muscle as well as the form and articulation of the bones, which act
passively as the levers. But while the anatomist is occupied more
particularly with the mechanical action of each muscular unit, the
physiologist supplements this by the synthetic study of the co-
ordination of the various muscular forces which combine in the
accomplishment of each separate motor act.
96
CHAP, ii MECHANICS OF LOCOMOTOR APPARATUS 97
I. Historical investigation into the action of the muscles on
the skeleton, aiid the mechanism of posture and locomotion, com-
menced with Borelli's classic De motu animalium, published in
1680. The writings of Barthez (1798) and of Gerdy (1832) con-
tain no real advance on the work of Borelli. Poisson (1833)
first attempted to calculate the work which a man performs in
walking. Eeal progress in this direction was made in the classical
publication of W. and E. Weber, Die Mechanik der menschlichen
Gehwerkzeuge, which appeared in 1836. The second half of the
nineteenth century brought many anatomical studies on the form
of the articular surfaces, and the significance of the ligaments, the
articular capsules, fascia, etc., more especially from Henke, Langer,
and H. Meyer. Among standard works Duchenne's Pliysiologie
des mouvements deserves mention, owing to the positive character
of the research and the accuracy of the descriptions, although it
does not compare in originality with the epoch-making researches
of Borelli and the Webers. After the application of the graphic
methods, more particularly by Marey and Carlet (1872), the study
of locomotion was carried to greater perfection. Still greater
advances were made after instantaneous photography had been
applied to the study of the successive phases of movement in man
and other animals, first by Muybridge, subsequently by Marey
(1882) and his successors with more perfect kinernatographic
methods.
As a preliminary we require a general notion of the structure
of the bones, the passive organs, and the action of the muscles,
which are the active organs of movement.
Taken as a whole, the bones may be regarded as rigid organs
in comparison with the forces which act on them during the
movements of the body. The ribs are an exception to this rule,
since (Vol. I. p. 407) they undergo a slight degree of flexion and
torsion round their long axis during thoracic inspiration.
To the student of animal mechanics the histological structure
of the bones, which is more particularly of morphological interest,
appeals less than their architecture, which is such as to combine
the greatest amount of rigidity with the greatest possible lightness,
as first pointed out by H. Meyer in 1867. All the long bones
are hollow, which does not lessen their rigidity, since a hollow
cylinder presents the same resistance to pressure and traction as a
solid cylinder of the same 'diameter and identical material. The
marrow which fills the bony cavity contributes to the comparatively
light weight of bone, since it is rich in fat. The trabeculae which
constitute the spongy part of the extremities of the long bones are
so arranged as to support the surfaces destined to bear the greatest
pressure.
The application of this mechanical principle is to be found in
all bones, but it is specially obvious in the femurs.
VOL. in H
98 PHYSIOLOGY CHAP.
The head of the femur is united obliquely by its neck to the
shaft of the bone, at an angle which usually diminishes during the
period of growth under the influence of the weight of the body, and
varies in the adult from 110° to 140°. In the shaft of the femur,
which is by far the larger portion, the compact bone forms a tube
with thick, solid walls, filled with marrow which is largely fat.
Fin. M. — Section through the end of a femur. (Zaaijnr.)
But at the upper end of the femur, including the head, neck,
and trochanters, in consequence of the obliquity of the head to the
longitudinal axis of the bone the conditions for obtaining the
necessary strength become extremely complex, since the compact
substance of the tube extends (Fig. 64) into a system of lamellae
arranged fanlike so as to support the surfaces destined to bear the
greatest pressure.
It should be noted that when from pathological conditions, for
ii MECHANICS OF LOCOMOTOE APPARATUS 99
instance, articular anchylosis, and after amputations or resections,
the mechanical requirements to which the bones naturally conform
are changed, the systems of lamellae of the spongy substance alter
considerably.
The enlargements usually presented at the ends of the long
bones, the ridges, tuberosities, and spines are for the purpose of
giving the muscles large and adequate surfaces of attachment.
The bones of which the skeleton is made up are united rigidly
together, or in such a manner as to permit a more or less extensive
displacement and movement on each other. The bones united by
sutures (sytiarthroses), as those which compose the cranium, are
perfectly immobile ; those united by means of cartilages (synchon-
droses) are semi-mobile, or admit of very limited movements. Such
are the syrnphyses of the pubis and innominate bone and the
synchondroses of the ribs and vertebrae. Finally, the bones
united by articular capsules are semi- mobile (ampliiartlirose},
mobile (artlirose), or very mobile (diarthrose*), according to the
form of the articulation. The articulations of the carpal and
tarsal bones belong to the first category ; the elbow, knee, and ankle
to the second ; the shoulder and hip-joints to the last.
In all these true articulations the heads of the bone are covered
with a layer of cartilage, to the edges of which the fibrous articular
capsule, which connects the two bones and surrounds the articular
cavity, is attached. Each capsule is covered internally by a pave-
ment epithelium which extends over the joint cartilage, and
secretes the synovia, a colourless, transparent, viscous fluid, formed
by the mucous metamorphosis of the epithelium, which is destined
to lubricate the articular surfaces and enable them to move easily
one upon the other.
Externally, fibro-elastic ligaments strengthen the capsule, and
prevent or limit to a greater or less extent the movements of the
articular heads.
From the physiological point of view, articulations can be
subdivided into the classes proposed by A. Fick. The first
comprises the synchondroses (ribs and vertebrae) and the
arnphiarthroses (joints between the tarsus and carpus). In these
articulations the bony surfaces never change their relations,
and can only be fixed or moved to a limited extent by the
elasticity of the interpolated fibro-cartilages, or pericapsular liga-
ments. The bones thus united are in stable equilibrium, to which
they return immediately when any external cause which has
displaced them from their normal position ceases to act. The
arthroses and diarthroses form the second class, as the articular
surfaces change their relations while moving. The bones thus
articulated are in unstable equilibrium, that is, they remain in
whatever position they are placed by external causes, until this is
removed by some force working in the opposite direction. A
100 PHYSIOLOGY CHAP.
comparatively slight force is consequently able to produce move-
ments of the bones.
In articulations of the second class (arthroses and diarthroses),
which more especially concern us, the bones have articular heads
which are approximately cylindrical or spherical in shape. The
former constitute the hinge joints which move in a single axis ;
one of the articular surfaces is concave, the other convex. Both
are shaped like a section of a cylinder, or more exactly like a cone,
an ovoid, or an ellipse. The articulations of the elbow, knee,
and ankle belong to this class. In the second class of articula-
tions with round heads, the bones can rotate round a single axis,
as in the humero-radial and the atlanto-epistropheal joints, or
round many axes, as in the ball-and-socket joints, represented by
the scapulo-humeral and the hip-joints.
From these articulations with one or many axes, we must
distinguish the articulations with two axes at right angles to
one another, represented by the saddle joints and the con-
dyloid joints. The articular saddle surfaces are convex in one
direction and concave in the plane vertical to it. Such is
the joint between the metacarpal bone of the thumb and the
trapezium bone of the carpus, which permits not only of flexion
and extension, but also of adduction and abduction in two almost
perpendicular axes. The joint between the radius and the bones
of the carpus, which permits the flexion and extension of the
hand, and its abduction and adduction in two axes vertical to
each other, is also a condyloid bi-axial articulation.
In most articulations the surfaces of the bones are not in
complete apposition. There is only a small area of contact
between the head of the femur and the hollow of the acetabulum,
because, as Konig showed, their surfaces are not geometrically
complementary. The gap between the articular surfaces where
there is no direct contact is filled either by the synovia or by
introflexion of the capsular membrane due to external pressure.
These capsular introflexions always have excrescences known as
synovial villosities, which are rich in vessels and lined with
epithelium, to which the formation of synovia is mainly due.
There are consequently no true articular cavities.
However small the area of contact of the articular heads,
it was formerly supposed that it was invariably present, but
Konig found an exception in the scapulo-humeral articulation.
On dissecting frozen subjects he discovered that there was
always a layer of congealed synovia between the two articular
surfaces.
An important but difficult question is, what forces intervene
to resist displacements of the articular surfaces ? E. Weber
attributed this to atmospheric pressure only. He saw that if all
the muscles surrounding the hip-joint in a suspended corpse
ii MECHANICS OF LOCOMOTOR APPARATUS 101
were divided, and the capsular membrane and accessory ligaments
of the articulation were then cut oft* the head of the femur remained
in the acetabulum, and was not apparently displaced. In this
case the entire weight of the lower limb is effectively supported
by atmospheric pressure, which is equivalent to admitting that
a column of air the height of the atmosphere and section equal
to that of the acetabular cavity, would be heavier than the lower
limb, which weighs about 22 kgrms. Weber tried a control ex-
periment. On the same subject he made a small opening from
the internal surface of the pelvis to the acetabulum, and allowed
the air to enter into the joint ; the head of the femur no longer
remained in the cavity, and the limb fell directly the air was
admitted, because the contact of the articular surfaces at the
point of perforation was not so intimate as at the edges of the
acetabulum, where there is a cartilaginous ring which exactly fits
the head of the femur, and consequently the air rapidly penetrated
between the surfaces.
It is, however, known that the results of these experiments are
not applicable to other articulations : if the fingers are stretched
by a traction of not more than 500 grrns., the articular surfaces
of the rnetacarpal-phalaugeal joints come apart. The separation
produces a characteristic sound, and the articular capsule and
surrounding tissue are intraflected to fill the space left by the
displacement of the surfaces of contact.
Besides the atmospheric pressure, the contact of the articular
surfaces is aided by the ligaments which are attached chiefly to
the capsule. This is apparent in the amphiarthrosis of the carpus
and tarsus, which, owing to the shortness, strength, and tension
of the accessory ligaments which strengthen the capsules as well
as to the complex and irregular form of the articular surfaces, are
movable only to a very limited extent. In the arthroses and
diarthroses, on the contrary, which are more freely movable, the
capsules and ligaments serve, not to keep the articular heads in
contact, but rather to limit the movements. In fact they are not
tense when the muscles are at rest, but are thrown into tension
when the moving limb reaches a certain extreme position. In
order to understand the mechanism of the articulations in general,
it is also necessary to take into consideration the tone and state
of contraction of the muscles which surround the joints. Even
in the resting state the muscles are never so relaxed in the normal
individual, as not to contribute to the support of the joints. The
articular contact is opposed by the weight of the limb, as well as
by the pressure at which the synovial juice is secreted, which
cannot be less than that at which the blood circulates in the
capillaries of the synovial tissue. And there must always be
equilibrium between these antagonistic forces. It is not possible
to calculate exactly to what extent atmospheric pressure helps to
102 PHYSIOLOGY CHAP.
support a joint and keep its articular surfaces in contact, although
it is undeniable that this pressure is a considerable factor.
Owing to their conformation the joints and the soft parts
which surround them (muscles, capsules, ligaments) not only
serve to connect the segments of the limbs, but also limit their
movements. Thus the olecranon of the ulna during the extension
of the forearm comes in contact with the dorsal surface of the
humerus, and prevents further extension. The same function
is exerted by the so - called ligaments of arrest ; the lateral
ligaments of the knee-joint, which run from the internal and
external condyles of the femur to the internal condyle of the
tibia and the head of the fibula, are stretched during the extension
of the leg, and limit this movement to 180°.
II. The discussion on the physiology of muscle in Chapter I.
refers particularly to bundles of parallel fibres of uniform
length, in which the total action represents the sum of the
actions of each fibre. But muscles with parallel fibres like
the sartorius and the frog's hypoglossus are rare ; the structure
of the muscle is usually less simple. In addition to long muscles
and short muscles, cylindrical, and spindle-shaped, and flat muscles,
anatomists distinguish fan-shaped muscles, semipennate muscles,
and pennate muscles, according to the direction of the fibres, the
form of the tendons, and the manner in which the muscle bundles
are inserted.
In fan-shaped muscles the different parts may act separately
or all together. The deltoid is a classical example. This muscle
raises the arm forward, backward, or from the side, according
as only the front or back portion or the whole acts. In the
latter case the movement (as occurs when several forces act
simultaneously in different directions) follows the diagonal given
by the parallelogram of the forces, which causes the arm to be
raised in the lateral plane.
Semipennate and pennate muscles are more common. In
these a tendon penetrates deep into the belly of the muscle, and the
muscular fibres run out from it obliquely in one or more directions.
In such muscles the line of junction of the points of attachment
does not coincide with the direction of the fibres, and when the
whole muscle contracts, the effect is the sum of the values,
calculated for each fibre separately. The gastrocnemius, the
biceps, and brachialis anticus, and the flexors for the arm, are
examples of pinnate muscles.
Generally speaking, in muscles with parallel fibres, the
diameter and cross -section is proportional to their strength,
while their length is proportional to the range of the movements
they can produce. But in pennate muscles the strength and
range of the movements cannot be deduced from their section
and apparent length : there are short muscles which appear to be
ii MECHANICS OF LOCOMOTOE APPARATUS 103
long, thick muscles which appear thin. The energy these are
capable of developing is measured, not by the area of the section
vertical to their long axis (anatomical section), but by the area
of a section vertical to the direction of the bundles of fibres
(physiological section) ; and the range of their action is measured,
not by their anatomical length, but by their physiological length,
i.e. the mean length of the muscle bundles of which they consist.
All muscles are not inserted into the bones. The fibres of the
visceral organs — as the heart, bladder, intestines, uterus, as well as
the circular fibres of the oral, pyloric, and anal sphincters — are
only inserted into one another or into the surrounding soft parts.
Other muscles are attached to the bone by one end, and
terminate at the other in soft parts, either on the skin or in the
raucous membrane. Such are the azygos uvulae, the levator
palati, the muscles of the face, the stylo -glossus, the stylo-
pharyngeus, etc. The muscles of the face exert a mutual traction,
making equilibrium with the symmetrical muscles of the other
side ; when the muscles on one side of the face are paralysed, the
mouth consequently becomes oblique.
All the other skeletal muscles are composed of straight fibres,
the two ends of which are generally inserted into tendons of
greater or less length, by which they are attached to two distinct
bones of the skeleton. The majority of the muscles cross only
one joint, that is, they are attached by their two ends to two
contiguous bones, and are therefore uni- articular muscles.
Certain muscles, however, cross two or more articulations, and
are attached to more or less distant bones : these are bi- or multi-
articular muscles. The anterior brachial muscle is uni-articular,
the semi-tendinous is bi-articular, as well as the long head of the
biceps and certain muscles of the leg. In these cases the muscles
and tendons are unusually long, and as they can shorten con-
siderably are able to move two or more articulations simultaneously.
When two bones are connected by a movable articulation, and
a muscle passes from one to the other, this forms a lever. The
skeleton is built up of a vast number of levers, the movements
of which combine among themselves in the most various and
complex forms. The centre of gravity of each limb represents
the point of application of the resistance, that is the weight of
the bony lever, of the soft parts by which this is covered, and
of any extrinsic load which may be carried by the limb. The
point of insertion of a muscle or muscles upon the movable
segment represents the point of application of the force. Finally,
the fulcrum of the lever is represented by the articular surface
of the moving bone upon the articular surface of the fixed bone,
or by the ground, or any other fixed support on which the
limb rests.
It is rare to find that one of two interarticulated bones is
104
PHYSIOLOGY
CHAP.
absolutely rigid and the other movable ; much more frequently
both the bones are movable, but in different degrees. The muscle
or muscles attached to the two bones exert in contraction an
equal traction upon the two points of insertion and tend to dis-
place the two bones equally, but since the resistances opposed to
the displacement of the two bones differ, it follows that they are
unequally displaced. The distinction of fixed and movable in-
sertions of a muscle really has only a very relative value. As a
rule, however, one of the muscular insertions is less displaced
than the other, generally that which is nearer the axis of the
trunk, or the root of the limb.
FIG. 65. — A, Flexor movements of forearm for contraction of anterior brachial, which causes
backward rotation of arm in scapulo-humeral articulation. (O. Fischer.) B, Extensor move-
ments of forearm produced by triceps, and associated with forward rotation of arm in
scapulo-humeral articulation. (O. Fischer.) The two diajn'ams represent an experiment made
on a mechanical model.
To demonstrate the mobility of the points of insertion of the
muscle, Fischer (1895) employed a wooden model to represent
the humerus and ulna articulating together, flexed by contrac-
tion of the anterior brachial muscles, and extended by the con-
traction of the triceps. He found that the movement of flexion
is associated with the backward displacement of the humerus, and
the movement of extension with its forward displacement (Fig.
65, A, B).
The relation between the movements of the shoulder and of
the elbow joints which occur in consequence of the contraction
of the flexor or extensor muscles of the elbow varies when the
mass of the limb is increased. If, for instance, a weight is held
in the hand, and the elbow is flexed, the movement at the shoulder
is increased.
II
MECHANICS OF LOCOMOTOE APPAEATUS 105
These statements refer not merely to the flexor and extensor
muscles of the forearm, but have a general value. When the
knee is bent, not only does the leg move backward, but the thigh
bends simultaneously forward. Generally speaking, it may be
stated that a uni-articular muscle produces a movement in the
neighbouring articulation in the opposite direction to that which
occurs in the articulation lying between its points of insertion.
The whole of the force on the muscles
is not utilised in the movements of the ^
skeleton. This occurs only in the case
when the insertion of the muscles is
approximately at right angles to the bone,
as in the masseters which are able to em-
ploy their full strength in bringing the
jaws together. But the great majority
of the muscles are inserted more or less
obliquely, the direction of their fibres
forming a more or less acute angle with
the principal axis of the bone. In all
these cases a great part of the traction
force of the muscle is lost in the move-
ment. This disadvantage is frequently
diminished by the fact that many bones
have prominences at the point of attach-
ment of the muscles over which the tendons
of the muscles pass as over a pulley, and
become attached to the bone at a favour-
able angle.
In every case, whatever the form and
size of the angle of insertion of a muscle
upon the bone, it is possible by resolving
the total traction force into its components,
according to the law of the parallelogram
of forces, to estimate how much is utilised
T i . , , • , • Fio. t>6. — Diagram of the resolu-
m displacing the moving bone, Supposing tion ofi muscular force into
the other bone to be rigid.
Let it be supposed that AC and AB in
Fig. 66 represent the long axes of two bones, which are movable
round the axis A perpendicular to the plane of the figure ; that
MM' are the points of insertion of a muscle, M being fixed, M'
movable ; lastly, that the line M'D represents the total traction
force of which the muscle is capable. If we resolve the line M'D
into its two components M'E and M'F, which are vertical to each
other, then M'E represents the force utilised by the muscle in
moving the joint A, called by mechanicians the moment of force,
while M'F is the amount of force that is spent in pressing the two
articular surfaces at A against one another, so as to render the
its components. Explanation
in text.
106
PHYSIOLOGY
CHAP.
articulation more solid. The more obtuse the angle BAG formed
by the two bones, the smaller will be the components M'E, i.e. the
force utilised in the movement. The smaller this angle becomes,
the greater will be the proportion of the force employed in the
movement.
Since movable bones may be regarded as levers, the laws
which govern the action of
levers can be applied to them.
When the object is to attain
considerable speed rather than
have great force, the force is
applied to the shorter arm of
the lever ; when, on the con-
trary, a high resistance has to
be overcome, and less speed
of movement is required, the
force is applied to the longer
arm. In the animal body the
arm of the lever to which the
force is applied is shorter than
that which causes resistance,
i.e. the majority of the muscles
are inserted nearer the articu-
lations than is the centre of
gravity of the movable part.
This arrangement is advan-
tageous for the speed of the
movement,butdisadvantageous
owing to loss of force. The
loss is, however, compensated
by the fact that a less amount
of muscular shortening is re-
quired to effect a given range
of movement (Fig. 67).
It is important to note that
during movement the length
of the arm to which the force
applied, and that which
FIG. C7. — Diagram showing the various degrees of
muscular shortening required for a given move-
ment, according as the lever arm varies for
Eower and for the load. (Luciani.) When the
iver AC rotating on the axis A reaches AC", the
muscle MM only shortens slightly (Mm'), because
the lever arm AM i.s shorter than that of the
load MC ; the muscle MM', on the contrary, has
to shorten much more (to Mm") to execute the
same movement, because the arm AM' is much
longer than that of the load M'l '.
IS
carries the weight, often vary
in proportion with the range of
the movement, so that the load diminishes during work. When,
for instance, the body is raised from the bent knee, this movement
is accompanied by the unloading of the muscles which actively
extend the knee. In this position the arm that carries the load
is represented by the horizontal distance of the axis of the knee-
joint from the line of gravity of the body, i.e. from the perpen-
dicular taken from its centre of gravity. During the rise this
ii MECHANICS OF LOCOMOTOK APPARATUS 107
distance becomes gradually less, and iu the erect posture is almost
negligible. On the other hand, the working line of the quadriceps
muscle which extends the knee remains at approximately the same
distance from the axis of the knee-joint during the movement.
III. Leaving the study of the various positions that may be
assumed and the different movements that may be performed
by each part of the skeleton, we must here confine ourselves to
studying the different postures and movements of the body as a
whole in progression.
In both standing and walking the position and the displace-
ment of the centre of gravity and of the line of action of gravity
of the whole body are of great importance.
Every part of the body gravitates according to the vertical
line that falls from it to the earth. This infinite number of
perpendiculars which only meet at the centre of the earth, and
niay therefore be regarded as parallels, may be replaced by one
single perpendicular line representing the sum of the component
forces ; this is known as the line of gravity. Whatever position
is assumed by the body, so long as it preserves the same form,
the lines of gravity corresponding with each posture intersect
at the same point which is known as the centre of gravity.
In all bodies which are not geometrical in form and consist
of a heterogeneous mass, the centre of gravity can only be deter-
mined by experiment. This is done by suspending the body by a
cord successively in two different positions ; the directions of the
cord prolonged through the body give two lines of gravity, and
the point at which they intersect is the centre of gravity. The
exact determination of the centre of gravity of the human body
is much more difficult, since it is not a rigid body, and undergoes
changes of form.
Borelli (1679) and the Webers, starting from the assumption that
in well-formed individuals the line of gravity must lie in the median
sagittal plane, or the plane of symmetry of the body, attempted
merely to ascertain the height of the centre of gravity, that is, its
distance from the sole of the foot and apex of the head, without
defining its position on the transverse vertical plane. For this
purpose they laid a man on his back upon a board supported on
a metal wedge, and placed the whole in equilibrium like the arms
of a balance. The vertical plane perpendicular to the length of
the body through the wedge that supports the board must pass
through the centre of gravity. They found that this plane was
nearer the crown of the head than the sole of the foot. If the
total height of a man be taken as 1000, the centre of gravity
would be found at 570 from the sole and at 430 below the crown.
These observations were controlled by Harless and by Meyer,
who found values that did not vary more than 3 per cent from
those of the earlier observers. Harless found that in woman the
108
PHYSIOLOGY
CHAP.
centre of gravity is placed lower than in man ; in children, on the
contrary, it is higher, owing to the relatively greater or less
development of the pelvis.
In order to ascertain the centre of gravity in the antero-
posterior plane of the body, Meyer placed a naked subject in the
erect and rigid posture, and then made him bend forward on the
front of his feet and his heels as far as possible without falling.
By means of a plumb line he determined the lines of gravity in
the two most extreme postures, and the points of intersection of
Fin. 68. — Normal position. (Braune ami
Fischer.) In this position the centres of
rotation of the principal articulations fall
in the same vertical plain- indicated by the
line.
FIG. 60. — Military position or "stand at
ease." (Braune and Fischer.) In this
position the centres of rotation for the
lower limbs lie behind the vertical line that
passes through the centre of gravity.
these lines in the body represent its centre of gravity in the given
erect and rigid posture.
More recently Braune and Fischer have applied the same
method to the dead body frozen and extended on its back upon a
board. The rigid and invariable form of the body enabled them
to determine exactly the point of intersection of three perpen-
dicular lines of gravity obtained by successively suspending the
body in three different positions.
According to Weber the centre of gravity of the whole body
in the erect position is at about the level of the sacral promontory ;
according to Meyer it lies at about the upper border of the second
sacral vertebra inside the spinal canal ; according to Braune and
Fischer it is considerably farther forward, at the level of the upper
border of the third sacral vertebra.
ii MECHANICS OF LOCOMOTOE APPAEATUS 109
The centre of gravity of the trunk may lie determined on the
dead subject in the same manner after exarticulating all the
limbs. It lies in the plane between the lower extremity of
the sternum or the ensiform cartilage and the tenth dorsal
vertebra, and in a vertical transverse plane that passes somewhat
behind the axes of rotation of the heads of the femurs. We shall
presently see the importance of this fact.
The position of the centre of gravity for the whole body is
important in determining the positions of more or less stable
equilibrium of the body. Braune and Fischer denned the normal
erect posture (Normdl-Stdlung} as that in which the axes of
rotation of the principal articulations fall in the same vertical
transverse plane as the line of gravity (Fig. 68). From this
they distinguish the military or " stand-at-ease " position (Bequeme
Hal tuny} in which the line of gravity falls 4 cm. in front of
FIG. 70. — The base of support and the line of gravity in different postures. At A tin1 base of
support is represented by the area <>''<•'/, and </ is the point through which the line of gravity
passes ("attention attitude"). At B the base of support comprises ulinl, i/ being the point
through which the line of gravity passes ("normal position").
the line of junction of the articular heads of the femurs (Fig. 69).
In the first posture the line of gravity falls near the posterior
margin of the base of support ; in the second it falls considerably
more forward (Fig. 70). Obviously this last posture represents a
more stable condition of equilibrium.
In each different posture assumed by the body resting on the
soles of both feet there is a new displacement of the centre of gravity
(Fig. 71). If the individual carries a weight he is constrained to
modify his position because the system is thrown out of equilibrium,
unless the centre of gravity lies within the common base of
support. If the load is placed on the back he must lean forward,
if the weight is placed in front, backward. If a weight is held up
with the right arm the body inclines to the left ; if with the left
arm, to the right. Heavier weights can be borne on the head, as
then the normal posture of the trunk may be but little changed,
and the line of gravity little displaced, but the centre of gravity
is raised, which renders the equilibrium less stable, though the
base of support is unchanged.
110
PHYSIOLOGY
CHAP.
In order to increase the base of support and to obtain more
stable equilibrium it is only necessary to set the feet further apart
upon the ground. This is often done where the erect posture has
to be long maintained.
From these forms of symmetrical vertical posture we must dis-
tinguish the asymmetrical vertical posture, in which almost the
whole weight of the body falls upon one leg, the other being
slightly flexed and placed in advance. In this posture (Jianchee]
the line of gravity falls through the extended limb which supports
FIG. 71.— Displacement of centre of gravity in postures a, &, c. (Braune and Fischer.)
Centres of gravity shown as black dots on the vertical lines.
the body, and the trunk consequently inclines towards this side.
The different forms of this posture, which is very natural and
instinctive, are determined by the angle formed by the longi-
tudinal axes of the two limbs or by the distance between the
two soles of the feet.
IV. We should next consider briefly the mechanism of
equilibration in the different postures of the human body, but
must here confine ourselves to the horizontal posture, the sitting
posture, and the common erect attitudes.
The horizontal posture is the easiest to maintain because
it unites as completely as possible the two conditions of stable
equilibrium, i.e. an extensive base of support, and the maximum
approximation of the centre of gravity to it. As muscular con-
ii MECHANICS OF LOCOMOTOE APPAEATUS 111
tractions are not necessary for maintaining equilibrium in lying
down, that is therefore the position of rest and sleep. We may
distinguish between the sternal, sterno-costal, lateral and dorsal
postures. This last is almost confined to man, as in no other
vertebrate is the back sufficiently flat to support the weight of the
body conveniently.
In the sitting posture, if the trunk is leaning against the back
of the seat, all the muscles are in repose, except the elevators of
the head which keep it in the vertical position. In fact, in
sleeping while seated the head drops forward towards the chest,
which shows that the centre of gravity for the head is placed in
front of the occipito-atlantoid articulation.
When seated on a stool with no support for the back, the base
of support is represented by the line that connects the outer
margins of the sciatic tuberosities and of the feet which rest on
the ground. In order to maintain the centre of gravity of the
head and trunk within this base, it is necessary to obtain the
antero-posterior balance by the alternate activity of the dorsal,
the lumbar, and the psoas-iliac muscles.
In the erect posture, with the two feet set square, the centre
of gravity of the body is brought much higher from the base of
support, and this base is much smaller; it would therefore be
natural to assume that a much greater muscular force would be
necessary to preserve equilibrium. Meyer, on the contrary,
demonstrated that in the most comfortable erect posture, the
muscular activity necessary to preserve equilibrium is small, as this
is due principally to the tension of the ligaments, especially the
ileo-femoral ligaments.
As its articulations are mainly synchondroses, the vertebral
column may be regarded as an elastic bar, capable of supporting
the entire weight of the head, trunk, and upper limbs. It has
various curvatures ; it is convex forwards in the cervical and
lumbar regions, and concave in the thoracic and sacral regions
(Fig. 72). It is wholly immobile in the sacral region owing to the
fusion of the vertebrae, but little movable and flexible in the
lumbar region, much more mobile and flexible in the dorsal
part, and in the cervical region it is remarkably flexible in all
directions. The neck muscles fix the head, and therefore make
the cervical spine relatively rigid.
The line of gravity of the trunk and head in the easy (or
military) position shown in Fig. 69 falls behind the line of
junction of the ileo-femoral articulations. The trunk would
primarily fall back, but for the resistance, as Meyer showed, of the
strong ligament which runs from the anterior inferior iliac spine
to the anterior intertrochanter line of the femur ; the balancing
of the trunk on the heads of the femur is chiefly due to the
elastic tension of this ileo-femoral ligament, but this is aided by
112
PHYSIOLOGY
CHAP.
the alternate activity of the psoas-iliac muscles, which tend to
bend the trunk forward, and the dorsal and lumbar muscles, which
tend to incline it backward.
The common line of gravity of the head, trunk, and thighs, also
passes behind the knee-joints; and some arrangement is necessary
when the individual is in the upright
posture to prevent falling backwards
owing to flexion of the knees. This is
provided for by the tension of the ileo-
fernoral ligaments which rotate the
femora inwards, and thus prevents the
slight external rotation which is neces-
sary for the flexion of the knees. The
hip- and knee-joints are thus both fixed
by the weight of the trunk, which
throws the ileo-femoral ligaments into
tension. Owing to this mode of fixation
of the knee-joints, the active interven-
tion of the extensor quadriceps muscle
is not necessary, and indeed the patellar
ligament does not seem to be more tense
in the vertical posture than in other
positions.
The line of gravity of the whole body
falls on the ground in a plane somewhat
anterior to the line between the two
tibio-astragalic articulations, and the
body tends to fall forwards. This is
avoided by the fact that the plane of
flexion in this joint is very oblique with
that of the other side ; the two planes
of flexion form an angle of 60° open to
the front. In order that flexion at
these two joints should be possible, it
is therefore necessary for the two knees
to be moved apart from each other, and
flexed. When flexion of the knees is
prevented, falling forward owing to
flexion of the tibio-astragalic articula-
tions is also prevented. As the fixation
of the hip-joint determines the fixation of the knee, the fixation
of this joint leads to the fixation of the ankle. Here again the
gastrocnemius, soleus, posterior tibial, and posterior peroneal
muscles also take part in maintaining fixation.
The tarsal and metatarsal bones, which constitute the skeleton
of the foot, form an arch which rests on the ground by the
tuberosity of the heel, and the heads of the first and fifth meta-
Fio. 72. — Curve normally presented
by the anterior median profile of
the vertebral column in the
military posture. (G. H. Meyer.)
it, tuberculum anterius of atlas ;
b, lower border of 6th cervical
vertebra ; c, upper border of 9th
dorsal vertebra ; /, lower border
of 2nd lumbar vertebra ; p, pro-
montorium ; s, symphysis ossium
pubis ; d, angle of 3rd sacral
vertebra ; e, coccyx.
ii MECHANICS OF LOCOMOTOE APPARATUS 113
tarsal bones. Owing to the strength of the plantar ligaments
the arch of the foot can carry heavy weights without giving way.
Flat foot, owing to abnormal relaxation of these ligaments, is un-
favourable to the maintenance of equilibrium in the erect posture
and in walking.
Owing to the formation of the skeleton and the arrangement
of its ligaments, the erect posture can therefore be maintained
with a comparatively slight expenditure of muscular energy.
But when it is necessary to remain standing for a long time,
an asymmetrical posture is generally preferred, in which the
main part of the weight of the body is thrown on one leg, while
the other is held in a forward and semi-flexed position.
Vierordt, by an extremely simple graphic method, registered
the oscillations of the head in different positions, with the object
of determining the most natural posture, i.e. that which induces
the least fatigue and provides the greatest stability of the body.
The method consisted in attaching a pen to the head by a suitable
cap, which traced on a paper fixed horizontally from above the
oscillations of the principal axis of the body in different postures,
each being maintained for three minutes. He found that the
antero-posterior and lateral oscillations are considerably greater
in the symmetrical military posture than when the weight was
thrown upon one leg (asymmetrical). The latter posture is
accordingly the most natural, and preference is given to it in
sculpture and painting.
According to Vierordt the advantages of the asymmetrical
posture are as follows :—
(a) Greater rigidity of the hip- and knee-joints, due to almost
the whole weight of the body falling on the limb which serves
as support ; this produces increased tension of the ligaments,
particularly of the ileo-femoral.
(&) The calf muscles of only one side are active, and less
work is thrown upon these than in the symmetrical posture.
(c) The advanced limb, which does not bear the weight of the
body, exerts a slight pressure on the ground, so that when the
quadriceps extensor of the knee comes actively into play to hinder
the body from falling forwards, it works under favourable con-
ditions. In the symmetrical posture, on the contrary, the calf
muscles on both sides work under a heavy load to attain the
same end.
(d) The appreciation of pressure by the sole of the advanced
limb, and the muscle sense generally, are under the most advan-
tageous conditions in the asymmetrical posture, so that oscillations
of the centre of gravity are more readily perceived, and promptly
compensated by muscular reaction.
And, as in the asymmetrical attitude, the muscles of one
limb only become fatigued, it is possible to remain longer
VOL. Ill I
114
PHYSIOLOGY
CHAP.
standing, by throwing the weight of the body alternately on the
two feet.
V. In locomotion there is a great and more or less rapid dis-
placement of the centre of gravity of the body and its base of
support. The movements performed by man in different forms
of locomotion are extremely complicated. But the principles of
mechanics by which we have explained the maintenance of
equilibration help to solve the fundamental problems of human
locomotion.
The ordinary forms of locomotion are walking and runniny.
In both the body is thrown
forward by the rhythmic and
alternate muscular contractions,
specially by the muscles of the
lower limbs. In walking the
body never leaves the ground,
but in running the whole body
is momentarily in the air.
According to the description
of the Webers the lower limbs
are alternately active in walk-
ing ; while the one which is
applied to the ground sustains
the entire weight of the body
and throws the centre of gravity
forward, the other swings pass-
ively.
Each step begins with plac-
ment of the step. (Kick.) a, passive right ing the active limb with its Sole
leg winch touches ground with big toe only; on the ground, the foot and
db, left foot with whole sole resting on ,~
ground; c, centre of rotation for hip-joint; knee being SOlliewhat flexed,
IKY/, rectangular triangle, in which the passive -\ , i -i , p , i 1,1
limb forms the hypotenuse, the ground and ailQ 1116 Weigilb 01 DOCly
catheter' accor(lin8 to the falls on the sole, while the
passive limb lies behind with
its great toe on the ground. At this stage the centres of the
femoral heads and the extremes of the two limbs form a rect-
angular triangle with the ground, two sides being formed by the
active limb and the ground, and the hypotenuse by the passive
limb (Fig. 73).
In the next stage of the step, the knee of the active limb
is extended and the heel raised, throwing the centre of gravity
forward and slightly raising it, while at the same time the passive
leg is lifted from the ground and swung forwards till it once
more touches the ground and takes the weight of the body.
According to the Webers each step in walking may be con-
sidered as a movement of falling forward, which is arrested by
advancing the passive limb and throwing the weight upon it.
S a!
FIG. 73. — Position of lower limbs at commence
II
MECHANICS OF LOCOMOTOE APPARATUS 115
In order to swing forward without hitting the ground the
passive lirub must shorten slightly. But according to the Webers'
theory this is not due to contraction of the flexors of the thigh
or knee, for the lower limb may be regarded as a compound
pendulum which in oscillating becomes slightly flexed at its
articulations. Eecent investigation has, however, modified much
in this theory.
It is not correct to say that the limb lifted from the ground
and swinging forwards is totally passive. Duchenne, by his
clinical observations, demonstrated the
necessity in regular walking of the
active intervention of the flexors of the
thigh, the tensor fasciae, the psoas-iliac
and the sartorius muscles to shorten
the limb and avoid contact with the
ground during the swing. Marey, too,
showed that the swing of this limb
could not be regarded as passive, since
it consists in a progressively acceler-
ated movement, and must therefore be
associated with, and partly dependent
on, muscular force.
In order to obtain a more exact idea
of the complex movements of walking,
the way the feet are lifted and set
down, and the position assumed by
the limbs at their principal articula-
tions in each phase of the step, graphic
and chronophotographic methods must
hp rp^nrrprl in FIG. 74.— Pedestrian in exploring si s
which record the pressure applied
to the ground upon a portable
Marey and Carlet were the first who apparatus. (Marey.)
applied the graphic method to the study
of the complex movements of walking and running. Of the different
instruments which Marey invented, the most important are the shoes, which
register the pressure applied to the ground by the individual who walks or
runs. The sole of these shoes contains an air-chamber communicating by a
tube with a recording tambour, which writes upon a portable revolving
cylinder, held in the hand of the individual who performs the experiment
(Fig. 74). The air-chamber lies in the front part of the sole, near the end
of the metatarsus. Accordingly it only registers the pressure exerted upon
the anterior part of the foot (Fig. 75). Carlet obtained better tracings by em-
ploying soles with two intercommunicating air-chambers placed one lu-ar
the heel, the other near the front of the metatarsus.
Along with these tracings of the pressure exerted by the feet while
resting on the ground, Marey and Carlet registered the vertical oscillations
of the head, or the horizontal oscillations of the pelvis (Figs. 75, 79), by
means of special tambours.
The chronophotographic method which Marey applied to walking
consists in recording on one fixed plate the successive images of a person
walking. The photographic apparatus has a lens, and a man is made to
116
PHYSIOLOGY
CHAP.
walk past a black ground with a white net on his back which is vividly
illuminated by direct sunlight. While he walks a rotating apparatus lets
light into the camera obscura at regular intervals. At each instantaneous
exposure an image of the subject in different postures is thrown upon the
successive parts of the plate (Figs. 82 and 84). In order to obtain more
images at each cycle, and at the same time to avoid the confusion resulting
from their superposition, Marey invented the ingenious method of partial
Km. 7-j. — Curve of walking. (Marry.) />, movements of right foot ; 5, of left foot ;
II, vertical oscillations.
which consists in suppressing the images of the left side of
the body, photographing only the right half of the walker. For this
purpose the left half is clothed in black, the right in white (Fig. 76).
The figures of each step can similarly be multiplied in walking or run-
ning by increased simplification of the images. For this the subject is
clothed entirely in black, six brilliant metal buttons being placed on the
head and over the articulations of the shoulder, elbow, thigh, knee, and foot, as
well as five shining bands over the bone of the arm, forearm, thigh, leg,
and edge of the foot (Fig. 77). By photographing the subject as he walks
forward strongly illuminated by the sun, the chronophotogram is obtained,
as shown in Fig. 78, where, for the sake of simplification, the tracing of the
Fiii. 76.— Photographs of right half of body of a subject walking slowly iiasl the camera. (Marey.)
head is omitted, since it shows only vertical oscillations which are perfectly
comparable at every step with those of the dots on the shoulder and thigh,
as shown on the figure.
A later improvement on Marey's method was introduced by Braune and
Fischer, who substituted for the dots and metal bands on the black coat of
the subject, upright Geissler's tubes, connected with the conducting wires
of a circuit which included a big Ruhmkorf induction apparatus. The
circuit was interrupted at equal intervals, which lasted O0383 parts of a
second. By photographing the subject as he wralked not only along a plane
parallel with the sensitive plate but also along other planes, Fischer was
II
MECHANICS OF LOCOMOTOK APPARATUS 117
able to construct a curve of the movements of various joints and of the head,
as also of the, movements of the trunk, etc.
Fig. 80 is a diagram of the cycle of walking constructed by Zimmerman
from tlie dmmophotographs of Fischer.
The tracing (Fig. 79) obtained by Carlet with his exploring
shoes shows that in the usual mode of walking the heel is first
applied to the ground, then the whole sole of the foot, and lastly
the ball of the toes only ; that the time during which both feet
are on the ground is less than half the
period that each alone rests on it ; that
the time of the rise and swing of one
leg is always shorter than that of the
opposite limb. Carlet demonstrated by
the same method that the pressure exer-
cised by the foot upon the ground during
a step is not equal to the weight of the
body, but that in the last stage of the
step an additional pressure dependent
on the muscular forces, which raises the
body and propels it forward, is added.
According to Carlet the additional incre-
ment of pressure varies with the length
of the steps and never exceeds 20 kgrms.
The length of the step depends on
the length of the lower limbs and the
degree in which the knee of the limb
which bears the weight of the body at
the commencement of the step is flexed.
Fig. 73, which shows diagrammatically
the position of the lower limbs at the
commencement of the step, makes it
plain that the length of step can only
increase when the length of the hypo-
tenuse (i.e. the length of the extended
limb) is increased, or when the flexion
of the knee of the limb on which the weight of the body
falls is increased. People who have long legs and long feet
naturally take longer steps than short people ; and if they walk
together the latter are obliged to quicken their step by a voluntary
effort ; this is done by increasing the flexion of the knee and
dropping the centre of gravity. If the knee is kept rigid and
extended, only very short steps are possible, and a greater expendi-
ture of energy than usual is required.
It is also possible to vary the rate of the step, which depends
on the duration of the application of one or both feet to the ground,
that is, on the forward swing of the inactive limb. The duration of
the double application depends on the will ; the more hurried the
ing. ChronophotograpMc method.
(Marey.)
118
PHYSIOLOGY
CHAP.
gait, the shorter it becomes, and according to the Webers in very
rapid walking its duration is reduced to zero, i.e. one leg is raised
as soon as the other touches the ground. This, however, is contra-
dicted by Carlet, who found a brief period in which both feet were
on the ground, even in the most rapid gait. The rate of swing
of the relatively passive limb depends on the stature or the length
of limb. The shorter the limb, the more rapid the swing.
The speed of walking depends upon the length and duration
of the steps, i.e. the distance traversed in the time unit. Numerous
FIG. 78. — Chronophotograph of walking ; shows the successive positions taken up by the joints
"and bones of the limbs in the step. (Marey.)
experiments of the "Webers show that as an individual increases
the length of his steps their duration diminishes, so that when
walking at full speed the duration of the steps is minimal and their
length maximal. This can be verified from the figures given by
the Webers in the following table :—
Duration of Step
in Seconds.
Length of Step
in Millimetres.
Speed of Walking
in Metres per Sec.
0-335
851
2-397
0-417
804
1-928
0-480
790
1-646
0-562
724
1-288
0-604
668
1-106
0-668
629
0-942
0-846
530
0-627
0-966
448
0-464
1-050
398
0-379
This law of the inverse ratio between length and duration of
steps only holds, according to Marey, up to a certain point. When
II
MECHANICS OF LOCOMOTOE APPARATUS 119
the number of steps exceeds 150 per minute, i.e. when the duration
of the step becomes less than 0'4 second, the speed of walking
does not increase because the length of step diminishes.
The force of walking depends on the extensor muscles of the
thigh, leg, and foot.
Fig. 80 gives an exact idea of the position of the principal
articulations not only of the lower limbs, but also of the upper
limbs and the head at the different moments of the step cycle.
123 4 567 g- 91011
T23 4 567
Fi<:. 79. — Tracings of the pressure applied to the ground in walking. (Carlet.) I'd, right foot;
P*. left foot; Or, vertical oscillations; On, horizontal oscillations. 1, 2, 3 = period of double
application; 3, 4, 5 = period of single application; l-7 = period of application of left foot;
5-11 = period of application of right lout ; 1-3 and 5-7 = application of heel of left or right foot ;
4-5 and 8-'.i = application of point of left or liuht foot.
The cycle begins at the instant in which the left leg is raised
from the ground and swings forward, while the heel of the right
leg rests upon the ground.
Each step is divided into 10 successive phases of equal duration,
and at every 10th phase the right leg is in the position originally
occupied by the left, and vice versa. From the 1st to the 5th
phase, which include the first half of the step, the left knee
becomes flexed, while the right becomes extended, so that the thigh
and shoulder joints (represented by the junctions of the black and
red lines) and the vertex of the head (represented by the big dots
marked on the upper part of the figure) are somewhat raised.
From the 6th to the 10th phase, which include the second half of
i 1
120
PHYSIOLOGY
CHAP.
the step, the left leg is extended forward till the heel touches the
o
~~.
to
5
30
a
o
S
00
ground, while the right leg first rests upon the ground with the
ii MECHANICS OF LOCOMOTOE APPARATUS 121
whole sole of the foot, but later, as the heel rises, on the point of the
foot only. In the first half of the step — owing to the extension
of the right knee — there is an upward vertical oscillation of the
hip, shoulder, and head ;• while in the second half of the step there
is a downward movement owing to forward flexion of the right
ankle, and parti}7 also of the knee on the same side. So that at
each step there is a douhle vertical oscillation of the hip, shoulder,
and head, as clearly shown by the figure. According to the Webers
these vertical oscillations attain a height of 32 mm., according to
Carlet of 37 mm., in persons of average height, during fairly rapid
walking; they increase in proportion to the length of the steps.
Besides these vertical oscillations, the top of the head and the
shoulders and hips show lateral horizontal oscillations during
walking, which are very apparent on looking down from a height,
for instance from a window, upon a person walking in the street.
While the vertical oscillations coincide with the length of a step,
the horizontal oscillations correspond to the double steps or a whole
step cycle. These lateral horizontal oscillations reach their maximum
at the same moment as the vertical oscillations. In the diagram
of Fitj. 80 the maximal lateral oscillation therefore falls to the
O
right at the 5th phase, and the maximum of lateral oscillation to
the left at the 15th phase. The further apart the limbs are in
walking, the more pronounced are these lateral oscillations, which
evidently depend upon the degree of abduction at which the feet
are planted upon the ground.
The oscillations of the shoulders and hips round a vertical axis
should also be noted ; these accompany the lateral oscillations of
the trunk. At each step the leg that is moving forward is accom-
panied by a forward movement of the hips and a backward move-
ment of the shoulders, i.e. a slight twist of the trunk round a
vertical axis. This torsion may be so exaggerated as to become
very apparent, but it is present to a slight extent even in normal
walking, especially in women with a large pelvis. The forward
movement of the hips is also due to the swing forward of the
lower limb of the corresponding side and the active contraction of
the lumbar muscles ; the backward inclination of the shoulders is
produced by the swing forward of the upper limb of the opposite
side, which, according to Duchenne, is not purely passive, as it
depends partly on contraction of the deltoid muscle. Fig. 80 shows
plainly that while the left leg swings forwards, the right arm
becomes more and more flexed at the elbow, and is raised and
advanced. This torsion of the trunk and active oscillation of the
upper limbs, which balance the body, increase in rapid walking.
These simultaneous and opposite movements of the upper and
lower limbs in the ordinary gait of man correspond with the
alternate movement of the four limbs in the ordinary gait of the
quadrupeds.
122 PHYSIOLOGY CHAP.
Lastly, it should be noted that the torsion of the trunk is
always accompanied (particularly in hurried walking and climbing)
by a rhythmical forward movement of the trunk and head at each
stride. This movement, which overcomes the resistance of the air
and economises the power of the limbs by throwing the centre of
gravity forward, is probably the effect of the activity of various
muscles, especially of the ilio-psoas.
VI. After this account of the complex mechanism of walking
there is little to add in regard to running. As we have already
pointed out, the two feet are never on the ground at the same
moment in running, and one foot never comes in contact with the
ground till the other has been raised from it ; the entire body is
consequently suspended for a moment in the air. This is shown
by the tracing taken with the exploring shoes (Fig. 81). It can
also be seen with instantaneous photographs upon a fixed plate,
FIG. 81. — Curves nf luiiniim, traced with m-onliim shoes. (Matey.) D, movements of rijjlit font :
S, movements of left tout : n. \n t iciil oscillations. The ai'plieation of the foot to the ground
lie-ins at. the moment at which tin- cuive tises; its removal, at. the moment at wliich tin-
curve drops.
when the exposures occur at a rhythm corresponding with that of
the two phases of the step in running (Fig. 82).
This essential difference between walking and running depends
upon the fact that in running the extension of the limb upon the
ground and of forward displacement of the body is more marked,
so that the body is thrown forward and raised from the ground.
During the moment while the body is unsupported in the air the
two legs swing forward. The leg which gives the forward impulse
is a little behind during the swing, and a little forward while the
other leg touches the ground.
The contact of each foot on the ground is shorter in running
than in walking, and its duration is inversely proportional to the
force with which each foot is applied to the ground ; this increases
with the rate of running. The frequency of contact increases
with the pace, but only within certain limits, beyond which the
space covered in a certain time depends more on the length of the
steps than on their number.
The absolute duration of the period in which neither foot is on
the ground varies very little with the variations of the speed of
running ; but its relative duration increases considerably, since,
ii MECHANICS OF LOCOMOTOH APPARATUS 123
as was said above, the duration of the contact diminishes with
increased speed.
In order to form a true conception of the mechanism of
running it is very instructive to ascertain the exact moment at
which the vertical oscillations of the body reach their maximum
upward excursion. The Webers held that this occurred as the
body is projected upward and forward by the force of the impulse
given by the rapid extension of the limb in contact with the
ground. Marey's tracings show, on the contrary, that the body
attains the maximum of its vertical ascents as one foot conies to
FIG. 82.— Instantaneous photograph of running— on a fixed plate. (Marey.)
the ground. As shown by curve 0, Fig. 81, the head begins to
rise at the moment at which the foot touches the ground, and
reaches its maximum height midway through the period of
contact, after which it descends and reaches its minimum at the
moment when the foot leaves the ground, and before the other
foot comes into contact with it, i.e. during the phase of suspension.
This proves that the suspension is due essentially not to the
sudden extension of the leg but to its subsequent flexion, which
suddenly withdraws it from the ground after giving the upward
and forward thrust to the body.
Both the leg on the ground and also the swinging leg are
much more active in running than in walking. The muscles of
the upper limbs also contribute to the forward thrust of the body,
since they oscillate alternately with the homologous lower limbs.
The torsion of the trunk round a vertical axis and inclination
124 PHYSIOLOGY CHAP.
of the shoulders are less marked in running than in walking. On
the other hand the inclination of the trunk forward in the first
period of the contact, and backward in the second half, is much
more pronounced in running.
The speed of running, according to the statement of the
Webers, may exceed 4'5 m. per second ; anything beyond these
limits can only be kept up for a short distance.
Galloping differs from walking and running, in which there is
a regular alternation of the movements of the limbs on the two
sides, which are placed on the ground at regular intervals.
Galloping deserves a short mention, although it is not a normal
form of locomotion in man. According as the gallop to the
right or to the left is imitated, the right or left foot is put forward
at each step, like a galloping horse. In Fig. 83, which represents
Fio. 83. — Tracing of galloping to the right. (After Marey.) D, movements of right foot;
N, of left foot ; 0, vertical oscillations.
a tracing obtained by Marey with recording shoes, four phases can
be distinguished in the gallop. The left foot, the more posterior,
firsb touches the ground with a firm and prolonged pressure ;
while the left foot is still on the ground the right foot is placed in
a more advanced position (double contact), but with less and
shorter pressure ; the second contact is at once followed by
elevation of the left foot (simple contact) ; and finally conies the
rise of the right foot also (suspension), which lasts a perceptible time
before the tap of the left foot begins the second cycle. Line 0 of
the figure shows that the two taps are followed by two slight
elevations of the head, followed in turn by two depressions, most
of which coincide with the phase in which the whole body is
unsupported in the air.
Jumping consists essentially in the rapid and energetic
extension of one or both lower limbs, preceded by a pronounced
flexion, by which means the body is thrown upward and forward.
The mechanism of jumping varies considerably according to its
purpose.
Chronophotographs on a fixed plate of the successive positions
of an individual who is jumping over a hedge or ditch (Fig. 84)
show that during the spring and the upward and forward thrust
ii MECHANICS OF LOCOMOTOK APPAEATUS 125
of the body, the movement is much more rapid than in coming
down again. While rising, the arms are pushed forward in order
to raise the centre of gravity and increase the impulse in the
direction of the leap ; during the descent, on the contrary, they
are thrown back to lessen the momentum of the body at the
moment at which it touches the ground. As soon as the feet
come in contact with the ground the knees are flexed to lessen
the counter-blow and the shock.
In order to understand the essential features of the different
gaits which we have been discussing the diagram suggested by
Marey is useful. In this the duration of the contacts of the right
foot is shown by white lines, of the left foot by shaded lines, the
duration of the elevation of either limb in the air by the iuter-
FIG. 84.— Instantaneous photographs of a long jump — on fixed plate. (Mai^y.)
veiling black area. It is a kind of simplified notation, less
complete than that of the graphic method because it does not
indicate the pressure exercised by the foot upon the ground and
its variations ; but it is much clearer and shows at a glance the
fundamental difference between the different gaits (Figs. 85, 86).
This form of notation is almost indispensable in differentiating the
various gaits of quadrupeds.
VII. Swimming differs from terrestrial locomotion inasmuch as
the body does not rest on the ground, but is immersed in water,
which is a fluid medium.
The body floating in water may be compared to a body
resting upon a supporting plane, formed by the buoyancy of the
fluid. This is due to a great number of parallel forces which
act vertically from below upward on the lower surface of the
swimming body. The resultant of these forces is called the centre
of buoyancy, which corresponds to the centre of gravity of the
liquid mass displaced. The floating body may thus be regarded as
126
PHYSIOLOGY
CHAP.
suspended by its centre of buoyancy, and to be in equilibrium it is
necessary that the centre of gravity and the centre of buoyancy
shall be on the same vertical plane. And for the equilibrium to
be stable the centre of gravity of the floating body must be below
the centre of buoyancy. Ships are all constructed on this
Fio. S5.— Diagram of four different gaits, from man. (After Marey.) 1, walking on Hat ground ;
2, walking uphill and upstairs ; 3, running ; 4, fast running.
principle, i.e. so that their centre of gravity shall be as low as
possible in comparison with the centre of buoyancy. The same
principle has recently been applied to dirigible airships and
aeroplanes.
On an average the human body as a whole is heavier than fresh
water (I/O 10), but its gravity differs little from, and is even some-
what less than, that of salt water. While lying on his back, so
Fio. 86.— Diagram of galloping and jumping. (Marey.) 1, galloping to the left ; 2, to the right ;
3, series of rhythmical jumps on both feet ; hops on right foot alone.
that only his mouth and nose are above the water, an adult man
(especially if very fat) can easily float on the sea, if he keeps all
his muscles relaxed. Thin people, however, whose average specific
gravity is rather higher than that of salt water, are unable to
float in the supine position without the help of slight impulsive
movements of the feet, produced by rhythmical extension of the
legs. In order to move in this position it is necessary to supple-
ii MECHANICS OF LOCOMOTOK APPARATUS 127
ment the movements of the legs by slight rowing movements with
the arms.
Swimming with the abdomen downwards is more difficult,
either because the centre of gravity is above the centre of dis-
placement or because, as the head and neck are out of water, the
weight of the body is consequently greater than that of the water
displaced.
The mechanism of swimming consists essentially in exercising
pressure upon the water rhythmically from above downwards, and
from before backwards with the surface of the hands and feet, so
as to cause a reaction of the water displaced, which is able to raise
the body, prevent it from sinking, and impel it forward in the
required direction.
The details of the mechanism of swimming have been little
studied since graphic methods cannot be applied, and chrono-
photography is difficult. Moreover, swimming is not natural to
man, but is an art which he learns and perfects by practice.
Accordingly there is no fixed and constant mode of swimming,
and the movements of the upper and lower limbs adopted by
different swimmers are not exactly alike. Generally speaking,
there is an initial thrust forward on the surface of the water by a
rapid extension and adduction of the legs, on which the water is
displaced backwards and toward the bottom by the feet, producing
a reaction which raises the body of the swimmer and jerks it
forward. This movement of the lower limbs is accompanied with
a forward thrust of the arms, which are brought together in front.
The arms are then moved outwards, backwards, and slightly
downwards, this being perhaps more efficacious in swimming
than the initial movement of the lower limbs. This movement
is associated with retraction and abduction of the legs, which
completes the natatory cycle.
If the swimming movements are too strong and rapid, they
are fatiguing and of little use. Both hands and feet, which act as
the blades of an oar, press on the water with the maximum available
surface, and return to the starting position with a slower move-
ment, and at the same time present the smallest possible surface
to the water.
BIBLIOGRAPHY
BORELIJ. De motu animalium, etc. Rome, 1680.
ED. and W. WEBER. Mechanik der menschlichen Gehwerkzeuge. Guttingen, 1836.
DUCHENNK.. Phys. des mouvements, 1867.
CARLET. fitude sur la locomotion humaiiie, 1872.
MAREY. La machine animale, 1879.
G. H. MEYER. Die Statik und Mechanik des menschlichen Knochengeriistes, 1873.
PETTIGREW. La locomotion chez les animaux, 1874.
A. FICK. Hermann's Handbuch der Physiol., I., 1879.
W. BRAUNE and 0. FISCHER. Abhandlungen der rnath.-phys. Klasse der konig.
sachs. Gesellsch. der Wissenschat'ten, 1885-1904.
128 PHYSIOLOGY CHAP, n
MAREY. Developpement de la methode grafique par 1'emploi de la photographic.
Paris, 1885. Le mouvement, 1894.
0. FISCHER. Arch. f. Anat. und PhysioL, Anat. Abt., 1S96.
R. DU BOIS-REYMOND. Ergebnisse d. PhysioL, II., Part ii., 1903. (Contains
many references. ) Spezielle Muskel physiologic oder Bewegungslehre. Berlin,
1903.
Recent English Literature :—
SHERRINGTON. Remarks on the Reflex Mechanism of the Step. Brain, 1910,
xxxiii. 1.
GRAHAM BROWN. The Intrinsic Factors in the Act of Progression in the Mammal.
Proc. Roy. Soc., London, 1911, B. Ixxxiv. 308.
GRAHAM BROWN. Note on the Movements of Progression in Man. Journ. of
PhysioL , 1912, xlv. p. xvii.
GRAHAM BROWN. Dynamic Principles involved in Progression. Brit. Mt>d.
Journ., 1912, ii. 285.
CHAPTER III
PHONATION AND ARTICULATION
CONTENTS. — 1. General observations on the fundamental characters of sounds,
and their formation by different musical instruments. 2. Structure of larynx as
a musical instrument ; functions of laryngeal muscles. 3. Nerves and centres of
phonation. 4. Mechanical conditions for the production of laryngeal sounds ;
function of different parts of the phonatory system. 5. Principal characteristics
of the singing voice. 6. Difficulties and natural imperfections of singing.
7. The vowel system in phonetic language. 8. Theory of physical nature of
vowel tones. 9. System of semivowels or sounding consonants, middle consonants
and mute consonants. 10. Composition of syllables and words. 11. Writing, or
graphic language. Bibliography.
BOTH in animals and man movement may be regarded, broadly
speaking, as the external, conscious or unconscious, manifestation
of the mental state. But it is essential to discriminate between
the movements which betray only instinct and feeling, and the
expressional movements which are the means of intellectual
communication.
These expressional movements and attitudes taken as a
whole constitute natural language, and are of special artistic and
psychological interest. From the physiological point of view
they present no difficulties ; they can be explained on simple
anatomical principles, and by the general laws of mechanics,
which were discussed in the last chapter.
The natural language and the vocal expression of animals
constitute our only objective basis for the construction of a
comparative psychology. This language consists of gestures,
ejaculatory sounds or noises, and physiognomic attitudes, which
are partly imitative (onomatopoeic) and to a far larger extent
instinctive, developed according to the laws of heredity and
atavism. In this language there is nothing conventional ; it is
intelligible to all, without instruction or effort. Without such
a language animals would be unable to herd together, unite in
families and societies, defend themselves from their enemies,
migrate in flocks at certain seasons, etc.
As a general rule it may be said that natural language is
most complete in the more intelligent animals. In different
VOL. Ill 129 K
130 PHYSIOLOGY CHAP.
animals, again, different organs or parts have the task of expression.
In the higher mammals it is the face which by the mobility of
its muscles lie trays most expression, and in many mammals — but
not in man — the ears contribute greatly to expression by their
varied movements ; the nose, lips, and mouth play a considerable
part in physiognomy. In some animals, again, the movements of
the tail and feet are significant. Lastly, the different postures of
the body as a whole play a great part in expression. Painters,
sculptors, actors, all make special studies of the natural language,
both in animals and man. They devote themselves to observing
and minutely analysing postures and deciphering their psycho-
logical significance, in order to reproduce them effectively in
works of art or dramatic representations.
I Hit the chief means by which the animal expresses its feelings,
wants, and passions is the voice, i.e. the inarticulate or scarcely
articulate sounds and noises which are characteristic of different
species.
In deaf mutes the language of gesture attains a high develop-
ment, and is able to fulfil all the needs of social life. But under
normal conditions the mimetic language of man is almost always
accompanied by phonetic language, or speech, and merely serves
to reinforce and elucidate expression.
Voice production is not the direct effect of muscular activity,
but is due to the vibrations produced in a particular apparatus,
the larynx, which is a true musical instrument. Nevertheless, as
it is muscular contraction which produces the degree of tension
in the vocal cords that is essential to the formation of the different
sounds, the study of phonation (speech) is closely connected with
the study of movements.
The formation of words, i.e. articulate speech, is a more
complex process, which is not limited to the larynx, but also
depends on the production of non-musical noises by the current
of expired air as it passes through the pharynx, buccal cavity,
and nasal fossae. Consequently, laryiigeal phonation is not in-
dispensable to conversation, any more than verbal articulation is
necessary to singing. It is possible to whisper without using
the vocal cords, and to sing vocally without words.
I. Since the voice is an acoustic phenomenon with musical
characters, the organ which produces it may be considered as a
musical instrument. In order to understand its function in
speech, it is well to glance briefly at the fundamental principles
of the production and characteristics of tones in general.
All elastic, solid, fluid, or gaseous bodies are capable of
vibrating so as to produce auditory sensations, that is, tones or
noises. A tone, according to Helmholtz, is any auditory sensation
produced by regular rhythmical vibrations ; a noise is a sensation
due to irregular and non-rhythmical vibrations.
in PHONATION AND ARTICULATION 131
Simple sounds or tones are composed of pendular vibrations,
i.e. to-and-fro movements of the vibrating molecules which follow
the same laws of motion as a pendulum. These vibrations only
differ in amplitude and duration : the amplitude is directly pro-
portional to the loudness of the sounds ; the duration is inversely
proportional to the number of vibrations per second, on which the
pitch of the sound depends. The form of the pendular vibrations
is constant and invariable. They can be graphically recorded
by making a tuning-fork trace its vibrations on a revolving
cylinder.
Helmholtz distinguishes "simple tones" or sounds (Ton) from
" compound tones " (.Klang), which are an aggregate of the simple
tones produced by simple, pendular vibrations. While, the form
of vibration in simple tones is always the same, that of compound
tones varies considerably, and depends on. the algebraic sum of the
component tones. The deepest of these tones is called the prime
tone, and the rest are the harmonics, or over-tones. The vibration
frequency of the prime tone to that of the partial tones is in the
ratio of 1 : 2 : 3, etc.
The number of partials which make up a compound tone, and
their relative strength, differs considerably for different musical
instruments, even when the prime tone is the same. This difference
gives rise to the quality (timbre, Klangfarbe] of a note, which
depends on the particular form of the vibration of the tone, due to
the relative number and strength of its harmonic overtones.
A compound tone can be resolved into its partial tones by
means of resonators. All sounding bodies have their own note ;
when made to vibrate, they invariably give out a note of a certain
pitch, which corresponds with a certain frequency of vibration per
second. When the surrounding air transmits to the sounding
body a number of vibrations corresponding to its proper note, it
begins to vibrate in unison. When, on the contrary, the vibration
frequency does not correspond with the frequency of its own note,
it remains at rest, or vibrates very feebly. Given a series of hollow
metal chambers (resonators) tuned to different notes of the musical
scale, it is possible to analyse compound tones into their partials.
When one ear is stopped, and the other is applied to the aperture
of a resonator, each resonator reinforces its own note and cuts
out all the rest (Helmholtz). Konig's manometric flame method,
described in text-books of physics, renders visible the partials
contained in a compound tone.
Another mode of analysing complex sounds is based on the
phonautographic curves traced by means of the thin membranes
used in phonographs with a very light lever, or a small mirror
that reflects a beam of light 011 to a travelling sensitive surface
(Hermann's
Musical instruments can be classified according to the
132 PHYSIOLOGY CHAP.
way in which their sounds are produced ; the principal forms are
stringed instruments, wind instruments, and reed pipes.
In stringed instruments the notes produced by the vibrations
of the strings are enormously reinforced by the resonance boxes.
The pitch varies with the length, tension, density, and thickness
of the stretched string.
The frequency of vibration per second, on which the pitch
depends, is inversely proportional to the length of the string. A
string vibrating over its whole length gives out the deepest note ;
if the length is halved, the frequency of vibration is doubled, and
the pitch is raised an octave ; with a third of its length the
frequency will be three times as great, i.e. a twelfth, and so on.
The frequency of vibration varies directly as the square root
of its stretching force. In order to raise by an octave the pitch
of the note given by the string, the tension would require to be
increased four times.
The frequency of vibration varies inversely as the mass of unit-
lengths of the string. Thicker and heavier strings vibrate less
rapidly and therefore have a deeper tone.
Wind instruments differ from stringed, since the air is here the
resonant body, and the walls of the pipe in which the air vibrates
affect only the timbre, i.e. the number and strength of the partials.
The pitch of the fundamental tone depends on the dimensions of
the pipe, and the strength of the blast of air passing through its
aperture. The narrower and shorter the pipe, the higher is the
pitch ; the greater the tension of the vibrating air molecules, the
more rapid are the vibrations, and the higher the frequency per
second.
Eeed instruments (oboe, clarinet, bassoon) only differ from
other wind instruments by the fact that their aperture is not
fixed and constant, but is formed of two vibrating tongues, which
rhythmically enlarge and reduce the opening by which the air
penetrates into the tube. According to Helruholtz the vibrations
of the tongues are pendular, and they can only give out simple
tones. The compound tones of these instruments depend on the
vibration of the air in the pipes ; the tongues merely regulate the
entrance of the air blast by rhythmically alternating the diameter
of the opening, which breaks up the column of air into a series of
rapid blasts.
Instruments with rigid tongues must be distinguished from
those with soft or membranous tongues, which are represented in
brass instruments (trumpets, horns, etc.) by the lips of the performer.
In these instruments the number of the vibrations is inversely
proportional to the length and diameter of the vibrating membrane,
and directly proportional to its tension and elasticity and to the
strength of the air-current thrown into vibration. The width of
the aperture does not appear to influence the pitch of the note
Ill
PHONATION AND AKTICULATION
133
produced by membranous tongues, but its formation is easier
in proportion as the slit is narrower. The extra tubes which
form the body of these instruments have a great influence on pitch
and timbre ; the tones become deeper as the body is longer, but
never drop an octave as is the case in instruments with rigid lips.
As a musical instrument the larynx has many points of
resemblance with tongued instruments. The formation of laryn-
geal sounds depends on the passage of air through a slit (opening
of the glottis) which is rhythmically altered in width by the
vibration of membranous tongues (the vocal cords) so as to break
up the air blast that passes through it. The wind-pipe is formed
by the bronchi and trachae,
as in brass instruments ; the
sounding -pipe or resonator
by the cavities lying above
the glottis, i.e. the larynx and
pharynx, the mouth and the
nose. On the other hand
the vocal apparatus is dis-
tinguished from all tongued
musical instruments by the
fact that the vocal cords
which represent the tongues
can change at any moment
in length, breadth, diameter,
and tension, even independ-
ently of the pressure of the
air blast which thrOWS them Fl°- S7.— Laryngeal cartilages, seen from behind.
(Henle.) t, thyroid cartilage: Cs, i.'l, its superior
and inferior horns; Pm, Pr, processus muscnlus
and vocalis of arytenoid cartilage ; co, cartilage
of Santorini ; <•;•, cricoid cartilage.
cr
into vibration.
A clear idea of the con-
struction of the larynx is
essential in order to understand the complex mechanism of
phonation.
II. The larynx consists of a cartilaginous skeleton which is only
partially ossified. The laryngeal cartilages are united by fibrous
membranes, ligaments, small articular capsules, and by a series of
small muscles, which constrict or dilate the glottis, stretch or relax
the vocal cords, and regulate the thickness of their vibrating
portions.
The cricoid cartilage is shaped like a signet ring with its narrow
part forward, and its face backward. Its lateral surface articulates
with the inferior cornua of the thyroid cartilage. The two
cartilages can rotate round the horizontal axis of these articular
surfaces, the anterior surface of the thyroid may be displaced
forwards and downwards, or the front part of the cricoid cartilage
may be pushed up towards the thyroid. The triangular bases of
the two arytenoid cartilages articulate at the upper margin of the
K 1
134
PHYSIOLOGY
CHAP.
cricoid plate on both sides of the median line by oval saddle-shaped
joints, which allow of their rotation on their base, and the dis-
placement of the base inward or outward. The stout crico-
arytenoid ligament controls the back to front movement of the
arytenoids. At the summit of the latter comes the articulation of
the two little cartilages of Santorini (Figs. 87, 88, 89).
The thyroid cartilage is attached to the hyoid bone, which lies
above it, by a fibrous membrane, the thyro-hyoid (known in its
middle portion as the ligamentuni thyreo-hyoideum lateralis), and
by the lateral thyro-hyoid ligament, which runs from the superior
cornua of the thyroid to the great cornua of the hyoid. By means
-Cs
Pi — 3
FIG. 88.— (Left.) t, thyroid, and cc, cricoid cartilages, from the side. (Henle.)
FIG. 89. — (Right.) Laryngeal cartilages divided through the median -sagittal plane, and viewed
from within. (Henle.) /, thyroid cartilage ; Cs, its upper horn ; Pi', processus vocalis of
arytenoid ; co, cartilage of Santorini ; er, cricoid cartilage.
of these membranes and ligaments the whole larynx can be drawn
upwards.
Behind the thyro-hyoid membrane is the epiglottis, which is
attached below the thyro-epiglottidean ligament to the median
notch of the thyroid, and projects into the pharyngeal cavity in the
form of a tongue which is folded back in swallowing and forms a
lid for the upper opening of the larynx (Figs. 90, 91, 92).
On both sides of the free portion of the epiglottis the mucous
membrane forms a fold that unites the upper margin of this
cartilage with the cartilages of Sautorini. In the depth of this
aryteiio-epiglottidean fold there is a group of mucous glands and a
nodule known as the cuneiform cartilage, or cartilage of Wrisberg.
The aryteno-epiglottidean fold limits the upper opening of the
larynx ; it is oval in form and is inclined backwards and downwards.
The laryngeal cavity narrows into the glottis or rima glottidis.
Ill
PROBATION AND AKTICULATION
135
Here the mucous membrane forms on each side two thick trans-
verse ridges which extend from the base of the epiglottis backwards
to the vocal processes of the arytenoids. The two upper ridges are
known as the false, and the two lower as the true vocal cords. The
former project less towards the median line of the glottis than the
latter. Between the true and false vocal cords are two recesses,
known as the ventricle of Morgagni (Fig. 94).
The elastic fibres of the submucosa are highly developed in the
fas
tat
J.f-
FIG. 90. —Laryngeal cartilage with fascia, ligaments, and insertions of certain muscles. (Henle.)
Oli, hyoid bone; e, epiglottis; Cs, superior horn of thyroid cartilage; he, hyo-epiglottic
ligament ; Jitl, lateral hyo-thyroid ligament ; tr, cartilage tritica ; tc, thyro-epiglottie cartilage ;
ca, crico - arytenoid cartilage: tas, tai, superior and inferior thyro - arytenoid ligaments;
Cap', Cap", insertions of posterior crico-arytenoid muscle ; Lp, insertion of laryngo-pharyngeal
muscle.
true vocal cords, and form compact bands which run through their
whole length ; they are wedge-shaped in cross-section, and covered
by a layer of non-ciliated pavement epithelium. In the false vocal
cords the elastic connective tissue is much less abundant, and the
mucous membrane that covers it is rich in adenoid tissue, which is
even more plentiful in the laryngeal ventricles and on the posterior-
inferior surface of the epiglottis. The mucous membrane of these
parts soon becomes oedematous from accumulation of lymph in the
lymph-spaces, which may obstruct respiration and cause suffocation
by closure of the glottis.
Owing to their elasticity the true vocal cords extend and con-
tract without falling into folds, and their delicate free edges,
136
PHYSIOLOGY
CHAP.
which are thrown into vibration by the expiratory blast, remain
regular.
The two true vocal cords which extend from their anterior
insertion on the thyroid to the vocal processes of the arytenoids,
into which they are inserted posteriorly, form the pars vocalis of
the glottis, the average length of which in the adult male is 18 '2
mm. according to Miiller, 17'5 mm. according to Harless, in the
female 12'6 mm. according to Miiller, 13-5 mm. according to Harless.
The posterior part of the glottis, which is 7 -8 mm. long, and
FK;. 91.— Larynx from behind, after removing a portion of the aryepiglottidean fold and upper
posterior portion of left thyroid cartilage. (Henle.) Taep, thyro-ary-epiglottidean muscle ;
Cap, posterior crico - ary tenoid muscle; A, arytenoid muscle; x, kerato - cricoid muscle;
kcps, posterior, superior, kerato-crieoid ligament ; co, cartilage of Santorini ; *, mucous glands
iu tlie aryepiglottic fold.
extends from the posterior ends of the vocal cords to the intra-
arytenoid fold, is bounded by the arytenoids, and is known as the
rirna glottidis respiratoria or intercartilaginea.
The laryngeal muscles dilate and constrict the glottis, and
extend and relax the vocal cords. These effects for the most, part
depend not on the action of a single muscle, but on the co-ordinated
play of several, which makes it harder to obtain any exact know-
ledge of the function of each separate muscle when they are
working together.
The two posterior crico-aryteuoid muscles are the chief, if not
the only dilators of the glottis ; owing to their attachments
and the oblique course of their fibres they rotate the bases of the
Ill
PHONATION AND AKTICULATK >X
137
arytenoids round their vertical axis, and, therefore, draw the two
muscular processes of the arytenoids down and back, and con-
sequently further from the median line, and at the same time
raise the two vocal processes. Isolated contraction of these
muscles must therefore abduct the vocal cords and dilate the rima
glottidis ; their paralysis must, on the other hand, produce in-
spiratory dyspnoea owing to abnormal constriction of the rima, but
it does not cause appreciable disturbance of phonation.
The constriction of the glottis is produced chiefly by the
Oh
.} tr
cl
FIG. M.— Larynx and hyoid bone, from the front. (Henle.) Oh, hyoid bone; litl, lateral hyo-
thyroid ligament ; if, cartilage tritica ; htm, median hyo-thyroid ligament ; ct, crieo-thyroid
ligament; Pp, inferior extremity of palato-pharyngeal muscle; Th, thyro-hyoid muscle; Cir,
erico-thyroid muscle divided into three bundles ; the vertical bundle on the left side has been
removed to show the crico-thyroid ligament i:t.
transverse arytenoid muscle, which runs between the outer
posterior borders of the arytenoids, and by contracting draws the
two bases of these cartilages towards the middle line, and their
mesial surfaces together, so that the intercartilaginous glottis
is closed. When this muscle is divided in any animal, the
posterior portion of the glottis remains fully open.
Other muscles also are concerned in the active closure of the
glottis ; they co-operate with the transverse arytenoids to form
a kind of laryngeal sphincter. Among these are the thyro-
aryepiglottidean, and the thyro-arytenoid muscles. The two first
run from their point of attachment on the inner surface of the
thyroid obliquely backwards over the two posterior surfaces of
138
PHYSIOLOGY
CHAP.
the arytenoids, where they cross in the median line, and then
run along in the aryteno-epiglottidean fold to be inserted in
the base of the epiglottis. The two latter start from the lower
part of the internal angle of the thyroid, and turn backwards
and upwards to the muscular processes of the arytenoid. The
chief function of these muscles is to constrict the glottis, and
reinforce the transverse arytenoid muscle.
The lateral crico-arytenoid muscle also aids in the abduction
of the vocal cords. This muscle runs obliquely from behind and
CO
£M cap
Fin. 93. — Side view of larynx, utter exarticula-
tion and removal of left plate of thyroid
cartilage. (Henle.) Sat, articular surface of
thyroid with cricoid ; (jap and ( 'al, crico-
arytenoid muscles, posterior and lateral ;
co, cartilage of Santorini, below which the
arytenoid and thyro-epiglottidean muscles
(Fig. 91) are seen in profile.
ct
Fie. 94. — Frontal section of larynx, the anterior
half viewed from behind. (Henle.) t, thyroid;
cr, cricoid ; a, plica ary-epiglottica ; Taep,
thyro-ary-epiglottidean muscle ; Toe and
Tai, thyro-aryitenoid muscles, external and
internal : 1, tubercle of epiglottis ; 2, 3, ven-
tricle ; 4, plica thyreo-arytaenoidea superior
or false vocal cord; 5, plica thyreo-ary-
taenoidea inferior, or true vocal cord.
above, forward and downward, viz. in the opposite direction to the
posterior crico-arytenoid or abductor of the glottis.
The tension of the vocal cords is especially due to the crico-
thyroid muscles, which in contracting raise the front part of the
cricoid towards the thyroid, and depress the posterior part of
the cricoid and consequently of the two arytenoids which rest
upon it (Longet). The effect of this rotation of the cricoid on
its transverse horizontal axis is to increase the distance between
the points of insertion of the vocal cords and thus to stretch
them. In order that the vocal cords may be stretched, it is necessary
that the two arytenoid cartilages should be firmly fixed, so that
Ill
PHONATION AND AETICULATION
139
Tae
Tan
they cannot be drawn forward. This is effected by the combined
action of the dilatators and constrictors of the glottis, viz. the
posterior crico-arytenoids (dilatators), the transverse and oblique
arytenoids, the external thyro-arytenoids, and the lateral crico-
arytenoids (constrictors). If the posterior crico-arytenoids alone
contracted with the crico-thyroids, the vocal cords would be
stretched and abducted and the glottis dilated. But it is
essential for the formation of sounds that the cords shall be not
only tense, but also approximated to each other, so that they can be
thrown into vibration by the expiratory air-current. These two
conditions are realised when the constrictors of the glottis are
thrown into action simultaneously with the dilatators.
According to C. Meyer and Griitzner, the genio-hyoid and
thyro-hyoid muscles con-
tribute to the tension of
the vocal cords, as they
raise the thyroid upwards
and forwards in the direc-
tion of the chin, and sup-
plement the action of the
crico- thyroid muscles by
which the rotation of the
crico- thyroid articulations
round the transverse hori-
zontal axis is effected.
The relaxation of the
vocal cords is due to
simple elastic reaction
when the extensor muscles
cease to act. Active re-
laxation of the cords can,
however, be produced by the internal thyro-arytenoids, which
are perhaps the most important muscles for phonation. They
are triangular muscles, which extend with the vocal cords from
the inner angle of the thyroid to the vocal processes of the
arytenoids, but some of their bundles are inserted in the elastic
substance of the cords. When these muscles contract they pro-
duce an opposite effect to the crico-thyroids, and bring the vocal
processes of the arytenoid nearer to the thyroid, which relaxes
the cords. But it is conceivable that contraction of the isolated
bundles inserted into the elastic tissue of the cords may produce
tension of some parts and relaxation of others.
It is very probable that the true function of the internal
thyro-arytenoids in phonation is to regulate the tension and
thickness of the vibrating portion of the vocal cords, by which
a rapid succession of tones of different pitch is made possible.
The internal thyro-arytenoids almost always co-operate in
Km. '.15.— Transverse section of larynx through bone of
arytenoid cartilages. (Henle.) t, thyroid ; PC, pro-
cessus vocalis of arytenoid ; .?//, sinus pyriformis ;
Th, section through thyro-hyoid muscle; A, ary-
tenoid muscle; Toe, Tai, thyro - arytenoid muscles,
internal and external ; Taep, thyro-ary-epiglottidean
muscle ; *, anterior cord of glottis.
140
PHYSIOLOGY
CHAP.
phonation with other laryngeal muscles. If we assume that
during contractions of the muscles which stretch the vocal cords,
the internal thyro-arytenoids which tend to relax them are also
contracting, it is easy to understand the functions of the latter,
which regulate the delicate changes in position of the larynx
and vocal cords necessary in a gradual succession of tones that
differ little in strength and pitch from each other. The feeling
of tension in the larynx in singing with the chest register fully
open shows that in singing all
the laryngeal muscles may be
more or less active, and that the
formation of different musical
notes, gradations of their pitch,
and rise and fall in the scale,
depend on the delicate co-ordina-
tions of their activity, and par-
ticularly on the internal thyro-
arytenoids, which are in direct
and intimate relation with the
vibrating vocal cords, and have
justly been named the " vocal
muscles."
III. The nerves to the larynx
are the two laryngeal branches
of the vagus (Fig. 96). The
superior laryngeal certainly con-
tains more sensory than .motor
fibres ; the former are distributed
by the rainus internus to the
mucous membrane of the larynx
FIG. 96. — Laryngeal nerves from behind, and to the laryngeal muscles as
(Sappey.)l, Superior laryngeal nerve; 2, its flUvp(, nf mnqmilflv cprmp • rhp
external branch ; 3, 4, 5, twigs to mucous HDrCS UlUSCUJdl SenbC , tilt
membrane of larynx ; 6 filaments that con- motor fibres paSS through the
nect lett superior and interior laryngeal
nerves; 7, same nn the right: 8, 8, inferior ramUS externUS to innervate the
laryngeal nerves; !>, branches to posterior ,1 -j -i ,1 i
cricp-arytenoid muscles; 10, branch to Cl'lCO-thyrOld mUSClCS, partly alSO
arytenoid muscle ; 11, 12, branches to crico- t-Uc qr-irfemnirl rnnenlp
aryteiioid and thyro-arytenoid muscles. B dry ten O. SOie.
The inferior laryngeal, or
nervus recurrens, is a purely motor branch which supplies all
the muscles of the larynx except the crico-thyroid.
As Claude Bernard observed complete aphonia in cats after
extirpation of the spinal accessory, it was generally held that
the motor fibres of the larynx came from the ramus interims
(accessorius vagi) of this nerve, although they ran in the vagus.
But the later work of Grabower (1890) showed that the motor
branches to the larynx originate in the vagus, and more
particularly from its lower roots.
Section of both laryngeal nerves produces relaxation of all
in PHONATION AND ARTICULATION 141
the muscles of the larynx, so that the vocal cords assume the
position of elastic equilibrium as in the dead body. Under
these conditions the glottis is moderately open, in the form of
mi isosceles triangle, with the angle of the apex towards the
attachments of the vocal cords on the inner surface of the thyroid.
Contraction of the laryngeal muscles is therefore not required
to hold the glottis open, as it must be in respiration. Laryngo-
scopic observations show, however, that during quiet respiration
when no voluntary influence is exerted upon the laryngeal
muscles the glottis is more widely open than after death. In
quiet respiration the glottis has an average width of 14 mm. in
the adult man, and about 11 mm. in a woman, while on the dead
subject it is about 5 mm. and 4 mm. respectively. This striking
difference shows that in life the posterior crico-arytenoid muscle
is kept continuously in a state of semi-contraction by the reflex
or automatic tonic activity of a centre, which acts exclusively
or predominatingly upon those fibres of the recurrens which
innervate the abductors of the vocal cords.
In many animals this tonic contraction of the abductors of
the glottis varies with the rhythm of the respiratory muscles ;
at each inspiration the glottis dilates, and at each expiration
it is slightly constricted. In man, however, laryngoscopical
observation shows that during quiet breathing these respiratory
oscillations of the glottis do not occur in the great majority of
cases (Sernon), and only appear during forced or dyspnoeic
respiration (see Vol. I. p. 421).
After section of the recurrent laryngeal nerve this respiratory
rhythm ceases, and the cords take up the paralytic position of
moderate separation which is seen after death.
Section of one recurrent nerve alone deforms the glottis owing
to disappearance of the tone of the muscles on the paralysed side,
which brings the vocal cord of that side nearer the median line.
This deformation or asymmetry of the glottis increases during
forced respiration.
The most important effect of section of the recurrent nerves is
the aphonia first described by Galen. Total loss of the voice is
not, however, constant. Haller, J. Miiller, Magendie, and others
noted that many dogs continue to bark after section of the
recurrent nerves, while others are still capable of emitting high
notes, especially when suffering acute pain. Longet confirmed this
fact, and found that the power of uttering high sounds was ob-
served only in dogs a few months old, in which the tension of the
vocal cords produced by the action of the crico-thyroid muscles,
which are not paralysed by section of the recurrent nerves,
suffices for the formation of high sounds, the inter-cartilaginous
O t O
portion of the glottis not being fully developed, owing to the almost
total absence of the vocal processes, so that the cords are kept
142 PHYSIOLOGY CHAP.
sufficiently close together, even when the arytenoid muscles are
paralysed.
Stimulation of the peripheral branch of a recurrent nerve
brings the cord of the same side nearer the median line than does
simple section of this nerve, while stimulation of both recurrent
nerves causes the cords to come together and the glottis to close.
So that normally the effect of the recurrent nerves which contain
fibres for both the abductors and the adductors of the glottis is
domiiiantly on the dilatators ; when, on the other hand, they are
stimulated artificially the effect on the adductors of the glottis pre-
dominates. The explanation of these phenomena seems to be as
follows : Normally, only those fibres of the recurrent nerves which
are connected with a centre intimatelv related with the bulbar
b
respiratory centre exert a constant tonic influence which maintains
the inspiratory dilatation of the glottis ; when, on the contrary, the
two recurrent nerves are artificially excited, all the laryngeal
muscles concerned in voluntary phonatioii (except the anterior
crico-thyroids) contract, and the contraction of the adductors
consequently predominates.
Section of the superior laryngeal nerve on one or both sides
does not appreciably affect the glottis, but it makes the voice
raucous and prevents the formation of high notes owing to the
loss of function of the crico-thyroid muscles which keep the cords
in tension. Longet demonstrated that the peculiar harshness
which ensues on paralysis of the superior laryngeal nerve depends
wholly on its external branch, which gives fibres to the crico-
thyroid. Isolated section of this nerve produces the same effect
as section of the whole nerve. He found, too, that the hoarseness
of the voice can be made to disappear by bringing the cricoid
artificially nearer the thyroid ; it is therefore obviously due solely
to relaxation of the vocal cords. After cutting the internal
branch of the inferior laryngeal, Longet could detect no appreci-
able change in the animal's voice, and electrical stimulation of
this branch produced no effect on the laryngeal muscles, though
Magendie held that the ramus interims contains motor fibres for
the arytenoid muscle.
The centres of the laryngeal fibres, both those which maintain
the laryngeal respiratory rhythm and those which control phona-
tion, lie in the bulb or medulla oblongata.
The centre for respiratory rhythm is closely connected with
the respiratory centre, but is distinct and independent of it. We
saw that the glottis, during quiet respiration, is kept constantly
dilated by the tonic action of the recurrent nerves. Semon and
Horsley, experimenting on cats, further showed that stimulation
of the upper portion of the floor of the fourth ventricle produces
marked widening of the glottis, but the thoracic respiratory move-
ments continue ; the bulbar centre for the laryngeal respiratory
in PHONATION AND ARTICULATION 143
movements can therefore be excited independently of the centre
for the thoracic respiratory movements. Unilateral stimulation
of this centre invariably produces bilateral effects, i.e. abduction
of both vocal cords and widening of the glottis.
The movements of phonation have also a separate centre in the
bull). After separating the brain from the bulb, Vulpian was able
renexly to elicit cries, as though the animal still reacted to the
painful effects of stimulation. Semon and Horsley on stimulating
the ala cinerea and upper margin of the calamus scriptorius,
obtained energetic closure of the glottis, or adduction of both
vocal cords, when the animal was not too profoundly narcotised.
Since phonation is a voluntary act, perfected by practice, it is
regulated by special cortico- cerebral centres which control the
action of the bulbar laryngeal centres.
The cortical centres in the Macacus monkey lie in the lowest
part of the pre-central or ascending frontal convolution ; and in
doo-s, in the lowest part of the pre-crucial part of the sigmoid
gyrus. Electrical stimulation of this area, in either hemisphere,
produces adduction of both vocal cords which lasts as long as the
stimulation (Semon and Horsley). But if this is unduly pro-
tracted the need of breathing causes a pronounced dilatation
of the glottis, which momentarily interrupts its closure.
In man the area of phonation and articulate language is far
more developed ; it lies at the foot of the third frontal convolution,
and acquires a much higher functional significance in the left
hemisphere than in the right. This important subject will be
discussed more fully in Chapter IX.
Extirpation of both cortical speech centres does not paralyse
the glottis in animals. After unilateral extirpation stimulation
of the centre in the other hemisphere produces the same effect-
closure of the glottis — as was previously obtained.
Unduly strong or protracted stimulation of the cortical centre
of phonation may induce an epileptic attack which begins in the
vocal cords, and then spreads to the muscles of the face, neck, and
limbs. The scream with which ordinary epileptic attacks begin
probably depends on the initial excitation of this centre in
the cortex.
IV. Ferrein (1741) was the first who attempted acoustic
experiments on the excised larynx of recently killed dogs, by
bringing the walls of the glottis artificially together, and blowing
forcibly through the trachea.
Johannes Miiller (1839) successfully resumed the study of the
formation of sounds in the larynx of dead bodies. He fixed
threads to the two arytenoid cartilages so that he could alter
the width of the glottis by bringing them more or less closely
together, and produced different degrees of tension in the vocal
cords by pulling the thyroid cartilage forward by weights.
144 PHYSIOLOGY CHAP.
The trachea was connected to a bellows, and the different
pressures at which the air traversed the glottis were measured
by a manometer.
With this method Miiller carried out a long series of experi-
ments which, though less valuable to-day owing to the laryngo-
scopical observations now made on the living subject, were of
epoch-making importance in the history of physiology. When
the cords were brought together, their tension being unchanged,
the laryngeal sounds became higher ; on moving the cords apart,
the sounds were deeper. With increased tension of the cords, the
note could be raised two octaves. With increased air pressure, the
tension of the cords being unchanged, the strength and pitch of
the laryngeal note could be raised a fifth. Lastly, he found that
everything above the true vocal cords could be removed without
altering the pitch of the sounds, and that the office of the accessory
tube, the pharyngo-buccal and nasal cavities, was limited to
altering the pitch.
J. Miiller first constructed an artificial larynx with one or two
membranous tongues of elastic material or arterial wall stretched
across the mouth of a wooden pipe, 011 which he studied the
mechanical conditions for the production of sound and of variations
in pitch, strength, and timbre. But in his conclusions he fell into
the same error as Ferrein, who first compared the vocal cords to
the strings of a violin, and regarded their vibrations as the primary
source of the sounds, the air blast as the bow which threw them
into vibration, and the thorax and lungs as the hand that moves
the bow. Miiller supported this theory, even after W. Weber had
demonstrated by his classical experiments that the sounds of
tongued instruments are essentially due to explosions of air, viz.
to the periodic increments and decrements of pressure as it passes
through the slit that lies between the vibrating tongues.
Direct observation on the living subject of the position of the
glottis during the formation of sounds was an immense advance
in the study of the mechanism of the laryngeal sounds.
Magendie (1816) was the pioneer in this research. He
recognised that it is necessary for the emission of vocal sounds
that the arytenoids and vocal cords be brought together,
while the opening of the inter-cartilaginous glottis does not
prevent the formation of sounds. His method consisted in
exposing the glottis in dogs by an incision between the hyoid
bone and thyroid cartilage. The same method was adopted by
the surgeon Malgaigne (1831), who corrected certain errors in
Magendie's observations, and showed that only the pars niena-
branacea of the glottis is concerned in voice formation.
The human glottis has also been directly observed in persons
who have attempted suicide by cutting the throat above the vocal
cords (Mayo, 1883, and others). Such observations confirm the
Ill
PHONATION AND AKTICULAT ION
145
fact that there is adduction of the vocal cords in the formation
of sounds, so that the glottis assumes the form of a slit.
The discovery of the laryngoscope by the famous singing-
master Manuel Garcia (1854) made it possible to observe the
human glottis directly under normal conditions, during the
emission of laryngeal sounds of different pitch.
The original laryngoscope used by Garcia was a simple metal mirror
fixed to a handle at a suitable angle. After warming it gently over a spirit
lamp to prevent the deposition of moisture, it was introduced into the isthmus
of the fauces, so that a beam of light could be thrown on to the glottis, which
thus becomes visible to the observer, who is looking into the mirror. The
FI0. 07.— Examination of larynx by laryngoscope, u, b, two metal mirrors ; illuminated by a lamp,
which is reflected from a mirror with a central aperture which is fixed in front of the
observer's eye.
latter may be directly illuminated by sunlight, which was Garcia's original
method, or by a lamp at the side of the observer in front of which a large
lens is placed to increase the strength of the illumination ; or by a lamp
placed behind the shoulder of the person observed, which illuminates a
concave mirror, and reflects a beam of light upon the mirror of the laryngo-
scope. The observer watches the latter through a central aperture in the
concave mirror (Fig. 97).
Oertel employed a rapidly intermittent illumination by placing a Mach's
stroboscopic disc in front of the lamp. It is then possible to follow the
vibration of the vocal cords by direct vision.
Szimanowsky obtained instantaneous photographs of the glottis during
the production of the different tones by substituting a photographic apparatus
for the eye of the observer.
The whole of the laryngeal vestibule cannot be seen simultaneously on
the laryngoscopic mirror, but by moving the mirror it is possible to see the
different parts in succession (Fig. 98).
Laryngoscopical observation shows that voice production is
VOL. in L
146
PHYSIOLOGY
CHAP.
preceded by closure of the whole glottis, or of the pars mem-
branacea (Fig. 98).1 Now the emission of tones coincides with
the rapid opening and vibration of the vocal cords by the blast of
air forced through the glottis by the expiratory muscles. The
vibrations of the cords are not limited to their narrow margins,
but extend more or less through their entire mass. At the same
moment the epiglottis is somewhat raised, particularly in high
notes ; the aryteno-epiglottidean folds are stretched ; and the false
vocal cords are drawn slightly nearer together and stretched, but
they do not vibrate. At the same moment the whole larynx
becomes more or less firmly fixed by the action of the extrinsic
muscles (thyro-hyoid, sterno-thyroid, pharyngeal, etc.), and rises
with the emission of the high notes, and falls with the low notes.
During the production of high notes the tongue contracts
energetically, the tip being drawn back, and the base lifted. The
soft palate is raised towards the posterior wall of the pharynx,
FIG. '.is. — Positions of glottis previous to production of the voice.
and the pillars of the fauces approximate and narrow its opening.
In deep notes, on the contrary, the tongue contracts slightly and
remains flat ; the soft palate is raised, and the pillars of the fauces
move apart. But the most important of all these changes in the
voice-producing apparatus are the vibration of the vocal cords
and the form of the membranous glottis, which varies considerably
with the pitch, intensity, and register of the voice.
In order that the vocal cords should vibrate, it is necessary
for the air- current passing through them to be at a certain
pressure, sufficient to displace them from their position of
equilibrium. In a case of tracheal fistula in a woman, Cagnard-
Latour, by fitting a manometer into the mouth of the fistula, was
able to measure the pressure of the blast of air during the
production of sounds of different pitch. He found a pressure of
160 mm. H20 necessary for sounds of medium pitch, of 200 mm.
for high, and of 945 mm. for the highest notes. Griitzner
obtained approximately the same figures in a young man on
whom tracheotomy had been performed.
Adduction of the vocal cords and narrowing of the glottis
1 This is not in agreement with some later observations. — F. A. W.
in PHONATION AND ARTICULATION 147
obstructs the passage of air, and increases the pressure in the
trachea necessary for throwing the vocal cords into vibration.
The loss of voice when the trachea is opened depends on the fall
of the pressure of the expiratory air below the minimum necessary
for the vibration of the vocal cords.
But the pressure of the expiratory air would in itself produce
no musical effect if the vocal cords were not thrown into a proper
degree of tension by their tensor muscles. As we have seen,
paralysis of the anterior crico-thyroid muscles makes the voice
hoarse, and hinders the formation of high tones.
The following general laws of the mechanism of the production
of laryngeal sounds may be deduced from experiments on animals
and observations on man :—
(a) The membranous glottis is the exclusive seat of voice
production. Lesions of the vocal cords render voice production
impossible.
(b) The vocal cords acting as membranous tongues are thrown
into vibration by the pressure of the expiratory blast, and vibrate
synchronously with the air-current. The vibrations of the vocal
cords certainly produce a note, but its intensity is very low, hardly
to be compared with that of the tones arising from the larynx.
The true sounding body is the air, but the vibrations of the air
are determined by the vibrations of the vocal cords.
(c) The vibrations of the air which are started in the glottis
are transmitted to the mass of air lying below as well as above
the vocal cords. The vibrations of air in the windpipe, bronchi,
and lungs are communicated to the thoracic wall, and can easily
be detected by applying the hand to the chest. This resonance
of the chest must certainly produce increased intensity of the
laryngeal notes, though it is difficult to appreciate its importance.
(d) The resonator proper consists of the parts lying above the
vocal cords, the laryngeal vestibule, and upper portions of the
pharynx, mouth, and nose. It is on the vibrations of the air in
this tube that the special qualities which characterise the human
voice depend. The necessary coincidence between the vibration
of the vocal cords and that of the air in the resonator is obtained
by the varying tension of the walls, and the alterations in length,
breadth, and shape of the cavity, by upward and downward move-
ments of the larynx, and alterations of the tongue, soft palate,
pillars of fauces, cheeks, and lips.
(e) Moro-agni's ventricles are of little importance as resonators,
but they give space for the free vibration of the vocal cords, and
produce a secretion by which the laryngeal mucous membrane is
kept moist.
(/) The false vocal cords can alter the form of the laryngeal
vestibule by their approximation towards the middle line, and
thus change the character of the tone produced by the vibrations
148 PHYSIOLOGY CHAP.
of the true vocal cords. It is doubtful whether they can act as
dampers by dropping to the level of the true vocal cords.
(g) The function of the epiglottis in voice production is also
uncertain. But the positions it takes up must certainly contribute
to altering the character and quality of the voice.
(A) Abundant proof of the great influence on the character of
the voice of the different forms which may be assumed by the
pharyngo-buccal cavity owing to the various positions of the soft
palate, tongue, and lips, will be shown when we come to discuss
language and particularly the formation of the vowels.
V. The sounds produced by the human voice are all comprised
in the interval of three and a half octaves, or a little more, but no
one individual possesses such an extensive vocal range. Few
indeed, and only after long practice, succeed in acquiring a range
of even three octaves, and in these rare cases the end-notes of the
scale are deficient in strength and clearness. The average compass
of a well-developed singer seldom exceeds two octaves.
The range of voice within the limits of the two octaves
depends principally upon the dimensions of the larynx, which
differs considerably in the sexes. In either sex musicians dis-
tinguish three different varities — soprano, mezzo-soprano, and
contralto, for the female voice ; tenor, baritone, and bass, for the
male voice. The soprano voice is about an octave higher than
the tenor ; the contralto about an octave above the bass. A few
notes between G and F of the third octave of the piano are
common to baritone and soprano. The table, p. 149, shows the
range of voice usually met with in different singers. Opposite
each note is the number of simple vibrations which correspond
to it according to the international concert pitch a1 = 435 (see
Chap. V. of Vol. IV.).
At puberty there is a rapid development of the larynx which
alters the range of the voice. Owing to the elongation of the
cords the voice generally falls an octave in the male and about
two notes in girls. A boy's soprano voice usually changes to a
tenor, an alto to a baritone. While changing, the voice becomes
harsh, uneven, and guttural ; this is due to a transitory hyperaernia
and swelling of the vocal cords which accompanies the growth of
the whole organ.
In eunuchs the voice of childhood is usually retained, but it
becomes stronger and fuller.
The upper limit of the vocal tones is reached at about the age
of eleven years. Children's voices may reach the highest notes of
the fifth octave, which are very seldom attained by the highest
sopranos.
The range of a child's voice varies, according to Engel, from
three whole toues to two full octaves. Paulsen (1895) found on
examining a large number of children that the compass of the
III
PHONATION AND ARTICULATION
149
voice in the sixth year was about an octave, by eleven it was
twice as great, by fourteen still more extended. Girls' voices
reach their widest range at the thirteenth, boys' voices at the
fourteenth year.
In advanced life the upper tones gradually weaken, and
ultimately disappear. A soprano voice nearly always turns into
a mezzo-soprano, and a tenor often becomes a baritone. These
changes, unlike those of puberty, come on gradually, and are due
to loss of elasticity, caused by calcification of the laryngeal
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cartilages, which begins about middle age, and increases with old
age. The thyroid ossifies first ; then the cricoid ; much later the
arytenoids. In old age the compass of the voice shrinks, and its
resonance diminishes and becomes tremulous, owing to retrogressive
changes in the neuro-muscular apparatus of the larynx and the
expiratory muscles.
Voices differ not only in their relative position in the scale, but
also in quality or timbre. Just as it is easy to distinguish the tone
of a basso concerto from a violoncello, and that of a clarinet from
an oboe, so a practised ear can distinguish a bass from a baritone
or tenor, and a contralto from a soprano, even when they are
singing the same notes.
Generally speaking, " bright " voices can be distinguished from
150
PHYSIOLOGY
CHAP.
" dull " voices, while others are " full," i.e. of medium, normal
timbre. With bright timbre the larynx is raised, the resonance
cavity is short, the mouth wide open, the glottis constricted ; with
dull timbre the larynx is lowered, the resonance tube long, the
oral opening constricted, the glottis rather wider. The difference
in quality is most distinct if the same note is sung with the two
vowels A and U.
It is an important fact that the voice can be varied in the
same individual by altering the position of the vocal organ.
When the scale is sung from the lowest to the highest note the
voice retains the same quality between certain limits, the pitch
only being altered. But in rising gradually to higher notes the
voice is not only raised hut also changes in quality. The voice is
usually divided into three registers, in analogy with the registers
of an organ : these are the chest register, the middle register, and
the head register, or falsetto.
A B
Fie. 9; i. — Aperture of glottis during emission of low notes (A), and liigh notes (B),
with chest register.
Laryngoscopical observations show that each register corre-
sponds to a particular position of the larynx, which is constant for
all notes comprised in that register, the tension of the cords alone
being altered according to the height of the notes. In passing
from one register to another the position of the larynx changes
abruptly.
The exact positions of the larynx in correspondence with the
different vocal registers is a subject of discussion among the
laryngologists.
It is generally admitted that in the chest register the vocal
cords vibrate over their whole length ; the aperture of the glottis
is elliptical and wide or narrow, according to the pitch of the
sounds ; the intercartilaginous portion of the glottis is also more or
less widely open ; and, lastly, the vibrations of the cords, which can
be clearly seen by the laryngoscope, are transmitted to the chest
walls, hence the name of " chest " register (Fig. 99).
In singing with a head register, or falsetto, the vocal cords are
shorter and narrower; the intercartilaginous portion of the glottis
is completely closed ; the membranous glottis, on the contrary, is
Ill
PHONATION AND AETICULATION
151
open, Itut only in the middle part, where it forms a comparatively
wide space through which the expired air can readily escape
(Garcia) ; this produces greater resonance in the pharyngo-huccal
cavity, and vibrations of the cranial bones (hence "head" voice);
the false vocal cords are tensely stretched, and approach the true
cords, or, according to some authors, actually come into contact
with them; the vibrations of the cords are only visible in the
most forward part of their free edges (Fig. 99«)- Other observers.,
on the contrary, state that in the head register the glottis is open
in its entire length, although it is reduced to a linear slit (French).
Possibly all singers do not employ the same laryngeal mechanism
in the different registers.
Among the contradictory interpretations of the fundamental
differences between the chest register and the head register, that
of Lehfeldt (1835) found wide acceptance, and was adopted by
Fit;. 99a. — Aperture of glottis during emission of lii.^h notes (C), with chest register ; and of
highest notes (D), with head register. (Mandl.)
Job. Miiller and many other physiologists. He assumed that in
the falsetto voice only the free edges of the vocal cords are thrown
into vibration, while in the chest voice the whole of the cords
vibrate. Bonders held that in the chest register the musculus
vocalis (internal thyro-aryteuoid), being contracted and tense,
participates in the vibrations of the cords, and that its weight
drags down the pitch. In the falsetto register, on the other hand,
as the musculus vocalis is relaxed, the vibratory movement is con-
fined to the edges of the cords; the pitch consequently becomes
higher owing to the reduction of the vibrating mass. The relaxa-
tion of the musculus vocalis accounts for the comparative breadth
of the glottis and the more rapid absorption of the reserve air, as
well as the more marked fatigue and greater vibration of the head.
After Oertel's laryngoscopical observations (1882) by Mach's
stroboscope method (intermittent illumination of the glottis) this
theory lost ground, and was gradually replaced by another,
according to which, when the falsetto voice is produced, nodal lines
are formed in the vocal cords parallel to their free borders. The
increased height of the falsetto notes is therefore due, not to
152 PHYSIOLOGY CHAP.
decreased depth and breadth of the vibrating portion but to the
subdivision of the vocal cords into two vibrating sections, by a
nodal line which runs parallel with their edges. When the
musculus vocalis is tense and contracted like the edge of the cord
in which it is embedded, it vibrates with them, and this prevents
the formation of nodal points, and the chest voice consequently
results.
The change from the chest register to falsetto is on this new
theory due principally to the relaxation of the musculus vocalis.
This change is usually easier and less apparent in women than in
men.
The singer's art is largely directed to equalising the resonance
and timbre of the voice in different notes of the scale, so as to pass
smoothly from one register to another. Many important exercises,
again, aim at facility in altering the strength of a tone without
changing its pitch — i.e. at singing crescendo and decrescendo. The
strength of the laryngeal notes depends on the amplitude of the
vibrations of the vocal cords, due in its turn to the pressure of the
expiratory current. But when the position of the glottis and the
tension of the vocal cords remain unchanged it is possible by
increasing the pressure of the air-blast to raise the height of a
tone a fifth ; consequently, to produce a crescendo on the same note
there must be a compensatory alteration of the vocal cords in order
to preserve the same number of vibrations. Compensation in the
opposite direction is necessary to produce a decrescendo. These
compensations are obtained by decrease or increase of the tension
in the vocal cords (relaxation or contraction of the crico-thyroid
muscles), or by increase or decrease in the mass of the vibrating
parts (contraction or relaxation of the musculus vocalis). Laryngo-
scopical observation confirms sometimes the one, sometimes the
other interpretation. Both are difficult adjustments, which are
easily executed even by experienced singers, and are only learned
by long practice.
" Expression " depends on these modulations of the strength of
a note without altering its pitch. No musical instrument is better
adapted than the larynx to give expression in singing, for the
larynx is a living instrument, brought into direct relation with the
emotional and motor centres of the performer by means of its
sensory and motor nerves.
VI. The power of utilising the larynx as a musical instrument
is not common as a natural endowment, not only because few people
possess the range, volume, and quality of voice that is indispensable
for singing, but also because many people do not understand the
right use of the larynx as a musical organ, though every one is more
or less capable of using it as an organ of speech.
In former days, particularly towards the end of the eighteenth
century, the difference between the singing voice and the speaking
ni PHONATION AND ARTICULATION 153
voice was much discussed. The voice used for speaking is
commonly held to be different from that used in singing. But
this is a mistake. In compass the only difference is that the tones
used in speaking are generally comprised within half an octave,
while those employed in singing extend over two octaves. A more
important difference lies in the fact that in speaking many sounds
(consonants) are used, so that the tones and the intervals between
the tones are not so plain as in singing. There are not therefore
two different voices but rather two modes of using the same voice ;
dramatic recitation and lyrical declamation stand midway between
speaking and singing.
Owing to these differences between the singing voice and the
speaking voice, mistakes in the correct pronunciation of words, and
in the true intonation, modulation, and accentuation of phrases
and periods, are often tolerated in speaking because they are less
offensive ; in singing, on the contrary, false intonation and wrong
notes produce a sense of discomfort which is unbearable to the
trained ear.
Longet distinguishes three different causes for the very common
failure to sing in tune, which amounts, in some cases, to a total
incapacity :—
1. The individual " has no ear," i.e. his sense of hearing is not
acute enough to enable him to distinguish between the different
tones. No one with this defect can sing. In fact, auditory
sensations are at least as necessary to the adequate function of the
organ of phonation as are visual and tactile sensations in the
movements of the body and limbs. The actual development of
the voice is dependent on the functioning of the organ of hearing ;
dumbness is associated with congenital deafness, and is almost
always due to lack of auditory sensations and not to defects in the
voice-producing apparatus.
2. The individual does not sing well because his tone-memory
is defective, i.e. notes do not leave clear and distinct traces in his
memory, from which he can easily revive the corresponding tones.
He is quite capable of singing in tune to an instrument, or with
other true singers, but when left to himself he cannot hit or keep
up the correct note, and is aware that he sings out of tune. In
these cases the musical memory can be developed gradually by
careful training, so that the faults in singing are reduced or
disappear.
3. The individual cannot sing correctly because his larynx
cannot produce true notes in response to volitional impulses. lAhis
not uncommon peculiarity is due not to anomalous conformation
of the larynx, but to some imperfection of the nervous mechanism
by which the tactile and muscular sensations are transmitted
centripetally to the centre, or the motor impulses centrifugally to
the laryngeal muscles.
154 PHYSIOLOGY CHAP.
The ability to sing depends not on the construction of the
larynx, but on the possession of the proper nervous mechanism, by
which both the auditory sensations and the tactile and muscular
sensations are capable of guiding the volitional impulses in such a
way that these are promptly and accurately transmitted to the
corresponding muscles. Congenital delects in these nervous
mechanisms can also, to some extent at least, be overcome by long
and steady practice, just as a violin player is able in a wonderful
way to cultivate the nervous mechanisms which move the muscles
of his hands. A perfect singer is not born, but trained, as a
concert player is developed after long practice ; but of course in
either case a favourable congenital predisposition is indispensable
to the mastery of the art.
It is possible by minute and careful analysis of the voice to
detect comparative correctness or faults of its formation, as well as
of the different notes of the musical scale which it is able to
produce.
A voice is " true " when the vibration numbers of its notes
correspond exactly to their place on the scale ; it is " false " when
the vibration numbers are greater or less than those of the notes.
Rising (crescenti) voices are the more usual ; falling (calandi) voices
less common, except in a singer whose voice is worn out. It is
often the case that certain notes are false, while others are in tune.
Minor keys are more difficult to sing correctly than major keys.
Hen sen by Konig's manometric flames, Kliinder by the
phonautographic method which records the vibrations of the
original tone and the note sung in unison with it, made interest-
ing researches on the accuracy of the voice. They discovered that
it is very difficult to hold a note with a constant number of
vibrations for a given time. Owing to positive or negative
variations in the tension of the vocal cords, the truest voices
fluctuate in vibration frequency above and below the normal
mean. The mean error for any particular note is not more than
0'35 per cent ; but in holding on a note, or in singing crescendo
or diminuendo it may amount to 1*54 per cent, owing to the
difficulty of compensation, even in the larynx of a professional
singer with long practice, in forming and holding on the notes.
This slight natural imperfection of the voice in keeping on the
notes is due not to want of ear, but to the larynx and its vocal
muscles (thyro-arytenoid muscles), which are incapable — no matter
how much they are exercised — of keeping up the exact, degree of
tension required for the several notes of the scale, without slight
periodic variations. The slight imperfections in the formation
and emission of tones, perceptible even in expert singers, depend
more on the ear than on the larynx, and are due to defective
sharpness in the memory traces of the respective tones.
VII. Articulate language is limited to man, and is one of the
in PHONATION AND AETICULATION 155
highest faculties by which he is distinguished from the rest of
the animal kingdom. From the physical point of view it consists
in a series of special expiratory and sometimes inspiratory sounds
produced in the resonance cavity of the pharynx, mouth, and nose,
which may be, but need not be, combined with the laryngeal
tones. In talking aloud the laryngeal tones are combined with
the pharyugo-buccal sounds into articulate speech, but in whisper-
ing, i.e. speech without voice, there are no laryngeal tones. It is
even possible to speak sotto voce without a glottis, as after loss of
the larynx by surgical operation. The resonator is therefore of
fundamental importance to the formation of words, while in
singing it is of secondary importance.
The vocal apparatus has rigid parts, such as the hard palate
and nostrils, and mobile parts, such as the lips, tongue, and soft
palate. It is the changes in form of the resonating cavity due to
the movements of these soft parts which give rise to the different
articulate sounds. Sometimes these changes do not interrupt the
continuity of the vocal instrument ; at other times they constrict
or close it, rendering the escape of the expired air difficult or
impossible. This constriction or occlusion may occur in certain
regions, as in the glottis, in the isthmus of the fauces, between the
soft palate and dorsum of the tongue, between the hard palate or
alveolar arches and the tip of the tongue, or at the lips. These
are known as the regions of articulation.
The number of elementary sounds which in different combina-
tions build up a language or dialect is limited, but it varies
considerably in different languages and dialects. The sounds are
distinguished as vowels and consonants in the grammar of every
language. The value of this distinction has been much discussed,
and many erroneous definitions have been made, showing that
there cannot be any absolute difference between vowels and
consonants, by which they can invariably be recognised. One
group of consonants, in fact, has the character of vowels, and
these sounds are frequently referred to as the semi- vowels.
Speaking generally, it may be said that the vowels are laryn-
geal sounds, which assume their specific character in the resonating
cavity owing to the predominance there of one or two tones of a
given pitch. The consonants, on the contrary, are sounds which
are almost invariably formed in the resonating cavity, and may
or may not be combined with laryngeal tones.
The vowel a (ah) is often regarded as the foundation from
which all the other vowels may theoretically be derived. It does
in fact represent a laryngeal sound as little modified as may be
by the resonating cavity, which remains as widely open as possible.
C. Hellvvag in his Deformatione loquelae (1781) distinguishes three
typical vowels, which produce the maximal difference to the ear.
These three are the only vowels found in hieroglyphs, and in
156 PHYSIOLOGY CHAP.
Indian, Gothic, and Arabic writing. They are i (ee\ a (ah), u (00).
All other vowels used in modern languages and dialects are inter-
mediate, and are derived from these three typical vowels.
The system of distinct vowels used in different languages and
dialects is represented in the following diagram of Briicke (after
Hellwag) :—
A
Ae A°
Ea Aoe O
E E° O 0
I Iu U1 U
The angles of the triangle are occupied by three typical vowels ; at
the sides and within the triangle are the intermediate vowels, many
of which are not represented in written language by special signs.
The mouth takes up a definite position for each vowel according
as it is pronounced aloud or whispered. These positions of course
differ most for the three typical vowels.
As shown by Fig. 100 the larynx is most raised at i (ee), the
lips are drawn back and the oral aperture is widened transversely,
the teeth are brought close together, and the tongue is raised
from the floor of the mouth and brought near the palate so as
to leave only a narrow opening for the air. With u (oo), on >the
contrary, the larynx is lowered as far 'as possible, the oral aperture
is brought forward and constricted, the lips forming an almost
circular opening, owing to contraction of the orbicularis, and the
tongue is dropped towards the floor of the mouth and raised
behind towards the soft palate. Lastly, with a (ah) the vocal
tube has a length intermediate between i (ee) and u (oo), the
larynx is least displaced, the mouth is wide open and rounded,
and the whole tongue is drawn back towards the floor of the
mouth so as to form a funnel-shaped cavity.
Certain authors distinguish a (ah,) as pharyngeal, i (ee) as
palatal, u (oo) as velar (Fig. 100), but these terms have little
physiological value. The phonic characters of the different vowels
depend essentially on the position and special form of the whole
resonance cavity, and not merely on the different regions in which
it becomes constricted.
In the intermediate vowels the different movable parts of the
resonator take up intermediate positions : e (eh), ea (e = let), ae
(a = hat) are formed between i (ie) and a (ah) ; o (oh), oa ( = or),
a° (6 = shot) between u (oo) and a (ah).
The pure vowels are pronounced with the soft palate raised,
and the nasal cavities more or less completely closed (Fig. 100).
When the soft palate is not raised the vowel has a nasal sound,
and if the nostrils are closed this is intensified, because the air
in the nasal cavity is better able to vibrate in unison with the
air of the pharyngo-buccal cavity.
Ill
THONATION AND AETICULA.TION
157
In pronouncing the fundamental vowel a (ah), where the
oral aperture is maximal, the soft palate is least raised
(Czermak) ; 011 dropping from a to the end-vowels u and i the
soft palate is raised and the nasal cavity more perfectly closed
in proportion as the oral cavity is constricted. This agrees with
the fact that a, o, e are easily rendered nasal, which is difficult
for i and u.
The complete series u (oo) . . . a (oh) ... i (re) corresponds to
FIG. 100. — Shape of oral cavity in the production of the three fundamental vowels (Grutzner.)
the progressive rise in pitch when the vowels are pronounced with
the ordinary breath. Although the several vowels can be pro-
nounced on different musical notes it is very difficult to enunciate
u clearly in the highest soprano, and i in the deepest bass.
U... i really represent the vowel -limits. In uttering these
the canal is most constricted ; at u the opening of the lips is
narrowest, at i the oral cavity is smallest, owing to the rise of
the tongue which divides it into two. Beyond these limits the
character of the vowel sounds is obscured, and approximates to
that of the consonants.
158 PHYSIOLOGY CHAP.
The fact that the vowel limits are reached when the resonating
cavity is most restricted, and blocks the passage of the air, agrees
with the fact that it is impossible to sing u and i very long and
loud like the other vowels. According to Wolf u can only be
heard distinctly at 280 paces, i at 300, while a is quite audible 360
paces distant.
On the other hand the vibrations of the walls of the resonance
cavity produced by the vibration of the air is maximal with the
vowels u and i, minimal with a. On stopping the ears, u and i
sound very loud to the ear, a much less so. On applying the palm
of the hand to the head, the cranial bones are felt to be vibrating
at u, still more strongly at i, and not at all at a, e, o. This fact has
been utilised in teaching deaf mutes to pronounce i, which they find
the most difficult.
The diplitliongs should not be confused with the intermediate
vowels. Grunmaeh erroneously regards a, u, o as diphthongs ; in
our opinion it is more correct to define them with Goidanich, as
organic alterations of the normal vowels. All the intermediates
represent special vowel sounds due to special positions of the phona-
tory apparatus. In diphthongs, on the contrary, as Brticke noted,
there is a rapid passage from the position of one vowel to that of
the next, the first being almost always accentuated. In the
diphthongs au ( = how), ai ( = high'), etc., the first vowel functions
as the sonant, the second as a consonant.
VIII. The formation of the different vowels is thus funda-
mentally due to the special positions assumed by the pharyugo-
buccal cavity acting as a resonator, and we next have to determine
the physical nature of the vowels, i.e. the partial tones of which
they are composed, and the relations of intensity on which their
timbre or quality depends. This problem is more complicated
than appears at first sight.
Generally speaking, the sound of any musical instrument is
a compound, in which one fundamental tone, the deepest and
strongest, and several harmonic over-tones, weaker in proportion
as their pitch is higher, can be distinguished. But this theory is
not applicable to the human voice, especially not to the complex
sounds in which we can distinguish the specific characters of the
different vowels. This is evident from the following facts :—
(a) The different vowels can be recognised even when they are
whispered, that is, uttered without any laryngeal voice.
(&) The different vowels can be uttered either in speaking or
singing to the same musical note.
(c) Any vowel may be sung to different notes of the scale, and
recognised for each note.
These three points suggest that the complicated laryngeal
sounds acquire their special vowel character from the pharyngo-
buccal cavity, which acts as a resonator, and reinforces certain
in PHONATTON AND AETICULATION 159
partials, while others are excluded, according as it assumes the
position for saying or singing one or other of the vowels.
The earliest experiments on the physical nature of vowel tones
were made by Willis (1829), and Wheatstone (1837), who con-
structed a theory of vowel tones which remained unnoticed for
twenty years. Douders (1857) first showed clearly that the cavity
of the mouth for different vowels is tuned to different pitches. It
forms a resonator which can be tuned to the different sounds
characteristic of different vowels.
In order to ascertain the tones which characterise the several
vowels, Donders cut out the laryngeal sounds which usually
accompany them, by whispering them one after the other ; under
these conditions sounds are produced in which the ear can re-
cognise a definite pitch in the dominating tone, which varies for
the different vowels, but is approximately constant in all persons
of the same sex and age. These sounds are caused by the air-blast
in the oral cavity, where the tones are reinforced so that it is
possible to recognise the different vowels, although they are
wreaker than the normal voice. In speaking or singing the
sounds given out by the resonator are associated with the laryngeal
sounds, and the specific partials of the different vowels are greatly
reinforced, and give the laryngeal sounds their characteristic
timbre.
In his classical work Die Lehre von den Tonempfindungen
Helmholtz placed his theory of vowel-tones on a strict scientific
basis, and extended Bonders' hypothesis. According to Helmholtz
" the vowels of speech are in reality tones produced by membranous
tongues (the vocal cords) with a resonance chamber (the mouth)
capable of altering in length, width, and resonant pitch, and hence
capable also of reinforcing at different times different partials of
the compound tone to which it is applied." J
In order to determine what partial tones of the mouth cavity
give their vowel character to the laryngeal tones Helmholtz
employed a more accurate method than that of Donders. He
struck tuning-forks of different pitch, and held them before the
open mouth arranged for the pronunciation of each vowel in turn.
The pitch of the fork which then sounded loudest gave the proper
tone to which the mouth was tuned. Helmholtz found that the
pitch of the vowels rises progressively from u (oo) to a (ah) and
from a (nil} to i (ee). In u, o, a he only distinguished a single
note ; in ae, e, i, oc, u' two different notes, because the mouth cavity
is divided in the pronunciation of these vowels by the rise of the
tongue (Fig. 101). He maintained that the vowel notes are the
same in men, women, and children. The least change in the
position of the oral cavity modifies the quality of the tone, and
thus gives rise to the intermediate vowels which are so common
1 Sensations of Tone, Helmholtz, tr. Ellis from 3rd ed., p. 153, 1875.
160
PHYSIOLOGY
CHAP.
in the Franco-Italian and Anglo-Saxon languages. This fact,
according to Helmholtz, explains why the vowel tones as fixed
by Bonders — and also by Merkel, Auerbach, Krinig, and other
n f :
•
»•
9-
r
>
*-
f-
— v, —
VL •» *
rrr\r i f
vy 1
f
9
y d 0 A A
*
E r <
i
'.
[)
T
ri
FIG. 101.— Pitch of vowels according to Helmholtz.
later observers — differ in certain respects from those which he
obtained.
He finally concluded that " vowel qualities of tone consequently
are essentially distinguished from the tones of most other musical
instruments by the fact that the loudness of their partial tones
FIG. 102. — Kcinig's apparatus for illustrating the quality of vowel tones by a manometric flame.
Above, the figure shows a section of Konig's manometric capsule and the rubber membrane
which divides the stream of gas from the air of the tube that is sung into.
does not depend upon the numerical order, but upon the absolute
pitch of those partials." l
Helmholt/ attempted to demonstrate the correctness of his
view by synthetically combining the tones of certain tuning-forks
1 Page 172, Ellis' tr., q.v.
Ill
PHONATION AND ARTICULATION
1G1
in his well-known vowel apparatus. He obtained the sound of u (oo)
by combining the fundamental tone I1 \vith/&2 ; the sound of u (oh)
by combining the same fundamental tone with &3 ; the sound of a
(ah) by combining bl with I4. He was, however, unable to repro-
duce the highest tones of e (ch) and i (re) by the tuning-forks.
The vowel tones were also studied by Ko'nig with the aid of
his mauometric flame apparatus (Fig. 102). This method is very
useful in analysing the complex nature of the vowel tones, since it
shows the difference in the form of sound-wave not only for the
IT
Fio. 103.— Flame pictures of the vowels a (ah), o (oh), u (oo), in three different keys.
separate vowels, but for the same vowel at a different pitch. The
duration of the wave-periods is, however, the same for the different
vowels sung to the same note (Fig. 103). The alteration of the
form of the wave while the period is constant must be due to the
superposition of tones developed in the mouth, characteristic of
the vowels upon the tones emitted by the larynx. But it is not
possible from the simple wave-form shown by the flames to
determine the number, pitch, and strength of the partial tones
from which the different sung vowels result.
Hallock (1896) employed a method founded on that of Ko'nig.
He connected eight resonators in harmonic series with as many
Konig's man om etric capsules, sang a vowel in front of them, and
then photographed the reflection of the flames in a mirror. From
VOL. Ill M
162 PHYSIOLOGY CHAP.
these photographs the partials present in any vowel tone within
the range of the resonators could be detected.
Edison's invention of the phonograph (1877), and its perfection
by himself, by Graham Bell and others, reopened the whole
question of vowel tones, to which Fleeming-Jenkm, Ewing,
Hermann, Hensen, Pipping, Boeke, Lloyd, M'Kendrick, and others,
have contributed in the controversy. The chief question has been
whether each word has an absolute or a relative pitch, and whether
on changing the prime tone to which a vowel is sung, its principal
over-tones change too, as is the case with ordinary musical instru-
ments ; or whether the height of the partial tones which give the
vowel its character always remains the same, independent of the
pitch of the prime tone to which it is sung.
The method employed for solving this difficult problem con-
sisted in taking graphic tracings of the vowel sounds, or vowel
phonograms, and then analysing the complex curves of these
sounds into the simple curves of the component tones by means of
Fourier's theorem.
Bonders (1870) first applied the phonautograpli of Leon Scott
to the investigation of vocal phonograms. In 1878 Fleeming-
Jenkin and Ewing employed Edison's tin-foil phonograph for
this purpose, although it was too imperfect to produce the sounds
of all the vowels clearly. These authors came to the conclusion
that both relative and absolute factors entered into the composition
of the vowels — an intermediate theory already accepted by
Auerbach and by Helmholtz in later editions of his book.
Hermann took up the subject about 1890, by the improved
wax-cylinder phonograph, and photographed the curves by a
beam of light, reflected from a small mirror attached to the
vibrating disc of the phonograph. The curves thus obtained,
representing the wave forms of the vowel tones, were then
analysed by Fourier's method.
Hermann found that the phonograph only reproduces the
sung vowels accurately when the cylinder rotates at the same
rate as that at which they were recorded, and that the quality
of a vowel varies considerably with the rate of the cylinder.
He maintains the fixed-pitch theory, and states that there is
for each vowel a characteristic tone which he terms the formant.
He further assumes (and in this his theory differs from all others)
that the formant need not necessarily be a partial tone of the
fundamental. The pitch of the formant may vary considerably ;
with the same prime it may vary in certain cases as much as
several semitones. Fig. 104 shows in musical notation the pitch
of the vowel according to Hermann.
Pipping's results in the main agree with those of Hermann.
He collected and analysed the vowel curves by means of Hensen's
gramograph.
Ill
PHONATION AND AKTICULATION
163
Sauberschwartx with Griitzner (1895) investigated the subject
by an ingenious application of the laws of the interference of
sounds. The vowels were sung into the mouthpiece of a long
tube, to which other short tubes of definite length were attached.
By closing the outer end of certain of these tubes various partials
could be extinguished by interference, and the listener at the
other end of the tube observed an alteration in the quality of
the vowel. Sauberschwartz, generally speaking, supports Hermann.
Later researches by Boeke, M'Kendrick and others added
new facts to the analysis of vowel sounds. At the Fifth
International Physiological Congress at Turin, Hensen stated
that the resonance tones of the oral cavity arranged for the
pronunciation of different vowels are variable within certain
limits, as had been established by Pipping. But he also showed
that the pitch of the laryngeal tones produces a rise in the oral
resonance tones. At a they may rise from 940 to 1175 ; at o
1
!
1
j j
L
J
i
i
™
•
-#•
ff
j
— j —
~]r * —
i
— J — 5^ —
™
^
ln\
i
v Is
*
t -A-
f
u o
FIG. 104. — Pitch of the vowels according to Hermann.
from 498 to 552 double vibrations. The problem of vowel sounds
is therefore more complicated than was supposed, and still awaits
its final solution.
In conclusion, Bonders' theory, which assumes that the oral
cavity is tuned for each vowel to a tone of fixed and unalterable
pitch, whatever the fundamental laryngeal note to which it is
sung, is certainly too restricted. Each vowel, however, undoubtedly
has one or more predominating partial tones, formed by the oral
cavity, on which the specific character of that vowel depends. Since
the form of the mouth varies with the individual and the race, and
the positions it assumes in different dialects and even in different
individuals in the pronunciation of the several vowels are not
and cannot be identical, it is easy to see why the formants of
any vowel are not identical in all cases. They approximate,
however, in certain common characters, by which it is possible
to identify a vowel, however differently it may be formed by
different individuals. It is also certain that the resonating
cavity varies very little when a musical scale is sung to a single
vowel. The ear is always able to recognise the vowel sung,
whatever its pitch ; each vowel, however, has a special register
in which its quality is best ; the soprano is best adapted to the
164 PHYSIOLOGY CHAP.
end- vowel i, the bass to the end-vowel u. Finally, the clearness
and purity of vowel-formation varies considerably in different
languages. It is generally admitted that the sung or spoken
vowels are purest in the Italian tongue, and least so in English.
Italians, moreover, prefer the fundamental vowel sounds a, i, u,
which He at the extremes of the natural system ; they also admit
the middle vowels e and 6, b and 6 (open and closed), but reject
all other intermediate vowels. The English, on the other hand,
not only prefer these, but have further developed a whole series
of vowels characterised by imperfect formation, which makes
them very difficult to recognise and classify.
IX.1 It is difficult to draw up any rational classification of
consonants. The most satisfactory would be based on their
objective, physical nature, but we have no means for the physical
analysis of elementary consonant sounds, such as enables us to
determine the physical nature of musical tones. Hermann found
himself at a loss after some introductory experiments. We
can only fall back on the physiological classification, which
is founded on the mode of producing the consonant sounds and
their subjective acoustic character.
Hermann made a primary division of consonants into two
groups, voiced and voiceless, according as the sounds formed are
accompanied by laryngeal tones or not. Voiced consonants are
much more numerous than voiceless consonants ; they are sub-
divided into semivowels, or liquids (which can function either as
consonants or vowels, and can be pronounced alone, independent
of other vowel sounds), and sounding consonants.
It is indispensable to the perfect formation of vowel sounds
that the pharyngeal cavity should be closed off from the nasal
fossae. When this does not take place, the quality of the vowels
alters and they become nasal, since the expiratory current passes
through the nose as well as the mouth. On closing the nostrils
the nasal character is intensified and may be more prolonged.
This nasal quality characterises the French language, but is also
present in Italian, Spanish, and all other languages.
The nasal vowels an, en, 6n represent the transition between
the vowels and the liquids or semivowels.
The semivowels are in, n, ng, I, and r. They have the
character of vowels because they are always uttered with the
voice, i.e. they are accompanied by vibrations of the glottis
(except when whispered), and sometimes carry the accent, when
they function as pure vowels. They approximate to consonants
because they are pronounced with the mouth partly or entirely
closed, and in the majority of cases the accent does not fall on
them, so that they mostly play the part of consonants.
1 This section has been considerably abridged from the Italian text, which
contains more detail than is required by the physiological student. — ED.
Ill
PHONATION AND ARTICULATION
165
The sounds in, n, n<j, constitute a distinct group of nasal
semivowels (rhinophones) characterised by the expulsion of the
expired air through the nose, where the laryngeal tone acquires
a characteristic resonance, while the mouth is closed in a definite
position. For m the mouth is closed with the lips pressed
together (labial articulation). For n the oral cavity is generally
closed by applying the tip of the tongue to the upper alveolar
arch (alveolar articulation) or to the hard palate (palatal articu-
lation) (Figs. 105 and 106). In ng (represented in Sanskrit
by a special symbol) the mouth is closed by the approxi-
Fio. 105. — Articulation of >i".
(Luciani and Baglioni.)
FIG. 106. — Articulation of gna.
(Luciani and Baglioni.)
Impression left by the tongue stained by cocoa powder previous to articulation.
mation of the dorsum of the tongue to the soft palate, either
more to the front (when preceded by e and i as in Engel,
thing} or more to the back (if preceded by a and o, as in
Wange, long].
The semivowels / and r are distinguished from these nasal
sounds by the fact that their resonance comes from the mouth,
and not from the nasal cavities which are closed by elevation
of the soft palate. Several kinds of I can be distinguished
according to the seat of articulation, the most usual being formed
by bringing the tip and lateral edges of the tongue into contact
with the alveolar and dental arches, while the air escapes
through two lateral openings between the premolars (Fig. 107).
M i
166
PHYSIOLOGY
CHAP.
This is the so-called alveolar I used in most European languages.
Besides this there is also an apical I, which is easily formed by
applying the tip of the tongue to the hard palate, above the
alveolar border. This is the / of the English will, well, hall,
etc. It is also found in Norwegian and Polish.
r differs from / because the tip of the tongue is rapidly and
intermittently applied to the palate, which gives a vibratory
character to the laryngeal tone. The labial r (brr) is not in
written language, but is often formed by children, and is also
an interjection e.g. to express cold. In Germany coachmen use
FIG. 107. — Articulation of Za.
(Luciani and Baglioni.)
FIG. 108.— Articulation of glia.
(Luciani and Baglioni.)
it to stop their horses. Gael states that it occurs in the language
of the savages on an island near New Guinea. The most common
forms of the anterior and alveolar-palatal are formed by vibrating
the tip of the tongue against the dental and alveolar arches,
and by applying it in the apical position to the hard palate.
The velar or uvular r, formed by applying the dorsum of the
tongue to the uvular portion of the soft palate, is less vibrant,
and is known as the French r because it is characteristic of that
language. Lastly, there is a laryngeal r caused by the tremulous
closure of the glottis, with a deep, soft tone as in the English
girl, bird, or the higher and harsher gli of Arabic.
The physical nature of the semivowels has not been determined,
owing to the difficulties which their study presents. According
to Hermann and Matthias there are formants in the sounds
Ill
PHONATION AND AKTICULATION
1G7
m, n, I, which can be recognised in phonautographic curves. The
phonograms of r, according to Hensen and Winckler, exhibit
a rhythmical crescendo and decrescendo like the modemto beats of
a musical tempo.
Consonants proper are distinguished from semivowels in being
invariably composed of sounds, while the accent never falls on
them, i.e. they never act as syllabic sonants. They form two
subgroups, according as they are accompanied by distinct laryngeal
tones, or not ; the first are called sounding (or median) consonants,
FIG. 109. — Articulation of da and gia.
(Luciani and Baglioni.)
Km. 110.— Articulation of co and ga.
(Luciani and Baglioni.)
the second mutes. Both may be subdivided into occlusives or
explosives, and fricatives or spirants.
Explosive consonants are produced by the sudden opening of
the oral cavity, owing to the pressure of the expiratory air.
Their formation accordingly involves the closure of the pharyngo-
buccal cavity at a certain point, in which sense only they are
occlusive or dosing sounds. Some authors maintain that they
should be called explosive when followed by a vowel or semivowel
(as in ba, pi, de, te, bra,^>la, dro, knu), and occlusive when preceded
by a vowel or semivowel (ab, ip, ed, ot, arb, alp, ord, onk). But
this a fallacy. Every one can demonstrate that even when
preceded by vowels or semivowels, the characteristic sound of an
explosive consonant is heard, not at the closure, but at the
reopening, of the cavity which has been momentarily closed.
168
PHYSIOLOGY
CHAP.
Fricative consonants are produced by sounds of friction as
the expiratory current passes through the constricted oral cavity,
and are consequently continuous or liquid sounds like the semi-
vowels, unlike the explosives which are instantaneous.
The explosive consonants b, d, g;, g", are formed with the
glottis open, and may be preceded and accompanied by a laryngeal
tone ; in p, t, c', k, the glottis is fully closed, and the expulsion of
the air is not accompanied by vibrations of the vocal cords.
The labials & and p are always formed by the opening of both
lips. In the alveolars, </, <f, t, c' the position of the tongue varies ;
FIG. 111.— Articulation of i and en'.
(Luciani and Baglioni.)
FIG. 112. — Articulation of jet.
(Luciani and Baglioni.)
hence their sound differs more or less noticeably. The same holds
for the palatals ga and k (Figs. 109, 110).
Fricative or spirant consonants are formed when the expiratory
blast of air is driven with a certain force through a confined
passage. Unlike the explosives the fricatives are preceded, not
By the closure, but simply by the constriction of the pharyngo-
buccal cavity. They may or may not be accompanied by laryngeal
tones, i.e. may be voiced or voiceless, w, v, the French and Italian
j, are pronounced with the voice ; /, the German ch and sell, and
French ch, without the voice ; with or without, s, z and the
English tli. Grammarians term the sounding s and z lenes, and
the mute s and z fortes. But the true physiological difference is
that the former are accompanied by laryngeal sounds.
The only consonant which is necessarily voiceless is h ; it may
Ill
rHONATION AND AETICULATION
109
be tennis, due to the slight sound that accompanies the opening
of the glottis previous to the utterance of a vowel (spiritus lenis
of the Greeks, aleph of the Hebrews, hamze of the Arabs), or
t'ortis (spiritus asper, Greek; he, Arabic). The latter sound is
'absent in Italian, but exists in many languages (harp, house,
Hans}. The mute h is sometimes represented (as a historical
reminder) in Italian, French, and English, but is frequently
omitted in written language.
In pronouncing s the constriction is usually produced by
contact of the lateral edges of the tongue with the entire dental
]•'!<•. 113.— Articulation of sa. (Griitzner.) FK;. 114.— Articulation of scia. (GriitziuT.)
Impression left by the tongue stained with carmine previous to articulation.
arcade, except the small anterior median space opposite the two
incisor teeth (Fig. 113) ; the sound is due to the escape of air
through this narrow passage.
The English tk is formed by applying the tip of the tongue
above the lower incisors till it lightly touches the lower lip
(interdental articulation).
Both s and th may be pronounced without the voice (thick,
thing}, or with the voice (those, that). The mute th corresponds
to 6a and the sounding th to 8a of modern Greek.
The fricative which the Germans write sch, the French ch,
and the Italians sci, is distributed through all known languages,
and is really a simple consonant, although in a few languages
(Sanskrit, Hebrew/ Cyrillian and Glagolitic dialects of Slav) it
170 PHYSIOLOGY CHAP.
is expressed by a special sign. It is not, in fact, a series of sounds,
but a single continuous sound very similar to s, formed by con-
striction of different parts of the oral cavity. It is due to
application of the lateral edges of the tongue to the hard palate,
alveoli, molar teeth, allowing an escape of air through a median
passage between the tip of the tongue and palate, which is wider
and more posterior than in s (Figs. 113, 114).
X. The words of a language result from the different combina-
tions of the elementary sounds we have been dealing with—
vowels, semivowels, sounding and mute consonants. One or two
vowels, alone or accompanied by semivowels or consonants so as
to make a continuous phonetic unity, form the so-called syllables.
The phonetic continuity of the syllable depends on its being
pronounced in one uninterrupted breath, which is only possible
when its elements are capable of fusion or agglutination. When
the successive sounds are not capable of agglutination, so as to
be uttered in a single, continuous, expiratory effort,' a short
interruption or pause (the hiatus) is interposed between them, by
which the sound is divided into two or more syllables.
The coherence of two vowels forms a diphthong ; when they
make a single syllable, i.e. fuse together so that the voice is
not interrupted in the rapid transition from the position for the
first to that for the second vowel ; when, on the contrary, two
vowels follow without agglutinating, so that the voice is interrupted
in passing from one to the other, they do not form part of the same
syllable and do not constitute a diphthong (aid, poetry}. The
division of two normally agglutinated vowels by the interposition
of a hiatus is known as diuresis ; the fusion of two separate vowels
which form part of two successive syllables, as synaresis. Tn the
first case one of the syllables is made into twTo, in the second two
syllables are fused into one.
More frequently the syllable consists of one vowel or diphthong
and one, two, or three semivowels or consonants, and vice versa.
Two laws must be observed for the adhesion of a vowel with
semivowels and consonants : (a) Vowels readily adhere to semi-
vowels, imperfectly to explosives and fricatives; (£) Both
semivowels and consonants agglutinate perfectly with vowels to
form single syllables.
The combination of several syllables constitutes polysyllabic
words, in which the phonetic unity is interrupted once or oftener,
according as it consists of two or more syllables. The break
is produced by the discontinuity of the outgoing expiratory
blast due either to occlusion or narrowing- of the resonating
o o
cavity at some point along its course — glottis, soft palate, hard
palate, or lips. The interruption may be more or less appreci-
able according as it is more or less prolonged, and is not always
a complete silence, but may be a light aspiration — the tennis
in PHONATION AND AKTICULATION 171
h, or spirit-us lewis of Greek — which is not usually marked in
writing.
In each syllable accent and yuaiUity have to be distinguished.
" Accent " means the loudness and pitch of tone with which the
.syllable is pronounced. In syllables which consist of one or two
vowels combining with one, two, or three semivowels or consonants,
the accent falls on the sound which is uttered in the strongest
and highest voice : this is the sonant of the syllable. The rest
of the elements associated with the sonant and pronounced in a
weaker and lower voice, — whether vowels, semivowels, sounding
consonants, or dumb consonants — form the consonants.
ir»rd accent, again, must be distinguished from syllabic accent;
it falls on those syllabic sonants which are pronounced in the
loudest, highest voice. Physiologically the accent may be suit-
divided as pJton-ic and tonic according to its strength or pitch.
Practically this distinction is rarely made, because the accent
generally, depends on the higher pitch at which the syllable is
uttered.
The " quantity " of the syllables depends on their brevity or
length, i.e. the physiological duration of the expiratory breath in
which they are uttered, which varies according to the different
vowels, semivowels, and consonants. In Greek and Latin the
quantity of the syllable was regularly distinguished and used as
the base of metric poetry. Modern languages attach little weight
to the quantity — i.e. brevity or length — of the syllables, since
this is dominated by the accent, which has become the base of
modern metrical poetry. Even when imitating classical metres
we emphasise the accent, not the length of the syllables — a
splendid example of this being the work of the Italian poet,
Carducci.
The combination of syllables leads to the formation of sentences
which are divided by pauses of different length, marked in writing
by commas, semicolons, etc. The words of which they consist are
variously accentuated. There is also a sentence accent, which
falls on the words we emphasise in speaking, and sometimes
underline in writing. The pitch of the ordinary speaking voice
varies within the limits of a half-octave. In European languages
the different tones of the language colour the phrases and alter
their expression. Correct diction and accent is a special gift with
which different individuals are very variously endowed. This
may not make their speech more intelligible, but it certainly
renders it more effective and agreeable.
XI. The development of speech in children closely follows
their anatomical development and the physiological exercise of
the speech organs. They begin by vocalising, and utter high-
pitched vocal sounds, i, a, e, which constitute the cries and in-
articulate sounds of infancy. The child's first articulate utterances
172 PHYSIOLOGY CHAP.
are those that are most easily formed, viz. semivowels and labial
consonants ( pa, ba, ma, Iru, Ira, pra\ which require only a single
action of the lips that are perfectly formed from birth and capable
of function. A little later conies the formation of the alveolar
consonants (da, to) winch cannot be uttered till the jaws are well
developed and the teeth protruding. The palatals and volars are
acquired later, 1 toth because they are harder to form, and because
the development of the soft palate is completed. Ca (ka) is easier
than ga, which does not occur in primitive languages, as g was a
later modification of c. The ga sound is often replaced by children
with ta. The semivowel r is harder to pronounce than m, n, and
/. Many children and adults lisp, i.e. are unable to utter the
alveolar r, and substitute I for it.
Up to a certain point there is a parallelism between the
ontogenetic and phylogenetic development of language in the
different races. Some primitive languages are very rich in vowels ;
but after a certain point of development they employ many
consonants. Up to the present there has been no comprehensive
study of the development of primitive idioms, but it may be stated
generally that languages, like individuals, evolve until they reach a
certain point of development, after which they suffer a slow but
persistent transformation, for worse or for better.
It is well known that the dialects of savage races may undergo
such modifications in the course of a few years that they are
hardly recognisable. Writing and written language play an
important part in checking or hindering the natural tendency of
every language to transformation, but this is largely promoted
by contact between the several dialects and vernaculars, as well
as by intercourse between peoples who employ different idioms.
The great historical transformation of Latin into the modern
Romance languages may perhaps be taken as an illustration of the
above. Even before the fall of the Roman Empire it was favoured
by the predominating influences of the unlettered popular dialects
during the early part of the Middle Ages, over the fixed idiom of
the Latin Codices. The metamorphosis took place more rapidly
in France than in Italy, which was the centre of Roman civilisation.
And French literature was, for this very reason, nearly two
centuries ahead of Italian literature.
But while written literature may check the natural evolution
of a language, it can never arrest it, for its development is the
work of the people, not of the writers. This is plain from the
discrepancy between any language in the strict sense, and its
literature--*.^ between spoken and written language. The
difference is greatest in the English language, in which the written
or printed words are not so much a symbolic representation of the
different tones and sounds of which they are built up, as mere
mnemonic signs — a little plainer and more expressive than the
in PHONATION AND AETICULATION 173
hieroglyphics of the ancients. Among the different Teutonic
idioms the German language is the most faithfully represented in
its writing.
Of the Neo-Latin languages, French has certainly retained its
archaic form in writing more closely than the others ; because the
evolutionary transformations of the language spoken by the people
were not adopted in the written form, owing to the prejudices of
the grammarians. In Italian and Spanish, on the contrary, the
written language is a more faithful transcript of the pronunciation.
BIBLIOGRAPHY
For this subject the student may consult articles by JON. MULLER, LONGET,
GRUTZNER (iu Hermann's Handbuch), BRUCKE, GAD and HEYMAN.S, SCHAEFKK.
The principal Monographs and Memoirs are :—
LISKOVIUS. Phys. d. Menschl. Stimnie, 1846.
HARLESS. Art. Stimnie i. d. Wagners's Handwort. d. Physiol., 1853.
LEPSIUS. Das allgemeine liuguistische Alphabet. Berlin, 1855.
DONPER.S. Arch. f. d. holland. Beitrage f. Nat. u. Heilk., 1857.
CZERMAK. Der Kehlkopfspiegel, etc. Leipzig, 1860.
THAI*SING. Das natiirliche Lautsystem. Leipzig, 1863.
MKRKEL. Anat. u. Physiol. d. menschl. Stimni- und Sprachorgans, 1856. Antro-
pophonik. Leipzig, 1857. Physiol. d. menschl. Sprache. Leipzig, 1866.
FOURNIE. Physiologic de la voix et de la parole. Paris, 1866.
RUMPELT. Das natiirliche System d. Sprachlante. Halle, 1869.
KONIG. Annal. d. Physik, vii. , 1876; cxxxxvi. , 1872.
SIEVEKS. Grundziige der Lautphysiologie. Leipzig, 1879. (Now in its 5th ed.)
BUUECKE. Grundziige d. Physiol. u. Systematik d. Sprachlaute. Wien, 1836.
(Now in its 5th ed.)
GAVARRET. Phenomenes physiques de la phonation et de 1'audition. Paris, 1877.
HELMHOLTZ. Die Lehre von den Tonempfindungen. Braunschweig, 1877.
(Tr. by Ellis from 3rd ed., 1875.)
AUERBACH. Ann. d. Physik, iii., 1878.
GARCIA. Mem. sur la voix humaiue, 1855-1861-1878.
SCHNEEBELI. Arch, des sc. phy. et nat. i., 1879.
OERTEL. Ueber d. Median, des Brust- und Falsett-Register. Stuttgart, 1882.
BELL, A. M. Sounds and their Relations. London, 1882.
TECHMER. Phouetik. Leipzig, 1880. International Zeitschr. f. allgemeine
Sprachwissensch. i., 1884.
SWEET. A Primer of Phonetics. Oxford, 1890.
SEMON. Brit. Med. Journ. London, 1886.
FRENCH. Verhamll. d. intern. Congr. Berlin, 1890.
STORN, J. Englische Philologie. Leipzig, 1892. (Vol. i. contains a critical review
of all the important works on phonetics published between 1840 and 1880.)
WYLLIE. Disorders of Speech. 1894.
PIPPING. Zeitschr. f. Biol., xxvii., xxxi., 1890-94.
BREYMANN, H. Die phon. Literatur von 1876-1895. Leipzig, 1897.
HERMANN. Arch. f. d. ges. Physiol. Ixi., 1895 ; Ixxxiii., 1900.
HALLOCK. Am. Ann. Photogr. ' 1896.
FLEEMING-JENKIN and EWING. Trans. Roy. Soc. Edin. vol. xxxviii., 1897.
HENSEN. Arch. ital. de biol., 1901.
ROUSSELOT. Principes de pnonetique experimental e. Paris, 1897-1901. Les
Modifications phonetiques du langage. Paris, 1891.
G. ASCOLI. Archivio glottologico italiano, vol. i., 1873.
SCRIPTURE, E. W. Elements of Experimental Phonetics. New York and London,
1902.
JESPERSEN, 0. Lehrbuch d. Phon. Leipzig, 1904.
174 PHYSIOLOGY CHAP, in
SCRIPTURE, E. W. Speech Curves. Washington, 1906.
PANCONCELLI-CALZIA. Bibliographia phonetica. (Published regularly since 1906
in Medizinisch-piidagogische Monatschrift f. d. Sprachheilkunde. (References
to recent works on phonetics).
PASSY, P. Expose des principes de 1'association phon. internationale. Leipzig,
1908.
GUTZMANN, H. Phys. d. Stimme u. Sprache. Brunswick, 1909.
LUCIANI, L. Par la ritbrnia ortografica (Estr. Atti d. Soc. it. per il progr. delle
Scienze— iv. Riunione. Naples, ottobre 1910.
LUCIANI, L. Di una ril'orma ortografica basata sulla fonetica fisiologica (Estr.
Rivista pedagogica, a. iv., v. i., 1910).
GOIDANICH, P. C. Rivista pedagogica, 3rd year, vol. ii. Modena, 1910. Archivio
glottologico italiano, vol. xvii., 1910. Miscellanea di studi in onore di Attilio
Hortis. Trieste, 1910.
POIROT, J. Die Phonetik (Hb. d. phys. Methodik di R. TIEGERSTEDT, iii. Bd. vi.
Abt.). Leipzig, 1911.
Recent English Literature : —
MOTT, F. AV. The Brain and the Voice in Speech and Song. London and New
York, 1910.
AIKIN, \V. A. The Voice — An Introduction to Practical Phonology. London,
1910.
CHAPTER IV
GENERAL PHYSIOLOGY OF THE NERVOUS SYSTEM
CONTENTS. — 1. Structural elements of the nervous system. Theory of in-
dependent neurones, or continuity of neuro-fibrils. 2. Conditions, laws and
phenomena of conduction in nerve. 3. Rate of conductivity : diphasic character
of the impulse arousing it. 4. Metabolism of nerve ; electromotive phenomena
during rest and excitation : demarcation current, action current. 5. Excitation
of nerve. Natural stimuli and artificial (chemical, mechanical, electrical) stimuli.
6. Factors in life and death of nerve : conditions of excitability. 7. Polar effects
of constant current ( electro tonus) : correlative changes in excitability and con-
ductivity. 8. Excitatory action of electrical currents. Laws of excitation.
9. Theories as to origin of nerve activity. 10. General functions of nerve-centres.
Ganglion cells and central fibrillary network. Bibliography.
THE Nervous System, which is the real centre of the functions of
animal life, controls the activities of the organs of involuntary—
or vegetative — life, as well as those of the muscles. By means of
the sensory mechanisms it correlates the several organs among
themselves, and brings the organism as a whole into relation with
the external world, while it is able by means of the motor
mechanisms to vary these relations and adapt them to change of
circumstances.
In order that it may fulfil these important functions, the
nervous system is built up of morphological elements which
establish a functional link between the different organs, inde-
pendent of their juxtaposition or distance, and control the
circulation of the tissue fluids, so that when a given change takes
place in one part, other phenomena necessarily ensue in other
remote parts, e.g. in the skin and the muscles, the mucous
membrane and the glands, etc. It is the nervous system that
presides over those complex relations between distant organs
which the ancients termed "sympathies." It represents the
physiological unity, the reciprocal dependence of parts, on which
the psychological unity, expressed in the phenomena of the ego or
consciousness, is founded.
The most elementary organisms, while they possess no differ-
entiated nervous and muscular systems, nevertheless exhibit
essential animal characteristics of sensibility and motility, albeit
175
176 PHYSIOLOGY CHAP.
in a rudimentary and ill-defined form : to explain this fact we
must assume a common protoplasmic basis for both these
elementally functions and those evolved in the more perfect
organisms 'by gradual morphological and functional differentiation
intfc %r?e**nervous and muscular systems.
The organs of the nervous system, of which the general
physiology will be considered in this chapter, represent the highest
grade of morphological and functional differentiation, both in the
ontogenetic development of the individual and in the phylogenetic
development of the lowest forms of the animal kingdom.
I. The nervous system in man and other vertebrates consists
of: (a) a compact mass — the cerebrospinal axis; (&) nerves which
are given off from this axis — the cerebral and spinal nerves — and
distributed, by successive division, into smaller and smaller bundles
and branches, to nearly all the organs and tissues of the body ;
(c) a vast number of ganglia or nervous nodes, intercalated along
the course of the nerves at greater or less distance from the cerebro-
spinal axis, many of which form two lateral chains, and constitute
the splanchnic or great sympathetic system.
To the naked eye the nervous system consists of two dissimilar
substances — the white matter and the f/rey matter. Under the
microscope both are seen to be made up of fibres and nerve-
cells, the fibres predominating in the white matter, the cells in
the grey.
Apart from their minute histological structure, the nerve-cells
of the cerebrospinal axis and ganglia have long been regarded as
the central, and the nerve-fibres as the peripheral, parts of the
I system. The cells more particularly serve the storage, elaboration,
I transformation, and development of the specific energies of the
system ; the fibres more especially conduct and transmit these
energies from the periphery to the centre (centripetal or afferent
nerves), and from the centre to the periphery (centrifugal or efferent
nerves). The inclination to differentiate between the physiological
functions of the ganglion cells and of the nerve fibres, which are
filiform processes of the cells, became more definite after the
discovery of the telegraph by Morse (1837), which to many minds
suggested a parallel between the functions of the nervous system
and the telegraphic installation of a State. The cells were com-
pared to the telegraph apparatus, the fibres to the conducting
wires, the cerebrospinal axis to the great central telegraph station,
the conglomerated ganglia of the sympathetic system to the inter-
mediate exchanges, the peripheral ganglia to the local offices of
country towns and villages.
But despite the apparent analogy between the two systems,
which both consist of distant apparatus brought into direct relation
by conducting wires, there are huge internal differences in the
nature and function of the elements of which the two systems,
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 177
respectively, are composed. The physiological data we are about
to discuss will emphasise these differences.
In reviewing our present knowledge of the minute structure of
the histological elements of the nervous system, it should be noted
that the data are all comparatively recent. Notwithstanding the
number and ability of the investigators and the delicacy and
variety of the methods employed, the facts are not yet sufficiently
clear and unequivocal to admit of the construction of any universal
and authoritative morphological theory.
The first exact account of the existence of specific nerve-cells
dates from 1833, when Ehreuberg described the cells of the spinal
ganglia of the frog. In 1838 Eemak first discovered in the
sympathetic of vertebrates that the nerve-fibres are a prolongation
of the processes of the cells, which was confirmed in 1842 by
Helmholtz and Hannover on invertebrates. Deiters was the first
to demonstrate, in a monograph published after his death by
Schultze (1863), that two different kinds of processes can be
distinguished in the central nerve-cells — nerve-fibres proper, and
protoplasmic processes. He proved the continuity of the former
with the axis-cylinders of medullated nerve-fibres, but left the
destination and physiological function of the latter undetermined.
Gerlach in 1871, by the gold chloride method, demonstrated
the existence in the grey matter of the cerebrospinal axis of a
diffuse fibrillary network, which he interpreted as the result of
an anastomosis or concrescence of the finest ramifications of the
protoplasmic processes of the ganglion cells. To this he ascribed
the important function of bringing the ganglion cells of the central
mass of the nervous system into direct interrelation.
In 1873 Golgi discovered his method of staining nerve-cells and
fibres black with salts of silver which led to a great advance in our
knowledge of the minute structure of the nervous system. He
showed that at a certain distance from the cells the nerve pro-
longations or axons give off collateral rami which branch from the
trunk, mostly at a right angle. Like Gerlach he admitted the
existence of a diffuse network of nerve-fibrils which conduct the
excitation ; but denied that it was formed by the dendritic
ramifications of the protoplasmic processes, which he held to be
simple nutrient paths from the cell body, with free endings.
Golgi maintained that the ganglion cells were united by a fibrillary
network formed of the finest ramifications of the axis-cylinders.
Subsequent researches made by Eamon y Cajal after 1888, with
Golgi's methods, led this author to deny the existence of any such
diffuse fibrillary network : Cajal concluded that both the dendrites
and the axons terminate free ; and that each ganglion cell, with
the whole of its protoplasmic and axis-cylinder processes, represents
an elementary organism in itself, connected with the others not by
anastomosis nor continuity, but by simple contact or contiguity.
VOL. 1IT N
-13
mm
, j
R
B
II
c
FIG. 115. — A, Bipolar nei ve-cell with poles prolonged into medullated nerve-fibres. (Rey and
Retzius.) The cut in' cell is invested with the neurilemma. li R, nodes of Ranvier.
B, Portions of two nerve-tibres stained with osinic acid (from a yonm; rabbit); diagrammatic,
425 diameters. (Schafer.) R R, nodes of Ranvie.r, with axis : cylinder passing through ;
a, neurilemma ; c, nucleus and ]irotoplasm lying between the neuiilemma and the medullary
sheath. C, Mednllated nei vr-liln i- treated with osmic acid. (Rey and Retzius.) E, node of
Ranvier ; K, nucleus. The myelin of the medullary sheath is incompletely interrupted so as
to form conico-cylindrical segments.
CH.IV GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 179
Cajal's observations found general support and were repeated
and confirmed by Ko Hiker, Lenhossok, and van Gehuchten with
Golgi's method ; by Eetzius, Biedermanu, and others with
Ehrlich's method (intra vitn-m, staining with methylene blue).
Waldeyer gave the name of neurone (from vtvpov, point of
contact of many nerve threads) to the elementary units of
which the nervous system is built up, which term found great
favour with the neurologists, and contributed not a little to
Kl'.. 11(1. — Phylogenetic and onto^enetic development of neurones with loiix axons from pyramidal
cells of cerebral cortex. (Ramon y Cajal.) The upper series represents the phylogenetic
development of these cells : .4, in fro;; ; Jl, newt ; (.', rat ; D, man. The lower series shows the
ontogenetic development of the neuroblasts of those cells in live successive phases, a, b. c, "'. e.
popularise the " neurone theory " in the medical world. The
protoplasmic processes were termed dendrites, the nerve process
neurite, axon, or axis-cylinder. The dendrites differ from the
axons in various structural characters, some of which had been
described by Deiters, others were discovered by Golgi with his
method. In many neurones the dendrites exhibit minute lateral
processes — spines or gemmules — along their course which are
never seen on the axons.
Some nerve-cells are wholly destitute of dendrites, e.g. the
typical cells of spinal ganglia and the corresponding ganglia of
the cranial nerves. On the other hand some nerve-cells have no
N 1
180
PHYSIOLOGY
CHAP.
\
true axis-cylinder process, e.g. those of the stratum granulosum of
the olfactory bulb. The cells of the spinal ganglia of Teleosteans and
the cells of the cochlear ganglion are bipolar or bineural, i.e. have
two axons (Fig. 115, A), and in the molecular layer of the cerebral
cortex, according to Ramon y Cajal, Eetzius, and others, there
are nerve -cells with two or three axons. Veratti, however,
contests this statement, and gives a totally different interpreta-
tion to the data on
which it
According
is based,
to Gokri
o o
the cells of the cere-
bral cortex which give
origin to the so-called
pyramidal tracts, and
still more those of the
ventral horns of the
spinal cord, have long
axis-cylinder processes
which give off col-
lateral rami, while
they preserve their
individuality for a
long distance ; the
latter are continued
in the ventral root-
fibres of the spinal
nerves (Fig. 116).
The cells of the dorsal
horns of the cord, on
the contrary, and
many cells in the grey
matter of the large
FIG. 117.— Large ceUs with short axons. Golgi s second type, 6
found in the nuclear layer of the cat's cerebellum, high Cerebral Centres, have
magnification. (Golgi.) In order to distinguish the proto- •, , • -i • •>
plasmie processes from the nerve processes or axis-cylinders, SllOr b aXIS - Cylinders,
the former are printed in black, the latter with their rami- ,,7 V, i r- l-i v o T> o o f a A 1 \T
tications in red. 11V
divide and subdivide,
and soon lose their individuality (Fig. 117). It is, however, very
doubtful whether the presumably different functions of these
various forms of neurones are connected with the morphological
differences indicated by the appearance of their axis-cylinders.
The neurone theory, which regards the elementary components
of the nervous system as morphologically distinct, is not based
on any conclusive evidence. Even after the observations of
Ramon y Cajal and his numerous adherents, Golgi and his pupils
still insisted on the theory of a diffuse; nervous network, formed
of the collateral rami given off from the axons in the vicinity
of the ganglion cells. Golgi demonstrated this diffuse nervous
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 181
network more particularly in certain parts of the central nervous
system, e.g. the fascia dentata of the hippocampus (Fig. 118)
and the cerebellar cortex (Fig. 119).
The neurone theory, on the other hand, harmonises perfectly
with the embryological observations of His (1887), who believed
Fin. IIS. —Fascia dentata of pes hippocampi major. (Golgi.) Between the processes coming from
the upper layer of nerve-cells and the lower of nerve-fibres there is an intervening zona reticulari.s
composed of nerve-libres which interlace repeatedly, so that they lose their individuality and
constitute what Golgi calls the diffuse nerve network.
that he had demonstrated the genesis of the nerve elements from
the special germinal cells of ectodermal origin, which are inter-
posed between the epithelial cells of which the walls of the
primitive neural tube are composed. A-polar and rounded in
an early stage, they subsequently become piriform ; next they
send out a nerve process and become uni-polar ; finally the
dendrites appear also (Fig. 116, a, b, c, d, e]. During their growth
N 2
182
PHYSIOLOGY
CHAP.
the neuroblasts gradually move away from the wall of the neural
canal towards the exterior. Many of them remain in the central
grey matter ; others wander out to form the cerebrospinal ganglia,
sympathetic ganglia, etc.
But this theory of His, in so far as it conceives the nerves
to be only appendages of the ganglion cells, is contradicted by
the observations of Balfour, Beard, Dohrn, Kupfer, and Eaffaele
FIG. IIP. — Cerebellar cortex showing relations between the small cells of the molecular layer and
the body of Pnrkinje's cells. (Golgi.) The nerve-fibres descending from the small cells of the
molecular layer partially embrace the large body of the Purkinje cells, partially pass between
these, and then subdivide repeatedly belowjthem to form another diffuse network
on fishes, and the more recent work of Bethe, Paladiuo, Fragnito,
and Capobianco on chick embryos. According to these observers
the axis - cylinders of the peripheral nerves and of the white
matter of the central organs are not (from the histogenetical
point of view) composed of prolongations of the axons and
dendrites of the ganglion cells, but are derived from the fusion
of many cells arranged in series, and only contract relations with
the ganglion cells at a later time. The problem is still unsolved,
since some authors (Harrison in the first place) confirm the
view of His, while others take the polygenetic theory as proven.
iv GENERAL PHYSIOLOGY OF NEEVOUS SYSTEM 183
Whatever the value of these conflicting statements, and how-
ever certain it is that during their histogenetic development
the constituent elements of the nervous system are morphologi-
cally distinct and independent, it is far from proved that in
fully developed tissues the so-called " neurone " represents a
true morphological unit, and is not a fusion of many elements,
or syncytiutn ; nor that these neurones do not enter into close
relation by direct continuity of their protoplasmic substance ;
nor, lastly, is the idea of a diffuse fibrillary network which, both
in the central grey matter and at the periphery, knits the several
neurones into a single unitary system, comparable with the
vascular system, by any means excluded.
This modern view of the minute structure of the nervous
system is founded on the work of Apathy,- Bethe, Nissl, and
others, who, by new methods of staining, have brought out new
facts which are in more or less open contradiction with the
neurone theory. We must confine ourselves to a brief survey of
the principal data supplied by these researches.
While the method used by Golgi and his numerous followers
in the study of the minute structure of the nervous system has
added greatly to our positive knowledge in this difficult subject,
it is by no means the best adapted to show up the microscopic
structure of the nerve-cells and processes. With too intense
impregnation with silver, both cells and processes are stained
uniformly black. In order that this method may bring out the
fine structure of the body of the nerve -cell, as in the figures
obtained by Golgi, it is necessary to make repeated experiments,
for which no general rules can be given.
Again, there is grave reason to suspect, on the strength of the
facts established by Apathy for the nervous system of the leech,
that the silver method which only shows up certain elements of the
system, leaving the rest unstained and therefore undifferentiated, is
inadequate for the demonstration of the finest ramifications of the
dendrites and axis-cylinders. We have seen that Golgi himself
pointed out that the free endings discovered by Ramon y Cajal,
upon which the whole neurone theory is based, are not indisput-
able, but result from an inherent defect in the method of staining.
In 1871, in describing the ganglion cells of the spinal cord,
Max Schultze recognised the fibrillary nature of their protoplasm
and of the protoplasmic and nerve processes. Both in fresh
preparations and in those treated with osmic acid, he observed
distinct fibrils which run in various directions through the cell
body, giving it the appearance of a network or reticulum, and
are in direct connection with the elementary fibrils of which both
the axons and the dendrites are composed. He further assumed
the existence of a finely granular substance, which fills the
inter fibrillary spaces.
184
PHYSIOLOGY
CHAP.
This point of view was adopted by Erik Miiller, Boll, Schwalbe,
and Eanvier, and was subsequently carried further by Flemming
(1895), who on staining with hamiatoxylin described independent
fibrils in the dendrites which were continued into the cell body,
though he could not trace them distinctly into the centre of the
cell, where they seemed to anastomose to form a network.
The theory of the fibrillary nature of the protoplasm of the
nerve-cells was disputed by v. Lenhossek, but it was adopted and
defended by Dogiel, Donaggio, Becker, Marinesco, Held, and
Lugaro. In 1896, Donaggio, with a special method of elective
FIG. 120. — Peripheral network of nerve-cells from flop's spinal conl. (Dona.ugio.)
staining, observed and described a fibrillary network that per-
vades both the interior and the periphery of the nerve-cells, and
in which the fibrils from the surrounding tissue terminate
(Fig- 120).
Lugaro (1897) convinced himself, with the same haeniatoxylin
method as Flemniing employed, of the fibrillary structure of the
spinal ganglion cells of dogs poisoned with arsenic, which totally
destroyed the chromatic substance at the periphery of the cell
body. The fibrils, according to Lugaro, anastomose among them-
selves, forming a very delicate reticulum in certain types of cells,
a coarser network in others. He made analogous observations
upon the cells of the nerve-centres of animals subjected to ex-
perimental hyperthermia.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 185
Levi, Luo-aro's collaborator, obtained similar results from the
O
ganglion cells of frogs during hibernation, in which state the
chromatic subtance is very scanty, so that the achromatic fibrillary
part is more conspicuous.
The existence of fibrils in the nerve-cell and its processes may
be regarded as fully established by Apathy's work on the nervous
system of the Anellidac (1897). He demonstrated definite fibrils
by a special method of staining the ganglion cells with gold
chloride. As shown by Fig. 121, these fibrils penetrate from the
dendrites into the cell body, where they form a wide -meshed
network, and then collect into a single bundle, and leave by the
axis-cylinder. The fibrillary network (Apathy) assumes different
FIG. 121. — <i;t]r_li'>n cell of ventral cord of Lmnliriciit, showing an endoeellular fibrillary network,
which is continuous with the afferent fibrils of the dendrites, and with one larger, effVii-nt
fibre of the axon. (Apathy.)
forms according to the nature of the ganglion cells. The small
fibres brought out by the gold stain are shown to be bundles of
very delicate elementary fibrils, which escape observation owing
to their size and the inadequacy of the staining methods. These
are the conducting elements proper of the nervous system.
Any one who has studied the preparations obtained with
Apathy's method must admit that they exhibit astonishingly
clear details of structure, which may be of fundamental import-
ance to physiology. At the same time it must be remembered
that Apathy's positive results relate solely to the nerve-cells of
the lower animals (Hirudo and Lumbricus), and that in spite
of prolonged experiments, nothing exactly corresponding has so
far been obtained in vertebrates.
Bethe, in a series of interesting observations (1897-1890),
endeavoured by other special methods of elective staining of the
186
PHYSIOLOGY
CHAP.
fibrils to extend to vertebrates the morphological facts and con
ceptions which Apathy developed for Anellidae. According to
Bethe the fibrils in the ganglion cells remain independent,
without anastomosing among themselves to form a network,
except in the cells of the spinal ganglia, in which he found the
network to consist of coarser fibrils, with larger meshes, than had
been observed by other methods. Bethe's fibrils pass in every
direction from one process to another, and between different
branches of the dendrites.
Golgi also investigated the minute structure of the nerve-cell
JSlPii Jim
^
~
Fie. 1:22. — Kibrillary ut-twoik of a fell of the do^'s spinal curd, obtained by Dona.u.uio with
his spi'dal mi-thud uf fli-cth>- staining.
after his classical work on the general structure of the nervous
system referred to above. His own publications and those of
his pupil Veratti (1898-1900) demonstrated for almost every
form of nerve-cell : («) an endocellular reticulum ; (&) a fibrillary
structure of the peripheral zone of the cell; (c) a kind of peri-
cellular network.
The nature and function of the endocellular reticulum are
still undetermined. As between the two hypotheses now in the
field, according to which it is either a nervous network (Apathy)
or a system of nutritive canaliculi (Holmgren), Golgi does not
attempt to decide.
The nervous character of the fibrils which constitute the
fibrillary structure of the peripheral zone of the ganglion cell
iv GENERAL PHYSIOLOGY OF NERYOUS SYSTEM 187
:i
3
o
p
is proved by their continuity with the axis-cylinder
process. Golgi has hitherto failed to discover any
relation between these peripheral fibrils and the
endocellular reticulum, which appears to be an
argument in favour of Holmgren's hypothesis,
although Golgi's reluctance to accept this inter-
pretation is easily understood.
The pericellular network described by Golgi
for different cells of the cerebellum, cerebrum, and
spinal cord consists, in his opinion, of neuro-keratiu,
and he believes its function to be one of insulation,
as he considers it entirely different to and distinct
from the diffuse nervous network described above.
This fibrillary network on the surface of the
nerve -cells is admirably shown up by Bethe's
method, and probably corresponds with the peri-
pheral network observed by Donaggio and by Cajal
in 1896.
Donaggio obtained excellent preparations of
vertebrate nerve-cells by his special method. As
seen in Fig. 122, the cells are not only penetrated
at the periphery by longitudinal fibrils which pre-
serve their individuality without anastomosing, as
stated by Bethe, but in addition a great number of
fibrils can be seen which are directed to the centre
of the cell, and there divide minutely to form a
dense network which is not stained by Bethe's and
Golgi's methods. The fibrillary network
nected on the one side with the
fibrils that penetrate from the
dendrites, on the other with
the fibrils that form the axis-
cylinder.
Donaggio's more recent pre-
parations (1904) show still more
plainly that the fibrils of which
the axis - cylinder is composed
are derived directly from the
endocellular fibrillary network
(Fig. 123). The mode of origin
varies according to two cellular
types, indicated by Donaggio.
On tracing out the course of
a sensory fibre, Apathy found
that it breaks up within the
central nervous system into an
elementary fibrillary network (JElementargitter), which suggests
is con-
I!*'"''
188 PHYSIOLOGY CHAP.
the diffuse nervous network of Gerlach and Golgi, inasmuch as
it is continuous with the fibrils that enter from the periphery,
and those which leave in the axis of the single process of the
nerve-cells of Hirudo. The filaments of this network are therefore
in direct continuity with the sensory or motor fibrils that enter and
leave the ganglion cells, and which form the intracellular fibrillary
network referred to above. All the ganglion cells are thus directly
connected among themselves by the continuity of the fibrils, which,
according to Apathy, are the essential* elements of nerve con-
ductivity. At the periphery of the system again, both in the
epithelial cells and in the sensory cells and muscles, the fibres
never exhibit free endings but anastomose among themselves to
form a network, in the same way as the arteries and veins form a
single continuous system by means of the capillary network.
Bethe confirmed Apathy's results in the most essential points,
for vertebrates as well as for invertebrates, by another method, viz.
elective staining of the fibrils. He finds that very different re-
lations prevail in different classes of animals between the ganglion
cells and the fibrils. In Arthropoda the extracellular fibrillary
network is well developed, while comparatively few h'brils enter or
leave the ganglion cells to form an intracellular network. In
vertebrates, on the other hand, most of the fibrils pass through the
cell, without forming a network within it ; on the contrary an
extracellular network is formed by the anastomosing of the fibrils
that surround the cell.
This last statement of Bethe's is contradicted, as we have seen,
by the most recent work of Golgi, Donaggio, and Semi Meyer,
which shows that the methods employed by Bethe bring out
only the coarser fibrils, leaving the more delicate intra- and peri-
cellular fibrils unstained. Bethe, on the strength of his own
observations, and of an experimental argument which we shall
examine below, reduces the importance of the ganglion cells, and
holds them to be mere stations for the passage and reinforcement
of the nerve current, while the central activity of the system is
developed outside the cell in the intercellular elementary network
of the grey matter ; Donaggio, on the contrary, holds that the
cell probably represents the true centre for the reception of the
excitatory impulse and for its synthesis and transformation.
As regards the theory of the unitary structure of the nervous
system of vertebrates, Held supports Bethe in essentials, on the
strength of his own observations ; Golgi, Veratti, Donaggio main-
tain an absolute reserve ; Semi Meyer and Lugaro, while they
admit the importance of Bethe's observations, deny that these prove
the applicability to vertebrates of Apathy's results for inverte-
brates, so as to overthrow the neurone theory, according to which
the relation of the separate elements of the system is merely one
of contact. Lugaro admits as a possibility, in regard to the question
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 189
of inter-neuronal anastomosis, that the nature of the connection
between the elements of the system may have developed in two
opposite directions in the course of phylogenetic evolution. He
accepts the theory of Apathy for invertebrates, but maintains that
of Ramon y Cajal for vertebrates, so long as the continuity of the
fibrils which compose the central and peripheral elementary net-
work is not positively demonstrated.
The most emphatic and certainly one of the most reliable
supporters of the theory of Apathy and Bethe, for both in-
FIG. 124. — Two cells from ventral horn of human spinal cord. (Nissl's method.) The chromatic
sul .stance is collected into small masses, which give a speckled appearance to the cytoplasm.
Each cell, besides the nucleus and nucleolus, contains a distinct mass of stainable granules.
vertebrates and vertebrates, is Nissl, although his own work does
not refer specially to the fibrillary structure of the nervous
system. In 1893 he discovered the existence in many ganglion
cells of peculiar granules which stain with basic aniline dyes,
particularly with rnethylene blue and toluidine blue. These—
which are now generally referred to as Nissl's granules or chromato-
phile granules — are present in small masses throughout the body
of the cell and in the larger dendrites (Fig. 124).
Nissl holds that since the fibrillary nature of the achromatic
part of the ganglion cell has been established, the theory of the
nerve unit (neurone*) is no longer tenable. He concludes, on the
strength of the researches of Apathy, Bethe, and Held, which
190
PHYSIOLOGY
CHAP.
demonstrated the fusion of the axis -cylinder fibrils into an
intracellular elementary network, that the nervous system is
constructed of ganglion cells and of a fibrillary nerve substance,
the latter being a specifically differentiated cell protoplasm,
present in the cells as fibrils, and outside them as grey matter,
which last apparently consists of a close and very delicate
network of elementary fibrils. So that Nissl, like Bethe, considers
the grey matter to be the most important constituent of the
nervous system.
Another method, which brings out the fibrillary character of
the nerve-cells, is that discovered by Ramon y Cajal ; it depends
on the reduction of silver nitrate, and is known as the photo-
graphic method. According to Golgi the results obtained by
it are of the utmost importance and are easy of demonstration.
FIG. 125. — Tin cr nri \v-cells and processes showing presence and course of neuro-tibrils.
Rtimon y Cajal's photographic method.
Cajal's method (Fig. 125) shows up every detail, so that the
course of the fibrils can be followed both within the cell body
and in the processes. Among its other advantages is the fact
that, unlike any that preceded it, it brings out the fibrillary
structure of the nerve elements during their earliest development.
Jaederholm, nevertheless, remarks with regard to the signifi-
cance and theoretical value of these histological observations :
" In my opinion the reticular formations within the cells must
be regarded as artificial products due to agglutination. Such a
reticular formation may be simulated, because the cytoplasm,
coagulated in the form of a network, stains along with the
fibrils ; this happens most frequently with Donaggio's method ;
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 191
less often with that of Cajal, more rarely still with those of
Bethe and of Bielschowsky."
It is curious and instructive to note that while for Ramon
y Cajal (1908) the results obtained by his method and its
modifications afford a positive proof of the neurone theory — since
he has never been able to convince himself of the existence of
anastomosing intercellular fibrils — for Golgi (1910) none of the
data adduced in regard to the anatomical structure of the nervous
system offer a definite proof either of the theory of independent
cell-units (neurones), or of the unitary fibrillary theory.
Nevertheless, from the present state of our knowledge, Golgi
rejects the view according to which the nerve-cell is deposed,
and the chief functional value attributed to the fibrils. " I
should feel as though I were breaking faith if I faltered in
my firm conviction that the nerve-cells are the central organs
of the specific psychical and sensory activities which we ascribe to
the nervous system, provided we admit that they too come under
the concept that is valid for the whole of the cell theory, viz.
that the nerve-cells, while endowed with a certain autonomy,
are more or less dependent on their anatomical and functional
inter-relations. It is hardly necessary to point out that this
statement does not entirely exclude the participation in psychical
and sensory actions of all the other factors that enter into the
complex organisation of the nervous system.
" In regard to the functional mechanism of the nerve elements,
far from being able to accept the idea of the independence
implied in the concept of the neurone, I can but once more state
my conviction that the nerve-cells exhibit collective activity,
in the sense that larger or smaller groups of them exert a
collective action upon the peripheral organs, through bundles of
fibres and through the diffuse nervous network. This concept of
course includes that of the analogous opposite action in regard
to sensory functions.
" However much my position may conflict with the view of
separate anatomical units, I cannot renounce the idea of a
unitary action of the nervous system, nor feel disturbed if this
brings me back to the earlier conception of the mode in which
the nervous system functions."
Golgi's views on the functional activity of the central nervous
system, which are based on anatomical investigations, and parti-
cularly on the existence of a diffuse nervous network, are, how-
ever, opposed to the best-established facts of the physiology of the
sense organs. They are more particularly at variance with the
authentic and easily demonstrated observations of isolated con-
duction and perception of tactile sensations at various points
of the skin, and of elementary retinal sensations, which we
shall discuss in treating of the physiology of these sense organs.
192 PHYSIOLOGY CHAP.
In 1885 Golgi wrote at the beginning of his celebrated mono-
graph : " As regards the central organs of the nervous system,
the main task of modern anatomy must be to answer the
most pressing of the problems propounded by physiology." The
neurone theory, while it harmonises with the cell theory, un-
doubtedly corresponds best with the postulates of physiology,
although it is far from solving them all adequately.
Whatever the final solution of this important controversy
as to the structure and mode of activity of the central and
peripheral nervous systems, it must be admitted that the wealth
of physiological facts that have accumulated in this important
field have developed quite independently of the prevailing theories
of their exact constitution. If the contents of the present
chapter are considered without prejudice — and we recommend
them more particularly to the attention of histologists, it must
be admitted that the physiology of the nervous system is far
in advance of its anatomy.
II. In discussing the general physiology of the skeletal
muscles we saw that they are normally thrown into activity
by the agency of their nerves alone ; when these are cut, all
movement instantly ceases. Nerves are no less excitable than
muscles ; but while in muscle active reaction to stimuli, i.e.
"excitation," is apparent as contraction or relaxation, the active
response of the nerve is not visible, but consists in the simple
transmission or conduction of the excitation from the point
stimulated to the end-organ. The excitability of nerve is therefore
manifested in its conductivity, i.e. its capacity for transmitting
the effect of local stimulation at one point along its entire
length. The excitatory impulse in muscle is also, as we know,
propagated along the muscle fibres by physiological conduction,
but conductivity assumes a special development in the nerve,
and may be considered as its specific function, depending on
the particular differentiation and constitution of its protoplasm.
Nerve conduction consists not in the propagation of fluid
or gaseous materials, as was formerly supposed, but in the
transmission of excitation, that is, of the active state of the nerve
substance, the conditions, laws, and characteristics of which we
must now investigate.
The fundamental condition of conductivity in a nerve-fibre
is its anatomical continuity and integrity. If after dividing a
mixed nerve the two ends are brought into perfect contact, we
obtain physical continuity, but not the anatomical continuity
which is imperative for conduction ; stimuli applied above the
section are not transmitted in an efferent direction to the muscles,
nor those sent in below in an afferent direction to the centres.
An effect identical with that of section is produced by crushing,
cauterisation, scalding, and by the action of certain poisons,
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 193
n
I
localised to one point of the nerve. Lastly, as was known to
the ancients, the simple tying of a nerve prevents physiological
conduction along its fibres.
Fontana (1797) was the first who observed that the gradual
compression of a nerve may abolish its conductivity without any
concomitant excitatory phenomena. But the subsequent experi-
ments of E. H. Weber, Schiff, and others, threw doubt upon his
conclusions. They found that the paralysis due to compression of
the nerve is preceded by a
state of increased excita-
bility of the nerve and
motor phenomena in the
muscle. The subject, which
is important to clinical
medicine, was methodically
investigated by Liideritz
(1881), Zederbaum (1883),
and Efron (1886), who con-
firmed the observations of
Schiff. They saw that when
the compression of the nerve
has not been too severe, nor
too prolonged, its conduc-
tivity may be gradually re-
established. According to
Liideritz, gradual compres-
sion abolishes conductivity
first in motor and later in
sensory fibres ; but this
observation was contra-
dicted by Zederbaum and
Efron. In their experi-
ments on the nerves of
amphibia and of mammals,
these authors noted that
a pressure of some hundred
grammes is always required before conductivity is abolished.
These experiments were resumed by Ducceschi (1900) in
Ewald's laboratory by another method, i.e. compression of a very
limited area of the nerve by means of a silk thread (about 0'3
mm. thick) ; this is passed round the nerve as it lies upon a
metal plate through two small holes made in the latter, so that it
can be gradually drawn down by a weight (Fig. 126).
By means of this little apparatus Ducceschi succeeded in
diminishing or abolishing conduction in the frog's sciatic by the
compression caused by a weight of a few grammes, without any
preceding signs of excitation, as already observed by Fontana.
VOL. in 0
FIG. 12G. — Apparatus for measurable compression of
frog's nerve by a silk thread. (Uucceschi.) 1, metal
plate pierced with two small holes ; «, sciatic nerve ;
/, silk thread ; b, balance to carry weights ; »•, support
moved by screw v to allow the weight to be applied
gradually.
194
PHYSIOLOGY
CHAP.
He saw that conductivity returned a few seconds after the pressure
was removed, provided it had not been excessive nor unduly pro-
Fni. 127. — Myograms of frog's gastrocnemius (1) with electrical stimulation ; (2) with break shocks
at an interval of 4 sees. (Ducceschi.) In both tracings a weight was applied at ^ the value
being marked in grammes ; at -^- the compression ceased.
longed (Fig. 127). If, while the frog's gastrocnemius was being
tetanised by an interrupted current applied to the sciatic, the
nerve was compressed below the point of excitation, the trans-
mission of the impulses was partially inhibited, and the almost
FIG. 128. — The marks on these tracings correspond to those of the preceding figure.
At b and c the nerve was tetanised.
tonic contraction of the muscle was transformed into a clonic
contraction (Fig. 128). The effects of graduated compression on
conductivity differed according as chemical, mechanical, or electrical
iv GENEKAL PHYSIOLOGY OF NEEVOUS SYSTEM 195
stimuli were employed, owing probably to their different intensity.
When excitation from chemical stimuli (glycerol or hypertonic
salt solution) was no longer able to pass the compressed point,
excitation from mechanical stimuli was able to get through ; when
the latter was blocked by the compression, electrical stimuli were
still effective (Fig. 129). It is an interfering fact that reflex
spinal excitation is arrested by a minimal degree of compression
such as blocks the transmission of chemipal stimuli.
A frog's nerve ceases to conduct when its diameter is reduced
to one-third or one-fourth of the normal ; it then becomes trans-
parent, as the fluid contained in the myelin sheath is pushed back
above and below the point of compression. Histological inspection
of the nerve compressed by a silk thread shows that there is
no blackening of the myelin
sheath by osinic acid near the
point of compression, but the
axis-cylinder (the conducting
element) is reduced in size.
After D ucceschi, Signorina
Calugareanu (1901) experi-
mented iu Dastre's laboratory,
by a somewhat different
method, on the effects of
mechanical compression of
the nerve of the electrical
Organ Of Torpedo, the frog's Fio. 129.— The very rapid contractions at the begin-
• ,• -i ,1 11 •,> ning of the tracing were due to chemical stimula-
SCiatlC, and the rabbit S VagUS. tion with glycerol, applied to the upper part of
She also obtained diminution the nerve- At ^ the nerve was compressed by
P i ,• ., •.I 25 grms. At </ it was stimulated above the point
01 COlldllCtlVlty WltbOUt any of compression with break shocks.
previous rise of excitability,
and found that the injurious influence of compression was
not manifested immediately, but after a certain time (about 1
minute).
Bethe, too (1903), studied the effect of compression on frog's
nerve by a method similar to that of Ducceschi, with reference
more particularly to the histological changes. He found that by
a degree of compression which did not abolish conductivity to
electrical stimuli the axis-cylinder may be considerably reduced
in diameter, at the cost not of the neuro- fibrils which compose it,
but of the perifibrillar substance (or neuroplasin). According to his
calculations the amount of perifibrillar substance in the normal
fibre is to that of a compressed fibre which is still capable of con-
ducting, as 654 : 1. This, he says, proves that conductivity is a
function of the neuro-fibrils and not of the perifibrillar substance.
Bethe further noted that when the nerve-fibres are rendered
incapable of conducting by compression, they also lose their
capacity for primary staining, i.e. staining with basic dyes in the
\
\
196 PHYSIOLOGY CHAP.
fresh state, or when dehydrated only, — which returns when con-
ductivity is re-established.
One of the most important facts, which may rank as a funda-
mental law of nerve conduction, is that each fibre of a nerve
conducts the excitatory impulse from the periphery to the centre,
or from the centre to its terminal ramifications, without spread of
the excitation by contact to the neighbouring fibres. In the case
of a mixed nerve the motor fibres can be excited along their
course without simultaneously producing sensations, or the sensory
fibres without simultaneous production of movements. The most
convincing proof of isolated conduction of the active state in
individual fibres is afforded by the delicacy of localisation, both of
movements and, still more, of sensations. It is possible to stimulate
the small bundle of fibres that form the motor roots of the
sciatic separately so as to produce localised contractions in the
individual muscles or portions of muscles which they innervate,
without diffusion of the impulse to the whole group of muscles
that are thrown into action by stimulating the trunk of the sciatic.
The excessively delicate localisation of tactile sensations, the
sharpness of outlines and shading of colours in visual images,
would be quite impossible if each fibre of a peripheral or optic
nerve were not an isolated conductor.
This localisation of movements and sensations, with which we
are all familiar, has so far received no mechanical explanation. It
has been thought on good evidence that the sheaths, and particularly
the myelin sheath, are mainly responsible for the complete insula-
tion of the axis-cylinder ; but the fact that this insulation holds
good for the non-medullated nerve-fibres as well leads one to
conjecture that it is a property inherent in the axis -cylinder,
though we are ignorant of the cause to which it is due. That
insulated conduction does not depend> on the medullary sheath
is further proved by the fact established by Ducceschi, that when
the frog's sciatic is so compressed as to rupture the sheath without
blocking the conductivity of the nerve, isolated contraction of the
separate muscles of the foot can be obtained by stimulating single
branches of the lumbro-sacral plexus.
The new theory of the minute structure of the nervous system,
according to which the axis-cylinder and the dendrites are con-
sidered not as elementary nerve-fibres but as bundles of separate
fibrils forming an elementary network, naturally raises the question
whether the law of insulated conduction is applicable to the pro-
cesses (dendrites and axons) of the ganglion cells as a whole, or
to the individual fibrillary elements of which these seem to
consist. It must be confessed that science is not yet ready to
solve this problem, which needs a more complete knowledge of
their anatomical relations. We can only say that many ramifica-
tions of nerve-fibres are merely dissociations of distinct fibrils
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 197
united into bundles, and that the true ramifications of the con-
ducting elements probably exist only in the terminal and peripheral
organs, where distinction and localisation of the physiological
effects of the excitation transmitted along the conducting filaments
is no longer necessary.
Another fundamental fact of nerve conduction is what William
James, the psychologist, termed the forward direction. Conduction
is normally centripetal, i.e. from the periphery to the centre in
sensory fibres and afferent fibres in general, and centrifugal, from
centre to periphery, in the motor fibres and efferent fibres in
general. Again, when the nerves are artificially stimulated along
their course, the effect is expressed in movement for motor nerves,
in sensation for the sensory. We shall see, in fact, in discussing
the physiology of the special nerve roots, that on stimulating the
central stump of a root that contains motor fibres only all sensory
reaction fails, and on stimulating the peripheral stump of a root
containing only sensory fibres no motor reactions are obtained.
This fact at first sight justifies the conjecture that sensory
nerves can only conduct the excitation in an afferent direction
when excited along their course, and motor nerves only in an
efferent direction, as though there were some valvular mechanism
which allows the transmission of the impulse in one direction and
blocks it in the other. Certain experimental facts, however, show
this hypothesis to be untenable, and indicate that nerves in
general, when artificially excited at any point of their course, are
capable of conducting in both directions, but the effect is manifested
only at the centre for sensory nerves, and at the periphery for
motor nerves.
The best argument for double conduction appears from the
study of the electrical phenomena that accompany the excitation
of nerve. This will be discussed in a separate section. When a
nerve is stimulated midway, while the two ends are joined up to
two galvanometers, the so-called negative variation is seen on
both. This occurs not only with a mixed nerve, which contains
both sensory and motor fibres, but also, as Du Bois Reymond
pointed out, with a nerve which contains only motor (efferent)
fibres, e.g., the ventral spinal roots.
Gotch and Horsley repeated and varied this experiment, both
with efferent and afferent nerves. They divided a ventral root of
the sciatic plexus in the cat ; connected it with a highly sensitive
galvanometer, and then excited the trunk of the sciatic. A double
reaction followed — -of the muscles of the limb, which proved
centrifugal conduction in the motor fibres, and of the galvano-
meter, which showed centripetal conduction in the same motor
fibres. Similar effects were obtained with sensory nerves. On
exciting a dorsal root and connecting the central end of the
divided sciatic with the galvanometer, the negative variation
198 PHYSIOLOGY CHAP.
appeared, which is a proof of centrifugal conduction in the sensory
fibres.
Many other attempts have been made to demonstrate the
possibility of reversal of the normal passage of excitation along a
nerve. Schwann divided the sciatic of a frog, and allowed the
two ends to unite. He then stimulated the sensory roots of the
nerve, and saw that its excitation produced no contraction in the
muscles of the limb. From this he concluded against the theory
of conduction in a double direction, since it seemed to him im-
probable that each afferent or efferent fibre of the two stumps
should be able to unite with a fibre of its own kind. But the
fact that normal sensibility and motility is recovered after nerve
section shows that what Schwann thought so impossible really
does take place. His experiments, which Steinbriick confirmed in
1838, do not therefore overthrow the theory of conduction in
both directions.
Bidder (1841) attempted to connect the peripheral end of the
hypoglossal (motor nerve) with the central end of the lingual
(sensory nerve), but he only managed to unite trunks of the same
kind, as in Schwann's experiments. Union of heterouomous
stumps was, however, obtained by the subsequent experiments
of Gluge and Thiernesse (1859), Philipeaux and Vulpian (1860),
Roseuthal (1864), and Bidder himself (1865). It was found that
when the two nerves above mentioned had united, stimulation of
the lingual produced movements of the tongue, and stimulation
of the hypoglossal (united to the central end of the lingual) elicited
signs of pain.
These results seemed to be positive evidence for conduction in
I both directions ; subsequent researches, however, proved them
capable of a different interpretation. The symptoms of pain when
the hypoglossal was stimulated can, according to Arloing and
Tripier, be interpreted as a phenomenon of recurrent sensibility in
the stump of the hypoglossal, and the movements of the tongue
on stimulating the lingual may, according to Vulpian's last work,
depend on excitation of the fibres of the chorda tympani, which is
an efferent nerve. If, on the other hand, the hypoglossal on one
side be cut so that it degenerates completely, and the peripheral
stump of the freshly divided lingual nerve is then excited, a slow
contraction of the tongue follows, which is due to the chorda
tympani and is accompanied by vascular dilatation. The mechanism
of this phenomenon is very obscure, since the chorda tympani has
no direct anatomical connection with the tongue muscles, and
produces no motor effect under normal conditions, i.e. when the
hypoglossal is uninjured. So that none of these experiments are
of any account for the question of double conductivity in nerve.
Nor can any greater value be assigned to the experiments which
Paul Bert carried out on rats by suturing the tip of the tail to the
iv GENERAL PHYSIOLOGY OF NEEVOUS SYSTEM 199
skin of the back, and dividing it when healed close to the root.
As he elicited signs of pain on exciting this inverted tail, he
concluded that conduction in the nerve had been reversed. But
till we know what phenomena of degeneration and regeneration
take place in the nerve, after transplanting the tail, it is impossible
to give any positive explanation of the results of this experiment,
and it cannot be invoked in favour of the law of double conduction.
Kiihne (1859) attempted by another method to prove con-
duction in both directions. He divided the broad end of a freshly
dissected frog's sartorius into two strips with scissors, and found
that mechanical stimulation of one of the strips produced h'brillary
contractions which were not confined to the segment of muscle
that was directly excited, but spread also to the strip that had
not been excited. According to Klihne this phenomenon can only
be explained on the assumption that the excited and non-excited
segments of muscle contain nerve-fibres which come from the
bifurcation of the axis-cylinders of the principal nerve. The
excitation is transmitted centripetally in the nerves of the first
strip, and then spreads centrifugally to the nerves of the second
strip.
Babuchin repeated this experiment on the electrical organ of
Malapterwrus which has a single gigantic many-branching nerve-
fibre. He found that excitation of a single twig of this fibre
suffices to produce a discharge of the whole electrical organ.
Hermann attached great importance to these experiments of
Ktihne and Babuchin as evidence for the law of conduction in
both directions. Other authorities, on the contrary, make strong
objections, for which we have not space, particularly as Kiihne,
in a memoir of 1886, published a long series of new experiments
on the pectoral and gracilis muscles of the frog which lend them-
selves better to the solution of the problem.
If the pectoral muscle of the frog is divided as shown in Fig.
130, by leaving a bridge (Z~] which carries the nerve and a few
muscle fibres, mechanical, chemical, or electrical stimulation of
this bit of tissue will cause the whole of the remainder of the
preparation (J/) to contract. This contraction is not fibrillary as
in the sartorius, but diffuse and simultaneous in all the fibres of
the muscle, so that it can be graphically recorded and shown to
exhibit the characteristics of a single twitch. The experiment of
Fig. 131 is still more decisive. It shows that retrograde con-
duction of the nerve impulse along the motor fibres may also
occur between two parts of the same muscle (K and L], united
only by the nerve (&), on stimulating one portion of the nerve (Z),
so that any direct intervention of the muscle fibres in causing
the phenomenon is excluded.
Kiihne ascertained by a minute histological examination of
the nerves of the frog's pectoral and gracilis muscles that the
200
PHYSIOLOGY
CHAP.
dichotomous branchings of the nerve-fibres occur principally at
the points at which the nerve enters the muscle, and in the
extramuscular part of the same nerve. This dichotomous division
of the nerve-fibres is brought about by the separation of the fibrils
of which, according to Schultze, the axis-cylinders are composed.
Hence the experiments of Kiihne not only yield a direct proof
of double conductivity, but they also imply that the isolated con-
duction which Johannes Miiller showed to be a property of the
axis-cylinder does not hold as between the fibrils of which each
axis-cylinder is composed.
Kiihne employed the same method to demonstrate unequivocally
that the paralysing action of curare is localised in the end-plates
of the muscular nerves, and does not spread to the motor fibres
Z
...
1'lUv
rTXiF
I
ft
I ^
p" '
f !
i ' L
N
FIG. 130. — Killing's experiment on frog's pectoral
muscle. -Y, iirrvt- which supplies the right
half (in) of the muscle ; the left half is cut
away leaving only the bridge Z, which con-
tains the part of the nerve that is mechanic-
ally stimulated.
PIG. 131. — Kiihne's experiment on the gracilis
muscle. N, nerve that gives off branches
to the two separate parts of the muscle
A' and L and to the bridge of muscle Z,
which is mechanically excited.
(see Chapter I.). He employed the gracilis muscle of the frog,
which can be divided by a ligature into two portions, in only one
of which the poisoned blood circulates. The muscle thus treated
can be cut so that the nerve forms the only connection between
the curarised and non-curarised portions (Fig. 132). Under normal
conditions the mechanical stimulus applied at N, Z, or K pro-
duces a contraction of the entire muscle according to the law
of the backward conduction of excitation ; but in the curarised
muscle mechanical stimulation of the nerve at N and at k will
only cause contraction of the part K, i.e. the non-curarised portion
of the muscle, the same effect being produced by exciting the
branches / and I' of the curarised portion. This proves that the
nerve-fibres have not been paralysed by the curare, since con-
duction in a centripetal direction takes place in them, as under
normal conditions.
It may be argued logically from the law of double conduction
that the motor and sensory nerves do not differ fundamentally in
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 201
their internal constitution. That under normal conditions the
former conduct centrifugally and the latter centripetally depends
not ou any intrinsic difference, but on the specific nature of the
organ with which they are related at the centre or the periphery,
and to which they transmit the excitation. If experimental efferent
excitation of sensory nerves and afferent excitation of motor
nerves produces no perceptible motor or sensory effects, there must
at the peripheral end of the former and central end of the latter
be some apparatus, as to the nature of which we are entirely
ignorant, which hinders the excitation from being propagated, as
a system of valves determines the direction of flow of a current.
There is thus no intrinsic contradiction
between the law " of the forward direc-
tion of normal excitations " and that " of
the double direction of experimental
Vexcitation," i.e. such as is artificially
produced along the course of the nerve.
Intimately connected with this law
is the other which Hermann (1879)
termed "law of the constant effect of
nervous excitation." Whether a nerve
be excited at its end or at any point
along its course, the effect on the organ
of reaction is invariably the same, viz.
I muscular movement for motor nerves,
sensation for sensory nerves. The local- Fio. 132. -Kuime's experiment
isation and character of the muscular
movement are determined not by the
site of stimulation, but by the number
of fibres excited and their peripheral
distribution to the muscle. So, too,
the location and specific quality of
the sensation, e.g. pressure, heat, and
pain, which occurs on stimulating a sensory cutaneous nerve
at any point, is identical with that produced by the action
of natural stimuli upon the end-organ in the skin. The most
striking example that can be adduced in proof of this law is that
observed when a limb has been amputated. " When the member to
which a nerve trunk is distributed," says Johannes Miiller, " is
removed by amputation, the stump of the nerve which contains
the whole of the shortened nerve-fibres is capable of the same
\sensations as if the amputated limb were still present. This
persists all through life." If the stump becomes inflamed, such
persons complain of sharp pains in the entire lost limb. Upon
recovery they have the same sensations that normal people feel in
a healthy limb, and there is often a persistent sensation of itching,
or discomfort, which appears to be localised in the limb that no
frog's graeilis muscle, halt' of which
had been poisoned with curare and
then severed, so that only the
nerve was left as a connecting
bridge. N, nerve that gi\es
branches to the poisoned L and
non - poisoned K, halves of the
muscle ; k, connecting bridge ;
Z, nerve -muscle biidgr that is
mechanically excited.
202 PHYSIOLOGY CHAP.
longer exists. Many persons eventually become accustomed to
these sensations, and cease to notice them ; but they surge up
again when attention is focussed upon them, and are often felt
distinctly in the fingers, sole of the foot, or hand. The sensation
is more acute when pressure is exerted on the stump.
The symptoms of anaesthesia dolorosa are no less important
to the demonstration of the peripheral projection of sensations.
Traumatic paralysis from compression or section of a nerve trunk,
in which more or less extensive cutaneous areas become totally in-
sensitive to the strongest stimuli, though the patient still complains
of intense pain in them owing to the irritable state of the nerve
trunk, is not infrequent. In surgery, division of the nerve may
fail to cure neuralgia, as it merely interrupts the conduction of
external peripheral excitations to the centre, but cannot suppress
the conduction of central irritation in the nerve, which gives
origin to sensations projected to the periphery similar to those
produced by extrinsic local stimulation.
The phenomenon of the peripheral projection of sensations can
easily be demonstrated under normal conditions by mechanical
excitation of one's own ulnar nerve in the groove of the internal
condyle at the elbow, where it is accessible ; this produces a prick-
ing in the palm and back of the hand, and in the third and fourth
fingers. Pressure on the infraorbital nerve, where it issues from
its foramen, produces pricking at many points of the cheek and
upper lip.
III. Johannes Miiller in 1844 declared the problem of the
velocity of nerve conduction to be insoluble, and compared it with
that of light. " The time," he writes, " in which a sensation
passes from the exterior to the brain and spinal cord, and thence
back to the muscle so as to produce a contraction, is infinitely
small and immeasurable." Only six years later, in 1850,
Helmholtz was able by exact physical methods to determine the
rate of propagation in a frog's nerve, and to demonstrate that it
is infinitely slow in comparison with the propagation of physical
energy. Electricity traverses a space of 464 million metres in a
second, light 300 million, sound 332 metres; the excitatory
impulse in nerve, on the contrary, is transmitted at a rate so
much lower that it may be compared with the speed of a loco-
motive or the flight of an eagle.
The first exact measurement of the velocity of conduction in
nerve was made by Helmholtz on a frog's nerve-muscle preparation
(Fig. 3). If the time-interval between the stimulation of the
nerve and the contraction of the muscle (latent period) is measured,
it is found to be greater when the motor nerve is stimulated at a
point remote from the muscle than when it is stimulated near the
muscle. The difference in the time-interval is also, carteris paribus,
proportional to the length of nerve between the two points excited.
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 203
From the difference in time and the length of the nerve as
measured the rate of conductivity is easily calculated.
Helmholtz employed two methods for determining the time that elapses
between the (electrical) stimulation of the nerve and the reaction of the muscle.
The first method, invented by Pouillet, consists in measuring the duration
of an electrical current, sent through a galvanometer at the moment of excit-
ing the nerve, and interrupted at the moment at which the muscle contracts
(for details of the application of this method see Biedermann).1 The second
method, employed after Helmholtz by all physiologists, is a special applica-
tion of the graphic method. The times of nerve excitation and muscle con-
traction are recorded by a myograph on the smoked paper of a drum or plate,
which is moving very rapidly, the time being marked on the same surface
by means of a tuning-fork. The difference in time can thus be measured
exactly between the first stimulation of the nerve close to the muscle and the
commencement of the muscular contraction, and the second stimulation
farther from the muscle and commencement of the second: contraction.
When the times of the two successive stimulations are recorded at the same
point of the revolving drum (as in Fig. 133), the distance between the initial
Fir.. 133. — Velocity of nerve conduction, as measured by Marey on himself. 1, myogram traced on
exciting the nerve close to the muscle ; 2, myogram on exciting the nerve 30 cms. from the
muscle ; D, time tracing from a tuning-fork at 250 double vibrations per second. The interval
between the two contractions occupies about 2-5 vibrations, corresponding to O'Ol sec. in
which the impulse traverses 30 cms. = 30 m. per second.
point of the two contractions is all that is required to calculate the rate of
conductivity, when the length of nerve between the two points of excitation
is known.
From an average of the experiments made by Helmholtz on
the frog's nerves the velocity of nerve conduction was found to be
27'25 metres per second, which is much less than the velocity of
the propagation of sound in air, but greater than the propagation
of the contraction wave in the muscle of the same animal, this
being, as we have seen, about 1 metre per second.
Helmholtz and Baxt also determined the rate of conductivity
in the motor nerves of man. They recorded the myograms of the
thumb-muscle upon a rotating cylinder by placing a sensitive
lever on the thenar eminence, and exciting the median nerve
either in the axilla or near the wrist joint, through the previously
moistened skin. The rate obtained was somewhat higher than for
frog nerves, i.e. 30-35 in. per second.
Helmholtz and many other investigators have also attempted
to determine the rate at which the impulse is propagated in the
1 Electro-Physiology, English translation by F. A. Welby, 1896, ii. 59.
204 PHYSIOLOGY CHAP.
sensory nerves of man, but the resulting data are discordant and
unconvincing. The method consists in determining the reaction-
time to tactile sensations sent in at two points on the skin of the
arm, at different distances from the centres. As soon as the
subject perceived the sensation he pressed a button which marks
the moment of reaction upon a revolving cylinder. It was
formerly assumed that the reaction-time for two approximately
identical sensations, evoked at two points of the skin at different
distances from the centres, differed only in proportion to the
different length of nerve through which the impulse has to
pass before reaching the centres. The discrepancy of results
obtained by various experimenters, which ranges from 26 to more
than 100 m. per second, however, shows that the lost time at
the centres, where the afferent excitation is transformed into a
motor impulse passing down the efferent nerve, must vary con-
siderably, according to the site of stimulation, the state of fatigue
and degree of attention of the subject, with other less appreciable
conditions. It is probable, judging from other experiments to be
described later, that the rate of conductivity is the same in
sensory nerves as in motor.
Considerable differences in rate of conductivity are found in
the lower animals, and even in different kinds of nerve in the
same animal. Fredericq and van de Velde found for the nerves
of the claw of the sea-crab a velocity varying from 6 to 12 metres
per second when the temperature varied between 19° and 20° C.
v. Uexkiill found variations of O'4-l m. per second for the nerves of
the mantle of Cephalopoda ; Chauveau found in the vagus fibres
that innervate the smooth muscle cells of the oesophagus of large
mammals a velocity averaging 8'2 rn. per second, while in the
vagus fibres that innervate the striated muscles of the larynx it
averaged 66'7 m. per second. According to Chauveau -this rate
is not uniform for all parts of the nerve, but falls in the parts
nearest the muscle.
From some of Gotch's work, again, it seems highly probable
that the rate of transmission of the motor impulse is much lower
in the terminal branches of the nerve than it is in the principal
trunks. In experiments on the electrical organ of Malapterurus,
in which a gigantic nerve-fibre terminates in a very free arborisa-
tion, he measured the difference of latent period obtained on
exciting the organ -directly or through the nerve, and found that a
non-negligible fraction of time (0'003-0'005 per second) was lost
in the transmission of the impulse along the twigs of the nerve.
On repeating the experiments of Babuchin on the same nerve
(see p. 199) to see if the retrograde centripetal conduction of
the impulse proceeded at the same rate as the centrifugal, his
results led him to conclude that the velocity of conduction did not
alter with the ascending or descending direction of the impulse.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 205
The influence of temperature on rate of conduction in nerve is
very apparent. Helmholtz, experimenting with the motor nerves I
of frog, found that their conductivity diminished considerably
on cooling, and increased on warming to 25° C. Gotch and
Macdonald made a careful research, exciting the same nerve at
regular intervals with minimal or nearly minimal stimuli. They
found that on cooling the nerve to 5° C. the muscular response
diminished or disappeared, while on warming it to 35° C. it was
increased and became maximal. So that cooling diminishes not
only the velocity of conduction, but the intensity of the effect trans-
mitted by the nerve as well ; heating produces the opposite effect.
Helmholtz and Baxt further observed that both the rate of
conduction and the intensity of the effect transmitted vary
with alterations in the strength of the stimulus. This result,
obtained on the brachial nerve of man, was confirmed by
Vintschgau for the motor nerves of frog, and by Fick for the non-
medullated nerves of Anodonta. It was, however, always disputed
by Rosenthal and Lautenbach, and it is in any case doubtful
whether it applies to mechanical and chemical excitation as well
as to electrical stimuli. It should further be noted that the
shortened latent period obtained on stimulating the nerve with a
stronger induction current may be apparent only, which is due
to the fact that in this case the current spreads further and
stimulates points of the nerve which lie nearer to the muscle.
We shall later discuss the alterations in the conductivity of
the nerve caused by electrotonus.
Fr. W. Frohlich (1904), in studying the oxygen demand, and
the effects of narcosis on the frog's sciatic (infra], showed by the
myographic method that the rate of transmission of the nervous
impulse undergoes a local diminution during asphyxia and
narcosis in the part of the nerve affected, and that this became
more marked in proportion to the length of nerve involved. This
delay in conduction is perceptible even in a state of narcosis or
asphyxia in which conductivity seems by other methods to be
unaltered.
According to Ch. Richet the experimental results arrived at
by the various authors as to the velocity of transmission of the
excitation or active state of the nerve may be summarised as
follows :—
(r/,) In the frog the mean velocity of the nervous vibration (as
he terms the active or excited state of the nerve) is from 20 to
26 m. per second.
(&) In warm-blooded animals this velocity is 30-34 m. per
second.
(c) It varies with a number of factors, particularly with the
temperature.
It is not identical in every part of the nerve.
206 PHYSIOLOGY CHAP.
From these facts we derive the important conclusion that
fthe internal excitatory process, or active state of the nerve,
Us transmitted at a rate that is, comparatively speaking, so low
that it must undoubtedly consist in a physico-chemical change of
the living substance of the axis cylinder, propagated by contiguity
from one part to the next. The conduction of excitation in the
nerve is analogous to the transmission of excitation in the muscle,
although it occurs much more rapidly. We may assume with
Pfliiger that potential energy is liberated during activity in nerve
as in muscle, this chemical process being propagated from segment
to segment till it reaches the muscle, where it excites the
mechanical process of contraction just as the spark of a match
produces an explosion when it reaches the powder in a mine.
As in muscle so in nerve, it can be proved that excitation
is a diphasic cyclic process, whatever concept be formed of the
hitherto unknown chemical changes aroused by the stimulus.
Just as in muscle the phase of relaxation follows the phase of
contraction, and the whole cycle of muscular excitation results
from these two factors, so in nerve the active state results, as can
be demonstrated, from a physico-chemical, presumably katabolic,
change, followed after a brief interval by the opposite (anabolic)
change, which represents the return of the protoplasm of the
nerve to the molecular equilibrium proper to the resting state.
Our physiological analysis of the phenomena of excitation will
yield constant confirmation of this law.
IV. We have seen that the excitation or active state of a
muscle is expressed in three orders of effects ; in mechanical,
chemical, and electrical phenomena. The active state of a
nerve induced by various stimuli is, on the contrary, so far as we
know, expressed solely by alteration of its electrical potential.
The chemical composition of the axis-cylinder (the only really
and specifically active part of a nerve) is totally unknown to us.
Under the microscope it gives the xanthroproteic reaction and
other indications of a protoplasmic character. From this single
fact we may conclude, with Foster, that there is a generic
analogy between the chemical composition of the active sub-
stance of muscle and that of nerve, and conjecture that the
transmission of excitation along the nerve-fibre is accompanied
by chemical changes similar to those which take place in the
muscle fibre. It is, however, certain that the nutritive exchanges
and metabolic phenomena which are theoretically probable in
nerve must be extremely small, since it has so far been impossible
to obtain any direct demonstration of them.
A. D. Waller, starting from the observation (which we shall
discuss below) that there is a relation between the functional
capacity of the nerve and the variations produced experimentally
in the CO., content of the surrounding atmosphere, concludes that
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 207
the nerve produces carbonic acid during its activity ; but there is
so far no direct demonstration of this fact. It has, indeed, as we
shall see, been demonstrated of late years by the school of Verworn
(H. v. Baeyer, Fr. W. Frohlich) that the nerve requires a supply
of oxygen to keep up its vitality. Thunberg succeeded in
measuring the quantity of oxygen absorbed and of carbonic acid
given off. But no one has yet proved that this respiratory gas
exchange depends directly upon the state of rest or activity of
the nerve. Funke found that the normally alkaline reaction was
converted into an acid reaction in a nerve treated with strychnine,
owing to its exaggerated activity, but this observation has not
been confirmed by other workers. Rohmann, who experimented
on the nerves of the electrical organ of Torpedo, using acid fuchsin
as his reagent, failed to obtain any positive result.
The exceedingly slow character of nerve metal lolisrn can also ,
be detected in the fact that, unlike the grey matter, which is
irrigated by a rich network of blood capillaries, the vascularisa-
tion of nerve is very little developed. But the best argument, of
which we shall give experimental proof later on, is the fact that
nerve, unlike the nerve-centres, is practically inexhaustible, i.e. it
shows no visible signs of fatigue, even when thrown into a state I
of activity for several hours.
Thermal phenomena, again, such as are due to katabolic
processes, are very small and insignificant in the active nerve.
Schiff found a slight increase in heat development when he
applied the thermo-electric pile to nerve. But the same method
yielded negative results in the hands of other expert observers
(Helmholtz, Heidenhain). Nor did Rolleston arrive at any
positive result with Callender's extremely sensitive method.
It seems impossible to doubt that metabolism is very low in
nerve-fibre, even after strong and persistent stimulation, which
evidently means that the work the nerve has to perform is
inconsiderable. Both when the excitation is propagated from the
periphery to the centre (afferent nerves) and when it travels from
the centre to the periphery (efferent nerves), the nerve only needs
to send a slight impulse, a tiny spark, to the end - organ with
which it is connected in order to effect a vigorous process and
marked explosion of energy, owing to the great irritability of
that organ.
Yet, however slight it may be, the process of excitation and
conduction in the nerve-fibre must involve a certain consumption
of energy. That the products of chemical dissociation and the
correlative development of heat are not demonstrable even after
strong and protracted stimulation, suggests that the chemical i
dissociation is rapidly compensated by a process of restitution. '
Gad, in • formulating this notion more precisely, assumes that the
restitution of the substance that has been altered by excitation
208 PHYSIOLOGY CHAP.
in any part of a nerve is accomplished instantaneously at the
expense of the next part, and that upon this the propagation of
the excitatory impulse depends.
An indirect proof of this theory is afforded by the study of
the electrical phenomena exhibited by nerve in the state of rest
and of activity, which need only a brief description, since they are
almost exactly identical with those already discussed for muscle
(vide Chapter L, sec. XL, p. 68).
The discovery of the so-called current of rest in nerve was
made by du Bois-Beymond (1845). Any bit of nerve cut out
of the body presents approximately the same electromotive
phenomena as muscle, and these may be summed up as follows :—
(a) Two symmetrical points on the longitudinal surface and of
the two cross-sections of a nerve are as a rule iso-electric, i.e.
equipotential.
(6) Two points at different distances from the sections show a
FIG. 134. — Diagram <>f demarcation currents in a length of mixed nerve excised from the animal.
Direction ni currents indicated by arrows; e, physiological equator at the centre of the bit
of nerve.
difference in potential, in the sense that the point nearest the
cross -section is electrically negative, on the galvanometer, as
compared with the other point.
(c) Generally speaking, the surface of a transverse section is
negative to the natural or longitudinal surface, and the greatest
difference in potential, i.e. the maximum deflection of the galvano-
meter needle, is obtained on placing one unpolarisable electrode
on the cut surface and the other on the middle of the longitudinal
surface.
The diagram in Fig. 134 is a representation of these pheno-
mena. They are all comprised under the general law that in
i excised nerve the longitudinal surface represents the positive pole
' or anode, and the transverse surface the negative pole or kathode.
The currents that can be led off to a galvanometer from an
artificial cross-section and from any given point of the natural
longitudinal surface of a nerve, decline rapidly, especially in
warm-blooded animals. In the frog's sciatic the value of the
current may fall by one-half in two to four hours, especially in
summer. But the difference of potential may increase again, and
the current may regain its original force, if a new section is made
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 209
near the first. This fact seems to us important, because it
corroborates Engelrnarm's theory that the strength of the current
corresponds with the intensity of the lesion in the injured nerve,
and that this process of injury is arrested at the next node of
Ranvier. It also gives support to Hermann's theory that the
uninjured cell elements are incapable of developing electromotive
phenomena, and that the critical points of demarcation between
the healthy tissue and that injured by the section are determined
by these nodes.
Nerves that are wholly dead are incapable of giving currents.
Any lesion of a nerve along its course, by cauterising, crushing,
compression, etc., renders it negative to the normal parts. Local
changes of temperature in the nerve, if insufficient to produce
structural lesions (e.g. up to 30° C.), give rise to electromotive
phenomena, the heated tissue becoming positive to the normal
tissue, as occurs in muscle.
It may be deduced from all these facts that the electrical
phenomena of resting nerve depend on the negativity (on the
galvanometer) of the altered or injured portions of the fibres, in
relation to the uninjured, which justifies the name of demarcation
currents given by Hermann.
The strength of the demarcation currents does not appear to
be in strict relation with the area of cross-section. The frog's
sciatic gives a more vigorous current ( = O'02-O'Oo volt) than a
large nerve of the horse or monkey ( = O'OOS volt according to
Biedermaiin). This is probably due to the varying resistance and
susceptibility of the nerve to external agents. It may be affirmed
in general that every cause which decreases the functional capacity
of the nerve must also diminish the intensity of its demarcation
current.
An important fact discovered by different observers, both for
vertebrates and invertebrates, is that non-niedullated fibres yield
greater differences of potential and therefore larger currents than
medullated fibres, independently of their sectional area. From
this it may be inferred that the seat of the electrical phenomena \
is not the medullated sheath but the axis-cylinder of the nerve.
Another remarkable fact is that while in a mixed nerve-
composed of afferent and efferent fibres — the two transverse
sections, or two points equidistant from these upon the longi-
tudinal surface, are equipotential when connected with the
galvanometer, this is not the case for nerves composed of one
kind of fibre only — afferent or efferent. The central cross-section
of an afferent nerve (e.g. a dorsal root of a frog's spinal nerve) is
negative to the peripheral cross-section, but the central cross-
section of an efferent nerve (e.g. the electrical nerve of Torpedo) is
positive to the peripheral cross-section (Fig. 135). In these cases
the equator is not equidistant from the two cross-sections, but
VOL. Ill P
210 PHYSIOLOGY CHAP.
lies nearer the peripheral section in the afferent nerve, nearer the
central section in the efferent nerve.
This phenomenon, discovered by Du Bois-Eeymond and
confirmed by Fredericq, Mendelssohn, and others, indicates that
efferent nerves are traversed by an ascending, afferent nerves
by a descending axial current. This is the only objective
difference known at present between the two categories of nerves,
which are alike in structure and in their capacity for conducting
in both directions.
According to the latest work of Weiss (1904), the potential
difference between two cross-sections of nerve — the axial current
—is due solely to an anatomical cause, the unequal distribution
of the connective tissue. The more connective tissue present,
the less the potential that can be led off", owing to the resulting
short circuit. The contrary direction of the axial current in
efferent and afferent nerves might also be the result of unequal
arrangement of the connective tissue.
/
Centrifugal nerve. Centripetal nerve.
Fio. 135.— Diagram of axial currents in centripetal and centrifugal nerves. (Du Bois-Eeymond.)
c, central end ; ;<, peripheral end ; e, physiological equator.
The discovery of the current of rest or demarcation current
was immediately followed by that of the current of action, i.e.
the electromotive phenomena produced by stimulating a nerve,
which correspond perfectly with those already noticed for muscle.
In nerve as in muscle the current of action is manifested as the
negative variation of the demarcation current. If a current from
one end of the divided sciatic of the frog is led off to the galvano-
meter, it is reduced or abolished on exciting the other end with
a tetanising current. When stimulation ceases, recovery of the
original state is manifested.
Du Bois-Keymond's phenomenon of the negative variation can
also be demonstrated with chemical stimuli (Griitzner), mechanical
stimuli (Hering), and physiological stimuli (Gotch and Horsley)
for both afferent and efferent nerves. It is seen in afferent
nerves when the peripheral stump of the dorsal root of a
mammalian spinal nerve is connected with the galvanometer,
either the peripheral nerve or the sensory nerve-endings of the
skin being excited at a distance. It is seen in efferent nerves on
leading off the central end of the ventral root, or sciatic, to the
galvanometer, and exciting the ganglion cells of the cord or the
iv GENERAL PHYSIOLOUY OF NEIiVOUS SYSTEM 211
cerebral cortex directly, or reflexly, liy stimulation of the central
end of the sciatic of the opposite side.
The discovery of these electrical phenomena, which are the
constant corollary of nerve stimulation, signalled a considerable
advance in the general physiology of nerve, since they are the
only external manifestation known of the transition from the
state of rest to that of activity.
The negative variation of the current of rest depends on the
fact that the excited point of the nerve becomes for the moment
the seat of a negative electrical potential which is transmitted
lii
Ether
FIG. 136.— Photograph of electrical variations produced by rhythmical tetanisatiun nf an excised
nerve. (A. I>. Waller.) The stimulations were sent in at intervals of a minute. After applying
ether (black line) the electrical responses were suspended for about 5 min., after which they
recommenced and became more vigorous than before.
along the nerve as a diphasic wave, in complete analogy with what \
we have seen for muscle.
The strength of the negative variation is up to a certain
limit proportional to the intensity of stimulation (Waller). It
is a more reliable measure of the impulse in a motor nerve than
the height of the muscular contraction which the impulse induces.
In fact the maximum degree of muscular excitation is evoked
with a strength of stimulus less than that required for the
maximum degree of nervous excitation. When the maximal
muscular contraction is already obtained, it is still possible to
increase the value of the negative electrical variation by increasing
the strength of stimulation.
The negative variation alters with the excitability and \
conductivity of the nerve ; it is abolished or decreased by any
212
PHYSIOLOGY
CHAP.
factor that lowers functional activity ; on the other hand it is
effectively reinforced by all stimuli that promote activity. On
warming the nerve to 35-40° C. the duration of the negative
variation diminishes ; it is prolonged by cooling the nerve to
5° C. Lowering the temperature also delays the propagation of
the negative variation.
Waller studied the course of electromotive phenomena in
nerve by photographing the galvanometer deflections in a long
series of rhythmical tetanisations. These records give valuable
indications in regard to the effect of anaesthetics, salt solutions,
alkaloids, gases, etc., when applied directly to a length of excised
nerve. He concluded as follows : —
Chloroform
Fio. 137.— Photograph as before. (Waller.) The figure shows that after applying chloroform to
the nerve (black line) the electrical reactions are permanently abolished.
(a) Anaesthetics (ether and chloroform) temporarily abolish
the current of action and the excitability of the nerve. The
return of the action current after inhibition by ether is invariably
followed by a secondary augmentation : its suppression by chloro-
form is not only more prolonged, but may be permanent if the
dose is too strong (Figs. 136 and 137).
(5) Oxygen, nitrogen, hydrogen, nitrous oxide, carbonic oxide,
have no appreciable effect upon the current of action ; on the
other hand, carbon dioxide in small quantities (e.g. 4 per cent, as
in expired air) increases it ; in larger percentages carbon dioxide
acts exactly like ether (Figs. 138 and 139).
(c) Potassium salts have a decidedly depressing influence ;
sodium salts are less depressing. Calcium and strontium salts,
on the contrary, increase the current of action.
iv GENERAL PHYSIOLOGY OK NEEVOUS SYSTEM 213
(d) Among the alkaloids, aconitine and veratrine iu 1 per
cent solutions rapidly abolish the current of action ; curariue,
FIG. 138. — Photograph. (Waller.) To show primary excitation of the nerve by a small amount of
CO-2 applied between the two white lines.
digitaline, and morphine diminish its activity; strychnine in-
creases it ; atropine and aconitine are inert.
(e) Protracted tetanisation increases the current of action, i.e.
CO-j
FIG. 139.— Photograph. (Waller.) Shows that a large amount of CO», acting on the nerve
during the light band, at first suspends the electrical reactions of the nerve and then has a
secondary exciting action.
has an effect similar to that of CO., in small doses (Eig. 140).
Eroin this fact Waller argues that tetanisation of nerve is
accompanied by a development of C02.
214 PHYSIOLOGY CHAP.
These conclusions (as Boruttau pointed out) are partially
based upon the theoretical fallacy that the magnitude of the
galvanometer swing is an exact measure of the strength of the
current of action. This is not correct. The magnitude of the
galvanometer deflection is a result not merely of the strength of
the current but also of its duration. Admitting that the cessation
of deflections on the galvanometer indicates the disappearance of
the action current, it is not, on the other hand, legitimate to
assume that an increase in these deflections must represent an
increase of the action current and a rise of excitability. To study
the period of the current of action it is necessary to employ the
capillary electrometer, the oscillations of which can be photographed.
Fin. 140. — Photograph. (Waller.) Shows that prolonged tetanisation of the nerve
(at T from a. to <o) has the same exciting action on the electrical vuiiutions of
the nerve as a small amount of COo.
Boruttau and Frohlich (1904) were able, by this method, to show
that the action current in the nerve treated with alcohol, ether,
chloroform, and carbonic acid really suffers a decrement — the
amount of which is in ratio with the strength of the stimulus
and the length of the injured tract. The change in the period
of the excitatory wave is localised in the part of the nerve
that is affected ; while the diminution in the current of action,
once set up, affects the normal parts of the nerve as well.
The increase in the galvanometer deflection observed by Waller
as an after-effect depends not upon increased excitability, but
upon increased duration in time of the excitatory wave, which is
due to delay in the process of recovery.
The negative variation depends not only upon the intensity of
the stimulus but also upon the strength of the current of rest led
off to the galvanometer. It is more vigorous, as the anode is
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 215
nearer the centre of the longitudinal surface of the nerve, when
the kathode is on the cross-section. Moreover, many conditions
that affect the demarcation current in one direction or the other
affect the action current in the same way. Non-medullated nerve-
fibres, which yield a more pronounced demarcation current, also
exhibit a stronger action current. In non-medullated fibres
the mere opening or closing of a constant current indicates on
the galvanometer a diminution in the difference of potential present
in the resting state, while a tetanising current (i.e. a succession
of stimuli of given frequency) is required to obtain the same effect
in rnedullated fibres. This is because in medullated nerve the
intensity of the electrical phenomenon is too low for the passage
of a single wave of the action current to act upon the galvano-
meter. But it can be demonstrated, as in muscle, that the
uniform negative variation shown by the galvanometer during
the tetanising stimulation of a nerve is the effect of a series of
discontinuous electrical changes which have the same rhythm as
the stimulus sent into the nerve.
Bernstein (1867) demonstrated this with his differential
rheotome, by which the galvanometer circuit is rhythmically closed
for the briefest period at regular intervals which coincide with
each stimulation. He found that the negative variation starts at
once in the part excited, that it is propagated along the nerve at
the same rate as the excitation (27 in. per second at 15° C.) ; lastly,
that it remains a very short time at each point of the nerve
(0'0007 sec.), corresponding to a wave-length of about 18 mm.
Wedensky adopted the telephone to render the rapid successions
of the currents of action perceptible to the ear on tetanising the
frog's sciatic. When connected with the nerve that is being
tetanised, the telephone gives the sound that corresponds with the
number of induction shocks from the exciting current. When
the strength of the shocks is increased, the sound in the telephone
is also strengthened till it reaches a maximum, after which no
further increase of current strength increases the effect in the
telephone. If the nerve is killed by ammonia every sound in the
telephone ceases.
Gotch and Burch, by substituting a highly sensitive capillary
electrometer for the galvanometer, were able not only to demon-
strate the discontinuous character of the electrical changes
produced by faradisation of the nerve, but also to photograph the
action currents, as shown by the oscillations of the mercury
meniscus in the capillary. By this method they found that the
negative variation reached its maximum in O'OOl sec., and lasted
longer when the temperature was lower. Further, on comparing
the curves of the capillary electrometer with those obtained from
currents of known strength, they found that the negative variation
may amount to 0'03 volt at 5 J C.
216 PHYSIOLOGY CHAP.
On experimenting with a bundle of six frogs' sciatics, cooled
to 5° C. in order to delay the transmission of the wave of the
current of action, Hermann, with the rheotome, succeeded in show-
ing its diphasic character, i.e. the negative phase is followed by a
positive phase which is different in form, but of the same algebraic
value (Fig. 141). This was confirmed by Boruttau for the non-
niedullated nerves of Octopus and Elf clone, in which the rate of
conductivity is very low. Gotch and Burch photographed the
diphasic wave in frog's nerve, with reduced velocity of conduction,
on the capillary electrometer.
The diphasic character of the electromotive effects of rhythmi-
cal tetanisation can easily be seen in Waller's galvanometer
photographs. The curves show that the negative phase is often
PIG. 141. — Diagram of diphasic variation of electrical potential at two points of a nerve after a
single excitation, measured by the rheotome. (Hermann.) The curves a b c — d e f show
respectively the electrical variations from the points proximal and distal to the electro" Irs.
The diphasic curve traced by the coarser lines results from the algebraic sum of the preceding.
The spaces filled by cross lines, which represent the two phases of the wave, are approximately
equal according to Hermann.
followed by a positive phase, directly the stimulation ceases. The
positive phase is seen particularly in cooled nerve, and in nerves
injured by preparation, or by long soaking in normal saline. The
negative phase is most evident after prolonged tetanisation and
the action of a small amount of C02 (Figs. 138 and 140).
As for muscle, so for nerve, it is highly probable that the
negative phase of the current of action may be the expression of
a katabolic or disintegrative process, and the positive phase, of an
anabolic or reintegrative process.
After all that has been said of the current of action it is
natural to regard it as the external sign, and to a certain extent
the measure, of the active state of a nerve, i.e. of its excitation.
But it must not be thought that the electrical phenomenon con-
stitutes the whole or the essential part of excitation. In the
present state of our knowledge we must, while holding the current
of action to be concomitant with the active state of the nerve,
keep the two phenomena distinct ; since, as we shall see, the
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 217
electrical variation can be manifested after the excitability of tbe
nerve has entirely disappeared.
V. The term stimulus, as applied to nerve, covers every agent
capable of translating its excitability into action — as directly
expressed in the external sign of the current of action, by which
the physical change of tbe nerve is manifested. The indirect
subjective proof of nerve excitation is sensation, when the stimulus
acts upon our sense orga.ns : consciousness of the voluntary
impulse when it proceeds from the higher centres. The indirect
objective proof is a simple muscular contraction when the stimulus
acts upon the motor nerves, — a reflex muscular contraction when
it acts on the sensory nerves. In most of the work done upon
nerve the reaction of the muscle has been taken as the index of
activity, so that the results for the most part apply only to motor
nerves.
We must distinguish between natural and artificial nerve
stimuli. Nerve, like muscle, is excitable at every point of its
course by a great number of stimulating agents of varying
character (chemical, thermal, mechanical, electrical). Normally,
however, sensory nerves and afferent nerves in general are always
excited from the sense-organs with which their peripheral termina-
tion is in relation ; and motor nerves and efferent nerves in
general are always excited from the central organ from which they
take origin. Moreover, the peripheral organ of sensory nerves is
normally excited exclusively by external stimuli of a definite
character, which are therefore known as specific stimuli. As we
shall &ee later in describing the sense-organs, their nerve-endings
are so constituted that they are highly susceptible to the influence
of stimuli which would be powerless to excite the nerves themselves
at the different points of their course.
For this reason the natural stimuli for the respective sense-
organs are also termed adequate stimuli ; they are adapted to the
specific constitution of the sensory nerve-endings which they
stimulate. The adequate stimulus for the optic nerve is light,
which alone can excite retinal nerve-endings ; the adequate
stimulus for the auditory nerve is sound, which alone can excite
the nerve-endings of the organ of Corti, etc.
Motor nerves, again, are normally excited by specific stimuli,
produced by the (reflex or automatic) activity of the ganglion cells
of the central organ from which they originate, and on which
they are morphologically and functionally dependent.
The fact that naturally every nerve is excitable only at one
of its ends (peripheral or central), and only to a definite kind of
stimulus, is one of the most admirable adaptations of the animal
organisation, and prevents that chaotic disorder in the activity of
the whole system which would occur if the nerves were excitable
at every point of their course by different external and internal
218 PHYSIOLOGY CHAP.
factors, e.g. the tissue fluids by which they are irrigated, and
which regulate their metabolism.
Although under physiological conditions excitation never
occurs along the course of a nerve, it is, as we have seen, excitable
at any point, when acted on by an artificial stimulus of sufficient
strength. Its excitability is indicated by the minimal intensity
of the effective stimulus, when the latter can be measured with
sufficient accuracy. Speaking generally, we may say that the
minimal intensity of effective stimulus is less for nerve than for
muscle, which shows that nervous excitability is greater than
muscular excitability, and that the two forms of excitability have
a different organic substrate.
Of the many external agents which throw a nerve into activity
when applied experimentally, electrical and mechanical stimuli
are usually adopted : the former because they are easily graduated
and do little harm to the integrity of the nerve ; the latter
because their action can be localised to the point of application.
Thermal and chemical stimuli are less used, because they are
not easy to graduate and are more or less harmful.
(«) Little need be said in regard to thermal stimuli. The
intrinsic temperature of an animal (homoiothermic or poikilo-
therrnic) does not act as a stimulus on the nerve, but regulates
the normal degree of its excitability.
Nor does abnormal rise or fall of general or local temperature
as a rule act as a stimulus when it occurs gradually ; it merely
modifies the excitability of the nerve. The rapid heating of a
frog's motor nerve, by dipping it into water at 38° 0., or bathing
any given point with the same, may, according to Valentin, excite
a muscular twitch without causing local death of the nerve. But
this observation was not confirmed by Eckhard, who found that
contractions were only produced by a temperature of 66-68° C.,
i.e. when the rise of temperature was so great as to destroy the
structure of the nerve or permanently alter it. According to
Valentin, a rapid fall of temperature to - 5° C. also excites a nerve,
though gradual freezing produces neither excitation nor final loss
of excitability.
The later work of Kosenthal, Afanasieff, Griitzner, and others
was directed more to the influence of temperature upon the ex-
citability and conductivity of nerve than to its stimulating action.
It is true that when the temperature rises above 35° C. or sinks
to - 4° C., signs of excitation often ensue, but this fact can be
interpreted either as meaning that stimuli that are normally inert
become effective in consequence of the rise of excitability, or that
the too acute rise or fall of temperature develops specific stimuli
of a mechanical or chemical nature.
In regard to the stimulating action of abnormal temperatures
along the course of a sensory nerve, E. H. Weber observed on
iv GENERAL PHYSIOLOGY OF NEEVOUS SYSTEM 219
man that a few seconds after plunging the elbow into water at
the temperature of melting ice, a painful sensation is produced
over the whole cutaneous area served by the ulnar nerve, and later
a sensation of insensibility, which is undoubtedly due to diminished
conductivity in the cooled portion of the nerve.
(&) Many soluble chemical substances act as stimuli when
applied to an exposed nerve. But the excitatory effects which
they induce are irregular in character, and in all probability
their action depends either on the removal of water from the
nerve, or on the specific action which they exert upon its
molecular state; or again upon the alteration or death of the
nerve at the points of contact.
When a motor nerve is left to dry, its excitability rises at
first ; this is followed by a state of excitation expressed in a suc-
cession of small muscular twitches, or irregular tetanus ; lastly,
there is loss of excitability and conductivity. Up to a certain
point these effects are stronger in proportion to the length of
nerve exposed to desiccation. They vary also in different nerves,
and in different parts of the same nerve. If instead of dehydrat-
ing the nerve it is bathed in distilled water, the opposite phenomena
occur ; there is depression amounting to total loss of excitability.
It is certain that some organic substances act as stimuli
when applied to nerve, by abstracting water from it. Such, e.g.,
are glycerol, urea, the sugars, which stimulate motor nerves more
vigorously in proportion as they are more concentrated. As
regards the action of urea, Buchner noted that its prolonged
application is not, as is the case with other chemically exciting
substances, followed by loss of vitality in the nerve.
Nearly all the neutral salts, if applied for some minutes to a
nerve, act as stimuli with an intensity approximately proportional
to their concentration ; too strong a solution rapidly inhibits or
destroys the excitability of the nerve (Griitzner).
In order to obtain salt solutions perfectly comparable in their
effects, Griitzner employed equimolecular and not equivalent
solutions, i.e. solutions containing the same percentage doses of
salts. For the different sodium salts the scale of excitatory action
is NaF, Nal, NaBr, Nad. The molecular weights of these salts
are in an ascending order : NaF, 41'9 ; NaCl, 58'3 ; NaBr, 102'7 ;
Nal, 1494; and the percentage content of the equimolecular
solutions is NaF, 4-2; NaCl, 5-8; NaBr, 10'2; Nal, 14-9. From this
we may conclude that abstraction of water is not the sole factor
that determines the excitatory action of a salt, but that this
further depends upon the specific action of the chemical com-
pound upon the nerve. Griitzner demonstrated the same for the
salts of potassium, caesium, rubidium, barium, strontium, and
calcium.
Grlitzner's experiments on afferent nerves with these salts are
220 PHYSIOLOGY CHAP.
interesting. In view of the uncertainty of the results when
reflexes were taken as the index of excitability it occurred to
him to utilise the burning sensation felt on applying equimolecular
salt solutions to a cut on the finger. With sodium salts his results
were as follows: with Nal (14'9 per cent) sensation is aroused
after 5 sees.; with NaBr (10'2 per cent), after 10 sees.; with NaCl
(5-8 per cent), after 15 sees. Sensory nerves are accordingly stimu-
lated in the same order as motor nerves. But on vising potassium
salts Griitzner observed an interesting difference in the reaction of
motor and sensory nerves. These salts have only a slight stimulat-
ing effect on motor nerves, but act very powerfully on sensory
nerves ; for the latter potassium chloride is the most active,
sodium chloride is the least active of all. This important point
can be demonstrated by the following experiment. If the sciatic
plexus of an anaesthetised frog is divided on both sides, and
a solution of KC1 applied to the central end of one plexus and
the peripheral end of the other, reflex movements are seen in the
anterior limbs and trunk, while no contractions appear in the
muscles of the excited posterior limb ; on repeating the experi-
ment with NaCl, movements are seen in the muscles of the
directly excited limb, while movements of the reflexly excited
muscles only appear after an interval. This difference can be
interpreted to mean that KC1 is better able to excite in the
afferent direction, i.e. to awaken the activity of the central organs,
while NaCl is more able to excite along efferent paths, i.e. to stir
up the activity of the peripheral end-plates. Moriggia, on the
contrary, found that NaCl (04 per cent) excited the sensory and
not the motor fibres.
The results of experiments on the excitatory action of the
basic compounds do not agree. Eckhard and Kiihne observed that
even very weak solutions (01 per cent) of NaOH and KOH were
exciting^ to motor nerves ; Griitzner, on the contrary, found that
their stimulating action was very weak, while larger doses had a
destructive effect. Ammonia kills the nerve without exciting it.
Inorganic acid compounds in general have a stimulating action
proportional to their chemical avidity. Griitzner found that
nitric and hydrochloric acid stimulated in \veaker solutions than
sulphuric acid. The organic acids excite only in concentrated
solutions, and some of them (e.g. oxalic acid) destroy the vitality
of nerve without exciting it.
The salts of the heavy metals again affect the vitality of
nerve, without any previous stage of excitation, but according to
Eckhard and Kiihne, zinc chloride, zinc sulphate, and ferric
chloride are exceptions to this rule.
(c) Every one knowrs that mechanical factors, e.g. compression,
shock, crushing, pulling, cutting, puncture, produce excitation
when they act on nerve at a certain rate and with a certain
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 221
energy, since they induce pain in sensory nerves and muscular
twitches from motor nerves. Slight pressure or traction may
temporarily increase the excitability of nerve, but it is sometimes
possible, by slow but continuous mechanical action, to destroy con-
ductivity and excitability in a nerve without any perceptible
previous excitation. Paralysis of the brachial plexus has been
noted clinically as resulting from the constant use of crutches,
and paralysis of the recurrent laryngeal nerve is often due to its
compression by an aneurism.
Physiologists have devised various means of applying
FIG. 142. — Induction coil. (Dn Bois-Reymonrl.)
mechanical action, which has the great advantage of being
perfectly -easy to localise, as a nerve stimulus. The simplest
method is that of rapid section of the nerve with scissors. For
the quick repetition of mechanical stimuli, Du Bois-Reyrnond used
a little toothed wheel that compressed successive portions of the
nerve. Heidenhain employed a small hammer arranged so that it
always tapped a fresh bit of the nerve. A similar tetanomotor
was employed by Wundt and perfected by Tigerstedt, which acted
for a given time upon the same point of the nerve. Langendorff
substituted a vibrating tuning-fork for the hammer. Finally von
Uexkiill (1895) invented a rigid hammer which tapped the nerve
as it lay over a very soft pad, so that it was possible to stimulate
the same point for a long time without injuring the nerve ; this
222
PHYSIOLOGY
CHAP.
produced a form of stimulation very similar to faradisation, with
the advantage of eliminating all the errors due to spread of the
stimulus to other parts of the nerve.
A highly special form of stimulation is obtained by rapidly
removing the compression applied to the nerve. But in this case
it is not certain that there is true mechanical excitation ; more
probably the muscular reaction depends on the recovery by the
nerve of its normal fluid content, which had been altered by the
previous compression ; this gives rise to a demarcation current
which excites the nerve.
(d) The best excitant of nerve, as of muscle, with the strongest
analogy to physiological excitants is undoubtedly the electrical
current, of which the efficacy as a stimulus was demonstrated by
Galvani and Volta.
\
Flu. 143.— Dnnir
l iunl ]>u Bois-Reymoml
The electrical stimulus most employed is the induced current,
generated in a secondary circuit by the make and break of the
current which passes through the primary circuit of an induction
coil (Fig. 142). It can be perfectly graduated, is capable of
yielding a comparatively high electromotive force, is of brief
duration, and develops very rapidly. The regular series of make
and break shocks, or of alternating break and make shocks, from
Du Bois-Reymond's sliding induction-coil is generally known in
the laboratory as the tetanising current.
The direct application of the constant galvanic current from
a cell (Fig. 143) has the disadvantage, owing to its prolonged
passage, of producing electrochemical changes in the tissues greater
than those due to other methods of stimulation. This inconveni-
ence can be reduced to a minimum -by employing very brief
currents in alternating directions. It is also easy by means of a
rheochord to regulate the intensity and exactly measure the
electromotive force of the current employed as stimulus. Later on
iv GENERAL PHYSIOLOGY OF NKliVOUS SYSTEM 223
we shall examine the effects of galvauic currents upon nerve in
full detail.
We have already seen (p. 19) that alternating currents of
high frequency (Hertz waves) and sufficient intensity to light
an electric lamp have no stimulating action upon nerve or muscle,
probably because they paralyse conductivity (D'Arsonval).
The currents from a telephone are also capable of stimulating
nerve. Hiirthle succeeded in exciting a frog's nerve by the sounds
of a heart beating into a telephone.
Lastly, the physiological electromotive phenomena of the
electrical organs of Torpedo (Marey), as well as the intrinsic currents
of voluntary muscles of the heart and the nerve itself, can also
be used as nerve stimuli (Hering).
Whatever the nature of the agent employed as stimulus, the
excitation which it discharges — given constant excitability in
the nerve — is dependent both on the intensity of the stimulus
and on the rapidity with which its action begins and ceases, as
well as on its mode of action on the nerve. It is generally agreed
that the efficacy of a stimulus depends within certain limits upon
its intensity. But the method by which this law is deduced from
the muscular reaction, direct or reflex, is inaccurate. Waller
demonstrated (supra) that the only physical measure of the
activity of a nerve is its electrical variation, which is manifested
even when the stimulus is so weak that it fails to evoke any
muscular contraction, and which increases with the increase in the
strength of the stimulus, even when the muscular reaction is
already maximal.
The relations between the excited state and the mode of
stimulating the nerve have been studied particularly for electrical
currents. When applied to motor nerves (Ritter and others)
these produce a maximum effect at the moment of incidence and
of disappearance, and evoke a contraction only at the instant of
making and breaking the current, and not during its passage,
provided there are no rapid positive and negative alternations
of its strength. On the basis of these facts Du Bois-Reymond
formulated the law that currents stimulate in virtue not of their
absolute intensity but of the rapidity with which they arise and
disappear, or at which their intensity increases or diminishes. No
universal value can, however, be ascribed to this law. The
reaction of the muscle is not an exact index of the state of
activity of the nerve. Both during and after the passage of a
current, while the muscle is inactive, important changes are going
on in the nerve, which are not always, but only in given cases,
transmitted to the muscle. Further, under certain conditions, the
closure and opening of an electrical circuit connected with the
nerve will evoke a true tetanus instead of simple contractions.
Lastly, in sensory nerves there is, not only at the make and break
224 PHYSIOLOGY CHAP.
but also during the passage of the current, a continuous sensation
which is the subjective sign of an excited state of the nerve.
It should be noted that besides the influence of the ascend-
ing or descending direction, to which we shall refer below, the
current is most efficacious when passed longitudinally through the
nerve, least when passed transversely across it (Galvani, Albrecht).
Finally, the exciting action increases with extension of the intra-
polar length (Pfaff, v. Humboldt).
VI. The efficiency of external stimuli varies in the first place
with the excitability of the nerve, which differs very much not
only in different classes of animals, but also in different nerves of
the same animal, in different fibres of the same nerve, and, accord-
ing to some investigators, even in different parts of the same fibre.
Kitter and Eollett were the first to note that on exciting a frog's
sciatic with a current of minimum intensity the abductors and
flexors of the foot — i.e. the muscles innervated by the peroneal
nerve — were thrown into contraction ; while the adductors and
extensors — i.e. the muscles innervated by the branches of the tibial
—were only excited by stronger currents. This same holds good
for the flexor and extensor nerves of the toad and rabbit, and can
be shown not only with electrical but also with mechanical and
chemical stimuli. In the frog's vago-sympathetic trunk the
inhibitory fibres are excited by weaker currents than the acceler-
ators. Excitation of the nerve of the crab's claw with a very
weak current (see p. 35) causes the abductor of the claw to
contract ; with stronger currents this muscle relaxes and the
adductor contracts. Weak currents usually suffice to excite
nerves, but the nerve of the electrical organ of Malaptcrurus is
excitable to strong currents only, and is almost inexcitable to
chemical stimuli. Probably there are no two nerves in the same
animal with identically the same degree of excitability.
At first sight the degree of excitability in different parts of the
same nerve appears to vary. If a motor nerve, e.g. the frog's
sciatic recently divided from the spinal cord, is excited at different
points nearer to or farther from the muscle, the reaction of the
muscle is seen to be more vigorous in proportion as the stimulation
is more remote. Pfliiger explained this fact (first observed by
Budge) on the hypothesis that the nervous excitation produced by
the stimulus increased like an avalanche on its way to the muscle.
But this interpretation was at once disputed by Heidenhain, and
subsequently by Fleischl, Griitzner, Tigerstedt, and others. The
phenomenon must be due to the increase of excitability caused in
the upper part of the sciatic by the injury due to the section. When
the nerve remains as far as possible under normal conditions, it is
found to be equally excitable in its different parts to chemical
(v. Fleischl) and mechanical stimuli (Tigerstedt). The excitatory
impulse is more probably weakened than reinforced during its
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 225
propagation through the nerve, owing to the resistance encountered.
I'ucceschi in fact saw that on compressing the frog's sciatic lightly
by his method (Chap. IV. p. I',).0.) near the muscle, and then
tetanising it with an induced current alternately near the point
of compression and at the central end of the nerve, the conduction
of the impulse to the muscle ceased earlier from the more distant
points of excitation than from those nearer to the muscle.
Whatever the degree of excitability in the different nerves, it
can survive for a long time, independently of the circulation. If
care be taken to avoid desiccation and too sudden changes of
the normal temperature, the medullated fibres of mammalian
nerves are capable of preserving their excitability for many hours,
and those of the frog for many days, even when the circulation
has been entirely arrested.
The functions of nerves are usually supposed to be very
unstable and readily altered by slight causes. But it is easy to
demonstrate, on the contrary, that nerve, owing to its low meta-
bolism and specific differentiation, represents a form of living proto- i
plasm which is endowed with peculiarly high resistance to noxious \
influences. It is possible to experiment for a long time with a
mammalian nerve, after it has been isolated for a considerable
distance from the surrounding tissues and its circulation cut off,
without loss of its normal functions, provided it remains covered
and protected from heat and cold, and that circulation is normal
in the central and peripheral organs with which it is connected.
After occluding the aorta of a rabbit, the sciatic (according to
Frederic* [) is capable, on electrical stimulation, of causing the
corresponding muscles of the leg to contract, even after an interval
of half an hour. After three-quarters of an hour the contractions
cease for indirect stimulation, while the direct excitability of the
muscles still persists. This is due not to exhaustion of the nerve,
but to loss of conductivity in the motor end-plates. In fact even
w I it'ii the muscles have lost their excitability the nerves are still
alive and capable of excitability and conductivity, as is shown by
the negative electrical variation.
The most striking demonstration of the vital resistance of
nerve is, however, its comparative non-fatigability.
When a motor nerve is excited, the muscle apparently becomes
fatigued long before the nerve. This was demonstrated by
Bernstein in the following experiment : — Make two preparations of
the frog's sciatic ; cut them high up so as to separate them from
the spinal cord, to exclude sensations and reflexes : tetanise the
two peripheral stumps simultaneously with the same induced
current, and at the same time pass a strong constant current in
the ascending or descending direction through one of the two
sciatics below the point tetanised : this — by a polarising process
known as electrotonus, which we shall presently study — inhibits the
VOL. Ill (>
226 PHYSIOLOGY CHAP.
excitability and conductivity of the nerve, so that the transmission
of excitation to the muscle is prevented. The muscles of the first
sciatic will then be thrown into tetanus which lasts for some
minutes and gradually dies away, while the muscles of the second
(polarised) sciatic remain absolutely quiet. In order to show that
the absence of tetanus in the first case is not due to fatigue or
exhaustion of the nerve, it is only necessary to break the polaris-
ing current which blocks the second nerve. The corresponding
muscles are at once thrown into tetanus of the same vigour and
duration as that of the other side, showing that the nerve had
preserved its excitability intact during the protracted stimulation.
Schiff in 1858, by a method similar to that of Bernstein, arrived
at the same conclusion as to the great resistance of nerve to fatigue.
He applied the electrodes of a very weak battery, the circuit of
which was closed instantaneously every two seconds by the
pendulum of a clock, to the distal stump of the frog's sciatic, and
obtained a muscular twitch at each closure. If the electrodes of
a strong tetanising induction current were then applied to the
central end of the nerve the rhythmical contractions were replaced
by a tetanus that died out gradually, till finally it ceased altogether,
on which the muscle no longer reacted either to the intermittent
shocks of the battery or to the induced tetanising current.
Under these conditions it would seem as though the nerve were
exhausted, but proof to the contrary was shown in the fact that
directly the tetanising current was interrupted the rhythmical con-
tractions reappeared. To explain this fact Schiff' assumed that the
induced current produces a negative excitation, which was able to
neutralise the effect of the intermittent shocks.
Wedensky (1884) improved on the methods of Bernstein and
Schiff, and confirmed and extended their researches. He tetanised
the sciatic with an induced current of given strength and frequency
till the phase of apparent exhaustion was reached. On then re-
ducing the intensity and frequency of the current the tetanus
reappeared, showing, according to Wedensky, that the nerve was
not exhausted, but acted as an inhibitory nerve. The experiment
can be repeated many times upon the same nerve, always with
the same result.
This " paradoxical " phenomenon, viz. that a stronger or more
frequent stimulus produces less effect than a weaker or less frequent
stimulus, was satisfactorily interpreted by F. B. Hofmann, who in
1902-4 undertook a series of accurate investigations into muscular
tetanus from indirect stimulation. He refers it to fatigue of
the end-organs. The excitability of these is depressed after each
stimulation : recovery takes place after an interval which is longer
in proportion with the strength of the preceding excitation and
the degree of fatigue. If the stimuli are too strong, and follow
O O'
too rapidly, there is no recovery, and in excitability ensues ; if the
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 227
stimulus is weakened, or made less frequent, the reaction reappears.
Under normal conditions these effects of fatigue are manifested
only in muscle and particularly in the motor end-plates ; but we
shall see that under special circumstances the nerve trunk too may
exhibit similar paradoxical phenomena, so that the experiments
of Sclriff and Wedensky cannot be taken as a positive proof of
the non-fatigability of nerve.
The experiment of Bowditch (1885) is simpler and less
ambiguous. After curarising a cat, using artificial respiration,
he divided the sciatic and tetanised for a long time with an in-
duction current, which produced no effect upon the muscles of the
leg, owing to the paralysis of the motor end-plates. After two to
three hours of artificial respiration the paralysis induced by the
curare wears off, the animal gradually recovers, and the effects of the
excitation of the sciatic appear in the form of an irregular tetanus.
Lambert substituted atropine for curare, and was able to show the
non-fatigability of the secretory fibres contained in the chorda
tympani. After many hours of ineffectual stimulation of the
nerve the sub-maxillary gland began to secrete as the poison
disappeared gradually.
A more direct proof of the relative inexhaustibility of nerve
was given by Wedensky with the galvanometer and telephone.
He showed that the electrical phenomena (negative variation)
characteristic of functional activity undergo no perceptible altera-
tion after protracted stimulation ; and that two nerves excised
from the body, one being at rest, the other exposed to prolonged
stimulation, perished simultaneously.
These researches as a whole show that nerve fibres, unlike
other parts of the central and peripheral nervous system, exhibit
no signs of exhaustion, even after protracted activity : the fact that
a nerve is still capable of reacting to direct stimulation after the
response of the muscle had ceased proves — as Waller pointed out
—that the organs which connect the nerve with the muscle, i.e.
the motor end-plates, are much more easily fatigued than the
muscle and nerve. It is probable that the waste products developed
by the muscle during tetanus have some significance in the
production of exhaustion in the end-plates, as they may exert
a toxic action on the motor nerve -endings similar to that of
curare (Abelous).
This relative inexhaustibility is not, however, characteristic of
all nerves. Garten (1903) discovered a non-medullated nerve
(olfactory of pike) which readily becomes fatigued. On stimulat-
ing it with a series of induction currents at brief intervals, the
action current — observed by the capillary electrometer — diminished
after a few stimulations, but it increased again after a pause.
Even niedullated frog's nerve under abnormal conditions manifests
phenomena which cannot be interpreted otherwise than as fatigue
Ql
228 PHYSIOLOGY CHAP.
effects. Fr. W. Frohlich (1904), who made a long series of
accurate observations on this question, saw that, at a certain
stage of narcosis or asphyxia of the nerve, phenomena of apparent
inhibition set in which are perfectly analogous to those described
by Wedensky, and which Hermann referred to fatigue of the end-
organs. This paradoxical state, in which very strong and frequent
stimuli are less effective than weaker and less frequent stimuli,
can only be interpreted in these experiments as fatigue of the
part of the nerve which is exposed to narcosis or asphyxia. Such
manifestations of fatigue do not appear in nerve under normal
\ conditions, because the consumption of living matter is minimal,
I and recovery is extraordinarily rapid. They are manifested only
' when the restitution processes are much retarded by toxic or
other pathological influences.
Although under normal conditions nerve is practically inex-
haustible to prolonged artificial stimuli, so long as these do not
alter its substance, its specific activities (excitability and con-
Fio. 144.— Griinliagen's experiment on the effect of COo on a limited portion of a frog's
sciatic nerve. Explanation in text.
ductivity) may progressively diminish and eventually disappear
when it is deprived of the essential conditions of its existence.
Since nerve in atmospheric air shows no signs of fatigue even
after protracted activity, the question naturally arose as to how
far its functions depend upon the supply of oxygen, and how
much they are altered when indifferent or toxic gases are sub-
stituted for atmospheric air. The earlier investigations of Banke
and of Ewald (1867-69) are inconclusive ; they were incomplete
and yielded little result.
Ranke stated that a nerve (frog's nerve-muscle preparation)
suffers no injury in an atmosphere of carbonic acid, and that it
keeps its excitability longer in an atmosphere of hydrogen than
in one of oxygen. Ewald was unable to discover any difference
in the period of declining excitability, whether the nerve was
immersed in oxygen or hydrogen, or was in vacuo. He concluded
that its vitality is independent of its oxygen supply.
The experiment in which Grlinhagen allowed carbonic acid to
act not upon the entire nerve-muscle preparation of the frog, but
only upon a limited portion of the nerve, is more important. For
this purpose he introduced the nerve of the frog's leg into a glass
iv GENEEAL PHYSIOLOGY OF NERVOUS SYSTEM 229
tube which served as a gas chamber, and plugged the ends with
china clay saturated with isotonic salt solution. By using two pairs
of electrodes he was able to excite both the part of the nerve that
was being treated with CO., and the more proximal part outside
the gas chamber (A and B of Fig. 144). At a certain time after
passing the current of C02 into the gas chamber, stimulation of
the nerve at point A produced only a feeble response, which
gradually disappeared altogether; while stimulation at point B
was still fully effective. The impulse starting at B can therefore
be transmitted along the portion A of the nerve, in which excit-
ability has been depressed or abolished. This important experi-
ment is complementary to Waller's researches on the effects of
CO., on the electromotive response of nerve (Figs. 138, 139), and
proves that excitability and conductivity, while closely associated,
behave on artificial excitation as two distinct properties of the
nerve.
Griinhagen's experiments were continued by Luchsinger, and
more particularly by Piotrowski, who extended them to anaes-
thetics, and endeavoured to differentiate the action of the latter
upon the excitability and the conductivity of nerve, by means
of various forms of electrical and mechanical stimuli. He con-
cluded as follows :
(a) Carbon dioxide and carbon monoxide gases always produce
a marked depression of excitability in the intoxicated segment
without injuring conductivity.
(&) Alcohol vapour causes an initial rise of both excitability
and conductivity : later on the second decreases more rapidly than
the first, until a stage is reached in which excitations aroused
above the intoxicated portion are no longer conducted, although
the nerve is still perfectly excitable at that point.
(c) Ether and chloroform depress both excitability and con-
ductivity, but affect the former more rapidly and fundamentally
than the latter. Chloroform attacks the vitality of nerve more
powerfully than ether, so that its effects may become permanent.
Gotch also confirmed these results.
(cT) In all these experiments conductivity returns more rapidly
than excitability, when the action of these gases upon the nerve
is stopped.
The results of these and many similar experiments are
obviously unsatisfactory, and are far from giving any clear idea of
the relations between excitability and conductivity in nerve. The
work in Verworn's laboratory of his pupil Fr. W. Frohlich (1903)
has thrown more light on this subject. Frohlich found that on
anaesthetising or asphyxiating a tag of nerve its excitability
diminishes gradually and almost evenly, while conductivity — i.e.
excitability of the more central and uninjured parts of the nerve —
is at first unaltered, and then, when the excitability has fallen to
Q 2
230
PHYSIOLOGY
CHAP.
a certain point, suddenly disappears. Recovery takes place in the
same way ; excitability gradually rises, while conductivity suddenly
returns in its former proportions as soon as the excitability has
risen to its normal level (Fig. 145).
Von Baeyer (1902), in Verworn's laboratory, carried out
another series of researches on the effect of oxygen and the in-
different gases (nitrogen and hydrogen) upon the vitality of nerve.
By means of Griinhagen's method, which he improved in certain
details (Figs. 146 and 147), he established the following results,
which are complementary to those of his predecessors :
200
0
10
15
20
25
30
35
FIG. 145. — Diagram to show changes of excitability and conductivity in a motor nerve under the
influence of anaesthetising and asphyxiating agents upon a limited portion. (Fr. W. Frohlich.)
The abscissa line shows the time in minutes ; the ordinates, the distance in mm. of the coils at
which the minimal stimulus (single induction shock) takes effect.
(a) Under the direct asphyxiating influence of the indifferent
gases, the excitability of nerve disappears in three to five hours.
On substituting oxygen for these gases, normal excitability returns
after three to ten minutes.
(&) The physiological conductivity of the nerve is also abolished
by the asphyxiating gases, and recovered on adding oxygen.
(c) Asphyxia — loss of excitability and conductivity — spreads
along the nerve in a centrifugal direction according to the Hitter -
Valli law (infra) ; functional recovery when oxygen is supplied
seems, on the contrary, to be propagated in a centripetal direction.
(d) On raising the temperature of the nerve to 42-47° C. the
indifferent gases produce asphyxia in twenty to sixty minutes. If
the temperature be then lowered again to that of the surrounding
iv GENERAL PHYSIOLOGY OF NEKVOUS SYSTEM 231
atmosphere, and the current of indifferent gases continued for
twenty-five minutes, the nerve does not recover. P>ut if oxygen is
passed through the gas chamber there is a preceptible recovery in
three to six minutes, which becomes complete in a few moments.
These results show that the vitality of nerve depends on a
definite supply of oxygen. Its
comparative inex haustil tility
under normal conditions is due
to the fact that at ordinary
temperature, in presence of
atmospheric air, it obtains all
the oxygen essential to its
functions. As we have seen,
both v. Baeyer and Frohlieh
demonstrated unmistakable
phenomena of nerve - fatigue
in an atmosphere deprived of
oxygen.
Von Baeyer's experiments
were extended and completed
by Fr. W. Frdhlich (1903), who
found that asphyxiated and
anaesthetised nerve is incap-
able of recovery by assimilating
oxygen, confirming the results
of Hans Winterstein for nerve-
centres (infra'}. Frohlich then
studied the effects of duration
of oxygen supply on. the re-
covery of asphyxiated nerve.
With prolonged passage of
oxygen he found an initial
rise of excitability up to the
normal height; a further supply
of oxygen produced no further
rise of excitability, but in-
creased the duration of a second
asphyxia.
Von Baeyer's experiments
were repeated by Boas (1904),
\vho placed the nerve in an atmosphere of pure hydrogen and
in vacua, with the same results.
Thunberg (1904) showed that the consumption of oxygen and
production of carbonic acid in nerve can be demonstrated directly
by chemical analysis. By means of a micro-respiratory method he
was able to measure oxygen intake and carbonic acid output from
excised bits of rabbit's nerve.
FIG. 146. — Von Baeyer's method of demonstrating
the effect of gases on a length of nerve. «,U-tul>e
ending in a bulb with a little water to saturate
the gas passing through it ; the tube is enclosed
in a kind of water-bath by which tin- 1 i-mp.'iature
of the gas can be raised as desired ; b, gas
chamber into which the nerve is introduced
through the side aperture <', and where it can
be excited by means of platinum electrodes
soldered in at <l ; e, vent for gas ; /, rubber cork
through which the bulb of a thermometer can
be introduced into the chamber.
232
PHYSIOLOGY
CHAP.
Another important condition of the vitality of nerve lies in
its anatomical continuity and connection with its central organ.
A long series of well-established facts proves that when this
connection is interrupted its normal nutrition and morphological
structure are altered, as well as its excitability.
When a nerve, e.g. sciatic, is divided at any point of its course,
there is at first a considerable rise in excitability, particularly near
the point of section (Rosenthal), which is due to the electromotive
changes developed there (demarcation current). This rise dies
away after a certain time, and gives place to a gradual decrease,
and, finally, the total loss of excitability in the nerve.
According to a law formulated by Valli and confirmed by
Bitter the depression and loss of excitability, both in the excised
FIG. 147.— Gas chamber of v. Baeyer's apparatus, with unpolarisable brush electrodes instead
of those shown in preceding figure. The letters ?ill e\, il\, e\, J\ have the same meaning as
b, <; d, K, /in previous figure.
0
nerve and in that which is only divided, begin at the proximal end
and progress centrifugally towards the periphery. Experiment
shows in fact that when excitability is exhausted in the proximal
parts the nerve is still capable of excitation in more peripheral
regions. Complete disappearance of excitability in the entire
trunk of the sciatic occurs four days after section in the clog
(Longet), two days in the rabbit (Eanvier), two days and a half
in the pigeon (Waller). In poikilothermic animals in general
excitability lasts much longer ; it varies considerably with the
season and with the general conditions of nutrition in the animal
experimented on. In the frog, during the winter season, the
excitability of the cut sciatic persists for thirty-three days after
section (Brown-Sequard).
Before this gradual depression and loss of excitability in the
centrifugal direction is completed, a characteristic degenerative
change begius in the divided nerve, which is coupled after a few
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 233
days with an opposite regenerative process. This finally leads to
the gradual recovery of function in the nerve, and so of sensibility
and motility in the region which it innervates.
These morphological studies of the degeneration and re-
generation of nerves severed
from their centres were
begun by Steinbriick (1838),
Nasse (1839), Giinther and
Schon (1840) ; but they only
acquired significance after
the discovery of the so-called
trophic centres of the spinal
roots by Augustus Waller iu
1852.
We must here confine
ourselves to a summary of
the changes produced by
severing the fibres of a mixed
peripheral nerve from their
trophic centres. Two to four
days after section the whole
peripheral part of the nerve
and a short length of its
central portion (according to
Engemiann to the nearest
node of Ranvier, but accord-
ing to other authors as far
as the second or third node)
begins to undergo a process
of degeneration, which is
easily traced under the micro-
scope, and which leads to the
disintegration of the fibres.
It is usually held that the
degenerative process does not
advance progressively from
the seat of the lesion towards
the periphery, but that it
appears simultaneously
throughout the whole distal
FIG. 148. — Degeneration and regeneration of nerve-
libres. (Ranvier.) A, rabbit's sciatic four days
after section; B, C, the same fifty hours after
section ; D, fibre stained with carmine only, to
show axis - cylinder ; F, (~f, pigeon's fibres three
days after section ; H, two fibres of rabbit's vagus
six days after section ; J, lymph cell from inter -
tibrillary connective tissue, containing ingested
globules of myelin. Throughout the figure, n, n,
are nuclei ; x, x, myelin broken up by increase
of the protoplasm ; etc, axis - cylinder ; K, L, re-
generation of nerve-fibres ; H, of rabbit's vagus
seventy-two days after section ; L, of rabbit's
sciatic ninety days after section ; e, conical ending
of white matter of central end of the nerve ; s,
sheath; na, new axis -cylinder. L shows two
globules of myelin left over from the degeneration
of the old fibre.
portion. The rapidity of the
degenerative process is greater in young than in old animals,
in strong than in weak, in warm-blooded than in the cold-
blooded.
The most apparent change occurs in the myelin sheath of ,
the fibres, which undergoes progressive fragmentation till it
is reduced to small irregular lumps or drops. Along with this
234 PHYSIOLOGY CHAP.
morphological alteration there is n chemical metamorphosis of
the rnyelin which, probably owing to the formation of fat, now
stains black with osmic acid, after the nerve lias been mordanted
in a chrome solution. Marchi's method of distinguishing between
the healthy and the degenerated nerve-fibres is based on this
chemical change of the myelin sheath (Fig. 148, A-J").
Many hold, on the strength of Eanvier's studies, that the
fragmentation and fatty degeneration of the myelin is accom-
panied by a multiplication of the nuclei of the neurolemma,
and increase of its protoplasm, which interrupts the continuity
of the medullary sheath. The axis-cylinder, too, is broken up
by the same process as the myelin, i.e. by increase of the
protoplasm at the level of the nuclei of the interannular segments.
But according to the recent and more accurate work of Bethe
and Monckeberg the degenerative alteration of the axis-cylinder
precedes the other changes, and takes place pari passu with the
diminution and loss of excitability in the nerve. First, the
fibrils of the axis-cylinder stain less readily ; next, they fuse
into a compact cord, which looks knotted in places, and also
shows large fusiform nodules ; lastly, they break up and then
dissolve into a detritus of colourless granules. The acute period
of the degenerative process is followed by a slow fetage, in which
the products of disintegration are absorbed (by phagocytosis ?)
so that they entirely disappear after three to four weeks. When
clear of the degeneration products the fibres of the nerve are
seen as strands filled with large fusiform elements, which are
derived from the cells of the neurolemma. What part do these
spindle-shaped elements play in the regeneration of the nerve ?
The regenerative process in the divided nerve proceeds to a
large extent along with the degenerative, to which it is the active
reaction, directed to the morphological and functional recovery
of the injured nerve.
There are two principal theories to explain the process of
nerve regeneration, which are related to the two fundamental
conceptions of the morphological structure of the nervous
system discussed earlier in this chapter.
In correspondence with the neurone theory, many authors
hold that the regeneration of the axis-cylinders in the peripheral
end of the cut nerve is due exclusively to an outgrowth of the
axis-cylinders of the central end. These increase in size, become
bulbous at their extremities, and send out fibrils in a centrifugal
direction, which pierce the cicatricial tissue that has united
the two stumps, and then penetrate the old neurolemmal sheaths,
or grow along them until they reach their peripheral termination.
Ranvier, Vanlair, Strobe are the chief promoters of this theory
(Fig. 148, K,L}.
The other conception of the regenerative process in nerve
iv GENEEAL PHYSIOLOGY OF NERVOUS SYSTEM 235
corresponds with the theory which regards a ganglion cell and
its processes, not as a morphological and functional unit, but
as a syncytium, i.e. the result of the fusion of a number of
neuroblasts arranged in a chain. On this hypothesis the cells
of the neurolemma represent the residues of the neuroblasts
from which the nerve -fibres originated, and after section of
the nerve they reassume their character of neuroblasts by
multiplying and hypertrophying in the form of spindle-shaped
embryonic cells, and regenerate the nerve-fibre discontinuously
and simultaneously in the different parts of the cut nerve. This
theory is supported by Benecke, Tizzoni and Cattani, Huber,
v. Biingner, Galeotti and Levi in particular, and it has been
reinforced by recent morphological and experimental observations
of Bethe.
Bethe, unlike the earlier workers, prevented the two stumps
of the divided sciatic in dogs and rabbits from joining, and
examined the peripheral stump six to nine months later by
physiological and histological methods. When the experiment
was carried out on adult animals he noted an increase of
protoplasm in the neurolemma, with differentiation into an
axial filament and a peripheral sheath, but was unable to detect
fibrils in the former or niyelin in the latter. The nerve was
thus partially regenerated, but was found on stimulation to be
inexcitable and incapable of conducting.
Bethe obtained different results on experimenting with young
animals, in which the regenerative capacity of the tissues as
a whole is much greater. Of four young dogs and one rabbit
operated on he observed in 3 cases not only complete morpho-
logical regeneration, but also functional recovery of the isolated
peripheral nerve (i.e. one not reunited with the central stump).
On stimulating with induced currents that were too weak to
produce direct excitation of the muscle, the leg muscles were seen
to contract freely.
Laugley and others, however, objected to Bethe's conclusions
that this was not a true autogenous regeneration of the nerves,
and that the regeneration of the peripheral stump must depend
on its uniting with the central end of other adjacent nerves
that had been divided in the operation. The .tendency mani-
fested even by nerves that are situated at a distance, and that
supply other muscles, to unite with the peripheral ends of cut
nerves, so as to re-establish the conductivity of the fibres, is
in fact very marked. This enigmatical fact, that nerve -fibres
emero-in^ from the centre and in normal connection with it
o o
grow towards peripheral organs that have been denervated, has
been attributed by some neurologists who deny autogenous
regeneration to a kind of neurotaxis, i.e. to the capacity of
denervated organs to attract the nerve-fibres that grow towards
236 PHYSIOLOGY CHAP.
the periphery (perhaps by chemical stimuli deriving from the
degenerative processes).
Some remarkable experiments have recently been carried out
upon the embryos of various cold-blooded animals with a view
to solving the origin of nerve - fibres. The results cannot,
however, be taken as conclusive for either theory. Such are the
experiments of Braus and Banchi (1905), who transplanted limb
buds into the bodies of tadpoles, and the observations of 0.
Schultze (1904-5) on the histogenesis of the peripheral nerves
in tadpoles. These yield data that decidedly favour the
autogenous theory. On the other hand, Harrison (1904-6) found
in amphibian larvae that after excising the neural crest, from
which all the cells of Schwann for sensory and motor nerves are
FIG. 149. — Diagrammatic. Regenerative changes at the central end of a nerve-fibre, close to the
section. (Perroncito.) a, normal axis-cylinder composed of a bundle, of fibrils; b, swelling,
from or above which the regenerating fibres grow out ; c, portion of axis-cylinder undergoing
degenerative changes, close to the section ; <l, d", young fibrils sprouting from the axon, which
leave the nerve-fibre through the neurolemma ; d', new fibres running backward in a spiral ;
e, fi Oi Q'I 9"> ''i h', h", different forms of buds and regenerating fibres.
derived, the axis -cylinders still develop, but remain destitute
of sheaths.
When, in 1900, it was still possible — in the absence of specific
histological tests — to question the existence of the regeneration
of axis-cylinders in cut nerves, Purpura examined them with
Golgi's silver nitrate method and obtained decisive results. At the
extremity of the central stump of a divided nerve, between the
normal medullated fibres, he observed the presence of nude axis-
cylinders that stained black and were associated with a number
of ramifying varicose nerve - fibrils, of a markedly embryonic
character. These fibrils invaded the cicatricial tissue between
the two stumps, running through it in all directions, and
interlacing in a most complex fashion. At a later period the
peripheral stump is also invaded by fine branching nerve-fibrils,
which differ from those which run in the scar by following a
longitudinal course between the residues of the old degenerated
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 237
fibres. Purpura holds that the newly found fibrils come from
the central end of the nerve, and, in fact, from the old axis-
cylinders. At a later stage, in place of the fibrils and arranged
like them, bundles of medullated nerve-fibres are found in the
cicatrised tissue and in the peripheral stump.
Lastly, A. Perroncito (1908) made a careful histological study
of the regeneration of cut nerves, using particularly Ramon y
Cajal's photographic method. He too concluded that the re- .
generation of nerve-fibre is exclusively the work of the central \
stump. He brought out the remarkable fact that, regenerative
changes in the fibrils occur within a few hours of the injury in
the central end of cut nerve, far more rapidly than was formerly
supposed. The regenerative process is manifested by a numerous
FIG. 150.— Three nerve-fibres from central end of do.^'s sciatic at different periods after section.
The axon shows different forms of regenerating fibrils. (Perroncito.) The upper fibre comrs
from a nerve divided six hours, the centre fibre seventeen hours, the lowest fibre forty-eixht
hours previous to preparation.
and varied formation of fibrils, derived from the central stumps
of the axis-cylinders which had degenerated for a greater or less
distance (but never more than a few millimetres) from the point
of section. This degeneration ceases at a point of the fibre which
does not, according to Perroncito but contrary to the opinion of
others, correspond with a node of Ranvier: at this point the
end of the axis -cylinder a few hours after section exhibits a
fusiform or cylindrical swelling, in which a fibrillary structure
is quite apparent (Fig. 149). The formation of new fibres, most
of which as they grow advance towards the periphery, proceeds
rapidly from this swelling or the part of the axis - cylinder
immediately above it. Some force their way through the neuro-
lemma into the old fibres. All of them exhibit characteristic
bulbous or spiral endings (Fig. 150). Twenty-four hours after
the lesion, in young animals, these regenerated prolongations have
already passed the confines of the old central stump, and penetrated
238
PHYSIOLOGY
CHAP.
the blood-clot of the wound and the clumps of leucocytes found
at the extremity of the central stump of the cut nerve.
During the third or fourth days after section the process of re-
generation proceeds no less rapidly ; the central end is surrounded
by a mass of newly formed connective tissue which is permeated
%-, #fefeg§S5=3S?%S
'r* 'i-«f>-< • '- -• it Jf ^.' ~ • f^f~i-~f-^m.7 — -v^
^^^s^^^^^^^^^^^s^^^
FIG. 151. — Extreme end of central stump and portion of cicatrix (semi-diagrammatic) twenty
days after section. (Perroncito.) The regenerated fibrils from the nerve-fibres of the central
stnmp in the first zone of the cicatrix interlace and run in all directions ; in the next zone they
niaUf a number of spiral formations ; lastly, they form a fibrillary interlacement like a network,
which fills flip middle part of the cicatrix. This apparent network again gives rise, in the
outer part of the cicatrix, to slender bundles of new fibrils, which run singly in the longitudinal
direction, and begin to reconstitute the peripheral part of the divided nerve.
in all directions by a great number of new fibres that run mainly
along the axis of the old nerve. Twenty to thirty days after the
section the regenerating fibres travelling towards the peripheral
stump are once more, to a large extent, made up into definite
bundles, while the spiral regenerative formations have attained
their maximal development (Fig. 151). Thus we have an
iv GENEEAL PHYSIOLOGY OF NERVOUS SYSTEM 239
anatomical recovery of the cut nerve, since the newly formed
nerve-fibres, after passing through the cicatrised tissue and
repeatedly dividing into branches, rejoin the peripheral stump
and run through it, between the old degenerating fibres. The
newly formed nerve-fibres, including even the most delicate, are
invariably continuous from the outset, as if there were no
formation of nerve-fibres other than those coming from the
central stump of the cut nerve.
Perroncito observed that, while the functional recovery of the
nerve was intimately connected with the scar formation, it may,
under certain conditions, be independent of it. He saw, for
FIG. 152. — Dog in which all the IUTVCS of the right hind-leg were destroyed. After some months
it showed no defect in progression. (Purpura.)
example, that the conduction of electrical excitation reappears
earlier in the peripheral part than at the scar, which would
explain Bethe's experimental results. He brings out the fact that
functional recovery is not exclusively and necessarily associated
with anatomical regeneration since it can be simulated by the
existence of collateral nerve paths.
Sometimes, particularly in young animals, Purpura noticed a
rapid and more or less complete functional recovery, which he
attributed to a process of collateral compensation. In all cases
in which he observed slow functional recovery he attributes this
to regeneration of the nerve-fibres. To ascertain whether the
more rapid recovery is due to collateral paths, Purpura operated
on puppies by cutting all the nerves to the hind -limb, and
obtained complete, though retarded, return of function, i.e. of
perfect co-ordination in walking, as partially shown in Fig. 152.
In addition to his experimental investigations into the
240
PHYSIOLOGY
CHAP.
functional recovery of a cut and sutured nerve, Purpura made
some interesting clinical applications of his conclusions on nerve
regeneration. He demonstrated the possibility of recovery of
function on crossing two different nerves. In a patient affected
with facial paralysis, which resisted medical treatment (Fig. 153),
he made a crossing of the outer branch of the spinal accessory
nerve with the facial (May 1909). Forty days after the operation
a slight correction of the facial asymmetry was perceptible ; after
two and a half months it was practically cured (Fig. 154). At the
close of 1909 the invalid besun to exhibit associated movements
o
FIG. 153.— Complete paralysis of left facial nerve previous to operation. (Purpura.)
of the shoulder and the muscles innervated by the facial. In the
early months of 1910 the movements were associated when they
were sharp and sudden, but the patient was able to dissociate
them when she fixed her attention on them. By the second half
of that year she was always able to dissociate them.
More recently (1910) Modena instituted histological investiga-
tions with Donaggio's method upon the regenerative phenomena
in divided nerve, and his results agree fundamentally with those
of Purpura and Perroncito.
VII. Special interest, from both the theoretical and the
practical standpoint, attaches to the study of the changes which
the nerve undergoes when any part of it is exposed to the action
of a constant current. These changes appear as physical electro-
motive and physiological phenomena, and consist in profound
alterations of the excitability and conductivity of the nerve.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 241
The former were discovered in 1.843 by Du Bois-Reymond, who
gave the name of electrotonus to the special electrical state produced
by the passage of a galvanic current, in both the intrapolar and
the extrapolar parts of a nerve. The latter, which were accurately
described by Pfliiger in 1859, are more properly termed electro-
tonic alterations of the excitability and conductivity of nerve.
Both these effects are in reality manifestations of the chemical
phenomena of electrolysis and polarisation.
We know that the passage of a galvanic current through a
moist conductor is accompanied by phenomena of electrolysis and
FIG. 154. — Correction of the facial paralysis two and a half months after the crossing of the
external branch of the spinal accessory with the facial. (Purpura.)
dissociation, which reach their maximal development at the
points of entry and exit of the current, i.e. at the electrodes.
When the current passes through a moist conductor, the presence
of electrolytes (i.e. the molecules of a neutral salt in solution)
renders the fluid acid at the anode and alkaline at the kathode
owing to the transport of the acid negative ions to the positive pole,
and of the basic positive ions to the negative pole of the current.
If after a prolonged passage of current through the fluid the
electrodes are disconnected with the cell and connected to a
galvanometer, a so-called " polarisation current " is seen in the
opposite direction to the polarising current ; this is due to the
accumulation of positive ions at the kathode and negative ions at
the anode of the polarising current.
Since nerve is a moist conductor, the passage of a galvanic
VOL. Ill R
242
PHYSIOLOGY
CHAP.
current through it must be accompanied by these polarisation
phenomena.
When metal electrodes are applied to a nerve, the principal
seat of polarisation is the surface of contact of the electrodes
with the fluids of the nerve, which is therefore called external
polarisation. The intensity of this polarisation can be reduced
by employing currents of very brief duration (induced currents),
alternating in direction, and of approximately equal strength
(sinusoidal currents). It can be practically abolished by using
unpolarisable electrodes (see Fig. 45, p. 71).
When a current is passed through a nerve by means of
unpolarisable electrodes, so that external polarisation is abolished,
internal polarisation, so-called, will still be manifested; it is
specially conspicuous in nerves with medullated fibres, and arises
from their peculiar structure. In this case, too, the electrolytic
Nerve.
Anelectrotonic.
current.
Polarising
current.
Katelectrotonic
current.
FIG. 155.— Diagram of electrotonic currents, to show polarising current thrown into median
portion of an exposed nerve; anelectrotonic current led on' to galvanometer from anodal
portion ; katelectrotonic current led off to galvanometer from kathodal portion of the
nerve. (Waller.)
effects of the passage of current are more pronounced at the
poles, i.e. at the points of entrance (anode) and exit (kathode] of
the current, whence they spread with diminishing intensity, not
only in the intrapolar, but also in the extrapolar parts of the
nerve. The displacement of the electrolytic products or ions in
the direction of the poles during closure of the current is shown
in the intrapolar tract by a rise of electrical resistance (diminished
current intensity) and in the extrapolar tracts by electrical
currents which are in the same direction as the polarising current
when led off to the galvanometer (Fig. 155). These currents are
known as anelectrotonic currents in the extrapolar tract corre-
sponding to the anode, and katelectrotonic currents in the part
corresponding to the kathode.
The strength of the electrotonic currents increases with the
strength of the polarising current, with diminished distance
between the galvanometer electrodes and those of the cell, lastly,
with increased length of the intrapolar tract. They do not
appear when the polarising current is passed transversely through
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 243
the nerve ; when the nerve is tied, bruised, or its physiological
conductivity in any way interrupted ; and when the nerve is
degenerated, exhausted, or dead.
Anelectrotonic are stronger than katelectrotonic currents ; the
former gradually increase during the passage of the polarising
current, while the latter gradually decline. On cooling, both
decline to the point of total disappearance. The maximum
intensity of the electrotonic currents may exceed that of the
demarcation currents by more than twenty-five times.
Electrotonic currents alter in direction when the polarising
current is reversed ; they persist during the whole time of the
passage of the polarising current, and their intensity decreases
along the extrapolar tracts in proportion with the distance from
the poles. These characters distinguish the electrotonic currents
sharply from the action currents, which, as we have seen, are
constant in direction, and arise from the active state or excitation
rdh
LJ
FIG. 156.— Diagram of the electrotonic currents which summate algebraically with the
demarcation currents in a length <>t' rxcised nerve. (Luciani.)
of the nerve, independently of the nature of the stimulus, and of
the direction of the exciting current when an electrical stimulus
is employed.
When the polarising current is sent into an excised nerve, from
which demarcation currents can be led off to the galvanometer,
these summate algebraically with the electrotonic currents, which
are accordingly reinforced if in the same direction as the demarca-
tion currents, — weakened or reversed, if the latter are in the
opposite direction (see Fig. 156). These phenomena were
formerly known as the positive and negative phases of electrotonus,
an unfortunate expression as the electrotonic phenomena are
entirely independent of the demarcation currents.
The fundamental phenomena of electrotonus can be reproduced
on very simple models. As early as 1863 Matteucci observed
that the electrotonic currents in both intrapolar and extrapolar
portions of the nerve can be demonstrated in all essential
particulars if the galvanic current is led through a platinum wire
surrounded by a porous sheath saturated with fluid, instead of
through a nerve. Hermann, Griinhagen, Hering confirmed
Matteucci's observations by means of slightly different models.
244 PHYSIOLOGY CHAP.
Hermann's model consists of a glass tube containing a platinum
wire, which makes a good conducting axis. The tube, closed at
the ends, is rilled with a saturated solution of zinc sulphate, which
forms a moist, less well-conducting sheath for the axis. A pair of
zinc electrodes are fastened to the tube, which are in contact with
the solution, and serve as the polarising and galvanometer contacts.
The electrolytic polarisation which takes place during the passage
of the current between the surface of the metallic core and
the solution, and drives the kathodic ions towards the anode and
the anodic ions towards the kathode, generates a resistance to the
passage of the current through the intrapolar portion by which
its longitudinal diffusion in the extrapolar parts is promoted.
Both in the nerve and in Hermann's model, polarisation or
post-electrotonic currents are produced on breaking the polarisa-
tion circuit. These are opposite in direction to the electrotonic
currents, and are due to the accumulation of ions with the opposite
charge at either pole of the battery. The reversal of current at
the close of electrotonus was demonstrated on nerve by Pick, but
according to Hermann it is definite only in the anelectrotonic
region.
Notwithstanding the analogy between the electrotonic pheno-
mena in nerve and those which can be reproduced in the core-
model, there is no doubt that the former depend not only upon
physical conditions, but also upon the anatomical and physiological
integrity of the nerve.
Biedermann pointed out the differences between the electrotonic
phenomena in normal and in etherised nerve. In a normal nerve
traversed by a polarising current the extrapolar electrotonic effects
from two points ecpuidistant from the poles are not equal on the
galvanometer. In one case Biedermann found that anelectrotonus,
as expressed by the deflection of the galvanometer needle, was
equal to 46 and katelectrotonus to a deflection of 25 ; on
increasing the strength of the polarising current he obtained
anelectrotonus of 96, katelectrotonus of 60. On etherising the
nerve these differences disappeared ; with the first current the
galvanometer deflection was 24 in both the anodic and the
kathodic region ; with the second current it was 68 for the former,
66 for the latter. Biedermann took these results obtained with
etherised nerve to be the expression of the physical electrotonus
due to polar electrolytic effects, and those obtained with normal
nerve to be the expression of physiological electrotonus due to
special vital conditions which make anelectrotonus more pro-
nounced than katelectrotonus. He further showed that the effects
of anelectrotonus spread over a larger area in normal than in
etherised nerve.
These observations of Biedermann are supported by Waller,
who found that anaesthetics, and. all agents in general that
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 245
influence the electrical reaction of nerve, are also capable of
temporarily suppressing electrotonus.
Besides the electrotouic phenomena strictly so-called, polarising
currents evoke other parallel specific changes of excitability and
conductivity in both the intrapolar and the extrapolar portions of
the nerve. We owe our knowledge of the principal phenomena
of this subject to Pfliiger, who followed up the earlier researches
of Bitter, Nobili, Matteucci, Valentin, and Eckhard. The main
facts in regard to the electrotonic changes of the excitability of
nerve are as follows :—
(«) The passage of a constant current through a nerve causes a
s.c.
Fio. 157.— Diagram to show electrotonic modifications of excitability, according to ascending or
descending direction of polarising current. (Waller.) p.c., polarising current ; s.c., exciting
current : HI., muscle. In the upper diagram the direction of the polarising current is ascending,
and excitability is therefore lowered in the anelectrotonic region ; in the lower diagram the
direction of the polarising current is descending, and excitability is therefore raised in the
katelectrotonic region of the nerve.
rise of excitability at the kathode and a fall of excitability at the
anode.
(&) These changes in excitability are most marked at the poles,
but they also spread into the intra- and extra-polar regions,
Crowing weaker. There is in the intrapolar portion an indifferent
point, at which excitability remains unaltered.
(c) When the current that sets up electrotonus ceases the
alterations of excitability are reversed; the kathodic region
becomes less excitable, the anodic region more so.
The nerve -muscle preparation of the frog is generally used
in experimental demonstration of these electrotonic changes in
excitability. According as the polarising current is passed in an
ascending or a descending direction through the nerve, the
anelectrotonic or katelectrotonic region will be found nearer- the
muscle. In order to show that excitability is depressed in the
former and raised in the latter, the nerve is excited near the anode
or kathode respectively, either by an induction current (as in Fig.
246
PHYSIOLOGY
CHAP.
157) or with mechanical or chemical stimuli. The strength of
the muscular response, recorded on a revolving cylinder, is found
to be diminished when the nerve is stimulated in the region of the
anode, increased when excited near the kathode.
A curve of the katelectrotonic and anelectrotonic alterations
of excitability corresponding with the kathodic and anodic regions
can be constructed by comparing the muscular responses obtained
by exciting different parts of the anodic and kathodic regions.
The form and height of the negative and positive excursions of
this curve alter, according to Prluger's comprehensive researches,
with the strength of the polarising current, and the degree of
excitability of the nerve experimented on. It is further found
that when the polarising current is weak the indifferent point in
the iutrapolar tract lies near the anode, and in proportion as the
FIG. loS. — Diagram of electrotonic changes of excitability in the infra- and extra-polar portions of
the nerve. (Pfliiger.) a, position of anode ; /,-, position of kathode ; a, k, intrapolar portion.
The three curves, j/j, //.,, i/:i, represent the electrotonic effects of weak, medium, or strung
currents. The .points, .1], .1-.',, ,>.,. show the relative position of the indifferent points with tin-
three currents. The portions of the curves below the abscissa express the anelectrotonic
diminution of excitability ; the portions of the curves that rise above the abscissa express the
katelectrotonic increase of excitability.
strength of the current increases it shifts towards the kathode.
All these facts are represented in the diagram of Fig. 158.
Griinhagen's researches show that both the kathodic rise and
the anodic fall of excitability occur at the poles without any
appreciable delay after closure of the circuit. The electromotive
effects due to polarisation, on the contrary, appear in the im-
mediate vicinity of the poles at an interval of O001 sec. after
closure of a very brief current.
On the strength of the facts at present known the electro-
motive effects and electrotouic alterations of excitability appear
not to be strictly synchronous. But seeing the parallelism of the
two classes of phenomena, it is natural to surmise that there is a
close connection between them, and probably a relation of cause
and effect.
The alterations of excitability that occur on breaking the
polarising circuit must be regarded as the effects of recovered
equilibrium in the nerve. The anodic rise and kathodic fall of
excitability begin at the poles and spread thence to the peri-
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 247
pheral regions. The anodic effect is more pronounced than the
kathodic.
Conductivity is also affected by the passage of the polarising
current. When the central portion of a nerve is excited by an
electrical stimulus of minimal intensity, and the galvanic current
then passed through its peripheral part, the muscular reaction
diminishes or fails altogether. This effect persists for a short time
after opening the current.
The electrotonic decrease of conductivity is greater in propor-
tion to the strength and duration of the polarising current. It
appears to be associated with the fall of excitability at the anode
on closing the circuit, which is not compensated by the rise of
excitability and conductivity at the kathode. This can be
demonstrated as follows : A polarising current is sent through the
s.c.
FIG. 159. — Diagram of tripolar application of polarising current to nerve. (Danilewsky.)
s.c., exciting current ; m, muscle ; a, k, lateral electrodes joined together, connected with
kathode ; c, central electrode connected with anode.
frog's nerve-muscle preparation by means of three electrodes (as
shown in Fig. 159), the two side electrodes being connected with
the kathode of the cell and the middle electrode with the anode.
In this case the katelectrotonic effect prevails over the auelectro-
tonic, because the kathodic region is more extended than the anodic.
If a point of the nerve remote from the muscle be now excited the
response of the muscle is greater than usual, owing to the kat-
electrotonic rise of excitability and conductivity. If the experi-
ment is reversed by putting two positive electrodes at the sides
and one negative in the middle, the opposite result appears, i.e.
the response of the muscle is less than normal, owing to the
preponderance of anelectrotonus over katelectrotonus.
The polar electrotonic changes affect not only the amplitude
of the reaction, but also the velocity of conduction. On closing
the polarising circuit there is acceleration at the kathode and
delay at the anode, except where the effects at the two poles are
in perfect equilibrium, when the rate of conduction remains
243
PHYSIOLOGY
CHAP.
unaltered. The reversed polar changes on opening the circuit
also affect the rate of conductivity ; in the region in which
excitability is increased conductivity is also accelerated.
All these data in regard to the polar effects of the constant
current are founded on experiments specially made on frogs' nerves.
Many workers since Helmholtz have attempted to reproduce the
same electrotonic phenomena upon man, but the results have been
variable and uncertain. Waller and De Watteville alone succeeded
in showing that electrotonus follows the same laws in man as in
other animals, the only difference being that the polar changes are
less marked with different modes of sending in the current.
VIII. In speaking of the polar changes of excitability and
conductivity in nerve during the passage of a constant current
we have confined ourselves to the excitatory influence of this
current upon the nerve at make and break, i.e. when its action
upon the nerve begins and ceases. These excitatory effects are
expressed in the muscular contractions that occur at these two
moments. According to the strength of the polarising current,
and its ascending or descending direction in the nerve, it is
possible to obtain break as well as make contractions, or break or
make contractions only. The regular order in which these signs
of nervous excitation occur, and the explanation of their occurrence
by the laws of electrotonus, constitute what is known as " Pfliiger's
law of contractions," as in the following table : —
Ascending Direction.
Descending Direction.
Strength of
Gum-lit.
Closing.
Opening.
Closing.
Opening.
Weak
Weak contrac-
Weak contrac-
tion
tion
Medium
Strong con- Weak contrac-
Strong con-
Weak contrac-
traction tion
traction
tion
Strong
Weak contrac- Strong con-
Strong con-
Weak contrac-
tion
traction
traction
tion
Very
Strong con-
Strong con-
strong
traction
traction
These experimental data, which together constitute the Law of
contractions, are expressed in the diagram of Fig. 160.
The results obtained with weak and moderate currents are
readily interpreted if we assume with Pfliiger that they depend on
rise of excitability in the nerve at the kathode (katelectrotouus),
which takes place so abruptly on closure of the circuit that it
causes excitation, no matter what the direction of the current may
be. The anodal rise of excitability which occurs on opening the
circuit, owing to the disappearance of anelectrotonus, is less
effective than the kathodal rise at closure. This explains why the
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 249
break of weak currents produces uo excitation, and why at break
the contraction is relatively less marked with moderate currents
than it is at make.
The excitation caused by stimulating with strong or very
strong currents requires a more elaborate explanation. In this
case, also, the nerve is excited at the kathode at make and at the
anode at break of the circuit. The excitation, moreover, increases
in proportion to the strength of the current. But for a motor
Ascending cmivnts Descending currents
t !
Wrak r I - SAS \ \ Weak
Medium I I 5MB SHfi 9 ' Medium
Strung C \ SM 5BS BBB 1 Strong
strong strong
t I t 1
Make Break Make Break
Fi(3. 160. — Pfliiger's Law of Contractions.
nerve, the kathodal excitation at make with an ascending
direction of current must, in order to reach the muscle, pass
through the auodal region, in which — as we have seen — con-
ductivity is greatly depressed. This explains why in such a
case the make contraction is either very feeble — with strong
currents, or fails altogether — with very strong currents. So, too,
the anodal excitation at break, in order to reach the muscle,
must with a descending current traverse the kathodal region, in
which (owing to the disappearance of katelectrotonus) conductivity
is much diminished. This explains the weak contraction that
appears at break of strong descending currents, and which may
fail altogether when very strong currents are employed.
250 PHYSIOLOGY CHAP.
The same law of contraction applies to sensory or afferent
nerves. In this case the reflex muscular response is taken as
the measure of excitation in the nerve. Here the results must
of course be inverted, the reflex contractions excited from sensory
nerves with ascending and descending currents following the
law of motor nerves for the descending or ascending currents
respectively.
The expressions adopted in the formula of the law of con-
traction, of weak, medium, strong, or very strong currents, have
only a relative value, since the local phenomena of excitation due
to polar changes depend not only on the strength, direction, and
duration of the current, but also on the initial excitability and
the length of nerve traversed by the current. It has been shown
that polar electrical stimulation is more effective as the electrodes
are further apart, because the changes in the equilibrium of the
nerve are so much the more difficult to compensate.
All the phenomena of Pfliiger's law come off equally well with
tripolar excitation of the nerve, as in Fig. 160. The nerve is even
more sensitive to this form of stimulation, probably owing to the
larger area of the intrapolar tract, so that currents which were
ineffective with ordinary bipolar contacts may become effective.
There may be exceptions to Pfliiger's law owing to the influence
of accessory factors. Such are the local alterations of excitability
due to the effect of temperature, to salt solutions, to interference or
coincidence of the polarising current and the demarcation current,
etc. When, for instance, the kathode is close to the section in a
freshly divided nerve, a break contraction can be obtained not
only with medium, but also with weaker currents/ which are
usually ineffective. This is because in such a case the descending
break current summates with the demarcation current, which is
also descending. When, on the contrary, the two currents are
opposite in direction, the effects are neutralised. It can, in fact,
be demonstrated experimentally that a vigorous demarcation
current is able to annul the exciting action of a weak polarising
current in the opposite direction (Hering).
The polarisation after-effect, which appears in the nerve after
the passage of a polarising current of sufficient strength and
duration, may both at make and at break render another current
in the same direction effective when the latter is too weak to
produce any excitation alone. The break contraction resulting
in this case may be taken as a proof of the fact that the disappear-
ance of anelectrotonus is as capable of arousing excitation as the
appearance of katelectrotonus.
The polarisation after-current on the passage of a strong
polarising current may itself cause a prolonged excitation
expressed by the persistent contraction of the muscle. This
phenomenon is known as Ritter's opening tetanus. It is seen
iv GENEEAL PHYSIOLOGY OF NERVOUS SYSTEM 251
with an ascending polarising current, and depends upon excitation
at the former anode, as is also proved by the fact that division of
the nerve in the intrapolar tract during tetanus is not enough to
abolish it.
The closing contraction of a polarising current may also,
under special conditions of exaggerated local excitability of
nerve, be transformed into a closure tetanus when the direction
of the current is descending. This phenomenon evidently
depends on persistence of kathodal excitation.
Waller and De Watteville (1882) devoted much time to
verifying Pfltiger's law for man. The study of the polar
phenomena on man presents special complications, owing to the
presence of the tissues by which the nerve is surrounded. In the
frog's nerve the polarising current is applied directly, the poles
being set far enough apart to keep the kathodal and anodal
FIG. 161. — Diagrams to show the spread, or concentration, of a polarising current that enters or
leaves the skin by a series of points above a nerve, over which the anode (A) or kathode (A") of
a battery is applied. (Waller.)
influences distinct. In man, on the contrary, the current must
be sent in through the skin, and before reaching the nerve it has
to pass through all the tissues which lie above it. Peripolar
regions are thus formed more or less extensively round the poles,
which make it futile to apply the two electrodes to the same
nerve, since the kathodal and anodal regions cannot be kept
distinct, nor can the direction of current strictly speaking be
called ascending or descending. It is, therefore, necessary to
employ Chauveau's method of unipolar stimulation, in which
one electrode is placed upon the skin above the nerve and the
other applied to a distant point of the body. When the anode
is applied to the nerve, the current enters by a series of points,
over a considerable length of the nerve, and leaves by another no
less extensive series of points (Fig. 161 A). The former constitute
the anodal polar region, the latter the kathodal peripolar region.
When, on the contrary, the kathode is applied to the skin over
the nerve, the opposite phenomena occur (Fig. 161 K). The
current which is widely diffused in the body is thus concentrated
at the points of exit from the body which form the kathode. Its
252
PHYSIOLOGY
CHAP.
density is therefore greater in the kathodic polar than in the
anodic peripolar region.
As, therefore, the excitations and make contraction arise at
the kathode, and the excitation and break contraction at the
anode, Waller says that when a current strong enough to produce
contraction at break as well as at make is employed for unipolar
stimulation (anodal or kathodal) the kathodal closure contraction
is the strongest ; the kathodal opening contraction the weakest.
The anodal closure contraction is less strong than the kathodal,
and the anodal opening contraction is less weak than the kathodal.
If instead of using strong currents, unipolar stimulation
commences with a weak current that is gradually strengthened,
the contractions (auodal and kathodal closure and opening) appear
in the following order :—
Weak current
Kathodal
closure contrac-
tion
Medium current
Kathodal
closure contrac-
Anodal closure
contraction
Anodal opening
contraction
Strong current
tion
Kathodal
closure contrac-
tion
Anodal closure
contraction
Anodal opening
contraction
Kathodal
opening
contraction
This order of contractions constitutes what Waller calls the
" law of contraction in man," which may be interpreted as follows :
The fact that the kathodal make contraction is the first to
appear with weak currents, and is the strongest of all the reactions
with medium and strong currents, is due to its dependence upon
the katelectrotonus that arises in the polar regions, i.e. upon the
most effective form of stimulus in the most favourable region.
The appearance of the kathodal break contraction with strong
currents only, while it is the weakest of all the reactions, is due
to its dependence upon the disappearance of katelectrotonus in
the peripolar region, i.e. on a less effective form of stimulus in
the less favourable region. That the anodal make contraction
usually precedes the anodal break contraction can be explained by
the fact that the former depends on the appearance of katelectro-
tonus in the peripolar region, the latter on the disappearance
of katelectrotonus in the polar region. At other times, indeed
(Waller), this order may be inverted, and the anodal break con-
traction may precede the anodal make contraction. This anomaly
is only an apparent deviation from the law, and depends on the
relative density of current in the two regions, due to the nature
of the tissues that surround the nerve.
According to Waller, the latent period of the break contraction
in man is constantly about 0'05 sec., i.e. it is extremely long in
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 253
comparison with the very variable latent period 1'or the frog. It
is also a striking fact that when strong currents are used con-
tractions not only appear at make and break of the current, but
there is frequently a tonic contraction or galvanotonus during the
whole time the current is passing.
The law of contraction in man is of great practical importance
in differentiating between normal and morbid states of the nerves,
as with the latter the above reactions may be deficient or absent,
owing to depression or abolition of excitability and conductivity.
The so-called reaction of degeneration is clinically of great
interest. It occurs when the muscle and nerve degenerate,
either from pathological processes in the trophic centres, or
because the connections of the latter with the muscles have been
interrupted (neuritis, compression and injury of the nerves).
Two principal forms of the reaction of degeneration can be
distinguished : Erb's reaction, and reaction at a distance.
(ft) Erlfs reaction is characterised by a primary phase of
increased galvanic excitability, with loss of direct and indirect
faradic excitability. Later on, galvanic excitability, too, disappears
in the nerve, and the contractions obtained on exciting the muscle
directly become slow, prolonged, and irregular, and are most
marked on closure at the anode or positive pole ; with the
advance of the degenerative process stronger and stronger
currents are required to excite the muscle, till finally all trace of
electrical excitability disappears.
(&) Reaction at a Distance. — The reaction to which Ghilarducci
(1895) gave this name is constantly exhibited under the same
pathological conditions as Erb's reaction. To demonstrate it the
large electrode (indifferent electrode) is placed as for Erb's reaction
on the sternum or nape of the neck ; but instead of applying the
exploring electrode to the surface of the muscle as for Erb's
reaction, it is placed below it at a distance so much the greater
from the peripheral extremity, as the tendon of the muscle to be
explored is shorter and the patient more delicate (e.g. to examine
the deltoid in children of less than a year old the exciting
electrode is placed upon the back of the hand).
" Reaction at a distance " is distinguished from " Erb's reaction "
by the following characteristics :—
(a) The muscular contractions constantly predominate at the
closure of the negative pole ;
(ff) They are manifested with currents three to four times
weaker than those required to make the muscle contract with
direct excitation ;
(y) They persist long (three to four years) after every trace
of electrical excitability, as tested by classical methods, has
disappeared.
Reaction at a distance is thus of far greater importance than
254 PHYSIOLOGY CHAP.
Erb's reaction, since it survives for a long time, and is, in ad-
vanced stages of disease, the sole means of proving the existence of
degenerative processes.
In order to determine more exactly what changes in the con-
ductivity of nerve accompany the electrotonic alterations of
excitability, Novi with Brugia (1890) carried out a series of
investigations on the latent period by direct stimulation of motor
nerves in a state of electrotonus. These experiments were per-
formed on the exposed sciatic of the dog by Chauveau's unipolar
method. A second series of investigations was made by Brugia
on man with the object of determining the degree in which the
electrotonic alterations of excitability affect the conductivity of
motor nerves left in normal relation with the surrounding tissues.
The results are as follows :—
(".) In the isolated nerve of the dog anelectrotonus produces a
considerable delay in the rate of transmission ; katelectrotonus, on
the contrary, accelerates the transmission of excitation, excepting
for strong currents, when it is retarded, though to a less extent
than for anelectrotonus.
(&) In the nerve of man left in its normal relations with the
surrounding tissues, both katelectrotonus and anelectrotonus, but
the latter more especially, produce a considerable delay in the
rate of conductivity.
(c) In the nerve both of dog and man a progressive increase
in polarisation increases the latent period proportionately; but
while a certain degree of anelectrotonus blocks the conduction of
the impulse completely, katelectrotonus may become very pro-
nounced before it abolishes the conductivity of the nerve.
(d) While the delay in the muscular response ends almost
simultaneously with the cessation of katelectrotonus, there is, on
the contrary, both in dog and man, a very long interval before the
nerve regains its full conductivity in anelectrotonus.
(V) Increased strength of stimulus has hardly any effect on the
anelectrotonised nerve, while it compensates the difficulty of con-
duction for the nerve produced by katelectrotonus.
(/) In nerves which have begun to degenerate, i.e. in the state
in which faradic and galvanic excitability are merely diminished,
the electrotonic delay in conduction is more pronounced than
under normal conditions ; at a more advanced stage of degenera-
tion even katelectrotonus is capable of prolonging the latent
period, and all the various phenomena of electrotonus are slower
and more feebly developed.
IX. How far is it possible from the whole of the facts before
us to construct a general theory of the genesis and intrinsic
mechanism of nervous activity ? Before replying to this question
we must review the various hypotheses that have been brought
forward.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 255
It is hardly necessary to mention the grossly mechanical con-
ception of the early physicians, who compared the influence of the \
nerves upon the muscles to the pulling of hell wires in order
to ring them.
Another hypothesis that now seems little less puerile, although
under various forms it prevailed for centuries, was that hy which
the nerves were regarded as hollow tubes or canals, within which
circulates a fluid, or a more or less ethereal and mystical gas, that
conveys the movements ordered by the brain and the sensations
from the sense organs, and received various names according to
the epoch and school of thought (spi-ritus mtalis or animalis,
pneuma, fluidum nerveum, etc.). The paralysis produced by
ligation of a nerve was explained as the necessary effect of the
arrest of the fluid that circulates in the nerve tubes.
At a much later time physicians conceived the conduction of
neural activity as a phenomenon analogous to the imdulatory \
transmission of a mechanical impulse through an elastic medium,
the nerves being regarded either as vibrating cords or as being
composed of a number of minute elastic particles which transmit
their oscillations one to another (Robinson, 1630). The theory of
an imponderable nervous fluid was, however, more plausible and
found more favour. Especially after the phenomena of frictional
electricity and the laws of its propagation became known many
physicians thought they could compare activity in the nerve to
that of an electrical apparatus. Hausen (1743) and de Sauvages
(1744) were the first who upheld the electrical nature of nervous
activity. Haller criticised this hypothesis, holding it to be
unfounded and contradicted by two important experimental facts
— absence of insulation of the nerves, and the paralysing effects of
tying the nerve.
It was not till Walsh (1773) had pointed out the electrical
nature of Torpedo shocks, and Galvani had discovered animal
electricity, that the hypothesis of the electrical nature of nervous
activity became more widely known and accepted, and it has [
only acquired the definite position of a scientific theory within
recent years.
The hypothesis of absolute identity between electricity and
neural activity received a fatal blow when Helmholtz (1850)
demonstrated by exact physical methods that conduction in the
nerve proceeds at an incomparably slower rate than electrical con-
ductivity (see p. 203). Nevertheless it appears highly probable
from the work on animal electricity done by Nobili, Matteucci,
and particularly by Du Bois-Reymond on the negative variation
of the nerve current and the phenomena of electrotonus (1843),
that electrical energy does play a part in nervous conduction,
although under a different form from that assumed in the theory
of their identity.
\
256 PHYSIOLOGY CHAP.
In order to account for the complex of phenomena comprised
under the term "animal electricity," Du Bois-Eeymond pro-
pounded his molecular theory, according to which the nerve
contains a large number of peripolar electrical molecules, arranged
in regular order. But this theory, which now has only historical
interest, seems neither acceptable nor necessary after the rigorous
criticism of data which led Hermann to formulate the ((Iteration
theory, — accepted by most physiologists. Du Bois-Eeyrnond failed
to show how his molecular theory could account for the intimate
mechanism of the conduction of excitation along the nerve.
To-day it is almost universally admitted (supra, p. 200) that
the conduction of excitation is caused by a physico-chemical pro-
cess in the living matter of the axis-cylinder, which is propagated
from one segment to another like a spark, one segment or portion
of the fibre being excited by the next, as though the state of the
active portion acted as a stimulus upon the inactive.
This schematic conception of neural conductivity obviously
connotes the theory that the two physiological attributes of nerve,
excitability and conductivity, are fundamentally only different
expressions of one single property. For if we assume the con-
duction incited by an external stimulus to be due to the fact that
the active state of the excited segment acts as an internal stimulus
for the next segment, then conductivity must obviously be con-
ceived as a particular form of excitability, and the existence of
the first is not admissible without the second.
Tbis theory has been opposed by a wbole series of facts, which
seem to show that under certain conditions conductivity can be
diminished, or even abolished, without perceptible injury to
excitability, and vice versa (see p. 229 for the local influence of
anaesthetics upon nerve) ; and that under many other experimental
conditions the rise or fall of the two properties are not parallel,
(see p. 245, katelectrotonic and anelectrotonic alterations of
excitability and conductivity). Nor can we absolutely deny the
contention of van Deen, Schitf, and others, that the central nervous
system contains fibres endowed with perfect physiological con-
ductivity (aesthesodic and kinesodic fibres), which are entirely
devoid of excitability to any artificial stimuli. But even if well
established these facts do not prove that excitability and con-
ductivity cannot co-exist ; at most they show that different nerve
fibres, or the same fibres under different experimental conditions,
present great variations of susceptibility to various stimuli and
their respective modes of action. It is quite probable, as Hermann
pointed out, that adequate internal stimuli normally find more
favourable conditions of excitation and conduction in nerve than
do the artificial external stimuli which are foreign to physiological
life. In this connection the work of Gotch and Macdonald on
the influence of temperature upon the excitability and con-
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 257
ductivity of nerve should lie remembered. They confirm the
preceding results of Helmholtz, Grlitzuer, and other authors, and
show that conduction must be an effect of excitation because it
varies with variations of temperature in correspondence with the
rise or fall of excitability.
An exhaustive theory of nervous activity would have to define
iu what the physico-chemical alterations of the fibre that we
term " excitation " consist, and how they are propagated to
adjacent segments, which is the process of " conduction." We
are far from any such theory. We can only affirm that the active
state of the point of nerve stimulated is intimately associated
with its electrical negativity, and the conduction of excitation
with the wave-like propagation of this negativity, i.e. the current
of action. Since the electrical stimulus is among the most
powerful excitants of neural activity, and is an important factor
in excitability, it seems probable that the action current of
nerve is no mere accessory pheno-
menon, but that it is the im-
mediate cause of the conduction
of the excitatory impulse. ...
According to Hermann this
conduction may be explained on
the assumption that anelectro-
tonus is produced at the excited
„ , Fie. 1132. — Diagram of conduction in nerve.
Spot, 111 COUSeqiience OI external (Hermann.) For explanation see text.
stimulation, and katelectrotonus
in the adjacent segments. Hermann's hypothesis is illustrated
iu the diagram (Fig. 162), in which KK represents the axial
substance, HHHH the sheath of the nerve-fibre, pqrs the segment
of nerve stimulated. The lines of demarcation (ps, qr) between the
excited segment and the adjacent non-excited segments present two
electromotive surfaces, owing to the negative electrical potential of
the former, which generate currents in both directions, as indicated
by the diagram. According to Hermann these currents must be
of enormous strength, seeing the microscopic interval, and conse-
quent minimal resistance, between the two electromotive surfaces.
They are therefore capable of producing in the auodal zone (aa, aa)
an anelectrotonus which throws the substance of the nerve into
rest, and in the kathodal zone (cc, cc) a katelectrotonus of sufficient
intensity to excite it. In this way the excitatory impulse is trans-
mitted along the nerve.
Yet even on these assumptions we have, as Hermann confesses,
no perfect theory of conduction in the nerve. His hypothesis
seems probable from the fact that his core-model, consisting of a
platinum wire surrounded by a solution of copper sulphate, is
able (according to Hermann and Samways and Boruttau) to
exhibit electrotonic currents, which advance in wave form like the
VOL. in s
258 PHYSIOLOGY CHAP.
action current of the nerve. To demonstrate this fact it is only
necessary to send a polarising current of brief duration through
the model, and to lead off from more or less distant points by the
galvanometer electrodes. Electrotonic currents make their appear-
ance at a time when the polarising circuit has already 'been broken.
How these waves, which are analogous to the action currents of
nerve, can be generated in the artificial conductor is still obscure.
The apparent similarity of the two phenomena is interesting, and
justifies the conjecture that conduction of the impulse in nerve
consists in the spreading in wave form of a physico-chemical
molecular process, comparable with that observed on the core-
model. This hypothesis agrees better with the known facts of the
velocity of transmission of the nerve impulse (which we have seen
to be about 40 m. per second) than any other theory, on which
the active state of nerve is assumed to be a chemical modification
accompanied by metabolic phenomena.
Biedermanu objected to the hypotheses of Hermann and
Boruttau that conduction of excitation is a general property,
common to many tissues very different from nerve. In some of
these tissues conduction takes place from cell to cell, e.g., in ciliated
epithelial cells, in hydroid colonies, in the cells of cardiac muscle,
etc. Yet, as Boruttau remarks, in these cases cited by Biedermann
the transmission of the impulse can be measured by millimetres
or centimetres per second. These phenomena are in a different
category from those manifested in the homogeneous elementary
fibrils of the axis-cylinder, in which the velocity may reach 60 rn.
per second.
On the other hand it must be pointed out that nerves have
recently been found in invertebrate animals with a comparatively
sluggish rate of conduction, while many gradual transitions exist
between the most rapid conduction of vertebrate nerves and that
of other tissues, so that there is no justification for assuming a
fundamental difference in the process of nerve conduction. As
we have seen, the latest investigations on asphyxia and fatigue in
nerve have proved that its metabolism, however small, is by no
i means a negligible factor, and must be taken into account in
any comprehensive theory of nervous activity. The chemical
theory, which refers the conduction of the excitatory impulse in
nerve, like that in all other tissues of the body, to the propaga-
tion of a process of chemical change, and regards the electrical
phenomena solely as accessory, is, therefore, at least in theory, as
acceptable as the purely physical theory.
Of late the theory of axial conduction seems to be yielding
more and more to modern concepts of physico- chemistry, by
which the bio-electric phenomena are referred to the principle of
concentration cells (Ostwald, Tschagowetz, Macdonald, Oker-Blom,
Bernstein, and others). Nernst and Zeynek (1899), on the strength
iv GENERAL PHYSIOLOGY OF NEKVOUS SYSTEM 259
of certain analogies, proposed the theory that every excitation of
living matter (conceived as ;i system of semipermeable membranes)
induces change in the concentration of the ions, and that the
resulting concentration currents set up conduction in the nerve.
In this way, as pointed out by Boruttau (1904), it is possible to
reconcile the two opposite theories, physical and chemical, by
assuming that conduction in the nerve depends upon the electrical
currents produced by chemical metabolism.
This theory, which Verworn has also (1906) accepted, presents
the further advantage of not being confined to nervous tissue, since
it is applicable to all other tissues of the body.
X. We have seen that the function of the nerve-fibre is to
conduct excitation. Under normal conditions the excitatory
impulse never arises in the fibres, hence they are not capable of
transforming or reinforcing the impulses transmitted, either from
the periphery (centripetal or afferent nerves), or from the centres
(centrifugal or efferent nerves). The excitability of nerve-fibres
is rather a condition of their conductivity than an autonomous
property. But when the centripetal impulse has reached the
central grey matter the afferent impulse is transformed into an
efferent impulse. This transformation consists not in a simple
reversal of direction of the impulse, but in a discharge of fresh
energy, in which there is often a marked disproportion between
the afferent and the resulting efferent impulses. When, e.g., a
foreign body comes in contact with the glottis, a loud fit of
coughing is reflexly excited. This indicates that the stimulation
of a few sensory fibres is able in the centres to produce spread of
excitation to the motor fibres of all the expiratory muscles. There
is thus in the centres an explosion of fresh energy, comparable to
that discharged in the muscle when the excitation reaches the
end-plates along the motor nerves.
The transformations which the afferent impulses undergo in
the centre can also be expressed as a diminution or inhibition of
pre-existing activities. The foreign body which provokes reflex
couo-hincr when it touches the glottis does not merely throw the
O O O */
motor centres of the expiratory muscles into activity, but it
simultaneously inhibits the activity of the inspiratory muscles.
Every co-ordinated reflex presents this double action of afferent
impulses on the central organ. The afferent impulses are also
capable of setting up processes which lead to the facilitation
(Balinung] l of other reflex acts.
While conductivity is the fundamental physiological function v
of the peripheral nerve-fibres — since we have no proof that these \
modify impulses during conduction, — excitability is the funda-
mental function of the nerve-centres, so that a weak impulse
1 BahnuiKj has been variously rendered in English as facilitation, reinforcement,
canalisation, augmentation. — Tu.
260 PHYSIOLOGY CHAP.
may set up a vigorous and widespread reaction, with great ex-
penditure of energy.
As we know nothing of the physiological process which is the
material basis of nerve excitation, we are a. fortiori ignorant of
the physiological process which underlies the excitation of the
centres. It can only be said that from the subjective, psycho-
logical point of view, it may be distinguished as conscious and
unconscious, according as it is accompanied or unaccompanied by
changes in the ego and the state of consciousness. From the
objective physiological point of view it may be either reflex or
automatic, i.e. evoked by impulses that reach the centre from the
periphery by afferent paths, or by such as arise within the centre
itself, and are sent out peri-
pherally to the motor apparatus.
Both reflex and automatic acts
may, of course, be either con-
scious or unconscious.
We have so far always
spoken of centres or of central
grey matter in contrast to the
peripheral nerve-fibres, but this
general expression includes two
quite distinct structures, the
ganglion elements or nucleated
nerve -cells, and the extra-
cellular fibrillary network.
Here, again, the question crops
up : is the central process (re-
Fio. 163.— One of the unipolar n<>rve-cdls that Hex Or automatic,
"liS: )°f U"' ' or unconscious) seated in the
ganglion cells or in the extra-
cellular network of fibrils ? From the morphological point of view
the matter is still — as we have seen — sub judice (pp. 180 et seq.}\
but we must now review the physiological arguments that bear on
one or the other of these hypotheses.
In support of the opinion that the ganglion cell is only a
trophic centre, a reservoir for the nerve currents, while the central
activity of the system develops outside the cell, in the elementary
neuro-fibrillary network of the grey matter, Bethe (1897-8) adduced
an experiment made upon Carcinus maenas, a crayfish. The
muscles of the antennae of this crustacean are innervated by
neurones which (as shown by the diagram, Fig. 163) recall the
unipolar cells of the spinal ganglia of mammals. At a considerable
distance from the pear-shaped cell body the nerve process divides
into two branches, one of which is in connection with the dendrites
of other neurones or neuropile, and forms the cellulipetal path,
the other runs to the muscles of the antennae and forms the
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 261
cellulifugal path. After isolating the cephalic ganglion that
innervates the second pair of antennae, Bethe frequently succeeded
in completely removing the part which contains the bodies of the
ganglion cells, so that not one of them was left connected with the
neuropile and the peripheral nerve processes. Twelve to twenty-
four hours after the operation he found that the tone of the muscles
of the antennae was normal ; the reflexes excited by contact were
carried out normally, or even exaggerated ; and on applying re-
peated slight stimuli which were individually insufficient to induce
a reflex, they summated, and eventually discharged a reflex. On
the second day from the operation, however, the reflex excitability
was diminished, the movements of the antennae became smaller and
slower; finally, on the third to fourth day they ceased altogether,
even to the strongest stimuli, the antennae remaining drooping and
relaxed as if their nerve had been divided. From these results
Bethe concluded that the ganglion cells, i.e. the nucleated portions
of the neurones, are not essential to reflex phenomena ; and that
muscular tone, co-ordinated reflexes, and summation of stimuli,
may persist even after removal of the ganglion cells, as if the
excitations passed directly from the neuropile to the motor nerve
of the antennae, as indicated by the arrow on the diagram. The
early disappearance of functional activity after removal of the
ganglion cell is due to the loss of its trophic action upon the
entire neurone.
In the unipolar neurones of vertebrates, as in those of the spinal
ganglia, the cell body appears to be a collateral appendage to the
paths of physiological conduction, and there is reason to doubt
whether the excitations naturally pass through it, and if it is inter-
calated on the paths followed by the physiological impulses. This
hypothesis, already raised by Nansen and by Ramon y Cajal, seems
probable not only from Bethe's experiments, but also from those of
Steinach, who endeavoured to bring about the degeneration of the
frog's spinal ganglia by cutting off their blood-supply. Under such
conditions he observed that reflexes could be obtained on exciting
the sensory nerves as long as ten to fourteen days after the
operation, although under the microscope it could be seen that the
ganglion cells had undergone a more or less profound degeneration.
But Verworn rightly points out that this experiment is of no great
value because the exact degree to which degeneration must be
pushed before the cells are rendered incapable of conducting has
not been determined by histological examination. Stomach's experi-
ment does not therefore exclude the possibility that the impulses
normally pass through the ganglion cells.
Greater importance must be attached to the experiments on
whether the afferent impulses conducted by the sensory nerves
are delayed in passing through the spinal ganglion or not. Exner
(1897) was the first to state that there was no delay. His experi-
262 PHYSIOLOGY CHAP.
inents, which contradicted those of Wundt, who had previously
found a delay of 0'02 sec., were repeated by Moore and Eeynolds
(1898) at Schiifer's instigation. They cut all the bundles of a dorsal
spinal root in the frog, except one, and recorded the reflex time of
a muscular contraction on exciting first the remaining bundle of
the root and then the nerve before its entrance into the ganglion.
They found that the latent period did not vary perceptibly, which
led them to conclude that the afferent excitations traversing the
sensory paths do not pass through the body of the ganglion cells,
the true function of which is trophic.
But can this conclusion from the spinal ganglion cells be
properly extended to all ganglion cells of the grey matter of the
central nervous system of vertebrates 1 Can we from the physio-
logical standpoint unreservedly accept the theory of Apathy and
Bethe that the diffuse network of nerve fibrils, which appears to
be the universal and essential medium of the reciprocal relations
between the different fibres and the ganglion cells, represents the
true and only substrate of the central neural phenomena 1
Possibly our knowledge is not yet enough advanced to be able
to give a decisive and final reply to this question. But it is closely
related to the question of the specific energies called out by the
excitation of the different sensory nerves. What is the true
material basis of specific energy ? Why does the optic nerve in-
variably respond by visual sensations and the auditory nerve by
sensations of sound, whatever the nature of the stimulus that
affects them ? Does this depend on the specific nature of the
neurones in toto, i.e. on the peripheral conducting paths as well as
the centres ; or are all conducting nerve-fibres essentially identical
in character, and is the substrate of specific energy represented by
the peripheral and central, sensory and motor connections of the
nerves ? Most physiologists, particularly those who have studied
the general physiology of nerve (among them Du Bois-Eeymond
and Hermann) are in favour of the latter view.
Still there are not wanting supporters of the opposite theory,
who assign to the individual fibres (sensory and motor, rnedullated
and non-medullated) a qualitatively different functional nature
(Griitzner and others). Bering (1899), on the strength more
particularly of his studies on the physiology of the senses, declared
emphatically against the doctrine of the identity of nerve functions,
and assumed instead that the individual neurones differed not only
by their different place in the system, but also by the qualitatively
different nature, innate or hereditary, of their activity.
Whatever the final solution of this difficult problem, it is
certain that the mode in which the central grey matter reacts
to direct or indirect stimulation presents certain characteristic
peculiarities by which it is distinguished from the peripheral
nerves.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 263
The grey matter of the centres is capable of reacting by pro-
longed excitation to a simple stimulus, e..g. the prick of a pin.
Thus Birge observed that the rat's spinal cord reacted by simple
twitches to puncture of the white matter and by a regular tetanus
to puncture of the grey matter. Again, the frog's spinal cord
responds by prolonged excitation to single induction shocks
(Marchand). According to Baglioni and Fienga the motor
elements of the ventral horn exhibit the same property as the
frog's spinal cord, of reacting to single stimuli by tetaniform
excitation.
Another charactistic property of the grey matter is that it
reacts more effectively to frequent and weak stimuli than to
stronger and less frequent shocks. Kronecker and Nicolaides, on
FIG. Ki4. — Reflex movement of frog's leg after electrical stimulation. (Stirling.) The lower line
marks seconds ; the middle line the duration of the stimulation ; the upper line the reflex
movement preceded by small preliminary contractions.
stimulating the vasomotor centre, obtained feeble effects with
strong but infrequent induction shocks, while with moderate but
more frequent shocks of the same current the effect was much
more pronounced. The same appears in reflex stimulation of the
spinal cord ; break induction shocks of a given strength induce
reflex movements more rapidly in proportion to their frequency
(Stirling). With this property is intimately associated that of
summation of stimuli possessed in a striking degree by the grey
matter ; this gives the character of a high tension discharge to
the reaction. Sanders -Ezn with chemical stimuli, Stirling with
electrical stimuli, applied to the skin of the decerebrated frog,
obtained small preliminary contractions and then a vigorous
contraction, which is succeeded by a period of exhaustion, necessary
to the formation of a new charge (Fig. 164).
Lastly, artificial excitation of the grey matter shows that it has
the faculty of transforming the rhythm of the stimulation into a
different and characteristic rhythm of its own. This is seen from
264 PHYSIOLOGY CHAP.
the investigations of Kronecker and Stanley-Hall, quoted on p. 21
(Fig. 13).
Baglioni showed in a preliminary series of researches (1900),
carried out especially upon the spinal cord of the frog, that it is
possible to differentiate between the individual elements of the
central substance by their reactions to certain poisons. He started
from the observation that strychnine and phenol have the common
property of increasing the reflex excitability of the spinal cord to
an enormous extent, but the disturbances they produce are dis-
tinct. While strychnine poisoning causes tetanic spasms in all the
muscles of the body so that co-ordinate movements become im-
possible, phenol poisoning does not abolish co-ordinated movements,
but these are interrupted by rapid clonic contractions which produce
constant attacks of tremor in different muscles.
Baglioni referred these fundamental differences to the different
point of attack of the two poisons upon the spinal cord. He
found that if carbolic acid were applied to the cells in the dorsal
or posterior part of the cord, while the ventral cells were spared,
clonic contractions of the limbs appeared ; but if strychnine was
subsequently applied to the same region, it failed to elicit tetanic
action. These and other experiments led Baglioni to conclude
that the action of strychnine is confined to the cells of the dorsal
part of the cord (sensory or co-ordinating ganglion cells of the
dorsal horn), while phenol has a selective action upon the cells of
the ventral part of the cord (motor ganglion cells of the ventral
horn).
In subsequent researches upon other animals Baglioni (1904-9)
confirmed and amplified the theory of the elective action of
strychnine and phenol upon specific central cells, and claimed
that it is a physiological method by which the existence of sensory
central elements reacting to strychnine and of motor elements
reacting to phenol can be readily detected. He also found that the
central nervous system of invertebrates contains elements that react
to one or the other of these two poisons. In Cephalopoda the
ganglion stellatuin of the mantle consists of ganglion cells, which
react exclusively to the action of phenol and cause clonic spasms
in the muscles innervated by them, while they are entirely unaffected
by strychnine, which, on the other hand, attacks the higher central
ganglia of the head, and produces tetanic convulsions similar to
those seen in vertebrates. Fr. W. Frohlich (1910) confirmed and
amplified Baglioni's work on Cephalopoda.
In the higher vertebrates also (dogs), strychnine and carbolic
acid exhibit an elective exciting action on the different ganglion
cells. Baglioui and Magnini (1909) noticed the remarkable fact
that strychnine, besides picking out cells in the dorsal region of
the cord and bulb, will also attack the ganglion cells of the
excitable zone of the cerebral cortex, and excite them to activity.
iv GENEEAL PHYSIOLOGY OF NEEVOUS SYSTEM 265
More recently (1909) Baglioni has brought forward other
experimental arguments in support of the theory of the elective
action of these two poisons, and emploj^ed the cerebrospinal axis of
the toad, which, unlike that of the frog, can be completely isolated
and removed from the vertebral cavity owing to the great length
of its cauda equina. It allows all the operative handling
necessary for the complete isolation of the cerebrospinal axis,
which in the frog involves serious lesions and even death of the
central substance, since this is extremely sensitive to the least
mechanical injury. In the central preparation of the toad (Fig. 166)
it is comparatively easy to apply small wads of cotton wool soaked
in strychnine or carbolic acid to the dorsal or ventral surface of
the lumbo-sacral enlargement, which contains the centres of reflex
activity for the posterior limbs. It is found that strychnine pro-
duces increased reflex excitability and tetanic spasms when applied
to the dorsal surface of this part, while it is inert when placed in
direct contact with the ventral surface. Vice versa, carbolic acid,
in a weak solution (Ol per cent) increases reflex excitability and
produces clonic convulsions when applied to the ventral surface,
while it has no such effect when brought into direct contact with
the dorsal surface. By this means Baglioni also demonstrated
the presence of central elements on the dorsal surface of the bulb,
which, under the local action of strychnine, induce tetanus in
the posterior limbs.
Baglioni confirmed the interpretation already given by Claude
Bernard of the origin of the tetanic spasms observed during the
action of strychnine. The essential cause is the abnormal increase
of reflex excitability produced by strychnine, owing to which
minimal peripheral sensory stimuli, which are incapable under
normal conditions of inducing reflex contractions, are now adequate
to excite all the centres of the cord which they affect, to the point
of exhaustion. If after severing the spinal cord from the bulb the
whole of the dorsal roots are cut (as was also seen in 1893 by
H. E. Hering), or if every peripheral stimulus from the skin and
the higher sense organs is artificially eliminated by placing the frog
in a suitable medium, strychnine will kill the animal without pro-
ducing any tetanic spasms. While the stimuli from the skin and
external sense-organs induce the primary contraction of all the
muscles of the body, it is the secondary stimuli coming from the
end organs seated in the muscles and tendons stimulated by the
muscular twitches that reflexly incite the subsequent tetanic con-
vulsions, till the temporary or final fatigue of central activity is
brought about.
That under normal conditions the spinal cord is not capable of
reacting by a prolonged series of tetanic contractions to faradic
stimuli applied to afferent fibres is due to the fact that after each
single excitation the central elements are thrown into a refractory
266 PHYSIOLOGY CHAP.
period or time of recovery, which lasts Q'25-0'5 sec., during which
they are incapable of transmitting impulses to the motor elements
of the ventral half of the cord. The latter, on the contrary, are
still, under normal conditions, able to react to a series of stimuli
thrown in in rapid succession, which evokes tetanic contractions of
the corresponding muscles.
Finally, in another series of researches, Baglioni studied the
action of many derivatives of phenol, and saw that while some of
these, such as the di- and tri-phenols, have the same exciting action
as carbolic acid, others produce an initial depression ; others, again,
like benzoic and salicylic acids, have no action on the nerve-
centres.
From these observations as a whole, as well as from the varying
capacity of resistance to asphyxia shown by the individual parts of
the cerebrospiual axis, it is obvious that there are fundamental
differences between the peripheral and central nervous systems,
and also between the different elements of the central system—
functional differences that certainly cannot be reconciled with the
theory of equivalence or physiological identity of all the elements
that make up the nervous system.
Unlike the peripheral nerves, the central grey matter has
a very active metabolism, and is therefore highly vascular. In
this connection Fritsch made an important observation to the
effect that the large ganglion cells of the nuclei of origin of
the vagus and trigeminus nerves in Lophius piscatorius are
traversed by a network of capillaries which is essential to their
nutrition.
The need of a blood-supply for the function of the nerve-
centres is shown by the effects of blocking the vessels which supply
them. A diminished flow of blood to the brain by rapid compres-
sion of the two carotids suffices to abolish consciousness, and in
many cases produces a fainting fit, owing to the incapacity of the
grey matter to function, due to anaemia. Stenson's experiment
(cited elsewhere) that compression or ligation of the abdominal
aorta of the rabbit, is quickly followed by paralysis of the hind
limbs, shows that anaemia of the spinal cord makes the ganglion
cells incapable of function.
Fredericq repeated Stenson's experiment 011 dogs in order to
determine more accurately the time required to produce motor and
sensory paralysis. Fifteen to twenty seconds after the occlusion
of the aorta there was a transitory motor excitation of the muscles
of the limbs, followed by motor paralysis which became total in
30-40 sees. During this time the sensibility of the lower limbs
is unaltered ; it is only after 90 sees, that hyperaesthesia followed
by anaesthesia sets in, which becomes total about 3 mins. after
occluding the aorta. If the compression or the ligature is removed,
sensibility returns after 5-10 mins., and motility somewhat later.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 267
If the block is kept up for longer, uo functional recovery takes
place.
These facts, showing that the individual ganglion cells present
different resistances to anaemia, are confirmed by Landergren's
work on the phenomena of acute asphyxia. As shown in Fig. 165,
four stages can be distinguished in acute asphyxia. In the first
stage there is a brief rise of activity in the vasornotor bulbar
centre. When the activity of this centre ceases the excitation
of the vagal cardiac centre reaches its maximum. The course of
i. n. in. iv.
Period of general Period of suspended Period of exagger- Final period (pre-
rxcitation. respiration. ated respiration. mortal).
Fir.. 165. — Diagram of vital resistance of some nerve-centres to asphyxia. (Landergren.) Tlie
continuous curved line indicates the functional excitation and subsequent paralysis of the
bulbar vasomotor centre ; the dotted line, the functional state of the centre for the cardiac
vagus ; the broken line, the state of activity of the respiratory centre ; the dotted and broken
line (with which the life of the animal expires) indicates the functional state of the spinal
and vasomotor centres.
the excitation of the respiratory centre was not, owing to a long
pause in respiration, completely represented, but it appears to
coincide approximately with that of the bulbar cardiac centre.
The last to be thrown into excitation are the spinal vasomotor
centres, the activity of which continues even when the function of
the other centres is abolished.
That the metabolism of the nerve-cell is highly active in com-
parison with the very low metabolism of the nerve-fibre, appears
not only indirectly from the fact that the nucleated portion of the
cell is the trophic centre of the entire neurone, as we saw in
discussing Wallerian degeneration (see pp. 233 ct srq.'), but also
and more directly from the observation of Marinesco, that under
certain normal or morbid conditions of the ganglion cells there is
268 PHYSIOLOGY CHAP.
a gradual disintegration of the chromatic substance of Nissl's
granules (see Fig. 124, p. 189), which spreads uniformly over the
cell protoplasm. This process (known as chromatolysis} is accom-
panied by a swelling of the cell, with lateral displacement of the
nucleus, followed later by a diminution in the volume of the cell,
and the partial or total disappearance of the chromatic substance.
In studying the cytological changes in the nerve-cell after
prolonged work, Lambert, Eegnat,- and Mann saw that the nerve-
cell diminishes in size and that the chromatic substance is
disintegrated and gradually disappears, but Nissl, on repeating
these observations, obtained unconvincing results, though he
observed a certain diminution of the chromatic substance.
Clearer and more definite results ensue on severing the axon
from the cell, as shown by the investigations commenced by Nissl,
and continued in particular by Lugaro, Marinesco, and Van
Gehuchten. The first signs of chromatolysis in the cell were
observed twenty-four to forty-eight hours after section of a
motor nerve. The chromatolytic process goes on for about fifteen
days, when the cell is reduced to a rounded mass destitute of
Nissl's granules. The chromatolysis begins near the point of exit
of the axis-cylinder, then invades the perinuclear portion of the
cell, next the more peripheral part, and lastly the dendrites.
After twenty to twenty-four days the process of regeneration sets
in ; it progresses very slowly, and is complete in about three
months.
Alterations in the sensory cells after section of the peripheral
nerve were studied by Lugaro, Fleming, Cox, and others. On
cutting the spinal root between the ganglion and the cord, Lugaro
found few signs of chromatolysis in the cells of the ganglia. Van
Gehuchten and Nelis, on the contrary, observed chromatolysis in
the cells of the jugular ganglion after section of the vagus. It
differed only in not being followed by a process of reintegration, so
that after about three months the cells had almost entirely dis-
appeared. Nissl noted the same result in certain motor cells also,
and Schafer in the cells of Clarke's column, after section of the
direct cerebellar tract. This ascending or retrograde degeneration
after section of the nerve is a valuable help in localising the centre
connected with given nerve paths (Gudden's method).
It is easy to understand that all portions of the processes
separated from the nucleus degenerate, since the nucleus is the
centre of nutrition for the entire neurone : it is more difficult to
explain the cause of chromatolysis and the degeneration of the cell
body after the severance of a part of the axon. The disintegra-
tion and degeneration described by Van Gehuchten for certain
sensory cells are probably due to the loss of function, after inter-
ruption of the paths by which peripheral excitations normally
reach the cell. But this explanation is not applicable to the
iv GENERAL PHYSIOLOGY OF NEIIVOUS SYSTEM 269
phenomena of degeneration in motor cells, since their afferent
path remains intact. According to SchaTer the explanation is that
after section of the axis -cylinder, its end must tirst undergo
chemical and electrical alterations, under the influence of inflam-
mation and cicatrisation, which keep the cell in an abnormal state
of protracted excitation. In fact we have seen that chromatolysis
accompanies exaggerated activity of the nerve.
Chromatolysis may also result from the action of certain
poisons, e.g., arsenic, lead acetate, bromides, antipyrine, cocaine,
strychnine, alcohol, some bacterial toxines (rabies, tetanus, etc.).
A. Monti concludes from a long series of observations that
chromatolysis of nerve -cells is frequent, and is definite and
constant in cases of disturbed metabolism. On comparing
preparations made by Nissl's and by Golgi's method, Monti came
to the conclusion that there is an almost exact correspondence
between chromatolysis and degeneration of the dendrites. Both
are observed in nutritional disturbance of the nerve -cell. This
correlation between the alteration of the dendrites and those
of the chrornatophile substance agrees with Golgi's idea, that the
protoplasmic processes play an important part in the nutrition of
the nerve-cell.
Donaggio found that while the chromatic substance is readily
destroyed by pathogenic causes, the intracellular reticulum offers
an enormous resistance. It is, on the other hand, profoundly
injured when the pathogenic agent is combined with the action of
cold.
The subject of metabolism,, or the material exchanges in the
nerve - centres, has only been approached, largely by indirect
methods, of late years. It is a priori evident that in the central
masses of the nervous system, as in the other tissues and organs,
the specific functions are intimately bound up with the successive
phases of katabolism and anabolism, in which the discharge or
accumulation of energy takes place.
The fact that of all the tissues the central nervous system
offers most resistance to loss of weight in fasting shows its
predominance and its capacity for keeping the energy required for
its functions constant, by drawing its nutriment from all the
other tissues. This is, however, no argument for assuming that
the chemical work which accompanies the activity of the nerve-
centres is necessarily very active.
The earliest researches on the metabolism of nerve-centres
was confined to establishing the variations in the chemical
reactions. While the white matter preserves its alkaline reaction
to litmus for a comparatively long time after death, the reaction
of the grey matter in warm-blooded animals changes so rapidly
that it becomes acid almost immediately after death. For some
time this was supposed to be the vital reaction of the grey matter
270 PHYSIOLOGY CHAP.
(Gscheidleu). Langendorff (1885) first demonstrated that grey
matter also is alkaline to litmus intra vitam, and that the acid
reaction sets in after cutting off the blood -supply, and may
disappear again if the circulation is re-established promptly. The
observation that in the frog rise of temperature, strychnine
poisoning, or any cause that increases metabolism accelerates the
appearance of the acid reaction, led Langendorff to conclude that
the formation of acid is due to vital processes, the products of
which are eliminated under normal conditions by the blood stream.
We owe our first detailed knowledge of the metabolic pro-
cesses that go on in the nerve-centres to the researches of Verworn
and his pupils (1900-3). The method used by Verworn in his
experiments on frogs consisted in replacing the blood circulation
by an artificial circulation of various fluids. This artificial
circulation, in the form either of a constant stream or of a
rhythmically intermittent current similar to that of the normal
circulation by means of a small pressure pump (Winterstein,
Baglioni), was introduced through a glass cannula, inserted in the
aorta, near the heart. After passing through the whole vascular
system the fluid left the body again at the cardiac orifices, which
were opened so as to allow the circulating fluid to escape through
them. Verworn used strychuinised frogs for experiment because
their increased excitability made it possible to obtain a more exact
and easy demonstration of the changes in reflex activity caused by
the influence of various experimental factors. Briefly stated, his
results are as follows :—
If the blood of a strychninised frog is replaced by physiological
saline previously deprived of its oxygen by boiling, before the
circulation is started, the tetanic spasms that occur at every
contact gradually diminish and are separated from each other by
increasingly long pauses of inexcitability, till finally no reaction
can be aroused. On then circulating the oxygen-free saline there
is a slight initial recovery, which can only be explained by the
washing away of the toxic products of metabolism that have
accumulated. The recovery thus obtained is, however, incomplete
and of short duration. If, on the other hand, the salt solution is
replaced by well-oxygenated defibrinated blood, there is soon a
complete recovery shown by strong and protracted tetanic spasms.
What constituent of the blood is responsible for this complete
recovery of the normal excitability ? Verworn found that the
recovery was practically the same when salt solution fully
saturated with oxygen was circulated instead of blood, while
blood serum deprived of oxygen was totally ineffective. This
shows that the restorative action was due not to organic nutritive
materials, but solely to the oxygen.
On the strength of these results Verworn distinguishes two
fundamentally different factors in the paralysis of the centres, viz.
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 271
fatigue due to the accumulation of the toxic products of meta-
bolism, and exhaustion due to consumption of the supply of
oxygen. The former can be eliminated by mechanical washing,
the latter, on the contrary, only by a fresh supply of oxygen to the
centres. The paralysis caused by these two factors together
produces what Verworn terms work-paralysis.
Verworn attributes fatigue to the production and accumulation
of carbonic acid, more particularly on the strength of Winterstein's
experiments. This author found that C02 at a high concentration
is able to exert a markedly paralysing action on the centres, and
inhibits the appearance of the strychnine spasms.
By the method of artificial circulation Winterstein endeavoured
to decide whether this narcosis, since it is capable of suspending
excitatory processes, is able to check the restorative action of oxygen
also. He experimented as follows :—
A strychniuised frog, asphyxiated by the circulation of oxygen-
free salt solution, was anaesthetised by the circulation of salt
solution containing a narcotic (chloroform, ether, alcohol, carbonic
acid). Oxygenated blood mixed with the same narcotic was then
circulated. Under these conditions there was of course no
recovery of the centres, on account of the narcosis. But on
circulating normal saline to remove the drug there was still no
recovery of central excitability, because the asphyxiated nerve-
centres, which had been deprived of oxygen, were unable, owing
to the action of the narcotic, to utilise it when offered them.
Narcosis thus suspends not only the katabolic but also the anabolic
processes. Fr. W. Frohlich observed an analogous effect on peri-
pheral nerve (supra, p. 231). This important fact is explained
by the latest work of Winterstein (1905) as a direct arrest of
the oxidation processes by narcotics, represented in the lower
organisms by an extraordinary fall in the consumption of oxygen
during narcosis.
In another series of researches Winterstein studied the special
state of the nerve-centres known as heat paralysis. When a frog
is warmed in a thermostat, all reactions disappear after a period
of general excitation, owing to a paralysis of the nerve-centres
which passes off if the animal be cooled again in time. Winterstein
found this heat paralysis to be closely related to the oxygen
supply of the centres. If a frog which is in a condition of heat
paralysis be cooled in an atmosphere free of oxygen, or if its
blood be replaced by cold physiological saline containing no
oxygen, the animal is unable to recover from the paralysis.
Recovery, on the contrary, takes place when there is sufficient
oxygen. It follows that heat paralysis must be a form of asphyxia,
due, according to Winterstein, to the fact tliat either the store of
oxygen in the centres or their oxidative processes are insufficient
for the excessive demand produced by the heat.
272 PHYSIOLOGY CHAP.
Further advance in the general physiology of the nerve-
centres was made by Baglioni (1904) with his method of isolating
the spinal cord. This method is much simpler than that of
artificial circulation, and avoids the lesions caused by protracted
artificial circulation, which readily induce oedema and lower the
vitality of the nerve - centres. Baglioni's method consists in
dissecting out the spinal cord by removing the dorsal halves of
the vertebrae, and separating it from the rest of the body, so that
it is only attached by the sciatic nerve and plexus to the leg,
which can be stimulated and used as the index of excitability
on one or both sides. On applying mechanical or electrical
stimuli to the skin, reflex movements are produced in the leg,
since the spinal centres have not been injured by the operation.
Baglioni finds that on placing this preparation in an atmosphere
of pure oxygen, or in physiological saline saturated with oxygen,
it survives and preserves perfect reflex activity for twenty-four
to forty-eight hours. The oxygen tension of atmospheric air is
not enough to maintain its vitality for more than two hours at a
temperature of 18-20° C., as the oxygen can only be absorbed
from the dorsal surface of the cord — the ventral surface being
covered by the anterior half of the vertebrae. Reflex action
disappears in a much shorter time, in about three-quarters of an
hour, if nitrogen is substituted for oxygen, and more rapidly in
proportion as the temperature is higher.
This experiment indicates even more plainly than the last the
great oxygen hunger of the nerve-centres and their capability of
surviving for a comparatively long time with their circulation cut
off and with no supply of organic nutrient materials. The need
of oxygen, which greatly exceeds that of the peripheral nerves, is,
according to other experiments of Baglioni, a characteristic property
of the central nervous system, not only in vertebrates, but in in-
vertebrates also.
Wiuterstein, Baglioni, and Fienga subsequently found that it
was possible to isolate the frog's cord still more completely by
lifting it almost entirely out of the vertebral canal. Total
isolation of the cerebrospinal axis is thus possible in the toad
(Baglioni, 1908), owing to the great length of the cauda equina,
which allows of the necessary manipulation in freeing the cerebro-
spinal axis from its connections without serious injury. Fig. 166
gives the photograph of such a preparation from the toad.
Winterstein (1906) carried out a series of quantitative
estimations of the gaseous metabolism of the frog's isolated spinal
cord by means of Thunberg's microspirometer, which, as shown on
p. 231, makes it possible to measure the carbonic acid given off and
the oxygen absorbed, thus giving the respiratory quotient for small
organs and animals. He concludes that the asphyxial paralysis
of the centres is due, not to the consumption of the reserve
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 273
oxygen, but to an accumulation of products of metabolism, wbicb
have a paralysing action and are easily oxidisable, so that a
proportional amount of oxygen is consumed in neutralising them.
Fn;. Itiij. — Central preparation of toad. (Bullion!.) The posture of the lower liinlis. uliirli arc
exhausted by recent reflex activity, differs from that in a living preparation. The dm-sal surface
of the spinal cord is shown.
He further found that the spinal cord under these conditions
consumes about 250-350 cmm. of oxygen per gramme per hour,
its respiratory quotient being always less than unity.
Two years previous to Verworn, Ducceschi (1898) had made
VOL. in T
274 PHYSIOLOGY CHAP.
use of the method of artificial circulation in estimating the
results produced in the spinal centres of batrachians by salt
solutions at different concentrations. He found that the solution
best adapted to maintain the functions of the spinal centres was
one containing from 0'6 to 1 per cent sodium chloride. Hypertonic
solutions, which contain more than 1*5 per cent sodium chloride,
cause motor paralysis after a brief period of motor excitation
(tetanus, clonic spasms), while hypotonic solutions, which
contain less than 0'6 per cent sodium chloride, cause depression
and loss of excitability, but less rapidly and without any previous
phase of increased excitability. Since hypertonic solutions
withdraw water from the nerve-centres, and hypotonic solutions
cause excess of fluid or oedema in them, these experiments of
Ducceschi show the importance of water for the metabolism of
the ganglion cells.
Morawitz subsequently worked at the same subject with
Verworn, and arrived at the following conclusions which confirm
and partly extend those of Ducceschi : (a) If distilled water is cir-
culated through a strychniuised frog, excitability soon disappears
altogether, to reappear on circulating a physiological saline
solution. (6) Great loss of water from the cord owing to
artificial circulation of a hypertonic solution (2-5 per cent sodium
chloride) increases the reflex excitability in the frog till it
resembles strychnine poisoning, (c) If more water is added to
that contained in the nerve elements, excitability diminishes.
Everything therefore tends to show that the excitability of the
ganglion cells depends to a large extent on their water content.
Battelli extended Ducceschi's experiments to the artificial
circulation of warm-blooded animals (guinea-pigs) in order to
study the influence of water, of certain inorganic salts, and of
glucose upon the nutrition, and therewith the excitability of the
nerve-centres.
The following seem to us to be among the most important
of his results : (a) Artificial circulation of a deoxygenated salt
solution prolongs to some extent the duration of reflex excitability,
which only lasts 70 sees, after tying the aorta. (&) A physiological
solution saturated with oxygen increases the duration of the
reflexes for a variable but not very prolonged period, (c) A
mixture of sodium chloride and calcium chloride solution saturated
with oxygen gives a marked and constant increase in the reflexes.
(d) Potassium and magnesium salts, neutral sulphates and
phosphates are tolerated by the centres, but do not increase the
duration of the reflexes, (e] If the artificially circulated fluid
has even a moderately alkaline reaction due to the carbonate,
bicarbonate, or phosphate of sodium, the vitality of the centres is
rapidly abolished. (/) A deoxygenated solution of sodium or
calcium causes only a slight prolongation of the functions of the
iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 275
nerve-centres. The chief result of Battelli's experiments is that
calcium salts appear to be essential to the gaseous exchanges
between the circulating fluid and the nerve-centres.
Some recent experiments of Sabbatani also confirm the
importance of calcium to the normal functions of the centres of
the cerebral cortex.
Baglioni (1904) further instituted a series of experiments on
his preparation of the frog's isolated spinal cord, with the object
of determining the conditions under which salt solutions are able
to maintain the reflex activity of the nerve-centres. In particular
he investigated the importance of sodium chloride, and found that
it cannot be replaced by any other substance, e.g. glucose, glycerol,
asparagine, etc., or by potassium or lithium chloride at equal
concentration. Sodium chloride can only be replaced to a certain
extent by other salts of sodium (bicarbonate, nitrate).
If the isolated spinal cord is placed in an isotonic solution
which contains, e.g., glucose instead of sodium chloride, its reflex
excitability disappears after a certain time (two to five hours
according to the surrounding temperature), and returns again if
the preparation be immediately plunged into a solution containing
0'6-0-9 per cent sodium chloride. Peripheral nerves react in the
same way.
Lastly, it must be noted that Herlitzka (1909) instituted a
series of researches with artificial circulation through the bulbar
centres of the frog, in order to determine the chemical conditions
of the artificial solutions which are able to maintain their
activity. Among other points, he finds that a series of organic
substances, such as glucose, glycerol, and urea, added to normal
saline enable the centres to survive for a comparatively long time.
He attributes the action of these substances to their solubility in
lipoids.
BIBLIOGRAPHY
The student will find copious references to the early literature of this subject in
HERMANN'S Text-book of Physiology, and to the later in those of SOHAFER and
NAGEL.
Morphology of Nervous System :—
WALHEYER. Deutsche med. "VVochenschr., 1891.
RAMON Y CA.JAL. Revista de cientias medicas de Barcelona, nuras. 16, 20, 22, 23,
1892. Arch, di fisiol. vol. v., 1908.
NISSL. Allgem. Zeitschr. f. Psychiatric, vol. xlviii., 1892.
APATHY. Mitteil. a. d. zool. Station zu Neapel, 1897.
BETHE. Arch. f. mikrosk. Anat., 1897. Morphol. Arbeiten von Schwalbe,
vol. viii., 1898. Biol. Centralblatt, xviii., 1898. Arch. f. mikrosk. Anat.
vol. Iv., 1900. Allg. Auat. u. Physiol. d. Nervensystems. Leipzig, 1903.
ROBERTSON. Brain, Part Ixxxvi., 1899.
GOLGI. Boll, della Societa Med. Cliir. di Pavia, 1898-99. Verhandl. d. anat. Ges.
XIV. zu Pavia, 1900. Arch, di fisiol. vol. iv., 1907. Atti della Soc. ital. p. il
progresso d. scienze, III. Riunione, 1910.
DONAGGIO. Riv. sper. di freniatria, 1896, 1900, 1904, 1905, 1908. Int. Congress
of Physiology. Turin, 1901; Brussels, 1904.
276 PHYSIOLOGY CHAP.
PURPURA. Bollettino della Society, medico-chirurgica di Pavia, 1901. Rendiconti
del K. Istituto Lombardo di Scienze e Lettere, serie ii. vol. xxxiv., 1901.
Archives italicnnes de biologie, fasc. xxxv., 1901. Arcliivio ed atti della
Soeieta italiana di Chirurgia, 1909. Arcliivio ed atti della Soeieta italiana di
Chirurgia, 1911.
PERRONCITO, A. Mem. del R. Istituto Lombardo di Sc. e Lett; ; Classe delle Sc.
mat. e nat. vol. xx., 1908.
VERWORN, W. Zeitschr. f. allg. Physiol. vol. vi., 1906.
MODENA. Bull, dell' Ace. medica di Roma, 1910.
Excitability and Conductivity of Nerve : —
HELMHOLTZ. Arch. f. Anat. u. Phys., 1850-52.
GRUTZNEU. Pfliiger's Archiv, vol. xxviii., 1882.
ZEDERBAUM. Du Bois-Reymond's Arch., 1883.
KUHNE, W. Zeitschr. f. Biologie, 1886. Ueber die Wirkung des Pfeilgiftes auf
die Nervenstiimme. Heidelberg, 1886.
GOTCH and HORSLEY. Phil. Trans., 1891.
BERNSTEIN. Untersuchungen iiber den Erregungsvorg. im Nerven- u. Muskel-
system, 1891.
WEDENSKY. Pfliiger's Archiv, vol. Ixxxii.. 1900.
DUCCESCHI. Pfliiger's Archiv, vol. Ixxxiii., 1900.
FRUHLICH, FR. W. Zeitschr. f. allg. Physiol. vol. iii., 1904.
THHRNER, W. Ibidem, vol. viii., 1908.
Electrophysiology of Nerve : —
MATTEUCCI. Traite des phenomen.es electro-phys. des animaux. Paris, 1844.
Du BOIS-REYMOND. Untersuchungen liber thier. Electr. Berlin, 1848.
PFLUGER. Untersuchungen iiber die Physiol. des Electrotonus. Berlin, 1859.
BERNSTEIN. Untersuchungen iiber den Erregungsvorgang im Nerven- und Muskel-
system, 1871.
WUNDT. Untersuchungen z. Median, d. Nerv. u. Nervencentren. Stuttgart,
1876.
TIGERSTEDT. Mitt. v. physiol. Lab. in Stockholm, vols. i. -iii., 1882-85.
BIEDERMANN. Elektrophysiologie. Jena, 1895. (English Trans, by F. A. Welby,
1896).
HERMANN. Pfliiger's Archiv, vols. vi., vii., viii., xxx., xxxi., xxxiii., xxxv.,
Ixii., 1872-98.
WALLER. On Animal Electricity. London, 1897.
GOTCH and BURCH. Proc. Roy. Soc. London, vol. Ixiii., 1898.
BORUTTAU. Pfliiger's Archiv, vols. Iviii., Ixiii., Ixvii. , Ixxi., Ixxxiv., cv., 1894-1904.
General Physiology of Nerve-Centres :—
NISSL. Allg. Zeitschr. f. Psychiatrie, 1892.
LUGARO. Rivista di pat. nervosa. Firenze, 1896.
MARINESCO. Presse medicale, 1897. Arch. f. Physiol., 1899.
DUCCESCHI. Sperimentale, Iii., 1898.
WINTERSTEIN. Du Bois - Reyinond's Arch., 1900; Supp*- Zeitschr. f. allgem.
Physiol. i. , 1901 ; v., 1905 ; vi., 1906.
VON BAEYER. Zeitschr. f. allgem. Physiol. i., 1901.
BATTELLI. Journal de physiol. et de path, gen., 1900.
VERWORN. Du Bois - Reymond's Arch., 1900; Supp*- Die Biogenhypothese.
Jena, 1903.
BAGLIONI. Du Bois -Reymond's Arch., 1900. Zur Analyse der Reflexfunktion.
Wiesbaden, 1907. Zeitschr. f. allg. Physiol. ix. and x., 1909.
HERLITZKA, A. Arch. d. fisiol. vol. vii., 1909.
Recent English Literature :—
KEITH LUCAS. Temperature Co-efficient of the Rate of Conduction -in Nerve.
Journ. of Physiol., 1908, xxxvii. 112.
BRODIE and HALLIBURTON. Heat Contraction in Nerve. Journ. of Physiol., 1904,
xxxi. 473.
iv GENEKAL PHYSIOLOGY OF NEKVOUS SYSTEM 277
ADRIAN. On the Conduction of Subnormal Disturbances in Normal Nerve.
Journ. of Physiol., 1912, xlv. 389.
MKEK and LEAPER. On the Effects of Pressure on the Conductivity in Nerve and
Muscle. Amer. Journ. of Physiol., 1911, xxvii. 308.
KKITH LUCAS. On the Sunimation of Adequate Stimuli in Muscle and Nerve.
Journ. of Physiol., 1910, xxxix. 461.
GOTCH. The Delay of the Electrical Response of a Nerve to a second Stimulus.
Journ. of Physiol., 1910, xl. 250.
ADRIAN and LUCAS. On the Summation of a Propagated Disturbance in Nerve
and Muscle. Journ. of Physiol., 1912, xliv. 68.
KEITH LUCAS. On the Refractory Period of Nerve and Muscle. Journ. of Physiol.,
1909, xxxix. 331.
SCOTT. On the Relation of Nerve Cells to Fatigue of their Nerve Fibres. Journ.
of Physiol., 1906, xxxiv. 145.
HALLIBURTON. Biochemistry of Nerve and Muscle. London, 1904.
ALCOCK and LYNCH. On the Relation between the Physical, Chemical, and
Electrical Properties of the Nerves. Journ. of Physiol., 1910, xxxix. 402 ;
and 1911, xlii. 107.
SCOTT. On the Metabolism and Action of Nerve Cells. Brain, 1905, xxvii. 506.
KEITH LUCAS. On the Recovery of Muscle and Nerve after the Passage of a
Propagated Disturbance. Journ. of Physiol., 1910, xli. 368.
ADRIAN. Wedensky Inhibition in Relation to the " All-or-None" Principle in
Nerve. Journ. of Physiol., 1913, xlvi. 384.
HEAD, RIVERS, and SHERREX. The Afferent Nervous System from a New Aspect.
Brain, 1905, xxviii. 99.
HEAD and RIVERS. A Human Experiment in Nerve Division. Brain, 1908,
xx xi. 323.
CHAPTER V
SPINAL CORD AND NERVES
CONTENTS. — 1. Grey and white matter of the spinal cord. 2. Extra- and intra-
spinal nerve-cells ; their connections with the root-fibres and tracts which ma.ke
up the spinal columns. 3. Spinal roots. Bell-Magendie law of localisation of
sensory and motor tracts. Waller's law of degeneration after section. 4. Func-
tional relations between afferent and efferent roots. 5. Segments] arrange-
ment of .spinal roots. 6. Reflex activity of segments of cord ; shock after section
of cord. 7. Short and long spinal reflexes; laws of reflex spread. 8. Genesis of
spinal reflexes ; central factors that inhibit or promote them. 9. Tonic and
automatic functions of spinal cord ; " knee-jerk" or patellar reflex. 10. Trophic
functions of spinal cord. 11. Sensory functions and Pfliiger's "spinal soul."
1'2. Spinal cord an instrument of the brain ; spino-cerebral and cerebro-spinal
paths of conduction. 13. Localisation of principal spinal centres ; phenomena of
spinal deficiency (dogs with amputated cord, Goltz). Bibliography.
BlCHAT distinguished two main parts of the nervous system,
the Cerebrospinal System and the Splanchnic or Sympathetic
System. The first regulates the relations between the organ-
ism and the external world and presides over the functions
of animal life; the second controls the relations between the
respective organs, and presides over the functions' of vegetative
(or visceral) life. Acceptable as this dualistic conception of
the nervous system may be in the abstract, it should be clearly
recognised that it goes too far, and gives rise to error in the
localisation and definition of the boundaries between the two parts
of the system. The cerebrospinal axis is not completely detached
from the sympathetic system. While the two are quite distinct
at the periphery to which both are distributed, they intermix in
the central nervous system and fuse into a single system. The
cerebrospiual axis controls the functions of animal life, but is not
thereby excluded from the control of the visceral organs also ; on
the other hand, the sympathetic does not represent the entire
nervous system of visceral life, but only that part of it which lies
outside the cerebrospinal axis. It may thus be treated as the
part of the latter which is distributed in the form of gangliated
plexuses to the visceral organs. Experimental analysis shows
fundamentally the same nervous mechanisms in the ganglia of the
sympathetic as exist in the spinal cord.
278
CHAP. V
SPINAL COED AND NEEVES
279
I. The spinal cord, 'which occupies
the whole extent of the vertebral canal
in the early months of foetal life, ex-
tends in the adult from the foramen
occipitale magnum to the lower edge
of the first lumbar vertebra, and has
an average length of 45 cm. (Fig. 167).
There is a corresponding segment
or metamere of the spinal cord with
two pairs of nerves connected with it
for each segment of the vertebral
column. But the metamerism of the
roots must be distinguished from the
metamerism of the cord. The former
is a true and perfect metamerism,
because each pair of nerves (neuromcrc')
FIG. 167. — Diagrammatic view from before of spinal cord
and medulla oblongata, including the roots of tin?
s]iinal and some of the cranial nerves, and on one side
the gangliated chain of the sympathetic. (All™
Thomson.) J. The spinal nerves are enumerated in
order on the right side of the figure. Br, brachial
plexus ; Or, anterior crural ; 0, obturator ; and Sc, great
sciatic nerves, coming off from lumbo-sacral plr.xus ;
X, X> filum terminale; a, b, c, superior, middle, and
inferior cervical ganglia of the sympathetic, the last
united with the 1st thoracic, il : <l' , the llth thoracic
ganglion ; I, the 12th thoracic (or 1st lumbar) ; below
ss, the chain of sacral ganglia.
is in relation at the periphery with
definite and circumscribed portions of
groups of muscles (myomeres) and
cutaneous areas (dermatomeres}, as we
shall see in discussing the peripheral
distribution of the spinal nerves. In
the spinal cord, on the other hand,
metamerism is reduced to its lowest
terms. Originally independent, during
phylogenetic and ontogenetic evolution
the spinal segments (myelomeres) have
fused, and their functions have mingled.
What remains of their primary inde-
pendence is confined to the intimate
functional connection that exists in
carrying out the simplest reflex acts
between the ventral and the dorsal
roots of the same spinal segment.
Fig. 168 shows the natural appear-
ance of a segment of the cord, with
the corresponding pair of spinal nerves
Cl
Hr
IS*-'
a
J2
ss)
280
PHYSIOLOGY
CHAP.
issuing from it by two distinct roots. The ventral root consists of
a larger number of slender bundles ; the dorsal root contains a
smaller number of thicker bundles. The roots on the two sides
are never perfectly symmetrical. The ventral roots (excepting
those of the first cervical pair) are as a whole smaller than the
dorsal roots and probably contain a smaller number of fibres.
This was in fact determined by Birge on two frogs, in which the
dorsal roots contained, respectively, 3781 and 5335 fibres, and the
ventral roots 3528 and 4283 fibres.
FIG. 168. — Different views of a portion of the spinal cord from the cervical region with the roots of
the nerves. Slightly enlarged. (Allen Thomson.) In A the anterior or ventral surface is
shown, the ventral nerve-root of the right side having been divided ; B, view of the. right side ;
C, the upper surface ; D, nerve-roots anil ganglion from below. 1, ventral median tissm r ;
•2, dorsal median fissure; 3, ventro - lateral impression, over which the bundles of the
ventral nerve-root are seen to spread (too distinct in figure) ; 4, dorso-lateral groove, into which
the bundles of the dorsal root are seen to sink ; 5, ventral root ; 5', in A, ventral root divided
and turned upwards ; ii, dorsal root, the fibres of which pass into the ganglion, 6' ; 7, united
or compound nerve ; 7', dorsal primary branch, seen in A and D to be derived partly from
ventral, partly from dorsal root.
In vertebrates the length of the individual segments of the
spinal cord is not, as a rule, equal to the height of the correspond-
ing vertebrae ; it usually decreases from above downwards, so that
the length of the spinal cord only amounts to three-quarters that
of the vertebral canal. The successive roots in descending series
have therefore a more oblique longitudinal course, and travel
farther before they reach the corresponding intervertebral foramina.
The lower part of the vertebral canal merely contains a mass of
nerve-roots known as the cauda cquina.
The cervical enlargement of the cord, which comprises the
reoion of the roots that make up the brachial plexus, is largest at
SPINAL CORD AND NEEVES
281
the height of the 5th and 6th cervical vertebrae and ends at the level
of the 2nd and 3rd thoracic vertebrae. The lumbo-sacral enlarge-
ment, which comprises the segments that send roots to the lumbo-
sacral plexus, begins at the level of the 10th dorsal vertebra and is
largest at the level of the 12th. Next comes the conus wcdulhiris,
which terminates at the level of the 1st or 2nd lumbar vertebra
in the hlum terminate, by which the cord is attached to the
coccyx.
The cord as a whole is enclosed in a sheath (thcccC) formed of
a dense fibrous membrane, the dura mater, which is attached to
Ml
KK.. li'i'.i.— Diagrammatic transvrisr section of spinal cord. (Er-l>.) o, tissur:> longitudinalis ventralis ;
h, f. 1. dorsal; e, ventral column; rf, lateral column; e, dorsal column; ./, t'linieulus .Lji-acili.s ;
ij, fimiculus cuneatus ; h, ventral; t, dorsal root; k. central canal; /, suleus intermedius
dorsalis: «i, ventral horn; H, dorsal horn; o, traetus intermedio - lateralis ; <', lu-ni/essus
ivt ienlaris ; a, wliite or ventral commissure; r, grey or dorsal commissure; s, Clarke's
column or coliimiia vesicularis.
the periosteum that lines the interior of the vertebral canal.
Enclosed in the dura mater, the cord is protected against external
pressure, and readily gives, without undue strain, to the twisting
and displacement caused by the movements of the vertebral
column. In fact there is a space between the dura mater and the
cord, filled with a lymphatic fluid known as the cc rebro spinal fluid,
which is continually formed as fast as it diffuses through the
lymphatic spaces in the spinal roots.
Inspection of a transverse section of the spinal cord (Fig. 169)
shows the arrangement of the central grey matter and the
peripheral white matter, but comparison of a series of transverse
sections made at different levels (Fig. 1*70) shows that different
regions present special characteristics and variations in form,
282
PHYSIOLOGY
CHAP.
and in the relative quantity of grey and white matter, particularly
in the region of the cervical and lumbar enlargements.
By means of Otto Stilling's table of planirnetric measurements
of the cross-sections of single spinal roots, of the grey and white
matter, and of the different bundles at the level at which each root
FIG. 170.— Transverse section of spinal cord at dim-rent heights. (W. R. Cowers.) Twice the
natural si/e. The letters and numbers indicate the position of each section; Co, at level1 of
fnrry.U'Ml nerve; Sac.4, of 4th sacral; L3, of 3rd lumbar, and so on. The grey substance Is
shaded dark, and the in-i vc-erlls within it are indicated by dots.
emerges, Woroschiloff constructed the diagrammatic curve of
Fig. 171, iu which the abscissa represents the points at which the
roots emerge, while the ordinates indicate the sectional areas of
the grey matter, the roots, and the different columns (dorsal,
lateral, ventral). The first curve (<jr] shows the increase of grey
matter near the lumbar and cervical enlargements. The second
SPINAL CORD AND NEKVES
283
curve (nr) shows that the sectional areas of the spinal roots also
increase at the two enlargements, so that there is a certain ratio
between the number of the root-fibres and the amount of grey
matter in the corresponding segments of the cord. The three last
curves (pc, Ic, ac) show that the white matter of the cord,
particularly that of the lateral and dorsal columns, gradually
increases in bulk from below upwards.
The nerve-cells are not uniformly distributed in the grey
matter, but are collected into groups which occupy definite and
approximately constant positions in the different regions, in which
they form columns of cells. The largest ganglion cells are in the
ventral part of the ventral horn. They increase in number at the
level of exit of each ventral root, especially in the thoracic region
of the cord, which indicates its metameric origin. They also
FIG. 171.— Diagram to show relative and absolute size of sections of the grey matter, white
columns, and spinal roots at different levels of the spinal cord. (After Woroschiloff.) The
sections of the different roots (w.r.), grey matter ((jr.), and lateral, dorsal, and ventral columns
(I.e., p.i.:, «.<•.) are represented by curves, their common abscissa beiu.u intersected by ordinates,
each of which corresponds to a pair of spinal nerves. In the ordinates each mm. of rise above
the abscissa line corresponds to about 1 sq. mm. area of section.
increase in number in the two enlargements, parallel with the
increased size and number of fibres of the ventral roots in
these parts.
Another group of cells, distinct from the preceding, is found
in the lateral horn, mainly in the thoracic segments, where the
lateral horn appears as a distinct formation. Its cells are smaller
than those of the preceding group, and are generally spindle-
shaped, with their larger axes directed towards the apex of the
horn.
The two dorsal grey horns, again, have at their base, particularly
in the thoracic region, a well-defined oval group of ganglion cells,
which are smaller than those of the ventral horn. This is the
so-called columna vesicularis or Clarke's column. In the cervical
segments and lower part of the lumbar cord it is represented by
the cervical nucleus and the sacral nucleus of Stilling respectively.
And in other parts of the spinal cord there are found the so-called
284 PHYSIOLOGY CHAP.
solitary cells, which from their form and character must be also
regarded as belonging to this group.
The chief characteristic by which the cells of the grey matter
of the cord are distinguished from those of the inter-vertebral
and sympathetic ganglia is the branching of their processes into a
vast number of very fine filaments, similar to the ramifications of
the delicate fibrils by which the axis-cylinders of the peripheral
nerves terminate in the tissues.
The nerve-fibres of the columns of the white matter of the
cord have medullated sheaths, but no sheath of Schwann. They
vary considerably in diameter ; the largest are in the ventral
roots and outer parts of the lateral columns ; those of the dorsal
roots and columns are smaller ; smaller still those of the anterior
commissure and the parts of the lateral columns near the grey
matter.
The general direction of the fibres is transverse in the roots,
longitudinal in the columns, oblique in the commissures, but in the
grey matter the medullated fibres interlace in all directions, both
individually and when collected into bundles, while its fine non-
medullated fibres form an inextricable felt-work.
The white matter is traversed by a number of radial septa,
along which the marginal vessels penetrate into the cord. These
septa consist of neuroglia which also supports the medullated
nerve-fibres in a loose network and forms a denser net in the
grey matter. The neuroglia is particularly rich in the substantia
gelatinosa, which surrounds the central canal of the cord and
covers the cap of the dorsal horn. It is epiblastic in origin,
and as it consists of keratin, it is very resistant to artificial
digestion.
II. As the minute structure of the cord and the still unsettled
questions of anatomy are not the business of the physiologist, we
must confine ourselves to such facts as are more particularly of
physiological interest.
One of the best-established anatomical facts is that the fibres
of the ventral roots represent the processes or axis-cylinders of
ganglion cells that lie in the grey matter of the ventral horn of
the same side (Deiters, 1865). Some of these root fibres, however,
pass through the ventral commissure and form connections with
the cells of the ventral horn on the opposite side.
The fibres of the dorsal roots, on the contrary, are not directly
connected with the cells of the dorsal horn, but are processes of the
spinal ganglion cells. These cells usually have a single process, which
divides after a short course into two branches, one of which passes
to the periphery through the spinal nerves, while the other branch
passes to the cord as the dorsal or posterior root. Almost all the
fibres of this root divide on reaching the cord (Eamon y Cajal and
Kolliker) into two main branches, one ascending, the other
SPINAL COED AND NEEVES
285
descending in the dorsal column and the region round the dorsnl
horn (Fig. 172). Both these branches give off collaterals at fairly
close intervals, which run towards the grey matter, penetrate it,
and ramify around its cells. Some of these collaterals run to the
cells of the ventral horn on the same side ; others enter into
direct relation with the cells of
Clarke's column or the solitary
cells of the dorsal horn.
To summarise the facts most
essential to physiology : The fibres
of the peripheral nerves which
emerge by the ventral roots have
their cells of origin in the ventral
horn of the cord, and those which
enter by the dorsal roots originate
not from the cells of the cord, but
from the spinal ganglia. In the
grey matter of the cord the nerve-
tibres of the two roots are closely
related, so that transmission of the
excitations from one root to the
other is possible, either by simple
contact between the ends of the
neurones, or by the anastomosis of
the neurones among themselves
into a common fibrillary network.
Lastly, the nerve-fibres which make
up the dorsal white column of the
cord are the prolongation of the
peripheral fibres that enter by
the dorsal roots ; but the fibres
that constitute the ventro-lateral
columns are independent of the
peripheral neurones.
Investigations on the embryo-
logical development of the spinal
cord, pathological observations on
spinal diseases in man, and the
effects of partial sections of the
cord in animals, have yielded the
highly important result that the columns which make up the
white matter of the cord are not uniform masses of nerve-fibres, but
can be subdivided into well-differentiated bundles or tracts. The
enibryological investigations of Flechsig led to the very important
conclusion that the development of the myelin sheath does not
take place simultaneously on all the longitudinal fibres of the
spinal cord, but it occurs earlier in certain bundles or tracts of
FIG. 172.— Longitudinal section of dorsal
column of spinal cord of chick on eighth
day of incubation. (Ramon y Cajal.)
Shows the course of five entering fibres
of dorsal root, and some longitudinal
fibres of ventral column. A, A, fibres of
dorsal root; B, bifurcation of one in
form of Y ; C, D, origin of collateral
branches ; B, fibres of Qoll's tract, also
giving oft' collaterals.
286
PHYSIOLOGY
CHAP.
fibres than in others, as partially shown in Fig. 173. By this
means certain tracts can be distinguished.
Corresponding results are obtained from the study of the
ascending and descending degenerations observed in cases of spinal
disease, or experimentally produced in animals. In cases of hemi-
plegia from cerebral apoplexy complete degeneration of the pyram-
idal tract is seen in the cord (Fig. 174). After transection of an
upper thoracic segment (Fig. 175) descending degeneration of both
pyramidal tracts can be followed to the lumbo-sacral cord, and
ascending degeneration of the columns of Goll and the cerebellar
O O
. . : • . "f*-A-*-WM •*" ••'
^£i$jj%jjf%r' • &'•
'-• - . ^^&.^/f '•*; ., •£$
^Vor
S^un
del-
i<
\
\
li $_JLV
FIG. 173. — Section of spinal curd of new-born animal. The pyramidal tracts which are not yet
m\ i-linated an- rli-ar and transparent. The pyramidal tracts of the ventral column extend to
the periphery of tin- ventral lateral column. (Edin^vr.) ll'ni-;el-ZotiK = root-zone ; Grenz-
scliicht = limiting layer; KleinKirnseitenstrang-Bahn=d.\'KC\ cerebellar tract; Seitenstrtiity-
Vorderstrang-Grwndbiindel=groiui<l bundle of lateral and ventral column.
tracts through the cervical segments. Other ascending and
descending degenerations are observed with other diseases, or as
the result of injuries or experimental lesions.
The methodical study of cross-sections of the different segments
of the cord, both in cases of pathological or experimental degenera-
tion and in the embryonic cord at different periods of develop-
ment, has made it possible to distinguish the two categories of
fibres in the white columns. The first consists of tracts, the
sectional area of which increases continuously from below upwards
by constant addition of new fibres. In the second the tracts do
not increase from below upwards, but vary in diameter in different
regions according to the bulk of the corresponding spinal roots.
The bundles in the first group represent the long conducting
paths, spino-cerebral and cerebro-spinal, which directly connect
V
SHNAL COED AND NEEVES
287
the different segments of the cord with the brain, or the different
regions of the brain with
the cord. The bundles in
the second group, on the
other hand, are the short
intraspinal ascending or
descending paths which
connect together different
elements of the cord at
different levels.
We must glance at
the principal facts in
regard to the nature and
relations of the main
tracts in the two
groups :—
(a) The pyramidal
tracts are composed of
the axis-cylinders of cells
in the Eolandic area of
the cerebral cortex. They
pass through the internal
capsule, cerebral ped-
uncle, and pyramids of
the medulla oblongata,
where most of the fibres
decussate before descend-
ing in the form of a
compact bundle in the
dorsal portion of the
lateral column (crossed
lateral pyramidal tract).
A small number of these
fibres which do not cross
in the bulb descend on
both sides of the ventral
median i fissure as the
direct pyramidal tract
described by Tiirck ; this
usually ends about half-
way down the thoracic
COrd. The fibres Of the FIG. 174. — Secondary de- FIG. 17">.— Sre.m.lary ascend-
. j -, p/, scending degeneration due ins; and descending de-
pyraniiual tracts give Oil to a lesion in left cerebral generations due to lesions
pnl'htpri'h nlrrncr thpir licniisi.liere. (After Erb.) of upper thoracic cord.
(After Sti mnpell.)
course, which arborise
around the cells of the ventral roots, so that each fibre is able
to convey excitations to a series of cells which are distributed
c—
288 PHYSIOLOGY CHAP.
along the different segments of the ventral grey matter. It is
probable that some at least of the collaterals of the direct
pyramidal tract decussate in the cord, and pass to the opposite
side through the ventral commissure, before they enter into
relation with the cells of the ventral roots.
As shown by Fig. 174 the pyramidal fibres undergo a descend-
ing degeneration, but this never extends to the fibres of the
ventral roots so long as the cells of the ventral horn remain
intact.
(b) Two bundles can be traced from the lateral column to the
cerebellum : one, described by Marchi, undergoes descending
degeneration after extirpation of the same side of the cerebellum
(direct ventro-lateral cerebellar tract); the other, described by
Flechsig, degenerates in the ascending direction, after lesions of
the lateral part of the cord (direct dorso-lateral cerebellar tract).
The former, as shown by Fig. 176, occupies
in dogs the ventral three-fourths of the
veutro-lateral column, and also dips in-
wards in front of the crossed pyramidal
tracts. [More recent investigations have
proved that it does not take origin in
the cerebellum, but from cells of the brain-
stern that lie immediately Ventral to it.,
no. i76.-section of s,,inai cord and chiefly from Deiter's nucleus.— ED. ]
(inmiiai region) of dog, killed ^\IQ direct ascending cerebellar tract
three months alter removal of -,i-,r-\ • i • i- •
right half of cerebellum, (rig. l/o) IS better knOWll ; it llCS in
LMsahaded^thdotr the dorsal margin of the lateral column,
and increases in size as it ascends, till on
reaching the sides of the bulb it passes through the restiform
body to the median lobe of the cerebellum.
The fibres of Flechsig's cerebellar tract originate from the cells
of Clarke's column on the same side, and therefore degenerate
upwards.
(c) Gowers identified another important tract, which occupies
an irregular area in the lateral column in front of the direct cere-
bellar tract and the crossed pyramidal tract, and is known as the
ventro-lateral ascending bundle (Fig. 177). This tract grows larger
as it ascends; it. can be followed into the bulb and pons Varolii.
After lesions of the lumbar segments it undergoes ascending
degeneration. Its cells of origin are probably in the dorsal horn.
We shall return to the significance of this bundle in considering
the effects of partial transverse section of the cord.
(d~) Each dorsal column contains two bundles, which are
separated anatomically by a septum from the middle of the
thoracic region upwards : the funiculus gracilis or column of Goll
occupies the medial dorsal part, and the funiculus cuneatus or
tract of Burdach the lateral part of the column. We have
SPINAL COED AND NERVES
280
already said that the fibres of the dorsal columns are the direct
continuation of the dorsal roots, which originate in the cells of
the spinal ganglia. The fibres of the tract of Goll are small
in diameter, and many of them, instead of entering the grey
matter of the cord, run as far as the medulla oblongata, where
they terminate in a special nucleus of grey matter (nucleus of
the funiculus gracilisj. The tract of
Burdach consists of larger fibres which
send numerous collaterals to the grey
matter, and penetrate into it after a longer
or shorter course, coming into intimate
relation with the cells of Clarke's column.
Both these tracts undergo ascending de-
generation after section or compression of
the cord, or severance of the dorsal roots.
Goll's tract, which is myelmated later,
contains the longer paths which arise
from the lumbo-sacral and lower thoracic
roots ; while Burdach's tract, for the most
part, consists of short intraspinal paths,
with longer fibres derived from the higher
thoracic and cervical roots, which do not
enter the tract of Goll, and terminate in
the nucleus of the funiculus cuneatus or
nucleus of Burdach in the bulb. Thus
the two bundles of the dorsal column are
composed principally of exogenous fibres
or spino-cerebral paths of conduction, but
they also contain endogenous fibres or
intraspinal paths.
(e) The endogenous intraspinal fibres
are represented mainly by the portions
of the white matter adjacent to the grey.
Such is probably the character of the zone Fio. ivT.-As^ndm,^ degeneration
of fine fibres which fills the area between
the ventral and dorsal horns, termed by cowers, after
Sherrington and Grlinbauni the lateral
limiting layer (Fig. 178, I. n. 5). But a
certain number of intraspinal fibres with a short course are inter-
spersed among the fibres of the crossed pyramidal tract. They
are distinguished from the latter by their earlier myelination, and
by the fact that they do not degenerate with them (Miinzer).
The so-called ground bundle of the ventro- lateral column
occupies a sectional area that varies with the area of the grey
matter. Probably many of its fibres are interspinal and serve to
connect the grey matter of different segments of the cord.
The ventral zone of the dorsal column consists of fibres whose
the
cord at the 1st liiinluii1
m^nt. (Gowers.)
VOL. Ill
u
290
PHYSIOLOGY
CHAP.
cells lie in the dorsal horn ; they do not degenerate with the other
parts of the same columns, and are probably also endogenous
internuncial fibres.
Certain cells of the intraspinal system have axis -cylinders
that cross with those of the other side, through the dorsal white
commissure.
(/) In addition to the cells which are the trophic centres for
the fibres of the ventral roots and the white matter, the grey
matter of the cord also contains numerous fibres, which traverse
it in every direction, forming a close plexus. Many of these are
collaterals of the long and short paths of the white matter. The
observations of Sherrington and of G. Mingazzini show that some
A B
Km. 178. — Section through A, cervical, B, lumbar cord, to show approximate limits of the respective
systems of the spinal cord, as shown by embryological research, and principally from prepara-
tions of secondary degeneration in one or other of the systems. (Edinger.) la, pyramidal
tract of lateral column ; 1, pyramidal tract of ventral column ; 2, ground-bundle of ventro-
lateral bundle; 3, ventro-lateral cerebellar tract; 4, dorsal cerebello-spinal tract; f), external
limiting layer of grey matter ; 0, column of Burdach ; 7, column of Goll ; 8, zone of entry of
roots ; 9, ventral area of dorsal columns.
of them degenerate after ablation of the Eolandic area of the
cerebral cortex, as a result of degeneration of the pyramidal tracts.
Schiff assumed long conducting tracts for sensations of pain
in the grey matter ; but nowadays only short paths are recognised
in it. Painful impulses may traverse the fibres of the grey
matter, but they emerge after a short course and run up the
lateral columns of the opposite side, probably in the region of the
tract of Gowers.
III. From the standpoint of general physiology the spinal
cord may be regarded as a highly complex organ — or, better, a
series of intimately connected segmental organs — which receives
all the excitatory impulses arising at the periphery, except from
the head, by centripetal paths, and reflects them directly by
centrifugal paths, or else conducts them farther to the central
stations of a higher order, situated in different regions of the
brain. Nearly all spinal acts, strictly so-called, present under
v SPINAL CORD AND NERVES 291
normal conditions the character of reactions induced by external
influences, in the form of movements which are adapted to adjust
the organism temporarily to its environment. In a word, the
reflex act is the elementary nervous process that underlies the
most complex activities of the spinal system. Many of the spinal
acts commonly termed automatic or spontaneous, since they appear
to be independent of external influences, are classed by other
authors among reflex actions, the distinction between reflex and
automatic acts having varied at different periods and in different
schools. To this we shall return later.
The first question before entering on the study of the spinal
reflexes is to determine whether sensation and movement depend
on separate nerve-fibres or not, i.e. are the sensory impulses from
the periphery to the cord conducted by the same fibres as those
which conduct motor impulses from the cord to the muscles ?
From remote antiquity it has been assumed that the sensations
and the movements of animals depend on distinct nerve-fibres.
Herophilus and Erasistratus, as well as Galen, affirmed this from
their clinical observations, and from the varying effects of injury,
which abolished now sensibility, now motility, and by irritating
the former produced pain, or, by exciting the latter, convulsions.
" There are nerves," said Galen, " to the muscles and others to the
skin : when the former are affected, movement is abolished, when
the latter, sensibility."
The next question is whether the motor and sensory nerves
enter and leave the cord together or separately. Starting from
the anatomical fact that the spinal nerves emerge by two distinct
roots from the cord, Walker (1809) was happily inspired to
attribute different functions to these roots. But as he made no
experiments he fell into the error of attributing sensation to the
ventral, and motor functions to the dorsal roots. In the same
year the celebrated naturalist Lamarck hit on the same idea,
but did not actually determine the function of either root. The
first experimental research in this matter was made by Charles
Bell (1811). But as he worked with freshly killed rabbits he
was unable to establish the function of the dorsal roots, and
merely succeeded in demonstrating the motor nature of the ventral
roots. Convincing proof of the different functions of the two roots
was not forthcoming for another ten years, when it was afforded
by the work of Magendie, Job. Miiller, Panizza, Longet, and
Claude Bernard.
In 1822 Magendie discovered that cutaneous sensibility is
abolished in the regions supplied by the fibres coming* from
divided dorsal roots, while it is unimpaired when the ventral roots
are cut. He exposed the posterior portion of the cord in very
young dogs, divided the lumbar and sacral dorsal roots on one
side, and closed up the wound. At first the limb on the operated
292 PHYSIOLOGY CHAP.
side, besides being insensitive, appeared to be completely paralysed;
but after a few minutes distinct movements were visible. In
other experiments Magendie cut the ventral roots on one side
and left the dorsal, when he noted that the corresponding limb,
while totally immobile and flaccid, preserved its sensibility intact.
He concluded that the posterior roots were more especially
connected with sensibility, the anterior roots more particularly
with movement.
Magendie's experiments were the necessary complement to
those of Bell, who affirmed nothing as to the sensory properties
of either root. The merit of this discovery is undoubtedly shared
by both investigators.
On repeating and varying his experiments, Magendie did not
always obtain such clear results as the above, and he published
his doubts with commendable scientific integrity. But they were
soon removed by the subsequent experiments of other workers on
animals more easily operated on than dogs. The most classical
demonstration of the Bell - Magendie law was given by Joh.
Miiller on the frog, in which it is possible to expose the entire
cord without serious functional depression. Mltller's frog, familiar
to every student of physiology, shows on one side complete
paralysis of movement with intact sensibility, on the opposite
side complete paralysis of sensibility with intact movements,
when all the ventral roots are cut on the one side, all the dorsal
on the other.
The complete evidence for the Bell -Magendie law may be
summed up as follows :—
(a) On exciting or dividing a ventral root, there is a
localised contraction in the muscle or muscles innervated by
that root. (&) The same effect is obtained on stimulating the
peripheral stump of the same ventral root by any stimulus,
(c) No effect, on the contrary, is obtained when the central stump
is stimulated. (YZ) Motor paralysis of the whole limb follows on
section of all the ventral roots that innervate its muscles.
(e) Signs of pain (cries, or more or less diffuse reflex movements)
are obtained on exciting or dividing any dorsal root. (/) The
same effect is produced by exciting the central stump of the same
divided root. (#) Excitation of the peripheral stump has no effect.
(Ji) After cutting all the dorsal roots that innervate a limb it is
found to be totally insensitive.
The Bell-Magendie law holds for every class of vertebrate. It
was established for batracians by the experiments of Joh. Miiller,
Panizza, and Fodera ; for birds by those of Panizza, Moreau, and
Schiff ; for fishes by those of Wagner, Stannius, and Moreau.
This original formula had to be revised as soon as it became
clear that the nerves of the sympathetic system, which serve the
visceral organs, have as much a spinal origin as the somatic sensory
v SPINAL CORD AND NERVES 293
and motor nerves. Besides the motor nerves to skeletal muscles,
the motor nerves to plain muscle (intestine, excretory ducts, bronchi,
vessels), the secretory nerves, the inhibitory or dilatator nerves,
etc., must all be taken into consideration. All these nerves were
included in the common category of centrifugal or efferent nerves.
On the other hand, besides the nerves of general or specific sense,
the excitation of which produces conscious sensations, other nerves
that transmit impulses from the periphery to the centres, and do
not evoke any appreciable sensation, had to be recognised. Both
these groups of nerves were included in the general category of
centripetal or afferent nerves. The most general and compre-
hensive formula for the Bell-Magendie law must therefore run :
the ventral roots contain only centrifugal, the dorsal roots only
centripetal fibres.
The first experiments of Bell, Magendie,and J. Miiller contain no
positive demonstration of this new and more comprehensive formula
of the law of the spinal roots. Yet (as already discussed in Vol. I.
Chap. X.) the results of experiments by Cl. Bernard, Schiff,
Pniiger on vaso-constrictor nerves, of Dastre, Morat, Gaskell on
vaso-dilatators, of Luchsinger on the secretory sweat nerves, which
are all localised in the ventral roots, agree perfectly with it.
Other investigations, however, showed that the Bell-Magendie
law in its wider formula is not universally valid, but admits of
certain exceptions. According to the work of Strieker and his
pupils, the vaso-dilatators to the posterior extremities are contained
in the 4th and 5th dorsal lumbar roots of the dog, and the corre-
sponding fibres for the anterior limbs run in the dorsal roots of
the brachial plexus. According to Steinach the motor fibres to
the oesophagus, stomach and intestine, including the rectum, are
contained in the dorsal roots of the 3rd- 6th spinal nerves in
the frog. This was disputed by Horton-Smith, who, however,
admitted that he had found motor fibres to the skeletal muscles in
the dorsal roots of the frog. These exceptions to the law agree
with the histological observations of Lenhossek and Ramon y Cajal,
who found that the dorsal roots contain centrifugal elements, i.e.
some cells of the ventral horn send out their axis-cylinders by the
dorsal roots.
Magendie was the first to point out from certain of his experi-
ments that the dorsal roots sometimes contain motor fibres, and
the ventral roots sometimes contain sensory fibres. Owing to
these contradictory facts the value of the law of the functions of
the roots was disputed for some time ; but the difficulty dis-
appeared when Longet and then Bernard demonstrated that the
sensibility of the anterior roots was only an apparent exception to
the Bell-Magendie law. The sensory elements of the anterior
root really corne from the dorsal root, and only pass through
the ventral to supply the sensory innervation of the nieninges.
294 PHYSIOLOGY CHAP.
Demonstration of this phenomenon, which Longet termed recurrent
sensibility, was given in the following experiments :—
(a) If the ventral root be cut, and the two stumps are then
stimulated, sensory effects are obtained from the peripheral end
only, while excitation of the central stump produces no effect.
(&) If a dorsal root be cut, the sensibility of the corresponding
ventral root disappears entirely, whether this be cut or not.
Claude Bernard discovered that in order to obtain a good
demonstration in the dog of the sensibility of the ventral roots, it
is necessary to wait about an hour after exposing the cord. If the
sensibility of the roots is tested immediately after the vertebral
canal has been opened, it is always found that the dorsal roots
alone respond to stimulation. This fact is incontestable, but the
explanation given by Bernard appears to us incorrect. He assumes
that the recurrent sensory fibres of the ventral roots become
insensitive owing to the shock of the operation, and recover their
sensibility with rest. But under normal conditions not only the
ventral roots through which the recurrent fibres pass, but also the
meninges of the cord to which they are distributed, are insensitive
like all serous membranes, and they become sensible to pain only
when inflammation, due to exposure to the air and other influences,
sets in. Hence we may conclude that the fibres that run back
from the dorsal to the ventral roots to be distributed to the
meninges belong to that category of centripetal nerve-fibres that
abound in all visceral organs, and are normally devoid of con-
scious sensibility ; excitation of these only passes the threshold
of consciousness to arouse sensations of pain under conditions of
irritation or inflammatory reaction.
Bernard further demonstrated that division of the mixed nerve
trunk at a certain distance from the union of the two spinal roots
abolishes the sensibility of the ventral root, in the same way as
after division of the dorsal root. This fact proves that the point at
which the recurrent fibres turn ceutripetally is not at the junction
of the roots, but in the nerve plexuses or more peripherally.
Bernard further believed that he had demonstrated that the
sensibility of each ventral root was dependent solely on the corre-
sponding dorsal root, and not on other adjacent sensory roots, but
the subsequent researches of Arloing and Tripier show that recur-
rent fibres may pass from a sensory to other sensory roots.
The existence of recurrent centripetal fibres in the ventral
roots makes it highly probable that centrifugal fibres may emerge
from the ventral roots to run back in the dorsal roots to innervate
the muscle cells that occur in the interior or on the surface of
the cord (vasomotor fibres). Vulpian, on exciting the peripheral
stump of a ventral root, was unable to detect any visible alteration
of circulatory conditions at the surface of the cord, but this negative
result is possibly due to the fact that the vasomotor nerves of the
v SPINAL CORD AND NERVES 295
cord, like those of the hrain, have a long course in the sympathetic
chain and plexuses, after which they re-enter by the spinal roots
of a region higher or lower than that under observation.
An indirect proof of the Bell-Magendie law is afforded by the
Wallerian degenerations that take place in the two spinal roots
after section. As we saw in the last chapter (see p. 232), when
a mixed nerve is divided the peripheral part that is severed
from the centre degenerates, while the proximal part connected
with the centre remains unchanged for a long time, and may grow
and regenerate the cut nerve. Waller found that after section of
the dorsal root (between the spinal ganglion and the cord) the
central, but not the peripheral part degenerates ; after section of
the ventral root, on the contrary, the peripheral, but not the
central part degenerates. So that the afferent fibres of the
posterior root have their trophic centre in the cells of the spinal
ganglion, and the efferent fibres of the ventral root have their
trophic centre in the cells of the grey matter of the cord. This
observation agrees with, and therefore confirms, our physiological
knowledge of the dissimilar character of the fibres which constitute
the two roots.
Wallerian degeneration also confirms the phenomenon of
recurrent sensibility. Schiff (1850) was the first to see that
after cutting the ventral root certain fibres in the central stump
degenerate, while a corresponding number in the peripheral stump
remain intact. Since these are recurrent fibres, it is clear that
those which are separated from their trophic centres in the central
stump degenerate, while those which are left in connection with
their centre in the peripheral stump remain intact.
Wallerian degeneration also confirms the fact that a certain
number of centrifugal (vaso-dilatator) fibres emerge with the dorsal
roots. If this is a genuine exception to the Bell-Magendie law,
section of the dorsal roots should give rise to a form of degeneration
which is not in strict correspondence with Waller's law, i.e. there
must be some intact fibres in the central stump and some
degenerated fibres in the peripheral sturnp. Different authors,
however, obtained different results by this method. Vejas, Max
Joseph, Gad, Morat and Bonne obtained positive results as above ;
Sherrington, Singer and Miinzer, Gabri, on the other hand, found
the central stump completely degenerated, and the peripheral stump
intact, precisely according to Waller's law. In order to settle the
controversy, Tarulli and Panichi (1902) resumed the study of the
degenerations consequent on section of the dorsal roots, and made
a number of experiments on different parts (cervical, dorsal, and
lumbar) of the dog's cord. The degenerations were followed out
by the method of Marchi or of Weigert-Pal, both on cross-sections
of the root-stumps and on teased bundles of nerves, in order to
study the fibres lengthways. The result was constant ; in the
296
PHYSIOLOGY
CHAP.
peripheral stumps of the cervical and thoracic dorsal roots there
were a very few degenerated fibres, and in the central stump a
corresponding number of healthy fibres. But in the lumbar dorsal
roots more fibres were degenerated in the peripheral stump and
more were intact in the central stump (Fig. 179).
Hence the degeneration method confirms this exception to the
Bell-Magendie law, as a few dorsal root- fibres, especially in the
lower lumbar segments, have a centrifugal course, and take origin
either from Kainon y Cajal's dorsal root cells or from the cells in
the ventral horn, while all the rest have their trophic centre in
the spinal ganglion.
IV. Numerous physiological and clinical facts show that there
Fio. 179.— A, transMTsi' section of central end of 7th dorsal lumbar root of dog, showing degenera-
tion of most of the fibres (black discs) with very few healthy fibres. 13, transverse section of
piTipln-ral i-iid of same root, showing contrary appearance. (From preparations made by
Tarulli and Panichi with Marchi's method.)
is a close relation between sensation and movement, and that the
functions of the two spinal roots, while distinct, are not inde-
pendent of one another.
The influence that the dorsal roots exercise upon the spinal
efferent neurones can be shown in various ways by observing the
reaction of the skeletal muscles. Brondgeest (1860) was the first
who noted relaxation or atony of the flexor muscles of the frog's
thigh after cutting the dorsal roots of the lumbar plexus. Harless,
on stimulating the frog's sciatic with a weak induction current,
before and after section of the same roots, found the constant
effect of division to be diminished excitability in the nerve.
Cyon (1865) first experimented directly on the spinal roots,
and demonstrated that the integrity of the dorsal roots is indis-
pensable to the normal excitability of the corresponding ventral
roots. Section of the former produces a depression of excitability
in the latter.
v SPINAL CORD AND NERVES 297
Von Bezold and Uspensky contested Cyon's results, since they
were unable to verify any constant influence of the dorsal upon
the ventral roots. According to these authors, the fact recorded
by Cyon is rarely met with ; in the majority of cases excitability
remains unaltered ; sometimes, indeed, it is temporarily increased.
This last feature was constantly observed by Marcacci in
Dastre's laboratory. He divided all the spinal roots in the frog
with the exception of one pair. On then cutting the dorsal root
of this pair he found that an induced current that was previously
inadequate to evoke a response now threw the muscles innervated
by the remaining ventral root into contraction.
Bemiondo and Oddi (1890), under our direction, resumed the
experimental study of this subject on the dog. They abolished
the influence of the dorsal root, not only by section, but also by
the local application of cocaine, which produces temporary paralysis
without excitation. Under these conditions they constantly found
a marked depression of excitability in the corresponding ventral
root, which no longer reacted to the minimal stimuli that had
previously been effective.
In a new series of experiments (1896) Polimanti returned to
this subject, and sought to determine the influence exercised on a
ventral root, both by the dorsal roots of the same pair and by
those of other pairs (above or below) on the same or the opposite
side. Generally speaking, he confirmed and extended the results
of Belmondo and Oddi, and found that on dividing the dorsal
roots there is constantly a marked depression of excitability in
the corresponding ventral root. The same result was often
obtained on testing the reciprocal influence of two roots of
different spinal pairs, on the same or the opposite side. But there
was a marked difference between the results of Belmondo and
Oddi and those of Polimanti as regards the effects of mechanical
or electrical stimulation of the divided dorsal roots. The first
authors found that on stimulation of the dorsal roots the excita-
bility of the ventral roots was almost invariably increased above
the normal ; Polimanti in most cases obtained the opposite result,
i.e. depression of excitability, which he held to be a reflex inhibition,
probably caused by the excessive strength of the stimulus. But
he did not deny that under normal conditions a slow and quiet
wave of excitation passes, as assumed by Cyon, from the dorsal to
the ventral root, by which its excitability is maintained and on
which the tone of the skeletal muscles depends.
In proof of the reinforcing action of the dorsal upon the
ventral roots, it is only necessary to study the motor effects of
dividing the former. If one dorsal root alone is divided no very
obvious effects ensue, because the influence of adjacent roots
readily compensates the functional deficiency. But if several
sensory roots are cut, e.g. all those which supply the sensory
298 PHYSIOLOGY CHAP.
innervation for a posterior limb, the movements of this limb, while
not abolished, will be altered in a characteristic manner.
Panizza (1835), who first performed this experiment, noted
that the movements of the apaesthetic limb were uncertain and
showed the characteristics termed by us dysmetria, i.e. failure to
measure. In movements of flexion, for instance, the limb was
carried too far up and out. Stilling (1842) confirmed Panizza's
observations and ascribed to the dorsal roots the maintenance of
muscular tone by transmitting to the centres a knowledge of the
state and position of the muscles. Cl. Bernard (1858) pointed out
that the frog made little use of its leg muscles when the influence
of the sensory roots was cut out. A very accurate description of
the movements of the apaesthetic leg of the frog has recently been
given by the younger Hering. Among various phenomena he
noted the following as characteristic : when the animal jumps it
takes up its normal position first with the intact and then with
the apaesthetic limb, and in bringing the latter back to the
ordinary position raises it unduly (Hebphdnomen). When the
posterior roots are divided on both sides, the frog makes lower and
less extensive springs.
The effects of dividing the dorsal roots in the dog were
exhaustively studied by Baldi (1885), who kept the animals alive
for a long time. On cutting the afferent roots of a hind-limb the
leg in which sensibility is paralysed is not used in walking during
the first days ; it seems incapable of supporting the weight of the
body, is kept semi-flexed at the thigh- and knee-joints, and is rarely
completely extended. Later the animal begins to use it in walking,
but in an abnormal manner ; it is lifted too high and thrown
either too far forward or too far back. After cutting the afferent
roots of the last three cervical nerves and the first thoracic on one
side, the animal limps, holding the insensitive leg up off the
ground. After a few days the leg may be used in walking, but
the foot gives way and the animal stumbles and falls. Sub-
sequently the gait improves, but then trophic disturbances of the
limb in which sensation is lost set in. Bilateral section of the
afferent roots of the lumbo-sacral plexus makes the animal
incapable of using the posterior half of its body, which is dragged
passively along by the anterior part as if paralysed. On lifting
the animal up, the hind-limbs perform alternate flexor and extensor
movements. Eventually the hind-limbs succeed in supporting the
weight of the trunk up to a certain point, but the knees often
knock together and give way.
The effects of dividing the dorsal roots of the monkey, accord-
ing to Mott and Sherrington (1895), are even more striking.
When all the afferent roots of a limb are cut it is used neither in
walking nor climbing, and only comes into play with very energetic
movements of the corresponding normal limb. When the monkey
v SPINAL CORD AND NERVES 299
wishes to reach an object with a limb in which only the sensibility
of the skin of the hand is preserved, its movement is irregular and
zig-zag, and it often grasps objects lying near the thing to which
the movement was directed.
According to H. Munk, who tested these results o'f Sherrington
and Mott by experiments on the macaque monkey, on cutting the
dorsal roots of one arm the immobility of this limb is not so
complete as was asserted by the above authors. It is only the
movements normally observed on stimulating the afferent nerves
of the limb that disappear ; the other movements seem to be
difficult and temporarily or permanently impaired in proportion
as the excitability of the central organs from which they are
evoked is diminished, owing to the suppression of the excitations
that normally reach them by the sensory paths.
Bickel (1897) observed that the effects of severing the afferent
paths in the dog are greatly aggravated by lesions of the labyrinth.
A similar effect is also obtained by cutting out the retinal
sensations.
H. E. Bering, Sherrington, and Bickel all agree that mechanisms
exist, more particularly in the cerebral hemispheres, which are
capable of compensating the loss of afferent control in animals
with paralysed sensibility. Bickel and Jacob (1900) saw that
the disturbance of gait in dogs that have lost sensibility in the
hind-limbs gradually diminishes in time till it disappears. " If
after this compensation has been established the senso - motor
zones of the cerebral cortex in relation with the hind-limbs are
destroyed, the ataxic disturbances reappear, and are again compen-
sated slowly and feebly — never to the former extent." Merzbacher
(1902) found the same on the frog.
The experiments of Trendelenburg (1906) on pigeons, in which
the dorsal roots of various regions of the cord had been cut, agree
fundament illy with the above. Bilateral section of the dorsal
roots which innervate the wings crippled the animals permanently
for flight, while bilateral section of the dorsal roots for the legs
caused permanent incapacity for standing. After unilateral section
of the same roots a great difference is seen in the behaviour of the
wings and the feet, as this operation does not interfere with normal
flight, signs of dysmetria being perceptible only in certain reflexes
(abnormal lifting of the wing), but unilateral section of the lumbo-
sacral roots produces marked ataxia, which at first hinders both
standing and walking. The animal only learns to use its limbs
again by degrees, the disturbances of innervation, particularly in
locomotion, being plainly shown by an abnormal raising of the
leg, analogous to the Hebphanomen which Hering described for
the frog. The reason for this dissimilar behaviour of the wing
and the leg lies in the fact that the wings are as a rule innervated
simultaneously, so that sensory impulses passing to the centres on
300 PHYSIOLOGY CHAP.
one side only can regulate the movements of both wings ; while
the legs which come into play alternately have each an independent
regulating mechanism. The compensatory phenomena observed
after operating on oue leg are undoubtedly due to sensations
coining from the sound leg. If this also is operated on the power
of standing is permanently lost. The labyrinth takes an important
part in these phenomena of compensation : if it is destroyed on
both sides, compensation disappears and never fully returns.
The cerebrum, on the other hand, has no influence in compensating
these motor disturbances.
Trendelenburg's results agree with those obtained by other
experimenters on other animals. His observations differ in one-
important respect from those previously recorded, viz. while
bilateral section of the dorsal roots of the legs causes muscular
atony of those limbs, so that they hang flaccid, bilateral section of
the dorsal roots that innervate the wings does not induce loss of
their muscular tone, so that when at rest they keep approximately
the normal position of flexion — folded and raised on to the back—
and neither hang flaccid nor trail the feathers on the ground.
The tone of the muscles to which this posture of the wings is due
does not disappear even if the anterior brain is removed, or the
labyrinth destroyed. Trendelenburg concluded that the tone of
the wings is not reflex in origin. In some control experiments
Baglioni (1907), however, noted that the insensitive wing does not
behave at all like the normal wing. Even if the apaesthetic wing
does not hang or trail on the ground when the pigeon stands erect
or walks, like the wing paralysed by section of all its motor and
sensory nerves, it certainly does not oppose the same degree of
resistance to passive movements as a normal wing, nor is it raised
and lowered immediately like the normal wing. The insensitive
wing is, therefore, deficient in muscular tone. In order to explain
why the apaesthetic wing does not betray its atonic condition in
the erect posture or in walking, Baglioni suggests that the sensa-
tions coming from the leg renexly excite tonic contraction of the
wing muscles, so that these are raised on to the back and do not
trail along the ground.
V. The mode in which the fibres of the spinal roots tire dis-
tributed after passing through the nerve plexuses to the skin and
subcutaneous tissues, and particularly to the muscles, is of more
than merely anatomical interest. It is intimately associated with
the simplest reflex functions of which the individual segments of
the cord are capable ; it has further a practical interest, as from
our knowledge of it it is possible from motor and sensory functional
disturbances to deduce conclusions as to the localisation of circum-
scribed lesions of the cord or the spinal roots.
Anatomy tells us little of the special peripheral relations of the
sensory and motor fibres that emerge from each pair of roots. In
v SPINAL COED AND NERVES 301
fact the spinal nerves intermix so freely along their course in the
plexuses (cervico-dorsal, lumbo-sacral plexuses) that it is necessary
in order to ascertain the peripheral distribution of each sensory
and motor root to resort to the emhryological method, or the
physiological methods of section and excitation, or the pathological
method of degeneration combined with clinical observations.
Apart from observations by the older anatomists (Reil, Monroe,
Scarpa, Sommering), Schroder van cler Kolk (1847) was the first
to occupy himself with the peripheral distribution of the spinal
roots. He assumed that the branches of the mixed nerves in
general are distributed so that the sensory ramifications terminate
in the region of the skin lying immediately over the muscles
innervated by the motor fibres of the same nerve.
Starting from this concept, Eckhard (1849) studied on the frog
the relations between the peripheral terminations of the dorsal and
ventral roots that innervate the hind-limbs. He found Schroder's
law to be true, but not entirely accurate, since the sensory fibres
do not exactly supply the cutaneous areas over the muscles
innervated by the corresponding motor fibres. In order to discover
the distribution of the sensory roots in the skin, he divided all
the dorsal roots save one, and then ascertained which area of
the skin still preserved its sensibility. In this way he dis-
covered that each root provides sensibility to a definite and
continuous region of the skin, and that these regions more or less
overlap one another. To determine the distribution of the motor
roots, he experimented with electrical excitation of one alone, after
section of the rest, and found that it only threw certain of the
muscles of the limb into contraction. This corrected an observa-
tion made by Kronenberg (1836) under Johannes Miiller's
direction. He attributed to the plexus a protective function
against fatigue, and assumed that the stimulation of a single root
forming part of the plexus was able to throw all the muscles of
the limb into contraction.
Eckhard's results were controlled by Koschewnikoff (1868), C.
Mayer (1869), and more recently by Sherrington (1893), without
substantial modification. Peyer (1854) and Krause (1865)
obtained similar results on the rabbit.
But in all these researches the leading motive that was to
combine the scattered facts into one system was wanting, viz. the
extension of the idea of segmentation — metamerism — to the peri-
pheral distribution of the sensory and motor roots. Tiirck (1856)
first detected a segmental arrangement in the cutaneous areas
supplied by the sensory roots. He divided the dorsal roots one by
one in the dog, and determined the peripheral distribution of each
by observing the zone of insensibility to touch and pain that
ensued in the skin. He thus discovered the cutaneous root areas
for the whole of the dog's body, and showed that a part of each
302 PHYSIOLOGY CHAP.
zone acquired its sensibility almost exclusively from the corre-
sponding dorsal root, while the remainder owed its sensibility both
to its proper root and to those adjacent to it. The cutaneous
root-zones or segments of the neck and trunk, according to Tiirck,
are arranged in series and girdle the body like rings, which start
from the spinous processes of the vertebrae and reach the ventral
median line in a direction almost vertical to the axis of the body.
The root areas for the skin of the limbs appeared to Tiirck to
be irregular in form, which in his day was found difficult to
interpret.
Although commended by Ludwig in the second edition of his
Text-book, Tiirck's memoir passed almost unnoticed, the morpho-
logical theory of metamerism not being yet sufficiently developed.
The modern view of the segmental distribution of the ventral
roots was led up to by the work of Ferrier and Yeo (1881) on the
motor roots of the brachial plexus in the monkey ; the almost
contemporaneous work of Paul Bert and Marcacci on the roots of
the him bo-sacral plexus in the dog ; that of Forgue and Lauuegrace
(1884) on the roots of the brachial and lumbo-sacral plexuses of
the dog and monkey ; lastly, that of Polimanti (1894) on the
brachial and lumbo-sacral plexuses of the dog, rabbit, and cat.
The separate excitation of each of the ventral roots that combine
to form these plexuses invariably resulted in a synergic movement,
co-ordinated to a definite purpose, so that there is in the individual
ventral roots a functional systematisation of movements.
The memoir of Forgue and Lanuegrace is the most important
from the segmental point of view. These authors recognised that
each root contributes to the innervation of an always identical
series of muscles, so that in animals of the same species the
distribution is approximately constant. When a functional varia-
tion occurs it is small, and the innervation acquired or lost by
any root is borrowed from, or passed on to, the root immediately
adjacent to it, and not to a more distant root. In opposition to
the other authors cited, Forgue and Lannegrace assumed that
while the excitation of an entire root does produce a combined
movement, this combination is accidental and not functional, so
that normally, in carrying out any movement, the will must excite
the synergic fibres of several roots, and not of one root alone.
They showed no reason why this should be the case, but it
harmonises with the histological fact of the multiplicity of
collateral rami from the fibres of the pyramidal bundle, which
penetrate the grey matter at different levels and enter into relation
with the cells of the ventral horn in different segments.
The theory of the metameric distribution of the sensory and
motor roots, now generally admitted, rests to a large extent upon
the exhaustive experiments of Sherrington (1893) on the sensory
roots, of Kisien Russell on the motor roots of the monkey, and on
v SPINAL CORD AND NERVES 303
the morphological work of Bolk on both motor and sensory roots
in man.
If we summarise the complicated results of these three authors
under a few heads, and for the moment pass over certain divergences
which will be discussed below, it may be said that :—
(«) There is a true segmentation of the body-surface (Sherring-
ton's segmental skin-field) as well as a true segmentation of the
muscles, which both correspond with the metamerism of the spinal
roots. There are certain exceptions to the strict parallelism
between the segmental innervation of the skin and of the
muscles assumed by Schroder van der Kolk, particularly in the
extremities, where during phylogenetic and ontogenetic evolution
the muscle segments often become more or less displaced in
relation to the segmental skin-fields.
(6) While the skin segments (Bolk's dermatomes) form con-
tinuous fields, the muscle segments (Bolk's myotomes) are com-
pounded of portions of several muscles. Their metameric
arrangement is less striking than in the dermatomes, but can
easily be demonstrated.
(c) The metameric arrangement of the dermatomes and
myotomes in the neck and trunk is ring-shaped ; at the ex-
tremities it seems to be more complicated, but is intelligible from
the ernbryological development of these organs.
(d~) Each derniatorne is partially covered by the adjacent, which
immediately precedes and follows it in the serial arrangement
(cranio-caudal direction). This fact, already known to Eckhard
and Tiirck, has been termed by Sherrington overlapping. Whether
a similar overlapping occurs among the myotomes is at present
unknown.
(0) The sensory inuervation of the muscles follows their
metamerism, not that of the skin. The metamerism of the pilo-
rnotor nerves is almost parallel with that of the skin. The
vasomotor innervation of the skin also corresponds approximately
with the dermatomes.
These facts from the work of Sherrington, Risien Russell and
Bolk give an almost complete schema of the metamerism of the
skin and muscles (Fig. 180). There are, of course, divergences
that seem a priori inevitable in view of the difference of species
(man and monkey) and of method (physiological and morpho-
logical) under which the data were collected.
Kocher's attempt (1896) to determine the segmental skin-
fields for man solely by deductions from clinical data was a
failure. A series of publications by the Dutch neurologist
Winkler and his pupils, Beyermann, Coenen, Langelaan, Van
Rynberk, show that the clinical data accord well with the diagrams
of Sherrington and of Bolk.
Wichmann has recently collected from modern clinical
304
PHYSIOLOGY
CHAP.
literature (Thorburn, Kocher, Gowers, Starr, Eclinger, Leyden,
Goldscheider, Striimpell, Jacob, etc.) a series of observations on
the segmental innervation of muscle whicb agree witb the fore-
going experimental and morphological facts.
The main defect of Kocher's diagram, and also of that suggested
by the American neurologist Allen Starr, is in the nietameric
FIG. 180. — Metameric distribution or transverse segmentation of cutaneous areas <>f sensibility of
human body, drawn with the limbs in the position of their embryonic growth. (Diagram con-
structed by Luciani from Bolk's data.) The series of derma tomes which successively correspond
to the cervical, lumbar, and sacral roots is indicated by different degrees of shading.
division of the limbs. Without giving sufficient attention to the
special character of the embryological development of the limbs,
they — Starr more particularly — represented the dermatomes as
running from the vertebral column to the limbs in uninterrupted
zones, narrow in the middle and somewhat expanded at the ends.
Bolk's schema, on the contrary, corresponds perfectly with our.
knowledge of the embryological development of the limbs. The
arrangement of the der-matomes in the upper limb (Fig. 180) is in
the following order in the cranio-caudal direction : shoulder, outer
SPINAL CORD AND NERVES
305
side of upper arm, radial side of forearm, hand, ulnar side nf
forearm, inner side (lower in figure) of upper arm, axilla. The
segments 4, 5, 6, 1C are separated from the segment's 8C, ID by
a line corresponding to the axis of the limb. There is a similar
arrangement in the lower limb. If we consider the embryo-
logical development of the limb as shown in the diagram (Fig.
181) it is easy to see how this arrangement originated. At a
the limb-buds, formed chiefly by a lengthening of the nietameres
- 1
4
$
6
7
8
/
z
/
I
a A]
i
_J
/
FIG. 181. — Diagram of embryonic development of tipper limbs from the metameres UC, !>, 6, 7, 8,
ID. (Bolk.) a, 1), (.-, d, e, /show the successive phases of the growth cone of the limU^wing
to the lengthening of the metameres destined for the upper limb, and its displacement from
the middle line of the body.
7 and 80, begin to appear ; at b and c these metameres, separated
by the axis of the limb, begin to extrude from the median line of
the body ; at d and c the nietameres 5 and QC and ID are also
displaced from the median line and form part of the cone of
growth ; finally at / the arrangement and distribution of the
metameres of the limb is the same as those of the adult individual.
( Granting this arrangement of the skin and muscle segments,
we next have to consider their constitution and functions separately.
With the exception of a few small muscles of the vertebral
column, which receive their motor fibres from one ventral root
alone, all the other muscles of the human body are supplied by
VOL. Ill
x
306 PHYSIOLOGY CHAP.
fibres from more than one root, i.e. they are polymeric,, belonging
to many myotomes. On the other hand, each myotome contains
portions of several muscles. The actual muscles, derived from the
fusion of several monomcric units, may be classed in three groups :
(«) Muscles that remain monomeric, with a single function.
Among these are the small vertebral muscles above referred to.
O
(5) Polymeric muscles with a simple function, as the rectus
abdomiuus, which is innervated by the 5th-12th thoracic roots;
the tendinous bands seem an evidence of the fusion of the eight
segments of which the muscle is composed.
(c) Polymeric muscles with complex functions. Most of the
skeletal muscles belong to this category.
When a muscle thus receives fibres from two ventral roots,
does the stimulation of one of these roots produce total contraction
of the muscle ? Sherrington replies in the affirmative ; he even
maintains that it is not necessary to stimulate the whole of the
root ; it suffices to excite any one of the filaments or rootlets
which compose the root, as it passes through the dural sac, in
order to throw the entire muscle into contraction. Eisieu Russell
contradicts this emphatically, and affirms that stimulation of a
single root of a polymeric muscle only throws a portion of it into
contraction. This is obviously the case for the sartorius muscle.
Whatever the final solution of this controversy, it is certain that
although a myotome may be a complex of muscle fibres which
have only a single function, it is far more frequently found that
the muscular complex of the myotome contains elements with
antagonistic functions. In this case it is evident that the same
ventral root must contain separate fibres for both functions.
Thus Martin and Hartwell observed in the dog a rhythmically
alternating functional activity of the motor root which innervated
the antagonistic internal and external intercostal muscles.
The physiological unit of cutaneous metamerism — the drrwa-
tome — has recently been the subject of a careful experimental
study by Winkler and Van Rynberk. They found that the
dermatome consists of two areas, one central, the other marginal.
The former is capable of maintaining sensibility even when all
overlapping is abolished by section of the neighbouring posterior
roots ; the latter, on the contrary, is not capable of subserving
sensibility without the co-operation of the overlapping dermatomes
(Fig. 182, A).
The sensibility of the central and marginal areas of the
dermatome is not uniform, but varies in degree at different points.
Three spots can be distinguished in the dermatome at which
innervation and therefore sensibility are maximal. One of these
lies near the dorsal median line, the second near the lateral line,
the third near the ventral median line, as shown in the diagram.
From these points, at which it is most acute, sensibility diminishes
V
SriNAL CORD AND NERVES
307
gradually to the surrounding and the more peripheral parts of the
dermatome. These areas correspond with the points at which the
cutaneous nerves enter the skin.
In another series of experiments Winkler and Van Rynberk
attempted to decide the question whether the four or five rootlets,
which make up each dorsal root, have a localised or a diffused
c F
Fio. 182.— Diagram of dermatomes of the trunk of the body. (Winkler and Van Rynberk.) All
six diagrams show a central area shaded dark and a marginal area shaded light ; d, median dorsal
linn; J, lateral line ; v, ventral median line ; ^t, centre of maximal dorsal innervation ; +, centre
of maximal lateral innervation. A shows the complete form of the central area, which is isolated
only in the most successful operations ; in B, C, D, E there is an increasing reduction of the
st-nsiiry central area owing to greater traumatic lesions or to partial section of the roots ; at F
tin; whole dermatome is insensitive save the first area marked * *** which corresponds to
the point of maximal dorsal iniiPi vatiun known as the ultima m muricii* of the dermatome.
distribution in the dermatome. Their results showed that partial
transaction of the root has the same effect as a complete section,
except that the central area of complete insensibility is reduced
as indicated in Fig. 182. The diagrams B, C, D, E show the
various degrees of restriction of sensory area shown in such cases.
During the period of shock after the operation a few points only
may be found near the median dorsal line (diagram F), in which
sensibility persists in the midst of an analgesic area. This point,
308 PHYSIOLOGY CHAP.
which coincides with the maximum of dorsal innervation (diagram
A at point #), was termed by Winkler and Van Rynberk the
" ulti'iiiU'in moricns " of the dermatome.
These observations, as a whole, bring out the important
physiological fact that the function and distribution of the root
filaments is diffuse, and not localised, in the segmental skin-field.
The same authors also endeavoured to estimate the precise
extent to which overlapping of the dermatonies takes place.
By a series of ingenious measurements and calculations
Winkler and Van Rynberk ascertained that the overlapping of the
central areas amounts to one-third near the dorsal median line ;
to two-ninths near the lateral line ; while in the ventral median
line they do not come into contact. If the marginal zone is also
taken into consideration, the total overlapping of the derrnatomes
appears at no point to be less than half, so that every point on
the skin must be simultaneously related to two dermatomes, i.e.
it is innervated from two dorsal roots. This observation holds
for the trunk : in the region of the limbs the dermatonies are
more compressed, and the overlapping is therefore greater.
These central areas of the dermatomes are important, more
particularly when brought into relation with the clinical facts
observed by Head (1893). He describes areas of cutaneous
hyperalgesia met with in many visceral diseases, particularly
those of the intestines. He observed great constancy in their
localisation and extension, and that in these particulars they
correspond with the eruptive zones of Herpes zoster. Since it
is known that this cutaneous eruption is only the external
symptom of an acute infectious inflammation of one or more
spinal ganglia, it was natural to assume that the herpetic eruption
would follow the cutaneous metamerism, the more so as Sher-
rington had already noted that the sympathetic innervation of
the skin coincides approximately with it. Head considers the
cutaneous hyperalgia, which is symptomatic of internal disease, to
be the peripheral expression of irritation in a spinal segment.
The only serious objection to this hypothesis is that none of
Head's zones overlap like the dermatonies. It is probable that
the zones of Head, like the herpetic eruption, occur only within
the central areas of Winkler and Van Rynberk, where overlapping,
as we have seen, takes place to a much smaller extent than for
the whole dermatome. In this way it is possible to refer an
important series of obscure clinical facts to the system of cutaneous
segmentation.
Another phenomenon pointed out by Langelaan (1900) must
be mentioned in connection with cutaneous metamerism. He
discovered that a whole system of lines and areas exists in the
skin of normal persons, which may, in comparison with the rest
of the skin, be termed hyperalgesic. For example, 021 pricking
V
SPINAL COED AND NEEYKS
309
the arm in various places lightly with a pin a subject of ordinary
intelligence is able to indicate accurately that in certain lines
and areas the painful sensation is felt far more acutely than in
adjacent regions. This cannot depend on differences of pressure
in the pricking, for if the experiment be repeated at different
p.
Ki',. is". — Hyperalgesic liands and areas in skin of upper limb
(A), lower limb (B), and thorax (C) of a normal individual.
(Langelaan.)
times and on various subjects, the hyper-
algesic points are found fixed and well
defined. On tracing the hyperalgesic
points with a dermographic pencil upon
the skin of his subjects, Langelaan found
that they combined into definite fields
and lines, which coincide with the limit-
ing lines of Bolk's dermatomes (Fig.
183, A, B, C).
The hyperalgesic lines seem to corre-
spond with those points at which the
dermatomes overlap ; on the back of the
hand and the palm where some of the
dermatomes (6, 7, 86', 1Z>) fuse they form a definite area, not a
line, as seen at A in the above figure.
It is worth noting that under certain pathological conditions,
e.g. in Tabes dorsalis, these hyperalgesic lines and fields become
pronounced and more easy to demonstrate than under normal
conditions.
310 PHYSIOLOGY CHAP.
In order to obtain a more constant and readily measurable
stimulus, Coenen has tested Langelaan's discovery by means of
an Erb's electrode with three seconds application of weak induced
currents. In an area limited to the ulnar surface of the forearm
he showed that the skin is more sensitive near the axis of the
limb, and that the subject felt pain here with a current that was
unperceived in the neighbouring regions.
VI. As was stated above, the real and perfect metamerism
of the spinal roots is only seen in the segmeutal arrangement of
the cell columns of the ventral horn of grey matter. This fact
fully bears out the physiological view that the spinal cord
represents a series of central organs (myelomeres), which are
intimately connected, and are more or less unitary in their
functions.
The predominating function of the niyelomeres is " reflex
activity." This term, borrowed from the physicist — who speaks
of the reflection of light and heat rays — corresponds ill with the
physiological phenomena which it is intended to connote. In
the widest sense any immediate reaction of a living and excitable
element to an external stimulus may be called a reflex act. In
a narrower sense, however, as applied to the nervous system,
the reflex act is the involuntary transformation of a centripetal
into a centrifugal nerve impulse, by means of a central organ,
represented by a group of ganglion cells. We say "involuntary
transformation " to distinguish the reflex act from the voluntary
act, which may also follow on, and be evoked by, an afferent
impulse.
Typical examples of common reflex actions are : sneezing on
stimulation of the nerves of the nasal mncosa, coughing from
stimulation of the glottis, swallowing from contact of fluids or
solids with the isthmus of the fauces, contraction of the pupil
to light, movements of the arm or leg on tickling the armpit or
sole of the foot, etc. Every one knows that these movements are
involuntary — for although the will can check them to a certain
extent, it cannot inhibit them —and that they may be conscious
or unconscious, since they may occur in the waking or the
sleeping state.
But in experiments upon animals it is difficult to distinguish
" reflex " acts from the " voluntary " acts which result from
conscious sensations. In order to establish the purely reflex
nature of spinal acts the influence of the will is cut out in
animals, either by narcosis, or by decapitation or removal of the
cerebrum. None of these methods, however, seem to us adequate.
The first method is founded on the fact that narcotics (opium,
chloroform, ether) suspend the psychical activities first, without
loss of excitability or conductivity in the lower nervous elements.
But according to the best auto-observations in chloroform narcosis,
v SPINAL COED AND N KJiVES 311
the abolition of sensation and volition takes place gradually, and
is not complete till the narcosis has been carried so far as to
inhibit the movements that we consider " reflex " because they
are excited by external stimuli.
The second method is founded on the assumption that the
psychical functions are localised exclusively in the brain. Uut
this, as we shall see, is far from certain. It is doubtful whether
the spinal cord severed from the cerebrum may not also be capable
of function as an organ of sensation, albeit an imperfect one, and
whether the excitation of its afferent nerves may not avail to
excite traces of consciousness and motor impulses, since there is a
choice of efferent paths by which the excitation can be transmitted
to the peripheral motor organs.
Hence it is not possible in studying the functions of the spinal
cord to make a sharp distinction between purely reflex and
voluntary acts, since there is no objective sign by which a clean
line of separation can be drawn between them. The purposive, or,
as Goltz calls it, the responsive, character, or property of carrying
out movements directed to a given end, is common to both reflexes
and voluntary actions, as appears from the experiments made on
cold- as well as on warm-blooded animals.
We are therefore constrained to make an objective study of
the characteristics and manifestations of the reflex acts which the
spinal cord is able to carry out independently of the brain.
Whytt (1750) was the first who demonstrated that the agency
of a central organ is necessary for the transmission of excitations
from afferent to efferent nerves. As soon as the grey matter of
the cord is destroyed every reflex movement ceases. The same
author showed that reflex action does not depend on the integrity
of the cord as a whole, but that an isolated segment suffices for the
reaction. If in the decapitated frog the cord is divided at the
level of the fifth spinal nerves, reflexes in both the fore- and the
hind-limbs are obtained on exciting the skin. The reflex centre
for the former is located in the ventral enlargement, for the
latter in the dorsal enlargement of the cord. A striking
example of a vigorous and sustained reflex in the frog, first
noticed by Spallauzani, is the sexual clasp, which persists after
dividing the cord above and below the two large nerves of the
brachial region (second and third cervical pairs). The lizard's tail,
like that of the eel, can be divided into a number of pieces, each
of which preserves refiex activity for some time. The lumbo-
sacral region of the cord can be longitudinally split up into two
halves, each of which is capable of reflex movements so long as
the grey matter is left intact. The functional capacity of isolated
parts of the spinal cord is the physiological evidence of its
metamerism. In the higher warm-blooded animals the function
of the segments is obscured by the phenomena of shock, which
312 PHYSIOLOGY CHAP.
inhibits the activities, not merely of the parts directly injured,
but also of the more remote parts which have not received direct
injury. Even when contusion or traction is as far as possible
avoided, a transection can suspend all activity in the cord for a
certain time.
Marshall Hall first gave the name of " shock " to this temporary
depression or total inhibition of the nervous functions after
mechanical injury to any part of the system. Goltz held the
phenomena of shock to be due exclusively to inhibition, but this
is doubtful. If the mechanical lesion is regarded as a powerful
stimulus, then shock may be conceived as exhaustion of excitability
in the elements involved. As by transection of the cord the
lower part is suddenly severed from the higher centres, we may
hold with Foster that the phenomena of shock which it exhibits
may arise partly from the withdrawal of the stream of influences
which reached it while still connected with the rest of the system,
and that these phenomena subsequently disappear as the cord
becomes adapted to the new conditions and learns to function
independently.
Amongst " laboratory animals," monkeys exhibit spinal shock
at its maximum after transection of the cord (Sherrington). The
fact should be noted that the shock appears to take effect in the
aboral direction only. After high cervical transection, the effects
of shock are more severe in the fore-limbs than in the hind ; for
an hour or so it may be difficult to elicit a reflex by any kind and
any strength of stimulus.
In the dog this functional depression usually wears off in about
five weeks after a brachial transectiou. In man transection of
the cord profoundly disturbs the functions of the skeletal muscles,
and to a certain extent those of the viscera, as in monkeys.
G-oltz assumed that the phenomena of shock may persist for
months in the isolated part of the cord. Sherrington, on the
other hand, inclines to think that the true shock phenomena
pass off much more rapidly, and are succeeded by permanent
functional alterations, which in many ways resemble a recrudescence
of shock. These are probably caused by " isolation-dystrophy "
due to the withdrawal from the spinal nerve-cells of the influences
they are accustomed to receive from higher parts of the nervous
system. In any case, it is certain that the phenomena of functional
depression due to transection of the cord are more pronounced and
permanent in man and in the ape than in the dog and rabbit,
while they are quite transitory in the frog and other cold-blooded
vertebrates. The increasing gravity of shock in ascending the
vertebrate scale is probably due to the increasing influence of the
great projection system of the brain on the motor organ in the
higher animals. The relative insignificance of shock in the
visceral system, and slight differences in the animal scale in this
v SPINAL CORD AND NERVES 313
respect, indicate " the extent to which the reactions of the visceral
musculature and some of the reactions of the skeletal musculature
accessory thereto are normally unconnected with higher conscient
nervous organs.
" i
Sherrington's observations on monkeys, after cervical tran-
section, are very important. The motor root-cells that do not
respond to stimulation of the skin react perfectly to excitation by
the pyramidal paths at the cut end of the cord ; weak stimulation
of the central ends of the afferent root readily evokes reflex move-
ments, though far stronger stimuli fail absolutely when applied to
the skin and afferent nerve trunks.
VII. When a stimulus applied to any sensory area of the body
evokes a reaction of the muscles belonging to the same or to
adjoining segments of the cord, the reaction is termed a short
spinal reflex; when, on the contrary, the stimulus evokes a
reaction on the musculature of a more or less distant uietauiere,
the spinal reflex is termed long. Short spinal reflexes are, as a
rule, more easily and readily elicited because they have less
resistance to overcome.
Sherrington makes the following statements as to the intra-
spinal irradiation in short spinal reflexes :—
1. The degree of reflex spinal intimacy between afferent and
efferent spinal roots, i.e. the facility with which the reflex is dis-
charged, varies directly as their segrneutal proximity. The
excitation of a central end of a severed thoracic root evokes with
special ease contraction of muscles, or parts of muscles, innervated
by the corresponding motor roots, and next easily muscles inner-
vated by the next adjacent motor roots. The spread of short
spinal reflexes in many instances seems to be rather easier tail ward
than headward.
2. Taken generally, for each afferent root there is in its own
segment a reflex motor path of as low resistance as any open to it
anywhere. In other words, each single afferent root, or a single
filament of it, evokes a special reflex movement with a minimal
stimulus.
3. The different motor mechanisms for the skeletal musculature
lying in the same spinal segment exhibit markedly unequal
accessibility to the local afferent impulses. So that in many
animals it is easier to arouse reflex contraction of the flexors of the
homonymous knee and the extensors of the coutralateral than of
the extensors of the homonymous and the flexors of the contra-
lateral knee, although the respective motor fibres may be contained
in the same efferent root.
4. When a spinal reflex discharge is prolonged, it usually
1 Sherrington, Sc/tafcr's Text-Book of Physiology, 1900, vol. ii. p. 849.
314 PHYSIOLOGY CHAP.
involves antagonistic sets of motor cells alternately, e.g. the
alternate movement of flexion and extension.
5. The groups of motor nerve -cells contemporaneously dis-
charged by spinal reflex action innervate synergic and not
antergic muscles.
6. The reflex movements that may be elicited in and from any
one spinal region exhibit much uniformity despite considerable
variety of the locus of incidence of the exciting stimulus. Approxi-
mately the same movement, e.g. in the hind-limb flexion of the
three great joints, will result, whatever piece of the limb surface
be irritated. The seat of incidence of the stimulus will only
influence the movement in so far that the flexion will tend to
occur predominantly at that joint, the flexor muscles of which are
innervated by motor cells segment ally near to the entrance of the
afferent fibres from the particular piece of skin which is the seat of
application of the stimulus.
The laws, or rather the rules which govern the course of irradia-
tion in long spinal reflexes, were formulated by Pfliiger in 1853.
They can be stated as follows :—
(a) Law of homonymous conduction for unilateral reflexes. If
a stimulus applied to a sensory nerve provokes muscular move-
ments solely on one side of the body, that side is without exception
that which is the seat of application of the stimulus. This
statement, as already known to Johannes Miiller, does not
completely express the facts. For instance, when the tail is
touched on one side, it is in many animals, from the fish to the
mammal, moved towards the opposite side, i.e. the reflex is dis-
charged by the musculature of the side opposite to the seat of
excitation.
(&) Law of the bilateral symmetry of the reflex action. When
the excitation evokes movements on both sides, those muscles of
the opposite side first come into play which are symmetrical with
those already excited in the homonymous half of the cord. This
statement, although true of a number of instances, fails to conform
with fact in many others. The important crossed reflex from the
hind-limb of the bird and mammal does not conform to it, and
Luchsinger observed on narcotised dogs that excitation of a front
limb evokes reflexes from the hind -limb on the opposite side.
This crossed reflex, which occurs very frequently in mammals
(Sherrington), is probably connected with the co-ordination of the
spinal centres for progression.
(c) Law of unequal intensity of bilateral reflexes. When
excitation of a sensory nerve elicits bilateral reflexes of unequal
intensity, the side of stronger contractions is always homonymous
with the seat of application of the stimulus. This law also
.suffers exceptions. The abduction of the tail from the side
stimulated, referred to above, and the " torticollis " reflex towards
v SPINAL COED AND NEEVES 315
the opposite side from that excited, are examples of reflexes
opposed to this law.
(fZ) The irradiation of reflexes spreads more easily towards than
away from the medulla oblongata, i.e. downwards from the cranial
nerves, upwards from the spinal nerves. When the excitation of
a sensory cranial nerve spreads reflexly to a motor nerve, this
nerve, according to Piiuger, is at approximately the same level in
the central organ as, or lower but never higher than, the sensory
nerve. If the excitation spreads farther the direction of irradiation
is always downwards, towards the bulb. Thus on exciting the
optic nerve the pupil contracts, i.e. the impulse passes from the
optic to the oculomotor nerve, and thence, from above downwards,
towards the bulb. In the cord, on the other hand, the motor nerve
first excited is at the same level as the sensory root through which
the excitation passes, but when the reHex spreads the path of
irradiation is, according to Pfliiger, always upwards, towards the
bulb. Thus excitation of the finger evokes reflexes in the cervical
region of the cord, and on spreading, the excitation passes through
the cervical cord to the nuclei of the spinal accessory, vagus, etc.,
and not to the thoracic and lumbar parts of the cord. It is only
after reaching the bulb that the excitation is able to spread down-
wards to the lumbo-sacral region.
This law is the most disputed of all, as it presents the most
exceptions. It contradicts the observations of Sherrington, who
observed in mammals that in the majority of instances irradiation
spreads more easily down than up the cord. It is easier to obtain
reflex movements of the limbs and tail by excitation of the skin of
the pinna than the reverse ; it is more difficult to elicit a move-
ment of the lore-limb by excitation of the hind-limb than the
reverse.
Sherrington endeavoured to determine the salient features of
long intraspinal reflexes in normal mammals and in those in which
the cord is severed from the brain. The animal is supported
freely from above with its spinal axis horizontal, so that the
attitude of the limbs is determined by gravitation. On exciting
different areas of skin under these conditions, he found that
certain areas discharge reflexes to the skeletal musculature more
easily than others. These areas are the soles, the palms, the
pinnae, the tail, the perineal region ; and with the exception of
the last these areas are those which possess the greatest range of
motility. Irradiation from these reflexigenous areas takes place in
a definite order. If, e.g., in the cat with isolated cord (Sherrington's
" spinal cat ") the left hind-limb is stimulated, movement is excited
in that leg, which spreads to the tail, then to the right hind-limb,
lastly to the left fore-limb. If the left fore-limb is stimulated, the
movement spreads thence to the left hind-limb, the tail, the right
hind-limb, and lastly the right fore-limb. If the left pinna be
316 PHYSIOLOGY CHAP.
stimulated the irradiation is from left hind-limb to left fore-limb,
tail, right hind-limb, right fore-limb.
Generally speaking, we may accept Sherrington's statement
that the reflexes from spinal animals are very analogous to those
obtained from normal animals. The latter of course exhibit
greater variability in their reflex reactions. The long spinal
reflexes are generally more variable and less constant than the
short reflexes.
From this discussion it will be seen that Pfliiger's laws now
have little more than a historical interest, owing to the exceptions
discovered to them. If any general rules for the origin and spread
of reflexes are to be formulated it is all-essential to take their
"biological significance" (Langendorff) into account, as deduced
from the fact that they almost always represent a reaction co-
ordinated to a given end, and useful to the organism as a whole.
Bagiioni (1904-7), who analysed the reflexes that can be
obtained from the "spinal frog" after the bloodless severance of
the medulla oblongata (compression by a clamp), when the animal
can survive for a long time, was able to demonstrate that different
retiex mechanisms exist potentially in the spinal cord, the
manifestation of which depends not so much upon the seat, the
intensity, and the duration as upon the nature of the peripheral
stimulus. Gentle pressure with the finger or other blunt object
on the sole of the foot excites an extensor reflex of the hind-
liinb with spread of the toes of the same foot, so that the web
presses against the impinging finger (plantar reflex). Painful
stimulation (e.g. electrical, chemical, mechanical, pricking with the
point of a pin, or compression with forceps) of the same point of
the skin evokes the opposite reflex, i.e. flexion of the hind-limb
and contraction of the web, so that the foot is moved always from
the stimulus and the limb drawn up to the body.
Similar reflexes have been demonstrated by Sherrington (1904)
on the "spinal dog," by Bagiioni and Matteucci (1909) on the
"spinal pigeon," and by G. Cesana (1911) on rats after the three
first days of life. (In the earliest hours of life the rat always
responds by a movement of flexion (Cesana).)
On the strength of these facts Bagiioni distinguishes two
classes of reflex actions: those due to abnormal injurious stimuli,
and those due to normal (biological or functional) stimuli.
(</.) In the first class the reflex movements are in proportion to
the strength and duration of the stimuli. If these are weak or of
short duration, the reflex aims at removing the point of the body
abnormally stimulated ; if they are strong or protracted, this
movement is succeeded by more complicated reflexes directed to
remove the obnoxious stinmlus.
(&) The reflexes of the second class are in relation, not with the
strength or duration, but with the nature of the stimulus, which is
v SPINAL CORD AND NERVES .".IT
not an injurious factor from which the animal must escape, but a
condition favourable to the normal development of useful functions.
Thus the plantar reflex is a rellex which the animal usually carries
out in walking or leaping. It represents the extensor reaction
of the limb applied to the ground for the purpose of raising the
body.
The reflexes of the second category do not for the most part
spread to different muscles, like the reflexes of the first class, when
the strength or duration of the stimulus is increased; they behave,
on the contrary, more as if they conformed to the " all or nothing "
law of the heart.
Finally Baglioni has brought out the fact that reflexes of the
first class are usually produced by injurious electrical or chemical
stimuli such as Pfliiger employed. To evoke reflexes of the second
category it is necessary to use adequate stimuli, and to apply them
to the peripheral sense organs which normally receive them, and
•not to exposed nerve trunks.
VIII. The nature of any reflex movement is determined by
the quality, intensity, and seat of the stimulation, and lastly by
the state of the centres that participate in the reflex.
All the different modes of cutaneous stimulation (electrical,
mechanical, thermal, chemical) are capable, even when they induce
painful sensations, of evoking spinal reflexes. The. form of the
movement may differ, however, with the nature of the excitation.
For instance, the tail of the eel, according to Pfluger's experiments,
moves towards a tactile stimulus, and away from a painful
stimulus. Certain special reflexes only come off with specific
stimuli ; gentle patting of the skin of a dog's flank may cause a
rhythmical scratching movement.
It is easier to evoke a reflex by weak mechanical stimulation
of the skin than by strong induction shocks applied directly to a
nerve trunk. Faradisation of the central end of a muscular nerve,
for instance, has much less effect on respiratory rhythm and on
blood pressure than the stimulation of a cutaneous nerve : in the
first case there is a fall, in the second a rise, of blood pressure.
Excitation of the dorsal roots induces reflexes more easily than
stimulation of the peripheral nerve-endings in the skin ; but in
the second case the reaction is more like an ordinary co-ordinated
movement, while in the first it resembles a reflex spasm. This
shows that in mammals the spinal roots are less a functional than
a purely morphological complex ; the functional combinations of
the root filaments are first formed in the nerve plexuses.
The character of the reflex is also influenced by the intensity
of the stimulation, independently of any change in the nature of
the afferent impulse. A weak stimulus evokes a reflex reaction
that is transmitted to a few efferent fibres ; a stronger stimulus
causes the reflex to spread to many efferent, fibres. But there is
318 PHYSIOLOGY CHAP.
no strict relation between strength of stimulus and extent and
duration of reflex. According to Slier rington, the reflex arc some-
times behaves like cardiac muscle, which responds to stimuli by
maximal contractions or not at all (supra^). In any case it is
certain that the internal conditions of the reflex arc have more
influence upon the degree of the reaction than the strength of
external stimulus.
The seat of stimulation is an important factor in determining
the character of the reflex movements. The reflexes evoked by
stimulating the viscera are different from those excited by
cutaneous stimulation ; these, again, vary greatly according to the
point stimulated. This fact is easily demonstrated on the spinal
decerebrated frog. The constancy of the various reflex reactions
obtained on exciting different points of the frog's skin (by bits of
paper saturated with acidulated water) tends to show the existence
of a functional mechanism in the cord in which the character of
the reflexes is determined by the spatial position of tbe spot at
which the excitation arises. This is true, not only for cutaneous
sensations, but also for those which originate from the sensory
nerves of the muscles, tendons, and joints, and serve to identify
the position of the limbs in consciousness.
Lastly, the character of the reflexes depends to a great extent
on the intrinsic conditions of the cord, i.e. the state of excitability
and conductivity of the spinal centres. Reflex excitability can be
raised or lowered by the action of specific toxic substances ; it is
depressed or abolished by anaesthetics, particularly with chloro-
form : reinforced by convulsants, especially strychnine. Various
diseases that involve the spinal cord produce a rise or fall in reflex
excitability, like poisons, so that the reflexes are exaggerated or
abolished.
The functional condition of the spinal centres is chiefly
dependent on the circulation and the respiration. A spinal frog
in which the circulation is arrested by tying the heart, or tbe
blood is replaced by an isotonic salt solution, reacts to cutaneous
stimulation for about half an hour if the temperature is low ; for
a shorter time with a higher temperature. In the spinal rabbit,
according to Sherrington, the reflexes do not last more than a
minute after the arrest of circulation at the normal temperature.
But if the animal had previously been cooled, the reflexes may
persist much longer. Both anaemia and asphyxia, before they
abolish the reflexes, cause temporary exaggeration, shown by a rise
of blood pressure, contraction of the bladder, erection of hairs, and
convulsive movements.
In addition to these variations of reflex excitability and con-
ductivity in the spinal centres, which are produced by coarse
alterations in their physiological conditions, we must take into
consideration the other more delicate changes in the state of the
v SPINAL COED AND NERVES 319
said centres, due to the transient physiological processes known as
inhibition and facilitation (Bahnung).
The reflex actions of a spinal segment depend, not only on the
excitations that reach it by the respective afferent paths, but also
on influences from other portions of the nervous system. These
influences may be of such a character as to moderate or depress
its activity, or they may augment it. In the first case there is
inhibition, in the second facilitation, of the reflex.
Inhibition, first discovered by the Webers in the action of the
excited vagus on the heart, was applied to the physiology of the
nervous system by Setschenow (1863). He observed that the frog
deprived of its whole brain developed stronger reflexes and reacted
to weaker stimuli. But if the cerebral hemispheres alone, without
the optic lobes and remainder of the brain, were extirpated, the
reflexes were not much affected. If, finally, the optic lobes of the
decerebrated frog were stimulated, e.g. with a crystal of salt, it was
•seen to withdraw its foot from the acidulated water much later
than the normal frog. Setschenow concluded that the mesen-
cephalon is an inhibitory organ for spinal reflexes.
Inhibitory reflexes were subsequently obtained from other
parts of the brain, and also from the cord itself, by direct or reflex
excitation.
In the higher mammals, where the cord contains long cortico-
spinal paths, the brain has a marked inhibitory influence upon the
spinal reflexes, and these are facilitated by the removal of the
cortex or transection of the cortico- spinal paths. Both in the dog
and in the ape this phenomenon is easily verified a short time
after the operation, i.e. when the spinal exaltation is due to the
onset of Wallerian degeneration, which acts as a continuous
irritant of the spinal tissue. That the brain can function as an
inhibitory organ for the spinal reflexes appears from the everyday
experience that we can sometimes voluntarily arrest, at other
times delay, more often modify certain reflexes, e.g. micturition,
defaecation, coughing, sneezing, etc.
Another well-established fact is that excitation of one part
of the cord is able to inhibit the reflex activity of other parts.
This is seen particularly from the experiments of Goltz. If in the
spinal frog the sciatic nerve is stimulated electrically, no reflex is
evoked by applying acidulated paper to the skin. The arrest of
the frog's heart by rhythmically tapping the intestines does not
come off if the foot is pinched at the same time. The spinal snake
makes rhythmical pendulous movements which cease when its
body is lightly touched. Micturition already in progress can be
interrupted in a spinal dog by pinching the hind-foot or tail. In
the spinal cat suspended horizontally with relaxed limbs stimula-
tion of the skin of one foot causes drawing up of the homonymous
and extension of the contralateral limb; when both feet are
320 PHYSIOLOGY CHAP.
stimulated simultaneously the extensors are inhibited and the
flexors of both sides are thrown into contraction.
Inhibition of a spinal centre through other centres probably,
according to Sherrington, plays a great part in the co-ordination of
the spinal acts. In fact, his researches show that the contraction
of any group of muscles is usually accompanied by the inhibition
of the antagonist group. The tension of the muscle in consequence
of its contraction mechanically excites its sensory apparatus
(inusculo-tcridinous organ of Golgi) and thus reflexly depresses the
tone of the antagonist muscle. On faradising the central end of
the nerve of the femoral biceps of the cat the effect of this
stimulation on the extensor muscles of the knee is shown by their
elongation and the temporary diminution of the patellar reflex.
FIG. 184. — Myograms of weak tonic contraction of m. extensor communis of toes. (Verworn.)
The arrows indicate the times at which there is reflex inhibition of tone after crushing the
antagonist muscles. The curves are reduced to §.
If the flexor muscle of the leg is detached from its insertion and
then stretched or compressed, there is, as with electrical stimulation,
a relaxation of the extensor muscle of the knee and a weakening
of the knee-jerk. To confirm these effects, which Sherrington calls
reciprocal innervation of antagonist muscles, Verworn performed
the following experiment on the dog : he isolated the branch of
the peroneal nerve by which the m. extensor lougus communis of
the foot is innervated, detached this muscle from its insertion, and
connected it with a recording apparatus, after fixing the limb by
a plaster bandage. On stimulating the nerve at regular intervals
of one second, he obtained a tracing of approximately equal con-
tractions. On pinching the flexor muscles with a large forceps
during this periodical stimulation he obtained a temporary fall in
the level of the contractions, which indicates a reflex depression of
the tone in the muscle due to the mechanical excitation of its
antagonist (Fig. 184).
v SPINAL COIU) AND NKKVKS 321
The iiihiltition due to direct or indirect excitation of a spinal
centre is usually quite transient in decerebrated animals. When
the stimulation is sufficiently prolonged, the inhibition is followed
by a functional rise, which accords well with the alternating clonic
character of the muscular reactions in decerebrated animals.
Transection of the cord also induces inhibition in its caudal
segments, which is more pronounced in the segments nearest the
section and gradually declines in the more remote segments. This
is plain from Eoseuthal's experiments (1873). He showed that
the latent time of the reflex evoked in the frog's hind-limb by
stimulating the skin of the opposite limb is longer in low than
in high transection. Bickel at a later date (1898) proved on the
frog, salamander, and tortoise that the reaction time is longer
when the cord is cut below the brachial plexus than when it is
divided immediately below the medulla oblongata. Further, De
Boeck (1887) found that a stronger stimulus was needed to excite
a reflex in the rabbit when the cord was divided than when the
section lay above the spinal bulb.
The opposite effect, facilitation or augmentation (Bahnuny}
of the spinal reflexes, was first pointed out by Exner in 1882.
He saw in the rabbit that on simultaneously stimulating the
cortical centre for a given muscle of the leg and a point on the
skin of the leg by which the same muscle was excited, the reflex
contraction was more energetic than when the cortex alone, or
the skin alone, was excited. On reducing the strength of the
cutaneous stimulus till it became subliminal, it was made efficient
again when a cortical stimulus was applied two seconds pre-
viously. Adequate skin stimuli similarly rendered subliminal
cortical stimuli effective. When both stimuli — taken singly — were
O v
subliminal, each made the other efficient if the interval between
them did not exceed one-eighth of a second.
Sherrington gives other instances of reflex facilitation. He
states that the reflex excited from an afferent root of a spinal
animal by a given minimal stimulus can be evoked by a weaker
stimulus when other adjacent roots are previously excited.
In 1905 he analysed the fundamental characteristics of a
specific reflex in the dog, the "scratch reflex." On applying
certain stimuli within a wide saddle-shaped zone of the skin on
the back and flanks (Fig. 185) of a dog, after high thoracic tran-
sectiou, the hind-leg on the same side executes a scratching move-
ment. This movement is produced by flexion of the hip, knee,
and ankle, which is rhythmically repeated about four times a
second. The sensory nerve-endings which discharge the reflex
(the " receptors ") lie on the surface of the skin and seem to be in
close relation with the hair follicles. The reflex can be evoked by
mechanical stimuli — rubbing the skin or lightly pulling the hair-
as well as by electrical excitation — weak faradic currents, constant
VOL. m Y
322
PHYSIOLOGY
CHAP.
currents, and alternating currents of high frequency. The reflex
consists in a series of short rapid contractions of the flexors of the
hip, the frequency of which is independent of that of the excitation.
The reflex path runs, as shown by the method of successive sections,
in the external part of the lateral column.
The chief characteristic of this reflex is that one and the same
reaction can be elicited from a comparatively large sensory area
(Sherrington's receptive field), so that a whole series of afferent
(sensory) mechanisms are in connection with the same efferent
(motor) mechanism.
" At the commencement of every reflex arc," Sherrington writes,
" is a receptive neurone extending from the receptive surface to
the central nervous organ. This neurone forms the sole avenue
which impulses generated at its receptive point can use whitherso-
FIG. 185. — Receptive field for scratch reflex in dog with complete cervical
transaction. (Sherrington.)
ever be their destination. This neurone is therefore a path
exclusive to the impulses generated at its own receptive point, and
other receptive points than its own cannot employ it.
" But at the termination of every reflex arc we find a final
neurone, the ultimate conductive link to an effector organ, muscle,
or gland. This last link in the chain, e.g. the motor neurone,
differs obviously in one important respect from the first link of
the chain. It does not subserve exclusively impulses generated at
one single receptive source, but receives impulses from many
receptive sources situate in many and various regions of the body.
It is the sole path which all impulses, no matter whence they
come, must travel if they are to act on the muscle-fibres to which
it leads. . . .
" Eeflex arcs show, therefore, the general features that the
initial neurone of each is a private path exclusively belonging to a
single receptive point (or a small group of points) ; and that finally
the arcs embouch into a path leading to an effector organ ; and
v SPINAL CORD AND NKliVKS 323
that their final path is common to all receptive points wheresoever
they lie in the body, so long as they have connection with the
effector organ in question. The terminal path may, to distinguish
it from iuternuncial common paths, be called tin- Jinal common
path. The motor nerve to a muscle is a collection of final common
paths." 1
Given this special arrangement of the various elements which
constitute a reflex arc, a series of important theoretical conclusions
capable of explaining the phenomena of facilitation and inhibition,
as seen in the reciprocal action of the various reflexes, can be
deduced. It is obvious that when several receptors connected with
the same common path are simultaneously excited, their individual
effects must be either summated so as to reinforce, or neutralised
so as to inhibit, according as the reflexes which they separately
excite harmonise or are incompatible. Sherrington terms the
former " allied," the latter " antagonist," reflexes. He has demon-
strated a series of such reflexes on the dog, which were either
allied to, or inhibitory of, the " scratch " reflex.
IX. It is a vexed question whether the spinal cord is
capable of automatic as well as reflex activity. The rhythmic
respiratory movements that may persist after dividing the bulb
are of a doubtful character (Vol. I. p. 502). The tone of the
sphincters and of the blood-vessels, which we discussed in the
physiology of digestion and circulation (Vol. II. Chaps, III. and VI.,
Vol. I. Chap. X.), is probably due to the action of constant or
frequently repeated extrinsic stimuli. The tone of the common
skeletal muscles in the resting state, which undoubtedly depends
on spinal tonus, is again not automatic but reflex in character, as
conies out plainly from Brondgeest's experiments. If the sciatic
of one hind-limb be divided in a spinal frog suspended vertically,
the flexor muscles of that limb are relaxed, while those of the
opposite limb are slightly contracted. This shows that the tone of
the flexor muscles of the hind-limb prevails over those of the
extensor muscles after removal of the brain, and that this muscular
tone depends on spinal tonicity. If instead of cutting the sciatic
its posterior roots are divided (Cyon), the tone of the flexors also
disappears. This shows that the tone of the spinal centre is not
automatic but reflex, i.e. it depends on a continuous wave of
excitation which flows through the sensory fibres to the centre,
and thence back to the muscles.
Chloroform and ether, like transection of the afferent roots,
abolish the tone of the spinal cord.
The tonic influence of the afferent roots seems not to be
derived exclusively from the sensitive cutaneous surface, as Brond-
geest assumed. In fact it persists in the frog even when the whole
1 Sherrington, The Intcyrative Action of the Nervous System, London, 1906.
pp. 115 and 116.
324
PHYSIOLOGY
CHAP.
of the skin has been removed, according to Moinmsen. There
must, therefore, be other paths of excitation besides the cutaneous
nerves, probably from the sensory nerve-endings in the muscles
and tendons.
Since the spinal tone that governs muscular tone is reflex,
not automatic, it may be asked whether it depends exclusively
upon the afferent excitations and is a constant quantity, or can
FIG. 186. — Tracings of homulateral reflexes of hind-limb of marsh tortoise, obtained with uniform
and rhythmically recurrent stimuli. (Fano.) To avoid confusion between the separate reflexes
by (superposition of the curves, a special mechanical contrivance was fitted by which the
writing-point was removed from the drum at a given moment after stimulation. The points of
stimulation are marked below the series of curves, and the time in ^},n sec. The vertical
lines that coincide with each stimulation were ruled with a T square to show the reaction-time.
Tracings reduced by J.
vary automatically, independent of any extrinsic influence, in
consequence of periodic oscillations or variations in the excitability
and metabolism of the central organ ?
Fano (1903) from a systematic study of the reflex movements
of the marsh tortoise (Umi/s palustris) adduced experimental
evidence for the last view. He invented an apparatus by which
the animal could be excited at regular intervals by faradic break
shocks of constant strength, the reflex reactions being recorded at
regular distances on a smoked drum. He proved that the motor
reactions are not uniformly vigorous, but exhibit continuous
SriNAL COED AND NERVES
325
irregularly periodic oscillations. The curves of Fig. 186 represent
this phenomenon. The time marking, obtained from a tuning
fork of 100 vibrations per second, and the exact moment of
stimulation, are recorded below the muscle tracings. By measur-
ing the distance between the single stimuli and the corresponding
reactions, the latent period of the latter is arrived at. Another
interesting fact then comes out, that besides the irregular periodic
oscillations in the amplitude of the reactions, there are similar
oscillations in the reaction time.
Fano's experiments demonstrate that the automatic variations
of special excitability above described, which give a character of
irregular oscillating periodicity to the spinal tone in the tortoise,
FIG. 187. — Tracing a.s in last figure, after cervical transection of the cord. (Fano.)
depend on influences coming from the brain, particularly from
the medulla oblongata. These periodic oscillations diminish when
by removing the fore-brain the inhibitory influence of the mid-
brain is unchecked. If the optic lobes are also destroyed, so that
the automatic activity of the bulb is given free rein, the oscilla-
tions once more become very conspicuous and far exceed those
observed under normal conditions. After dividing the thoracic
cord they diminish considerably in the hind-limbs ; after cervical
transection they decrease in the fore-limbs (Fig. 187).
Fano's observations give further confirmation of the inhibitory
influence of the optic lobes already referred to (p. 319), and of the
automatic activity of the spinal bulb, to be discussed in the next
chapter. These automatic oscillations of the excitability of the
cord are merely the spread, almost one might say the reflection, of
those more marked waves that occur in the bulb, the existence of
326
PHYSIOLOGY
CHAP.
which was deduced by us as early as 1879 from the critical analysis
of periodic respiration (Vol. I. p. 492).
Langendorff (1905) has recently confirmed Fano's observations
for the oscillations of intensity in the reflex movements of the
tortoise. But he was unable to admit their dependence on
impulses from the bulb, since they persisted after high tran-
section of the cord. Scheven in the rabbit noticed analogous
oscillations of the patellar reflex, which is evoked by the rhythmical
application of single mechanical stimuli (M///YA).
According to Gr. Cesana (1911), in the new-born rat oscillations
in the height of the reflex contractions are seen from the earliest
A
f
Fin. iss. — Knee-jerk. A, the dotted line indicates the movement produced l>y lapping the
palellar tendon: B, the same obtained by a hammer when it does not occur readily in the
usual way.
days of life, and these, contrary to what occurs in the adult, persist
even after transection below the medulla oblongata.
The phenomenon of " knee-jerk," first studied by Westphal and
by Erb, is strictly related to the tone of the skeletal muscles.
When the limb is hanging with all the muscles at rest a light
blow on the patellar ligament with the hand, or better with a
small hammer, evokes a sharp contraction of the quadriceps cruris
and an extension of the knee (Fig. 188). Similar effects are seen
in other muscles on mechanically exciting the muscles and tendons
or the periosteum, but the knee-jerk is the most typical and the
best studied.
The indispensable condition for the appearance of the knee-jerk
is some tension or tone in the muscle. The stimulus which evokes
the reaction consists in a gentle but sudden passive increase of
this tension.
v SPINAL COED AND NEEVES 327
The true reflex character of the patellar reflrx or tendon
phenomenon is not universally admitted. According to Brissaud,
Eulenberg, Mac William, Waller, Gowers, and others, the time
elapsing between the mechanical stimulation and the muscular
reaction is too brief for a reflex (via afferent root, cord, and motor
root cells), and corresponds approximately to the latent period in
direct electrical excitation of the muscle, as shown by the curve of
Fig. 189.
But its reflex nature was clearly brought out by Sciamanna
(1900) in some ingenious experiments on a patient with marked
exaggerations of the knee-jerk on the right side ; the right vastus
iuternus muscle also contracted reflexly when the patellar tendon
on the left side was tapped. By means of the graphic method he
showed that the direct and reflex contractions of the leg excited and
FKI. 189. — Comparison of latent period in (1) a direct contraction, (2) the tendon phenomenon,
(3) a reflex contraction. On the rabbit. (Waller.)
those of the opposite side differ perceptibly in the time lost from
the moment of stimulation.
Scheven's latest experiments in Langendorffs laboratory are
also decidedly in favour of the reflex nature of the knee-jerk. In
the rabbit he compared the latent period in direct electrical
stimulation of the muscle and after mechanical stimulation of the
patellar tendon. His method enabled him to record the moment
of stimulation with great accuracy in both cases, while he avoided
the usual errors due to inertia of the lever. On direct stimulation
of the muscle he found the latent period to be on an average
O'Oll sec., while in the knee-jerk it amounted to 0-022 sec., i.e.
nearly double the former. This is excellently shown in Fig. 190,
in which the upper line (d.s.) gives the curve of the m. extensor
cruris with direct stimulation ; the lower (r.s.), which starts much
later from the abscissa, shows the mechanically excited reflex
contraction of the same muscle.
Scheven also recorded a long series of patellar reflexes evoked
by rhythmical stimuli, with the object of establishing the
influence of specific conditions of stimulation on the height
328 PHYSIOLOGY CHAP.
of the reflex contractions. He saw that even with perfect
equality of stimulation periodical variations in the height oi
the contractions, corresponding to those which Fauo observed
on the tortoise, were always present. He attributed these to
corresponding variations in the excitability of the spinal centres.
Fatigue was practically excluded under Scheveu's experimental
conditions. In one experiment he recorded some 900 reflex
contractions, excited at intervals of one second, without fatigue,
as noted by Treves in his experiments on man, with the ergograph
(Chap. I. p. 51). The height of the contractions increased in
direct ratio with the height from which the hammer dropped to
arouse the reflex, and rose rapidly at first and then more slowly to
the maximum when the height of drop was about 30 cm. On
FKJ. 1!'0. -Comparison of contraction from extensor muscle of raliliit's leg to direct electrical
stimulation (il.x.), and reflex mechanical stimulation (/•.*.). (Scheven.) Tunin.n-foi k 100
vibrations per second.
further increasing the drop the height of the twitch declined,
probably owing to inhibition caused by the strong excitation of
the afferent cutaneous nerves. Specially important is the fact that
the height of the contraction depended to a large extent upon the
stimulation frequency ; the smaller the interval between two
stimuli, up to a certain point, the higher was the contraction.
This is undoubtedly an effect of summation of stimuli, and as
summation is a property of the nervous centres (see last chapter)
this fact also testifies strongly to the reflex nature of the knee-jerk.
Whether the knee-jerk be regarded as a reflex or not, it is in
any case dependent on the integrity of a spinal reflex arc — the
afferent limb of which conducts from the sensory organs in the
muscle itself and its appendages — to which is due the tone or state
of tension in the latter during rest. If the afferent nerves of the
muscle or its motor or sensory roots are divided, the knee-jerk is
abolished ; while it persists, and may even be increased, if all the
v SPINAL CORD AND NERVES 329
other afferent nerve paths to the limb are severed. The integrity
of the reiiex arc seems a necessity, either because the stimulus
mechanically excited from the patellar ligament traverses this arc
in order to throw the muscle into contraction, or because it main-
tains the mild tonic tension in the muscle which is the sine qua
non of the slight passive extension — this again acting on the
muscle as a direct stimulus. The dependence of the knee-jerk on
the excitability of the spinal centres is also shown by the fact that
it is favoured by the waking state and by voluntary activity ; it
is depressed during sleep, anaesthesia, and spinal anaemia ; and it
is abolished by the inhibitory excitation of the afferent nerves of
the antagonist muscles (Sherrington — supra).
Speaking generally, it may be said that the patellar reflex
faithfully follows the oscillations in spinal excitability, showing
now a rise and now a fall. Hence it may almost be taken as a
very delicate physiological indicator of the tone of the nerve-
centres in general, and those of the cord in particular. In this
lies its great clinical value. Its disappearance is a characteristic
symptom in locomotor ataxy ; its exaggeration is indicative of those
descending processes of degeneration in the cord which are associated
with the pronounced exaggeration of muscular tone, clinically known
as spasticity.
Experimentally the knee-jerk has been the object of much
study, and some of the experiments bear directly on the physio-
logy of the spinal cord. The conditions which intensify the
reflex are : electrical excitation of the central end of the sciatic on
the opposite side ; stimulation of the skin or mucous membrane
0-2-04 sec, before the jerk is elicited ; a flash of light ; a sudden
sound preceding the jerk by 0'2-0'3 sec. ; two taps on the tendon
at a short interval ; lastly, rest, food, etc. Other conditions depress
or abolish the phenomenon either immediately or after a brief re-
inforcement ; as local fatigue of the extensor muscles, general
fatigue, local anaemia produced by an Esmarch's bandage, arrest
of circulation in the lumbar region, inhalation of chloroform or
ether, etc.
Sherrington says that in the monkey spinal transection usually
abolishes the jerk for a week or so. In the dog and cat it can be
evoked in a quarter of an hour or less from the time of the opera-
tion, while Barbe stated that he obtained the phenomenon in man
immediately after decapitation. On the other hand, complete
destruction of the cord in the thoracic region usually seems to
abolish the knee-jerk permanently.
The reflex spinal mechanism connected with the knee-jerk of
each side is unilateral and lies in its own half of the cord. As
shown by the diagram (Fig. 191), the reflex centre in the monkey
lies in the fourth and fifth lumbar segments (chiefly the fourth in
man). If the cord be split in the median sagittal plane the jerk
330
PHYSIOLOGY
CHAP.
4L (3) '
5L(4) "
6L(5)
on either side is not impaired. Spinal transaction and transection
at the junction of diencephalon or mesencephalon increase the
briskness of the jerk, and after ablation of the Eolandic cortex, on
one side, the contralateral knee-jerk usually becomes more brisk.
Jeudrassik noticed that a voluntary movement of the arm at the
time the knee-jerk is being elicited augments it ; and that if the
jerk is very feeble it may be reinforced by making the patient
interclench his fingers and pull them apart strongly (Jendrdssik's
grip). This is probably due to the fact that con-
traction of the arm-muscles relaxes the muscles of
the leg, and thus cuts out the tone by which
the patellar reflex is inhibited. According
to Bowditch and Warren, the effect is most
marked when the patellar tap is delivered
0'2-0'6 sec. after the voluntary move-
uient of the arm.
X. In close association with the
tonic action of the spinal centres is
the trophic action which they
exert upon other centres and
upon the peripheral tissues.
We have already reviewed
the arguments which
underlie the Wal-
lerian doctrine that
Or nll~
nnvHrrn
P
Ol the nCUTOne
.1
represents the
trmihip ppntrp nf
HOpIl
all ifq ^lrnpp^sPc!
(\L1. JLLO \JL WV-'C/OO^O.
.
We kllOW further
, i • .-i
that in the
central nervous
system the normal trophic influence is exerted in the same
direction as the physiological conduction of excitation ; it is the
sensory neurones that control the nutrition of the motor neurones,
and not the reverse. On interrupting the relations of inter-
dependent groups of nerve-cells, there is arrest of development
(agenesis) if the growth of parts is still incomplete, secondary
atrophy if development is already perfect. After section of the
sensory roots not only do their central ends degenerate, but trophic
changes may be seen in the corresponding motor root cells
(Warrington, 1897).
In this connection we must confine ourselves to the group of
well-known phenomena which show that the spinal nerves and
their centres, as well as the centres of the brain, are to some extent
FIG. 11H.— Diagram to show nervous
mechanism of knee-jerk. (Sherring-
ton.) 4L-18, 4th-7th lumbar and
1st saci'al roots of Modulus; the
corresponding roots in man are
numbered in brackets (the 7th
lumbar pair in monkey corresponds
to 1st sacral in man); cr.n., crural
nerve ; sc.m., sciatic nerve — afferent
., ,. L j -, , , , , ..
paths indicated by dotted lines,
etterent by broken lines ; m.ext, ex-
tensor muscle ; m.flex, flexor muscle.
v SPINAL COED AND NEEVES 331
capable of profoundly modifying the nutritive condition of other
tissues, from which it has been attempted to build up the theory
of the existence of a special category of nerves, with the function
of directly regulating the metabolism and nutrition of the tissues,
—the so-called trophic nerves. We must examine the data lief ore
testing the theoretical value of the conclusions based on them.
According to Louget, Mayo (1823) was one of the first who
called attention to the fact that after lesions of the trigeminal
nerve the conjunctiva of the eye becomes inflamed, the cornea
ulcerated, and the face on the side of the lesion oedematous.
Similar clinical observations were made by other observers. First
Fodera, then Magendie and Longet, reproduced these changes
experimentally on rabbits, by intercranial section of the trigemiuus
with a special hooked knife. In addition to panophthalmitis
Bernard, Biitner, and Eollet subsecpuently noted ulcerations of the
lips and buccal cavity.
Magendie (1824) observed that when the section was made
above the Gasserian ganglion, the dystrophic changes in the eye
set in more slowly or were entirely absent, while they inevitably
appeared if the lesion involved the ganglion. Bernard (1868)
confirmed these results from his clinical observations. Longet
attributed the alterations in the eye after lesions of the Gasserian
ganglion to the simultaneous injury to the sympathetic filaments
that pass from the carotid branch of the superior cervical ganglion
to the Gasserian ganglion, but Bernard does not support this view.
In his opinion the extirpation of the superior cervical ganglion
delays the trophic disturbances in the eye after section of the
trigeminus, by increasing the circulation and augmenting the
vitality of the eye and its resistance to the post-operative causes
of the dystrophy.
Sinitzin's experiments (1871) confirmed and extended those
of Bernard. On piercing with a glass thread the cornea of a rabbit
in which the superior cervical ganglion had previously been ex-
tirpated, there was usually no inflammatory reaction ; whereas
the same operation performed on the other eye caused extensive
conjunctivitis with iritis, and sometimes panophthalmitis. Section
of the trigeminus produced no corneal ulceration when the superior
cervical ganglion had been destroyed shortly before or immediately
after. Lastly, the eye troubles caused by section of the trigeminus
rapidly cleared up if the ganglion was excised.
These results, contradicted by Eckhard and by Senftleben
(1873), were confirmed by Spallitta in Marcacci's laboratory (1894)
by some successful experiments on dogs, which he sums up as
follows : —
(a) Lesions of the Gasserian ganglion constantly induce the
trophic lesions of the eye already described by Fodera and
Magendie and confirmed by later observers.
PHYSIOLOGY CHAP.
Previous destruction of the superior cervical ganglion
prevents the trophic changes which result from injury of the
Gasserian ganglion alone.
(c) When disturbances appear in the eye after the double
operation, they are constantly recovered from.
(d) Animals from which the Gasserian ganglion alone is removed,
and those in which this lesion was preceded by destruction of the
superior cervical ganglion present totally dissimilar symptoms in
the eye, independent of whether the trophic alterations are present
or not.
Schiff, Mantegazza, Vulpiau, studied the after-effects of tran-
section of the spinal nerves to the limbs. After dividing the sciatic
and crural nerves, Schiff found in the adult dog, cat, and frog that
three to six months after the operation the bones of the operated
limb were smaller than those of the normal limb. Mantegazza
and many others afterwards drew attention to the muscular atrophy
which appears after sensory and motor paralysis of the limb. In
two to three weeks the muscle fibres begin to atrophy, and after
some months or years they are converted into a tissue resembling
connective tissue. Loss of excitability goes parallel with the
atrophy, and the electrical reaction of degeneration appears.
Bidder noted that a few weeks after section of the nerves to
the salivary glands these become about half the size of the healthy
glands on the opposite side. Nelaton emphasised the clinical fact
that the testis atrophies after section of the spermatic nerves.
On dividing this nerve in animals, sparing the blood-vessels of the
spermatic cord and the vas deferens as far as possible, Obolensky
saw that the testis dwindled in two to three weeks, and almost dis-
appeared after four months. Histological examination showed that
the glandular tissue had almost disappeared, and was replaced by
connective tissue and fat. When, on the contrary, the spermatic
nerves are spared and the vas deferens is divided, there is no
apparent change in the testis.
In Baldi's experiments (1889) in our laboratory, on the effects
of section of the afferent or efferent roots in dogs he paid particular
attention to the trophic changes in the skin. Clinical observation
had already shown that the diseases of motor and sensory nerves
are accompanied by alterations in the nutrition, not only of muscle,
but of other peripheral tissues as well; cutaneous ulceratiou, for
instance, is particularly frequent after lesions of the peripheral
nerves. In order to investigate the origin of this dystrophy, Baldi
operated on a series of dogs, cutting in some the dorsal, in others
the ventral, roots, which subserve the sensibility or the motility,
respectively, of an entire fore- or hind-limb, on one or both sides.
The first effect in the limb that has become completely
insensitive is neuro-paralytic hyperaemia, shown in the rise of
temperature and reddening of the skin. This is very transient,
v SPINAL COED AND NEliVKS .",.",:',
and disappears after a few days, even before the complete healing
of the spinal wound.
As soon as the wound is healed, and the animal begins to
move about, an abnormal erosion of the nails is noticed, followed
shortly after by loss of hair on the dorsum of the foot and by
some excoriation. If the animal is left to itself an ulcer soon
forms that involves the derma and subjacent tissues, the capsules
of the joints open, and the phalanges and even the metatarsal
bones fall off. To prevent this, or to heal the lesions, it is
necessary to keep the insensitive limb constantly in bandages. In
dogs with bilateral transaction of the sensory roots of the lumbo-
sacral region the cutaneous alterations set in more rapidly. After
this operation the animal cannot retain either faeces or urine, so
that precautions must be taken to prevent irritation from these
sources. Immediately after the operation the rectal mucosa and
the penis are slightly relaxed and markedly hyperaemic ; but in
time the hyperaemia disappears and the parts are apparently normal.
Before long, however, erythema, ulcerations, ,and other lesions of
the tissues of the limbs set in, and become incurable unless treated
with the greatest care.
The effects of dividing the motor roots to a hind-limb differ
little from the above. Essentially different, however, are the
effects of simple transection of the cord between the last dorsal
and the first lumbar vertebrae, as repeatedly carried out by Goltz.
After the shock effects have disappeared and the wound has
healed, these animals exhibit no dystrophic changes in the tissues
of the limbs, although in progression they drag either the perineum
or one or the other hip on the ground, and pull the posterior parts
of the trunk along, since it receives no voluntary impulses.
If in dogs in which the dorsal roots or ventral roots of one
hind-limb are cut the hair of both hind-legs is shaved off in two
corresponding areas, the hair in the limb operated on takes more
than twice as long to regain its original length, and the new coat
is thinner and poorer than that of the normal limb. The nails,
too, grow more slowly in the limb operated on than in the normal
limb. If croton oil is smeared upon symmetrical areas of both
limbs, the blister appears twenty-four hours later in the operated
leg, and the new epidermis forms a fortnight later than in the
healthy limb.
Under the microscope the skin of the insensitive limb is
seen to be much atrophied and the Malpighian layer sometimes
disappears.
Various hypotheses have been put forward to account for these
trophic disturbances consequent on nerve lesions. The following
are among the more general and widely accepted :—
(«) The dystrophic effects are produced by the neuro-paralytic
hyperaemia which sets up disorders of nutrition in the tissues ;
334 PHYSIOLOGY CHAP.
They depend on external trauma or irritation, against which
the operated animal is no longer able to protect itself;
(c) They depend on both these factors, since the neuro-paralytic
hyperaemia makes the tissues more vulnerable to external injuries ;
(d~) They depend on loss of the influence of the nerves which
regulate the nutritive processes and metabolism of the tissues.
The first hypothesis, supported by Fodera, Magendie, Longet, is
clearly controverted by the experimental results of Bernard,
Sinitziu, and Spallitta, which show that, on the contrary, under
special conditions, hyperaemia may even promote the nutrition of
the tissues. Moreover, the hypothesis takes no account of the
fact that hyperaemia is a transitory phenomenon and that the
trophic lesions often make their first appearance after it has
disappeared.
The second theory, first propounded by Snellen and Bonders,
is based on the fact that after section of the trigemiual or of the
facial nerve the panophthalmitis could be warded off for six to ten
days if the eye were artificially protected from injury or irritation
by particles of dust. It was severely shaken by the experiments
of Meissuer, who observed panophthalmitis after a partial lesion of
the trigeminus which had not entirely destroyed the sensibility of
the cornea, On the other hand, Baldi's observations show that
even if traumatic irritation is often a necessary factor in trophic
disturbance it is not sufficient of itself to cause it. It must
therefore be assumed that parts which are deprived of their inner-
vation exhibit a lower resistance or greater vulnerability, so that
they can be injured by slight irritants that do not affect tissues to
which the nerves are intact.
In what, then, does this lessened resistance or greater vulner-
ability in the denervated tissues consist ? Schiff explained the
pauophthalmitis consequent on section of the trigeminus by the
third of the hypotheses enumerated above, and held that the
lowered resistance of the eye results from the neuro-paralytic
hyperaemia, owing to which particles suspended in the air,
which do not injure the normal eye, become the cause of
panophthalmitis.
This theory, too, is in direct contradiction with the experiments
of Sinitzin and Spallitta. After ablation of the superior cervical
ganglion the neuro-paralytic hyperaemia of the eye should be more
pronounced than that which, according to Schiff, sets in after
simple lesion of the trigeminus. But the trophic disturbances in
the eye may be altogether absent. Schiff's view is moreover
inadequate to explain Baldi's interesting observations on the
retarded growth of hair and nails, and the slow regeneration of the
epidermis and cicatrisation of wounds in a limb with sensory
paralysis. It is evident that these, as well as the atrophy of the
muscles and other tissues, including the skin, are the effects of loss
v SPINAL COED ANT) NERVES 335
of the trophic influence of the nerves and their corresponding
centres.
But this trophic influence must not be taken in the sense
previously suggested by Meissuer and Samuel, viz. that there is
a special category of trophic nerves and centres, entirely distinct
from the sensory and the motor, whose function is the direct
control of metabolism and nutrition of the tissues, independently
of both the blood and lymph circulation, and of the new conditions
of functional paralysis set up in the tissues after the section or
lesion of their respective nerves. Any such hypothesis, besides
being, unsupported by experimental facts, is contrary to the spirit
of the cell theory, according to which the function of living
cells is inseparable from their nutrition, because every excitation
necessarily has an altered metabolism for its material basis.
When the function of a cell or organ is under the direct and
absolute influence of another cell or organ (as the muscle depends
upon the nerve), then the latter by controlling the function must
also indirectly control the nutrition of the former.
XI. In discussing the spinal reflexes we saw that there is a
certain relation between the sensory surface stimulated and the
reflex. In a spinal (or bulbo-spinal) animal direct stimulation
of the central end of a large nerve only evokes a spasmodic unco-
ordinated reflex, in which muscles of different or even antagonistic
function are simultaneously thrown into action ; on stimulation of
a sensory surface, on the contrary, the combination of the muscles
thrown into play is much more complex, and the reflex is repre-
sented by a true co-ordinated motor act, in which not only do
many muscles take part, but there is an evident harmony between
the strength, duration, and precise moment of the contraction of
each muscle that participates in the action. In fact, the expression
" co-ordinated muscular act " means that the whole movement is
directed towards the attainment of a useful effect in the most
profitable manner, and that the muscular reaction is perfectly
adapted to the stimulus, so that there is an ideal teleological
relation between them.
Grainger (1837) seems to have been the first who pointed out
that the reflex spinal movements excited by cutaneous stimuli
were defensive in character, and apparently directed to the purpose
of removing the stimulus.
The most classical example of these defence reflexes of force is
seen in the spinal or bulbo-spinal frog. The crouching position
that it naturally assumes shews that the spinal centres are in
continuous activity, because a paralysed animal stays in any
position given to it. If the leg is pinched, it is drawn away as
though to escape from a painful impression. If a bit of paper
soaked in dilute sulphuric or acetic acid is applied to any point
of its skin, the frog performs a whole series of movements, which
336 PHYSIOLOGY CHAP.
are perfectly co-ordinated to the eiid of removing the obnoxious
stimulus.
Besides these defensive acts, there are other co-ordinated
reflexes in the spinal frog connected with the reproductive
functions. Goltz observed that whenever a decerebrated male
frog is gently stroked on the skin of its back, it croaks as if to
express pleasure. In the breeding season if the back of a female
frog, or even the finger of the observer, is placed in contact with
the skin of the thorax of the male, the fore-limbs clasp the object
strongly and persistently, as in the normal sexual embrace.
In mammals, too, it is possible to observe co-ordinated reflexes
in portions of the cord that are entirely separated from the brain,
for instance in the lumbar enlargement, after transection in the
thoracic segments. Ten days after the operation, when the effects
of " shock " have quieted down, the animal will pass urine only
when the bladder is full, or when the skin of the perineum is
tickled. So too, it only defaecates or performs movements of
defalcation when the anal orifice is tickled, and during expulsion of
the faeces it lifts its tail and shifts and flexes its hind-limbs as if try-
ing not to soil itself. If the skin of the animal is lightly stimulated
in the sacral region, the foot on the same side makes rhythmical
movements of alternate flexion and extension, as it normally does
in scratching. If the penis is excited by masturbatory manipula-
tions the phenomena of erection and spermatic ejaculation follow,
associated with movements or postures of the hind-limbs that
express voluptuous sensations.
These and other phenomena admirably described by Goltz and
his pupils are co-ordinated reflex actions, designed to satisfy a
want or to protect some part of the body from injurious stimuli.
In other less frequent cases the motive of the reflex seems to be
preservation of the individual while the part is sacrificed. This
interesting group of phenomena were investigated by Fredericq,
and termed by him autolomy. More particularly in certain
insects (grasshoy>pers), crustaceans, arachnids, echiuoderms, if a
limb is mechanically or chemically stimulated, it suddenly breaks
and drops off, so that the animal is able to escape from the pursuer.
The same phenomenon is also seen in certain vertebrates, as in the
blind-worm and green lizard, which readily part with their tails
to escape capture. The fracture of the limb or tail is effected by
a violent reflex contraction of certain muscles by a mechanism
which is not fully known. Since the phenomena of autotomy
persist in decapitated animals they witness to a solidarity of
action, almost one might say a personality of the spinal cord when
it is separated from the cerebrum.
Even in the absence of external stimuli, the spinal animal
sometimes carries out complex actions which differ little from
those of the intact animal. It is an ancient observation that
v SPINAL CORD AND NERVES 3:(»7
fowls can fly directly after decapitation. Tarchanoffs observations
on ducks are more interesting. After trausection of the cord
between the 4th and 5th cervical vertebrae they can perform a
long series of perfectly regular swimming movements in the water,
both with the feet and the wings. But if placed on a table they are
incapable of standing upright, although they execute regular
alternating movements of walking with their legs.
In man, too, complex co-ordinated reflexes of defence have
been observed in cases of contusion or dislocation of the cord in
the cervical or thoracic region. Marshall Hall describes a man
whose cord was crushed at the neck by a fall. There was complete
motor and sensory paralysis of the lower half of the body, but
when stimulated either with painful mechanical stimuli, or with
hot water, or by tickling the soles of the feet, the lower limbs
moved with great vigour as if the patient's cord felt the pain or
was aware of the tickling.
The fully co-ordinated defensive movements carried out in
sleep (e.g. in response to bites of fleas or mosquitoes), and many
quite unconscious movements made during the waking state,
while the attention is otherwise occupied, are similar, and should
probably be classed among the purely spinal co-ordinated reflexes.
All these instances illustrate the great complexity of the
spinal reflexes — a complexity that cannot be explained by the
simple spread of excitation from the afferent nerves into adjacent
nerve-cells.
An adequate theory of reflexes must throw light on the process
by which the centripetal or afferent excitation becomes centrifugal
or efferent ; it must tell us why the reflex is sometimes confined
to a few muscles, and at other times spreads to more muscles in
various combinations ; why the efferent impulses travel along
certain paths and not others ; lastly, how the co-ordination and
adaptation of the reflexes to the nature and localisation of the
stimulus is attained. At present we can only give vague and
inadequate replies to these questions, though a few hypothetical
but certainly ingenious attempts have been made towards a partial
solution of the problem on the basis of the neurone theory.
The greater or less irradiation of reflexes and the laws by
which they are governed, are generally explained by the more or
less direct and easy communication between the sensory and
motor neurones concerned ; or the greater or less conductivity
along the paths formed by the fibrillary networks in the grey
matter.
It is harder to explain the adaptation of the reflex to the
stimulus. In this connection the fact is usually cited that habit
facilitates the transmission and association of actions that were
difficult in the first place, which is possibly due to improved con-
ductivity along the paths.
VOL. in z
338 PHYSIOLOGY CHAP.
But these and other more detailed mechanical explanations of
co-ordinated reflexes adapted to stimuli seem inadequate to account
for the variety of the modes in which a brainless frog reacts to
different forms of stimulation. Some authors have maintained,
on the strength of these observations, that the spinal cord itself,
as the continuation of the brain, is also a seat of psychical
functions, and look upon these complex reactions as the expression
of a rudimentary consciousness and volition in the cord, persisting
even after it has been severed from the cerebrum.
This doctrine is contrary to the old metaphysical axiom of
the absolute unity and immateriality, and consequent indivisi-
bility of the ego or soul. This axiom, which the earlier spiritual-
istic philosophy accepted as dogma, is, however, easily controverted
by experimental physiology. The divisibility of the " ego " as
a sentient principle is demonstrated by the fact that a numerous
class of the lower animals are propagated by fission, and are able
to multiply by division into the segments or metameres of which
they consist (Vol. I. p. 84). Each segment is capable of forming an
entity with the same sensorial capacity as the complete individual
of which it was a part. Hence it is not only legitimate, but
scientifically necessary, to inquire whether, on dividing the
cerebrospinal axis in the higher animals, consciousness can be
divided also. The answer to this difficult and possibly still
insoluble problem lies in arguments from analogy, based on the
experimental facts that indirectly witness to the psychical
capacity of the spinal cord.
We conclude that a living being is capable of awareness of
itself and of the world without it ; of controlling its own actions
by will, of having, in fact, a "soul," only from the resemblance
between our own conscious actions and those that it presents.
Thus from the cogito ergo sum, which is the direct intuitive proof
of our own consciousness, we recognise the same in our fellow-men,
then by induction in the higher animals, and lastly in the lower
animals also.
Is the adaptation to end which characterises the movements
of decapitated animals enough to convince us that their spinal
cord is capable of feeling and volition ? Evidently not, because
all the mechanisms of the animal economy are adapted to obvious
ends ; coughing cleanses the air passages ; vomiting empties the
stomach of injurious matters ; contraction of the pupil modifies
the effects of light ; winking of the eyelids removes dust particles
from the cornea ; intestinal peristalsis sends on the faeces, etc. etc.
These co-ordinated mechanisms have come about by a slow process
of natural selection, according to Darwin ; by an evolutionary
automatic process of unknown character, according to Nageli ;
more simply, they represent fossilisation of psychical functions,
having been built up step by step from voluntary actions, which
v SPINAL COED AND NEEVES 339
by long practice became as it were materialised and automatic,
and were transmitted by inheritance. Evidence for the organisa-
tion of what were at the outset voluntary acts, lies both in the
fully unconscious co-ordinated reflexes, which we are able to carry
out not merely in sleep but also in the waking state, and in the
fact that many complex actions that were voluntary at first (e.g.
walking, reading, piano-playing, etc.) become, after long practice,
mechanical, and are carried out with perfect regularity without
the intervention of the will or the least effort of attention.
In order to judge objectively of the psychical or mechanical
character of a given spinal reaction, it is necessary, according to
Pfliiger and Auerbach, to see if it varies from one moment to
another with the variations in external relations. If the individual,
when prevented from carrying out a given movement adapted to
the removal of an obnoxious stimulus, employs another action
directed to the same end, this proves it to be possessed of sentient
functions, because from one moment to the next, without any pre-
existent mechanism, organised by long practice, it knows how to
modify or change the character of the reaction, so as to adapt
it to the required end. Evidence of such a capacity is brought
forward by these authors. They observed that a decerebrated
frog, when a drop of acid falls on its right flank, or, better, when
a bit of paper soaked in acid is applied to it, always uses its right
leg to wipe away the irritant. If the right leg is amputated, it
first makes ineffective efforts with the stump, and then employs
its left leg. If, after amputating the right leg, the acid is applied
to the right side of the back, the frog again makes ineffectual
attempts with the stump, and then stops. But on applying the
acid to the left side of the back also, the frog uses its left foot to
wipe itself on the left as well as on the right side.
Pfliiger insisted on these phenomena as evidence that the
spinal cord of the frog is capable of at least rudimentary psychical
functions. According to other authors, on the contrary, these
actions, besides being rare and generally incomplete, are capable
of a purely mechanical explanation. The fact that when the
limb which the animal uses for removal of the cutaneous stimulus
has been amputated, the limb of the opposite side is resorted to
for' the same purpose after ineffective attempts with the stump, is
held to mean that the local excitation, owing to the longer contact
of the stimulus on the skin, has become more intense, and has
spread from one half of the cord to the other. But if Pfliiger's
description is studied in all its significant details, this mechanical
explanation is obviously inadequate.
Foster, on the other hand, points out that spontaneous move-
ments (automatic movements proper), such as occur in the entire
absence of external stimuli, are never seen in the spinal frog.
This fact appears to him irreconcilable with the existence of any
340 PHYSIOLOGY CHAP.
active consciousness in the cord, that is, of an uninterrupted
sequence of psychical processes and transitional states, as though
an internal stimulus were perpetually acting on the central organ.
He therefore inclines to attribute to the cord a sort of transitory,
discontinuous consciousness, which only surges up in response to
stimuli of a certain intensity, and maintains that our complete
consciousness, and that which we attribute inductively to the
higher animals, is merely the perfect development of this rudi-
mentary spinal consciousness.
" We may, on this view," Foster l writes, " suppose that every
nervous action of a certain intensity or character is accompanied
by some amount of consciousness, which we may, in a way,
compare to the light emitted when a combustion previously giving
rise to invisible heat waxes fiercer. We may thus infer that when
the brainless frog is stirred by some stimulus to a reflex act, the
spinal cord is lit up by a momentary flash of consciousness coming
out of darkness and dying away into darkness again ; and we may
perhaps further infer that such a passing consciousness is the
better developed the larger the portion of the cord involved in the
reflex act and the more complex the movement."
Though direct confirmation of Foster's hypothesis on the
nature of the spinal psychical functions is wanting, it appears to
us to be logical and generally admissible. Those who take the
manifestations of perception and memory as the distinguishing
signs of consciousness, and absolutely deny the psychical character
of co-ordinated reflexes, do not reflect that the spinal cord is not
claimed as the seat of the higher intellectual functions, but only as
that of a simple rudimentary intelligence due to the synthesis of a
small group of elementary sensations. The approach of a dog on
hearing its own name, the return of a hungry animal to the place
where it is accustomed to find food, are conscious acts of perception
involving a process of memory. Of course nothing of the sort can
be observed in a " spinal " animal. According to Goltz' ex-
periments, if two frogs, one normal, the other spinal, are placed in
water and the vessel is gradually heated, the normal frog makes
movements to escape from the water when the temperature rises
to 35° C. ; the spinal frog, on the contrary, makes no attempt to
avoid the danger, and, provided the rise of temperature be gradual,
will let itself be boiled without effort to escape. If, on the other
hand, the spinal frog is thrown into water already heated up to
35° C. it will at once make lively movements, which must,
according to Goltz, be regarded as unconscious reflexes, because
they did not appear under the former conditions of experiment.
But from our point of view, these facts — even if they show that
the spinal frog exhibits no sign of perception and memory — do
not exclude the possibility of its possessing transitory flashes of
1 Foster, Text-Book of Physioloyy, 1897, part iii. p. 983.
v SPINAL COED AND NEKVES 341
consciousness, arising from a psychical synthesis of elementary
sensations.
Lastly, many of those who see in the co-ordinated spinal
reflexes inherited, instinctive, but unconscious acts, do not
recognise that in admitting these they implicitly admit a sort of
fossil intelligence for the cord, — i.e. to adopt Bering's felicitous
expression — unconscious memory of primitive psychical processes.
The entire i " soul " of a brainless Amphioxus is a spinal soul.
How much of this soul persists as such, and how much (to repeat
the metaphor) in a fossil state, in the spinal cord of the higher
vertebrates ? The future must decide.
At first sight it would seem as though the most complex of
the spinal reflexes that are independent of the brain and, in our
opinion, indicate a rudimentary spinal intelligence, should be
more numerous, more striking, and better elaborated in the higher
animals with a more developed nervous system. The contrary,
however, is the fact ; these higher spinal reflexes predominate and 1
are more vigorous and pronounced in the lower vertebrates. This •
of course may be due to the greater solidarity between the
different segments of the system in the higher vertebrates, and the
greater control exerted by the brain over the spinal mechanism,
owing to the development of the long spino-cerebral and cerebro-
spinal conducting paths which are totally absent in the lower
vertebrates.
XII. The long conduction paths which run from the cord to
the brain and from the brain to the cord, constitute so many inter-
central reflex arcs, by means of which the spinal mechanisms of
the higher vertebrates are brought into direct functional com-
munication with the cerebral mechanisms. It is through these
long conducting paths that, with the development of definitely
conscious sensations and voluntary movements, the spinal cord
ceases to be a collection of autonomous centres and becomes an
instrument of the brain.
We have seen that the cord is capable of executing perfectly
co-ordinated reflex movements. In voluntary movements impulses
descending from the brain throw the same spinal mechanisms into
play as are concerned in the execution of the spinal reflexes
excited by impulses conducted from the periphery along the
afferent nerves. Indeed, since reflex movements differ from
voluntary in nothing except the exciting agent, it would be
irrational to suppose that they depend on two separate central
mechanisms.
Marshall Hall's theory, which distinguished the spinal reflexes
from the voluntary movements by assuming an excito -motor system
consisting of fibres separate from those of sensation and voluntary
motion, has long been abandoned. The anatomy of the cord shows,
as we have seen, that the same neurones, by coming into relation
342 PHYSIOLOGY CHAP.
through their collaterals with the cells of the ventral roots, are
excito-motor, and belong to the spinal reflex arcs ; and by sending
ax oils cere! >ral wards, act as sensory nerves, and are part of a cere-
bral reflex arc. On the other hand, the peripheral motor neurones
function as involuntary or reflex fibres when they react to stimuli
received through the dorsal roots, and as voluntary motor nerves
when excited by the pyramidal tracts.
Thus the cells of the spinal mechanisms are not merely in
relation with local functions of the cord, but also send impulses to
the cerebral nerve-cells and receive others from them in turn.
The phylogenetic evolution of the nervous system goes pari passu
with an ever-increasing development of the long spi no-cerebral
and cerebro-spinal conducting paths. The pyramidal tract, which in
the higher vertebrates represents the complex of the long cerebro-
spinal motor conducting paths, increases gradully in bulk and
attains its maximal development in man. The direct ventral
pyramidal tract only appears in man, and, according to Sherrington,
in the ape. In rats and guinea-pigs, according to Lenhossek, the
pyramidal tracts are small and run in the dorsal columns : while
in rabbits, cats, dogs, they pass, according to Spitzka, through the
lateral columns, after decussating in the medulla oblongata. In
the cat (Boyer), in the dog (Muratoff), in the monkey (Mellus and
Sherrington), and sometimes in man also (Pitres), there is a small
direct lateral pyramidal tract, as the bulbar decussation is not
always complete. In the lower vertebrates (amphibia, reptiles, and
also birds), it is probable that there are no cortico-spinal nor long
centripetal tracts, such as are present in the higher vertebrates
with a well-developed cerebral cortex.
It is essential to bear in mind the varying development and
course of the cerebro-spinal and spino-cerebral conducting tracts
in different classes of vertebrates, in order to avoid the error which
the older physiologists fell into, when they applied the data
obtained from the physiological effects of partial transections of
the cord in the lower vertebrates to human physiology.
We have seen that complete transection of the cord produces
paraplegia by interrupting all the conduction paths. We must,
therefore, confine ourselves to studying the effects of partial
spinal transection upon the motility and sensibility of the more
caudal parts, by experiments on the vertebrates nearest to man,
as well as from the simpler and least equivocal clinical
observations.
Clinical cases of cerebral lesions taught us long since that the
motor and sensory paths decussate in the cerebro-spinal axis.
Haemorrhage in the right brain causes motor and sensory
paralysis of the left half, and when in the left brain, of the right
half of the body. Brown-Sequard, however, records certain
exceptions to this rule, which can be explained either by an
v SPINAL COED AND NERVES 343
anomalous failure of the conducting paths to decussate, or by a
double decussation. Clinical cases have in i'act been dm-.ribed in
which the one or the other had occurred. But these exceptions
are rare.
Does this decussation occur in the brain, in the bulb, or in the
cord I The interhemispherical commissure, the so-called corpus
eallosiim, contains simple paths of interhemispherical association,
and is not related to cerebro-spinal conducting paths. The
majority of the motor cerebro-spinal fibres which form the
pyramidal tracts cross in the bull), while many of the fibres
which do not cross here (direct ventral and lateral pyramidal
bundles) decussate in the cord, passing from one side to the other
by the white and grey commissures. In any case a partial spinal
decussation of the motor paths is established, both by histological
facts and by bilateral descending degeneration of the direct and
crossed pyramidal tracts after unilateral traumatic injury or
pathological lesions of the cord (W. Miiller, Charcot, Pitres, and
others).
The decussation of the sensory paths is known to occur partly
in the so-called interolivary region of the bulb, above and dorsal
to the decussation of the motor pyramidal tracts ; but certain
collaterals of the medullated fibres of the dorsal roots also cross
through the anterior commissure. It may therefore be stated in
general terms that anatomical facts show that the long motor and
sensory conduction paths cross from one side to the other, to a
small extent in the cord, to a much larger extent in the brain-stem.
The effects of unilateral section of the cord must now be con-
sidered in more detail.
Few problems in the physiology of the nervous system have
been more discussed, and the results and interpretation differ
widely.
Galen was the first who performed and attempted to follow up
the total or partial transection of the cord (probably on monkeys),
and it is astonishing to see how closely his results agree with the
most recent observations.
Many workers took up this subject in the early half of the
nineteenth century, but after the first experiments of Fodera
(1823), Schops (1827), J. van Been (1838), Valentin (1839),
Stilling (1842), Budge (1842), Eigenbrodt (1848), the only authors
who published repeated communications upon it were Brown-
Sequard in France and M. Schiff in Germany and Italy.
Brown-Sequard's theory, which was accepted by most physio-
logists and quoted in nearly all text-books of the physiology and
pathology of the nervous .system, may be summed up in the
following propositions : (a) Nearly all the motor fibres cross in the
medulla oblougata, very few in the cord ; (6) nearly all the sensory
paths cross in the cord, very few in the medulla oblongata.
344 PHYSIOLOGY CHAP.
The experimental basis of this theory consisted in the fact that
after hemisection of the cord there is, according to Brown-Sequard,
direct motor and crossed sensory paralysis. The former is asso-
ciated with slight paralysis of the opposite side ; the latter is
accompanied not by hypoaesthesia, but by hyperaesthesia on the
side of the section. Many clinical cases of unilateral spinal lesions
confirm the results of these hemisection experiments performed on
various vertebrates.
But it can be objected to Brown-Sequard's experimental results
that the animals were under observation for too short a time :
that the sensory changes was frequently tested directly after a
severe operative trauma ; that there was no microscopic control of
the operations ; lastly, that Brown-Sequard's own description of
some of the results of his experiments contradict his conclusions,
and rather suggest that each half of the cord contains sensory
fibres from both halves of the body. It is evident that he allowed
himself to be influenced in his experimental observations by the
preconceived ideas which he had formed from his clinical observa-
tions. The latter, again, are far from invariably confirming his
conclusions, and in many cases the seat of the lesion has not been
exactly localised by anatomical examination.
Schiff, too, occupied himself in detail with the effects of spinal
hemisection. In his experimental observations (as we learn from
his most reliable pupil and successor A. Herzen) he was always
guided by the following rules :
(1) If a function is found to persist immediately, or a few
minutes or hours, after the transection of a part of the cord, this
is a definite proof that it is independent of the part divided, and
is connected with other parts that have not been injured.
(2) If under these conditions there is a loss of function, this
does not prove relation between this function and the injured part,
unless the loss persist for weeks and months after the operation,
till cicatrisation is complete, the effect of shock entirely worn off,
and the animal as far recovered as the operative lesion permits.
Under these irreproachable criteria, Schiff arrived at the
following results from his experiments on unilateral transection
of the cord :
(a) At whatever level one half of the cord is divided, a series
of phenomena, some transitory, others permanent, can be seen.
The former consist in a diminution of pain sensibility on the
opposite side, which may amount to total analgesia ; various motor
disturbances on both sides ; frequently hyperaesthesia to pain of
the injured side, associated with vascular dilatation. The only
permanent symptom is the abolition of tactile sensibility on the
side of the lesion in all the more caudal parts.
(6) After transection of the whole spinal cord with the
exception of the posterior columns in the thoracic region, there is
v SPINAL COED AND NERVES 345
persistence of tactile sensibility, while sensibility to pain is wholly
abolished.
(c) The converse experiment, that is section of the posterior
columns only, while the rest of the spinal cord is left intact, pro-
duces immediate and permanent loss of tactile sensibility, while
pain sensibility persists.
(rf) Section of the ventro-lateral columns does not abolish
tactile or pain sensibility.
(V) Two lateral hemisections, right and left, at different levels,
Fin. 102. — Seetiun of ventral and thoracic columns with nearly the whole of the j;rey matter in
rabbit — level of last dorsal vertebra. (Woroschiloff.)
at a certain distance from one another, reduce sensibility to pain
on both sides, while tactile sensibility is entirely abolished.
(/) Median longitudinal section of the lumbar cord at the
level at which the nerves to the lower extremities pass out,
diminishes sensibility to pain, while tactile sensibility and motility
remain intact.
From these experiments Schiff formulated the following
theoretical conclusions : Tactile sensibility is carried to the brain
by the fibres of the dorsal columns on the same side, which, there-
fore, do not cross in the cord ; pain sensibility is transmitted by
the grey matter of both sides, but chiefly through the opposite
side ; motor impulses are transmitted by the grey matter and by
the ventro-lateral columns ; the ventro-lateral columns do not
transmit sensory impressions.
346
PHYSIOLOGY
CHAP.
Subsequent research, especially by Miescher (1870), Nawrocki
(1871), Woroschiloff (1874), iu Ludwig's laboratory, led to results
which absolutely contradicted Schiff's conclusion that the lateral
columns do not transmit sensory impressions.
Woroschiloff, who made all his experiments on rabbits, found
that after dividing the dorsal and ventral columns and the whole
of the grey matter in the lower thoracic region, the transmission
of sensory and motor impulses was mot affected ; after section of
the two lateral columns, on the contrary, both are abolished, and
all reflex relations between the posterior and anterior portions of
FIG. 193. — Section of both lateral columns and of a lateral portion of both horns of the grey
matter — level of last dorsal vertebra. (Woroschiloff.)
the body are minimal (Figs. 192, 193). From these experiments
he concluded that the lateral column contained both motor and
sensory paths.
From a subsequent study of the effects of transection of the
cervical cord of the rabbit, Woroschiloff (1878) obtained similar
results, and demonstrated that the sensory and motor paths for
the fore-limbs also run in the lateral columns. The motor paths
lie principally on the same side, the sensory on the side opposite.
This last assertion, which agrees with Brown-Sequard's theory,
is contradicted by some important later experiments on higher
mammals (dogs, monkeys), which tend to show that the conduct-
ing paths for sensibility only cross to a minor extent in the cord.
Among these experiments those of Mott (1892) on the effect
of heuiisection of the cord in monkeys deserve special attention.
SPINAL CORD AND NERVES
347
He found paralysis of voluntary movement in the limbs on the
side of the section, which passes off to a great extent, and defective
sensibility on the same side, which diminishes on the return of
motility. Mott also observed on the operated monkey the symptom
known as allocliciria for pain, and perhaps also for tactile sensi-
bility ; when a point of the skin of the limb on the side of
c
D
Fii;. 194. — Ascending degenerations after spinal hriiiisrrtinn .in "monkey. (Mutt.) D, .site of
complete hemisection of left side, between 5th and (3th thoracic vertebrae ; C, transverse
.sect inn immediately above the level nf the operation; B, section at level of 4th thoracic
\eitebra ; A, section at level of 6th cervical vertebra. The degenerations, as shown by the
lighter parts of the photograph, extend to the tract of Goll, the direct eerebellar tract of
Flechsig, and the ventro-lateral tract of Cowers.
the lesion is stimulated the animal refers the sensation to the
honionymous point on the opposite side. The return of the motor
functions takes place more rapidly for bilateral associated than for
unilateral movements; flexion reappears before extension; the
movements of the ankle-joint before those of the knee and foot :
the movements of the fingers recover only very imperfectly.
The following conclusions may be drawn from Mott's work as
a whole ; the sensory paths do not cross directly after they enter
the spinal cord ; the paths of cutaneous sensibility in general, and
348 PHYSIOLOGY CHAP.
perhaps of muscular sensibility as well, only pass along the same
side of the cord, while the paths for pain or thermal sensibility
pass along both sides.
According to Mott's observations, the ascending degenerations
after hemisection of the cord are sharply limited to the side of the
operation, as shown by the photograph reproduced in Fig. 194.
From this he concluded that the greater part of the crossed fibres
which conduct pain and thermal sensibility must undergo an
interruption in the grey matter of the cord before they pass to
the opposite side.
The importance of Mott's observations lies essentially in their
contradiction of the theory of Brown-Sequard, which held its own
for so many years in physiology and medicine, and in their having
led Brown-Sequard in the last months of his working life (1894)
to renounce his old theory of the decussation of sensory paths in
the cord.
Almost simultaneously with Mott, and while still ignorant of
his important publication (1893), we investigated on dogs the
immediate and remote effects of lateral hemisection of the cord,
which were published by Bottazzi in 1895, together with a critical
review of the subject, and some new experiments of his own. It
is interesting to note the almost complete accordance of our own
conclusions from dogs with those previously published by Mott
from experiments on the monkey.
After transection of the right half of the lower thoracic cord,
we observed («.) immediate paralysis of the right hind-leg passing
into a state of persistent paresis, and temporary paresis of the left
hind-leg ; (6) obvious ataxy of the right hind-leg which became
more pronounced and definite as the motor paralysis diminished ;
(c) serious disturbance of tactile sensibility in both hind-legs im-
mediately after the operation, which disappeared in the left leg with
the period of irritation, but persisted though greatly diminished
in the right ; (d) diminution of pain and thermal sensibility in
both hind-limbs, but much more pronounced in the right leg.
True hyperaesthesia was not observed in any of the dogs we
operated on, but the reflexes were increased in the right hind-leg
after the period of irritation. The ascending degenerations seen
in our dogs involved, as in Mott's experiments, the column of
Goll, the direct cerebellar tract of Flechsig, and the ventro-lateral
tract of Gowers.
In 1891 Gotch and Horsley brought forward another clear
and quite original experimental proof of the theory that the
majority of centripetal impulses pass through the same half of the
spinal cord as that to which they were carried by the dorsal roots.
After hemisection of the lower thoracic region, they examined the
current of action in the various columns of the cord on stimulation
of the sciatic nerve. The maximal galvanometer deflection was
v SPINAL COED AND NEEVES 349
obtained from the dorsal columns, and next from the lateral
columns of the same side.
The difficulty of examining and interpreting the phenomena
due to partial transaction of the spinal cord, particularly the
different disturbances of sensibility, becomes much less when the
observations are made upon man in cases of spinal disease, or local
traumatic lesions of the cord. On the other hand such disease or
injury is rarely sharply circumscribed to one part or one entire
half of the cord, so that the symptoms necessarily vary and their
value is impaired.
In lesions confined to one half of the cord, Kocher (189G)
found that the motor disturbances do not differ from those
observed after hemisection in the higher animals. There is total
homolateral paralysis which diminishes in time and is eventually
reduced to a slight paresis. The sensory disturbances consist in
homolateral hyperaesthesia to contact and to pain, and in many
cases to heat and cold, which also involves the deeper tissues, as
movement of the limbs is very painful. On the side opposite to
the lesion there is as a rule diminished sensibility, which is marked
or slight, according to the extent and severity of the spinal lesion.
Sometimes every form of sensibility is abolished ; more frequently
tactile sensation remains and pain sensation is reduced, with or
without diminished sensibility to heat and cold. But these dis-
turbances of sensibility, whether direct or crossed, are not
permanent, as the homolateral hyperaesthesia and the contra-
lateral anaesthesia or different dissociated hypoaesthesias disappear.
It is thus obvious that Brown-Sequard's syndrome is seen in
the majority of cases of unilateral lesions of the cord.
None of the interpretations so far put forward to explain the
clinical homolateral hyperaesthesia and controlateral anaesthesia
have, however, reconciled these with the experimental observations
on the higher mammals. Serious objections can be brought
against the old doctrine of the spinal decussation of sensory paths,
the chief of which are as follows : (a) simple puncture of the
dorsal cord induces homolateral hyperaesthesia, with motor and
vasoniotor paralysis ; (&) hemisection of the thoracic cord along
with transection of the opposite side of the cervical cord does not
affect the sensibility of the two lower extremities ; (c) the homo-
lateral hyperaesthesia is more marked than the coiitralateral anaes-
thesia, which varies greatly both in man and animals, and
frequently bears no relation to the seat of the lesion ; (rf)
Galen's experiment of dividing the decussating fibres only by
median longitudinal section of the lumbar enlargement does not
abolish but only diminishes sensibility.
Owing to these objections Brown-Sequard gave up his view
that the anaesthesia results from interruption of the crossed
sensory paths, and regarded it as an inhibitory phenomenon, and
350 PHYSIOLOGY CHAP.
the hyperaesthesia as a phenomenon of dynamogeny, without
asserting that these two terms gave any final solution of the
problem, which it must be admitted is still totally obscure.
More recently (1902) Borchert, in H. Muuk's laboratory, made
further experiments on the effects of dividing the dorsal columns
in dogs at different levels of the cord, and investigated the disturb-
ances of tactile, painful, and muscular sensibility in the limbs.
His experiments, controlled by microscopic examinations, showed
that after section of the dorsal columns, not only painful, but also
tactile and muscular sensibility (consciousness of position of limbs)
persisted, so that there was still some power of localisation.
This, according to Borchert, disposes of Schiif's theory that
tactile impulses can only be conducted by the long tibres of the
dorsal columns, while it eliminates the contradiction in the results
observed on man and on the dog. Just as man is still capable
after degeneration of the dorsal columns, as in tabes dorsalis, of
perceiving tactile stimuli, so the dog is not insensitive to them
after experimental division of the same columns.
It follows that tactile sensations must be transmitted by the
short intraspinal afferent paths, and that destruction of the dorsal
columns (Borchert) causes not a qualitative, but only a quantitative
diminution of sensibility.
Finally we must refer to the work of Petren (1902), who made
a careful synthetic review of clinical cases, particularly those with
unilateral lesions of the cord due to traumna, spondylitis, syringo-
myelia, etc. He concludes that tactile sensibility (pressure)
follows two paths in the cord : the one, the long uncrossed path of
the dorsal columns ; the other associated with the paths of the
other forms of cutaneous sensibility. The latter (pain, tempera-
ture) first pass through the dorsal horn of the same side, and then
cross the median line. For the hind-limbs this decussation is
completed by the level of the first lumbar segment, or at latest the
twelfth thoracic segment, never lower down. After crossing, these
paths run upwards in the external half of the lateral column, but
in the higher segments they reach its median half, so that there
is within the lateral column a gradual displacement of fibres from
without inwards. These sensory paths probably correspond with
part of the fibres of the tract of Gowers.
According to Petren, a unilateral lesion of the cord, when not
too low down, only produces crossed anaesthesia. This assumes
two forms : either pain and thermal sensibility are altered, while
tactile sensibility remains normal ; or all forms of cutaneous sensi-
bility are modified. These are the only types found, the first
being the most common.1
1 EDITORIAL NOTK. — The question of sensory conduction in the cord can evi-
dently be definitely settled only by observations of the sensory disturbances pro-
duced by local spinal lesions in man, as in man alone is it possible to investigate
v SPINAL CORD AND NEKVES 351
XIII. We have seen that although the spinal cord is only the
instrument of the 1 train in the execution of voluntary movements,
it may exhibit activity independently of the higher centres in the
so-called reflex movements.
We have further seen that the spinal reflexes vary not only
with the strength of stimulus and the excitability of the centres,
but also with the site of the stimulus. It is therefore necessary
to ascertain what part of the cord is concerned in individual
spinal reflexes, i.e. what is the localisation of their spinal centres.
These problems are difficult to solve, and little progress has
yet been made in this direction. The spinal cord, as we have seen,
consists of a series of segments or myelomeres which are intimately
connected, and more or less linked together into a functional
solidarity, so that the different reflex centres cannot be distin-
guished by separating them — apart from the shock this produces.
It is certain that there are reflex centres which are more or
less scattered throughout the spinal axis, so that we cannot speak
of their localisation in any given region or segment of the cord.
Such are the spinal vasomotor centres and the centres for sweat
secretion discussed in Vol. I. p. 363 et seq., Vol. II. p. 495 et seq.,
and the reflex centres which maintain a tonic and trophic influence
upon the muscles and the other tissues, as discussed in the present
chapter.
In regard to the localisation of the motor (muscular) centres
in the cord, it was formerly supposed that there was a distinct
separation between them, according to their functions (i.e. specific
extensor centres, flexor centres, etc.). Eecent research has not,
however, confirmed this hypothesis. Lapinsky (1903) published
a series of experiments on dogs and rabbits with the object of
determining if there were definite centres in the cord for the
separate groups and segments of the musculature of the limbs.
He usually employed Gudden's method, and examined the retro-
orade degeneration which occurs in the nerve-cells after section of
D O
accurately the state of the various forms of sensibility. But as opportunities of
accurately correlating the clinical symptoms and the site of the lesion are rare, a
final conclusion can be reached only by such extensive investigations as can be
scarcely possible to any one clinician. On the other hand accurate clinical
observations on suitable cases, even when the site and extent of 'the lesion cannot
be verified, can at least show how the various components of sensation are grouped
and arranged in their passage through the cord. The later observations of many
writers, as Petren, Rothmann, and especially of Head and his collaborators, justify
the following conclusions : — Pain and thermal sensibility are conducted through
the opposite ventrolateral columns ; two paths are open to tactile stimuli, one
in the homolateral dorsal column, the other in the opposite ventrolateral column
in the neighbourhood of the pain and thermal paths ; the faculty of localisation is
spatially associated with the tactile impressions in the cord ; the dorsal columns
convey uncrossed the impulses that subserve the sense of position and the appre-
ciation of movement, the recognition of size, shape, form, and weight, the appre-
ciation of vibration and the discrimination of simultaneous contacts (Weber's
compasses).
352 PHYSIOLOGY CHAP.
their axis-cylinder. Lapinsky's results contradicted the conclusions
of previous workers that the motor centres of the cord are segment-
ally arranged in correspondence with the respective segments of the
liinbs they innervate. The cord has no compact columns of cells,
but merely solitary groups at different levels with no definite
boundaries. Still less is it possible, he says, to demonstrate special
centres for the flexors and extensors or for the adductors of the
thigh. The cells with these functions lie at different levels of the
cord and belong to the groups which simultaneously supply their
antagonist muscles. So, too, the idea that each muscle has its
special centre is contradicted by the fact that every muscle receives
nerve -fibres from several ventral roots, and that each of the
larger muscles has centres in several different groups of cells. No
experiments have yet succeeded in demonstrating distinct centres
in the cord for separate muscles, or groups of muscles with the
same function.
Owing particularly to Goltz, who made a prolonged study of
the effects of complete transection of the cord in the lower thoracic
region, we are able to divide the spinal reflex centres into two
groups: those seated in the lurnbo-sacral part of the cord and
those in the cervico-thoracic part. The two enlargements, lumbar
and cervical, may physiologically be regarded as two lower or
subordinate brains, which preside over the sum of the reflex acts
of which these two parts of the cord are capable.
The lower or lurnbo-sacral part of the cord contains the centres
for the following special reflexes :—
(a) The centre for movements of the posterior (lower) limbs;
as we have seen, it is possible in the " spinal " dog with suitable
stimulation of the skin to evoke all the reflex acts of which
the lower part of the animal's trunk is capable.
(&) The ano-spinal centre (Vol. II. p. 372).
(c) The vesico-spinal centre (Vol. II. p. 474).
((/) The centre for erection, the geuito-spinal centre, and the
ecbolic or utero-vaginal centre (which we shall discuss in the
chapter dealing with the functions of the male and female genital
systems ; see Vol. V).
The upper or cervico-thoracic region of the cord contains :—
(«) The centre for movements of the anterior (upper) limbs.
(&) The spinal centres for the respiratory movements (Vol. I.
p. 447).
(c) The spinal centres for the cervical sympathetic, the vaso-
motor and secretory fibres of which run principally to the head.
The so-called cilio-spinal centre, or dilatator of the pupil, dis-
covered by Budge, extends from the lower half of the cervical cord
to the level of the third thoracic segment. Electrical excitation
of this segment region produces mydriasis, like the excitation of
the cervical sympathetic.
v SPINAL COED AND NERVES 353
(<f) The accelerator spinal centres for the heart are in approxi-
mately the same region as the cilio-spinal centre (Vol. I. p. .'!oGj.
From this enumeration it is plain that not only the nerve-
centres for the organs of animal life, but to some extent those of
the visceral function also lie in the spinal cord.
Since the innervation of the organs of visceral life is supplied
directly by the sympathetic ganglion system, a final and interesting
problem here presents itself. Are the functions of the sympathetic
system subordinate to those of the spinal centres, or can they
subsist independently of them ?
To solve this question it is necessary to study the immediate
and remote effects of ablation of the cord. Previous to the
remarkable results obtained by Goltz and Evvald in 1896, such a
research would have been impossible. They first demonstrated
that dogs can survive for many months in a good state of health
after repeated removal of parts of the cord from below up to the
cervical region ; so that the opinion previously maintained by
every one — that in warm-blooded vertebrates the cord is absolutely
indispensable to life, as the regulator of the nutritional processes,
the vascular tone, and the thermal equilibrium of the organism-
is fallacious.
As we have already seen (p. 330), after simple section of the
dorsal roots of the spinal nerves the tissues that become insensitive
are more liable to injury than before. This is, of course, most
marked in the posterior part of the dog with amputated cord.
Patches of decubitus, pustules, erythema, oedema, especially near
the genital organs and anus, are extremely likely to appear ; but
these cutaneous lesions can be avoided or cured by constant and
scrupulous cleanliness. By degrees, however, the skin of the cord-
less animal gradually acquires an increasing resistance to external
injurious influences.
Even more important to the survival of these animals is the
avoidance of a fall in the blood temperature, which is liable to
occur directly after simple transection of the cord, by enclosing
the animal in a chamber with double metal walls, between which
warm water is continually circulated.
The persisting activities in the posterior part of the animal
that has lost its thoracic and lumbo-sacral cord are far more
numerous than would be anticipated a, priori from what we have
learned experimentally with regard to the functions of the spinal
cord. The immediate effects of removal of the cord are principally
due to operative shock. After a few months they diminish
sufficiently to give a clear idea of the great physiological im-
portance of the sympathetic ganglion system, in so far as it is
capable of acting on the organs and tissues of vegetative life,
independently of the spinal system.
Directly after ablation of the thoracic and lumbo-sacral cord,
VOL. in 2 A
354 PHYSIOLOGY CHAP.
the external sphincter of the anus is entirely relaxed ; but after a
few months (as already shown in Vol. II. p. 372) it regains its
tone. It reacts to mechanical traction, to injections of cold
water, to induced currents ; it may also recover the rhythmical
automatic contractions — independent of external stimuli — which it
manifests after simple division of the cord from the higher centres.
From these facts Goltz and Ewald concluded that the anal
sphincter, in addition to the cerebral and spinal centres, possesses
peripheral sympathetic ce'ntres, which possibly lie in the depth
of the muscle.
Unlike the sphincter, which also consists of striated muscle,
all the striated skeletal muscles atrophy. First they lose their
faradic, next their galvanic excitability, lastly, they become
inelastic and are reduced to bundles of connective tissue. The
bones also alter and become brittle. The digestion, which is
disturbed during the first days, becomes normal again in the
course of a few weeks. Defaecation takes place regularly once or
twice a day, and the faeces are natural in appearance. The urine
is clear, free from sugar and albumin. The bladder, which is
paralysed for the first days, gradually recovers its functions, and
after a few months evacuates the urine collected in it periodically
and spontaneously, and when evacuation has taken place the
animal remains dry for hours.
A pregnant bitch, a few hours after extirpation of 94 cm. of
cord, gave birth to five puppies, one of which was left to her to
suckle, which she did perfectly. The puppy sucked all the
mammae in turn, and even the last pair, which were entirely
deprived of spinal innervation, yielded an abundance of milk.
The tone of the blood-vessels in the dog that has lost its cord
recovers completely in a few days. The temperature of the
clenervated posterior limbs becomes the same as that of the
anterior, which are still innervated by the spinal nerves from the
cervical region. From this it can be seen that the vascular tone
does not depend exclusively upon the bulb and cord, as was
formerly supposed, but that even under normal conditions the
sympathetic ganglion system must have an enormous influence
over it.
One sciatic nerve was divided in a dog that had lost the
lumbo-sacral part of its cord ; at first there was a marked difference
in the diameter of the vessels and the temperature of the paralysed
hind-limbs, but after a few days these differences disappeared.
On stimulating the skin of the posterior part of the cordless
animal, it is not possible reflexly to influence the vessels at remote
parts of the skin, but all stimuli have the same local effect in the
posterior as in the anterior part of the animal. Unipolar ex-
citation by induced currents produces pallor of the prolapsed
inucosa of the rectum, and heat and cold affect the cutaneous
v SPINAL CORD AND NERVES 355
\vssds of the hind-limbs in the same way as those of the fore-
liinlis.
Owing to this local excitability of the cutaneous vessels, the
cordless animal is capable of maintaining its normal blood
temperature during marked oscillations of the external tempera-
ture, and though it is necessary to keep it in a chamber with
constant temperature immediately after the operation, this pre-
caution becomes unnecessary in a few weeks.
At the season for changing the coat, a marked difference is
seen in the hair of the anterior and posterior parts of the body ;
in the former it is new and glossy, in the latter it is dull and
lifeless, and conies out at the least pull.
From these phenomena as a whole we must conclude that
the cord is not absolutely indispensable to life in warm-blooded
vertebrates, but that it is important to the visceral functions.
The absence of the spinal centres is responsible for the low
energy with which these functions are carried out under the
exclusive influence of the sympathetic system, and the great
instability in the health and vitality of the cordless animal, which
requires constant care, and easily falls ill and succumbs to
slight causes.
The closure of the anal sphincter in a dog in which the cord
is simply transected is tirmer than after removal of the cord, and
the rhythmic reflex contractions of the anus that are easily seen
in the " spinal " animal are exceedingly rare in the " sympathetic "
animal.
Even more striking is the diminished energy of the vesical
functions in the cordless animal ; the bladder, moreover, is often
infected, and most of the animals die of cystitis and pyelo-
nephritis. Only in rare cases has it been possible to cure the
cystitis when it has once set in.
Digestive disorders, again, are very dangerous to the animal
that has lost its cord.
Finally, in the cordless animal thermal regulation is only
possible with limited variations of the external temperature.
These important observations of Goltz and Ewald on the
symptoms produced by removal of the spinal cord enable us to
appraise the value of the early doctrine (see p. 278), by which the
sympathetic system was held to preside over the functions of
visceral life. Undoubtedly all such activities may subsist and
function in a comparatively normal fashion after removal of all
spinal influence. The office of the spinal system in regard to the
functions of visceral life seems to consist in endowing these
functions with greater energy, and in conferring greater stability
and more solid equilibrium on the general constitution of the
animal.
356 PHYSIOLOGY CHAP
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Journ. of Experiment. Physiol., 1909, ii. 243 ; 1910, iii. 21, 139, 271, and 319 ;
1911, iv. 19, 151, 273, and 331 ; 1912, v. 233 and 237 ; 1913, vi. 25 and 209 ;
1914, vii. 197, 245, 293, 345, 383, and 407.
FOKHES. Reflex Rhythm induced by Concurrent Excitation and Inhibition. Proc.
Roy. Soc., London, 1912, B. Ixxxv. 289.
POUTER. Variations in Irritability of the Reflex Arc in Asphyxia. Amer. Journ.
of Physiol., 1913, xxxi. 223.
SNYDER. The Latency of the Knee-jerk Response in Man as measured by the
Thread Galvanometer. Amer. Journ. of Physiol., 1910, xxvi. 474.
DEASON and ROBP,. On the Pathways for the Bulbar Respiratory Impulses in the
Spinal Cord. Amer. Journ. of Physiol., 1911, xxviii. 57.
HEAD and THOMI'SUX. The Grouping of Afferent Impulses within the Spinal Cord.
Brain, 1906, xxix. 537.
HEAD and HOLMES. Sensory Disturbances from Cerebral Lesions. Brain, 1911,
xxxiv. 102.
PAGE MAY. The Afferent Path. Brain, 1906, xxix. 742.
M'DOUGALL. The Nature of Inhibitory Forces within the Nervous System. Brain,
1903, xxvi. 153.
M'DOUGALL. Conditions of Fatigue in the Central Nervous System. Brain, 1909,
xxxii. 256.
LINGLE. The Mechanism of Muscular Tone. Amer. Journ. of Physiol., 1910,
xxvi. 361.
CAMIS. The Unity of the Motor Centres. Journ. of Physio]., 1909, xxxix. 228-
WALLER. The part played by Sir Charles Bell in the Discovery of the Functions
of Motor and Sensory Nerves (1822). Science Progress, 1911, vi. 78.
CHAPTER VI
SYMPATHETIC SYSTEM
CONTENTS. — 1. Anatomy and histology of fibres and ganglia of sympathetic
system. 2. Peripheral distribution of sympathetic system to the organs which it
innervates. 3. Physiological arrangement of constituent parts of sympathetic
system ; origin and course of efferent fibres. 4. Origin and course of att'en-nt
fibres. 5. Function of peripheral ganglia. Bibliography.
THE Sympathetic System, while intimately connected with the
cerebrospinal axis, differs from it in many respects, especially in
its peripheral distribution. This is evident from the important
researches of Laugley, to whom we are chiefly indebted for our
knowledge of this subject.
Just as the lunibo-sacral part of the cord is able to function
after it has been separated from the cervico-thoracic segments, so
the sympathetic system is able to recover and maintain certain of
its functions — at least for a time and under given conditions of
existence and nutrition — after extirpation of those segments of the
spinal cord with which it is anatomically connected (Goltz).
On account of this property, by which the system which
controls the visceral and involuntary functions of the body is :
distinguished from the spinal nerves that innervate the somatic
organs and depend wholly on their connections with the central
nervous system, Langley has proposed to replace the term
Sympathetic System by the more physiological title Autonomic
Nervous System. But since this autonomy is incomplete, and
there are close anatomical and physiological relations between the
visceral system and the cerebrospinal axis, it seems more con-
sistent to retain the older nomenclature.
In discussing the functions of the visceral organs in the first
two volumes we laid stress on the physiological importance of
individual parts of the sympathetic system ; in tiie present
chapter we have to deal with this system as a whole and with its
general characteristics.
I. The sympathetic nervous system consists of a highly com-
plex arrangement of ganglia, nerve-fibres, and nerve-plexuses,
which are distributed to the different regions of the bod)-.
359
3GO PHYSIOLOGY CHAP.
Anatomically the following parts can be distinguished :—
A. Two nerve cords, running along the ventral surface of the
vertebral column, from the atlas to the coccyx, which are segmentally
interrupted at given points in their course by nodes or ganglia,
and are known as the gangliated cords of the sympathetic
(Fig. 167, p. 279). Each is subdivided into cervical, thoracic,
lumbar, and sacral portions.
The cervical part has three ganglia : superior, middle, and
inferior. The thoracic part contains eleven or twelve ganglia, the
first two or three of which are usually united into a single ganglion
the stellate ganglion — while the lumbar and sacral parts have
five or sometimes only four ganglia each. The ends of the two
chains converge and unite behind the coccyx in a small single
node, the so-called unpaired coccygeal ganglion of Walter.
Each of these ganglia, which Gaskell termed vertebral or lateral
from their position, gives off three branches : (a) fibres which
connect the ganglion with the neighbouring spinal nerves (rami
conimimicantes). Of these, there are two classes : the white rarni,
which consist principally of myelinated nerve-fibres ; and the grey
rarni, composed mainly of non-medullated fibres. These are the
! only paths by which the sympathetic system is united to the
cerebrospmal axis. (6) Branches which connect the several
ganglia among themselves, and consist partly of medullated,
partly of non-medullated, fibres, (c) Branches that either run
directly to the peripheral organs or to ganglia of the sympathetic
system, which lie more peripherally.
B. The large plexuses of the sympathetic, which innervate the
viscera and lie distal to the ganglion chain near the large blood-
vessels. They consist of a network of nerve-fibres, which arise for
the most part in the gangliated cord, but partly also from the
vagus and from ganglia within the plexus. The most important
are : the cardiac plexus ; the caeliac plexus, also called from its
radiate appearance the solar plexus, which is the largest and
richest in the body, and is formed principally of the splanchnic
nerves from branches given off by the 5th or 6th to the 9th or
10th thoracic ganglia; and the hypjjgastricjDlexus.
Gaskell gave the name of prc-vertebral or collateral to the
ganglia of the large plexuses to distinguish them from those of
the ganglion chain, which he termed vertebral or lateral. Besides
these ganglia smaller groups of cells lie more peripherally along
the course of the different nerve trunks, before these enter the
visceral organs they innervate ; Gaskell termed these ganglia of
the third order terminal ganglia.
C. Besides the sympathetic system proper, there are other
central and peripheral nervous structures with similar functional
properties, which must be discussed along with it. Langley
includes in the sympathetic system all the nerves and ganglia
VI
SYMPATHETIC SYSTEM
361
which supply the unstriated muscles of the body (vessels, digestive
tract, excretory ducts, hair follicles), the myocardium, and the
secretory nerves to the glands, in contradistinction to the parts
of the nervous system which innervate the striated skeletal
muscles. But this division by peripheral distribution is not
always possible ; in some parts of the gut (e.g. in the upper parts
of the oesophagus and end of the rectum) striated muscle fibres
are controlled by the sympathetic system.
Langley divides the entire Sympathetic or Autonomic System
FIG. 195.— Two
cells I've mi fi-vvical ganglion of cat. Golgi's incMioil. Highly
(v. Kolliker.) ?*, axon.
niagnified.
into three parts : (a) the sympathetic in the strict sense of the
term; (&) the cnni'ml system (mesencephalic and bulbar), which
supplies the eye, upper part of the digestive tract, heart, and lungs ;
(c) the S((-cral system, which innervates the lower parts of the
digestive tract, the bladder, and the genital organs. We shall
frequently return to this classification.
In its minute structure the sympathetic system presents the
same constituent elements as the rest of the nervous system, viz.
nerve-fibres, ganglion cells, and a complicated fibrillary network
around the ganglion cells which probably originates in the pro-
cesses of the nerve-fibres. The single nerve-fibres unite into nerve
trunks, while the ganglion cells and network of fibrils accumulate
at certain points along their course.
362
PHYSIOLOGY
CHAP.
The cells of the sympathetic, unlike those of the bulbar and
spinal ganglia, are for the most part multipolar and smaller and
almost uniformly round (Fig. 195). Stohr distinguishes three
Motor
IVricellular network
Capsule
Sensory spinal
nerve-fibre
Sympathetic (?)
fibre
Section through
- peiirapsular
network
Surface view of
" perk'Hpsular
network.
Sti-llate cell
Nerve process
Lamellar
capsule
Fio. 196.— Diagrammatic. Elements of two sympathetic ganglia. (Stohr.) 1, 2, 3, cells of
first, second, and third type.
types of ganglion cells (Fig. 196) to which no distinctive function
can at present be attributed.
The nerve-fibres are of two kinds. The first are ordinary
medullated nerve-fibres, which are found in the white rami
communicantes ; these, which connect the spinal cord and the
sympathetic, originate in the cells of the lateral horn of the cord,
and conduct to the ganglia of the lateral chain.
vi SYMPATHETIC SYSTEM 363
The second variety are the so-called fibres of IJemak, which
have no niyelin sheath and present a grey appearance. They are
derived from the cells of the sympathetic ganglia, and connect
these with the peripheral organs.
The general rule that the white (myelinated) fibres of the
sympathetic system descend from the spinal cord (efferent paths)
or ascend to the cord (afferent paths) and thus belong entirely to
the cerebrospinal axis, while the grey (non-medullated) fibres
spring from the sympathetic ganglia and belong to the sympathetic
system in the narrower sense, is, according to Langley, liable to
exceptions. For example, he says that the nerves of the sym-
pathetic ganglia which innervate the muscles of the feathers in
birds are all myelinated.
II. The peripheral organs supplied by the fibres of the sym-
pathetic have already been discussed in the preceding volumes, but
may here be recapitulated :—
(a) The sphincter of the iris and pupil, contraction of which
diminishes the size of the pupil.
(&) The ciliary muscles, contraction of which relaxes the zonule
of Zinu and accommodates the eye for near objects.
Both these muscles are innervated, as are most of the striated
muscles of the eye, by the third cranial nerve ; but the fibres
destined for these unstriated muscles are, unlike those for the
other muscles, interrupted in a peripheral ganglion, the ciliary
ganglion, like all sympathetic fibres ; accordingly, they must be
included in the sympathetic system.
(c) The dilatator pupillae, the functional antagonist of the
sphincter of the pupil, contraction of which widens the pupil.
(rf) The plain muscle fibres found in the orbital tissues,
Tenon's capsule, and the eyelids, which enlarge the palpebral
fissure, protrude the eyeball and retract the eyelids. In some
animals there are also muscle fibres in the nictitating membrane
in the internal angle of the orbit, contraction of which retracts
this membrane.
(f) The musculature of the blood-vessels of the eye, which
when contracted constricts the blood-vessels of the conjunctiva,
iris, etc. The lachrymal glands also receive fibres from the
sympathetic, which on stimulation cause a secretion of tears.
All these nerve -fibres spring from the superior cervical
ganglion. We shall later discuss their connections with the
spinal cord.
Next to the sympathetic fibres that supply the eye come those
which are distributed to the surface of the body to innervate the
plain muscle fibres of the various organs of the skin. These
are :—
(a) The muscle fibres of the cutaneous vessels, contraction of
which constricts the vascular lumen and diminishes the amount
364 PHYSIOLOGY CHAP.
of blood circulating, producing pallor aud coldness in the corre-
sponding cutaneous regions ; their relaxation has the opposite effect.
(/3) The muscle fibres of the hair follicles, whose contraction
produces "goose skin." The study of the innervation of these
organs, which are specially developed in the cat, provided Langley
with a means of determining the arrangement and distribution
of the sympathetic fibres. He found, however (1904), that in this
animal the conditions were more complex than in the other
mammals, as there are two sets of antagonist muscles, one of
which, the more powerful, prevails over the other in artificial
stimulation, and causes depression of the hairs, while the other
causes their erection. In man, owing to the retrogression of
the piliferous system, the muscles of the hair follicles are of no
great importance. Erection of the hairs produces " goose skin "
after stimulation by cold and in certain emotions, as fear, etc.
(y) The ducts of certain cutaneous glands, e.g. the mammtiry
glands, are provided with contractile elements, which are con-
trolled by the sympathetic system.
The different glands of the skin, in particular the sweat glands
and sebaceous glands, are also innervated by the sympathetic.
The second large and important province governed almost
exclusively by the sympathetic system includes the visceral
organs in the strict sense, viz. the organs of circulation (heart,
blood- and lymph-vessels) ; and the digestive system, both its
unstriated muscles — on which the co-ordiuated movements of the
stomach and intestines, defalcation, micturition, etc., depend — and
its secretory glands.
On the following page is Langley 's Table l with a few minor
alterations. It sums up the various functions of the sympathetic
system in its widest sense.
III. The first problem to be studied in the physiology of the
sympathetic nervous system is its intimate structure, the origin
and course of its nerve-fibres, and the relations in which these
stand with the several ganglia.
As we know, two different experimental methods can be
utilised in tracing the course of the nerve-fibres ; one anatomical,
based on Waller's law (p. 233), according to which the part of
the nerve that is severed from its trophic centre degenerates ;
the other, physiological, based on the phenomena which appear
on exciting the central or peripheral end of the cut nerve, or the
functional disturbances seen after the cutting, cooling, poisoning,
etc., of the nerve.
We must first consider the origin and course of the efferent
nerve-fibres (motor or secretory).
The only path followed by the nerve-fibres which connect the
cerebrospinal axis with the ganglion chain of the sympathetic,
1 Langley, Ergebnisse der Physiologic, 1903, Jahrgang ii. Abteihmg ii. p. 830.
VI
SYMPATHETIC SYSTEM
365
Mid-brain
autonomic
Bulbar
autonomic
Sacral
a titonomic
Effects of stimulating the mid-bram,
luillar ami s;ici-;il mil i ni'iniir l
Contraction of iris
Contraction of ciliary muscle
Inhibition of heart, and of
vessels of mucous membranes
of head
Motor and inhibitory effects on
smooth musculature of gut
from oesophagus to descend-
ing colon
Motor and inhibitory effects on
muscles of trachea and lungs
? Secretion of gastric glands,
liver, and pancreas
Inhibition of arteries of rectum,
anus, and external generative
organs
Contraction of smooth muscula-
ture of descending colon,
rectum, and aiius
Inhibition of smooth muscles of
anus
Contraction of bladder
Inhibition (? contraction) of
urethra
Inhibition of muscles of external
generative organs
nl' si imllhlt ini; till- s.VIII-
]i:itlir1 1C IIITNPS.
Contraction of dilator of iris
Contraction of unstriated orbital
muscle
Contraction of arteries of eye
Acceleration of heart and con-
traction of blood-vessels in
mucous membranes of head
Inhibitory and motor effects on
smooth musculature of gut
from oesophagus to descend-
ing colon
? Secretion of gastric glands,
liver and pancreas
Contraction of vessels of gut
from oesophagus to descend-
ing colon
? Contraction of vessels of lung
Contraction of vessels of abdom-
inal viscera
Contraction of musculature of
spleen, ureters and internal
generative organs
Contraction of smooth muscles,
and arteries of skin
Secretion of cutaneous glands
Contraction of arteries of rectum,
anus, and external generative
organs
Inhibition and contraction of
smooth musculature of de-
scending colon, rectum, and
anus
Inhibition and contraction of
bladder
Contraction (? inhibition) of
urethra
Contraction of muscles of
external generative organs
is through the rami coinrnunicantes. We have seen (p. 292, et seq.)
that the Bell-Magendie law holds good for the sympathetic fibres,
except that the vaso-dilator fibres to the fore- and hind-limbs, in
the dog at least, leave the cord by dorsal and not by ventral roots.
The remaining efferent fibres of the sympathetic system run in
the ventral roots, and beyond the spinal ganglia join the fibres
of the dorsal roots, with which they run for a short course,
forming the so-called spinal nerves. These give oft' branches at
different intervals, including the rami communicantes, first, the
white, later or more peripherally the grey rami. In some cases,
however, the white and grey rami arise at approximately the
same point of the spinal nerve, and unite in a common trunk.
366 PHYSIOLOGY CHAP.
The rami communicantes branch from a mixed spinal nerve, and
are themselves mixed nerves, containing both afferent and efferent
fibres.
Gaskell (1886) was the first to make an exact study of the
structure, distribution, and function of the sympathetic nerve-
fibres. As in the dog the fibres that issue from, the cells of the
spinal cord are myelinated, and as all the medullated fibres which
connect the cord with the ganglion chain run in the white rami,
he concluded that the majority of the fibres that pass from the
cord to the sympathetic must traverse the white rami. As he
further established that in the dog the white rami emerge
exclusively between the 2nd thoracic and 2nd lumbar roots, it
follows that the region of the cord between these segments is
the only part that gives origin to sympathetic fibres.
Isolated stimulation of the white rami communicantes usually
presents insuperable difficulties, because they run along with the
grey fibres. In order to demonstrate the efferent fibres which
unite the cord and the sympathetic it is usual to stimulate the
entire spinal nerve above the point of exit of the rami communi-
cantes. The results of Claude Bernard, Langley, Sherrington,
etc., fully agree with Gaskell's conclusions. Only those spinal
nerves which give origin to white rami communicantes are capable,
on artificial stimulation, of exciting the organs innervated by the
sympathetic. The cervical nerves, which have no white rami,
are incapable of any such action. Bernard (1862) found nerve-
fibres able to dilate the pupil in the 1st thoracic, and not in the
8th cervical nerve ; Sherrington (1892) observed the same on
the ape ; and Langley (1897) found in the cat, rabbit, and dog
that the 1st thoracic is the highest nerve capable of a sym-
pathetic reaction on excitation.
Analogous results were obtained from experiments on the
lower spinal nerves. Langley and Anderson (1895) obtained no
sympathetic reaction on stimulating the spinal nerves below the
lowest lumbar nerve that has a white ramus. In the dog this is
the 3rd or 4th, in the cat the 4th or 5th, in the rabbit the 5th, and
occasionally the 6th, in man probably the 2nd or 3rd lumbar nerve.
The results obtained by the degeneration method agree fully
with the excitatory results. Section of those ventral roots that
give no sympathetic reaction on stimulation causes no degeneration
in the medullated nerve-fibres of the rami communicantes. This
holds, e.g. in Langley 's demonstration on the cat (1896), for the
ventral roots of the 6th and 7th lumbar nerves, or the sacral and
coccygeal nerves. As Langley remarks, this is the more remark-
able seeing that in the cat the rami which apparently originate
in the 6th lumbar nerve may contain over 300 medullated nerve-
fibres. It follows that these fibres must originate in the higher
spinal nerves ; most of them, in fact, degenerate after transection
vi SYMPATHETIC SYSTEM 367
of the thoracic and higher lumbar nerves, which, when stimulated,
yield a sympathetic reaction (supra).
Langley concludes that the .sympathetic nerve-fibres take origin
from a limited region of the cord, and reach the white rami
couinumicantes as medullated fibres. This region is the same as
that from which the nerves to the trunk emerge, and lies between
the regions from which the nerves for the fore- and hind-limbs
originate, though overlapping them to a certain extent. The
exact limits of the sympathetic origin vary slightly in animals of
the same species.
According to recent researches (Gaskell, Mott, Sherrington,
Onuf and Collins, Anderson, Scaffidi, Hering) the spinal cells
from which the efferent sympathetic fibres spring lie in the lateral
horns, and contribute the so-called intermedia- lateral tract of
Lockhart Clarke.
If we follow the sympathetic fibres along the white rami
communicantes in the peripheral direction we meet in the first
place the lateral or vertebral ganglia. This opens up the
important question as to the relations between the fibres of spinal
origin and the elements of these ganglia, more particularly the
ganglion cells.
If the sympathetic fibres behaved like the other efferent fibres
of the body, they would pursue an uninterrupted course to the
organs which they innervate. We shall, however, find a funda-
mental difference in this respect between the two classes of nerve-
fibres, as was first established by Langley.
The two methods commonly employed to determine the peri-
pheral course of the fibres — observation of the effects of stimulation
and study of the degenerations after division — are not suit-
able for this purpose. No salient qualitative difference has been
observed in the effects of exciting the sympathetic fibres above
and below the ganglion. And the degeneration method, however
valuable elsewhere, is not applicable to the sympathetic system
because its fibres are largely non-medullated, and that method is
based on the degeneration of the rnyelin sheath (Langley).
Observation of a nerve-fibre that was medullated as far as the
ganglion, and non-niedullated afterwards, might lead to the false
induction that the fibre terminated in the ganglion, since the
process of degeneration cannot be followed beyond that point.
Nevertheless the experiments with this method have yielded
results that agree with those we are now about to consider.
Langley discovered and elaborated a third method, which is of
the utmost importance in determining the different nerve paths, and
the constitution of the sympathetic system. This is the nicotine
method, based on the property that nicotine has of paralysing the
ganglion cells of the sympathetic system, or more probably their
synaptic junctions, while leaving the fibres unaffected.
368 PHYSIOLOGY CHAP.
Hirschniann (1863) observed that nicotine has a paralysing
action on the sympathetic system ; in the rabbit the intravenous
injection of nicotine abolished the effects of stimulating the
cervical sympathetic. But the methodical application of this
discovery is due to Langley and Dickinson (1889-90). They
established the fact that stimulation of the nerve roots that give
off sympathetic fibres is totally ineffective after injecting nicotine
into the circulation of a rabbit or cat. From this they concluded
that at some point of the system nicotine blocks the transmission
of the excitations passing towards the periphery. But when the
nerve-fibres behind a ganglion (i.e. peripheral to it) are excited, all
the effects observed previous to the injection of nicotine can be
obtained, showing that the point attacked by the poison lies within
the ganglion. This conclusion is confirmed by the fact that the
local application of a dilute solution of nicotine (about 0'5 per
cent) to the ganglia produces the same effect.
The importance of this method may be illustrated by one of
Langley's experiments. Stimulation of the sympathetic immedi-
ately below the stellate ganglion produces, as is well known,
contraction of the blood-vessels as well as other changes in the
fore -limb and shoulder, and vaso-constriction, dilatation of the
pupil, and other effects in the head. After the application of a
dilute solution of nicotine to the ganglion, stimulation of the sym-
pathetic below it produces no effect in the fore -limb or shoulder,
but the usual effects in the head, while the effects of stimulation
on this side of the ganglion are unaltered. This shows that the
sympathetic fibres that supply the fore-limb are connected with
the cells of this ganglion, while those that supply the head pass
through the ganglion uninterrupted. On the other hand, if a
dilute solution of nicotine is applied to the superior cervical
ganglion and its accessory ganglion, stimulation of the sympathetic
below the stellate ganglion produces no effects in the head ; all the
fibres that pass through the stellate ganglion to supply the head
must therefore be connected with the cells of the superior cervical
ganglion or its accessory ganglion.
Langley made similar experiments on other portions of the sym-
pathetic system, and also on the related bulbar and sacral nerves,
and came to the general conclusion that every efferent fibre of the
sympathetic system which runs from the cord in a white ranius
communicans ends without exception in a vertebral (lateral) or
pre-vertebral (collateral) ganglion, where it enters into direct
relations with a ganglion cell, which, by its non-medullated
process, transmits the impulse which it receives from the medullated
fibre towards the periphery.
Langley distinguishes the nerve-fibres that end in the ganglion,
i.e. 2)re-ganglionic, from those which originate in the cells of the
ganglion itself, or post-ganylionic. Von Kolliker preferred the
vi SYMPATHETIC SYSTEM 369
names of pre-cellnlai- and post-cellular fibres, or called them viscero-
motor fibres of the first and second order. Langley objected that
" a pre-ganglionic fibre is post-cellular, in relation to the nerve-
cell from which it arises " ; while the second term is too limited,
as it does not include the secretory fibres. We therefore adopt
Langley's nomenclature.
The nicotine method is not conclusive since the action of
nicotine differs in different cases. In certain animals, as the dog,
it has hardly any effect ; in different animals of the same species,
again, or in different sympathetic regions in the same animal, it
acts differently. The splanchnic system, for instance, is more
resistent to its action than the cervical sympathetic. The paralytic
phenomena are usually preceded by phenomena of excitation. In
birds nicotine excites and causes erection of the feathers without
paralysing the ganglia.
The results of the nicotine methods were substantially confirmed
by Langendorff (1891-92), who saw that in the period immediately
preceding the animal's death stimulation of the fibres that run to
the superior cervical ganglion and the ciliary ganglion fails to
produce any effect long before the nerves that emerge from these
ganglia become inexcitable.
To sum up, we may conclude that the efferent sympathetic
fibres issuing from the cord never — like the motor fibres to the
skeletal muscles — run uninterruptedly to the organs innervated ;
they terminate, after a longer or shorter course, in a ganglion.
Some end in the first ganglion they encounter ; others, on the
contrary, pass through several ganglia before reaching their
terminal station — on their way they may send collaterals to a
great number of different cells. There is only one break in the
efferent sympathetic path, since the post-ganglionic fibres, according
to Langley, always run without further interruption to the peri-
pheral organs which they supply.
The great majority of the post-ganglionic fibres from the
ganglia of the lateral chain run back in the grey rami to the
corresponding spinal nerves, or to the next higher or lower spinal
nerve, to innervate the peripheral organs served by the sympathetic,
in the regions to which these spinal nerves are distributed (skin
system). Where the spinal nerves innervate segnaentally distinct
regions, for instance in the trunk and neck, the skin fields
supplied by the grey rami do not overlap at all, or only by about
1-2 mm. But in regions in which the spinal nerves form plexuses,
the areas innervated by the various grey rami do overlap to a large
extent, as can readily be demonstrated by producing sweat
secretion of a cat's pad by stimulating the grey rami of different
spinal nerves.
According to Langley, the stellate and the superior cervical
ganglion not only give off post-ganglionic fibres to the corre-
VOL. in 2 B
370 PHYSIOLOGY CHAP.
spending spinal nerves, \\hich then pass to the skin, but also send
fibres to the viscera (heart, lungs and their blood-vessels, salivary
glands). These two ganglia therefore give oft" visceral as well as
cutaneous fibres.
The prevertebral or peripheral ganglia supply the viscera
exclusively, and send no fibres to the spinal nerves (Langley). The
inferior cervical ganglion sends fibres to the heart : the different
ganglia oi' the solar plexus serve the abdominal viscera ; the
inferior mesenteric ganglion sends fibres to the lower part of the
gut and the urogenital system.
Langley brings out the striking fact that the ganglia of the
sympathetic system nowhere have a special arrangement according
to their function ; the cells are not divided into groups with
special functions, viz. for the contraction or the relaxation of the
unstriated muscles of the gut or arteries. The ganglia are rather
cell groups, whence the nerves run out to special regions to inner-
vate the whole of the organs controlled by the sympathetic in
that region indiscriminately.
Fig. 197 illustrates diagrammatically the origin, course, and
peripheral distribution of the fibres of the sympathetic system.
IV. Our present knowledge of the course and functional signi-
ficance of the afferent fibres of the sympathetic system is compara-
tively scanty and incomplete. Every one knows that the visceral
organs are sensitive, as violent stimuli can evoke pain, but under
normal conditions, the movements of the gut, of the iris, the secretory
processes, etc., do not affect consciousness, — in other words the
afferent impulses that ebb and now in the sympathetic system do
not usually pass the threshold of consciousness. That such im-
pulses exist may safely be affirmed on the strength of the facts
before us, for histology has demonstrated the presence of special
sensory end -organs in the viscera, particiilarly the so-called
Pacinian corpuscles, which abound, for instance, in the cat's
mesentery.
What, then, do we know of the origin and course of the
afferent sympathetic paths, and their relations to the sympathetic
ganglia ? Do all organs supplied with efferent sympathetic fibres
possess afferent fibres as well ? Do the afferent sympathetic fibres,
like the efferent, undergo a break in their passage through the
ganglia ? The answers to these important questions, which are
essential for a clear understanding of the complex structure of the
sympathetic system, will be found in Langley 's review of the
experimental work on this subject (1903).
In this connection it is useful to separate the sympathetic
system, in the narrower sense, from the two other functionally
related autonomic systems, the bulbar and the sacral. While
these two supply afferent fibres to all the peripheral organs to
which they send efferent fibres, the same only holds for the
VI
SYMPATHETIC SYSTEM
371
i G vert.
G so/
-V-£
FIG. 107. —Diagram of thf IIPI \-o\is elements wliii-h make up the sympathetic or splanchnic sy^teni.
( Ba-liuiii.) ];. 1; . >pinal con I : It. 11'., ilursal rool : • H".. ventral root ; *p.\'., spinal nerve; r.o.,
white raiuus conimunicans : /.•:.. ,,'rey ranius eommunicans ; f,'..sV., lateral chain ; G.vert., ganglia
»t' lateral chain (vertebral ganglia) ; '/..-"/., si il.-n- .^anxlioii : p. G., peripheral ganglia (t.-iminal) ;
H.nt'-a.inf., inferior mesfiitfi ic u m.^lion ; D. intestun' : Ji lilailder. The l^it Md.-nt t he figure
shows the peripheral cutaneous system (.4f., arterial walK ; Ar., erectoi mu^rl<-s of hairs;
<//•.. gland cells); the ri.u'lit .irives tin- peripheral splanchnic- system (.-If., arterial walls; dr.,
gland cells; P, Pacinian corpuscles). The afferent paths and cells are black ; the efferent pre-
ganglionic(intra-central). bin*- ; tin- ••M'-i'Mit post-ganglionic paths and cells, red.
2 B 1
372 PHYSIOLOGY CHAP.
sympathetic to a limited extent, viz. for the visceral organs. The
remainder receive their afferent fibres direct from the spinal nerves
and not from the sympathetic by the grey rarni. After section of
the grey rami Langley found that only one or two fibres, which
apparently terminated close to the vertebral column, degenerated
in the central end, and stimulation of the central end evoked no
reflex. So that if the walls of the blood-vessels in the skin and
limbs, or the plain muscle and cells, or the ducts of the glands
receive afferent fibres, these must run in the spinal nerves from
the periphery to the cord, without passing through the ganglion
chain of the sympathetic. The same is true of the head also, in
which the sympathetic sends its efferent nerves into the province
of the bulbar (autouomic) nerves ; and perhaps also for the lower
part of the gut, where in the same way it enters the region inner-
vated by the sacral system.
The afferent innervation of the viscera is quite different. The
majority of the afferent fibres of the thoracic organs, as well as of
the stomach, intestine, mesentery, etc., electrical stimulation of
which causes pain, run in the sympathetic nerve trunks and not
in the vagus. It has long been known that excitation of the
vagus below the diaphragm produces little or no pain in animals.
The afferent sympathetic fibres come from the same spinal
nerves as the efferent fibres, that is, in man from the first thoracic
to the second or third lumbar. Like the efferent fibres, they pass
through the white rami communicantes. Their peripheral course
is, however, quite different, for while the efferent paths are inter-
rupted in their passage through the ganglion, so that a pre- and a
post-ganglionic part can be distinguished in them, this, so far as
we know, is not the case for the afferent neurones. The latter,
both in their mode of origin and their subsequent peripheral
course, behave like the rest of the afferent neurones in the body,
ascending as medullated fibres to the intervertebral ganglia, where
they have their trophic centre, and from which they run in the
dorsal roots to the cord.
There is obviously no reason to suppose that the afferent fibres
belonging to the cutaneous organs, which run with the spinal
nerves, without entering the ganglia of the sympathetic chain,
behave differently from other afferent fibres. And we have direct
experimental evidence that the sympathetic afferents which
supply the visceral organs for the most part have their trophic
centre in the intervertebral ganglia. The proof is that
section of the mixed spinal nerves, immediately below the
spinal ganglion, causes all or nearly all the fibres of the white
rami to degenerate, while, on the contrary, section of the lateral
strand of the sympathetic or of the two splanchnics produces no
degeneration of the fibres of the white rami.
The same is true of the sacral nerves. In the cat, for instance,
vi SYMPATHETIC SYSTEM 373
the pelvic nerve contains upwards of 1000 afferent fibres, and after
cutting the sacral roots, Langloy ami Anderson found that only
about half a dozen of these fibres were not degenerated in the
nerve. Langley concludes that of the thousands of afferent nerve-
h'bres running from the viscera to the cord, not more than a dozen
or so have their trophic centres in the peripheral ganglia, these in
all probability being either post-gauglionic, medullated, or recurrent
afferent fibres.
V. Having discussed the origin and course of the afferent and
efferent fibres of the sympathetic system, and acquired a general
idea of its structure, there remains the most important question of
all, the significance and functions of the sympathetic ganglia.
Are we to regard these masses of ganglion cells as portions of
the cerebrospinal axis which have been displaced to the periphery,
but are still endowed with the functions of the centres ? The
earlier anatomists seemed to incline to this view when they gave
the name of cerebrum dbdominale to the solar ganglion. We have
learned that the fundamental property of the central nervous ,
system lies in its capacity for subserving reflex acts, so in order to !
decide this question we must ascertain whether the ganglia of the
sympathetic system are capable of subserving reflexes.
From the above conclusions on the course of the afferent fibres
of the sympathetic, any such possibility must a priori be excluded,
seeing that all or nearly all the afferent paths run without inter-
ruption to the spinal ganglia, and never enter into direct relations
with the sympathetic ganglia. The excitations which they trans-
mit must therefore reach the centres of the cerebrospinal axis
before they can be reflected again to the periphery.
This logical conclusion is apparently contradicted by a series
of observations which seem to show that under certain conditions
the spinal ganglia may function as true reflex centres. Cl.
Bernard (18G4) was the first to describe these phenomena. After
dividing the lingual nerve above the point at which it emerges
from the chorda tympani, and thus cutting off all connection with
the central nervous system, he artificially stimulated the peripheral
end of the lingual nerve, and saw an abundant secretion from the
submaxillary gland. We have already recorded the experiments
of Sokowin who observed that after cutting off all direct com-
munication with the spinal cord, stimulation of the central end
of the hypogastric nerve induces contraction of the bladder on
the opposite side. This observation, subsequently confirmed by
Nussbaum, Nawrocki and Skabitschewski, and others, was inter-
preted to imply that the inferior mesenteric ganglion was able to
function as a reflex centre.
Other similar facts were observed in the sympathetic nervous
system by Langley and Anderson. They saw on repeating the
experiment of Sokowin that stimulation of the hypogastric also
•2 B 2
374 PHYSIOLOGY CHAP.
produced contraction of the internal anal sphincters, ischemia of
the rectal mucosa, slight pallor of the cervix and body of the
uterus on the opposite side, etc. Laugley (assisted partly by
Anderson) obtained similar results for the pilomotor muscles and
the cutaneous blood-vessels in the thoracic and lumbar regions.
But, according to Laugley, none of these reactions, in which
excitation of the central end of a sympathetic trunk after
separation from the higher centres causes motor or secretory
effects, are true reflexes. His arguments and interpretation will
be better understood by giving a specific example :—
If the lateral strand of the sympathetic be cut in the cat
immediately above the 7th lumbar ganglion, and the central
(cranial) end stimulated, erection of the hairs with contraction of
the blood-vessels will be seen in the cutaneous regions innervated
by the 4th and 5th lumbar roots. The same effects may be
obtained many days after, when sufficient time has elapsed for the
degeneration of afferent nerve-fibres with trophic centres below the
level of section. It follows that the excitation in this case is not
conducted by fibres whose trophic centres lie in the lower portion
of the sympathetic. If the nerve -roots of the 4th or 5th
lumbar ganglion are now cut the reaction described disappears
after five days. We must, therefore, conclude that the excitation
was transmitted by pre-ganglionic efferent fibres.
This striking fact that the supposed reflex ceases on degenera-
tion of the pre-ganglionic fibres is, according to Langley, common
to all so-called " sympathetic reflexes " hitherto described.
The only possible explanation he can find is that each pre-
ganglionic fibre divides into several collaterals, and sends branches
to different ganglia. Stimulation of the central end of one of
these fibres causes an excitation that is at first propagated back-
wards along the cut fibre, and then to another twig, until it
reaches the ganglion which gives origin to the post-ganglionic
fibres that evoke the reaction. In other words, this is a similar
process to that described by Klihne in his experiments on the
conduction of motor nerve in both directions. Langley has
proposed to call this special phenomenon by the name of pseudo-
reflexes or pre-ganglionic axon reflexes. Fig. 198 is a diagram
of the course of the excitation as compared with a true reflex.
Langley utilised these pseudo- reflexes for the purpose of ex-
perimentally determining which pre-ganglionic fibres are connected
with different ganglia.
He concludes : " In my opinion none of the ' apparent ' reflexes
of the autonomic ganglia depend on a reflex mechanism similar to
that which subserves reflexes in which the central nervous system
is concerned, as in no case is an afferent fibre concerned in the
process." l
1 Langley, Ergelnissc dcr Physiologic, 1903, Jahrgang ii. Abteil. ii. p. 859.
VI
SYMPATHETIC SYSTEM
375
Another argument adduced by Schultz against the view that
the sympathetic ganglia act as true reflex centres is that stimula-
tion of both post-ganglionic and pre-ganglionic fibres has the same
effect ; and that no summation can be seen from the latter, such as
is observed in the central nervous system.
Intimately connected with the functional importance of the
sympathetic ganglia is the question whether, after separation from
the cerebrospinal axis, they are capable of sending tonic impulses
to the peripheral organs which they innervate. This point, too,
has received various answers.
The simplest method of solving it evidently consists in
severing the pre-ganglionic fibres on one side of the body, and the
post-ganglionic on the other, or in extirpating the whole ganglion.
As the results can be compared on the two sides of the body it
should be easy to deduce the influence exercised by the ganglia
&
FIG. 198. — Mechanism of action in pseudn-, or pre-ganglionic axonal, and true- reflexes. (Langley.)
A, true reflex ; B, pseudo-reflex ; .C, common diagram for A and H.
alone, apart from the cerebrospinal axis. The cervical sympathetic,
and the superior cervical ganglion which has a dilatator action on
the pupil, are well adapted for this experiment, but the results
obtained by various authors (Budge, Braunstein, Langendorff,
Kowalewsky, Schultz) disagree. According to the three first, the
pupil is contracted for some hours to one or two days after the ex-
tirpation of the cervical ganglion, which implies that the ganglion
really has a tonic dilatator action, on suppression of which the
pupil contracts. But when the influence of the ganglion is
removed without irritation no difference is observed in the width
of the pupils.
Similar researches have been made on the ciliary ganglion.
This ganglion normally exerts a tonic action on the sphincter
papillae, which is maintained reflexly by the light that impinges
on the retina, and excites the ganglion by way of the optic
nerve and mesencephalon. Section of both optic nerves in an
animal causes dilatation of the pupil ; according to Schultz and
Lewandowsky the ciliary ganglion has no influence on this, for
376 PHYSIOLOGY CHAP.
the pupil is not further dilated if the nerves to the sphincter are
cut on one side or the other of the ganglion.
Accordingly it is not possible to demonstrate that either the
superior cervical ganglion or the ciliary ganglion have any
constant tonic influence. Still less can this be proved, as Langley
says, for the other peripheral ganglia of the sympathetic. Nor
is this surprising seeing that all the known tonic influences
exerted by the central nervous system invariably take place
reflex ly, while the sympathetic ganglia are unable, as we have
seen, to subserve reflexes independently of the cerebrospinal axis.
As the sympathetic ganglia are therefore incapable of suit-
serving reflex acts and of maintaining tone apart from the central
nervous system, what is their function ? It must be confessed
that in the actual state of knowledge a complete answer is not
possible. That their function is of importance is beyond doubt,
because the animal economy has no superfluous or useless elements ;
and observations are not wanting to show that the removal of a
ganglion is by no means without injurious effects. Thus, if the
cervical sympathetic is cut on the one side, and the superior
cervical ganglion is removed on the other, the pupil on this side
gradually becomes larger than that of the other side, (Langendorff's
paradoxical dilatation of the pupil). There is no satisfactory
explanation of this phenomenon, but it shows the influence of the
ganglion.
Langley holds that the sympathetic ganglia are centres of re-
inforcement for the central nervous system, and if separated from
the latter lose their capacity for carrying out their functions. But
it must be remembered that the peripheral ganglia are capable of
surviving for years after their separation from the cerebrospinal
axis, and of reacting to poisons, or to internal secretions of the body,
as those coming from the glandular substance of the paraganglia,
which (see Vol. II. Chap. I.) seem from recent researches to have a
special affinity for these sympathetic nerve-cells.
Schultz too suggested that the ganglia may be relays, in which
excitations coining from the higher centres by way of the pre-
ganglionic fibres are reinforced.
In addition to this vague and far from well-grounded hypothesis
that the peripheral ganglia of the sympathetic are relays for re-
inforcement, another theory as to their function, based on their
special structural relations, has been put forward. Bidder and
Volkmann (1842) pointed out that the number of the nerve-fibres
issuing from a ganglion (Langley 's post-ganglionic fibres) exceeds
the number of fibres entering it (pre-ganglionic fibres) ; this also
agrees with the observation referred to above, that one pre-ganglionic
fibre may form relations with a number of peripheral ganglion
cells. These facts suggest that one function of the ganglia may be
to enlarge the field of distribution of the impulses carried towards
vi SYMPATHETIC SYSTEM 377
the periphery by the pre-ganglionic fibres, since by the ganglia
intercalated along the course of these fibres the excitation of a lew
pre-ganglionic may be transmitted to a large number of post-
ganglionic fibres.
Hofmann (1904) held that the ganglia of the sympathetic may
be co-ordinating centres in the course of the efferent paths. He
tried to support this view by the fact that stimulation of the 1st
or 2nd thoracic nerve produces a general dilatation of the whole
pupil, while excitation of the separate ciliary nerves, on the con-
trary, produces a partial dilatation of certain sectors of the pupil.
The pre-ganglionic fibres of each thoracic nerve must therefore
influence the whole iris, while the post-ganglionic fibres of the
long ciliary nerves can only innervate a portion of its musculature.
From these observations Hofmann concluded that the ganglion
cells whence the post-ganglionic fibres issue are united by com-
missural fibres so as to form a true co-ordinating centre.
Langley, however, who had concluded against these inter-
gangliar commissural fibres, obtained opposite results on repeating
Hofmann's experiments. He found that stimulation of the separate
small bundles which make up the three thoracic nerves produced
contraction of only one part of the dilatator pupillae. He further
saw that the effects of stimulating the post-ganglionic fibres as
they leave the ganglion are practically identical with those
obtained from stimulation of separate bundles of the pre-ganglionic
fibres before they enter the ganglion. In both cases excitation of
a few fibres suffices to produce maximal dilatation of the whole
pupil. But if too few fibres are excited, then in both cases either
a weak general dilatation, or a dilatation of part only of the pupil
results. From this he concluded that the spread of the pre-
ganglionic excitations is due not to co-ordination in the ganglion,
but to the fact that the post-ganglionic fibres anastomose and
mingle in the preterminal plexus.
On comparing the functions of the sympathetic ganglia with
those of any part of the central nervous system it seems from
these facts that they are most comparable with the functions of
the motor ganglion cells of the ventral horn of the cord. The
motor cells of the ventral horn have also no intracommissural
fil ires : their sole task is to transmit the impulses that reach them
from the central sensory elements by their efferent processes,
which, like the post-ganglionic fibres of the sympathetic, run
uninterruptedly to the peripheral organs which they innervate.
The pre-ganglionic fibres are comparable with the intracentral
association fibres, which bring the various centres into inter-
communication, e.g. the long pyramidal, or short intraspinal
paths, which unite the afferent with the efferent mechanisms, and
like the pre-ganglionic fibres enter into relation by means of
collaterals with a number of motor cells in the ventral horn.
378 PHYSIOLOGY CHAP.
Comparative physiology gives instances of peripheral motor
ganglia which are quite analogous to those of the sympathetic
system, e.g. the stellate ganglion of the Cephalopoda (Baglioni,
1903).
This short chapter on the functions of the sympathetic nervous
system must not be concluded without pointing out that all the
arguments which Langley and other experimental physiologists
bring forward to show that the peripheral ganglia of the sym-
pathetic are incapable of functioning as true reflex centres apply
only to the vertebral or prevertebral ganglia, and cannot be
extended to the still more peripheral nervous system, which, in
the form of ya.ngliated plexuses, is intimately related to the
muscular elements, as fche intrinsic ganglion system of the heart
and blood-vessels, Auerbach's plexus in the gastro-intestinal walls,
etc. In Chaps. IX. and X. Vol. I., and Chap. IV. Vol. II., we
reviewed the experimental facts from which it may be concluded
that these nerve organs are capable, even when separated from
the cerebrospinal axis, of provoking true reflex acts, the so-called
periplieral reflexes.
Unless we admit these peripheral reflexes and recognise their
great importance, it is impossible to explain the astonishing
results observed by Goltz and Ewald after ablation of the spinal
cord in dogs, which were discussed in the concluding paragraphs
of the last chapter (pp. 352 et seq.').
BIBLIOGRAPHY
MAYER, S. Hermann's Handbuch der Physiologic, vol. ii. Leipzig, 1879.
GASKELL. Journ. of Physiol., vol. vii., 1886.
v. Kc'JLLiKEii. Handbuch der Gewebelehre, vol. ii. Leipzig, 1896.
BOTTAZZI, F. Riv. di patol. nervosa e mentalc, 1897.
LANGLEY. Schafer's Textbook of Physiology, vol. ii., 1900.
LANGLEY. Ergebnisse des Physiol., ii., Part ii. , 1904.
LANGLEY. Brain, vol. xxvi., 1903.
LANGLEY. Journ. of Physiology, vols. xxx. and xxxi., 1905.
LEWANDOWSKY. Die Funktionen des zentralen Nervensystems. Jena, 1907.
SCHULTZ, P. Nagel's Handbuch der Physiologic, vol. iv., 1909.
These works contain numerous other references.
Recent English Literature :—
LANGLEY and OHBELLI. Observations on the Sympathetic and Sacral Autonomic
Systems of the Frog. Journ. of Physiol., 1910, xli. 450.
LANGLEY and ORBELLI. The Sympathetic Innervation of the Viscera. Journ. of
Physiol., 1910, xl. p. Ixii.
ANDERSON. Paralysis of Involuntary Muscle with Special Reference to " Para-
doxical Contraction." Journ. of Physiol., 1903, xxx. 290.
LANGLEY and MAGNUS. Movements of the Intestine before and after Degenerative
Section of the Mesenteric Nerves. Journ. of Physiol., 1905-6, xxxiii. 34.
ELLIOTT. The Innervation of the Bladder and Urethra. Journ. of Physiol.,
1906-7, xxxv. 367.
vi SYMPATHETIC SYSTEM 379
ELLIOTT. Imiervation of the Adrenal Glands. Journ. of Physiol., 1913, xlvi.
285.
ELLIOTT. Control of the Suprarenal Glands by the Splanchnic Nerves. Journ.
of Physiol., 1912, xliv. 374.
BAKKINCTOX. The Nervous Mechanism of Micturition. Quart. Journ. of Experi-
ment, Physiol., 1914, viii. 33.
BRUCE. Vasodilator Axon Reflexes. Quart. Journ. of Experiment. Physiol.,
1913, vi. 339.
EDWARDS. A Study of the Anatomy and the Vasomotor Phenomena of the
Sympathetic Nervous System of the Turtle. Amer. Journ. of Physiol.,
1914, xxxiii. 229.
CHAPTER VII
THE MEDULLA OBLONGATA AND CEREBRAL NERVES
CONTENTS. — 1. General anatomy of the brain : the medulla oblongata. 2. Motor
functions of hypoglossus nerve. 3. Vago - accessory group ; motor functions
of eleventh nerve. 4. Different functions of vagus nerve. 5. The glosso-
pliaryngeal exclusively a nerve of taste. 6. Functions of the facial and acoustic
nerves. 7. Functions of the oculoineter and trigeminal nerves. 8. The medulla
oblongata as a motor centre. 9. The medulla oblongata as the central organ
of locomotion and posture. 10. The medulla oblongata as a sensory centre.
Bibliography.
IN the lower vertebrates the spinal cord alone suffices, as we have
seen, for the regulation of all the functions of animal life. The
lowest vertebrate, Amphioxus, possesses only a spinal cord divided
into rnetameres, the higher of which, according to Kupffer'a
recent work, represent a rudimentary brain, although they have as
yet acquired no functional importance greater than or different to
the other metanieres (Steiner). In the series of Craniota, on the
contrary, the constituent parts of the brain are added to the spinal
cord by the progressive development of the organism. In man,
the highest member of the animal scale, the brain is so highly
i developed that the spinal cord seems in comparison to be merely
its appendage.
I. From the physiological point of view the brain may be
divided into parts, corresponding with those which can be dis-
tinguished at an early stage of its development.
At the head end of the primitive neural tube the first signs of
the brain appear as three dilatations, which are transformed into
vesicles, destined later to form the cerebral ventricles. The anterior
and posterior vesicles each divide into two, while the median
vesicle remains undivided. The three primary cerebral vesicles
thus form five secondary cerebral vesicles, which again give rise
from before backwards to :—
(ft) The fore-brain or prosencephalon. In the embryo this is
represented by the 1st secondary vesicle, which is originally very
small and afterwards grows out laterally, forming the hemispherical
diverticula. In the adult it is represented by the brain proper or
380
CHAP, vii THE MEDULLA OBLONGATA 381
cerebral hemispheres. Each hemisphere consists of the cortex, and
the caudate and lenticular nuclei which constitute the corpus
stria turn.
(&) The 'tween-brain or thalamencephalon. In the embryo this
is represented by the 2nd cerebral vesicle, the lateral walls of which
thicken and form the optic thalami. The third ventricle lying
between the thalami represents the 1st primary cerebral vesicle.
(c) The mid-brain or mesencephalon is formed by the thicken-
ing of the walls of the 3rd embryonic vesicle. Its ventral part
forms the cerebral peduncles, the dorsal part the optic lobes or
corpora bigemina of the lower vertebrates, the corpora quadrigemina
of mammals. The aqueduct of Sylvius by which the third and
fourth ventricles communicate is the remains of the embryonic
mesencephalic vesicle.
(d) The hind-brain or metencephalon develops from the 4th
secondary vesicle. The thickening of the ventral wall gives rise
to the pons Varolii, of the dorsal walls to the cerebellum. The
fourth ventricle or sinus rhomboidalis is the remains of the
embryonic vesicle.
(e) The medulla oblongata or myelencephalon is derived from
the 5th secondary vesicle, the ventral portion of which enlarges to
form the bulb or medulla oblongata, while the dorsal part remains
a simple epithelial layer adherent to the pia mater which covers
the sinus rhomboidalis.
In order to form an idea of the very unequal development of
the five embryonic segments in the brain of the adult, the corre-
sponding parts of Figs. 199 and 200 should be compared. The first
represents the brain of a human embryo, at two and a half months ;
the second, the adult brain. It will be seen that in the foetus the
thalamencephalon and mesencephalon are relatively very large,
while in the adult the cerebrum, and after it the cerebellum, are
largest, and the corpora quadrigemina are relatively small.
Anatomical text-books should be consulted for the external form
and internal structure of the brain : here we must confine our-
selves to such anatomical details as are necessary to the study of
its physiology.
The spinal bulb, which is the subject of the present chapter, is
the intracranial prolongation of the spinal cord, hence the name
medulla oblongata. Owing to its vital importance, and the
multiplicity of its functions, it is quite one of the most important
parts of the nervous system. The complexity of its structure
indicates the complexity of its functions.
It is conical in form, with the base above, at its junction with
the pons, and a truncated apex below, continuous with the spinal
cord. As shown by Fig. 201, the cerebral nerves from the hypo-
glossal (12th) to the abducent (6th) issue from the ventral and
lateral surfaces of the bull >.
382
PHYSIOLOGY
CHAP.
C.q.
olf
\
Fio. 199.— Sagittal section of the brain of a 2^ months' foetus. (His.) 5 diameters. Abovi'. in I lie
right, the medial surface of the left cerebral hemisphere ; the wide cavity of the third ventricle
is limited above and in front by a thin lamina ; below, the iiifuiidibulnm and pituitary body.
The thalamus occupies the lateral and upper part of the cavity ; in front and below is the
foramen of Monro ; behind the thalamus another depression which opens into the slit of the
external geniculate body ; ulf, olfactory lobe ; ?>, pituitary body ; c.q., corpus quadrigeminum ;
cli, cerebellum ; m.o., medulla oblongata.
Pio. 200.— Right half of the brain divide<l by a vertical antero-posterior section (from various sources
and from nature). (Allen Thomson.) £. 1, -2, 3, 3n., 36 are placed on convolutions of the
cerebrum ; 4, the fifth ventricle, and above it the divided corpus callosum ; 5, the third
ventricle; 5', pituitary budy; il, corpora quadrigemina and pineal sland ; +, the fourth
ventricle; 7, pons Varolii ; 8. medulla oblon^ata ; :', ceiebellum; I, the oltaetory bullj; II,
right optic nerve ; III, right 3rd nerve.
VII
THE MEDULLA OBLONGATA
383
Certain bundles of nerve-fibres from the spinal columns pass
through the medulla and pons, and on reaching the ventral part
Fir;. 201. — View from before of medulla oblongata, pous Varolii, crura cerebri. and other central
portions of the encephalon. (Allen Thomson.) Natural size. On right side the convolutions
of the central lobe or island of Reil have been left, with a small part of the anterior cerebral
convolutions ; on left side these have been removed by an incision carried between the thalamus
options and the cerebral hemisphere. I', olfactory tract cut short and lying in its groove ;
II, left optic nerve in front of the commissure; II', right optic tract; Th, cut surface
of the left thalamus options ; C, central lobe or island of Reil ; Sy, fissure of Sylviusi;
X. X. anterior perforated space; e, external, i, internal corpus geniculatum ; Ji, hypophysis
cerebri or pituitary body ; tc, tuber cinereum with infundibulum ; a, one of the corpora
albicantia ; P, cerebral peduncle or crus ; III, close to left oculomotor nerve; X, posterior
perforated space. The following letters and numbers refer to parts in connection with
the medulla oblongata and pons: PV, pons Varolii; V, greater root of 5th neive; +, lesser
or motor root; VI, 6th nerve; VII, facial; VIII, auditory nerve; IX, glossopharyngeal ;
X, pneumogastric ; XI, spinal accessory; XII, hypoglossal ; 67, suboccipital or 1st cervical
nerve ; /in. pyramid ; o, olive ; rl, ventral median fissure of spinal cord, above which the
decussation of the pyramids is represented; c<i. ventral column of cord ; r, lateral tract of
bulb continuous with i7, the lateral column of the spinal cord.
of the mid-brain divide into two large bundles — the cerebral
peduncles — which penetrate into both hemispheres. On this
384
PHYSIOLOGY
CHAP.
account many anatomists give the name brain-stem to those parts
of the medulla and pons which are the direct continuation of the
spinal cord (Fig. 202).
The pyramidal tracts — as we saw in the last chapter — decussate
FIG. 202. — View of medulla oblongata, pons Varolii, crura cerebri, and central parts of encephalon
from right side. (Allen Thomson.) The corpus striatum and thalamus options have been
preserved in connection with the central lobe and crura cerebri, while the remainder of the
cerebrum has been removed. St, upper surface of corpus striatum ; Th, back part of tha-
lamus options (pulvinar) ; (', placed on the middle of the five or six convolutions constituting
the central lobe or island of Reil, the cerebral substance being removed from its circumference ;
>'//, tissure of Sylvius, from which these convolutions radiate, and in which are seen the white
striae of the olfactory tract ; I, the olfactory tract divided and hanging down from the groove
in the convolution which lodges it; II, optic nerves a little way in front of the chiasma ;
a, right corpus albieans with tuber cinereum and infundibulum in front of it ; h, hypophysis
or pituitary body ; e, external, i, internal corpus geniculatum at back part of optic tract; P,
peduncle or crus of cerebrum; III, right oculo-motor nerve; p, pineal gland; q, corpora
quadrigemina ; IV, trochlear nerve rising from r, valve of Vieussens. The following numbers
and letters n-fer chiefly to parts in connection with medulla oblongata and pons : V, on pons
Varolii above right nervus trigeminns ; .s, superior, m, middle, in, inferior peduncle of cere-
bellum cut short; VI, 6th nerve; VII, facial nerve; VIII, auditory nerve; IX, glosso-
pharyngeal nerve ; X, opposite cut end of pneumogastric nerve ; XI, uppermost fibres of
spinal accessory nerve; XII, hypoglossal nerve ; jxi, pyramid; o, olive ; ar, arciform fibres ;
/, lestiform body; //•, tubercle of Rolando; ca, ventral, cp, dorsal, cl, lateral columns of
spinal cord ; (7, '<"/, ventral and dorsal roots of 1st cervical nerve.
in the lower part of the bulb, turning sharply ventralwards to
form the ventral or anterior pyramids. By this decussation (Figs.
203 and 204) the ventral horns become detached and separated
from the rest of the grey matter.
VII
THE MEDULLA OBLONGATA
385
The long fibres of the columns of Goll and Burdach terminate,
on reaching the lower part of the bulb, in two grey nuclei, one
lying \vithiu the column of Goll (Fig. 203 Ny}, the other externally
within the column of Burdach (Fig. 204 JVc). As the central
canal approaches the dorsal surface of the bulb, these nuclei
enlarge, till just above the decussation of the pyramids they form
the prominences termed the clavae (Fig. 205, n.g., n.c.) from the
ventral surfaces of which the arcuate fibres emerge, and turn
FIG. 203.— Transverse section of medulla <>M<nii:;it.-i in MI- the decussation of the pyramids. (Henle.
FPH, pyramidal tract; C<jn, ventral horn ; Fa', rest ,of ventral horn ; A";;, nucleus of funiculus
gracilis ; <j, substantia tft'latinosa ; XI, spinal accessory.
forwards and inwards towards the median raphe, where they cross
with those of the opposite side. So that above and dorsal to the
motor or pyramidal decussation is the sensory decussation of the
fibres of the fillet of Eeil or lemniscus niedialis, which lies im-
mediately dorsal to the pyramids.
The sensory fibres of the lateral column of the cord, which lie
closely related to Gowers' tract, do not decussate but continue to
ascend through the lateral zone of the medulla ; they pass by the
lateral nucleus of the bulb, and eventually join the mesial fillet in
the upper portion of the medulla or in the pons.
The cerebellar tracts of the lateral columns pass through the
restiform body or the inferior cerebellar peduncle, and terminate
in the cerebellar cortex.
VOT,. in 2 c
386
PHYSIOLOGY
CHAP.
The grey matter of the cord is continuous with that of the
medulla, but its shape in the cross-section is considerably altered
by the motor and sensory decussations, and by the appearance of
the fourth ventricle. This takes place in the upper half of the
bulb, where the dorsal columns separate, the grey commissure
disappears, and the central canal opens out to form the fourth
ventricle or fossa rhornboidalis (Figs. 207, 208).
FIG. 204.— Transverse section of medulla oblongata in the region of the most caudal roots of the
hypoglossus. Decussation of pyramids almost complete. (Henle.) Nc, nucleus of funiculus
cuneatus ; XII, hypoglossal. Other indications as in preceding ligure.
When the central canal opens out, the grey matter that
surrounded it in the cord comes to lie in the floor of the ventricle,
so that the part that was formerly ventro-lateral (representing the
base of the ventral horn of the cord) becomes internal or medial,
and the homologue for the dorsal horn becomes external and lateral.
The nuclei of origin and termination of the cranial nerves lie in
this grey matter, which is formed by the breaking up of the
motor and sensory columns of the spinal cord.
There are other grey nuclei in the bulb that are not represented
in the cord. After the nuclei of the columns of Goll and Burdach
already alluded to, the most important is the nucleus of the olivary
VII
THE MEDULLA OBLONGATA
387
body, which is a thin wavy lamella of grey matter, witli its opening
or hilus towards the median line ; it receives a bundle of fibres
(olivary peduncle) which, after crossing the raphe and decussating
with those from the opposite side (Fig. 206), passes to the restiform
body or the inferior cerebellar peduncle. When there is atrophy
or agenesia of one cerebellar hemisphere (Gudden), or after extirpa-
tion of one lateral half of the cerebellum (Luciani), atrophy of the
c.c
I
k. , SL^vi i^-V) v'^fflSaaeKS /
n.c.
n.am.
a,-m.f.
n.a r
FIG. 206. — Section of medulla oblongata at about
the middle of olivary body. (Schwalbe.) f.
f.l.a., anterior median fissure : //."/•., nucleus
:n riformis ; p, pyramid ; XII, bundle of
hypoglossal nerve emerging from surface; at
b it is seen coursing between the pyramid
and the olivary nucleus o ; f.a.e., extemal
arcuate fibres; n.l., nucleus lateralis ; a,
arcuate fibres running towards restiform
body, partly through substantia gelatinosa 0,
partly superficial to descending root of 5th
nerve a. V. ; X, bundle of emerging vagus
root; f.r., formatio reticularis ; C.r., em pus
restiforme, beginning tn be formed chiefly by
arciform fibres, superficial and deep; n.c.,
nucleus cuneatus ; n.fi., nucleus gracilis;
t, attachment of the ligula ; ,/X, fiuiiculus
solitarius ; »X, n\', two parts of the vagus
nucleus; mXII, hypoglossal nucleus; n.t..
nucleus of funieulus teres; n.'iiu.. nucleus
ambiguus ; r, raphe; A, continuation of
ventral column of cord ; o', u", accessory
olivary nuclei ; p.o.l., pedunculus ulivae.
olive on the opposite side is constantly seen, which proves that
there are crossed relations between the olives and the two halves
of the cerebellum. At the dorsal and medial surfaces of the
principal nucleus of the olives, there are two accessory olivary
nuclei, dorsal and medial. They probably have the same physio-
logical value and the same relations with the cerebellum as the
O
principal olivary nucleus.
FIG. 205.— Section of medulla oblongata in the
region of the superior pyramidal decussation.
(Schwalbe.) }. a.ni.f., ventral median fissure;
/.a., superficial arcuate fibres emerging
from fissure; py. pyramid; n.ur., nucleus
of arcuate fibres ; /.a.1, deep arcuate fibres,
becoming superficial ; o, lower end of olivary
nucleus ; o', accessory olivary nucleus ; n.l.,
nucleus lateralis ; f.r., formatio reticularis ;
/.a.2, arcuate fibres proceeding from formatio
reticularis ; n, substantia gelatinosa Rolandi ;
i.i.V., descending root of 5th nerve; n.c.,
nucleus cuneatus ; n.c.', nucleus cuneatus
externus ; /.c., funieulus cuneatus; 11.11.,
nucleus gracilis ;./>/., funieulus gracilis; »>. »/../.,
dorsal median fissure ; c.c., central canal,
surrounded by grey matter, in which are
H.X1, nucleus of spinal accessory. /t.XII,
nucleus of hypoglossal; x.d., superior pyra-
midal decussation.
388
PHYSIOLOGY
CHAP.
Particular mention should be made of the formatio reticularis
which occupies the entire central part of the bull) (Figs. 205 and
206) ; it consists of nerve-fibres that cross in every direction, and
form a network. The longitudinal bundles are intersected by the
transverse or arcuate fibres that traverse the raphe obliquely.
Between the fibres there is a considerable number of nerve-cells,
mostly of a large size. These, according to Deiters, send their
processes downwards, and their dendrites horizontally. The
formatio reticularis may be regarded as a special form of the
ordinary grey matter
in which the cells are
irregularly scattered,
and form, as Kolliker
says, a diffuse nucleus.
It is probable that the
main functions of the
bulb depend on these
central multipolar ele-
ments of the formatio
reticularis (Edinger) ;
the great physiological
significance of the bulb
also appears from the
fact that it contains the
nuclei of origin of most
of the efferent cerebral
nerves, as also the ter-
minal nuclei of most
of the afferent cerebral
nerves. The nuclei of
the hypoglossal, spinal
accessory, vagus, and
„ 1 „ a nil a
centre of the cerebellum ; 6, fillet at side of the crura g 1 O S S O - pliai
cerebri ; 7, lateral grooves of crura cerebri ; 8, corpora
quadrigemina.
FIG. 207.— The three pairs of cerebellar peduncles. (Sappey,
after Hirsehtield ami Leveille.) On left side the three
cerebellar peduncles have been cut short; on right side
the hemisphere has been cut obliquely to show its con-
nection with the superior and inferior peduncles. 1,
median groove of fourth ventricle ; 2, same groove at the
place where the auditory striae emerge from it to cross
the floor of the ventricle ; 3, inferior peduncle or restiform
body; 4, funiculus gracilis ; 5, superior peduncle — on
right side the dissection shows the superior and inferior
peduncles crossing each other as they pass into the white
lie entil'elv with-
n i
in the bulb; those of the
acoustic, facial, and trigeminal nerves lie partly in it, partly in the
pons ; those of the oculomotor and trochlear nerves are found
in the grey matter that surrounds the aqueduct of Sylvius in the
raid-brain.
The origins of the motor, and terminations of the sensory,
nerves are, as we have seen, systematically arranged in the spinal
cord, so that they can be identified at a glance. In the medulla,
on the contrary, all segmental regularity is lost ; the motor
and sensory elements here form irregular groups that make it
impossible from their relative positions to recognise their functions.
Of the twelve pairs of cerebral nerves the 1st and 2nd, i.e.
the Olfactory and Optic nerves, are so different from the others in
VII
THE MEDULLA OBLONGATA
389
str
to.
their origin and mode of development that it seems advisable to
study them separately, in discussing the olfactory and visual
senses. Embryologically, they are not, like the other cranial
nerves, mere prolongations from the walls of the primitive neural
tube, but vesicles that have budded out from that tube, the lumen
being subsequently obliterated.
The apparent origin of the ten remaining pairs from the 3rd
to the 12th is readily seen from a glance at the base of the
brain (Fig. 201). Their real origins lie in more or less elongated
.nuclei, which extend from the caudal end of the bulb to the
cranial end of the ventral wall of the Sylvian aqueduct. Fig.
209 gives an approximate idea of their positions.
II. The nucleus of origin of the Hypoglossus consists in a long
column of grey matter in the im-
mediate vicinity of the median line.
It begins at the level of the striae
acusticae, and ends a few millimetres
below the tip of the calamus scrip-
torius ; its total length is approxi-
mately that of the olive. Below, it
occupies a ventral position in respect
of the spinal canal (Fig. 205, n.XII) ;
above, where the spinal canal opens to
form the rhomboid sinus, it assumes a
dorsal position (Fig. 206, ?^.XII).
The nucleus of the hypoglossus
consists of a group of large ganglion
cells, enclosed in a line nervous net-
work (Fig. 210); their axis-cylinders
run ventralwards through the formatio
reticularis and emerge, as a series
of little bundles, between the olive
and the pyramids. Eoller's nucleus of small cells, as shown in
the figure, is not an accessory nucleus of the hypoglossus, but
belongs to the diffuse nucleus of the formatio reticularis.
Morphologically speaking, the hypoglossal is not a simple
nerve, but a compound one, formed by the union of at least three
ventral roots fused into a single 'trunk, as may be seen from a
study of its root filaments. In all probability it originally had
a corresponding dorsal root on the type of the spinal nerves, and
this has in fact been described as an anatomical variation in the
ox, dog, pig (C. Mayer), in the cat (Vulpian), and also in man
(Vulpian, Chiarugi). Complete or partial disappearance of dorsal
roots during phylogenesis can also be seen in the first spinal
nerves in reptiles and birds. In adult man, more often than in
other mammals, the dorsal roots of the 1st cervical nerve are
rudimentary, which, as Chiarugi rightly remarks, is a proof of the
2 C i
Flu. 20S. — Aiitei inr boundary (floor) of
fourth ve utricle. (Schafer.) Natural
size, in.s., median sulcus ; .-'/, striae
acusticae. marking Limit between
pontine part of ventricle ami medul-
lary part of calamus sr-riptorius ;
Lr., lateral recess ; i.f., inferior
(posterior) fovea ; a.c., ala cinerea ;
t.a., tri.u'onuin acustici ; s.f., superior
(anterior) fovea, close to lateial
margin of superior part of ventricle.
390
PHYSIOLOGY
CHAP.
tendency of the first segment of the trunk to become modified
according to the type of the occipital segments.
B
FIG. 200. — Diagram to show situation of chief nerve-nuclei and terminations of cranial nerves in
medulla oblongata and pons near floor of fourth ventricle. Twice the natural size. A, from
behind ; B, profile view of right half, the medulla and pons being supposed to lie transparent.
The efferent or motor nuclei are coloured red, the afferent or sensory nuclei, blue. In A the
motor nuclei are represented on right side only, the sensory on the left. Ill, IV, oculomotor
and trochlear nucleus; I'd, descending root of 5th nerve; 1's, so-railed sensory nucleus of
5th; l'a, ascending root of 5th; I'm, motor nucleus of 5th; VI, nucleus of abdncens;
VII, nucleus of facial ; ?tVII, root of facial curving round abducens nucleus ; VIII, inner or
dorsal nucleus of auditory ; VIII', outer or ventral nucleus of audit' ay ; IX. X. vm;n-<_;losso-
pharyngeal nucleus ; na, nucleus ambiguus. accessory or efferent vago-glosso-pharyngeal
nucleus; XI, nucleus of spinal accessory; XII, nucleus of hypoglossal ; XII', issuing roots
of hypoglossal.
At its origin the hypoglossal is an exclusively motor nerve.
This was recognised by Galen, who in Book VIII. cap. v. " de
VII
THE MEDULLA OBLONGATA
391
usu port in in;' classed this nerve among the " <luri ct motor i."
Boerhaave opposed this correct view aud described it as a nerve of
taste, since it is the only nerve to the tongue. Willis recognised
its motor nature, but also attributed a gustatory function to it—
a theory that was generally followed until Panizza (1834) first
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- - ffaclaif SI Rotter.
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FIG. 210.— Frontal snrtion tlirough hypoglossal nucl'-ns. (Koch.)
demonstrated experimentally that the old Galenic concept that it
is exclusively motor was accurate.
The observations of H. Mayo, Magendie, and Longet, who
stated that section or simple mechanical stimulation of the hypo-
glossal above the hyoid bone is painful, cannot be disputed. But
this sensibility is due to the fact that it anastomoses with fibres
of the vagus, of the lingual branch of the 5th nerve, and of the
three upper cerebral nerves. Cl. Bernard also found that the
392 PHYSIOLOGY CHAP.
peripheral end of the cut hypoglossal was sensitive, which he
attributed to recurrent twigs of the lingual.
Panizza gave an exhaustive description of the effects of
bilateral division of the hypoglossal in dogs, all of which depend
on the paralysis of the tongue muscles. The animal is no longer
capable of lapping up liquids with its tongue, nor of swallowing
solids after masticating them, unless the alimentary bolus drops
into the pharynx passively when the head is held up. If during
the movements of the head and jaws the tip of the tongue projects
from one or other corner of the mouth it remains there, for the
animal is incapable of drawing it back. If the tongue is bitten
during mastication, the animal gives a cry of pain, showing that
painful sensibility is unaffected. If a drop or two of concentrated
solution of quinine, which has a very bitter taste but no smell,
is dropped on the tongue, the animal shakes its head and lips
violently and makes agitated movements of mastication, as if to
get rid of an unpleasant sensation. This proves that the sense of
taste is preserved.
Electrical stimulation of the peripheral end of the divided
hypoglossal provokes contractions of all the muscles of the tongue,
except the palato-glossal and pharyngo-glossal. The fibres of the
three first cervical nerves, which anastomose with the hypoglossal,
are distributed to the thyro-hyoid and genio-hyoid muscles.
Hypoglossal paralysis in man confirms the results of experi-
ments on dogs; the effects are purely motor. In bilateral
paralysis the tongue cannot move in the mouth ; hence there are
disturbances in speaking and singing, slow mastication, and great
difficulty in swallowing owing to the incapacity of the tongue to
drive the food into the pharynx ; tactile and pain sensibility are
unaltered, but taste is slightly blunted as the tongue cannot
manipulate the food.
In unilateral hypoglossal paralysis the tongue is higher on
the paralysed than on the healthy side, owing to loss of tone in
these muscles; the tip of the tongue is deflected towards the
healthy side, which is somewhat shortened by the physiological
tone of the non-paralysed longitudinal fibres. When, on the
contrary, the tongue is protruded from the mouth, it is twisted
towards the paralysed side, owing to the one-sided action of the
genio-giossus, which from the direction of its fibres draws the
healthy half of the tongue towards the median line. In this
unilateral paralysis of the tongue, speech, mastication, and degluti-
tion are but slightly affected.
A few months after experimental transection or paralysis of
one hypoglossus, the muscular atrophy of the paralysed half of the
tongue becomes very pronounced.
III. Scarpa, Bischoff, and many others regarded the 10th
and llth nerves, i.e. the Vagus and the Spinal Accessory, as one
VII
THE MEDULLA OBLONGATA
393
single cerebral nerve, in which the vagus represents the dorsal or
sensory root, and the accessory the ventral or motor root. Certainly
the mode of origin of the vagus presents analogies with the origin
of the dorsal roots of the spinal nerves. Its primary root possesses
a ganglion (root or jugular
ganglion) which is connected
with the bulb by a series
of rootlets, and recalls the
ganglion of a dorsal spinal
root. The vagus contains
both sensory and motor
fibres. Fig. 209 shows that
it has two nuclei in the
bulb, a larger sensory
nucleus lying under the ala
cinerea, and a smaller motor
nucleus which it shares with
the 9th cerebral nerve, and
which is known as the
nucleus ambiguus.
On the other hand, we
learn from histology and
embryology that the spinal
accessory nerve arises with
ventral spinal roots. Its
internal or bulbar portion
(accessory properly so-
called) unites with the vagus
beyond the ganglion, as if
it were a motor root (Fig.
211).
Whatever the morpho-
logical value of the theory
which assumes the vagus-
accessory to be a single
nerve, it is very convenient
from the physiological point
of view to consider the llth
and 10th cerebral nerves
together.
The accessory of Willis
is an exclusively motor nerve,
which originates (Fig. 209)
from a column of cells placed dorso-laterally to the hypoglossal
nucleus, and extends into the spinal cord to the 5th cervical
segment, in which it forms part of the grey matter of the
lateral horn. From this nucleus the fibres emerge in a series
FIG. 211. — Diagiam of roots and communicating branches
of vagus ami neighbouring nerves. (Sappey, after
Hirschfeld ami Leveillr.) 1, facial nerve ; 2, glosso-
pharyngeal with pnti-n.-al ganglion ; 2', connection of
digastric branch of facial with glossopharyngeal
nerve ; a, vagus, with its t\vn ganglia ; 4. accessory;
5, hyp"gli>>-al : <\ >up>-iior cervical ganglion of sym-
pathetic ; 7, 7, loop of union between tiist two
cervical nerves; S, carotid branch of *yiiipatli>'t ii- ;
li, tympanic nerve gh>- n ntt'from petrosal ganglion: HI,
its carotid-tympanic ti laments; 11, twigtoEu.stachian
tube; 12. twig t» fen>->tia vestibuli ; 13, branch to
fenestra cochleae; 14, small, 15, large, superficial
petrosal nerve; 10. optic ganglion; 17, auricular
l.ianch of vagus ; IS. connection of accessory with
vagus ; Hi, union of liyin.igln-.sal with 1st cervical
m-iYc; 20, union between sterno-mastoirt branch of
accessory ami that of .ml <•'•] -viral nerve ; 21. pliaiyn-
geal plexus ; 22, superior laryng-eal nerve ; 23. ex-
t>-riiiil laryngi-al ; 24, mMiUe cervical ganglinii of
sympathetic.
394 PHYSIOLOGY CHAP.
of filaments along the lateral column of the cord and the bulb
below the vagus.
The external or spinal portion of the accessory, after passing
out by the jugular foramen, is directed backwards, and perforates
the sterno-mastoid and trapezius muscles, where it forms a plexus
with branches of the cervical nerves. Division of the external
branch therefore produces, not total, but only partial paralysis
of these muscles. According to Longet, if the animal, after bi-
lateral section of the external branch of the accessory, is made to
run, it soon becomes breathless, not being able, on account of the
partial paralysis of the steruo-mastoid and trapezius muscles, to
elevate the thorax sufficiently and dilate the lungs.
The internal bulbar branch of the accessory, after joining the
trunk of the vagus, sends part of its fibres into its pharnygeal
branch, while the rest anastomose with the vagus trunk, so that it
is impossible to distinguish them anatomically, and recourse must
be had to physiological tests.
Bischoff (1832) was the first who maintained, on the basis of
certain experiments on goats, that intracranial bilateral section of
all the root bundles of the spinal accessory paralyses the muscles
of the larynx, as after section of the recurrent nerves (see pp. 140
et seq.}. Longet (1841), Morgan ti (1843), confirmed the results of
Bischoff, and suggested for the bulbar part of the accessory the
name of nervus vocalis.
Cl. Bernard introduced a new method of extirpation of the
whole of the accessory nerve by pulling it out with a stout forceps
as it emerges from the jugular foramen. The operation is easy
in rabbits and cats, but difficult in adult dogs. After bilateral
destruction of this nerve the respiratory movements of the glottis
cease; according to Bernard, the glottis remains open in the
normal position, while after section of the two recurrent nerves
the glottis becomes constricted by adduction of the vocal cords,
leaving such a narrow fissure that the animal is in danger of
suffocation. Bernard concluded that the fibres which adduct the
vocal cords are distinct from the respiratory nerves which widen
the aperture of the glottis. The former come from the roots of the
accessory, the latter from the roots of the vagus, but both are
contained in the recurrent nerves.
Bernard's views were contested by Longet, Schiff, Heidenhain,
and others, who maintained that the effects on extirpating the
accessory and dividing the recurrent nerves were identical.
A. Waller (1856) and Burckhard (1867) supported the theory
that the motor fibres of the recurrent nerves come from the
accessory by the fact that in rabbits, after section of the nerve,
many or all the recurrent fibres degenerate. Although these
results all agree with Longet's theory, other experimenters bring
forward facts that are diametrically opposed to it.
vii THE MEDULLA OBLONGATA 395
In 1840 Volkinann, in collaboration with Bidder, denied, on
the strength of a number of experiments, that intracranial
stimulation of the roots of the accessory influences the laryngeal
muscles ; the opposite results obtained by Longet with galvanic
excitation of these roots were due to spread of the stimulus to
neighbouring roots of the vagus. Van Keinpen and Stilling
(1863), Navratil (1871), obtained the same negative results.
Schech (1873), on the contrary, extirpated both accessories iu
puppies, and showed by a series of laryngoscopical observations
that both vocal cords were paralysed in the cadaveric position,
with complete aphonia, as already stated by Bernard.
Eeceut work on the innervation of the larynx has been directed
to solving the two questions : (a) what difference is there between
the effects of dividing the recurrent nerves and extirpating the
accessory ? (b) do the motor nerves to the larynx come from the
accessory, the vagus, or from both these nerves {
The experiments of Wagner in Halle (1890-91) on cats, rabbits,
and dogs demonstrated that the section of a recurrent nerve at
once produces marked adduction of the corresponding vocal cord
and consequent asymmetry of the glottis, and that section of both
the recurrent nerves produces either closure of the glottis by com-
plete bilateral adduction of the vocal cords and necessitates
tracheotomy to prevent the animal from dying of asphyxia, or a
pronounced adduction of the cords which reduces the glottis to a
mere fissure. In all cases, after dividing the recurrent nerves
there is immobility of the vocal cords. This fact agrees with
Bernard's observations.
The adduction of the cords and narrowing of the glottis does
not, however, depend on the action of the muscles innervated by
the recurrent nerve, but on that of the crico- thyroid muscles
which are innervated by the superior laryngeal; in fact, it dis-
appears immediately after section of this nerve and the glottis
assumes the cadaveric position. If after section of the recurrent
nerves the glottis is observed daily, it is seen that after a few (two
to six) days the vocal cords pass from the median position of com-
plete adduction to the cadaveric position of moderate abduction,
in which they remain. These facts agree with the observations of
Longet, Schiff, and others in opposition to Bernard.
•It was more difficult to decide the question of the origin
of the motor laryngeal fibres contained in the recurrent nerves.
Grabower solved this problem by the research which he carried
out under Gad's direction (1889). Using cats, clogs, and rabbits,
he demonstrated plainly that the accessory has no part in the
motor innervation of the larynx, which is supplied by the 4th
to 6th lower rootlets of the vagus. These same lower roots of the
vagus also contain the sensory fibres for the larynx.
In his experiments on the accessory Grabower employed
396 PHYSIOLOGY CHAP.
different methods : division of the root fibres within the cranium ;
section of the nerve directly it has left the jugular foramen ;
Bernard's method of tearing the nerve out. All the experiments
carried out with the first two methods constantly gave negative
results ; the normal movements of abduction and adduction of the
vocal cords, in both respiration and phonation, are in no way altered.
On the other hand, tearing the nerve out from the jugular foramen
always produced in rabbits immobility of the vocal cords in the
cadaveric position, on the side operated on ; this depends on the
intimate anatomical relations between the accessory and the lower
root filaments of the vagus, which are torn out with the accessory.
Grabower demonstrated that in rabbits, as in cats and dogs, the
motor and sensory innervation of the larynx is due to these root-
lets of the vagus, as intracranial section of them produces motor
and sensory paralysis of the larynx on that side. When, on the
contrary, he destroyed the upper roots of the vagus, leaving the
lower roots intact, there was no disturbance of the normal functions
of the vocal cords.
Grossmann, under Exner's direction, obtained practically the
same results as Grabower, and almost simultaneously. He
specially investigated the effects of intracranial electrical excita-
tion of the single rootlets, both of the vagus and the accessory, in
rabbit. Like Grabower, he found that while stimulation of the
roots of the accessory produced no motor effect on the vocal cords,
that of the separate roots of the vagus produced strong adduction
or abduction of the corresponding vocal cord, or more or less
extensive contraction of almost all the laryngeal muscles.
Since these experimental facts have overthrown the theory
which ascribed the innervation of the larynx to the internal
branch of the accessory, the question arises if the theory of the
origin of the inhibitory cardiac fibres of the vagus from the
accessory can be retained. As we have seen (Vol. I. p. 329),
Waller (1856) based this hypothesis on his observation that the
cardiac fibres of the vagus degenerated and the inhibitory effects
of stimulation ceased after extirpating the accessory. Schiff,
Heidenhain, Vulpian, and Jolyet confirmed his results. But after
Grabower had proved that some roots of the vagus are (constantly
in rabbit) torn away with the roots of the accessory by this
method of extirpation, both these observations lost their value as
evidence. On the other hand, Gianuuzzi was unable, in rabbits
fourteen days after extirpation of the accessory, to demonstrate
complete loss of the inhibitory action of the vagus. While
Heidenhain, Vulpian, and Jolyet found acceleration of cardiac
rhythm — the necessary effect of abolishing the tonic action of the
inhibitory fibres — after destroying the accessory Schiff and Eckhard
obtained negative results.
If the bulbar roots of the accessory therefore have no influence
vii THE MEDULLA OBLONGATA 397
on the laryngeal muscles and heart, what muscles do they inner-
vate? The effects of intracranial excitation of the roots of the
accessory must be investigated in order to solve this problem.
The results obtained by Bentz and Longet from their experiments
on dogs suggest that the chief part of the pharyngeal muscles are
innervated by the accessory ; Ghauveau, on the contrary, experi-
menting with horses, only obtained a contraction from the upper
part of the first pharyngeal constrictor. More interesting, because
probably applicable to man, are the later experiments of Beevor
and Horsley (1888) upon monkeys; they obtained contraction of
the levator palati, azygos uvulae, and a large part of the muscula-
ture of the pharynx, by stimulating the roots of the accessory after
rapid extirpation of one cerebral and cerebellar hemisphere.
IV. We have already, in previous chapters of this book, referred
to the various and important functions of the Vagus or 10th nerve
(formerly misnamed " pueumogastric "). Now, therefore, we need
only summarise them, and add such experimental facts as we have
not had the opportunity of discussing elsewhere.
The branches of the vagus are of course distributed to the
head, neck, thorax, and abdomen, i.e. to many different visceral
and somatic organs (Fig. 212).
01. Bernard and others demonstrated the existence of sensory
roots, but after giving off the superior laryngeal, the proportion of
sensory fibres in the vagus trunk is small, especially in rabbits.
The inferior laryngeal consists for the most part of motor fibres.
The branches of the vagus contain fibres with various
functions : —
(a) The sensibility of the posterior part of the meninges is due
to the meningeal branch, which leaves the jugular ganglion and
accompanies the posterior branch of the meningeal artery. It is
probable that the vomiting in meningitis is reflexly produced by
the excitation of this branch of the vagus.
(&) The sensibility of the pinna and external auditory meatus
is partly supplied by the auricular branch, which also conies from
the jugular ganglion.
Irritation of the area innervated by the auricular nerve may
produce reflex vomiting and coughing, as well as reflex contraction
of the vessels of the ear (Snellen, Loven).
(c) The pharyngeal branch or branches that run from the
ganglion nodosum to form the pharyngeal plexus contain sensory
fibres for the mucous membrane of the pharynx, and motor fibres
for the three pharyngeal constrictors. Both these come into play
in deglutition and vomiting.
(d) The mucous membrane of the posterior part of the tongue,
epiglottis, and larynx (especially the part above the glottis) owes its
excessive sensibility, by which the least mechanical stimulus evokes
repeated fits of convulsive coughing, to the sensory fibres of the
398 PHYSIOLOGY CHAP.
vagus contained iu the superior laryugeal. The special sensory
and motor functions of the two laryngeal nerves, the nerves of
phonation, are dealt with in Chap. III. of this volume.
(e) The mucous membrane and plain muscle fibres of the
trachea, bronchi, and pulmonary alveoli are innervated by the
pulmonary branches of the vagus, which form the pulmonary
plexus. The important part played by the afferent and efferent
fibres of the pulmonary branches of the vagus in the innervation
of the respiratory apparatus is discussed in Vol. I. Chap. XIII.
(/) The function of the branches of the vagus that form the
cardiac plexus (inhibitory fibres, depressor nerve, etc.) in control-
ling the action of the heart has been dealt with in Vol. I. Chap. IX.
(#) The importance of the oesophageal, gastric, and caeliac
plexuses of the vagus has already been discussed in other chapters,
particularly in Chap. III. 4, 9, and 11, and IV. 7, of Vol. II. (also
in Chap. VI. of this volume).
In order to obtain a clear and accurate idea of the vital
importance of the vagi, in regulating circulation, respiration, and
digestion, we need only examine the effects of dividing them on
both sides in the neck. This study was inaugurated by Valsalva,
Morgagni (1740), Legallois (1812); continued more particularly
by Traube (1846), Cl. Bernard (1858), M. Schiff (1867); and
resumed more recently by Vanlair (1893), A. Herzen (1894),
Pawlow (1910), Nicolaides (1901), Gomez Ocaiia (1903). The
results can be briefly summarised. Section of both vagi in the
neck produces maiiy disturbances, which lead more or less rapidly
to the death of the animal. Rabbits generally die in twenty
to thirty-six hours, dogs in four to five days, fowls in six to
seven hours. In young animals death takes place in thirty to
sixty minutes after vagotoniy with symptoms of acute asphyxia,
owing to total paralysis of the laryngeal muscles, and almost
complete closure of the glottis by the passive adduction of
the vocal cords. This is due to paralysis of the posterior thyro-
arytenoid muscles which dilate the glottis, and to the fact that the
pars interarytaenoidea of the glottis is incompletely developed,
and its lips are almost entirely destitute of membrane. Legallois
found that in young animals simple section of the recurrent nerves
suffices to produce death by asphyxia ; but if, after cutting the
vagi free, pulmonary ventilation is supplied by tracheotomy, young
animals, like adults, are capable of surviving longer.
The cause of death of adult animals after bilateral section of
the vagi is very complex.
It is generally accepted that the section or ligation of one
vagus only in mammals or man is well borne in the majority of
cases, the disturbances of cardiac rhythm, respiratory rhythm, and
digestive functions being readily and speedily compensated. But
if the other vagus be simultaneously divided, the consequent trachy-
vii THE MEDULLA OBLONGATA 399
cardia and dyspnoea may become so marked that the animal dies
in a few hours, owing merely to the cessation in the control of
respiration and circulation. In fact no lesion of the internal
organs sufficient to account for death can be detected by post-
mortem examination.
In other cases the animals survive the double vagotomy for a
longer period, and death is due to hepatisation of the lungs, particu-
larly of the upper lobes, or to haemorrhage or hyperaemia with
diffuse oedema of the lungs and excess of mucus.
Like the panophthalmia after section of the trigeininal nerve
(see pp. 330 e,t seq.}, the pneumonia that follows vagotomy was long
regarded as a proof that the vagi contained fibres with a trophic
influence on the pulmonary tissue. Traube was the first who
threw doubt on this theory. He noted after double vagotomy
difficulty in swallowing, owing to the paralysis of the glottis and
oesophagus ; bits of food, saliva, or buccal mucus may consequently
get into the air passages or stick in the oesophagus and give rise
to frequent regurgitation, in which particles may penetrate through
the open glottis into the lungs, and there set up inflammation.
Again, apart from the penetration of irritating substances by
the air passages, the pulmonary lesions consequent on double
vagotomy may be explained by the following facts :—
(a) Vagotomy causes motor and sensory paralysis of the larynx,
trachea, the bronchi, and pulmonary alveoli, which, besides produc-
ing pulmonary emphysema and catarrh of the bronchi, suppresses
coughing and favours irritation, not only by foreign bodies, but
also by the mucus secreted by the bronchi.
(b) The acute dyspnoea consequent on double vagotomy
hinders the pulmonary circulation, and eventually produces
marked pulmonary congestion with haemorrhage and oedema,
even independently of the vasomotor paralysis of the lung which
was insisted on by Schiff and Herzen, but for which there is no
direct evidence.
When an interval of several months intervenes between the
section of the first and second vagus, so that the nerve first divided
is able to regenerate, dogs not infrequently survive double vagotomy
(Vanlair), but not rabbits or guinea pigs (Beaunis). It is, how-
ever, difficult to decide what length of time must elapse between
the first and second vagotomy, in order to ensure regeneration and
therefore survival. Vanlair's dogs died one to eight days after the
second vagotomy \vhen the first had been made four, six, seven
months or even a year previously. But as one dog survived
when the second vagus was cut ten months after the first, he
concluded that at least ten to twelve months were essential for
complete regeneration of the vagus first divided.
Later work has proved, however, that independently of the
regeneration of the nerve first divided, dogs may survive for
400 PHYSIOLOGY CHAP.
months when the second vagotomy follows within a few months
after the tirst (Her/en, Pawlow). Herzen succeeded in keeping
them alive by making a gastric fistula through which he fed the
vagotomised animal, so as to avoid pneumonia. Pawlow obtained
still better results by supplementing the gastric with the double
oesophageal fistula, as described in his experiments on sham
feeding (Vol. II. p. 108).
The experiments of Nicolaides, however, proved that, without
artificial help, a strong dog can survive the second vagotomy
performed immediately after the wound of the first operation has
healed. At the Physiological Congress at Turin (1901) he showed
two large, robust, and healthy dogs, in which the vagi and sym-
pathetics had been divided in the neck in two successive sittings
at a few days' interval, ten months and nineteen months earlier.
These animals were well nourished and ate well, swallowing large
pieces of meat without difficulty. Phonation,too,had been recovered.
The post-mortem examination, made before a committee of the
Congress, showed that the two vagi had not regenerated, and their
peripheral ends were seen under the microscope completely de-
generated. There is at present no evidence to explain how these
two dogs succeeded in compensating — perfectly, to all appearance
—the disturbances of respiratory and cardiac rhythm, of phonatiou,
and of the mechanical and secretory activities of digestion.
Still more marvellous is the survival of other dogs in which
double vagotomy was performed in one sitting. Among the
various cases recorded by the younger Herzen (1897) the
most interesting is that presented by Boddaert to the " Societe*
de Medecine de Gand " (1877). A strong bitch survived double
simultaneous vagotomy for three months and six days. During
the first week it seemed depressed, and vomited the milk and water
swallowed ; tachycardia and dyspnoea were marked. During
the second week improvement set in, and the animal ate freely
without vomiting. The vomiting decreased further during the
first and second months, and the animal's strength returned pro-
portionately. At the end of the second month its respiration
frequency was 14, and its pulse 132 per minute. In the last
week of its life its nutrition was again disturbed, and its strength
gradually diminished. The post-mortem examination revealed
emphysema of the upper lobes of the lung and broncho-pneumonia
of the right lower lobe, though microscopic examination failed to
discover any traces of food or buccal epithelium. The two stumps
of the vagus had united again, but it was obviously too early for
any complete regeneration.
Gomez Ocaiia, again, at the International Congress of Medicine
at Madrid (1903), presented a large strong dog which had survived
bilateral section of the vago - sympathetic in the neck, per-
formed some three months earlier. After twelve days the normal
vii THE MEDULLA OBLONGATA 401
relations between respiratory and cardiac rhythm returned. But
when shown at the Congress the animal was still incapable of
making any sounds, and vomited frequently, though well nourished
and in good spirits. After anaesthetising it with ether and
chloroform, Pawlow and Steward exposed the two nerve trunks,
which were found to be already united by cicatricial tissue, but
not regenerated, since strong electrical stimulation below the
point of section did not affect the rhythm of the heart, although
above that point it produced acceleration of the respiratory rhythm.
Both Boddaert's case and that of Gomez Ocana show that,
although important, the functions of the vagus nerves are not
absolutely indispensable to life. How the disorders of respiratory
and cardiac rhythm, of deglutition and of phonation, which neces-
sarily result from double vagotomy can be compensated remains a
mystery.
V. The Glosso-pharyugeal or 9th cerebral nerve leaves the
medulla oblongata by two roots, one of which, the motor, arises
along with the vagus from the nucleus ambiguus, the other, which
is sensory, has its terminal nucleus above that of the vagus, on the
floor of the fourth ventricle, in the ala cinerea (see Fig. 204). It
is therefore a mixed nerve, and may be regarded as a metarneric
homologue of a spinal pair. In its passage through the jugular
foramen, along with the vagus and accessory, it bears two small
ganglia, the jugular and petrosal, which have unipolar cells like
the spinal ganglia. The petrosal ganglion gives origin to the
tympanic branch (Jacobson's nerve), which connects the glosso-
pharnygeal with other nerves at the base of the skull (Fig. 211).
In passing through the neck the glosso-pharyngeal gives off a
pharyngeal branch, a tonsillar branch which also innervates the
mucous membrane of the pillars of the fauces and the soft palate,
and lingual branches that supply the circumvallate and foliate
papillae of the mucous membrane over the posterior two-thirds of
the tongue (Fig. 212).
Before the publication of Panizza's classical memoir, Experi-
mental Researches on Nerve (1834), Fodera, Mayo, and Magendie
had maintained that the sense of taste was subserved entirely by
the lingual branch of the tris;eminal. Panizza was the first who
O t?
demonstrated that the glosso-pharyngeal is the taste nerve, just
as the Lingual branch of the trigeminal is the tactile nerve, and
the hypoglossal the motor nerve, for the tongue.
Panizza's assertion of the exclusively gustatory character of
the glosso-pharyngeal was at once contested by Joh. Miiller and
his pupil Kornfeld, who believed this nerve to be of little import-
ance for taste, that sense being served by the lingual nerve, as
Magendie stated. Other physiologists came to the same conclusion
(Hall and Braughtou, Wagner, Valentin, Staniiius) on repeating
Panizza's experiments ; and others recognised the glosso-pharyngeal
VOL. Ill 2 D
402
PHYSIOLOGY
CHAP.
as the principal nerve of taste, but asserted that the lingual branch
of the trigeminal possessed the same function. Alcock (1839), in
FIG. 212.— Distribution and connections of vagus nerve on left side in neck and upper part of
thorax. (Sappey, from Hirschfeld »nd Leveille.) i. 1, vagus nerve ; 2, ganglion of its trunk ;
3, bulbar part of accessory ; 4, union of vagus with hypoglossal ; 5, phary ngeal branch of vagus ;
li, superior laryngeal nerve ; 7, external laryngeal ; 8, communication of external laryngeal
nerve with superior cardiac branch of sympathetic ; 9, recurrent or inferior laryngeal ; 10,
superior, and 11, inferior cervical cardiac branches; 12, 13, posterior pulmonary plexus; 14,
lingual branch of mandibular nerve ; 15, distal part of hypoglossal nerve ; 16, glosso-pharyngeal
nerve ; 17, accessory nerve, uniting by its inner branch with the vagus, and by its outer passing
into the sterno-mastoid muscle ; 18, 2nd, 19, 3rd and 20, 4th cervical nerves ; 21, origin of phrenic
nerve ; 22, 23, 5th, 6th, 7th, 8th cervical nerves, forming with the 1st thoracic the brachial
plexus ; 24, superior cervical ganglion of sympathetic ; 25, middle cervical ganglion ; 26, inferior
cervical ganglion united with 1st thoracic ganglion ; 27, 28, 29, 30, 2nd, 3rd, 4th, and 5th
thoracic ganglia.
%
an important series of experiments, maintained that the gustatory
fibres run in the glosso-pharyngeal and the lingual and palatine
branches of the trigeminus, and that the spheno-palatine ganglion
vii THE MEDULLA OBLONGATA 403
and the chorda tympaiii are of no importance for the sense of
taste, since they can be extirpated or divided without disturbing
it. Guzot and Cazalis (1839) concluded from their researches
that the lingual was the tactile and gustatory nerve for the anterior
three-fourths of the tongue. Eeid (1839) added that after bilateral
section of the glosso-pharyngeal the sense of taste was sufficiently
well preserved to distinguish bitter substances.
On the other hand, 01. Bernard (1843) found that after
dividing the facial nerve in the cranial cavity, or cutting the
chorda in the tympanic cavity, the taste sense is altered in the
anterior part of the tongue, because savours are less promptly
recognised than on the side not operated on.
Biffi and Morganti (1846), after unilateral section of the
chorda, failed to confirm the difference in the sense of taste on
the two halves of the tongue. It further appeared from their
experiments that the glosso-pharyngeal is the nerve of taste for
the palate, fauces, and posterior two-thirds of the tongue, while
the lingual branch serves its anterior third.
Duchenne (1860) brought evidence in favour of Bernard's
theory of the presence of taste fibres in the chorda tympani by
exciting them electrically through the external auditory meatus.
This, according to Duchenne, produces, in addition to sensory
phenomena, a metallic taste in the anterior two -thirds of the
tongue ; while electrical stimulation of the lingual nerve, on the
other hand, does not produce any sense of taste.
According to Schiff (1867), the taste fibres for the anterior
part of the tongue, which leave the bulb with the second branch
of the trigerninal, run to the spheno-palatine ganglion, thence by
the Vidian nerve to the geniculate ganglion of the facial, and
finally join the trunk of the inferior maxillary nerve, or run in
the facial to the chorda tympani, and thence to the lingual. This
theory, however, is at variance with the fact established by Alcock,
and subsequently confirmed by Prevost, that the extirpation of the
spheno-palatine ganglion produces no perceptible alteration in
taste.
Lussana and Inanzi (1862) fell back on Bernard and Duchenne's
hypothesis. They maintained that the taste fibres to the anterior
part of the tongue come from the facial or the intermediary nerve
of Wrisberg, and pass to the geniculate ganglion, thence by the
facial trunk to the chorda tympani and to the lingual. In addition
to his experimental data, Lussana based his view upon clinical
cases of paralysis of the trigeminus without loss of taste on the
anterior part of the tongue, and of paralysis of the facial nerve
or lesions of the chorda tympani in man, with abolition of taste
in this region. To this it was objected that in facial paralysis
the sense of taste disappears from the tip of the tongue only if
the lesion lies between the geniculate ganglion and the exit of the
404 PHYSIOLOGY CHAP.
chorda, and not when it involves the trunk of the nerve proximal
to the ganglion.
If the taste fibres for the anterior part of the tongue come
neither from the trigeniinal nor the facial, they may be derived
indirectly from the glosso-pharyngeal, through Jacobson's nerve,
or from the small superficial petrosal which unites the glosso-
pharyngeal with the facial. This opinion, which is well estab-
lished from the anatomical point of view, was confirmed by Carl
(1875) from accurate observations on himself. He noticed that
the left anterior part of his tongue was entirely deficient in sensi-
bility to taste. He had no affection of the facial or trigeniinal
nerves, but from early youth had suffered from left otorrhoea with
almost complete destruction of the tympanum. His left chorda
tympani seemed to be healthy, since its secretory and sensory
fibres reacted immediately to excitation. The loss of taste in the
anterior part of the tongue must be due therefore to injury to
other branches of the tympanic plexus. He concluded that the
taste fibres of this region came from the petrosal ganglion of the
glosso-pharyngeal, ran in the tympanic branch (Jacobson's nerve)
to the tympanic plexus, and thence by the small superficial petrosal
nerve, to the otic ganglion and the lingual nerve ; or partly to the
geniculate ganglion, and so by the chorda tympani to the lingual.
Von Urbantschitsch (1876) took the same view as Carl, on the
strength of his clinical observations, and held that taste fibres
run through the tympanic plexus, which is connected by Jacob-
son's nerve with the glosso-pharyngeal. This theory, while not
confirmed directly by experiment, seems the most acceptable. It
readily explains the cases of trigeminal paralysis, and those in
which the facial is injured by a lesion of the trunk above the
geniculate ganglion without noticeable disturbance of the sense of
taste. If we accept this conclusion, it confirms Panizza's original
statement that the function of taste is served exclusively by the
glosso-pharyngeal nerve.
Another question not yet fully cleared up is whether the fibres
of the glosso-pharyngeal subserve only taste, or tactile and pain
sensibility also, in the parts which they supply. Panizza held
that the intracranial mechanical stimulation of the glosso-
pharyngeal produces no sensations of pain, but others, including
Longet, deny this. On the other hand, no conclusion in favour
of the thesis that the 9th is exclusively a taste nerve can be
drawn from the fact that pain sensibility persists in the tongue,
fauces, and anterior surface of the epiglottis, after section of the
glosso-pharyngeal. Volkmann found that after this operation
irritation of the posterior part of the tongue, fauces, and pharynx
no longer cause reflex nausea and vomiting; but this might
O O ' O
obviously depend on loss of the taste sense in this region rather
than on paralysis of tactile or pain sensibility. In fact, after
vii THE MEDULLA OBLONGATA 405
section of the trigeminal, which certainly sends sensory and
tactile fibres to the isthmus of the fauces, the vomiting reflexes
persist.
Another experimental argument favours the idea that the
centripetal fibres of the 9th nerve are exclusively for taste. We
know how intimate a relation exists between gustatory sensations
and reflex salivation, and Ludwig and Eahn, on stimulating the
central end of the divided glosso-pharyngeal, obtained a more
abundant secretion of saliva than on exciting the lingual. After
bilateral section of the trigeminal nerve in the cat there is an
abundant secretion of saliva if the animal is given milk made
bitter with quinine. This does not occur on the other hand after
bilateral section of the glosso-pharyngeal. All these facts seem to
us to favour Panizza's theory.
The motor fibres of the 9th cranial nerve supply the stylo-
pharyngeal muscle and the superior constrictor of the pharynx
(Volkmann and Klein). These muscles come into action during
the deglutition reflexes, which are readily excited by stimulating
the base of the tongue towards the isthmus of the fauces.
The tympanic or Jacobson's branch, which, as we have seen,
conducts the taste fibres by an indirect path to the anterior part
of the tongue, also contains secretory fibres for the parotid gland
(Vol. II. p. 76).
VI. The 8th nerve has two roots ; one, the medial or anterior,
forms the Vestibular nerve, which pierces the bulb on the
inner side of the restiform body and ends in the nucleus in the
floor of the fourth ventricle ; the other, the lateral or posterior
branch, forms the Cochlear nerve, which passes round the resti-
form body, where it has a special nucleus (Fig. 213). These are
two distinct nerves, arising, like the dorsal roots of the spinal
pairs, from peripheral ganglia ; the first from the vestibular
ganglion or ganglion of Scarpa; the second from the spiral
ganglion of the cochlea.
According to Horbaczewsky the vestibular and cochlear nerves
run separately, from their origin, in the sheep and horse. After
section of the vestibular branch in the sheep (Biehl) and in
pigeons (Wallenberg) there is ascending degeneration of the
medial roots, which extends as far as the corresponding nucleus.
After removing the semicircular canals alone in pigeons the same
degeneration results ; but after extirpation of the cochlea only the
lateral root degenerates as far as its nucleus (Forel, Onufrowicz,
Baginski, Deganello).
The central relations of the vestibular and cochlear nerves are
still doubtful; the former is specially connected with the cere-
bellum, the latter with the cerebrum.
We shall discuss the functions of these two nerves, which
together make up the 8th cerebral nerve, in detail, in treating of
406
PHYSIOLOGY
CHAP.
To cerebellum
C.L.R
VIII M
the sense-organs ; here we need only say that the physiological
expression, acoustic nerve, applies only to the cochlear branch and
not to the whole nerve, since the vestibular branch has nothing
to do with hearing. With the earliest experiments of Flourens
(1828-30), who may be called the founder of the physiology of the
semicircular canals, the important fact became evident that all
lesions or injuries of the labyrinth are followed by specific motor
disorders without loss of hearing ; while deafness without motor
disturbance is the effect of destroying the cochlea. To prove that
the organs innervated by the vestibular nerve have quite a
different function from the
cochlea, we may cite the
facts adduced by Bateson
(1890), Kreidl (1895), Lee
(1898), and others, showing
that fishes, which have no
cochlea, have no proper
sense of hearing, i.e. they
do not react to ordinary
sound vibrations. When
fish are excited by ex-
plosions or other loud noises
this cannot be due to stimu-
lation of the labyrinth,
because approximately the
same reactions are ex-
hibited when the labyrinth
has been removed. These
sounds therefore excite the
tactile sense in fishes — the
auditory sense, as we shall
presently see, being only a
specialisation of this.
Doubt was, however, cast on these experiments on hearing in
fishes by Parker (1903). He noted that certain kinds of fish,
although devoid of cochlea, reacted to the vibration of a violin
string, or even to the note of a tuning-fork transmitted through
water, by modifications in the movements of their fins and their
respiratory rhythm. According to Parker, these reactions dis-
appear almost entirely on destroying the labyrinth.
As the two branches of the 8th nerve are analogous to two
dorsal spinal roots, so the 7th cerebral nerve — the Facial — corre-
sponds to a large ventral root, or more properly to the union of a
number of such roots. It takes origin in the lower part of the
pons from a nucleus of large ganglion cells, which lies at about
the level of the 6th nerve, and somewhat higher and more
ventral than the nucleus of the vestibular branch of the 8th
FIG. 213. — Plan of roots of acoustic nerve. (Thane.)
The outline represents a section at the junction of
the bulb with the pons : VIII.M, vestibular division ;
vm.LjCochlear division of auditorynerve; N. vin. ACC,
accessory nucleus ; G.L.R., lateral nucleus ; N.VIII.D,
dorsal nucleus ; AV, bulbo-spinal root of 5th nerve.
VII
THE MEDULLA OBLONGATA
407
nerve (Fig. 209). Its fibres first pass medialwards and dorsal-
wards to form a loop round the nucleus of the abducens, and then
turn ventral- and lateralwards to emerge at the upper end of the
bulb (Fig. 214). The facial nerve enters the internal auditory
meatus along with the 8th nerve, but separates from it at the
bottom of the meatus to enter the aqueduct of Fallopius, which
it leaves on the lower surface of the skull by the stylo-mastoid
foramen (Fig. 215). The facial is accompanied by the nervus
intermedius of Wrisberg.
During its course through the Fallopian canal the facial gives
FIG. 214.— (Left.) Plan of origins of fith and motor root of 7th cerebral nerves. (Thane, adapted
from Schwalbe.) The outline represents a transverse section of the lower part of the pons, on
to which the course of the facial nerve is projected; vi, 6th nerve; N.VI, its nucleus; vn,
facial nerve ; VILA, ascending portion of its root, supposed to be seen in optical section ;
N.VII, its nucleus : so, superior olive; AV, sensory or bulbo-spinal root of 5th nerve; VIII.M,
mesial root of acoustic nerve.
FIG. 215. — (Right.) Facial nerve in its canal, with its connecting branches, etc. (Sappey, after
Hirschfeld and Leveille.) f. The mastoid and a part of the petrous bone have been divided nearly
vertically, and the canal of the facial nerve opened in its whole extent from internal meatus to
stylo-mastoid foramen ; the Vidian canal has also been opened from the outer side ; 1, facial
nerve in first, horizontal part of its course ; 2, its second part, turning backwards ; 3, its
vertical portion ; the nerve at its exit from stylo-mastoid foramen ; 5, geniculate ganglion ;
6, large superficial petrosal nerve ; 7, spheno-palatine ganglion ; 8, small superficial petrosal
nerve; 9, chorda tympani ; 10, posterior, auricular branch cut short; 11, branch to digastric
muscle ; 12, branch to stylo-hyoid muscle ; 13, twig uniting with glosso-pharyngeal nerve
(14 and 15).
off two branches to the tympanum, the smaller of which innervates
the stapedius muscle, the other — which is the chorda tympani—
passes through the tympanic cavity and unites with the lingual
branch of the trigeminal to run partly to the sub-maxillary
ganglion, partly to the front part of the tongue. Branches run
from the geniculate ganglion through the large superficial petrosal
nerve to the spheno-palatine ganglion, from which the palatine
branches emerge to supply the muscles of the soft palate, parti-
cularly the azygos uvulae and the levator palatini. On leaving
the skull the facial sends branches to the external muscles of the
ear, the stylo-hyoid and the posterior belly of ' the digastric. At
408
PHYSIOLOGY
CHAP.
the posterior border of the masseter the facial trunk divides into
many branches, which are distributed to all the muscles of the
face, to the buccinator and the platysma inyoides (Fig. 216).
After some incomplete experiments by Bellingeri, Charles Bell
(1821) demonstrated that the facial is an exclusively motor nerve.
Fin. 216.— Superficial distribution of facial, trigeminal, and other nerves of head. (Sappey, after
Hirschfeld and LevcilK-.) f. Facial nerve— I, trunk of facial nerve after its exit from stylo-
mastoid foramen ; 2, posterior auricular branch; 3, filament of great auricular nerve uniting
with foregoing ; 4, occipital branch ; 5, auricular branch ; 6, twig to superior auricular muscle ;
7, nerve to digastric, 8, that to stylo-hyoid muscle ; 9, superior or temporo-facial division of the
nerve; 10, 11, temporal branches ; 12, malar; 13, 14, buccal; 15, inferior or cervico-facial
division of the nerve ; 16, mandibular ; 17, cervical branch. Fifth nerve— IS, auriculo-temporal
uniting with facial, giving anterior auricular and parotid branches, and ascending to temporal
region; 19, 20, supra-orbital; 21, lachrymal; 22, infra-trochlear ; 23, facial twig of zygomatic ;
•24, superficial branch of naso-ciliary ; 25, infra-orbital ; 26, buccal, uniting with branches of
facial ; 27, mental. Cervical nerves— 28, great occipital ; 29, great auricular ; 30, 31, small
occipital ; 32, superficial cervical.
He proved that after section of this nerve the sensibility of the
face was unaffected, while the facial muscles were paralysed. After
him, many other physiologists confirmed, completed, and corrected
his observations, either by experimental section or by electrical and
mechanical excitation of the trunk of the facial and its branches.
vii THE MEDULLA OBLONGATA 409
VII. The cerebral nerve which presents the strongest analogy
to a spinal pair is certainly the Trigemiual or Trifacial, with its
sensui T root connected with the semilunar or Gasserian ganglion,
and its single motor root which unites with one division of the
sensory root to form a mixed nerve.
Both the larger sensory and the smaller motor root of the
trigeminus issue from the side of the pons, where the transverse
fibres of the latter pass into the middle cerebellar peduncle (Fig.
201). The motor fibres arise in a nucleus of large cells at the
level of the upper portion of the fourth ventricle ; they are joined
by a bundle of fibres known as the descending or mesencephalic
root, which springs from a long slender column of cells in the
central grey matter of the aqueduct of Sylvius (Fig. 209). The
fibres of the sensory root run in part direct to the upper nucleus,
which lies lateral and ventral to the motor nucleus. The greater
number turn spiualwards through the pons, into the bulb and cord,
to the level of the 4th cervical segment ; they terminate among
the cells of the substantia gelatinosa Eolandi (descending or bulbo-
spinal root of the 5th nerve).
Distal to the Gasserian ganglion the trigeminus divides into
its three great branches : the ophthalmic, the superior maxillary,
and the inferior maxillary (Fig. 217).
The ophthalmic division is the smallest of the three sensory
branches which arise from the unipolar cells of the semilunar
ganglion. It supplies branches to the dura mater and tentorium,
to the eyeball and lachrymal gland, to the mucous membrane of
the nose and the conjunctiva of the eyelids, to the skin of the tip
of the nose, upper eyelid, forehead, and of the anterior portion of
the scalp. The ciliary gland is connected with it.
The superior maxillary nerve, with the sphenopalatine ganglion
(Meckel's ganglion) which is attached to it, sends branches to the
skin of the cheeks and anterior part of the temples, the lower
eyelid, the side of the nose and the upper lip ; also to the upper
teeth and mucous membrane of the nose, upper part of pharynx,
antrum of Highmore and posterior ethmoid sinuses, and the soft
palate ; finally to the tonsils, uvula, and glands of the buccal
cavity.
The inferior maxillary or mandibular nerve, which is the
largest of the three branches of the trigeminal, is a mixed nerve
owing to its union with the motor root. Its sensory branches are
distributed to the side of the head and external ear, the external
meatus, lower lip and lower part of the face. It also gives sensory
branches to the larger part of the tongue, to the mucous membrane
of the cheek, gums, and lower teeth, to the salivary glands, the
articulation of the jaw, the dura mater, the cranium, and the
mucous membrane lining the mastoid sinuses. The otic and sub-
maxillary ganglia are intimately connected with the mandibular
410
PHYSIOLOGY
CHAP.
nerve. Bellinger! gave the name of masticator nerve to the
motor root because it is distributed to the masseter, temporal, and
the two pterygoid muscles, but it also gives branches to the
mylo-hyoid, the anterior belly of the digastric, tensor palati, and
the tensor tympani.
Charles Bell (1821) first affirmed that the gaugliated root,
the 5th nerve, was the sensory nerve of the face, but it was
Fodera (1823) who first performed intracranial section of the
FIG. 217.— Diagram of brandies of fifth pair. (After a sketch by Charles Bell.) J. 1, Small root
of 5th nerve ; -2, large root, passing forwards into the semilunar ganglion ; 3, placed on the
bone above the ophthalmic nerve, which is dividing into the. frontal, lachrymal, and naso-
ciliary brandies, the latter connected with the ciliary ganglion ; 4, placed on the bone close to
foramen rotundum, marks the maxillary division, which is connected below with the splieno-
palatine ganglion, and passes forwards to the infra-orbital foramen ; 5, placed on the bone over
the foramen ovale, marks the mandibular nerve, giving off aurieulo-temporal and muscular
branches, and continued by inferior dental to lower jaw, and by lingual to tongue ; a, sub-
maxillary gland, with sub-maxillary ganglion placed above it in connection with lingual nerve ;
6, chorda tympani ; 7, facial nerve, issuing from stylo-mastoid foramen.
trigeminal on rabbits, and saw that sensibility was abolished in
all the external parts of the face, and on the mucous membrane
of the nose, cheeks, and tongue. Fodera's observations were con-
firmed and amplified by H. Mayo, Magendie, Eschricht, and
others.
Unilateral paralysis of the motor root of the trigeminus
paralyses the masticator muscles of the same side, so that in
mastication the jaw is pulled towards the paralysed side and the
teeth of the upper and lower jaws no longer meet accurately.
vii THE MEDULLA OBLONGATA 411
We have already dealt fully with the trophic disturbances of
the eye after intracranial section of the 5th nerve (Chap. V. p. 330).
The 6th cerebral nerve — the Abducens or External Oculo-
motor— is distributed solely to the external rectus muscle of the
eye. Its fibres arise from a small nucleus lying in the floor of
the fourth ventricle, immediately above the striae acusticae (Fig.
209). They issue in the form of a flattened bundle from the lower
edge of the pons, external to the pyramid. On paralysis of this
nerve the eyeball deviates inwards, owing to preponderance of the
antagonistic internal rectus muscle (convergent strabismus).
The 4th or Trochlear nerve is the smallest of the cerebral
nerves. It arises in an elongated nucleus, a prolongation of the
nucleus of the 3rd nerve, which lies in the ventral grey matter
of the aqueduct of Sylvius at the level of the posterior quadri-
geminal bodies (Fig. 209). Its fibres bend around the aqueduct
and enter the superior medullary velum where they decussate
completely with those of the opposite side. After a long intra-
crauial course this nerve is distributed exclusively to the superior
oblique muscle. After section or paralysis of the trochlear the
outward and downward rotation of the eveball is lost, so that
V
there is an upward and inward squint — in the direction of the
nose — owing to the unantagonised action of the inferior oblique
nerve.
The 3rd or Oculomotor, the largest of the motor nerves to
the eyeball, arises in a nucleus in the grey matter of the aqueduct
of Sylvius, under the anterior quadrigeminal body (Fig. 209).
After passing through the tegmentum the nerve emerges at the
inner border of the cerebral peduncle at the upper margin of the
pons (Fig. 201). It innervates all the external muscles of the
eye except the external rectus and the superior oblique, which
are supplied by the 6th or 4th nerves, that is the superior,
inferior, and internal rectus muscles, the inferior oblique and the
levator palpebrae. The branch that innervates the inferior oblique
muscle sends fibres to the ciliary ganglion ; the short ciliary
nerves which spring from this penetrate the bulb in the form of
minute filaments, and innervate the sphincter iridis and ciliary
muscle.
VIII. As a central organ the Medulla Oblongata has an
importance far greater than that of any other part of the nervous
system. When the bulb is severed by a transverse section from
the rest of the brain many important functions are preserved
which are immediately abolished when the section falls between
the bulb and the spinal cord. These are the functions of the
cerebral nerves which emerge from and have their centres in the
bulb, but in addition certain spinal functions become paralysed
because their dominating and co-ordinating centres lie in the
bulb.
412 PHYSIOLOGY CHAP.
The activity of the bulbar centres is for the most part deter-
mined by peripheral excitations that reach them by afferent paths
(reflex centres), but it is sometimes evoked by rhythmic or tonic
internal central excitations (automatic centres). Their normal
function depends on their structure and on the normal gas
exchanges kept up by circulation and respiration. Asphyxia,
rapid anaemia, rise of blood temperature from any cause excites
and finally exhausts the bulbar centres.
In discussing the visceral functions we dealt with the bulbar
centres by which they are controlled, that is, those which regulate
cardiac activity, vasomotor tone, respiratory rhythm and digestion,
consequently we need only now consider their more general
functions.
In the bulb, and intimately connected with the respiratory
centre, there is a centre which, when excited, produces general
convulsions or spasms. It has long been known that excitation
of the bulb by any kind of stimulus readily induces general con-
vulsions. Acute asphyxia, rapid ligation of the two carotids and
vertebral arteries, rapid bleeding, or compression of the veins of
the neck so as to produce a cerebral congestion all conduce to
more or less general cramps or convulsions (Kussmaul and Tenner,
Landois, Hermann, and others) by interruption of the normal
exchanges. If the interruption develops slowly the animal may
perish from asphyxia without any previous convulsions.
Kussmaul and Tenner believed that they had demonstrated
the integrity of the bulb to be an essential condition for the
appearance of general convulsions, because general convulsions no
longer set in in rabbits after separation of the bulb from the cord.
Destruction of the nceud vital of Flourens was sufficient to cause
the animal's immediate death without convulsions. If it were kept
alive by artificial respiration with the bellows, no abrupt suspension
of gas exchanges, however produced, was capable of evoking such
excitation of the spinal cord as to cause general convulsions.
Hence, they concluded, there must be a centre in the bulb whose,
excitation is indispensable for producing spread of convulsions to
all the muscles.
Freusberg (1875), however, with dogs saw that even in the
" spinal " animal the hind-limbs and tail were convulsed during
acute asphyxia, though to a less degree than when the bulb remained
connected with the cord. Baglioni and Carincola (1911) confirmed
Freusberg's observations on pigeons. They also found that these
symptoms of excitation did not occur if all the posterior roots had
previously been divided. They are not, therefore, according to
Baglioni, due solely to increased venosity of the blood, as
Freusberg surmised, but are partly due to sensory excitations
carried from the periphery by the posterior roots.
Nothnagel, by direct excitation of the rabbit's bulb, endeavoured
vii THE MEDULLA OBLONGATA 413
to ascertain the extent of the centre which gave rise to these
general convulsions. According to him it extends from the bulb
to the mid-brain. But Owsjaunikow (1875) was able by a better
method to show that in the rabbit the centre on which the spread
of the convulsions depends is seated in the lower third of the
bulb, and has an area of some 6 mm., measured from the tip of
the calamus. He evoked the spasm by reflex stimulation of the
bulb, using electrical stimulation of a hind-limb of the rabbit.
After dividing the bulb, by a transection 6 mm. above the tip
of the calamus scriptorius, it was possible with a given strength of
stimulus to provoke reflex movements in the four limbs of the
animal ; but if the section of the bulb were made lower down, the
convulsions were only partial, on one or both sides.
It seems to us probable that while in the higher vertebrates
the formatio reticularis normally presides over respiratory rhythm,
under abnormal conditions the excitation that affects it directly or
reflexly may spread to other skeletal muscles. On this theory the
collection of motor cells scattered over this region would deserve
the physiological name of general motor centre.
IX. The medulla oblougata and pons Varolii have other
important functions.
We know that the movements of locomotion are started by
voluntary impulses, but once set going they can be continued
mechanically, without attention on the part of the subject. This
shows that the organs which execute and co-ordinate the move-
ments of walking are anatomically distinct from those which
control the voluntary impulses proper. That man and many other
vertebrates do not walk from birth, and need a long education to
acquire the power, is due to the fact that at birth the nerve-
centres which subserve locomotion are incompletely developed.
Physiological experiments show that the centre for progression
lies in the bulbo-pontine region. Eedi (1810) first observed that
land tortoises can crawl after the brain has been removed. Fontana
confirmed this observation, but Eolando failed, probably because
he extirpated the bulb also. Fano repeated the experiments with
marsh tortoises in our laboratory (1884). He found that if the
entire brain, with the exception of the bulb, were destroyed these
animals began, after a short time, to exhibit unwonted locomotor
activity, either continuous or periodical, and accompanied by
movements of the neck and tail. The front limbs became more
active than the hind-limbs. The curve of progression shows that
such animals do not move in a straight line, but follow an irregular
course, and sometimes make circus movements in one or the other
direction, not apparently due to any asymmetry of lesion (Fig.
218). Locomotion is periodical, not continuous, when the tortoise
was not properly awake from its winter sleep, when much blood
had been lost at the operation, or when the central activities are
414 PHYSIOLOGY CHAP.
depressed from any cause. The number of steps in each locomotor
period bears no proportion to the successive pauses, as we noted
in the analogous phenomena of periodic cardiac and respiratory
rhythm (Vol. I. Chaps. IX. and XIII.). These and other facts for
which we have no space are evidence in favour of the fundament-
ally automatic nature of the activity of the locomotor centre.
Fano tried to localise the centre for progression in tortoises by
Owsjanuikow's method of successive sections of the bulb. He
found it was limited to its lower third, and that it thus coincides
with the localisation of the centre for general reflexes in the
FIG. 218.— Curve of progression of clecerebrated tortoise, which had a brush dipped in anilin solution
fastened to its tail. (Fano.) The curve is reduced to T£n. The arrows show the direction of
tin- movement ; the small breaks, the points at which the animal stopped.
rabbit. To us, however, it seems more probable that the lower
third of the bulb is related to the true locomotor centre as the
nceud vital of Flourens is to the true respiratory centre — this, as
we have seen, being far more extensive, and probably including
the whole region of the formatio reticularis.
The bulb is necessary not only for walking but also for active
posture, that is, the capacity for remaining in a given posture or
attitude, and resuming it when passively disturbed. In order to
take up or maintain its natural pose, the animal must throw a
number of muscles into activity. The tendency to take up a
normal attitude seems more marked in the lower than in the
higher vertebrates.
We know from the experiments of Renzi, Vulpian, and more
vii THE MEDULLA OBLONGATA 415
recently Steiner, that after excision of the whole of the brain,
except the hulb, fish can swim and maintain their normal position
with the back uppermost. The decerebrated frog, according to
the well-known experiments of Golt/, remains motionless in the
normal position ; it responds by a series of regular springs to
slight stimuli, and if thrown on to its back turns over again to
recover its normal position. Toads differ from frogs only in the
fact that after decerebration they creep about periodically like
land tortoises. The latter, according to Fano, also try to resume
the normal position when placed on their backs ; after remaining
motionless for some time the animal extends its neck, makes a
lever of its jaws against the ground, and agitates its limbs so
forcibly as to rotate its body on the long axis, which brings it
back to the normal position. Not invariably, but in most cases,
these repeated efforts attain their object : sometimes the decerebrate
tortoise turns over almost as quickly as the normal animal.
Similar facts are observed in birds and mammals. Both pigeons
and young rabbits after removal of the brain as low as the pons
stand upright and walk if stirred up. Even without external
stimuli they move about periodically like tortoises, but as soon as
the pons is destroyed or injured, standing and walking become
impossible.
The recent experiments of Baglioni (1909) have proved the
existence in the toad of true sensory centres in the dorsal region
of the upper third of the bulb, which preside over the movements
of the hind-limbs and possibly of the fore-limbs as well. He
isolated the cerebrospinal axis of the toad (Fig. 166) and found
that electrical and mechanical stimulation of this region not only
evoked movements of the limbs, but is capable, under the influence
of a local application of strychnine, of profoundly modifying the
reflex acts evoked from the hind-limbs by peripheral stimuli.
Magnini and Bartoloniei, who experimented under Baglioni's
guidance upon dogs, found that the local application of strychnine
to different parts of the dorsal surface of the bulb provoked various
effects, as hyperaesthesia and paraesthesia in the peripheral dis-
tribution of the cranial sensory nerves, particularly the fifth pair,
spontaneous muscular contractions, spasms of different muscles
of the face and neck, dyspnoea, vomiting, disturbances in gait,
erection of penis. Assuming that strychnine acts electively upon
the sensory central elements, these results are in favour of the
hypothesis that there are in the bulb, and particularly in its dorsal
part, centres which are mainly sensory. This conclusion agrees
with the other results obtained by these observers, viz. that local
application of weak solutions of carbolic acid — which stimulates
motor elements (p. 264) — produces hardly any effects.
X. Are all these highly complex automatic actions and re-
flexes of which bulbo-spinal animals are capable accompanied by
416 PHYSIOLOGY CHAP.
consciousness or not ? The same question arose with reference to
the spinal cord (pp. 335 et seq.), and the student must refer to the
arguments there discussed.
Flourens, in the first edition of his work on the Nervous System
(1823), stated that the cerebral hemispheres are the exclusive seat
of all sensation and volition, and consequently of all intellectual
activity. But it was pointed out by Cuvier, in his report to
the Academic des Sciences (1842) on Flourens' work, that this
conclusion was not a logical deduction from experimental observa-
tions, from which on the other hand it was logical to conclude that
the cerebral hemispheres are the only centres through which
sensations can reach consciousness. Flourens accordingly, in the
2nd edition of his work (1842) modified his conclusions by stating
that "1'animal qui a perdu ses lobes cerebraux n'a pas perdu sa
sensibilite ; il la conserve tout entiere. II n'a perdu que la
perception de ses sensations ; il n'a perdu que 1'intelligence."
Johannes Miiller also argued from the experiments of Flourens,
Magendie, and Desmoulins, that the medulla oblongata was " der
Sitz des Empfinduugsvermogens." He believed that the bulbo-
spinal animal has lost its memory and power of reflection and
attention, but that it continues to feel, and to react to sensations
by complex movements which are not mere reflex phenomena.
Longet pointed out in his classical treatise that the bulb and
pons contain sensitive and insensitive parts as well as motor and
non-motor parts, and affirmed that the pons, besides being the
conductor for afferent sensory impressions and voluntary motor
impulses, must be a centre of special activity, owing to the large
amount of grey matter contained in it. According to Longet it is
especially in the pons that the centre of general sensibility and
the locomotor centre are seated. In claiming for the pons a sort
of sensorium commune Longet relied particularly on the fact that
rabbits, mice, and dogs, in which the whole of the brain except the
bulbo-pontine region has been destroyed, respond by repeated
cries expressive of pain, accompanied by convulsive movements,
when a limb, tail, or ear is strongly excited. Owing to their varied
and persistent character Longet does not believe that these cries
can be simple, unconscious, reflex acts, but regards them as the
expression of pain really felt by the animal.
Vulpian came to the same conclusion after repeating and con-
firming Longet's experiments. He added an observation that
seems to us important. If the whole of the brain, including
the pons, is destroyed in a young rabbit, it responds to each
stimulus by a brief, single, invariably uniform cry, which has no
significance or expression, but resembles the sounds made by
certain toys when squeezed at one particular spot. If, on the
other hand, the pons is also left intact, the animal responds to
stimulation by one or more prolonged cries which undoubtedly
vii THE MEDULLA OBLONGATA 417
express pain, and are perfectly similar to those which the intact
rabbit makes when sharply stimulated.
These sensory phenomena observed in animals after removal of
their fore- and mid-brains are analogous to those observed in man
during chloroform narcosis. Chloroform probably abolishes the
excitability of the cerebral hemispheres before it acts upon the
lower centres of the brain ; incompletely chloroformed subjects
often utter distressing cries, contort the face as if suffering pain,
and writhe under the surgeon's knife in a way that convinces
every one present that these are no mere reflex acts, but a true
expression of pain, although on waking they declare that they
have fel t nothing. " Notre conviction profonde " (adds Longet)
" est qu'il y a eu sensation de douleur, et que son souvenir seul a fait
defaut. . . . Dansl'etat de demi-sommeil, que d'idees aussi traversent
notre cerveau et qui, 1'instant d'apres, nous echappent ! "
This theory of " ~bulbo-pontine consciousness had and still has
many opponents who would localise all psychical functions ex-
clusively to the cortex of the cerebral hemispheres, and treat
the phenomena described by Joh. Miiller, Longet, and Vulpian as
being purely unconscious reflexes. The obstacles to a clear and
incontestable solution by experiment are enormous and perhaps
insuperable.
In our opinion more value, as evidence for a sensorium in the
spinal bulb, attaches to the observations on lower vertebrates (frog,
toads, tortoises) described above. When, e.g., the tortoise thrown
on its back makes all the associated movements of the normal
animal with head and limbs in order to resume its habitual
position, it is natural to ask what can be the nature of the strong
external stimuli which are able reflexly to discharge the entire
complex of simultaneous and successive muscular actions which
the animal performs with singular dexterity, after remaining for
some time motionless with its head and limbs withdrawn into the
carapace. It seems to us clear that in this case we are in the
presence not of externally evoked reflex (Actions, but of central
instinctive actions (i.e. such as are acquired by habit and trans-
mitted by heredity) which cannot fail to be accompanied by a
certain degree of consciousness.
BIBLIOGRAPHY
Structure of Medulla Oblongata : see recent text-books of Histology of the
Nervous System, including those of EDINGEK, v. GEHUCHTEN, BEOHTEREW, and
the standard text-books of anatomy.
Physiology of the Cranial Nerves : a full bibliography will be found in the
classical text-books of Joh. MULLER, LONGET, and HERMANN (vol. ii., Special
Nerve-Physiology, by Prof. S. Meyer).
Among the most important Monographs are : —
BELL, CH. An Exposition of the Natural System of Nerves, 1824.
PANIZZA, B. Ricerche sperimentali sopra i nervi, ecc. Pavia, 1834.
VOL. Ill 2 E
418 PHYSIOLOGY CHAP, vn
MAGENDIE. Lecons sur les fonct. du syst. nerv. Paris, 1839.
BKKXARD, CL. Arch. gen. denied., 1844.
BIFFI and MORGANTI. Ann. univ. di ined. Milan, 1846.
BUDGE. Neue raed. Zeitschr., 1847.
WALLER, A. Gaz. raed. de Paris, 1856.
BERNARD, CL. Lecons sur la physiol. et la pathol. du syst. nerv. Paris, 1858.
MEISSXKR. Zcitschr. f. rat. Med., 1867.
ADAMUK. Centralbl., 1870.
LrssANA. Gazz. ined. ital., 1871.
BODDAEKT, R. Ann. de la Soc. de Mud. de Gand, 1877.
DUVAL. Soc. de Biol., 1878.
VULTIAN. Comptes rendus, 1880.
GI.EY, E. Soc. de Biol., 1887.
GROSSMAN N. Sitxungber. d. Wiener Akad., 1889.
GRAP.OWKK. Centralbl. f. Physiol., 1890.
SCHIFF. Gesamin. Beitr. z. Physiol. iii. Lansanne, 1896.
Motor and Sensory Functions of Medulla Oblongata and Bulbo-Pontine Tract,
in addition to text-books by Joh. Miiller and Longet, see :—
FLOURKXS. Kech. expi-rim. sur les propr. et les fonct. du syst. nerv. Paris,
1842.
GOLTZ. Function, d. Nervenzentr. d. Frosches. Berlin, 1863.
VULPIAN. Lemons sur la physiol. gen. et comp. du syst. nerv. Paris, 1866.
OWSJANXIKOFF. Bericlite d. K. Siichs. Gesellsch. d. Wissensch., 1875.
FRETSUKIM;. Arch. f. exper. Pathol. u. Pharniak. vol. iii., 1875.
FANO. Pubbl. del R. 1st. di studi sup. Florence, 1884.
BATESON. Journal of the Marine Biological Association of the United Kingdom,
1890.
KIJKIIM,. Piliiger's Archiv, 1895.
LEE. American Journ. of Physiol., 1898.
PARKER. Fiscli. Connn. Bull., 1903.
BAGLIONI. Zeitschr. f. allg. Physiol. ix., 1909.
MAGNIXI and BAUTOLOMEI. Arch, di fisiol. viii., 1910.
Recent English Literature : —
MATHISOX. The Effects of Asphyxia upon the Medullary Centres — Vasomotor
Centre. Journ. of Pliysiol., 1911, xlii. 283.
SOLLMANN and PiLrHEU. Reactions of the Vasomotor Centre to Section and
Stimulation of the Vagus Nerves. American Journ. of Physiol., 1912, xxx.
303.
MUSSEX. Note on the Movements of the Tongue from Stimulation of the Twelfth
Nucleus, Root, and Nerve. Brain, 1909, xxxii. 206.
GUSHING. The Taste Fibres and their Independence of the Nervus Trigeminus.
Johns Hopkins' Hosp. Bull., 1903, xiv.
DAVIES. Functions of the Trigeminal Nerve. Brain, 1907, xxx. 219.
CHAPTER VIII
THE HIND-BRAIN
CONTENTS. — 1. Anatomy of hind-brain : afferent and efferent tracts of the three
cerebellar peduncles. 2. Preliminary observations on cerebellar functions. 3. Dy-
namic phenomena immediately incident on removal of cerebellum. 4. Cerebellar
ataxy in dogs and monkeys after removal of half the cerebellum. 5. Cerebellar
ataxy after total removal of cerebellum. 6. Cerebellar ataxy. 7. The cerebellum
as the centre of equilibrium ; » 8. And the co-ordinating organ of voluntary
movements ; 9. And the organ of subconscious sensations, exercising constant
reinforcing action upon the other nerve-centres. 10. Localisation of cerebellar
functions. Bibliography.
IN discussing the medulla oblongata we were obliged to include
the poiis Varolii, which, both in its structure and its functions,
is the continuation of the bulb. Embryclogically, however, while
the medulla oblongata arises from the 5th secondary vesicle, the
pons and cerebellum originate in the 4th secondary vesicle, and
form respectively the ventral and dorsal parts of the Hind-brain
or Mesencephalon.
I. The Hind-brain is more developed in mammals than in other
classes of vertebrates. Both the ventral and the dorsal portions
present new and special formations which do not exist in lower
vertebrates — the pons properly so-called, the middle, cerebellar
peduncles, and the lateral cerebellar lobes. The pons consists
of a. nroipr'.fiincr mass nf fibvps witli an nKlimiQ omi^a/-. XTTU^U
ERRATUM
Page 419, par. 1, line 7, for " Mesencephalon" read " Metencephalon. "
nets, uesiufs a meuian ioue or vermis,
lateral lobes or cerebellar hemispheres, which do not exist, or are
rudimentary, in the lower vertebrates. This increased develop-
ment of the hind-brain in mammals is counterbalanced by a con-
siderable relative reduction in the mid-brain, in comparison with
that of the lower vertebrates.
419
420
PHYSIOLOGY
CHAP.
In transverse sections of the brain stem at the level of the
pons, the ventral part, or pons proper, must be distinguished from
the dorsal part or tegmentum, which is the continuation of the
bulb. The former contains the transverse fibres which pass to the
middle peduncles ; the most superficial lie over the pyramids, the
deeper pass partly between the pyramidal fibres, partly dorsal to
them ; reaching the middle line they decussate with the fibres from
the other side (Fig. 219). The grey matter of the pous contains
a.V
O.S.
FIG. 219.--Sec.tion across lower part of pons. (Stilling and Sehwalbe.) jii/, pyramidal bundles con-
tinued up from medulla ; po, transverse fibres of pons passing from middle cms of cerebellum,
before (/in-) and behind (/'O1) chief pyramidal bundles ; t, deeper transverse fibres, constituting
trapezium ; the grey matter between the transverse fibres is not represented in this or in the
following figures ; r, raphe ; o.s., superior olivary nucleus ; n.V, bundles of ascending roots of
5th nerve, enclosed by prolongation of grey substance of Rolando; VI, 6th nerve; TO. VI,
its nucleus; VII, facial nerve; Vll.a, ascending portion of facial root; TO. VII, its nucleus;
VIII, superior root of auditory nerve ; TO. VIII, part of nucleus of Deiters ; V, section of vein.
small multipolar nerve-cells scattered among the superficial and
deeper bundles (Fig. 220).
The dorsal part of the pons represents the continuation of the
formatio reticularis and grey matter of the bulb, but it also con-
tains a more definite and compact mass of grey matter, known as
the superior olivary nucleus, as well as the nuclei of the 5th, 6th,
and 7th cerebral nerves.
The cerebellum or dorsal part of the mesencephalon occupies
the posterior fossa of the skull : its median portion forms the roof of
the fourth ventricle (Fig. 221). Between the two superior peduncles
this roof is completed by the velum medullare superius, or valve
VIII
THE HTND-BEAIN
421
of Vieussens, which extends to the corpora quadrigemina and the
roof of the aqueduct of Sylvius (Fig. 200).
Most anatomists distinguish a, verm is or median lobe and two
hemispheres, or lateral lobes, in the cerebellum. Bolk (1902),
however, on the basis of accurate investigation and patient phylo-
genetic comparison of many mammalian cerebella, demonstrated
that this organ is divided not in the sagittal but in the transverse
V.IV.
* • '• -• -; -'.- . •• :' Pf£*$?' -^k '"•*-<'# I/ /y 'I'^vf ''•*•-'*>-' • ~ ' *^-»-z£J"*^aii?*~" * i ~'
1 ' •" • . • ' '4-KaT** ir~jBrt~jf?7 j's~'''&'*^'j' Tt -~V '*I^T% • •• ' ' ' V "'^ v*TjF "" *
:^ fPS-W^ciSTS^:'-:.xJ^3^f;>-, r,
Si' ">5;;» -.• --Ci«^. •;:- -^^ScrsiK-
FIG. 220. - Transverse section of pons Varolii through origin of auditory nerve. (Schafer.) From a
photograph. Magnified about -1 diameters. J". 1 V., fourth ventricle ; c, white matter of cerebelhir
hemisphere ; r.il., corpus dentatvim cerebelli ; //., flocculus ; c.r., corpus restiforme ; R., Roller's
ascending auditory bundle; D, Deiters' nucleus ; VIII, issuing root of auditory nerve ; VIII. d.,
dorsal nucleus; VIII. v., ventral (accessory) nucleus of auditory ; it.ti:, small-celled nucleus
traversed by fibres of trapezium ; tr., trapezium ; /., fillet ; ii.l.li., posterior longitudinal bundle ;
./'.;•., formatio n-ticularis ; ('.a., ascending root of .5th; s.g., substantia gelatinosa ; s.o., upper
olive; VII., issuing root of facial; H.V1I., nucleus of facial; VI., root bundles of abducens ;
py., pyramid bundles; n.p., nuclei pontis.
direction. According to the Dutch anatomist, the cerebellum of
mammalia presents one uniform type ; despite any variations from
this, there is always a deep primary sulcus which usually extends
to the white matter, and divides the cerebellum into an anterior
and a posterior part (Fig. 222).
In man the anterior lobe of Bolk includes the so-called vermis
superior (lobulis centralis and lingula), the monticulus and the
lobus quadratus anterior. This anterior lobe forms a single un-
paired median organ.
422
PHYSIOLOGY
OHAP.
The posterior lobe of Bolk is larger and includes all the rest of
the cerebellum. It can, however, be subdivided into four lobules,
two median and two lateral.
(a) The first of the two median lobules, called lobulus simplex
by Bolk, becomes so wide in man that anatomists had distinguished
in it a declivium or median part, and the lobus quadratus superior
or lateral parts. To this Bolk restores the character of a single
median unpaired lobule.
(&) The second of the median lobules is the lobulus medianus
posterior of Bolk, the so-called verjnis inferior. The single, un-
paired character of this organ is admitted by every one.
(c) The two lateral lobules were termed lobuli complicate by
12
lobe ; 7, pons Varolii ; 8, middle peduncle of cerebellum ; 9, medulla oblongata ; 10, 11, anti-run-
part of great horizontal fissure ; 1'2, 13, smaller and larger roots of fifth pair of nerves ; 14, sixth
pair; 15, facial nerve; 16, pars intermedia; 17, auditory nerve; IS, glosso-pharyngeal ; 19,
pneumogastric ; 20, spinal accessory ; 21, hypoglossal nerve.
Bolk, and include the remainder of the cerebellum. While the
other lobes develop in an antero-posterior line, so that the inter-
lamellar sulci all have a transverse or oblique direction, the
development in the lobuli complicati follows a twisted or spiral
line, and the interlamellary sulci consequently run in irregular and
even opposite directions. The schematic type which Bolk gives
for this lobule results from two loops back to back joined by an
isthmus that runs parallel with the median line. In the human
cerebellum there is an enormous development of the parts con-
tained in the first loop, which includes the lobuli semilunaris,
gracilis, and cuneiformis of the anatomists ; the isthmus is formed
by the tonsils ; the whole of the rest, which is rudimentary, consists
of the flocculus.
This new morphological and phylogenetic view of the cere-
viii THE HTND-BEAIN 423
belluin is interesting, because it is reasonable, — as Bolk showed in
V.cac.
B
Fir,. 222.— Views of upper (A) and lower (B) surfaces of Imman cerebellum. Natural size. From
photographs. (Sriiafer.) The plate also shows Bolk's divisions into lobules, in different colours.
The light yellow is Bolk's anterior lobe ; dark yellow, simple median lobule on upper surface,
and posterior median lobule on lower surface of cerebellum; the red shows the two lateral
lobules which Bolk calls .•um^oinc/— of which the deeper red tonsils and flocculi also form
part. In A : ?.c., lobulus centralis ; n.l.c., ala lobuli centralis ; m, culmen monticuli ; J.m.,
lobus culminis ; d., clivus ; ?.<•?., lobus clivi ; l.cac., lobus cacuminis ; l.t., lobus tuberis ; s.p.-c.,
suk-iis post-centralis ; s.pr.-d., sulcus pre-clivalis ; s.p.-d., sulcus post-clivalis ; f.li.,f.h., lissura
horizontalis magna. In B: I, lingula ; I.e., lobus centralis ; a.l.c., all lobuli centralis; s.p.-c.,
sulcus post-centralis ; r.rn.s., velum rnedullare superius ; p.s.c., pedunculus cerebelli superior ;
p.c., pedunculi cerebelli medius et inferior ; n., nodulus ; r.m.i., velum medullare inferius ; p.fl.,
pedunculus flocculi; rf., flocculus ; «., uvula; n/n., amygdala; >py, pyramis ; l.lii:, lobus
biventralis; 1. 1:, tuber valvulae sen posticum; l.t., lobus postero-inferior ; /.f/)'.1, lobulus
niacilis anterior : ?."/.-, lobulus -lacilis ]«.st>-i ior ; s.pr.-gr,, sulcus pre-gracilis ; s.i.-qr., suleus
intra-gracilis : s.p.-gr., sulcus post-gracilis ; f.li., tissura horizontalis ma-na. The vallecula has
been somewhat opened out to display the parts of the lower worm.
his masterly work on the Mammalian Cerebellum, 1904-6, — by
2 E i
424
PHYSIOLOGY
CHAP.
correlating the relative development of different lobes in different
mammals with the degree of functional development of certain
groups of muscles, to argue in favour of a physiological connection
—a functional relation --between the central and peripheral
variations. Bolk's ingenious inductions, taken as the starting-
point of new physiological researches, have led to certain positive
results in regard to functional localisation in the different
cerebellar lobules.
As regards the structure of the cerebellum, we must confine
ourselves to certain general statements, referring for minute
culm-en
Sulfuspost- centr-alis
loiuLus cert-trellis
li.ngu.la.
•
;<;-- ' ^RgSO?
l^^r^^^sA^
ventricu.lu.3
IV
Fie.. LJi'3. — Median section of vermis. Light yellow, Bolk's anterior lobe ; dark yellow,
the two median lobules.
details to recent text-books on the anatomy and histology of the
nervous system.
If a section is made through the cerebellum in the median
sagittal line, it is seen to consist of a central white substance
covered by a uniform layer of grey cortical matter (Fig. 224). The
lamellar or foliated aspect of the surface of the cerebellum is pro-
duced by the terminal branches of the so-called " arbor vitae,"
covered with grey matter.
Each lamella shows in section a central zone, of white matter,
and a cortex of grey matter consisting of two layers, one of which
is termed granular because it contains small nerve-cells which
look like granules with low magnification, the other molecular
owing to its appearance under the microscope. Between the two
layers there is a layer of large nerve-cells, known as the cells or
corpuscles of Purkinje (Fig. 224).
VIII
THE HIND-BKAIN
425
The medulluted fibres of the white matter appear continuous
with the three peduncles which unite the cerebellum with the
brain -stem.
Lying in the white matter, near the roof of the fourth
ventricle, are. four masses or
nuclei of grey matter of
different sizes, which are
symmetrically arranged on
either side of the organ.
The most medial is known
as the nucleus of the roof
(nucleus fastigii) ; the most
lateral is the nucleus den-
tatus, also known as the
corpus olivare cerebelli, from b
its great resemblance to the
olive of the bull.). The two
small nuclei, respectively the
nucleus giobosus and emboli-
formis, are accessory nuclei
lying between the two pre-
ceding (Fig. 225).
From the physiological
point of view it is important
to form a clear picture of the
relations of the cerebellum
to the rest of the nervous
system, by identifying the
afferent and efferent paths
that pass through the three
cerebellar peduncles.
The fibres of the superior
peduncles (crura ad cere-
brum) arise for the most
part in the cells of the
dentate nuclei ; they run
forwards to the mesence-
phalon, decussate almost ,
' Fio. 224.— Section of cortex of cerebellum. (Sankey.)
Completely beneath the COr- a, pia mater ;&, external layer ;e, layer of corpuscles
Jf • • j of Purkinje ; d, inner or granule layer ; e, white
pora quadrigemma, and ter- matter.
inmate in the nuclei rubri
of Stilling, which lie in the tegmentum of the mid-brain near
the regio subthalamica. From the cells of the red nuclei fibres
run out to the optic thalami.
In addition to these efferent fibres the superior cerebellar
peduncles also contain a few afferent fibres (Mingazzini), which
probably arise in the thalami, pass through the red nuclei without
426
PHYSIOLOGY
CHAP.
interruption, and decussate on the way to the superior cerebellar
peduncles.
After complete extirpation of one-half of the cerebellum —
which we first performed successfully on dogs — March! found by
his method almost total degeneration of the red nucleus on the
opposite side and only partial degeneration of the red nucleus on
the same side (Fig. 226). The decussation of the superior central
peduncles is therefore not complete, though nearly so.
According to the Dejerines, the red nucleus does not degenerate
r?,. globe sits
pll-iS ' - vvlfi'
FIG. 225.— Section across the cerebellum and medulla' oblongata, showing position of nuclei in
white matter of cerebellum. (Stilling.) J. fl.rf., nucleus dentatus cerebelli ; s, band of
fibres ilri -ivrd ,from restiform body, partly covering dentate nucleus ; s.c.ji., commencement
i if superior cerebellar peduncle ; com', com", eommissural fibres crossing in median white matter.
with unilateral cerebellar lesions that involve the cerebellar cortex
only, and not the dentate nuclei, which proves the origin in these
nuclei of the fibres that run to the red nuclei.
Marchi's method clearly shows that the superior cerebellar
peduncle is largely composed of efferent fibres of cerebellar origin.
According to Eamon y Cajal, the axis-cylinders of the cells of
the dentate nucleus can be followed into this peduncle, which
also receives a few fibres from the cerebellar cortex. As the
fibres emerge from the cerebellum many of them give off large
collateral branches, which form a descending bundle that passes
through the substantia reticularis grisea, and gives fibres to the
nuclei of the cerebral nerves (Cajal).
VIII
THE HIND-BEAIN
427
The middle peduncles (crura ad ponteni) are largely composed
of afferent fibres to the cerebellum, which arise in the cells of the
pontine nuclei. They cross in the median line of the pons and
terminate in the cerebellar cortex of the opposite side. Since the
cells of these crossed ponto-cerebellar fibres are in relation with
the final ramifications of the fibres which have their origin in the
cortex of the frontal and temporal lobes of the brain, it follows
that each cerebral hemisphere is indirectly connected with the
opposite half of the cerebellum on the opposite side by these fronto-
temporo-pontine paths (Fig. 227, «, &).
According to Eamon y Cajal, efferent fibres from Purkinje's cells
/.;• {I;!.; ^X ' 4
.' > i.,-:.t. ' • . *f -. .- •'
FIG. 226. — Sections of dog's mesencephalon, showing degenerations following extirpation of right
half of cerebellum. (Marchi's method.) A, section at level of nucleus of origin of 3rd nerves ;
a, a, red nuclei of Stilling, that to the left much degenerated, that to the right less so ; b,
fibres of 3rd nerves degenerated on the side of the extirpation ; d, posterior longitudinal
bundle terminating in the nucleus of the 3rd nerves ; e, pes pedunculi ; /, inferior bundle of fillet
of Reil coursing to corpora quadrigemina. B, corresponding section at superior- corpora quadri-
gcmina ; n, «, red nuclei, as above; b, posterior longitudinal bundle; c, optic tract partially
degenerated on the side of the extirpation ; d, inferior bundle of fillet of Reil running near the
corpora geniculata to the corpora qnadrigemina ; e, pes of cerebral peduncle.
also run through the middle peduncles, cross in the pons, and then
descend in the lateral column of the cord to terminate round the
motor cells of the ventral horn. According to Marchi and Mingazzini,
some of these efferent fibres run to the pontine nuclei, thence
fibres arise which ascend vertically through the cerebral peduncle
on the opposite side. By these indirect cerebello-cerebral paths
the cerebellum can influence the cerebrum on the opposite side
(Fig. 227, c, d). Finally, according to Bechterew and Mingazzini,
fibres of the middle peduncle, which arise in the cerebellar cortex,
cross the raphe of the pons, run up its sides, and end in the
formatio reticularis (Fig. 227, e,f).
The inferior peduncles (crura ad medullam) contain both
afferent and efferent fibres, the former predominating. The fibres
428
PHYSIOLOGY
CHAP.
ascending from the cord must be distinguished from those which
take origin in the medulla oblongata.
The "afferent spinal fibres run in the lateral columns of the.
cord ; these are the direct cerebellar tracts of Flechsig, which
ascend through the restiform body to the vermis of the cerebellum.
The fibres of these bundles spring for the most part from the cells
of Clarke's column on the same side, and as the collaterals of the
posterior roots run to these cells there is thus au indirect connec-
tion between the dorsal roots and the cerebellum. But, according
to Edinger, Obersteiner, and Thomas, there is also a direct connec-
tion between the posterior roots and the cerebellum, as certain
fibres of the posterior column turn dorsalwards and lateralwards as
external posterior arcuate fibres, and join the restiform body, to
run with the fibres of Flechsig's bundle to the vermis.
From certain observa-
tions of Ferrier and
Turner it seems probable
that the nuclei of the
posterior columns also
send fibres to the cere-
bellum via the restiform
body, but this has not yet
been proved.
A larger proportion of
the fibres of the inferior
cerebellar peduncle come
from the bulb than from
the cord. Atrophy of
the inferior olive, associ-
ated with atrophy of the opposite side of the cerebellum, — as first
described by Meynert and confirmed by subsequent observers-
shows that there is a crossed relation between the inferior olive
and the cerebellum, by way of fibres that ascend through the
restiform body. Other fibres spring from the cerebellar cortex
and descend to the olive of the opposite side ; in fact, after uni-
lateral cerebellar extirpation there is a considerable atrophy of the
inferior olive of the opposite side (Fig. 228, a, &).
According to Edinger, a bundle of afferent fibres, which he
terms the direct sensory cerebellar tract, takes origin in the main
nucleus of the acusticus, the nucleus of Deiters, and the nucleus of
Bechterew, and ascends through the internal segment of the
inferior cerebellar peduncle to the cerebellum, where it ends in
the nucleus fastigii and the nucleus globosus (Fig. 229). This
bundle is joined by fibres from the trigemiiius, vagus and accessory
nuclei. As the fibres of the vestibular nerve terminate in the
vestibular nucleus there is thus an indiiect relation between the
semicircular canals and these internal nuclei of the cerebellum.
Fio. 227.— Plan of afferent and efferent paths that run
through the middle cerebellar peduncle to establish
reciprocal relations between the cerebellum and the.
cerebrum. (Mingaxzini.)
VIII
THE HIND-BRAIN
429
The efferent cerebello-spinal fibres that leave by the lower
cerebral peduncle are represented by the direct ventro-lateral
bundle of Marchi, the course of
which has been well illustrated
by Thomas. The fibres of this
bundle pass through the inner
segment of the corpus restiforme
between the cells of Bechterew's
Fin. 228. — Plan of olivo-cerebellar paths, a;
cerebello - olivary, b ; cerebello - spinal,
crossed, <; <l, and direct, e, which accompany
the pyramidal tracts. (Mingazzini.)
Fie. 229.— Plan of direct sensory cerebellar
paths (Edinger), running froTii Deiters' D,
and Bechterew's 7J, nucleus of vestibularis v,
to nucleus fastigii t, and nucleus globosus g.
and Deiters' nuclei, run through the formatio reticularis in the
neighbourhood of the inferior olive, and pass into the ventro-
lateral marginal zone of the cord without decussation. After
unilateral extirpation of the cerebellum there is descending
degeneration of this bundle, as far as the lumbar region, which
decreases from above downwards (Fig. 230).
C
FIG, 230.— Sections of spinal cord. A, lumbar; B, thoracic; C, cervical, after extirpation of right
half of cerebellum in dog. Showing degeneration of Marchi's antero-lateral tract on same side
as the extirpation. <i, efferent spino-cerebellar bundle degenerated on right side as far as the
lumbar section, while on the left side the degeneration is slight, partial, and does not extend
beyond the cervical section. The bundle thus includes nearly the whole border of the ventro-
lateial eiilumn ; at '/ it takes in part of the pyramidal tract; at c it comprises the area
in which lies the anterior portion of Flechsig's cerebellar tract; at d some fibres of the
ventral roots are also degenerated.
It seems probable from the observations of Thomas that
Marchi's bundle springs, like the fibres of the superior cerebellar
peduncle, from the dentate nucleus, and that the degeneration of
430
PHYSIOLOGY
CHAP.
these two fibre-systems is in proportion with the injury of that
nucleus. Lesions of the nucleus fastigii produce no degeneration
in the cord.
Besides Marchi's bundle, another efferent cerebello-spinal tract,
mostly crossed, but to a small extent direct, has been described
by Mingazzini, Pick, and others. The crossed portion leaves the
internal segment of the restiforin • body, enters the raphe as
internal arcuate fibres, joins the external ventral arcuate fibres
of the opposite side, and enters the pyramidal tract (Fig. 228, c, d}.
The few uncrossed fibres
pass as external ventral
arcuate fibres and join
the pyramid tract on the
same side (Fig. 228, c}.
It is evident that the
crossed portion, since it
decussates again with the
contralateral pyramid,
joins each lateral half
of the cerebellum and of
the same side of the
cord, and that the small
uncrossed portion, which
also decussates with the
homolateral pyramid,
establishes a relation be-
tween each lateral half
of the cerebellum and
the opposite side of the
cord. This is clear from
Fig. 231.
II. The experimental
determination of the
functions of the cere-
bellum is one of the
most difficult problems in the physiology of the central nervous
system. We devoted many years (1884-91) to experiments
in the solution of this question. Previous investigators had
confined themselves almost without exception to ascertaining
the immediate effects of lesion or partial removal of the cere-
bellum or its peduncles. Eolando (1809) contented himself
with destroying half or the whole of the cerebellum in different
mammals, and giving a summary description of the effects on
the same day, without taking any trouble to keep the animals
alive. Fodera (1823) and, shortly after, Flourens (1824-42)
observed, particularly in birds, the immediate effects of small suc-
cessive ablations of increasingly deeper layers of the cerebellum.
FIG. 231.— Diagram to show crossed (a) and direct (b) cere-
bello-spinal paths which accompany pyramidal tract p,
and are in relation with the cells of the ventral horn
ca, from which the motor roots ra emerge to inner-
vate the muscles m. (Mingazzini.)
vin THE HIND-BIUIN
Stu<lv of (lie remote cl't'ects was only attempted very inadequately
liy Flourens, and always on birds. Magendie (1828), Serres
(1826), and Bouillaud (1827) in their experiments followed more
or less on the lines of Eolando, Fodera, and Flourens. After
several years, experiments on the cerebellum were resumed by
N. Schiff (1858-59), Brown-Sequard (1859-60-61), R. Wagner
(1858-1860), Dalton (1861), Lussana (1862), Leven and Ollivier
(1862-63), Vulpian (1866), Weir - Mitchell (1869), Nothnagel
(ISTl), Ferrier (1878), and others.
At the outset of our own researches on the cerebellum it
seemed to us advisable to extend our study to the higher mammals,
dogs and monkeys, in which the organ is more developed, but
which till then had rarely been employed for experiments on
account of the supposed technical difficulties.
Our principal experiments may be divided into three series,
viz. investigation of animals after removal of the lateral half of
the cerebellum, of the vermis, and of the whole or almost the
whole of the organ.
Before describing the results it seems advisable to make a few
preliminary remarks for the guidance of the student:—
(tf.) Whatever the extent or degree of the cerebellar lesion,
whether it be symmetrical or asymmetrical, unilateral or bilateral,
complete or incomplete, the resulting symptoms are disturbances
of voluntary movement.
(ft) Unilateral lesions of the cerebellum produce disturbances
chiefly on the same side of the body; while the effects of re-
moving the so-called motor region of a cerebral hemisphere are
mainly crossed, i.e. on the opposite side of the body to that
operated on.
(c) Whatever the nature of the cerebellar lesion, the true
phenomena of deficiency, i.e. those due directly to loss of the
cerebellum, are preceded by a brief period of functional exaltation ;
while in lesions of the cerebrum the phenomena of deficiency are
constantly preceded by a period of functional inhibition. To be
rigorously objective, we will refer to the immediate effects of
ablation of the cerebellum as "dynamic phenomena," leaving
undecided the question of whether they are produced by the
irritation of the operative traumatism or by the sudden cessation
of the influence of the cerebellum upon other portions of the
nervous system.
(d) To the phenomena of cerebellar deficiency of the second
period there succeeds a third series of effects, which we have
termed " compensatory phenomena " ; these are due to the activities
of portions of the cerebellum that are left intact, or of other
cerebral centres. In the first case there is organic compensation,
which consists in the gradual diminution of the phenomena of
deficiency ; in the second case there is functional compensation,
432 PHYSIOLOGY CHAP.
which consists in abnormal movements directed to meeting and
partially compensating the effects of deficiency.
(V) The phenomena of cerebellar deficiency, in association with
the processes of functional compensation, make up a syndrome or
characteristic complex of phenomena, which has long been known
by the generic name of cerebellar ataxy. It is the task of
physiology to make as exact an analysis as possible of the
individual elements that go to form this ataxy, with the object of
distinguishing the phenomena due to loss of cerebellar innervation
from those due to the instinctive or voluntary compensatory acts,
which are directed to nullifying the effects of the former.
(/) As each lateral half of the cerebellum is connected mainly
with the corresponding half of the body, it is obvious that the
symptoms of unilateral cerebellar extirpation must be greater on
the side of the operation than on the opposite side. Hence,
comparison of the two halves of the body in an animal from
which one-half of the cerebellum was removed is equivalent to
comparing two animals of the same species, age, and constitution,
one of which is in full enjoyment of its cerebellar innervation, the
other almost entirely deprived of it.
III. If not too deeply anaesthetised or enfeebled by bleeding
during the operation, dogs show signs of distress and agitation
immediately after complete removal of one-half of the cerebellum.
The animal also presents pleurothotonus or curvature of the
vertebral axis to the side operated on, tonic extension of the
anterior limb on the same side, with clonic movements of
the three other limbs ; rotation of the neck and head towards the
healthy side, slight nystagmus and squint with inward and down-
ward deviation of the eye on the side operated on, and downward
and upward of the eye on the healthy side ; and rotation round
the long axis of the body in the same direction as that of the
neck and head (i.e. from the side operated on to the healthy side
if the animal is looked at in front, from the healthy side to the
operated side if it is viewed from behind).
The immediate dynamic phenomena after total removal of the
cerebellum are agitation, unrest, and cries from the animal ;
opisthotonus, or backward curving of the vertebral axis, par-
ticularly of the neck and head ; tonic extension of both fore-limbs,
with alternating clonic movements of hind-limbs ; bilateral con-
vergence of the eyes ; and tendency to stagger and fall backwards.
These symptoms may seem more simple than those which follow
unilateral destruction, but they are really the same dynamic
disturbances spread over both sides. Opisthotonus is substituted
for pleurothotonus ; tonic extension of both limbs for tonic
extension of one limb, regression and falling backward for rotation
on the long axis.
After destruction of the vermis and, generally speaking, after
viii THE HIND-BRAIN 433
incomplete bilateral or unilateral, symmetrical or unsymmetrical
injuries, the dynamic phenomena are more irregular, both in their
nature and extent. In all cases the dynamic phenomena approxi-
mate more nearly to those of unilateral or total extirpation,
according as the peduncles of one side, or those of both, were
similarly affected.
The immediate dynamic symptoms persist for a few days—
usually eight to ten — if the wound remains aseptic ; the tonic
spasms diminish in strength and duration, and become transformed
into clonic and oscillatory movements.
The first symptom to disappear is the rotation 011 the long
axis, or tendency to fall and topple backwards (which usually
lasts only four to five days). The last to disappear is the pleuro-
thotonus or opisthotonus, which remain evident for a number of
days if the animal is suspended.
As the tonic spasm disappears and the movements become
merely clonic and tremulous, the animal's attempts to hold itself
upright and to walk gradually become more effective. Dogs, as
a rule, regain the power of floating and swimming before they
become able to walk.
In monkeys, with the exception that there is tonic flexion of
the fore-limbs instead of tonic extension, the dynamic symptoms
are identical with those described in dogs; but they are less
intense and of shorter duration, so that the phenomena of cerebellar
deficiency are more plainly seen after a very few days, when every
trace of the forced movements disappears.
The exact interpretation of the origin and nature of the
dynamic phenomena is one of the most difficult problems we meet
in the physiological study of the cerebellum, and is so far unsolved.
The feature which has more especially claimed the attention of
experimenters from Pourfour du Petit (1710), Lafargue (1838),
Magendie (1839), Schiff (1849), Longet (1878), to the workers of
the present day is the rotation of the animal on its own longitudinal
axis. Does this depend on the irritation of the fibres of the
cerebellar peduncles by the operative injury or on the sudden
removal of the influence of one-half of the cerebellum upon the
rest of the nervous system ?
In our Monograph upon the Cerebellum we declared for the
former view, which was already held by Brown-Sequard, Vulpian,
Weir-Mitchell, and others, and characterised as irritative all the
dynamic symptoms that predominate immediately after removal
of portions of the cerebellum, as Goltz had given the name of
inhibitory to those which ensue directly on cerebral ablation.
This view is supported by the following arguments :—
(«) They correspond with the degree of operative injury and
with the appearance of inflammatory and infective processes in the
wound.
VOL. in 2 F
434 PHYSIOLOGY CHAP.
(&) They predominate in the side exclusively or mainly
affected, and appear to be more pronounced and varied in pro-
portion as the lesion is deeper and extends farther towards the
cerebellar peduncles.
(c) When the peduncles are partly degenerated, in consequence
of previous removal of the vermis, the later destruction of a
lateral lobe only produces slight and transient irritative
symptoms.
Ferrier, however, showed that when there is actual irritation
or inflammation in the cerebellum the dynamic phenomena are
very different from what we had described. He found that when
a lateral lobe of the cerebellum was partially cauterised so that
the adjacent parts were irritated, rotation took place in exactly
the opposite direction to that which we observed after removal of
one side of the cerebellum.
We had never performed cauterisation experiments on the
cerebellum as they appeared unsuitable for eliciting clear and
unequivocal physiological facts, but on repeating Ferrier's experi-
ment on a number of animals we convinced ourselves of the
accuracy of his observations. We found that more or less pro-
found cauterisation of the cortex of a cerebellar lobe on one side
gave rise to symptoms that were almost exactly the opposite of
those seen after its removal. The disquiet and cries of pain are
absent — the animal rather appearing depressed and subdued;
the pleurothotonus to the injured side is replaced by slight
pleurothotonus to the normal side ; the tendency to rotate and
actual rotation round the long axis from the operated towards the
healthy side is replaced by a tendency to rotate in the opposite
direction, i.e. from the healthy towards the operated side.
On what does this reversal of effects depend ? The question is
still undecided. In reply to Ferrier we advanced the hypothesis
that the cauterisation of the cerebellum irritates the adjacent
parts as well, including the dura mater, which is a sensory
membrane capable of producing symptoms of reflex inhibition on
excitation. This, however, is not an adequate explanation. Are
the pleurothotonus and rotation in the opposite direction to be
referred to the preponderance of inhibitory effects on the operated
side or to exaggerated activity on the healthy side ? A recent
experiment on dogs indicates that it depends on both these factors.
We observed that if before cauterising the cerebellum on one side
the two halves of the cerebellum were divided 1 >y a median sagittal
section, the animal appeared subdued with pleurothotonus to the
cauterised side, and a slight tendency to rotate towards the
healthy side. Next day the animal was quiet ; it lay on the flank
of the cauterised side, and if forcibly placed on the opposite side
made a half-turn to recover this position, but showed no tendency
to rotate on its axis ; if held up there was pleurothotonus to the
VIII
THE HIND-BRAIN 435
cauterised side, Imt no rotation of its head towards the sound
side.
Mechanical excitation of one-half of the cerebellum can also
evoke motor reactions predominating in the muscles of the
opposite side. Nothnagel observed in 1876 that puncture of the
vermis with a tine needle on one side of the median line, or of one
cerebellar hemisphere, produced pleurothotonus or curvature of
the vertebral column to the opposite side, with rotation of the
head in the same direction, i.e. opposite to that observed after
removal of one-half of the cerebellum. But reactions also occur
in the fore-limb and facial muscles of the excited side. Lewan-
dowsky and J. Munk confirmed these results; they found that
tine needles must be used in order to evoke them, because with
coarser lesions the irritative symptoms are mingled with those of
the paralysis and produced quite different phenomena.
Sergi repeatedly found that simple section of the lower and
internal portion of a cerebeilar hemisphere, including a part of
the peduncles, produces a tendency to rotate, or actual rotation, in
a direction opposite to that which we observed after unilateral
cerebellar extirpation, and comparable with the effects of
cauterisation.
Electrical stimulation of one-half of the cerebellum (Lewan-
dowsky, 1903) gave parallel results. Weak induced currents
produced restlessness and consecutive movements that suggested
that the animal was suffering from vertigo. Stronger currents
produced a forced position towards the side opposite that excited
(right pleurothotonus when left side is excited); movements of
facial muscles and horizontal nystagmus of the head ; falling of
the animal to the right if excited on the left, and rotation in the
opposite direction to that observed after unilateral extirpation.
Lewandowsky, of course, assumed that there was true irritative
rotation in his case, and that ours was due to paralytic rotation.
On the other hand, Pagano (1902), working in Marcacci's
laboratory, found that merely injecting a few drops of 1 per cent
solution of curare into one cerebellar hemisphere in dogs produced
violent epileptiform reactions — mainly of the muscles of the same
side, and especially various rotatory movements — ten to fifteen
minutes after injection.
Two general propositions can be positively stated, without
danger of contradiction, in regard to the rotation round the
longitudinal axis that is constantly seen after destruction of one-
half of the cerebellum :—
(a) Predominance of the functional activity of the cerebral
centres of one side is a necessary condition for forced rotations,
and the afferent disturbance (vertigo) due to the sudden upset of
functional equilibrium is its immediate cause.
(&) The rotation phenomenon and the forced movements and
436 PHYSIOLOGY CHAP.
positions in general which follow immediately on the cerebellar
lesions (whether they are regarded as effects of irritation of the
fibres of the peduncles and of the extra-cerebellar cells with which
those are connected, or whether they are referred to the paralysis
or disturbance of cerebellar functions by the lesion) must not be
regarded either as the converse, or as an exaggeration, of the defect
phenomena that appear in the second post-operative period.
That vertigo is the true cause of forced movements and,
generally speaking, of the dynamic phenomena of the first post-
operative period is directly confirmed by clinical cases of cerebellar
disease, in which vertigo is a very frequent symptom. But the
indirect evidence afforded by the behaviour of monkeys with
lesions of the cerebellum is also most striking ; they soon learn to
avoid rotation on their long axis by clutching the surrounding
objects with their hands. If set upon the bare ground they
support not only their trunk but also their head on it. Further,
the fore-limb of the operated side is abducted as far as possible,
and the animal remains indefinitely motionless in this position in
order to avoid vertigo.
The disturbance, produced either by irritation of the peduncular
fibres or by the sudden disequilibration of the functional activities
of the two sides by the sudden paralysis of one, may produce
vertigo. On the other hand, we know that independent of any
cerebellar lesion similar rotatory vertigo with actual rotation on the
longitudinal axis may be produced in dogs, either by section of the
vestibular nerve (Bechterew) or by a unilateral lesion of the
inferior olive (Probst). As the relations of the vestibular nucleus
and the olive with the cerebellum are known, it might be assumed
that here also the disturbance of cerebellar influence comes into
play in producing the rotation phenomenon. But even when the
cerebellum has been totally removed it is still possible to produce
galvanic vertigo in dogs (Purkinje and Hitzig) which proves that
vertigo may arise without active participation of the cerebellum.
There is evidence which tends to show that the rotary phenomena
which accompany vertigo depend actually neither on the cere-
bellum nor on the brain-stem, but solely on the so-called motor
zone of the cerebrum. In this connection the symptoms described
by Pagano after injections of curare are of great interest. If the
motor zone (sigmoid gyrus) is excited on the side opposite the
cerebellar hemisphere into which curare is injected, no localised
movements of this side result, and the rotation of the body round
the longitudinal axis occurs in the opposite direction. Complete
removal of the motor zone on both sides entirely suppresses both
the general convulsions and the partial tonic contractions ; only
an increase in muscular tone is perceptible, particularly in the
muscles of the injected side.
This series of facts shows that the dynamic phenomena of the
vin THE HIND-BEAIN 437
early post-operative period are associated with a form of vertigo,
and that they are neither the converse to, nor an exaggeration of,
the defect phenomena of the second post-operative period, because
they are not fundamentally due to excessive activity nor to
paralysis of the cerebellum.
The explanation of the dynamic phenomena of the first period
is still a mystery; it is very doubtful how far they depend on
irritation or paralysis of the cerebellar peduncles. It is incon-
testable, and in our opinion clearly proved, that it is impossible
at present to argue from these phenomena in regard to the normal
functions of the cerebellum. If in our 1891 Monograph all
these dynamic phenomena of the early post-operative period were
referred on the strength of ablation experiments to irritation, on
the other hand we avoided the more serious error of assuming
them to be the converse of the true phenomena of cerebellar
deficiency. Indeed, we have repeatedly noted that phenomena of
irritation prevail in the muscles of the fore-limbs and neck, and
phenomena of deficiency in the muscles of the hind-limbs and
vertebral column.
IV. As the dynamic phenomena of the first period disappear,
the symptoms which depend on loss of the cerebellar functions
become more and more prominent. These, as we have already
said, constitute the syndrome which is known as cerebellar ataxy.
The dog, after removal of half its cerebellum and as the early
dynamic phenomena are disappearing, is so weak in the muscles
of the limbs on the operated side, particularly the hind-limbs,
that at first sight they appear paralysed. In order to move from
one place to any other, it is obliged to crawl on the buttock of
the operated side, the principal effort being made with the muscles
of the healthy side. This inability to stand upright and walk
may last four weeks. During this time, however, if the animal
can lean the flank of the operated side against a wall, it is able
to stand upright and make regular steps. Further, if thrown
into water, it keeps itself quite well on the surface, maintains
its equilibrium, and swims with perfect co-ordination. But if
its method of swimming be carefully watched, it is seen that it
cannot keep the trunk perfectly horizontal, but the operated side
lies constantly deeper in the water than the normal side. More-
over, the animal is unable to swim in a straight line, and
constantly makes circus movements to the sound side.
The interpretation of these facts is obvious. The animal is
incapable of standing on its feet and walking unless it can find
support on the operated side, because the weakness of the limbs
on that side is so great that they cannot bear the weight of its
body. It succeeds in swimming well, because the water supports
the weight of the body. In swimming, its healthy side is higher,
and it continually turns towards this side, because t*he move-
438 PHYSIOLOGY CHAP.
ments and the thrusts in the water with the limbs of the healthy
side are more vigorous and energetic than those on the operated
side.
The animal gradually learns to make more and more successful
123 4 5
FIG. 232. — Tracings of footprints during ordinary progression. From live normal dogs. (Luciani.)
The prints of the fore-legs are represented by small circles, those of the hind-legs by triangles.
The prints of the left leg are distinguished from those of the right by a black dot in the centre
of the circles and triangles. The traces of the right and left feet are united, respectively, by
lines. Each 25 mm. corresponds to 1 in. 1, Shows the elegant gait of a young poodle ; 2, the
clumsy gait of a bitch weighing (JOOO grins. ; 3, a young dog weighing 2700 grms. ; 4, a young
dog of 2980 grms. ; 5, the reeling gait of a bitch weighing 5400 grms. , which was completely
blind owing to enucleation of the eyeballs.
efforts at standing upright and walking, till at last it succeeds.
At first it falls constantly to the side of the operation, owing to
the giving way of the limbs on that side and consequent loss of
vni THE HIND-BEAIN 439
equilibrium ; after a time it i'alls less frequently. This gradual
restitution of function is only to a small extent due to organic
compensation, and depends far more upon functional compensation,
on the gradual acquisition of new acts and movements, which are
capable of compensating the effects of cerebellar deficiency, and of
preventing loss of equilibrium and the tendency to fall towards
the injured side. By the curving of the vertebral column the
weight of the hind part of the body is thrown towards the affected
side, and thus falls chiefly on the opposite hind-limb, i.e. the hind-
limb unaffected by the operation. By abduction of the fore-limb
it widens the basis on which the body rests, lowers its centre of
gravity, and makes the passive flexion of the fore-limbs in the
various joints more difficult.
Eeproduction of the footprints gives a record of these com-
pensating processes and a more minute analysis of the gait. The
normal tracing of the dog's ordinary walk is not always perfectly
equal and regular, but varies not only with the age and size of
the individual, but also with its race, as shown in the examples
of Fig. 232. To understand this tracing it must be remembered
that the ordinary step of the dog is made by alternate setting
down and lifting up the two diagonal pairs of feet, and that both
the setting down and the lifting up of the fore-limbs precedes
those of the hind-limbs, so that four distinct taps occur at regular
intervals, as can be proved by listening when the animal walks
upon a wooden floor.
If we examine the tracing of the footsteps of a bitch in which
the right half of the cerebellum had been completely extirpated,
it is seen to be very different from the normal (Fig. 233). Tracing
b was taken two months after the operation ; the animal held the
principal axis of its body* curved to the right and oblique to the
direction of progress, so that the limbs of the right side were
more raised and abducted than in the normal, and the left limbs
adducted. It shows this alteration in the gait very plainly,
especially in the marked displacement to the right of the foot-
prints of the hind-limbs, the varying length and force of the step,
and the irregularity of the two lines which join the prints of the
fore-paws, which normally are almost parallel. A year after the
operation tracing c was taken from the same bitch, and showed
greater regularity of gait, although the displacement to the right
of the footprints of the hind-limbs still persisted, though it is less
pronounced. After blindfolding the animal's eyes tracing d was
taken, and shows that the gait was not much altered from that
with the eyes open ; but the direction of progress was uncertain,
the steps shorter, and the fore-limb more abducted. Tracing e
was taken a few minutes after the subcutaneous injection of
30 cgrms. of morphine hydrochlor. and shows exaggeration of all
the above anomalies in the animal's gait.
440 PHYSIOLOGY CHAP.
When the dog with half a cerebellum has succeeded, after
repeated attempts, in avoiding falling- to the injured side by
appropriate compensatory acts, it also becomes able to avoid
forced circus movements towards the healthy side in swimming ;
it is able to keep to a straight line, and to turn towards the
operated side. For this purpose it adopts the same device in
PIG. 233.— Tracings of the gait of a bitch weighing 5150 grins, after complete extirpation of the
right half of the cerebellum. (Luciani.) 6, tracing taken two months after the operation ;
c, over a year from the operation ; d, after a year with eyes bandaged ; e, after a year when the
animal had previously received morphia.
swimming as in walking, that is, curvature of the vertebral
column towards the defective side, which enables it to use the
lumbo-sacral part of its trunk as a rudder. It compensates the
stronger action of the limbs of the sound side by an appropriate
degree of vertebral curvature, and swims in a straight line or even
turns towards the defective side.
One of the main results of our studies on the cerebellum is
that we have shown it to be possible, and even easy, to separate
the phenomena of cerebellar deficiency from the phenomena of
VIII
THE HIND-BKAIN
441
functional compensation, that is, the instinctive and voluntary
acts above described, by which the animal tries to repair the
effects of loss of cerebellar function. As soon as the so-called
motor zone of the cerebrum is destroyed on one or both sides the
animal with a half cerebellum loses for a long time, or for ever,
the newly acquired capability of holding itself upright, and
walking without falling towards the affected side.
When the motor region of the left cerebral hemisphere was
removed from the bitch with the half cerebellum which, fourteen
months later, gave the tracings in Fig. 233, she once more lost
A B
FIG. 234. — Brain of the bitch from which the preceding tracings were taken. (Luciani.) A, upper
surface, showing absence of right half of cerebellum and of left sigmoid gyrus. B, lower surface,
shows diminution of right half of pons and of left pyramid.
the power of standing upright and walking, because the limbs of
the right side could not support the weight of the body. Twenty
days after the cerebral operation she succeeded, by leaning her
right side against a tree, in raising herself on her four legs. But
as soon as she tried to leave this support she fell. She was, how-
ever, able to swim well to the right, and even in a straight line,
notwithstanding the curvature of the vertebral column to the
right, because the strokes of the left limbs on the water were
much stronger than the right. About six months after the last
operation she could once more walk without support, but still
fell not infrequently to the right. In walking she held the
axis of her body very obliquely to the direction she was going in,
and even more curved to the right than at the time when tracing
I was taken. When blindfolded she did not attempt to walk,
442 PHYSIOLOGY CHAP.
ami if forced to move, she fell to the right, owing to the limbs
of the right side, in which muscular and cutaneous sensibility
were altered, giving way. If thrown into water in a pool, she
swam properly with eyes open or blindfolded, with well-coordinated
movements, but with the right side deeper in the water than the
left. She died from severe and repeated epileptic attacks, live
months after the second operation. When the brain was removed
from the body both lesions were found to be complete (Fig.
234, A, B).
In this case the inability to stand upright and to walk, after
ablation of the motor zone on the side opposite that of the cerebellar
operation, was not complete and permanent. The partial re-
education of the animal, notwithstanding the marked alteration
in motility and sensibility of the right limbs, was undoubtedly
due to the compensatory function of the right motor zone, which
had been left intact. In other cases, in fact, when the animals
were deprived of half the cerebellum and both motor zones, we
obtained permanent loss, not only of maintaining the erect posture
and of walking, but of swimming also.
The phenomena of cerebellar deficiency exhibited by the animal
with a half cerebellum, particularly in the limbs of the operated
side, must be analysed more accurately. Let us again refer to the
bitch from which the tracings in Fig. 233 were taken.
Prior to the extirpation of the right half of the cerebellum
this animal had been trained to sit up for a long time on its hind
legs. After the operation it lost this power, and had not regained
it fourteen months later. When food was brought to the animal
and held above its head, it stood upright, but fell suddenly, owing
to the flexion of the right hind-leg. When it was made to draw
a weight tied to its tail, the greater expenditure of force required
in walking caused it to fall frequently to the affected side. When
a clamp was applied to the lobe of the left ear the animal tried to
remove it by appropriate movements of the left fore-limb ; but if
the same clamp was placed on the ear of the side operated on, the
animal never attempted to use the limb of that side, but contented
itself with vigorously shaking its head, which frequently caused it
to lose its balance and fall to the right. To these and other
similar phenomena of cerebellar deficiency we gave the name of
asthenia : muscular asthenia due to nervous asthenia, the direct
consequence of loss of the influence of the homolateral half of the
cerebellum.
Other phenomena prove that this asthenia is always closely
associated with a definite diminution of the normal tone of the
muscles — i.e. of the degree of their active tension during rest—
which must exert a considerable influence on the contractions and
relaxations of the muscles, particularly as regards the form, degree,
and duration of these processes.
vin THE HIND-BRAIN 443
When the bitch that had lost the right half of its cerebellum
was held up by its flanks in the air, the muscles of the right hind-
limb were seen to be more relaxed than those of the opposite side,
as in the hind -leg of Brondegeest's frog, after section of the
posterior spinal roots. On lifting the soles of the animal's feet
with the palm of the hand, greater resistance to passive flexion
was felt in the leg of the healthy side than on the side operated
on ; the latter, indeed, could be flexed beyond the normal limit,
that is, farther than the limb of the sound side. If the animal
was watched while feeding in the upright position, with its limbs
separated to widen the base of support and its whole attention
given to its food, it was noticed repeatedly that the legs of the
injured side gradually gave way, so that the animal would have
lost its equilibrium and fallen to this side, if it had not become
aware of its danger in time to recover its equilibrium by suitable
compensatory movements.
The tendency of the animal to fall towards the operated side
during the early days after removal of one-half of the cerebellum
is evidently related to the passive flexion of the limbs when
it is intent on its food. On watching carefully, it is evident
that the fall is due, not to the irregular position of the injured
limbs, but to the unexpected relaxation of the muscles, which the
animal has not yet learned to guard against.
Another more easily observed phenomenon may in our opinion
be referred to the too sudden relaxation that follows the contraction
of the muscles, owing to diminution of their tone. We noticed in
our bitch that the limbs of the operated side were lifted higher
than the normal, as if she had to mount up little steps, and
that she set them down more forcibly on the ground, and thus
made more noise on the wooden floor. It appears to us highly
probable that the abnormal elevation is the effect of the too rapid
relaxation of the extensors of the limbs during the contraction of
the flexors, and the stamp the effect of the too rapid relaxation of
the flexors while the extensors contract. We shall return to this
phenomenon in order to discuss other and less probable interpreta-
tions of it.
To this group of symptoms, which are intimately connected
with and yet distinct from asthenia, we gave the name of atonia,
which has met with general acceptance.
A third group of symptoms may be added to asthenia and
atonia if the mode in which the contractions are carried out is
carefully observed. In normal limbs the contractions of the
muscles are gradual and sustained in character, that is without
interruption of continuity, without trembling or oscillation, and
with perfect fusion of their elementary impulses. When lying
down in its kennel the animal, after removal of half its cerebellum,
only differs from the normal animal by a slight and almost con-
444 PHYSIOLOGY CHAP.
stant trembling of the head, which in this posture is the only
unsupported part of the body, its position being maintained by the
active contraction of the muscles of the neck. When the animal
stands it can be seen that the tremor is not limited to the head,
but involves the whole body, which oscillates slightly either in the
transverse, oblique, or diagonal direction. When it moves slowly
this tremor is exaggerated; the -movements of the limbs on the
operated side and of the vertebral column show a characteristic
defect in continuity and stability, owing to the intermittent nature
of the contractions, as though the summation of single impulses
were imperfect. This defective co-ordination and unsteadiness is
known to clinicians as titubation, since it gives the impression
that the patient hesitates to decide, or has difficulty in transmitting
the voluntary impulse to the muscles.
This titubation, however, disappears when the animal spon-
taneously, or compulsorily, accelerates its gait. No signs of
ataxy are then perceptible other than those which depend on
hemiasthenia and hemiatonia, and on the abnormal compensatory
acts by which the animal endeavours to escape the effects of these.
This proves that the tremulousness does not depend on delay in
the development of the voluntary impulses, or on difficulty of
transmitting them to the muscles ; but solely on the incomplete
summation of the single impulses, owing to which the movements
become slightly tremulous.
On the other hand, the tremor increases and assumes the
character of marked rhythmical oscillations when the animal eats
some favourite food. There are also true pendulum movements of
the head in the diagonal direction, due to the alternate functional
predominance of its depressor and levator muscles, which are
partially transmitted over the whole trunk. The animal is unable
to check or arrest them, so that its nose may hit the bottom of
the dish or the floor on which the food is placed.
To this group of phenomena, which includes tremor, titubation,
and rhythmical oscillating movements, we gave the name of astasia
for the sake of brevity and owing to their probable common
origin.
The ataxy in apes deprived of half their cerebellum is
fundamentally identical in its main features. Generally speaking,
compensation sets in more rapidly and in a very varied form in these
animals. We have already seen that monkeys can overcome the
effects of vertigo soon after the operation. On the disappearance
of the dynamic disturbances they are almost always able to avoid
falling to the affected side ; in walking the limbs of this side are
strongly abducted ; in sitting upright they support themselves by
placing one or both hands to the ground or by holding on to the
leg of a table. They can also avoid the swaying of the head and
vni THE HIND-BRAIN 445
trunk, which miffht cause them to fall when the hands are used
o
for eating, by resting the head firmly on the ground or against
a wall.
But these artifices, which the monkey can use in consequence
of the higher development of its motor centres, do not obscure the
signs of cerebellar deficiency, which are even more striking than
in the dog.
The asthenia of the limbs on the injured side is expressed, in
addition to the signs already described in dogs, in the less use
which the animal makes of them ; when a favourite fruit is offered,
the monkey always grasps it with the hand of the sound side.
This is not due to paresis of the limbs of the operated side, for
when the animal is suspended in the air by a sling round its
trunk, and one of the feet is brought near a small table, the latter
is strongly grasped with both hands. By pulling gradually on a
dynamometer which is fixed to the sling, while the ape is fastened
in this way to the leg of the table, it is possible to measure the
force by which the animal holds the table ; also it will be noticed
that first the hand of the operated side and then that of the sound
side gives way.
The atonia is shown by the fact that when the monkey is on all
fours on the ground, in the horizontal position, the affected side
hangs lower, owing to the defective tone in the muscles of the
limbs on that side. Sometimes there is slight ptosis of the upper
eyelid of the injured side, and a drawing over of the mouth towards
the healthy side, when the animal shows its teeth in biting its
food.
Finally, the astasia that is expressed in tremor, titubation, and
rhythmical oscillation is more marked in the monkey than in the
dog. Monkeys show tremor not only of the head, but unmistak-
ably in both the fore- and the hind-limb of the operated side,
whenever these are employed.
Patrizi (1904), to render the atonia, asthenia, and astasia more
distinct, recorded graphically both simple twitches and tetanic
contractions of the muscles of the normal and the operated side
in doss, after removal of one-half of the cerebellum. His observa-
O '
tions show that muscles deprived of the influence of the cerebellum,
and excited, directly or reflexly, with electrical stimuli, in an
animal that has been immobilised but not anaesthetised, present
curves which differ from those of the normal side, owing to
diminution of tone, lower functional energy, more rapid fatigue,
and the incomplete fusion of the elementary twitches from which
the contraction as a whole results.
On anaesthetising the animal to eliminate the normal tone of
the muscles the myograms of the limbs on the healthy side
resemble those obtained without narcosis from the limbs of the
decerebellated side. From these results Patrizi was led to con-
446 PHYSIOLOGY CHAP.
elude thab the asthenic and astatic phenomena are intimately
connected with the atonic symptoms ; this agrees well with our
conception of the physiology of the cerebellum.
A general fact to which there has been no exception in our
numerous experiments on dogs and monkeys is that the phenomena
of deficiency consequent on complete unilateral extirpation of the
cerebellum are limited exclusively to the neuro-muscular system ;
sensation is not disturbed.
We more particularly investigated the tactile and muscular
sense.
On merely touching a normal dog while it is eating, or while
its eyes are bandaged, or, better, while it is suspended in the air by
means of a sling with the limbs hanging down (Hitzig's method),
it shows by a swift movement of reaction that it has noticed the
contact. If the tactile sensibility of the decerebellated dog is
tested in the early post-operative period, when the animal is still
incapable of standing or walking, the reactions to contact are
usually absent in the limbs both of the operated and of the normal
side, and there may be no reactions to slight painful sensations of
any kind, particularly upon the operated side.
But if the examination is repeated three to four weeks after the
operation, at the time when the locomotor ataxy is at its maximum,
the reactions to contact never fail ; only they occur with a
perceptible delay on the operated, as compared with the normal, side.
Finally, during the period — which may last over a year — in which
the cerebellar ataxy is final and permanent, with no prospect of
improvement, the animal reacts to slight contacts with equal
promptness on either side. This shows that unilateral removal in
the cerebellum does not disturb tactile sensibility.
It is more difficult in animals to make any exact investigation
of the so-called " muscular sense " —by means of which we are aware
of the position of our limbs, the direction of active and passive move-
ments in the same, and the degree of tension or resistance opposed
to muscular contraction, without the aid of tactile sensibility and
vision. Of these different forms or qualities of muscular sense, the
first, which conveys the sense of the position of the limbs, is easy
to examine in dogs. When a normal dog with its eyes bandaged
is kept upright on a table, and any one of the four limbs is brought
into an unnatural position, e.g. when the dorsal surface of the foot
is placed in contact with the table, the limb is brought back
instantly to the normal position ; if one of the four legs is left
unsupported, by letting it hang over the edge of the table, the
animal at once draws it up and puts it back on the table.
In the dog after removal of half the cerebellum it is impossible
to carry out this experiment successfully while the animal is still
unable to stand on its legs, and therefore to react to unaccustomed
postures, even when perfectly aware of them. When it begins to
viii THE HIND-BRAIN 447
walk, and tin- cerebellar ataxy is pronounced, the animal does not
always correct the abnormal positions in which its limbs are
placed, and when it does there is a certain delay in the limbs of
the side operated on, as compared with the normal side. Ducceschi
and Sergi drew attention to the fact that during this period the
dog with half a cerebellum in many cases does not correct the
abnormal postures given to the limbs of the operated side, and
sometimes, though more rarely, not even those of the limbs on the
healthy side, in which there is no reason to suspect any disturb-
ance of the muscular sense.
If, lastly, the muscle sense is investigated during the long
period in which the cerebellar ataxy has become stationary and
permanent, anomalous positions of the limbs of the operated, as
well as of the sound, side are corrected as in normal dogs.
These facts show that absence of the cerebellum is com-
patible with integrity of the muscle sense. It is evident that the
frequent failure to react in the early stage and afterwards has no
value as evidence of sensory disturbance ; in this kind of research
the maxim that one well-estal dished positive proof is worth more
than any number of negative proofs holds good.
If the behaviour of a dog in which the cortex of one side of
the so-called sensory -motor area (sigmoid gyrus) has been removed
is compared with that of the dog with only half a cerebellum,
the conclusion that the muscular sense is seriously disturbed in
the former and has not perceptibly suffered in the latter is
inevitable. In both the defect phenomena disappear in time, but
in the former the failure to correct the abnormal postures of the
limbs persists for months, while in the latter it disappears entirely
as soon as the animal has acquired the power of walking, although
extreme ataxia persists.
But the most cogent proof of the integrity of the muscular
sense in decerebellated dogs is the retention of power, when the
animal lies at rest, of scratching the skin of the abdomen, thorax,
and neck with one or both hind-feet, with perfect adaptation to
the purpose of removing disagreeable stimuli. This is such a common
occurrence that it may altogether escape the careless observer.
But this action, on the one hand, necessitates integrity of cutaneous
sensibility, and on the other capacity for rightly exciting, directing,
measuring, and therefore being aware of muscular contractions — in
a word, integrity of the muscle sense.
V. A critical analysis of the ataxia due to unilateral lesions of the
cerebellum will greatly facilitate our task of analysing the second
typical form of cerebellar ataxy — that which results from bilateral
lesions. Speaking generally, the absence of the whole cerebellum
produces the same symptoms as the loss of one-half, only they
affect both sides, and do not predominate in one alone.
This spread of the defect phenomena to both sides produces a
448 PHYSIOLOGY CHAP.
peculiar form of motor ataxy, which has been well described as
" drunken gait " —a name which suggests itself at once to every
one who sees an animal attempt to walk for the first time after
removal of its cerebellum. A careful analysis of this reeling zig-
zag gait shows that it results from the same factors which we
distinguished in the gait of animals with a half-cerebellum, i.e.
from asthenia, atonia, and astasia, and from compensatory pro-
cesses, which are not, however, limited to one side, but involve
both.
On the disappearance of the dynamic phenomena of the early
post-operative period, the dog remains for a certain time incapable
of standing on its feet and sustaining the weight of its own body.
At each attempt to get up it falls now on one side and now on
the other. Later it begins to rise on the fore-limbs only, because
the hind-limbs flex at each attempt to stand up.
That this inability of the animal to assume and maintain the
upright posture is due solely to asthenia, atonia, and astasia, and
not to inability to co-ordinate its movements, nor to deficient
equilibrium, is proved by the fact that during this period the
animal is able to swim as well as any normal dog.
At a later period the animal manages to rise gradually, and to
take a few steps, but it frequently falls to one side or the other,
owing to the flexion of the limbs, particularly the hind -legs,
which are always the weakest. In the upright position it is never
still for a moment, and always seeks the support of a wall in its
first attempts at walking. It is only later that it gradually learns
to walk without support and to fall less often and less suddenly,
till at last it avoids this altogether.
This functional restitution is only to a minimal extent due to
organic compensation ; it depends fundamentally upon functional
compensation. We must carefully examine the form and the
effects of these compensatory processes, because it is these that
give its most characteristic feature to cerebellar ataxy.
These compensatory processes consist mainly in exaggerated
abduction of the four limbs in walking. This widens the base of
support and lowers the animal's centre of gravity, making it less
liable to fall ; at the same time the swaying of the body increases,
as this is a reaction to the resistance which its feet encounter from
the ground (Fig. 79, p. 119).
The decerebellated animal cannot use the muscles of the
vertebral column to compensate its symptoms, as they are atonic
and asthenic on both sides ; this contributes to the horizontal
oscillations and frequent alternating displacements of the animal's
centre of gravity to right and left. The not uncommon cross-
ing 'of the fore-limbs, so that the right foot is set down to the
left and the left foot to the right side, is undoubtedly a com-
pensatory adaptation, intended to obviate the effects of these
viii THE HIND-BRAIN 449
exaggerated horizontal oscillations. It can easily be understood
that it' the animal's trunk is inclined to the left and the centre of
gravity displaced to that side, while the right fore-limb is raised,
then, in order to recover equilibrium, the limb must he put down
obliquely to the left, so that it crosses with the leg of this side;
the contrary must take place if while the left leg is raised the
FIG. 235.— Tracings of gait of a bitch wei.u'hinj,' 0!>75 jjrnis. in which the cerebellum had been almost
completely removed by three operations. (Luciani.) ft, tracing obtained two and a half
months after final operation ; c, eleven months after; r', the same with eyes blindfolded.
trunk is suddenly inclined to the right while the left leg is raised.
This interpretation is confirmed by the fact that crossing of the
fore-limbs almost always occurs when the animal tries to alter its
direction, as shown by the tracings, of the footprints (Fig. 235).
In this case it curves its cervical spine to the right or left, so that
the left fore-limb crosses with the right, or the right fore-limb
with the left, to avoid loss of equilibrium and the danger of
falling.
So that when in the decerebellated animal there is a marked
VOL. in 2 G
450 PHYSIOLOGY CHAP.
displacement of the centre of gravity to one or the other side as
it walks, it can recover its equilibrium either by exaggerated
abduction or by exaggerated adduction of the fore-leg, propor-
tionate to the degree of displacement and the stage of the step at
which it occurs, whether at the moment of dropping or raising one
or the other fore-limb. The gait of the drunken man, at least in
mild intoxication, also results from depression of the energy and
tone of the nervous system (Schmiedeberg, Bunge) ; by facilitat-
ing the flexion of the limbs under the weight of the body this
produces abnormal involuntary lateral displacements of the centre
of gravity, which the individual compensates by exaggerated
abduction or adduction of the limbs.
The movements of the decerebellated dog are not indeed the
best adapted to the object of preserving equilibrium and recovering
it when menaced, with a minimal expenditure of energy. We
have seen that the animal with half a cerebellum lifts the limbs of
the injured side, particularly the fore -limbs, higher than the
normal and stamps them more firmly on the ground. This
peculiarity, to which we gave the name of motor dysmetria, and
which is well described by the term " hen's gait," is seen on both
sides in dogs after removal of the cerebellum. Whatever the
explanation of this dysmetria, it undoubtedly expresses an
imperfect functioning of the peripheral organs whose task it is to
effect compensation, so that the animal wastes part of its energy
uselessly. We have already shown how this may be interpreted
as the simple effect of atony of the leg-muscles, owing to which
there is a too rapid relaxation of the extensors when the flexors
are contracting and a too rapid relaxation of the flexors while
the extensors are contracting. So long as this hypothesis has not
been experimentally disproved, we cannot include dysmetria in the
fundamental elementary symptoms of cerebellar deficiency which
consist in atonia, asthenia, and astasia. But we shall return
later on to this disputed point.
The cerebellar ataxy of monkeys which have lost both sides
of their cerebellum only differs from that of dogs in the more
varied form of the compensatory processes, owing to their greater
activity.
During the period in which the monkeys are unable to stand
upright, and are compelled by the functional incapacity of their
hind-limbs to drag the body along the ground, they can clamber
on to the furniture by means of their fore -limbs, which are
always less asthenic than the hind. Even long after the operation
the monkey is incapable of standing erect and of walking in the
vertical position on its hind-legs only, as it not infrequently does
under normal conditions.
Again, the dorsal curvature of the back, due to atony of the
extensor muscles of the vertebral column, is more pronounced
vm THE HIND-BRAIN 451
in monkeys than in dogs, so that in the tracing the foot-
prints of the hind -limbs always fall in front of those of the
fore-limbs (Fig. 236). The animal deviates from side to side in
walking, making an undulating line, and if it falls to right or left
this is always due to the giving way of one or both hind-limbs,
in which atony is predominant. In comparison with a normal
monkey, it moves more slowly, and from time to time feels obliged
to rest, sitting on its buttocks.
The astasia is most prominent in the neck, but spreads more
or less to all the other muscles, as shown by the slight trembling
of the limbs each time they are used for isolated movements, as
to carry fruit to the mouth, to catch the insects in the hair, etc.
In monkeys, too, the limbs are raised unduly in walking
(dysmetria), owing to disturbed functions of the organs charged
with the compensatory processes. This dysmetria is certainly
FIG. 236.— Male Macacus in which nearly the whole of the cerebellum was extirpated at one
sitting. (Luciani.) b, tracing obtained one and a half months after the operation ; c, tracing
taken after a yeai .
not sensory in origin, because cutaneous and muscular sensibility
are not found, with the various methods of investigation which
can be employed on animals, to be appreciably disturbed. If
total extirpation of the cerebellum is performed on an animal
which has previously been deprived of the signioid gyri, which
contain the senso-motor area, or if, vice versa, these are excised
in an animal that has already lost its cerebellum, it remains
for the rest of its life incapable, not only of walking, but
even of supporting itself for a few moments in the erect posture.
This depends less on the fact that the motor defect phenomena
are much greater in this case, because those which depend on the
absence of the cerebellum sum up with the others which are due
to deficiency of the two cerebral areas, than on the removal of the
sigmoid gyri, which disturbs cutaneous and muscular sensibility ;
the animal consequently loses the power of compensation by which
it widens its base of support to save itself from falling.
Between the two extreme typical forms of cerebellar ataxy
described, which are due to the total or almost total absence of half
452 PHYSIOLOGY CHAP.
or the whole of the cerebellum, there are a number of intermediate
forms, due to partial and more or less extensive, symmetrical, or
asymmetrical lesions of this organ, which can more often be
observed because it is much easier to keep alive animals with
partial mutilations of the cerebellum.
The most important difference between the typical forms of
Fio. 237. — Gait of a bitch of 6000 grms. in which the two lateral halves of the cerebellum
were divided by a vertical cut, much of the grey matter of the vermis being lacenttrd.
(Luciani.) a, tracing before the operation ; b, four days after operation ; c, live days after ;
d, a month after ; c, two months after.
ataxy described above and these intermediate forms consists in
the fact that while the former improve but little, and persist
throughout the animal's life, the latter improve progressively
until they become latent, i.e. there is a true organic compensation,
which gradually makes the various forms of functional compensation
superfluous.
The tracings in Fig. 237 were taken from an adult bitch in
vin THE HIND-BRAIN 453
which the cerebellum had been divided in the median line by a
small knife and a hook, so that a considerable part of the grey
matter of the vermis was destroyed.
Tracing a represents the animal's normal gait ; four to five days
after the operation tracings b and c were taken, which show marked
al id action of both fore- and hind-limbs, in order to widen the base
of support, thus making it easier to maintain the equilibrium and
avoid falling on one side or the other. The steps are also seen to
be shorter in comparison with the normal; to cover the same
distance 10 steps were taken in a, 14 in b, 13 in c. Tracing d
was made one month, and tracing e two months, after the
operation, when the improvement in walking is evident and the
gait so nearly normal that no one could distinguish it without
comparing the tracings.
In another bitch we excised the whole of the median lobe or
vermis, without, however, exposing the floor of the fourth ventricle,
as the uvula was left partly uninjured. Tracing b of Fig. 238,
taken ten days after the operation, when the dynamic phenomena
had not entirely ceased, shows very grave locomotor disturbances ;
the steps are extremely short and it was found on listening that
the taps of the feet on the floor occurred at irregular intervals ;
each fore-leg frequently crosses that of the opposite side, but the
hind-limbs do not cross. Owing to the strong lateral oscillations
of the vertebral column the direction of progression is curved, and
often a zigzag, and the distance between the print of each lateral
pair of feet varies, which produces a marked disturbance of
co-ordination. Two days later, when the dynamic disturbances
had disappeared, tracing c was taken, which shows a surprising
improvement in the gait, and a week later tracing d, which differs
little or not at all from the normal. Tracing d' with the animal
blindfolded was obtained on the same day, and shows how little
influence vision has upon the gait. A month later the gait is
approximately the same, as shown by tracing e. Tracing e,
obtained after a hypodermic injection of morphia, shows that its
action upon the nervous centres causes the partial reappearance
of the ataxic phenomena.
All our researches lead to the important conclusion that organic
compensation of partial lesions is dependent on the remaining
portions of the cerebellum, i.e. on parts with the same functional
character as the part extirpated, and that compensation ensues so
much the faster and to a greater extent, in proportion as the part
destroyed is small in comparison with the portions left intact and
able to function.
A valuable confirmation of this analysis of the ataxy due to
more or less complete extirpation of the cerebellum in dogs was
given by Langelaan (1907) in his admirable description of a case
of congenital cerebellar ataxy in a young cat, which he examined
454
PHYSIOLOGY
CHAP.
by physiological tests during life and with histological methods
after its death. While alive the animal exhibited all the defect
phenomena which we described under the heads of asthenia,
atonia, and astasia, particularly in its hind-limbs. These defect
phenomena were associated with compensatory phenomena, as
pronounced abduction of the fore- and hind-limbs. Langelaan
FIG. 238. — Tracings of gait from a bitch weighing 5395 grms. which had been deprived of the median
eriebellar lobe. (Luciani.) a, tracing nine days after operation; c, eleven days after; d,
nineteen days after ; d', the same, on blindfolding the animal ; «, a month after ; e', the same
after hypodermic injection of morphine.
carefully examined sensation without discovering any disorder ;
the muscle-sense, which he tested minutely, was almost normal.
At the post-mortem examination he observed a marked atrophy
of the whole cerebellum, which involved only the cortical elements
(granular layer and layer of Purkinje's cells) ; while the central
nuclei and those of Deiters and Bechterew were normal in form
and structure. In addition to the atrophy of the cerebellar cortex
vin THE HIND-BRAIN 455
there was an associated atrophy of certain systems of fibres of the
cord and bulb.
VI. As long ago as 1879 Nothnagel pointed out that the
symptoms of disease of no other part of the brain are so uncertain
as in the cerebellum. Even to-day loose, inaccurate, and con-
tradictory clinical observations only tend to make any general
conception of the functions of the cerebellum difficult. The
reasons for this failure of clinical and experimental observations
to agree are numerous, and must be understood by the physiologist
who wishes to avail himself of clinical observation.
In the first place, the material for clinical observation of
diseases of the cerebellum is not plentiful. In 1899 Adler
published a brief review of 124 of the best observed cases from
the literature of the ten years preceding. To this survey we need
only add the few cases published between 1898 and the present
day.
In these statistics cases of tumours of various kinds pre-
dominate largely over all other forms of disease ; atrophy and
agenesia are less frequent ; still less common, haeniorrhagic foci,
softening, abscesses ; rarest of all, traumatic and surgical lesions.
A highly important fact which impresses every one who
studies clinical cases of cerebellar diseases is that in some of them
the disease remains obscure or latent during life and is not
suspected before the post-mortem examination. Our Monograph
of 1891 showed that certain of the cases described as "latent"
were so only to the extent that the accentuated form of dysmetria
of movements — which many of the older and some of the modern
clinicians hold erroneously to be the most characteristic sign of
cerebellar disease, and which are fallaciously termed " disturbances
of co-ordination " —were wanting. But in other cases there could
be no doubt that the lesions of the cerebellum presented no
symptoms.
If these cases of comparative or total absence of the essential
phenomena of cerebellar deficiency are investigated one by one; it
will be found that they are all instances of agenesia, viz. a more
or less complete congenital defect or arrested development of the
organ, dating back to embryonic life, or of sclerosis or atrophy,
which are the final outcome, of circumscribed encephalitis with a
slow course.
Mingazzini has recently made a fresh investigation of all the
earlier and recent cases of agenesia and atrophy of either half
or the whole of the cerebellum, and came to the following con-
clusions :—
(a] Agenesia of half the cerebellum usually runs its course
without any symptoms whatsoever.
(I)} Unilateral cerebellar atrophy remains latent, when only
the superficial cortex is affected.
456 PHYSIOLOGY CHAP.
(c) When the unilateral atrophy involves the cortex of the
involuted folia, but not the deeper parts, slight and not very
characteristic motor disturbances result ; there is merely slow
progression and a tendency to make backward steps.
(d) Only when the atrophy involves the whole of one-half of
the cerebellum is the characteristic drunken gait and manifest
asthenia of the muscles on the affected side to be seen.
(e) Incomplete bilateral agenesia of the cerebellum seldom
runs its course without symptoms. This, however, occurred in a
case described by Ingels, in which the weight of the cerebellum
was reduced to ^V of the normal. But in the majority of cases
there is ataxia with a greater degree of astasia, or pronounced
ataxia — particularly in the lower limbs — with general asthenia
and astasia, which may appear in the hands and arms in the
form of tremor.
(/) In bilateral sclerotic atrophy the main symptoms of
cerebellar deficiency are seldom absent. Tin- most constant are:
swaying in the upright position (astasia), which compels the
patient to widen his base of support to avoid falling ; a zigzag
gait like that of a drunken man, which is sometimes accompanied
by marked diminution of power (asthenia) in the lower limbs—
rarely in the upper — so that the patient is obliged to support
himself by the walls, seats, or a friendly arm to avoid falling.
These facts, derived from a critical examination of this group
of clinical cases — which is certainly the most important from the
physiological point of view — not only agree with those obtained
experimentally by ourselves in dogs and monkeys, but are a
useful complement to them.
The cases of agenesia that run a latent course seem to us of
the highest value, because they show that if a partial arrest of
development takes place in the cerebellum, such organic adaptations
may come about in the cerebral system as a whole as can wholly
or partially compensate the cerebellar deficiency.
The cases of atrophy which present no symptoms during life, or
only such as are slight and not characteristic, agree perfectly with
the experimental fact that more or less complete organic com-
pensations may occur with surprising rapidity after incomplete
mutilations, symmetrical or asymmetrical, of the cerebellum in
dogs and monkeys.
Evidently when cerebellar disease develops very slowly, it may
attain a considerable severity without any visible symptoms, since
the effects of deficiency are obscured or repaired by simultaneous
organic compensation in proportion as they make their appearance.
It is also plain that the process of organic compensation by the
intact parts of the cerebellum can only take place imperfectly in
cases of bilateral agenesia or atrophy, when the healthy and func-
tioning part of the organ is reduced to a minimum.
vni THE HTND-BEATN 457
Less convincing from the physiologist's point of view is the
larger group of clinical cases of various kinds of tumours in
one or other part of the cerebellum, which, in addition to more
or less extensive destruction of normal tissue, compress the
adjacent organs, beyond the limits of actual disease, particularly
the pons and medulla. It is a priori evident that in these
cases the fundamental phenomena of cerebral deficiency are
masked and to some extent replaced, by irritation or paralytic
phenomena, in proportion with the more or less acute course of
the disease and the extent and degree of the compression exerted
by the tumour on the surrounding parts.
The mechanical effects of compression are easy to recognise.
The crossed hemiplegia and hemiparesis1 seen in certain cases of
tumour of one lateral half of the cerebellum certainly depend on
the compression which the tumour exerts on the motor paths in
the pyramidal fibres of the same side before they cross. The
homolateral paralysis of one or more cerebral nerves by which the
syndrome of cerebellar tumours is sometimes complicated is due
to the same cause.
The symptoms which physicians regard, not without reason, as
the irritative effects of cerebellar tumours are more frequent, more
numerous, and more varied.
One of the most general is intermittent or continuous headache,
which may be localised in the forehead or temples, more often in \
the occiput, particularly close to that part of the cerebellum which '
is the seat of the tumour.
Vertigo in its various forms is another symptom by which the
clinical picture of cerebellar tumours is frequently complicated.
Some regard it as an essential feature of cerebellar diseases ; the
characteristic syndrome of ataxy would thus be only an effect of
vertigo. We learn, however, from clinical observation — which is
in this case of the utmost value since it relates to a subjective
phenomenon — that ataxy may be present without the faintest sign
of vertigo ; that this is almost invariably associated with irritative
and conrpressive lesions of the cerebellum, and is absent in all
degenerative and destructive lesions ; finally, that vertigo is not an
exclusive symptom of cerebellar diseases, but is very frequently
associated with diseases of other parts of the central and peri-
pheral nervous systems.
Vomiting is not uncommonly associated with headache and
vertigo, and may depend on the compression of the bulb or
on the irritation which spreads to the posterior corpora quadri-
"•riuina, where there is a centre for the contractions of the stomach.
O '
The forced movements and attitudes by which vertigo is
constantly accompanied in animals have usually been observed
in clinical cases of compressive and irritative lesions, involving
one cerebellar hemisphere. Eotation and circus movements are
458 PHYSIOLOGY CHAP.
exceedingly rare ; more frequently there is an irresistible tendency
to incline sideways or backwards, with curvature of trunk or neck,
strabismus, nystagmus, etc., so that the patient is incapable not
only of walking, but also of holding himself upright.
Cases of cerebellar tumours are not infrequently complicated
by epileptiform attacks, which may be general and widespread, as
in ordinary epilepsy, or partial and limited to certain groups of
muscles, as in Jacksonian epilepsy. But in cerebellar atrophy of
long standing these epileptiform fits are even more frequent ;
epilepsy cannot therefore be purely and simply the effect of
compression exerted by the tumours.
In tumours with a rapid course this complex of symptoms
predominates, and partly or wholly masks the fundamental
phenomena of cerebellar deficiency. But in most cases the
asthenic, atonic, and astatic symptoms described in animals that
have lost part or the whole of the cerebellum are associated to a
greater or less degree with symptoms due to compression or
irritation of the adjacent organs.
With the exception of cases of agenesia and partial atrophy
with a slow course which may remain entirely latent, the gait in
the vast majority of cases of cerebellar disease due to large or small,
symmetrical or asymmetrical lesions (tumours, haemorrhagic foci,
abscesses, etc.) is what clinicians term staggering, uncertain, and
reeling like that of the slightly inebriated — this is the synthetic
expression of cerebellar ataxy. As in a drunken person, the
oscillations of the body and continual irregular displacements of
the centre of gravity represent the effects of functional deficiency,
while the separation of the feet in walking, the inclination to left
or right, the hurried step forward or stumble back, and the use of
the arms as a counterpoise, are compensatory acts intended to widen
the base of support, lower the centre of gravity, and re-establish
equilibrium which is threatened in one direction or the other.
In asymmetrical or unilateral lesions of the cerebellum the
tendency to fall is in the majority of cases towards the side of the
lesion (seven times out of ten, Adler) ; in bilateral symmetrical
lesions the tendency is usually to fall backwards. Exceptions to
this rule, while conflicting from the clinical point of view, have no
scientific value.
One important clinical result is that the motor disturbances in
cerebellar patients are always far more marked in the lower limbs
than in the upper — as is the case to a marked extent in animals.
In rare cases there is a certain amount of ataxia in the upper
limbs, which is shown in an incapacity for carrying out delicate
movements with the hands.
Still more important is the fact clinically noted by Nothnagel,
Monakow, and others that in cerebellar patients the ataxy of the
lower limbs disappears completely when the patients are lying in
viii THE HIND-BRAIN 459
bed. In this position of stable equilibrium they are capable of
carrying out any movement rapidly and completely. It is rare to
find that one or the other leg, if raised, trembles slightly or
makes shaky or disconnected movements. "When the patient
lies on his back in bed," writes Nothnagel, " the leg-movements
are made quickly and certainly ; the subject has a clear idea of
their position and manages to place one limb actively in exactly
the same place to which the other has been brought passively."
This, which agrees perfectly with experimental observations,
proves that cerebellar patients — like decerebellated animals — retain
on the one hand the complete ability to co-ordinate their move-
ments, on the other the integrity of the muscular sense, that is,
full consciousness of the position of the limbs in space, both during
rest and in muscular activity.
It is curious to note that while v. Monakow expressly admits
that " the phenomena of cerebellar ataxy in man coincide in
essentials with the observations made upon animals," he expressly
denies that asthenia and atonia are essential factors in clinical
cerebellar ataxy.
But it is only necessary to glance through the cases collected
by Adler (1899), the majority of which were tumours in one or other
part of the cerebellum, to see that asthenia, expressed in the words
" weakness " or " paresis " of the muscles of the legs, was expressly
noted in a great number of cases. The most striking are 11 cases
of tumour of one cerebellar hemisphere in which muscular weak-
ness, or even a distinct hemiparesis, was noted definitely in the
homolateral side. In 6 other cases where there is no reference
to the strength of the limbs it is stated that the gait was unsteady
and uncertain, and that the patient had a tendency to fall, or did
fall, towards the side in which the tumour lay. In 8 cases, lastly,
it was noted that the patient was unable to stand or walk, owing
merely to irritative phenomena and vertigo.
In denying the occurrence of atonia v. Monakow repeated
Ferrier's objection that the tendon-phenomenon or knee-jerk was
exaggerated, according to Eisien Russell, in animals after opera-
tions on the cerebellum. He admits that Gowers, Jackson, and
Dercum, on the strength of clinical observations, ascribed a marked
influence on muscular tone to the cerebellum. " But," he adds,
" if observations on the absence of patellar reflex where there are
circumscribed lesions of the cerebellum are not wanting, in other
cases of cerebellar tumour the tendon reflexes are normal. It is
certain that depression of muscular tone involving loss of the
patellar reflex is very inconstant in cerebellar affections in man.
Luciani assumes that the alteration in tone is so delicate that
clinicians do not succeed in detecting it. He himself, however
(as Terrier justly points out), has neglected the very method which
physicians adopt in every case for testing the tone of the muscles,
460 PHYSIOLOGY CHAP.
viz. examination of the tendon reflex, so that the essential basis
of his atonia is wanting." To this argument we replied to Ferrier
in 1895 : " No one has ever demonstrated that the tone of the
muscles bears any relation to the reflexes that can be evoked by
mechanical stimulation of their tendons. I fail to see why a
certain degree of atony should diminish or remove the tendon
reflex ; it even seems to me that it may exaggerate this reflex — if
not in force certainly in its range. It is a fact that exaggeration
of the knee-jerk or patellar reflex is commonly noted by physicians
in cases with cerebellar lesions, apart from the contracture of the
paralysed limb. Since Terrier stated that after removal of the cere-
bellum the patellar reflex in his monkeys was grossly exaggerated
after a few months, he was logically bound to conclude either that
the tendon reflexes are in no way related to the muscular tone, or
that the absence of the cerebellum, far from producing atonia as I
maintain, induces, on the contrary, hypertonia or exaggeration of
muscular tone."
Terrier, and later v. Monakow, did not dispute the facts on
which we founded the theory of astasia. He agreed with us that
the lack of stability or firmness in the limb, both in different
positions and in movement, is seen particularly on the side of the
lesion ; that it is not confined to the muscles of the trunk and
limbs, but extends to all the muscles ; and lastly, that it is
expressed in tremor, unsteadiness, and also in dysmetria of the
movements of the limbs, despite the functional compensation of
which the voluntary motor centres are capable.1
In conclusion, it follows that in the simplest and most typical
cases the clinical symptoms of diseases of the cerebellum in no
way contradict the experimental observations. When the
principal atonic, asthenic, and astatic symptoms of cerebellar
deficiency are absent or indefinite, it should be remembered that
the partial deficiency of the organ may be more or less perfectly
adjusted by a process of organic compensation. In cases in
which the cerebellar disease runs an acute course, and is accom-
panied by vertigo and irritative phenomena, these naturally pre-
dominate, and may disturb the co-ordination of movements so
much as to render the erect posture and locomotion impossible.
1 Mingazzini lias unhappily replaced the term astasia by that which seems to
him more correct of dystasia or dysbasia, by which he means the difficulty which
cerebellar patients find in standing. He has evidently not grasped that the astasia,
or want of stability refers to all voluntary muscles and not merely to the muscles
of the lower limbs, neck and back, which are specially concerned in the erect
posture and in locomotion.
This change in nomenclature, trifling as it seems, may well be a source of
ambiguity, obscurity, and confusion in the physiology of the cerebellum !
Less mischievous, but equally useless, is the substitution for atonia and asthenia
of hypotonia and hyposthenia which some clinicians think more appropriate, as
though it were not obvious that the lack of tone and energy in the muscles must
be understood in a relative sense, just as anaemia signifies not complete deficiency
but comparative poverty of amount of blood circulating.
VIII
THE HIND-BRAIN 461
VII. The hypotheses of the functions of the cerebellum have
developed in three different directions. The first incorrect ideas
of Rolando (1809-28) were modified by Luys, Dalton, and
Weir-Mitchell, and after our own prolonged experimental studies
assumed a definite form, in which the cerebellum is regarded as an
organ of subconscious sensation, which exerts a continuous rein-
forcing action upon the other nervous centres, and on which the
normal tone of the muscles depends. The theory deduced from
the experiments of Flourens (1842), who localised in the cere-
bellum the faculty of co-ordinating the movements of posture and
locomotion, was most fully set forth by Lussaua (1862), who con-
sidered the cerebellum as the centre of muscular sense. Lastly,
according to the hypothesis propounded by Magendie (1825) solely
on the strength of the forced movements of rotation and retro-
pulsion after lateral lesions or symmetrical destruction of the
cerebellar substance, the cerebellum is an organ for maintaining
the equilibrium of the body in the erect posture and in walking. I
This hypothesis was further developed in the work of Terrier (1876),
Bechterew (1884-96), Thomas (1897), Stefani (1887-1903), and
others, who promulgated various conceptions of the intervention
of the cerebellum, in the equilibration and orientation of the body
in space.
Investigation of this last theory is especially important, because
it leads to the discussion of the physiological relations between
the cerebellum and the labyrinth, the peripheral sense-organ
served by the vestibular nerve, which we have seen to be connected
with the cerebellum by means of the nucleus of Deiters.
This is not the place to discuss the complex physiological
doctrine of the end-organs of the vestibular nerve, or labyrinth,
which must be dealt with along with the other sense-organs. It
has been experimentally demonstrated that the nerve-endings of
the semicircular canals and saccules of the vestibulum constitute
an extremely delicate organ of sense, necessary to the preservation
of equilibrium and the orientation of the body in space. Here we
need only insist on the fact which is of predominant importance
for the physiology of the cerebellum, that the proximal and
remote phenomena consequent on unilateral and bilateral destruc-
tion of the labyrinth resemble in no slight degree those which
appear after the unilateral or bilateral ablation of the cerebellum.
Flourens, who was the first to propound a • theory of the
function of the labyrinth (1824-30), recognised the analogy between
the motor disorders consequent on lesions of the semicircular
canals and those which follow cerebellar ablations. The further
investigations of Goltz (1869-79) confirmed and extended the
likeness between the effects of the two operations. Lastly, Ewald
(1887, 1889-92), who investigated the more remote residual
phenomena due to uni- and bi-lateral ablation of the labyrinth,
462 PHYSIOLOGY CHAP.
brought out clearly the almost complete identity of these with the
fundamental phenomena of cerebellar deficiency.
We must confine ourselves to stating that the main symptoms
due to defect of the labyrinth are — according to the minute
observations of Ewald — abnormal relaxation of the affected
muscles, diminished energy during activity, and diminished pre-
cision of the movements in which they are concerned. All the
special symptoms which animals without a labyrinth present in
comparison with normal animals can easily be interpreted as the
effects of atonia during repose, and of asthenia and astasia during
muscular activity.
The symptoms of the early post -operative period are also
phenomena of deficiency, as recognised by Flourens, and are
accordingly of the same character as the residuary symptoms of
the later period. This appears from Ewald's work, and still more
obviously from the researches of Gaglio (1889) on the effect of
cocainisation of the membranous labyrinth. When cocaine is
applied to the divided semicircular canals all the motor disturb-
ances consequent on the lesions persist, while if the canals are
intact it produces for a period of thirty to sixty minutes the same
effects as result from cutting or destroying them.
The difference in the motor disturbances in animals a short
time and a longer period after loss of the labyrinth is only
quantitative, and is due to the intervention of compensating
phenomena. Ewald showed that after almost total disappearance
the motor disorders consequent on destruction of the labyrinth
reappeared after removing the motor zone of one cerebral hemi-
sphere, and return in their original intensity and persist after
removing both motor regions, so that the parallel is almost
complete between our studies on the cerebellum and those of
Ewald on the labyrinth.
The fact that the motor disorders produced by destruction of
the labyrinth are phenomena of deficiency led Ewald to conclude
that these peripheral sense-organs normally send a continuous
excitation to the nerve-centres, which reaches the muscles reflexly,
keeps up their tone, and thus makes their normal function
possible.
What are the centres through which the labyrinth reflexly keeps
up muscular tone ? Owing to the great resemblance between the
phenomena of labyrinthine and cerebellar deficiency, it seems
legitimate to conclude that the labyrinth exerts its tonic action
on muscle through the cerebellum. Ewald, however, is not
in favour of this conclusion, on the strength more particularly of
the experiments of his pupil Lange, who demonstrated that in
pigeons which had been deprived of their cerebellum some time
previously lesions of the labyrinth induced the same character-
istic phenomena as were observed when the cerebellum was intact,
viii THE HIND-BEAIN 463
and that in pigeons which had some time previously lost their
labyrinth the removal of the cerebellum was followed by incapa-
bility of standing, and all other disorders noted when this
operation is performed on the normal pigeon. But in a later
critical study (1903) Stefani rightly points out that if the
phenomena of labyrinthine deficiency can be evoked on de-
cerebellated animals, this only shows that this sensory organ
influences not merely the cerebellum, but other centres also ;
and if the phenomena of cerebellar deficiency appear in animals
that have no labyrinth, this means that cerebellar activity is
maintained not merely by the impulses coining from the labyrinth,
but also by those other multiple afferent paths which anatomy
has shown to be directly or indirectly in relation with the
cerebellum.
In order to bring out the special physiological importance of
the vestibular nerve, in so far as it is related to the cerebellum
and concerned in its functions, Stefani refers to his earlier ex-
periments with Weiss (1877), which showed degenerative alteration
of Purkinje's cells in the cerebellum of pigeons after destruction of
the semicircular canals. Since this result was not confirmed by
other observers, Stefani (1899) induced his pupil Deganello to
repeat these experiments with the methods of Marchi and Nissl.
These new researches not only confirmed the preceding results,
but brought out other degenerative changes in the bulb, which
are highly interesting for both anatomy and physiology.
Since Purkinje's cells are the principal element of the cerebellar
cortex, a localised degeneration round these in all the lamellae,
on one or both sides, as occurs after unilateral lesions > of the
labyrinth (according to Stefani and Deganello), can only mean
that the activity of the cerebellum is due mainly, if not exclusively, 1
to the impulses transmitted from the labyrinth.
While fully agreeing with Stefani's facts, we are unable to
subscribe to the theory which regards the cerebellum as the organ
for equilibration and orientation of the body in relation to its
environment. Neither the cerebellum nor the labyrinth, in so far
as it is in relation with the cerebellum and influences its activity,
has this special function, though undoubtedly both combine with
other centres to preserve equilibrium and orientate the body
in space. Ewald, who is the most competent authority on the
physiology of the labyrinth, expressly admits that the continuous
reflex action of the labyrinth on muscular energy and tone is
the main function of this organ, and that in virtue of this rein-
forcing action (which may oscillate more or less according to the
displacement of the centre of gravity of the body) the labyrinth
participates in the complex functions of orientation and equilibrium.
Goltz (1870) held the labyrinth to be the organ for perception
of the position of the head, and fundamentally important to
464 PHYSIOLOGY CHAP.
equilibrium, and he considered the motor disturbances which
follow lesions of the semicircular canals to be the effect of defective
or fallacious sensations of the position of the head, due to sup-
pression or alteration of the normal displacements and oscillations
of the pressure of the endolymph in the semicircular canals, by
which the ampullar nerve-endings are excited. It was, however,
demonstrated by Cyou (1897) and confirmed by Gaglio that under
certain experimental conditions the endolymph may be entirely
drained away without producing- any disturbance of equilibrium.
At the same time Cyon's hypothesis that the semicircular
canals are the peripheral organ of space -perception is unproved,
as will be shown in Chapter II. of the next volume. As Gaglio
aptly observes, " We explore space with all our senses, and it is
the sum of the impressions which they make on our nerve-centres
that arouses in us the consciousness of relation, of the position of
equilibrium, and of the movements of our body in respect to the
environment."
The principal function of the labyrinth is — in Ewald's ex-
pression, already used by Hogyes — its tone, by which muscular
tone is reflexly controlled ; and no other hypothesis is needed to
explain the motor disorders consequent on section or destruction
of the semicircular canals. The disturbance • of the muscular
functions is so prominent that Ewald and many others before and
after him have called attention to it, and, as Gaglio remarks, it
is this which has led the observer so far from the truth.
If we examine the theories of the physiology of the cerebellum
we find the same fallacy. Abstract ideas of equilibration, orienta-
tion, co-ordination, for a long while prevented attention from
being directed to the essential phenomena.
In 1886 Ferrier, starting from the fact that the activity of
the cerebellum persists intact after removal of the cerebral hemi-
spheres, declared that organ to be independent of consciousness
and will, although he held it to be normally associated with the
activity of the fore-brain, since disturbances of equilibrium in a
given direction will under normal conditions provoke conscious
or voluntary efforts of a compensatory character in the opposite
direction. The same adjustments effected by the cerebellum may
therefore be carried out by the fore -brain independently of it.
The effects of cerehellar lesions were designated by Ferrier paralysis
of reflex adjustments, and are to be carefully distinguished from
paralysis of spinal and cerebral reflexes, which never results from
uncomplicated cerebellar lesions ; so that in 1886 Ferrier looked
on the cerebellum merely as a centre in which a very complex
mechanism for unconsciousequilibrationwa,sdevelopQd during phylo-
genetic evolution. But as the cerebrospinal axis already in itself
contains mechanisms which are capable of reacting to each displace-
ment of the equilibrium of the body by appropriate instinctive
vin THE HIND-BEAIN 465
or voluntary reflexes of a compensatory character, capable of
replacing the body in the normal position of equilibrium, it is
obvious that equilibration of the hody in space is not a specific
function, attributable to this or that part of the system, but a
complex /unction, dependent on the intimate organisation and
functional harmony of the system as a whole.
The i IK K if that cerebellar ataxy is not due to defective equi-
libration in space, but to the asthenic, atonic, and astatic neuro-
muscular state, is the fact that then1 is a period or stage of
cerebellar ataxy during which the animal is incapable of walking
or falls at every step, although it is still quite capable of floating
and swimming perfectly in the water — where equilibration is
much more difficult -- without losing its equilibrium, and of
regaining it promptly if it is lost, and further of readily altering
its direction by appropriate compensatory acts in order to get
near the edge of the basin and climb out (Luciani).
In order to discredit this observation, it was suggested that
" the movements required in swimming in water are not
necessarily so exact as those of walking " (Murri). Obviously the
everyday fact has been overlooked that every normal person
knows how to walk, while many have never learned to swim and
cannot keep themselves afloat in water without drowning.
The publication of our Monograph, The Cerebellum (1891), had
an undoubted influence 011 Ferrier. In reviewing our work
(Neurological Society of London, 1894) he no longer spoke of the
cerebellum as an organ of equilibration, nor as a collection of
unconscious centres of reflex action destined to come into play to
restore the equilibrium of the body as soon as it is menaced in
any given direction. He admitted, on the contrary, that the cere-
bellum exercises a constant influence (directly or through the
other cerebrospinal centres) upon the motor systems of the
animal machine, adding that " even, however, if we assume that
this is the true formula for the influence of the cerebellum it still
remains to be determined how its activity is called into play and
brought to bear on the muscles, either in association with the
cerebrum or independently."1
In his earlier work Stefani applied Goltz' theory of the semi-
circular canals to the cerebellum, and maintained that " the cere-
bellum may be regarded as an organ which utilises the impulses
sent out from the semicircular canals to acquaint the animal
with the position of its head in relation to the environment."
The decerebellated animal is not able to keep its head in the
normal position because it has lost consciousness of its position.
When it wants to carry out some movement its head oscillates in
all directions and the centre of gravity is displaced to one or
the other side, while the animal reacts to these displacements by
1 Ferrier, Brain, 1894, vol. xvii. p. 37.
VOL. Ill 2 H
466 PHYSIOLOGY CHAP.
appropriate compensation movements directed to the maintenance
of its equilibrium which cause the irregularity of its gait.
In a later publication (1903) Stefani came back on his old
theory, and recognised that it was inadequate, and that " in the
actual state of our knowledge the best hope of completing it lies
in blending it with the, theory of Luciani, who regards the
cerebellum as the centre of muscular tone. Luciani has demon-
strated the existence of a cerebellar tone, Ewald the existence of a
labyrinthine tone. To complete the two theories and fuse them
into one we need only assume that the cerebellar tone, as demon-
strated by Luciani, arises in the labyrinth, and is therefore adapted
to the requirements of equilibration and orientation, as already
suggested by Dreyfuss in Germany and Gaglio in Italy."
It is not, however, a matter of indifference whether the cere-
bellum is termed the organ of equilibrium, or of orientation, or of
tone. The tonic reflex activity controlled by the cerebellum is
not merely exerted on the muscles that function during posture
, and locomotion, but it extends more or less to all the skeletal
muscles whatever their function. In moving the eyes, in speaking
or singing, in writing, playing the piano, sitting down, in all these
actions there must certainly be intervention of the tonic influence
of the cerebellum, although the resulting movements are quite
different in character from those of equilibration. Again, when
standing and walking the cerebellum intervenes less as the organ
for preserving equilibrium than as the organ which regulates the
tone and contraction of the muscles to the right extent and in the
proper combination. Stefani is unfortunate in citing Gaglio in
support of his hypothesis ; for the latter expressly denies Goltz'
theory that the head possesses a special sense of equilibrium in
the labyrinth, " since the general conditions of sensibility which
control the sense of equilibrium in other parts of the body must
suffice."
VIII. In The Cerebellum (1891) we made a comparison between
the primitive rudimentary theory of Eolando and that of Flourens,
and expressed the following opinion, which we still hold to be
legitimate : " Eolando looked upon the disturbance of co-ordination
as the effect of partial destruction of the cerebellum, owing to
which there was unequal and irregular transmission of the normal
influence of the cerebellum to the different parts, and he erroneously
characterised the asthenia as paralysis. Flourens fortunately
avoided this error ; he expressly defines as weakness what Rolando
termed paralysis, but erred in regarding not this weakness but
the inco-ordination of movements as the main symptom of the
loss of the specific function of the cerebellum. In an animal
deprived of its cerebellum, he says, ' tons les mouvements partiels
subsistent encore ; la co-ordination seule de ces mouvements est
perdue.'
vni THE HIND-BRAIN 4G7
"Rolando's error was easily corrected by more careful observa-
tions ; that of Flourens opens a false track to subsequent workers,
and has become a serious obstacle to advance in the physiology of
the cerebellum. Rolando's view led him logically to the other error
of considering the cerebellum as an organ subservient to sensation
(through the agency of the medulla oblongata) or to the will (through
the agency of the cerebral hemispheres) ; the mistake of Flourens
led him to create an abstract and fictitious entity, the principle of
co-ordination or regulation of complex movements or postures, as
represented by the various forms of locomotion or position — a
principle localised in the. cerebellum, and independent of the
cerebrum, as the function of the latter remains intact after removal
of the cerebral hemispheres.
:' However fallacious and poorly founded, Eolando's theory
in itself is clear, definite, and complete in fundamentals, while
that of Flourens is obscure, imperfect, and unintelligible, since it
is impossible to picture in what the supposed co-ordinating or
regulating functions of the cerebellum can influence locoinotor
movements, which are willed by the cerebrum and carried out by
the medullary axis ; nor how this regulation can take place when
once the functional independence of the cerebrum and cerebellum
has been admitted."
Lussana, who considered the cerebellum as the centre of
muscular sense, offered an explanation of the phenomena of cere-
bellar deficiency described by Flourens that was ingenious in its
simplicity.
' For a long time " (he wrote in 1862) " the importance of this
(muscular) sense, through which the muscles effectively carry
out their voluntary movements, has been recognised. It will
suffice to quote two physiologists of undoubted authority, Bell and
Panizza. The former recognises that by sensory impressions we
can appreciate the degree of contraction of our muscles, and
are able by this means to regulate their activity in proportion
to the resistance which we have to overcome. In 1834 Panizza,
who described ataxia after section of the dorsal spinal roots,
wrote : The influence of the will on the muscles that are partially
deprived of sensibility is feeble and uncertain, because they no
longer feel and are no longer felt."
" The muscular sense " (adds Lussana) " is par excellence the
main factor in co-ordinating voluntary movement ; its central
organ is the cerebellum. Far more important and indispensable
than the cutaneous sense, the muscular sense serves in animals to
make known the resistance met with, and in voluntary movements
to regulate the forces of contraction by which the muscle is able
to overcome it. ...
• Without the cerebellum the animal no longer feels the solidity
of the earth on which it rests in standing and walking, nor the
468 PHYSIOLOGY CHAP.
resistance of the medium in which it flies or swims ; it does not
recognise the impenetrability of the objects which obstruct its
course ; it does not feel the weight of the body it has to carry ; this
is the physiological explanation of the disturbance of voluntary
movement described by Flourens. ' Le cervelet,' says this author,
' est le siege exclusif du principe qui co-ordonne les mouvements
de locomotion.' The true function of the cerebellum, in short, is
the muscular sense."
Undoubtedly Lussana's theory is an ingenious completion
and development of that of Flourens, save for his assumption
that the cerebellum is not the seat of any sensation. His hypo-
thesis is so lucid that it might find general acceptance were
not one thing — direct experimental evidence for it — lacking.
As a matter of fact, the occurrence of the staggering and reeling-
gait, and other locomotor disorder in decerebellated animals or
in diseases of the cerebellum is not enough to establish loss or
disturbance of muscular sense, because the normal regularity of
the movements does not depend exclusively upon the muscle sense.
In 1903 a pupil of Munk — Lewaudowsky — again assumed
the cerebellum to be the centre for muscular sense, and claimed
that the phenomena of cerebellar ataxy consist in disorders of
co-ordination.
As we have already given definite proof that both in animals
after removal of the cerebellum and in disease of this organ in
man the muscular sense is not in any way altered, it is
unnecessary to discuss this hypothesis again. But the position
taken up by Lewandowsky may detain us for a moment.
He agrees that the generic term ataxy does not express a
unitary concept, but is simply a complex represented by certain
disorders of movements, or motor paralysis. " If," he adds, " a
definite concept were attached to the term ataxy, there would
be no ground for dispute as to what is meant by cerebellar ataxy."
Again, when we say that the animal or man whose cerebellum
is affected has an uncertain, reeling, swaying gait, similar to that
of a drunkard, we express, not a single phenomenon, but a
complex, which may be split into a number of components.
What are the simple components of cerebellar ataxy for
Lewandowsky ? He verih'es the occurrence of astasia, atonia,
and neuro- muscular asthenia, which we have described and
demonstrated in various ways. He recognises the atonia by the
fact that the limbs of decerebellated animals can be flexed or
extended not only more readily than, but also beyond the range
of, the normal. He also describes asthenia, but does not admit
that it is due to defect of the stkenic action of the cerebellum.
He assumes that the complex movements only appear less
energetic because the synergic and co-ordinated actions of all
the muscles that come into play in the various voluntary move-
VIII
THE HIND-BEAIN 469
are lacking in decerebellated animals ; in a word, asthenia
is for him a result of disturbance of the co-ordination of the
movements.
As evidence for this loss of co-ordination Lewandowsky
adduces the phenomenon which wre described minutely under
the name of dysmetria, as expressed in the so-called hen's gait.
Lewandowsky regards this symptom, which can also be seen after
section of the dorsal spinal roots and in tales dorsalis, as all-
important. Asthenia, atonia, ataxia, fall into the second place ;
they are not fundamental phenomena of cerebellar ataxy, but
are merely secondary to dysmetria and to the imperfect co-
ordination of the voluntary movements, which in its turn is due
to disturbance of the muscular sense !
"Luciani," he adds, "has not been able to clear up the
symptoms in cerebellar ataxy, because he overlooks one effect of
cerebellar lesions which we should place, in the first rank—
i/ffi'i-ofions of the muscular sense. While Luciani, after thousands
of experiments, has never ol (served disturbances of the muscle
sense, we, on the contrary, say that every motor trouble due to
cerebellar lesions is accompanied by it."
This view, which is denied by most authoritative observers,
compels Lewandowsky to admit :
(a) That the cerebellum is not the only central organ of
muscular sense, as the cerebral cortex also participates :
(&) That it does not represent an intermediate station on the
paths of muscular sensibility running to the brain, but that there
are direct paths between the cerebrum and the spinal cord, which
are unconnected with the cerebellum;
(c) That there is both conscious and subconscious regulation of
movement by the muscular sense; that the cerebrum attends to
conscious regulation, while the cerebellum has no other task
than that of controlling and directing the subconscious move-
ments !
But these conclusions invalidate all his previous statements :
if the cerebellum is not the seat of conscious sensations, cerebellar
ataxy obviously cannot be a sensory ataxy like that which is
seen after section of the roots and in tabes, nor is the cerebellum
a centre, for the muscle sense. If the spino-cerebral sensory
paths are unconnected with the afferent spino-cerebellar paths, it
is clear that decerebellated animals cannot exhibit disturbance of
the muscle sense, since the spino-cerebral paths that transmit
the impressions of the state of the muscles to the cerebral
centre are intact; it is accordingly absurd to assume that the
dec.erebellated animal does not perceive and correct abnormal
positions of its limbs, if it be once admitted that the cerebellum
is not the seat of conscious sensations.
It must be admitted that dysmetria of movement can be
470 PHYSIOLOGY CHAP.
variously interpreted. In 1883 Schiff considered it to lie one
of the essential elements which, along with asthenia, make up
the syndrome of cerebellar ataxy. But he rejected the hypothesis
that dysmetria depends on defective co-ordination, as Lewaud-
owsky holds, nor did he regard it as an effect of the loss of the
inhibitory action of the cerebellum, as assumed by Budge in
1841 and by Wagner in 1858 ; he attributed it to irregularity in
the reinforcing action transmitted from the remaining portion of
the cerebellum to the group of muscles which come into play in
the different complex voluntary actions. Babinski, who accepted
this, called it cerebellar a-syneryy.
Schiff's view seems acceptable in cases of incomplete extirpa-
tion or pathological states of the cerebellum, but in cases of
complete extirpation of one lateral half, or of the whole cere-
bellum, his interpretation is not adequate. It must further be
added that dysmetria is not constant in all cases of cerebellar
lesion ; even in clinical cases it is a rare symptom.
As already stated, it is probably due to idonia of the muscles
of the limbs, owing to which there is a too rapid relaxation of
the extensors when the flexors contract, and a too rapid relaxa-
tion of the flexors when the extensors contract. Lewandowsky
did not admit this simple explanation, according to which
dysmetria is a natural consequence of atonia.
IX. We must now consider the function of the afferent im-
pulses that reach the cerebellum from the numerous afferent
paths, and the influence of those it transmits to its efferent paths.
These are the main 'problems on the solution of which the
physiology of the cerebellum has to rest.
One of the most striking and really fundamental facts bearing
on these problems, which finds confirmation both in physio-
logical experiment and in clinical observations, is that profound
alterations and absolute loss of the cerebellum do not paralyse
either sensation or volitional movement, although it has been
clearly demonstrated that this organ is related by its afferent
paths to the peripheral sense-organs (especially the cutaneous,
muscular, and labyrin thine senses), and by its efferent paths to the
peripheral apparatus for voluntary movements. While lesions of
other cerebrospinal centres result in true paralysis — complete or
incomplete — of sensation and motion, cerebellar deficiency is shown
in simple neuro-muscular atonia, asthenia, astasia.
In order to explain these differences, we are naturally led to
make certain conjectures, which are in no way at variance with
anatomical facts, and which harmonise well with physiological
research as a whole :—
(a) That the cerebellum with its appendages constitutes a
small and comparatively independent system in itself, so that its
removal interrupts no important conducting paths, centripetal or
vin THE HIND-BRAIN 471
centrifugal, between the brain and the peripheral organs of sensa-
tion and motion ;
(b) That it has no field of action of its own, i.e. belonging to
itself exclusively, which is not equally at the service of other
centres of the cerebrospinal system ;
(c) That it is not a sensory centre properly so called, as the
sensory impressions which reach it by special afferent paths arouse
no conscious sensations, but normally remain subliminal, below
the threshold of consciousness ;
(d) That under the special conditions in which its activity is
concerned, it may be regarded as a small coadjutant system to
reinforce the great cerebrospinal system.
In agreement with the recent morphological and phylogenetic
investigations of Bolk, there is ample physiological demonstration
that the cerebellum is a single unpaired organ, each portion of
which has the same function as the whole. In fact the loss of
the vermis may be repaired, i.e. organically compensated, by the
lateral lobes, and after various cerebellar lesions, symmetrical
or asymmetrical, circumscribed or diffuse, the phenomena of
deficiency differ not in their nature and character, but solely in
intensity, extent, and duration, and by their more or less marked
influence on the muscles of one or other side of the body. Our
own investigations proved clearly and decisively that unilateral
mutilations have a predominantly homolateral effect, i.e. much
more marked on the muscles of the same side, and not only on the
muscles that subserve posture and locomotion, but on all the
voluntary muscles and in particular on the muscles of the lower
or posterior limbs, and on the muscles that fix the vertebral
column.
If the principal effects of cerebellar deficiency consist in atonia,
asthenia, and astasia, it follows logically that the coadjutant or
reinforcing influence that the cerebellum normally exerts upon the
rest of the system consists in a tonic, sthenic, and static neuro-
muscular effect by which—
(a) The degree of tension at which the neuro-muscular organs
remain during functional pause or rest is increased (tonic action) ;
(6) The energy developed during the various voluntary, auto-
matic, and reflex actions is increased (sthenic action) ;
(c) The rhythm of the elementary impulses of which these acts
are made up is accelerated, and their normal fusion and regular
continuity is maintained (static action).
If it be once allowed that dysmetria of movement is a constant
phenomenon of cerebellar deficiency ; if, as Lewandowsky has
maintained, dysmetria is one of its essential and necessary phenomena,
and not a simple result of atonia or astasia, then we must add a
fourth factor. The tonic, sthenic, static effects must be supple-
mented by an adaptive action, on which the range, precision, and
472 PHYSIOLOGY CHAP.
adaptation to end of the several voluntary, automatic, and reflex
acts must depend.
Can the cerebellum exert an adjusting effect on the functions
of the motor organs without being an organ of conscious sensation ?
We need not hesitate to reply to this question in the affirmative,
since all the elements of the nervous system, not excluding those
of the sympathetic, are usually credited with this adaptive capacity,
which may in a wide sense lie termed the regulating or co-ordinating
faculty ? By what mechanism is this exerted ? Unless we accept
with Flourens an abstract co-ordinating or regulating function in
the cerebellum, the only alternative is that the precision and
accurate range of movement result from the precision and accurate
adaptation of its tonic, sthenic, and static influence.
The first fact that strikes every one who investigates the
intrinsic differences in the three main physiological functions of
the cerebellum is that they are so much akin, so intimately
connected in their origin, that it is practically impossible to
consider them separately and apart. Astasia, in which the
deficiency of static action is expressed, is usually held to be a
natural effect of asthenia (Tremitus a debilitate); asthenia, by
which the loss of sthenic effect in the activity of the muscles is
expressed, appears to be related to the atonia observed during their
repose. As, however, it is very difficult to demonstrate the relative
degree of the three phenomena in decerebellated animals, and as
it is not only atonia or asthenia or astasia that is the most
pronounced or obvious symptom in such animals, it may be
assumed — as we said in 1891 — that there are only three different
extrinsic manifestations of a single process, though there may be
no constant relation between their relative intensities.
In addition to the tonic, sthenic, and static functions, which
may collectively be referred to as the "action of reinforcement,"
the cerebellum normally exercises a direct or indirect trophic
action on the organs with which it is in relation. Direct trophic
influence is demonstrated by the degeneration and sclerosis that
follow ablation of the cerebellum, as shown by the work of Luciani
and Marchi, and that of Mingazziiii, Turner and Ferrier, Thomas,
Probst, and others. Indirect trophic action is seen specially in the
muscular changes observed in cerebellar ataxy, the retarded growth
of the cutaneous elements, particularly in the skin, and the lowered
resistance of decerebellated animals to the injurious action of
external agents, so that they succumb to disease more readily
than the intact animal, and have a shorter life in comparison.
The trophic and functional influences obviously represent the
two sides — internal and external — of one and the same physio-
logical process, the intimate nature of which is unknown to us,
and of which we perceive only the most striking and obvious
effects.
vin THE HIND-BE AIN 473
Both tlu1 trophic and the tonic influences are continuously
excited by the duvet and indirect paths that carry impulses to
the cerebellum from the cutaneous, muscular, and labyrinthine
sense-organs. Of these afferent paths that serve, the activity of
the cerebellum, particular importance attaches to the vestibular
nerve, which transmits tonic impulses from the labyrinth by way
of the nucleus of Deiters, as demonstrated by Ewald, Gaglio,
Stefani, and Deganello. It must be abmitted that the demonstra-
tion of the special influence which the labyrinth exerts on the ,
functions of the cerebellum is the only new fact of real importance \
that has been added to the physiology of this organ.
X. In conclusion we must recapitulate the new morphological
theory of the cerebellum, which Bolk has constructed on the basis
of an interesting phylogenetic and ontogenetic comparison between
the brains of different mammals and man.
From the phylogenetic point of view, the cerebellum of all
mammals consists of two lobes, one anterior, the other posterior,
divided by a primary sulcus. The anterior lobe always forms a
single unpaired median organ; the posterior lobe is subdivided
into four lobules, two median and two lateral, which are separated
by secondary sulci.
From the ontogenetic point of view, Bolk distinguishes four
centres of development, two median and two lateral, characterised
by varying rapidity of growth, during which the lobular arrange-
ment of the adult cerebellum is determined by means of numerous,
mainly transverse sulci.
On studying the developmental variations of the single lobes
or lobules of the cerebellum in different mammals, Bolk noted a
more or less definite relation between them and the degree of
functional development of special groups of muscles ; this led him
to attribute the functional control of special muscular complexes
to certain lobules.
We must confine ourselves to the main features of the
functional localisations in different lobules of the cerebellum,
based on the ingenious deductions made by Bolk from his morpho-
logical studies.
He starts from the fact that in certain movements the
muscles on both sides come into action, and in other parts of
the body the muscles of one side are capable of the most complex
movements, while those of the other side may remain altogether
inactive.
The head and neck are certainly included among the former.
In the head are the external muscles of the eyes, the masticator
muscles, the mimic facial muscles, the lingual, pharyngeal, and
laryngeal muscles, which nearly always function bilaterally. In
the neck, again, the muscles that effect the various movements of
the head enter into bilateral activity. The muscles of both the
474 PHYSIOLOGY
CHAP.
head and neck must, according to Bolk, be influenced by the two
separate median segments of the cerebellum.
In the upper and lower limbs the case is different. We know
that each limb is able in man to execute a great variety of more
or less complex movements, independently of the limb on the
opposite side. But this independence is not always complete and
absolute. Learners of the piano and violin have by practice to
overcome great difficulties in order to render the muscles of the
two sides independent, and to avoid the simultaneous contraction
of the homologous muscles of the upper limbs. Bolk infers from
this that in order to regulate the movements of the limbs there
must be three distinct centres in the cerebellum : one unpaired
for synergic bilateral movements ; two paired for the dissociated
movements of each limb.
Finally the trunk muscles specially employed in the respiratory
movements, and in equilibration during the erect posture and in
locomotion, must, according to Bolk, be represented in the cere-
bellum by one unpaired median, and two lateral centres.
Which cerebellar lobes represent these hypothetical centres
that can be distinguished, according to Bolk, in the cerebellar
cortex ? He begins by pointing out that the lobes and lobules of
the cerebellum, as above indicated, are really arranged one above
the other, like the corresponding muscular areas of the body. On
the basis of this correspondence we may assume that :—
(a) The lobulus anterior contains the centres for the muscles
of the eye, jaw, face, tongue, pharynx, larynx, that is, all the
muscles of the head region ;
(b) The lobulus simplex contains the centre for the muscles
of the neck ;
(c) The upper part of the lobulus medianus posterior represents
the median centre for the associated movements of the two
extremities ;
(d) Each of the lobuli ansiformes or paramediani contains the
lateral centres for the dissociated movements of the two limbs,
the crus prirnum being more exactly the centre for the fore or
upper limbs, the crus secundum and lobulus paramedianus that for
the hind or lower Limbs ;
(e) The lower part of the lobulus medianus posterior includes
the centres for the respiratory and perineal musculature ; the
formatio vermicularis the centres for the trunk muscles ; and the
lobulus petrosus the centre for the muscles of the tail.
This arrangement is represented in Bolk's diagram of the
mammalian cerebellum, which is reproduced in Fig. 239.
According to Bolk this hypothetical functional localisation in
the cerebellum is confirmed by correlation of the development of
the lobes and lobules, respectively, in different mammals with the
functional development of the corresponding groups of muscles.
VIII
THE HIND-BKAIN
475
For an exact description of these, the student must refer to Bulk's
original monograph.
We shall now see how far Bolk's inductions — founded on com-
parative anatomy — have been confirmed by physiological experi-
ment, either by the method of electrical, mechanical, and chemical
stimulation of different parts of the brain, or by the removal of
single segments.
After Hitzig and Fritsch had demonstrated the possibility of
localising certain motor centres in the cerebral cortex by electrical
stimulation (Chap. X.) Ferrier (1879) made use of this method,
not merely in developing the theory of cerebral localisation, but
also in attempting to extend it to the cerebellar cortex. The
f'JoFfilfttS
' formatio vermicularis
FIG. 239.— Diagram of lobules of mammalian cerebellum. (After Bolk, simplified by van Ryriberk.)
Left side of figure gives Bolk's new terms for the lobules ; right side, the probable localisation,
according to Bolk, of the relation in different mammals between lobular development and
the functional development of different groups of muscles.
motor effects which Ferrier obtained by faradisation of various
points of the surface of the cerebellum in the ape consisted in
associated movements of the eyeball to the right or left, upward
or downward, according as the stimulus was applied to the right
or left half, or to the anterior or posterior part of the median
lobe of the cerebellum. Movements of the head, as well as certain
abrupt movements of the limbs on the side excited, were often
associated with those of the eyes.
Ferrier's results were not, however, confirmed by Mendelsohn
with induced currents. Ferrier employed such strong currents
that they may have spread to adjacent regions, as the corpora
quadrigemina, pons, bulb.
Nothnagel (1876) performed a number of experiments on
rabbits with mechanical stimulation, by running a needle into
different points of the cerebellar cortex. Among the effects of
476 PHYSIOLOGY CHAP.
this stimulation he noted rhythmical movements of one fore-limb,
movements of mastication, arching of back, etc. But these effects
were not exactly localised, although Nothnagel affirmed a certain
relation between the points at which the needle was inserted and
the reaction.
Pruss (1901) attributed much importance to the direction of
the currents (ascending, descending, transverse) in the results
obtained by electrical stimulation of the cerebellar cortex. The
conclusions he arrived at in regard to cerebellar localisation
would be highly important if they could be accepted. But he
himself states that the currents which he employed to provoke the
reactions described were excessive.
Negro and Eosaenda (1907) repeated these experiments upon
the rabbit's cerebellum with moderate faradic currents. On
stimulating the area which corresponded approximately to the
crus p/'i in tun of Bolk, they obtained unilateral contractions of the
facial muscles and anterior limb, which were sometimes isolated,
sometimes associated. Only when the current was unduly strong
did the reactions extend to the muscles of the two sides. With
unipolar stimulation they obtained more accurate localisation ol
the facial and fore -limb muscles, and found that the facial
centre lies more forward than the centre for the fore -limb.
Both lie somewhat internally, but their exact position was not
determined.
Horsley and Clarke (1908), in a series of researches carried
out with more accurate methods, were able to demonstrate
that the stimulation had to be of enormously greater strength to
obtain motor reactions in faradising the cerebellar cortex than
was required to excite the cerebral motor centres; and that
even strong currents are not effective when the method of
bipolar excitation is employed. They came to the conclusion that
the cerebellar cortex is practically inexcitable ; that when motor
reactions are obtained, these are due to spread of the stimulus
to the subjacent nuclei of grey matter (dentate nucleus, roof
nucleus, Belters' nucleus, etc.), and, finally, that the results
obtained by previous observers were attributable to some fallacy.
Pagano (1904) investigated cerebellar localisation by means of
chemical stimuli, and employed minute interstitial injections of a
solution of curare, because — as previously noted by Tillie — this
poison has a decidedly exciting action upon the nerve-centres.
He succeeded in mapping out four distinct motor centres in
the cerebellum f< >r the muscles of different regions :—
(a) A paired centre for the fore-limb, lying near the crus
primum of Bolk.
(&) A paired ^centre for the hind-limb, near the crus secundum.
(c) An unpaired centre for the muscles of the neck, lying in
the lobulus simplex.
VI 11
TTIE HIND-l'.ftAIN 477
(d~) All unpaired centre for the. muscles oi' the back, in the
lowest part of the lobulus medianus ])osterior.
These results approximate closely to Bolk's diagram of localisa-
tion ; hut the inadequacy of Pagano's method for any exact
determination of the cerebellar centres may be concluded both
from the inconstancy and the variability of the reactions excited
by the curare at the different points of injection, and from bis
own observation that a deep. injection of curare into the lobus
anterior causes violent excitation of almost all cerebral centres,
with varied sensory and motor manifestations termed by Pagano
psychic strychninism or motor delirium, which rapidly caused the
death of the animal.
These studies of the effect of poisons, applied to the cerebellum,
were continued in our laboratory by Magnini under Baglioni's
guidance (1910). Baglioni's previous work had proved that local
application of weak solutions of carbolic acid affect electively
the motor elements of the spinal cord, and solutions of strychnine
the sensory elements of the whole nervous system (p. 264 et seq.~).
It was therefore hoped that by employing these two poisons as
chemical stimuli of the cortex and deep parts of the cerebellum,
it might be possible to obtain facts of importance for the theory
of cerebellar localisation.
But the results were disappointing, though they brought into
prominence symptoms which demonstrated the specifically different
nature from the corresponding elements of the cerebrospinal axis
of the afferent and efferent elements of the cerebellum.
Carbolic acid, applied to the cms primum and secundum of
the cerebellum, in any strength of solution (T3-6 per cent on
discs of filter paper) has no immediate effect. This means that
the cerebellar cortex, so far as we know, either contains no motor
elements, or these are specifically different in character from the
spinal motor elements.
Strychnine, when applied to the lobulus medianus posterior,
lobulus parainedianus, or crus secundum, either to the surface or by
injection, produces no special symptoms, according to the various
regions excited, but only more or less general movements of the
head, neck, trunk, and limbs of the side homolateral with the
stimulation. Application by discs of filter paper either produces
no effect or mere twitches of the facial muscles. Superficial
injections merely lead to raising of the fore -leg on the same
side, blepharospasm, salivation with rhythmical movements of the
jaw, tonic contraction of the two limbs on the homolateral side,
with tactile hyperaesthesia of the skin of the homolateral side of
the face.
These results, while they do not disprove the concept of
localisation in the cerebellum, give no decisive argument in favour
of it. The amount of strychnine used to evoke these phenomena,
478 PHYSIOLOGY CHAP.
of excitation (1-2 per cent solutions) far exceeded that required to
evoke the typical spasms, when applied to the excitable zones of
the cerebral cortex and the dorsal horn of the cord. The more or
less diffuse symptoms of irritation are similar to those produced
by applying the poison in minute doses to adjacent parts of the
bulb. It is probable that the effects observed are due to the
spread of the poison to the centres in the dorsal surface of the
bulb, and consequently that the afferent elements of the cerebellum
are different in their nature from those of the cerebrospinal axis.
The same negative results were obtained by Beck and Bikeles
(1912) on repeating these experiments with superficial application
of carbolic acid and strychnine.
More exact results in accordance with the theory of cerebellar
localisations were to be expected from the method of partial and
localised extirpation of the different segments of the cerebellum.
Our studies on the cerebellum aimed specially at formulating
the general function of this organ on an experimental basis, and
Iwere confined to analysis of the components of the ataxy con-
/ sequent on more or less complete extirpation of one half, or of the
so-called vermis, or of the entire cerebellum. " From our researches
as a whole," we wrote in 1891, "it is plain that the different
segments of the cerebellum all have the same function. In fact,
the loss of the median lobe may in great measure be repaired, i.e.
organically compensated, by the lateral lobes ; and, generally
speaking, whatever the cerebellar mutilation, symmetrical or
asymmetrical, circumscribed or extensive, the defect phenomena
do not differ intrinsically, but only in intensity, extent, and
duration, and in their more or less greater incidence on one or
other side of the body. . . . We cannot, therefore, regard the
cerebellum as a collection of functionally distinct or different
centres in the sense that each of its segments is in more or less
intimate or direct relation with a special group of muscles, or is
designed for functions of different character."
Nevertheless, our investigations resulted in one definite fact
which paves the way to the theory of cerebellar localisation, viz.
that in dogs or monkeys the influence of each lateral half of the
cerebellum is mainly direct, that is, is exerted principally on the
muscles of the same side. Rolando's rudimentary experiments
established the same fact, and long before Rolando, in 1749, the
celebrated physician, Giovanni Bianchi of Rimini, had formulated
the same theory 011 a clinical observation, as we learn from
Bilaiicioni's interesting historical notice (1908).
Ferrier (1876) observed a fact which has a certain value in
relation to the theory of cerebellar localisation. He found that,
after the extirpation of the anterior portion of the vermis, monkeys
showed a tendency to fall forwards ; after extirpation of the
VIII
THE HIND-BRAIN
479
posterior part of the vermis, the tendency was to fall backwards.
Thomas (1897), on the contrary, found a special relation in dogs
between the vermis and the muscles of the anterior portion of the
.-• fv
'•--.//>
L ans
FIG. 240.— Lobular division of dog's cerebellum. (Bolk.)
trunk, and between the hemispheres of the cerebellum and the
muscles of its posterior portion.
But it was van Eynberk who first provided an experimental
basis for the theory of cerebellar
localisation, taking as his guide
Bolk's work on the comparative
anatomy of the mammalian cere-
bellum.
He attempted to test Bolk's
inductions experimentally by cir-
cumscribed extirpations of certain '*>•? *"•
lobules, and to this end performed \ ,-,,
numerous experiments in the
Physiological Institute in Rome
*/ o
(1904-8). As all his work was
carried out on the dog it is useful
in the two accompanying figures
to reproduce a diagram of the dog's
cerebellum divided into lobules
according to Bolk (Fig. 240), as
well as a sagittal section, which
allows us to compare depths of
the inteiiobar and interlobular
sulci, and the varying size of the lamellae of which the lobules are
composed (Fig. 241).
The new facts established by van Ryuberk may be grouped as
follows :—
(a) After the total or partial extirpation of the lobulus simplex
;. 241. — Sagittal section of dog's cere-
bellum to show depth of sulci. The
abbreviations on both these figures refer
to the diagram of Fig. -J3'.'.
480 PHYSIOLOGY CHAP.
the animal presents side-to-side oscillations of the head, which are
evidently due to astasia of the muscles of the neck. Both at rest
and in walking the animal exhibits rhythmical oscillations of the
head from one side to the other similar to the sign a man makes for
no. This symptom can be observed for a week, or even a month,
but owing to organic compensation it becomes less and eventually
disappears.
(b) Immediately after the more or less complete extirpation
of the crus primum a characteristic symptom makes its appear-
ance. As the animal lies quiet, or when the trunk is cautiously
raised by placing one hand below the thorax, at each mechanical
or auditory stimulus the front paw of the side oper.itrd on is
raised upward and backward to the level of the ear by flexion of
the knee. The paw remains rigid for a moment in that position,
and then falls gradually, but the same movement recurs after each
stimulus. This obviously dynamic or irritative phenomenon, which
recalls the military salute, only lasts three to seven days and
gradually disappears. When the animal subsequently begins to
walk there is seen to be considerable dysmetria in the movements
of the fore-limb, which is due to the atonia of the muscles of the
limb, and lasts a longer or shorter time according to the extent
and depth of the lesion. But these symptoms, too, disappear
owing to organic compensation.
(c) After the localised extirpation of the crus secoiidum, parti-
cularly when the genu by which this lobule is connected with the
lobulus paraniedianus is also excised, no dynamic phenomena are
ever observed, but only simple asthenia of the muscles of the hind-
limb on the same side, owing to which the limb readily Hexes
under the weight of the trunk. When the extirpation includes
the two crura of the lobus ansii'ormis, there is hen's gait, combined
with obvious asthenia and atonia of the two limbs on the side
operated on, which becomes less and disappears more slowly by
compensation.
(d) The extirpation of the lobulus paraniedianus produces
rotation on the longitudinal axis, associated with pleurothotonus to
the side operated on. According to van Eynberk these dynamic
phenomena, in which the musculature of the trunk plays a special
part, are not seen after localised extirpation of the lobus para-
niedianus. When in addition to this lobule the two crura of the
lobus ansiforniis are excised, the resulting symptoms strongly
resemble those of unilateral removal of the whole cerebellum, but
they are more perfectly compensated.
(e) After the isolated extirpation of the anterior part of the
lobulus medianus posterior, which van Eynberk termed lobule S
from its configuration, no abnormal symptoms appear. When the
crus primum is also extirpated the symptoms which this produces
are exaggerated, but eventually they are fully compensated.
vin THE HIND-BKAIN 481
These effects of the extirpation of lobules of the cerebellum
obtained by van Kynberk were continued — at least in essentials—
by the researches of Pagano (1904), Marassini (1905-6), Luna
(1907), Hulshoff Pol (1909), and Binnert (1908).
The results obtained on dogs were continued by a series of
fresh researches by van Kynberk and Vincenzoni (1908) on the
sheep's cerebellum, in which the S lobule is more developed than
in dogs. In sheep, too, excision of the paramedian lobule causes
rotation round the long axis of the animal.
Eothmann's experiments on monkeys (1910-11) harmonise well
with the localisations indicated by Bolk. He further found that
in dogs the extirpation of the lower part of the anterior lobule
disturbs phonation (barking), and also produces noticeable dis-
turbances in the movements of the tongue and jaws. These results
were not, however, confirmed by Grabower (1912).
As a whole, these experimental facts to a large extent confirm
the inductions of Bolk, and are the first positive indication of
localisation in the cerebellum. There is no experimental control
for the less accessible parts of the cerebellum ; it has been
impossible to study the effects which follow on local extirpation
of the whole anterior lobe-- which, according to Bolk, must
influence the muscles of the head — and of the formatio reticularis,
which must be in relation with the caudal and spinal muscles.
These results agree perfectly with the general theory of the
function of the cerebellum as stated above, and there is no necessity
for reviving Flourens' old hypothesis. By his morphological
studies Bolk has suggested to other investigators this new develop-
ment of cerebellar physiology, according to which the several
lobules of the cerebellum have a more intimate or direct relation
with special groups of muscles ; on the other hand the function of
reinforcement is everywhere the same in the cerebellum, and
defect of any of the lobules can be met by organic compensation
in the lobules that remain.
One of the most important results of the analysis of cerebellar
ataxy produced in dogs by the unilateral or bilateral ablation of
the cerebellum is the sharp separation of the symptoms of cere-
bellar deficiency from those vi functional compensation ; the latter
are the purposive and voluntary acts by which the animal succeeds
in obviating the effects of deficient or lost cerebellar innervation.
Directly the sigmoid gyrus of one or both cerebral hemispheres,
which contains the greater part of the voluntary motor centres, is
destroyed, the animal which has lost half or the whole of its
cerebellum loses again for a time, or permanently, the power of
maintaining the erect posture and of walking (p. 440).
In reviewing the facts which show that the compensation of
cerebellar ataxy is dependent on the motor zone of the cerebrum,
a new series of problems is at once presented to the physiologist.
VOL. Ill 2 I
482 PHYSIOLOGY CHAP.
The solution of these is important to the general physiology of
the cerebellum and the functional localisation within it, since
they not only afford new evidence for the reinforcing action of the
cerebellum upon the cerebrospinal axis, but further throw light
on the mechanism by which the motor area of the brain gradually
becomes capable of compensating the effects of cerebellar deficiency.
The most important problems raised are :—
(a) What change occurs in the normal excitability of the
cerebral motor area of dogs that have previously been deprived of
half or the whole of their cerebellum ?
(6) Is electrical stimulation of the cerebellum capable of alter-
ing the threshold value of the motor area ?
(c) Is there a definite functional relation between the cerebellar
lobules that have been electrically excited and the centres in the
central motor area, the excitability of which is affected ?
We instituted experiments directed to solving the first
question, and published the results in our Monograph (1891).
In dogs, some months after the removal of half or of the
whole cerebellum, excitability was increased in both motor
areas of the cerebral cortex, both to electrical and to mechanical
stimulation. In two dogs in which one-half of the cerebellum
had been extirpated a year previously, both sigmoid gyri containing
the motor centres for the limbs were removed. During the
operation the mechanical excitation of these centres produced
intense and general reactions in both limbs, which were equal on
the two sides. In a third dog, which had lost the median and
right lateral lobe of the cerebellum fourteen months earlier, the
same results were obtained with faradisation of the two motor
areas. Cortical excitability was increased on both sides, and we
were unable, even with weak induced currents, to provoke move-
ments limited to one limb ; they were always diffuse and involved
either the two limbs of the opposite side or all four limbs.
This increased excitability of the cerebral motor centres agrees
perfectly with our explanation of the compensation of cerebellar
deficiency, as due to an exaggerated functional activity initiated
by their greater excitability.
In 1893 Russell obtained a diminution of excitability of the
motor area of the cerebral cortex in dogs and apes some weeks
after removal of the opposite half of the cerebellum.
This result is a new argument in favour of our theory that the
cerebello-cerebral relations are principally crossed, so that the
reinforcing action which each half of the cerebellum exerts on the
cerebral motor centres mainly affects those of the opposite side.
On the other hand it can readily be understood that the ablation
of one-half of the cerebellum, by eliminating this reinforcement,
must in the early period — which may last for some weeks-
produce a diminution in the excitability of the motor centres of the
viii THE HTND-BEAIN 483
opposite, cerebral hemisphere, and it is only later, after some
months, that the exaggerated voluntary efforts, directed to the
mechanical compensation of the cerebellar deficiency, may or can
produce an increase in the excitability and functional efficiency
of the centres.
We controlled Eussell's experiments in two monkeys some
months after the extirpation of the right half of the cerebellum,
and in a dog only seventeen days after the same operation. The
excitability of the left cerebral motor area was diminished only at
certain points, while at others it appears either unaltered or
increased, in comparison with the right motor area. Not being
able at the time to give an adequate interpretation of this equivocal
result, we confined ourselves to bringing it into relation with the
fact that the anatomical and functional relations between the
cerebellum and cerebrum are mainly but not exclusively crossed.
Gilberto Eossi eventually cleared up the matter by publishing
two brief but important experimental observations in 1912, which
were obtained with all possible technical precautions.
The immediate effect of hemi-extirpatioii of the dog's cerebellum
is a diminution of excitability in the motor cortical area on the
opposite side, as compared with that on the same side as the
extirpation. This diminution can be seen during the whole of
the period in which the phenomena of deficiency persist. The
establishment of compensatory phenomena is, on the contrary,
accompanied by a definite increase of excitability in the motor
area of the opposite side, as compared with the side of the
extirpation.
These new experimental data are a direct proof of the re-
inforcing action, for the most part crossed, which the cerebellum
exercises upon the cerebrum, while they further show that voluntary
effort suffices to repair and to compensate the phenomena of
deficiency, by raising the excitability of the cerebral motor cortex.
On investigating the effect of simultaneous stimulation of the
cerebral and cerebellar cortex, Eossi found that faradic stimuli
applied to the cortex of one lateral half of the cerebellum in
all the lobes explored — crus primum, crus secundum, lobulus
paramedianus — raised the excitability of the cerebral cortex on
the opposite side. That is, no motor reaction was induced, but
the threshold of excitation of the central motor area of the
opposite side was lowered, which, by facilitating the motor effects,
made previously inefficacious currents effective. On the other
hand, faradisation of the same parts of the cerebellum on one side
caused no appreciable modification in the excitability of the
cerebral cortex on the same side. Very weak faradic currents
produce these effects, during slight narcosis of the animal. In
profound narcosis the stimulation of the cerebellum is ineffective.
These new experimental observations published by Eossi
2 I 1
484 PHYSIOLOGY CHAP.
confirm the relative inexcitability of the cerebellar cortex already
demonstrated by Horsley and Clarke, but at the same time they
partially elucidate the mechanism of the reinforcing action of
the cerebellum on the cerebrum. On the other hand they
contribute nothing to the theory of cerebellar localisation, which
rests upon a totally different order of facts. To settle the question
of functional localisation in the cerebellum by the method of
simultaneous stimulation of the cerebellum and cerebrum would
require a long series of delicate experiments (on which Eossi is at
present engaged) on the effect upon the excitability of the
corresponding motor centres of the cerebral cortex, of stimulating
the separate cerebellar lobes.
BIBLIOGRAPHY
The most important publications on the Cerebellum are : —
ROLANDO. Saggio sopra la vera struttura del cervello. Sassari, 1809 ; Turin, 1823.
MAGENDIE. Precis elemeutaire de physiologic. Paris, 1825.
BOUILLAUD. Arch. gen. de med. xv. Paris, 1827.
ANDRAL. Clinique med. v. Paris, 1833.
FLOURENS. Recherches experimentales sur les proprietes et les fonctions du
systeme nerveux dans les animaux vertebres. Paris, 1842.
DALTON. Amer. Journ. of Med. Sciences. 1861.
WAGNER. Journ. de physiol. de Brown-Sequard, iv., 1861.
LUSSANA. Ibidem, v., 1862. Fisiologia e patologia del cervelletto. Padua, 1897.
LEVEN and OLIVIER. Arch. gen. de med., 1862-63.
LUYS. Arch. gen. de med., 1864.
WEIR-MITCHELL. Amer. Journ. of Med. Sciences, 1869.
LONGET. Traite de physiologic. Paris, 1873.
HITZIG. Untersuchungen liber das Gehirn. Berlin, 1874.
FERRIER. Functions of the Brain, 1876.
NOTHNAGEL. Centralbl. f. med. Wiss., 1876. Virchow's Arch. Ixiii., 1877.
Topische Diagnostik der Gehirnkrankheiten. Berlin, 1879.
LUCIANI. II Cervelletto. Florence, 1891. Rivista sp. di freniatria, xviii., 1892 ;
xxi., 1895. Archives italiennes de phys. xxi., 1894.
MARCHI. Sull' origine e decorso dei pednncoli cerebellari. Florence, 1891.
LANGE. Pfliiger's Archiv, 1., 1891.
EWALD. Untersuchungen iiber das Endorgan d. N. octavus. Wiesbaden, 1892.
RUSSELL RISIEN. Phil. Trans. Roy. Society of London, v. 185, 1894. British
Med. Journal, 1894.
FERRIER and TURNER. Phil. Trans, v. 185, 1894.
SCHIFF. Recueil des niemoires physiologiques, vol. iii., 1896.
BECHTEREW. Arch. f. Anat. u. Physiol., 1896.
THOMAS. Le Cervelet. Paris, 1897.
MONAKOW. Nothnagel's Spez. Pathologic, ix., 1897.
ABLER. Die Symptomatologie der Kleinhirnerkrankungen. Wiesbaden, 1899.
DEGANELLO. Arch, delle scienze med. xxiv. , 1900.
DREIFUSS. Pfliiger's Archiv, Ixxxi., 1900.
PROBST. Arch. f. Psych, u. Nervenkrankh. xxxv., 1902.
LEWANDOWSKY. Arch. f. Anat. u. Physiol., 1903. Das Kleinhirn. Jena, 1907.
GAGLIO. Arch, per le scienze med. xxiii., 1899. Arch. ital. de biol. xxxviii.
1903.
STEFANI. Atti del R. 1st. veneto, Ixii., 1903.
DUCCESCHI and SERGI. Arch, di fisiol. del Fano, i., 1904.
PATRIZI. Memorie della R. Ace. di scienze, lettere, ed arti in Modena, 1905.
H. MUNK. Sitzungsber. d. k. preussischen Akad. d. Wissensch., 1906-7.
LANGELAAN. Verh. d. k. Akad. van Wetensch. te Amsterdam, 1907.
vni THE HIND-BKAIN 485
A. MUURI. Lczioni di clinica medica. Milan, 1908.
G. MlNGAZZlNl. Lezioni di anatomia clinica dei centri nervosi. Milan, 1908.
Theory of Functional Localisation of Cerebellum :—
PRUS. Arch, polonaises des sciences biol. et med. i., 1901.
BULK. Morpliol. Jahrbuch, xxxi., 1902. Psychiatrische en neurol. Bladen, 1902.
Monatsschr. f. Psychiatric und Neurologic, xii. Verh. d. k. Akad. van
"Wetensch. te Amsterdam, i., 1905 ; ii., 1905. Das Zerebellum der Saugetiere.
Jena, 1906.
VAN RYNBERK. Archivio di fisiologia di Fano, i., 1904 ; ii., 1904. Archives
intern, de physiologic, v., 1907. Folia neuro-biologica, i., 1908. Ergebnisse
der Physiologic, VII. Jahrgang, 1908 ; VIII. Jahrgang, 1912.
PAGANO. Rivista di pat. nervosa e mentale, vii., 1902 ; ix. 1904. Archives
intern, de physiologic, ii., 1904. Archives italiennes de biologie, xliii., 1905.
MARASSINI. Archivio di fisiologia di Fano, ii., 1905. Archives italiennes de
biologie, xlvii., 1907.
LUNA. Ricerche fatte nel laboratorio di anat. normale di Roma e in altri
laboratori biologici, xii., 1906.
HORSLEY and CLARKE. British Med. Journ., 1906.
HORSLEY and BOUCHE. Ibidem, 1907.
NEGRO and ROSAENDA. Giornale della R. Ace. di Med. di Torino, xiii., 1907.
Archivio di psichiatria, med. legale e antr. criminale, xxviii., 1907.
VINCENZONI. Archivio di farmacologia sperimentale e scienze affini, vii. 1908.
BINNERTS. Academisch proefschrift. Amsterdam, 1908.
LOURIE. Neurologisches Zentralblatt, Leipzig, 1908. Pfliigers Archiv. Bonn,
1910.
HORSLEY and CLARKE. Brain. London, 1908.
HULSHOFF POL. Psych, en neurologische Bladen. Amsterdam, 1909.
MAGNINI. Arch, di fisiologia del Fano, vii., 1910. .
ROTHMANN. Neurol. Zentralblatt. Leipzig, 1910-11.
ROTHMANN und KATZENSTEIX. Ibidem, 1911.
BAUER and LIEDLER. Arbeiten aus dem neurol. Institute aus der Wiener
Universitat, 1911.
BECK and BIKELES. Pfliigers Archiv, 1911. Zentralblatt f. Physiol., 1912.
GRABOWER. Arch. f. Laring. und Rhinologie, xxvi., 1912.
G. Rossi. Archivio di fisiologia, x. p. 251, 1912. Ibidem, x. p. 389, 1912.
Recent English Literature :—
HORSLEY and CLARKE. On the Intrinsic Fibres of the Cerebellum, its Nuclei
and its Efferent Tracts. Brain, 1905, xxviii., 13.
HORSLEY and CLARKE. The Structure and Function of the Cerebellum examined
by a new Method. Brain, 1908, xxxi. 138.
SHERRINGTON. The Integrative Action of the Nervous System. London, 1906.
HORSLEY and MAC-NALTY. On the Cervical Spino-bulbar and Spino-cerebellar
Tracts, and on the Question of Topographical Representation in the Cerebellum.
Brain, 1909, xxxii. 237.
CHAPTER IX
MID-BRAIN AND THALAMENCEPHALON
CONTENTS. — 1. General structure of the mesencephalon. 2. The thalamen-
cephalon. 3. Effects of total extirpation of fore-, inter-, and mid-brain in fishes ;
4. In amphibia ; 5. In birds ; 6. In mammals. 7. Effects of stimulating the
mesencephalon. 8. Effects of extirpating the corpora quadrigemina alone.
9. Effects of dividing the whole or half the brain-stem at level of the mid-brain.
10. Effects of incomplete or total removal of optic thalami. Bibliography.
I. THE Mid-brain (mesencephalon) arises from the median primary
vesicle of the embryonic brain, which is interposed between the
hind -brain (pons and cerebellum) and the inter -brain (optic
thalamus). Of the cerebral vesicles this is the one that under-
goes least alteration during development. The changes consist
principally in a simple thickening of its walls and subsequent
restriction of the cavity, which is transformed into the aqueduct
of Sylvius. In the lower vertebrates it attains a more or less con-
spicuous development ; but in mammals its comparatively pre-
cocious development is arrested very early, and in man it develops
least of the five original parts of the brain.
The mid-brain is usually divided into two parts : one ventral—
the cerebral peduncles ; the other dorsal — comprising the corpora
quadrigemina which in lower vertebrates are also known as the
optic lobes.
The ventral portion of the mid-brain is divided into two parts
by the substantia nigra of Sommerung, the ventral of which is
termed the pes or crusta of the peduncle, the dorsal the tegmentum
(Figs. 242, 243).
The first is the continuation of the pyramidal fibres of the pons
and bulb, with the addition of other longitudinal fibres which
corne from the fore-brain ; the second is the continuation of the
formatio reticularis, with the addition of much grey matter and of
white fibres, some of which represent the continuation of the
superior cerebellar peduncles. The crura of the peduncles are
separated from one another ; the two tegmerita, on the contrary,
are united in the median plane along the raphe, and extend
dorsally on the side of the aqueduct into the corpora quadrigemina.
486
CHAP, ix MID- AND INTEE-BEAIN 487
Viewed in section the base of the peduncles is'crescentic in form ;
the bundles of which it is composed are separated by prolonga-
tions of the pia mater. The pyramidal bundles of the cord, medulla,
and pons, are the largest element, and occupy the median part, of
the cms of the peduncles. They arise from the Eolandic or central
region of the cerebral cortex, pass through the internal capsule,
and run to the nuclei of origin of the motor nerves in the pons,
bulb, and cord. The external or lateral segment of the pes is
formed of bundles which are the prolongation of the lateral
bundles of the poiis ; these take origin in the occipito-temporal
regions of the cerebral cortex, and terminate in the cells of the
nuclei of the pons which give rise to the fibres that form the
ponto-cerebellar path. The internal median segment of the pes
is composed of fibres which develop late as compared with those of
the pyramidal bundle ; they pass through the anterior portion of
FIG. 242.— Outline of two sections across the mesencephalon. Natural size. (Schafer.) A, through
inferior pair of corpora quadrigemina ; B, through superior pair, cr, crusta ; s.n., substantia
nigra ; t, tegmentum ; s, Sylvian aqueduct with central grey matter ; c.q.. grey matter of
quadrigeminal bodies ; l.g,, lateral groove ; p.L, posterior longitudinal bundle ; il.V, descending
root of 5th nerve; s.c.p., superior cerebellar peduncle; /, fillet. The dotted circle in B
indicates the tegmental nucleus.
the internal capsule, and come from ^he prefrontal region of the
hemisphere.
The substantia nigra consists of pigmented cells and nerve-
fibres of which the destination is unknown. They form the
ventral stratum of the tegmentum, which contains much grey
matter, consisting of scattered nerve-cells intersected by longi-
tudinal, transverse, oblique and arcuate fibres, which give the
same appearance to the lower part of the mesencephalon as the
formatio reticularis of the bulb or pons (Fig. 228). Besides the
scattered bundles of longitudinal fibres, we have to consider
the dorsal longitudinal bundle, the superior cerebellar peduncles,
and the fillet of Eeil (Fig. 244;. The first arises from the nuclei
of the motor cerebral nerves, and especially from the 3rd, 4th, and
6th pairs ; the second, as we have seen, decussate near the red
nucleus of Stilling, and pass to the ventral portion of the optic
thalamus ; the fillet originates principally in the nuclei of the
dorsal columns of the opposite side, and comes into relation with
the corpora quadrigemina and optic thalamus.
The aqueduct is surrounded by a layer of grey matter, which
2 I 2
488
PHYSIOLOGY
CHAP.
is the prolongation of that which lines the floor of the fourth
ventricle. In addition to many scattered cells, the grey matter of
the aqueduct contains the cell columns which give origin to the
roots of the 3rd, 4th, and the descending root of the 5th nerve
(Fig. 208).
The posterior corpora quadrigemina consist almost entirely of
'
FIG. 243. — Transverse section across mid-brain, through inferior corpora quadrigemina. Magnified
about 3 J diameters. From a photograph. (Schafer.) ST., dorsal quadrigeminal groove (sulcus
longitudinalis) ; c.i/.p., corpus quadrigeminum posterius ; str.l., stratum lemnisci ; c.yr., central
grey matter ; n.lll, IV, oculo-motor nucleus ; d.V., descending root of 6th nerve ; p.l.b., posterior
longitudinal bundle; f.r.t., formatio reticularis tegmenti ; d, tl', decussating fibres of tegmentum;
s.c.j)., decussating fibres of superior cerebellar peduncles; /, upper fillet;/', lower or lateral
fillet; p.p., pes pedunculi ; s.??., substantia nigra ; g.i.p,, interpeduncular grey matter; Sy,
Sylvian aqueduct.
grey matter (Fig. 243). The cells which they contain are in
connection with the endings of the fibres of the lateral fillet,
which arise from the nucleus cochlearis of the auditory nerve
on the opposite side. In correspondence with this intimate
relation of the posterior corpora quadrigemina with the nucleus
of I the cochlear nerve, it is in mammals only --which have a
well -developed auditory apparatus — that the posterior corpora
quadrigemina appear as distinct prominences. Other vertebrates,
IX
MID- AND INTER-BKAIN
489
including birds, bare only corpora bigeinina (optic lobes), wbicb
probably represent tbe anterior pair.
The anterior quadrigeminal bodies are less prominent, but
longer and darker, than the posterior (Fig. 229). A small bundle
of white fibres, which emerges from the lateral edge of the nucleus
and runs towards the corpus geiiiculatum externum, is a part of the
optic nerve. Fibres also spring from the cells of the grey matter
' •
-t
^Ki/'^M
!:lll&^il£
FIG. 244. — Section across miil-bi-ain, through superior corpora quadrigeinina. Magnified about 3J
diameters. From a photograph. (Schafer.) Sy, Sylvian aqueduct ; r.p., posterior com-
missnre; fil.pi., glandula pincalis ; c.q.a., grey matter of one of superior corpora quadrigemina
i'. 1,1. in., corpus geniculatum mesiale ; e.g.!., corpus geniculatum laterale ; tr.ojit., optic tract
p.p., pes pedunculi ; p.I.b., posterior longitudinal bundle; /., upper fillet; r.n., red nucleus
H.III, nucleus of 3rd nerve ; III, issuing fibres of 3rd nerve ; l.p.p., locus perforatus posticus.
of these eminences, and terminate in the nuclei of the 3rd and 4th
pair, where the fibres of the posterior longitudinal bundle also end.
Impulses from the optic nerve can thus readily be reflected to the
nuclei of the nerves that innervate the muscles of the eye.
II. The Inter - brain (thalamencephalon) originates, as we
have seen, in the 2nd secondary vesicle of the embryonic brain.
The optic thalami are the thickening of the walls of this vesicle,
the cavity of which shrinks in the adult to the third ventricle.
490
PHYSIOLOGY
CHAP.
Viewed from above the optic thalami are two large oval masses
of grey matter, which are covered by a thin sheet of white fibres.
At the anterior end a mass known as the tuberculum anterius
projects into the lateral ventricle, and is covered with the
FIG. 245. — View from above of third ventricle and part of the lateral ventricles. (Henle.) The
lirain has been sliced horizontally immediately below the corpus callosum, and the fornix and
velum interposition have been removed. Tho, thalamus opticus ; 7's, its anterior tubercle;
Pr, pulvinar ; Com, middle commissure stretching between the two optic thalami across middle
of third ventricle ; Cf, columns of fornix ; On, pineal gland projecting downwards and
backwards between superior corpora quadrigemina ; St, stria terminals ; Cs, nucleus caudatus
of corpus striatum ; Vsl, ventricle of septum lucidum ; CcW, section of genu of corpus callosum ;
Pen, pineal peduncle ; Tfo, pineal stria; Cop, posterior commissure.
epithelium that lines this cavity. At the posterior and mesial
end a still more conspicuous prominence, known as the pulvinar,
extends over the quadrigemiual bodies and partially covers them
(Fig. 245).
IX
MID- AND INTER-BEATN
491
At the ventral part of the posterior end of the optic thalamus
are two oval prominences, the corpora geniculata. The corpus
geiiiculatuin internum is the smaller ; it is connected with the
posterior quadrigeminal body hy a bundle of medullated fibres
known as the • brachium posticum. The corpus geuiculatum
externum or laterale lies directly below the pulvinar, and is con-
siderably larger; it receives the external root of the optic tract,
and is united to the anterior quadrigeminal body by a bundle of
medullated fibres known as
the brachium antieum.
A frontal section of
the optic thalamus shows
that the grey mass of
which it is composed is
divided into three distinct
nuclei by a medullary
layer : an internal nucleus,
lying between this layer
and the third ventricle ; an
external nucleus between
the internal nucleus and
the so-called internal cap-
sule ; and an anterior or
superior nucleus which
corresponds to the anterior
tubercle of the thalamus
(Fig. 247).
A horizontal section
through the thalamus
shows the same three
nuclei (internal, external,
anterior) under another
aspect (Fig. 247).
The optic thalamus at
its lower and external surface is in direct relation with the
bundles of fibres coming from the upper end of the peduncle.
These are the fibres of the superior cerebellar peduncle; fibres
which arise from the cells of the red nucleus ; the fibres of the
dorsal longitudinal bundles ; and part of the fibres of the median
lemniscus or fillet of Reil.
Other fibres connect the optic thalamus with the nuclei of the
corpus striatum. These take origin partly in the caudate nucleus,
partly in the lenticular nucleus. They cross the genu and posterior
segment of the interior capsule, and penetrate the lateral border of
the thalamus. Larger bundles issue from the ventral surface of
the lenticular nucleus, and enter the ventral surface of the thalamus.
The fibres that unite the thalamus to the cerebral cortex spring
FIG. 246.— Mesencephalon and its relations. (Testut.)
1, third ventricle ; 2, epiphysis or pini'al gland ; 3,
trigonum habenulae ; 4, posterior end of optic thalamus ;
5, external ; 6, internal geniculate bodies ; 7, optic
tract with its two roots ; 8, anterior ; 9, posterior
corpora quadrigemina ; 10, anterior ; 11, posterior
brachium of corpora quadrigemina ; 12, pons ; 13,
valve of Vieussens ; 14, superior cerebellar peduncles ;
15, trochlear nerve ; 16, lateral bundle of isthmus
cerebri ; 17, fourth ventricle ; 18, middle cerebellar
peduncles ; 19, inferior cerebellar peduncles.
492
PHYSIOLOGY
CHAP.
from its different portions, and spread like a fan into the centrum
ovale. They are grouped into three principal 1 amdles. The anterior
bundle emerges at the frontal end of the thalamus, runs through
the anterior segment of the internal capsule, and spreads to the
cortex of the frontal lobe. The posterior bundle arises in the
pulvinar and corpus geniculatum exteruuni, follows an antero-
posterior course, crosses the
hindmost segment of the
external capsule, and spreads
out to the cortex of the
occipital lobe (optic radia-
tion of Gratiolet). The in-
ferior bundle starts from the
mesial and ventral parts of
the thalamus, runs obliquely
lateralwards, passes along
the ventral surface of the
lenticular nucleus, and
finally ends in the cortex
of the temporal lobe and
insula (ansa peduncularis of
Gratiolet).
It is important to deter-
mine the origin, course, and
termination of the optic
nerves, and their connection
with the mid -brain, thala-
•mus, and cerebrum. The
fibres that make up each
optic nerve arise from the
ganglion cells of the retina.
They emerge from the eye-
ball a little mesial to the
posterior pole, and enter the
Fio. 24
Thalamencephalon and its relations. Frontal
section through grey commissure. (Testut.) a,
frontal portion of lateral ventricle ; h, its inferior
horn ; c, third ventricle ; d, Sylvian fissure ; e,
optic tract ; /, gyrus hippocampi. 1, lamina
incdullaris interna of optic thalamus ; 2, lamina
medullaris externa ; 3, internal ; 4, external ; 5,
superior nucleus of optic thalamus ; 6, caudate
nucleus ; 6', its lower end ; 7, 7', lenticular nucleus ;
8, claustrum ; 9, external capsule ; 10, internal
capsule ; 11, pes pedunculi ; 12, substantia nigra ;
13, stratum dorsale of regio subthalamica ; 14, zona
incerta ; 15, nucleus' of Luys ; 16, anterior end of
red nucleus ; 17, great commissure.
cranium through the optic
foramen. Directly after
entering the skull both optic
nerves unite in the chiasma, in which more than half the fibres
decussate, and thence pass to the posterior part of the optic
thalamus or pulvinar under the name of the optic tract.
Experimental physiology and pathological anatomy show
clearly that each optic nerve contains two distinct bundles of
fibres : one direct, which remains on the side in which it takes
origin, and a crossed bundle, which decussates in the chiasma to
pass to the other side. The fibres of the direct bundle come from
the external or temporal third of the retina ; those of the crossed
bundle from the two inner or nasal thirds. The dividing line
IX
MID- AND INTEE-BEAIN
493
9
between these two retinal zones corresponds to a vertical plane
through the t'ovea eentralis or yellow spot of the retina (Fig. 249).
Besides these two handles Samelsohn (1882) distinguishes a third
-macular — bundle that includes the tibres from the macula lutea,
the seat of central or direct vision.
The macular bundle again divides
into two groups of tibres : one
direct, which remains on the same
side ; one crossed, which decussates
in the chiasma and passes to the
other side. Fig. 250 shows the
position and direction of the three
bundles which make up the optic
nerve.
Partial decussation of the fibres
of the optic nerves is constant in
man and in the ape, but it is not
general in the vertebrate series.
The existence of the direct bundle
seems to be associated with binocu-
lar vision, since in animals whose
eyes are directed sideways, so that
binocular vision is impossible, e.g.
in birds and fishes, there is total
decussation of the optic fibres.
This rule, however, has certain ex-
ceptions : in the rabbit, dog, and
cat there is a partial crossing,
though less than in monkeys and
man, but in the mouse and guinea-
pig, according to Singer and
Miinzer, decussation is complete.
And in some birds, e.g. the owl, in
which vision is binocular owing
to the position of the eyes, de-
cussation is still complete.
As shown in Fig. 250, the
chiasma also contains in its pos-
terior parts commissural fibres,
which are not connected with the
optic nerves and eyes, but pass from the internal geniculate body
of one side to that opposite ; these constitute Gudden's commissure,
the function of which is quite unknown.
The optic tract runs obliquely backwards, and after passing
around the cerebral peduncle divides into two branches of unequal
size (Figs. 189, 190, pp. 327, 328). The lateral branch contains all
the optic fibres of the direct, crossed, and macular bundles ; a large
FIG. 248.— Horizontal section of left hemi-
sphere. (Flechsig.) 1, anterior; 2, pos-
terior limb ; 3, genu of internal capsule ;
4, nucleus lenticularis ; 5, nucleus cauda-
tus ; 6, optic thalamus ; 7, anterior horn
of lateral ventricle; 8, its posterior or
occipital horn ; 9, septum lucidum and its
central cavity ; 10, 11, fornix ; 10', corpus
callosum ; 12, claustrum ; 13, external
capsule; 14, insula ; 15, Sylviuu tissuif.
494
PHYSIOLOGY
CHAP.
part of these fibres terminate in the external geniculate body ;
others which pass ventrally and laterally to the geniculate body
enter the pulvinar ; other less numerous fibres take a more
medial direction and reach the anterior corpus quadrigendnum.
The finer internal branch of the optic tract is the continuation
of Gudden's commissure, and therefore contains no optic fibres
properly so-called. It enters the internal geniculate body, and
through it reaches the posterior quadrigeminal body.
III. The mid - brain and inter - brain are the parts of the
central nervous system which from their situation in the higher
animals have been least satisfactorily studied by ordinary physio-
logical methods. The results of researches on the lower animals,
in which the methods of ablation
succeed fairly easily, are not
directly applicable to mammals
and man, in which these segments
of the brain probably have a less
important or different physio-
logical value, owing to the pre-
ponderating importance and
influence of the other centres,
especially the cerebrum and the
cerebellum.
Owing to the incomplete and
not infrequently incoherent and
contradictory results of experi-
ment, we must, therefore, confine
ourselves to a critical discussion
of the most definite fundamental
facts.
The observations on the effects
of total extirpation, either of the
fore -brain alone, or of the inter- and hind -brain in different
classes of vertebrates, are most important to the physiology of
these three parts of the brain. Certainly they do not exactly
define the functions of the individual centres contained in the
parts that are destroyed or preserved; but they undoubtedly
place us in a position to form a general conception of their physio-
logical significance. The functions lost depend on the segments
destroyed ; the functions that remain, on the surviving segments.
Arnpliioxus, the lowest type of vertebrate, has no true brain,
but the anterior end of the cord is slightly enlarged owing to the
presence of a sinus ovalis which is continued into the vertebral
canal. This represents a rudimentary brain, which does not
differ essentially in structure from the rest of the cord, since it
consists of internal white matter and an outer layer of nerve-
fibres that run longitudinally.
FIG. 249. — Comparative extent of the retinal
areas connected with the direct and crossed
bundles of the optic nerve, in fundus of
left eye. (Testut.) n, nasal portion
connected with the crossed ; t, temporal,
with the direct bundle ; re, x, separating
line between the two portions. 1, sclerotic ;
2, choroid ; 3, retina ; 4, pupil ; 5, fovea
centralis and yellow spot.
IX
MID- AND INTER-BE AIN
495
Steiner (1885) divided Amphioxus into two transverse halves,
cephalic and caudal ; both parts fall immediately to the bottom
of the vessel, and lie motionless, but if after a few minutes the
two parts are stimulated mechanically, each begins to move with
perfect regularity, maintaining its equilibrium and always
advancing head -end forward. If the animal is divided into
three or four segments, each of these, after a suitable interval,
responds by locomotor movements to external stimuli. Steiner
concluded from these observations that Amphioxus consists of a
number of metameres which in no way differ physiologically,
and that it has no true brain or controlling centre for general
movements.
Danilewsky obtained somewhat different results from his later
FIQ. 250. — Diagram of decussation of optic nerve-fibres in chiasma. (Vialet.) 1, optic nerve on
left ; 1', on right side ; 2, 1', optic tract on left and right side ; a, direct ; 6, crossed bundle ;
e, macnlar bundle, partly crossed, partly direct ; d, Gudden's commissure.
experiments. After bisecting the animal, he saw that the anterior
half was capable of executing spontaneous rhythmical extension
and flexion movements, but not true, locomotion ; the posterior
half, on the contrary, remained motionless for a long time. Arti-
ficial stimulation elicited motor reactions more readily from the
head than from the tail end.
When the head is cut off, spontaneous movements cease ; the
animal remains one to two days motionless unless artificially
stimulated. The reflex movements are normal but weak, and
excitability seems more depressed than in the anterior part of the
divided animal.
From these and similar observations, Danilewsky concluded
that the so-called " brain " of Amphioxus contains the centres
for voluntary movement, that is, controlling centres for all the
other segments of the neuraxon.
In fishes in general the brain is but little developed. In
496
PHYSIOLOGY
CHAP.
Cyclostomes and Teleosteans the cerebral mantle consists of a single-
layer of ectodermal cells.
According to Steiner no disturbances in
the movements are seen after excising the
fore-brain of Squalius cephalus, a teleostean
(Fig. 251); the animal moves as though it
were intact. If offered a living worm it
chases, catches, and swallows it. If a bit
of string of much the same size is thrown
into the water, the animal comes up in the
same way, but turns off lief ore catching it,
or rejects it from its mouth. It is able to
select its food, and recognises its companions
that have not been operated on. Steiner's
experiments show that ablation of the fore-
^ner^SSSn: brain iii this class of fish produces no
2)
FIG. 251. — Brain of Sqtudius
noticeable disturbance ; we may, therefore,
brain ; D, myelencephalon conclude that the parts of the liei'VOUS
system remaining intact suffice for the com-
plete execution of all the higher nervous functions.
These are certainly represented in the mid- and 'tweeii-brain.
When the optic lobes are excised, according to Steiner, the animal
loses its power of maintaining equilibrium, and lies on its side, or
back, motionless, with relaxed fins.
But the return of spontaneous move-
ment, some time after the operation, is
not excluded : Steiner did not continue
his observations long enough.
According to Sterner, removal of
the anterior brain in Selachians, as
in the dog-fish (Scyllium canicula,
Fig. 252), causes immobility for many
hours and even days, unless the animal
is artificially stimulated. Bethe was
unable to confirm this observation,
as he found that removal of the fore-
brain did not abolish spontaneous
movements. The animals certainly
no longer feed spontaneously, but FlG. 252.-Bram ot
this is due not to ablation of the
fore-brain, but to destruction of the
olfactory lobes, as is proved by the
fact that excision of the latter alone
produces the same effect. On the
other hand, attentive observation of the normal dog-fish shows
that it is largely guided by the sense of smell in seeking its food ;
the Squalius, on the contrary, by the visual sense.
(Steiner.) en, nasal capsule; bo,
olfactory bulb: A, prosencephalon;
A', optic thalami or 'tween-brain ; P>,
optic lobes or mid-brain ; C, meten-
cephalon or hind-brain ; D, myelen-
cephalon or bulb, from which the
vagus nerve emerges.
ix MID- AND INTEK-BKATN 497
Even when the mid -brain as well as the 'tween -hrain is
destroyed, there is, according to Bethe, no disturbance of the
spontaneous movements ; the dog-fish is still capable of perfectly
equilibrated movements, which differ in no way from those of the
normal animal.
Marked disorders of movements only appear after removal of
the mid- and hind-brain; the results of Steiuer, Loeb, and Bethe
all agree on this point. The roof of the mid-brain is not
concerned in the movements, and it can be extirpated on one or
both sides without producing any motor disturbance, but accord-
ing to Steiuer the animal no longer reacts to light stimuli.
O • i »
Removal of the ventral part of the mid-brain, on the contrary,
produces constant motor disturbances, which are specially marked
after unilateral section.
If the whole of the right side is divided at the posterior edge of
the mid-brain, the animal swims directly after the operation in
circular progression to the left. Sometimes these circus move-
ments are associated with rotation round the long axis.
After total separation of the mid- and hind-brain, the animal
usually exhibits circus movements to either side, but if the lesion
is quite symmetrical, it advances in a straight line, and turns and
changes its direction only on coming in contact with the vessel
walls. Moreover, it changes from the horizontal plane into an
oblique or vertical direction only under external stimulation, and
during such change it may for a time take up the abnormal
position with its back downwards, though finally it turns over
briskly to assume the abdominal position. To conclude, the dog-
fish without its mesencephalon executes perfectly normal swimming
movements, but has difficulty in altering the direction of its
movements, while orientation in space is affected but not lost.
According to Bethe, Steiner is mistaken in stating that the animal
O "
is incapable of spontaneous movements under these conditions, and
that artificial stimuli are necessary to rouse it to locomotion.
IV. We must next consider the effects of destroying the brain
in Ampliilia, and, first of all, in the frog (Fig. 25.':!).
Goltz1 assumed (1869) that absence of voluntary locomotor
movements was the most important point in which the animal
that had lost its fore -brain differed from the intact animal.
Obviously, however, he excised the optic thalanius or mid-brain
together with the fore-brain. When the functions of these two
separate parts of the brain are distinguished, as was achieved by
Goltz' pupil M. Schrader (1887), the results are very different, for
if the optic thalami are interfered with as little as possible the
animal differs in no respect from the intact animal. The frog
moves spontaneously, even when placed in an unnatural position ;
1 In his monograph, " JBeitrage zur Lehre von den Funktionen dcr Nervenzentrcn
des Frosches."
VOL. Ill 2 K
498
PHYSIOLOGY
CHAP.
swims normally ; buries itself at the beginning of winter; if slowly
lowered by a screw adjustment into water begins to swim at once
like an intact frog ; and is capable when the hibernating season is
over of feeding itself like a normal frog, by catching the flies that
come into its vessel.
That the senses, particularly vision, remain intact in the frog
after removal of the fore-brain had already been demonstrated by
Desmoulins, Magendie, Longet, and others, though Flourens stated
the contrary. When stimulated to move, these animals are
capable of avoiding the obstacles they meet. Blanschko repeated
these researches under H. Munk
(1880), and found that the frog
deprived of its hemispheres is
capable of adapting its move-
ments to different positions,
and to the size and nature of
obstacles, and to vary them
suitably when the power of
moving is interfered with, or
the position of the obstacles
changed. Such frogs are not
merely not blind in any ab-
solute sense, but they are not
even "psychically blind"; they
retain not only sensations but
also perceptions and visual
images like the intact frog.
The other senses are also un-
affected, with the exception, of
course, of the sense of smell,
Fit-. 253. -Frog's brain — enlarged four times. sillCe this depends Oil the
(Loeb.) G.C., prosencephalon ; Th.O., optic f.lfflp^-m,v Vmlllcl whinli nvp PY
thalanms: Lnb. opt., optic lobes; P. C., cere- uiaGtOiy IDS, WHICH aiC 6X-
beiium, showing medniia obiongata below, tirpated with the fore-brain.
whence issue the cranial nerves. TTT-I
When the optic tlialaim are
totally destroyed as well as the hemispheres, the animal, according
to Schrader, remains motionless, but this state of depression
partially wears off. If the animal is examined some months
after the operation, at the close of the winter sleep, when the
lesion is perfectly healed, it is seen that on gradually lowering it
by means of the screw into water it does not swim as when the
hemispheres alone are removed, but floats motionless on the
surface. On repeating Goltz' experiment, in which the animal is
made to walk up and down an inclined plane (Fig. 254), the
frog without a mid-brain moves its head only, and makes no
attempt to climb up ; if the plane is too much sloped the creature
crawls down instead of up, viz. behaves in a manner exactly
opposite to that of the frog that has lost its hemispheres only.
IX
MID- AND INTER-BRAIN
499
The effects of excising the whole of the mid-braiu again differ
slightly, according to Schrader, from the results obtained by Goltz
and Steiner. When the medulla oblongata is uninjured by this
operation, the mutilated frog preserves its quack -reflex, and the
characteristic swim-reflexes, the centre for which lies not in the
optic lobes (Goltz and Steiner), but in the bulb. But if the
animal is left undisturbed without external stimulation, the sup-
pression of the spontaneous movements, according to Schrader,
is even more definite and complete than when only the fore- and
mid-brain are removed. Evidently this depends not on the
removal of the mid-brain as held by Goltz and Steiner, but on the
functional depression of the locomotor centre in the bulb, due to
FII;. 254. — Goltz' experiment on frog deprived of its cerebral hemispheres, and made to climb up
and down an inclined plane. On the left the frog is seen ascending an inclined board ; in the
(.entre it has climbed to the top of the upright board; on the right it is coming down the
opposite slope.
operative traumatism. As early as 1883 Fano demonstrated that if
the experiment were repeated on the toad (Bufo viridis), which is
very near the frog in the zoological scale, but is far more resistent
and less excitable, a similar result is obtained as with the marsh
tortoise (see p. 413). After destroying the whole mid -brain
(including of course the 'tween- and fore-brain), automatic loco-
motion can be seen in this animal as readily as in the tortoise.
But while in the latter the locomotor movements may be con-
tinuous, in the toad they are nearly always periodic, viz. in the
form of groups of locomotor movements separated by pauses.
Toads, like tortoises, when deprived of the mid-brain, recover their
normal position by appropriate movements if turned over on
the back.
Fano's studies on the marsh tortoise are of great importance,
as regards the results of removing the fore- and mid-brain. They
may be summarised as follows : Removal of the cerebral hemi-
spheres (Fig. 255) does not apparently deprive the animal of
any of the faculties attributed to the fore - brain. It moves
500
PHYSIOLOGY
CHAP.
spontaneously, sees quite well, avoids obstacles, responds ade-
quately to the impressions it receives, and behaves in all respects
like the normal tortoise. The only difference is that it moves
slower, is less lively, and shows less initiative. Still its actions
are certainly not merely reflex, and probably arise in the optic
thalami. Fano, in fact, demonstrated not only by removal of
the hemispheres, but also by stimulation of the thalami, that
the latter play a considerable part in the evolution of the
voluntary acts. The optic thalami, like the cerebral hemispheres,
react to electrical stimulation by groups of locomotor movements
which have all the character of voluntary movements, which
is not the case on electrical stimulation of other parts of the
nervous system.
When the optic thalami as well as the hemispheres are excised
in a tortoise,- the constant result is that spontaneous activity
ceases, and the animal becomes absolutely
motionless. It remains for days in the
position in which it is placed without
manifesting any reaction. Its spon-
taneous activity is not abolished, but
merely inhibited, by the mid-brain, for
we have seen that on removing the latter
automatic locomotion reappears.
On the strength of these results,
which were confirmed by Bickel, Fano
credited the mid-brain with a continuous
inhibitory action upon the automatic
the medulla. According to
central mechanism of the
movements of the tortoise
the
.A
Fin. '25'>. — Brain of Kmys
seen in situ, after removing the
top of the skull. (Fano.) A,
prosencephalon ; B, inescnceplia-
lon ; (.', metencephalon ; D, my-
elencephalon.
centres of
Fano, the
voluntary
consists in inhibition by the fore- and 'tween -brain of
constant tonic inhibition exerted by the mid-brain. So soon as
the fore-brain depresses mesencephalic inhibition in voluntary
activity, the automatic activity of the bulb spreads along the
efferent paths determined by heredity or acquired by habit,
making use of the spinal mechanisms and the energy accumulated
therein. This schematic concept undeniably agrees with the
phenomena exhibited by the marsh tortoise , but its applicability
to other amphibia and reptiles, and still more to other classes of
vertebrates, is very doubtful.
V. Eolando (1809) first observed the effects of removing the
cerebral hemispheres in birds, but he confined himself to observa-
tions made shortly after the operation. Flourens (1822) used
his experiments on pigeons as the basis of his general theory of
the functions of the cerebral hemispheres. He experimented on
other classes of vertebrates with the single object of controlling
and generalising from the data acquired on pigeons, which
ix MID- AND INTER-BRAIN 501
became the starting-point of all subsequent researches on the
cerebral centres down to the present day.
According- to the classical description of Flourens, the pigeon
deprived of its cerebral hemispheres is an animal condemned to
perpetual dreamless sleep. None of its senses are active ; it
remains motionless wherever it is placed; it never moves
spontaneously, and stays in the sleeping posture (Fig. 256). If
stimulated it seems to wake, opens its eyes, shakes its wings,
moves a little, and then relapses into slumber. If thrown into
the air it flies, but fails to avoid obstacles. It retains the capacity
of keeping its equilibrium both while standing, and in moving
when stimulated. It has completely lost the faculty of feeding
FIG. 256. — Pigeon deprived of its cerebral hemispheres in position described by Flourens.
(From a photograph by Dalton.)
by itself, so that it will starve in front of a heap of corn. It
shows no fear when any one approaches or threatens it, nor any
inclination for the other sex. It digests well when fed, and can
consequently survive for a long time. It digests sleeping; and
only makes a few aimless steps occasionally, owing to fatigue in
the legs. In short, the pigeon that has lost its fore-brain has lost
all its perceptions, all its instincts, all its intellectual faculties.
But none of the physiologists who repeated Flourens' experi-
ment were able to convince themselves of the accuracy and
constancy of his description, nor that the ablation of the hemi-
spheres sufficed to produce total abolition of sensation in general,
and more particularly of vision and hearing. They found that
pigeons with no hemispheres were capable of avoiding obstacles
when they moved, of following the movements of a lighted candle
with their head, of starting violently at loud noises, as the report
of a pistol — in a word, gave obvious signs of seeing and hearing.
502 PHYSIOLOGY CHAP.
In this connection the experiments of Magendie (1825), Bouillaud
(1850), Longet (1847), Keuzi (1863), and Lussana and Lemoigne
(1871) are highly important. It was the observations of these
authors as a whole that laid the foundation of the generally
accepted psychological distinction between crude sensations or
simple psychical impressions on the central sense-organs, and per-
ceptions or sensations elaborated by the intellectual centres and
referred to the external world. The former are also termed
unconscious or passive sensations, the latter conscious or active
sensations. Only the last are dependent on the cerebral hemi-
spheres, while the first depend on the thalamencephalon, mid-
brain, the pons, medulla oblongata, and cord.
To explain the discrepancy between the results of Flourens
and those of Magendie, Longet and Eenzi, it is not enough to
insist on the inhibitory effects of traumatism, since we know that
Flourens — unlike Eolando — succeeded in keeping decerebrated
pigeons alive for a long time and in observing them for months.
Clearly he must have excised the whole or greater part of the
optic thalami which represent the 'tween-brain, along with the
hemispheres. Longet was the first who attached great importance
to the exact delimitation of the cerebral lesions, and he obtained
animals deprived of their hemispheres only, without injury to the
optic thalami.
H. Munk (1883) resumed the experiments on pigeons, with
the object of deciding the old controversy between Flourens, who
concluded that the pigeon deprived of its cerebral lobes " a perdu
tous ses sens," and his successors, who held with Cuvier "que
les lobes cer^braux sont le receptacle ou toutes les sensations
preunent une forme distincte, et laissent des souvenirs durables."
As we shall presently see, H. Munk in his experiments on
dogs and monkeys came to the conclusion that the destruction of
certain segments of the cerebral cortex produced total blindness
in these animals. If what happens in dogs can also be observed
on birds, Munk thought it certain that complete extirpation
of both hamispheres must produce results similar to those so
excellently described by Flourens, who alcne had made observa-
tions on completely decerebrated birds. The error would then,
according to Munk, lie, not with Flourens, but with his successors,
by whom the cerebral hemispheres of the pigeons were only
destroyed incompletely. This operation is more difficult than
any other to carry out accurately on account of the uncontrollable
haemorrhage.
Eighty per cent of Munk's pigeons perished. Of the twenty-
five that survived, four only were found at the post-mortem to
have been completely operated on. These had been subjected to
repeated experiments for months after the operation. They were
totally blind, and behaved exactly as Flourens described. If
ix MID- AND INTEK-BEATN 503
l>l;iced on the edge of a table they often went over it and fell to
the ground. They stumbled against obstacles; the brightest
light anil blackest dark produced no effect other than a pupil
reaction (myosis or inydriasis). If flung into the air they always
fluttered down, and on reaching the ground continued to flap
their wings for some time before they became quiet ; they
blundered against obstacles during their flight, and if this was
impeded, tumbled to the ground.
In seeking to account for the disparity between these results
of Munk and those previously described with no less care by
Longet, we were led to think (1885) that the four pigeons
examined by Munk had become blind from the effects of degenera-
tion descending to the thalami and optic lobes, which Munk did
not examine directly. It is certain that the more recent experi-
Fio. -257. — A, brain of normal pigeon — from nature, enlarged \. a-c, brain of a pigeon in which
Schiuder had extirpated both hemispheres, sparing the optic thalami and optic lobes— also
magnified J. a, from behind ; li, from front ; c, from the side.
merits of Schrader (1889), due to the effects of total destruction
of the cerebral hemispheres of pigeons, accurately performed, pro-
duced a perfectly different set of symptoms from that described
by Munk.
Schrader lost 75 per cent of the animals operated on, fourteen
pigeons survived. Many of these were killed after four months,
after they had been closely and frequently examined. Some died
in the fourth or fifth week with signs of progressive weakness,
probably the effect of descending degeneration. The post-mortem
examination performed by Recklinghausen showed completely
successful ablation of the hemispheres with no lesion of the optic
thalami.
In the first three to four days after the operation, according
to Schrader, there is the condition of sleep and absolute immobility
described by Eolando and Flourens. After this period the animals
begin to move about in the laboratory, very slowly at first and
quicker by degrees till they recover their normal gait. This
active movement cannot be ascribed to traumatic irritation, since
504 PHYSIOLOGY CHAP.
the periods of activity alternate regularly with those of rest and
quiet sleep during the night.
From the outset these spontaneous movements are guided by
visual sensations, for the animals are capal >le of avoiding obstacles
of any kind as perfectly as normal pigeons. The movements
are regulated perfectly by tactile sensations, and all changes of
equilibrium are exactly compensated. Sounds and noises, on the
contrary, have no influence on the course of the movements,
although hearing is not lost, since the sound of striking a match
makes the pigeon start.
The brainless pigeon can easily be inhibited in its movements.
If it is touched lightly, or taken up and set down again, it will at
once throw its head back, ruffle its feathers, and sleep.
By special experiments it has been shown that the decerebrated
pigeon is capable of making definite purposeful movements.
When, for instance, it is set on a perch that hardly supports its
feet, 6 feet above the floor of an empty room, it decides after
long hesitation to fly, and drops to the ground in a gentle curve.
If, again, a horizontal support is placed at the same height a
few yards away, the bird much sooner resolves to leave its uncom-
fortable perch, and flies to the firmer support. If a stool is then
set a yard away from the bough, the pigeon drops first on to the
stool and then to the ground. But while capable of flying down,
it never attempts to fly up. It seems doubtful whether it is able
to feed itself.
The brainless pigeon shows by its voice and movements that
it is capable of sexual excitation, but it is indifferent to the
presence of the female. Nor does she in turn trouble about the
young birds that surround her and follow her. Decerebrated
pigeons are equally destitute of the sense of fear; their move-
ments are governed by the size, form, situation of surrounding
objects, but to these themselves they remain entirely indifferent,
whether they be animate or inanimate, friend or foe.
In conclusion, it can be affirmed from Schrader's observations
that the fore-brain of the pigeon is neither a sensory nor a motor
centre, since its total absence causes neither loss of movement nor
of sensation. But the decerebrated, as compared with the normal,
pigeon shows marked defects which are most readily explained
as the loss of memory impressions of previous sensations, owing
to loss of intelligence properly so-called. All the actions of
pigeons without fore-brains, however varied and complex, show a
regular and definite direction. They have the character of the
responsive movements of Goltz, that is, they are to a large extent
determined reflexly by the excitations which come from the
periphery to the sensory centres of the thalami, optic lobes, and
medulla oblongata. As a whole, they give an idea of the very
important functions dependent on the remaining portions of the
ix MID- AND INTEE-BEAIN 505
brain. In the absence of adequate researches, it is not at present
possible to distinguish which portion of these functions belong to
the 'tween-] train, hut it may be assumed with great probability
that Flourens' classical description of the pigeon destitute of
sensation and spontaneous movements corresponds with what is
observed when the inter - brain is destroyed along with the
fore-brain. Certain observations made by Schrader on pigeons
in which ablation of the hemispheres was associated with very
extensive lesions of the optic thalami, tend to confirm this opinion.
He found that under these conditions the animal collided with
obstacles, and was unable promptly to correct slight passive dis-
placements of the extremities.
VI. The effects of total destruction of the cerebrum in small
mammals was frequently investigated by Flourens ; but it was
reserved for later observers to give an accurate account of them.
On this point again the results obtained by H. Munk are in
fundamental contradiction with those of other workers. He
experimented on rabbits, guinea-pigs, and rats. The first,
according to Munk, survive at most two days ; guinea-pigs and
rats four days. Death is not due to inanition, because they lose
only 7 to 20 per cent of their weight ; but to inflammatory reaction
and progressive softening of the remaining parts of the brain.
In the first stage the decerebrated animal remains motionless
and passive like Flourens' pigeons. In the second stage the
animal makes a few rare isolated movements, occasionally a few
steps to left or right. Eespiration is quicker and deeper, and
after a few hours the animal begins to walk. The third stage is
characterised by periodic walking, such as Fano described in the
brainless tortoise. In rabbits, guinea-pigs, and rats, when deprived
of the prosencephalon, the pupil reflexes persist but the animals
are not otherwise affected by light. In walking they collide with ^
every obstacle they meet, go straight ahead without altering their
course, and run up against the wall of the room, or fall off the
table, in short, they show complete lack of the visual sense.
Widely different and, as regards vision, exactly contrary
results were obtained by Christian! in rabl >its after excision of the
cerebral hemispheres, including the corpora striata, but sparing
the optic thalami. Directly after the operation the animal
remains motionless, but it escapes if excited. If kept awake it is
capable of spontaneous movement, but relapses into sleep if left \
alone. In provoked or spontaneous movements nothing abnormal
occurs ; the animal avoids obstacles without touching them with
its nose, and is even capable of jumping up and climbing without
stumbling. Obviously, therefore, its movements are guided by
the sense of vision.
If in addition to the prosencephalon the thalamencephalon
also is extirpated or profoundly injured, Christian! noted that the
506
PHYSIOLOGY
CHAP.
rabbit is not capable of maintaining equilibrium either in standing
or in walking.
The observations on rabbits and other small mammals were
only made during one to two days, beyond which he was unable to
keep them alive. They are important as showing that the motor
and sensory functions which persist can be carried out independently
of the parts of the brain that were destroyed, but they do not
permit us to ascertain how far the loss of function is due to
removal of the organs, or to the effects of operative traumatism.
All-important and unique in the
Literature of the subject are the re-
searches and observations of Goltz
(1892) on three brainless dogs which
he succeeded in keeping alive for some
time. The first lived fifty-seven days,
the second ninety-two days, the third
was killed by bleeding after eighteen
months. The right hemisphere was
destroyed in a single operation ; the
left in three operations ; the frontal
and parietal lobes were first removed,
next the temporal lobe, and lastly the
occipital.
In the third decerebrated dog, on
which Goltz made minute observa-
tions which he carefully recorded, the
post-mortern examination by Schrader
showed as follows (Fig. 258) : medulla
oblongata and cerebellum perfectly
normal, but the pyramids had dis-
appeared ; the left anterior quad-
rigeiniiial body was much flattened,
FIG. 258.— Brain from Goltz celebrated « , , . ,
"brainless dog." (Explanation in shrunken, soitened, and greyisn-
yellow in colour, and the left pos-
terior quadrigeminal body showed the same change to a slight
degree. The rest of the left fore-brain with the optic thalamus
measured 1'7 cm. in length; it consisted of a softened greyish
mass, which was mainly the remains of the corpus striatum
and thalamus. The remains of the right fore -brain with the
thalamus of that side measured 3 cm. in length. Besides the
degenerated portions of the corpus striatum and thalamus, a soft
brown residue of the cornu Ammonis could be seen. The right
optic nerve was smaller than the left and grey in colour, while
the colour of the left was normal.
The phenomena manifested by Goltz' "brainless dog" are
therefore characteristic of an animal deficient not only in the
entire cortex of the fore-brain, but also in a large part of the
ix MID- AND INTER-BRAIN 507
basal ganglia and a lesser extent of the corpora quadrigemina.
The phenomena of deficiency observed in this animal cannot be
attributed exclusively to the fore -brain, but are partly due to
damage of the thalaniencephalon and mid -brain as well. To
summarise the phenomena observed by Goltz :—
On the third day from the last cerebral ablation, the animal
began to walk of itself in the room. Its capacity for locomotion
increased rapidly, so that after a month it was able to climb a
plane sloping 20° without difficulty.
After a few months there was marked disturbance of nutrition,
with progressive emaciation of the posterior half of the body. By
means of careful feeding, however, this progressive emaciation was
partially repaired and arrested, though the stability of movement
which the animal exhibited a few weeks after the last operation
did nou return.
According to Goltz, the cause of this emaciation was to be attri-
buted partly to the fact that the animal moved continually within
its cage, so that its intervals of rest and sleep were less than in
normal dogs ; partly also to imperfect thermal regulation, which
made it give off more heat than the normal. Otherwise it slept '
curled up like a normal dog ; it breathed more rapidly when kept
in a heated atmosphere, and shivered and trembled in a cold place.
Digestion was normal ; there was no foul smell from the \
mouth, and the faeces were normal in colour and consistency. The
urine never contained sugar or protein after the first few days
from the final operation.
During the eighteen months of observation the animal never
evinced any sign of sexual desire.
After emaciation was arrested the animal moved fairly
steadily on uneven ground ; but it readily slipped on a smooth
floor, though it was capable of recovering itself without aid. It
never walked on the dorsa of its feet. If its limbs were placed in
an abnormal position, it reacted at once so as to correct this. If
it was placed upright on a table and the support suddenly with-
drawn from one leg by pulling away a leaf of the table, the leg
dropped a little, but was at once drawn up without loss of
equilibrium. After hurting one of its hind-legs, it trotted about
on the three sound limbs, and spontaneously held up the injured
one. These phenomena showed that the muscular and cutaneous
senses were not entirely lost after destruction of the hemispheres.
Although the regulation of the movements was maintained,
the animal was never capable of finding the place at which any
one had touched it. II', for instance, its left hind-leg was pulled,
it turned its head sharply to the point of contact, and tried to
snap, but seldom succeeded in reaching the hand.
The sense of touch was considerably blunted. On blowing
through a glass tube between the hairs of the dorsuni of the foot or
508 PHYSIOLOGY CHAP.
near the nose the animal did not react, hut the inside of the ear
remained sensitive to this stimulus. The animal reacted vigorously
to stronger stimuli, and awakened if asleep. If pinched or pricked
at any point of the skin while wandering about, it showed annoy-
ance by its movements and voice, or by biting.
The sense of taste remained ; if offered two portions of meat in
two dishes, one dipped in milk, the other in solution of quinine
sulphate, it chewed and swallowed the first, and rejected the
second after taking it into its mouth and biting it.
The sense of smell was of course absent, since the olfactory
lobes had been destroyed, but the nasal branches of the trigeminus
sufficed to produce a reaction in presence of ammonia vapours,
and sneezing with tobacco-smoke.
The sense of hearing was much reduced ; the blare of a
trumpet was required to arouse it from sleep.
In regard to vision it was noticed that the pupils of both eyes
contracted sharply to light, and if a flash of light from a dark
lantern was suddenly turned on the animal in the dark, it shut
its eyes and turned its head away. On the other hand, it was
unable to avoid obstacles by sight. The fixed stare of its expres-
sionless eyes lasted unchanged till death, even when threatening
gestures were made or a cat or rabbit was brought in front of its
eyes. Still, according to Goltz, it could not be termed wholly
blind, as it shut its eyes and turned its head aside in presence of
light.
The intelligence of the animal was very much reduced. It
remained mute and indifferent alike to caresses and threats. Yet
it did not lose its sense of hunger and instinct to feed. When
hungry it moved about in its cage, put its tongue out rhythmically,
and made mastication movements with its jaws. If set on a table
with a dish of milk and pieces of meat near its nose, it began at
once to lap, chew, and swallow with evident satisfaction, like an
ordinary dog. In proportion as the stomach filled, the mastication
movements became slower, and finally, when it had taken 500
grins, flesh and 290 grms. milk, it left off eating. The animal was
incapable of finding the way to its food ; if the meals had not been
placed in front of its nose it would have died of inanition in the
presence of abundance of food, like Flourens' pigeon.
Goltz' dog, accordingly, differs from the decerebrated fishes
and frogs of Steiner and Schrader, which captured worms and
flies ; but it must not be forgotten that in this animal, not only
was the fore-brain absent, but almost all the thalamencephalon,
and part of the mid-brain as well. " A dog with intact 'tween-
brain and normal optic nerves would undoubtedly exhibit more
phenomena than our dog, notwithstanding the loss of the cerebral
cortex and corpora striata " (Goltz).
This prediction has been verified by the work of Eothmann,
ix MID- AND INTEE-BEAIN 500
given iu one of his earliest communications to the Medical Society
of Berlin in 1911. He exhibited a dog operated on at two
sittings, two years and three months previously, the two cerebral
hemispheres being completely removed with the exception of
certain parts of the base, which had to be spared in order not to
damage the chiasma and optic tract.
After becoming emaciated, it recovered its initial weight of 12
kgrms. It began to walk after two days ; in a couple of weeks it
could feed itself. Its mode of barking and eating was perfectly
normal. After a few months it was capable of walking and
running. When teased by pinching it tried to bite; but quieted
down when its head was stroked. The sense of position was not
completely lost in the limbs, but when set on a table with one leg
hanging down, it did not attempt to bring it back into a normal
position. Although it appeared to be blind it had regained the
winking reflex by the end of the second week, and when a sound
was made, it turned its head back and pricked up its ears.
Mental activity was not entirely absent ; Eothmann saw the proof
of this in the, fact that the dog learned to adapt its movements to
the oblong form of its cage. He concluded that the lower centres
are capable, by daily practice and education, of co-ordinated
movements directed to an end, and of assuming eventually part of
the activities which normally belong to the fore-brain.
Eothmann has not yet published his complete work, giving the
post-mortem description of the brain and a detailed account of the
symptoms, which are (indispensable in making a comparative study
between this animal and Goltz' dog.
Goltz' observations show that the most important phenomena
of deficiency observed after the destruction of the brain are the
loss of all the manifestations or expressions from which we draw
conclusions as to the memory, reflection, and intelligence of the
animal. All the sensory and motor functions essential to life,
save those of seeking food, may be executed, even if imperfectly,
1 >y the surviving centres. The dog without a fore-brain is capable
of feeding itself when the food is presented to it ; of moving with
tolerable regularity, under the guidance of muscular and cutaneous
sensations ; possibly also of sight and hearing when the thalam-
encephalon and mid-brain are intact ; and of passing alternately
from the waking to the sleeping state like the normal dog. The
prosencephalou is not necessary in any absolute sense for all these
functions, most probably because their highest representation
is in other parts -- particularly in the thalamencephalon and
mesencephalon.
Flechsig holds everything Goltz observed in the dog to be
partially true of man also. He saw a new-born infant, in whom
only the basal parts of the brain, including the posterior corpora
quadrigemina, existed, while the hemispheres, thalami, and anterior
510 PHYSIOLOGY CHAP.
corpora quadrigemina were absent. The child only lived a day
and a half. During this time it cried and showed signs of dis-
comfort, and when the skin was pinched, its cries and associated
movements of the limbs became more marked. Heubner observed
a human anencephalous infant that lived sixteen days, and behaved
exactly like a normal child of the same age.
Normal new-born infants who have no intellectual psychical
activities cry, like Goltz' dog, when they are hungry or distressed ;
after being suckled and laid comfortably to rest they become quiet
and sleep. Dements, again, and low-grade microcephalic idiots are
comparable to the brainless dog ; they are men without a brain,
who have no intellect or memory, but who nevertheless possess
sensory and motor capacity. Their special senses persist ; they
experience sensations of hunger and thirst, and their acts are
directed to satisfying their needs ; they react to painful sensations
by movements of defence and cries of distress. It is therefore
evident that profound dementia, i.e. the complete absence of the
higher psychical faculties, does not necessarily imply loss of the
lower faculties.
In monkeys, too, the fore-brain has been removed by Karplus
and Kreidl (1912) at the Physiological Institute of Vienna.
Macacus rheus bears the complete extirpation of one hemisphere
well. In a few hours it is able to assume the sitting posture in
its cage — and to feed itself by means of the limb of the side operated
on. The whole of the opposite side shows grave disturbances in
movement and sensation, but a large part of these disappear in
the course of a few weeks. For months, however, the monkey
feeds itself almost exclusively with the hand of the side operated
on ; only when this is prevented does it use that of the opposite side.
After the extirpation of the second hemisphere the results were
less successful ; only two monkeys survived for two weeks. The
extremities, which were paretic after the first operation, were
moved more freely and frequently after the second than the limbs
of the other side. The monkeys were alternately in a state of
waking and sleeping ; the sleep lasted longer than the waking
period, during which they opened their eyes, moved, and reacted
freely to various" stimuli. The movements of the head and eyes
are normal, those of the limbs much altered. One of the animals
a few days after the second operation succeeded in assuming the
sitting posture with its head erect, in eating with the hand that
had become paretic after the first operation, and in suspending
itself for some minutes to the bars of the cage, after which it shut
its eyes, bent its head, and relapsed into the sleeping state.
Light stimuli caused the, pupil to contract but produced no
other reaction. Strong auditory stimuli roused the monkey
from sleep, and when awake it produced not only reflex move-
ments of the ears, but also movements of the head and of the
ix MID- AND INTER-BRAIN 511
limbs. Tactile stimuli evoked complex movements as well as
simple reflexes.
It would be of the greatest interest to obtain a long survival
after complete decerebration in monkeys, in order to see how
far the phenomena of deficiency can actually be modified.
H. Munk put forward a number of ingenious objections to
the effect that all the phenomena described by Goltz in the
brainless dog can be explained as simple reflexes, not necessarily
accompanied by any psychical activity. He holds that the sense
centres by which we are normally brought into relation with the
external world are protected against the abnormal and injurious
effects of certain peripheral stimuli by a mechanism which evokes
ordinary reflex movements, unaccompanied by sensations, which
ward off or remove the stimuli from the nerve-endings, while at
the same time they can arouse sensations so that conscious and
voluntary movements co-operate to the same purpose. These
common protective movements, whose reflex centres lie below the
fore-brain, persist in the dog without cerebral hemispheres.
In the next chapter we shall return to Munk's theory. Here
we need only point out that Goltz declines to consider the
brainless dog, which sleeps when replete, is restless when its meal
is delayed, and tries to bite the hand that teases it, as a mere
reflex machine, an insensitive automaton. If these complex acts
are unmistakable signs of wants, feelings, sensations in the
normal dog, why are they less so in the dog without a cerebrum ?
Munk and those who agree with him show a tendency to
limit the material basis of psychical phenomena as much as
possible, and to ascribe them solely to the cerebral cortex, perhaps
with the object of facilitating the solution of certain problems.
Nevertheless the riddle of the " psyche " remains, whatever theory
of sensibility and consciousness is accepted.
The theory of Loeb — one of the most distinguished of Goltz'
pupils — comes very near that of Muuk. Starting from Munk's
position that consciousness is a function of memory, because when
memory is lost, as in fainting, deep sleep, and in stupor due
to certain poisons, consciousness is simultaneously suspended,
Loeb concludes that the prosencephalon is indispensable to
memory, and consequently that the brainless animal is an
automaton entirely destitute of personality or consciousness, but
he adds a reservation which does not seem important in view of
the experimental observations of Schrader and Goltz. Loeb
shrinks from going so far as to assume that the fore-brain is the
organ of consciousness. "The organ of consciousness may well
be the whole brain or the whole of the central nervous system so
long as it is connected with the fore-brain, and the latter may
be indispensable only in the activity of memory associations."
A critical examination of this theory would take us too far
512 PHYSIOLOGY CHAP.
from our subject. It is only necessary to remark that there is
this difference between the views of Munk and Loeb. Accord-
ing to Munk, the brainless animal has lost all its senses, including
sight and hearing, as assumed by Floureus. Loeb, on the contrary,
does not deny, but even confirms, the observations of Schrader on
pigeons and of Goltz on the brainless dog, but he holds that these
animals, while more or less guided reflexly by sensory impressions,
have no trace of consciousness, because they are destitute of
associative memory.
So long as there is no evidence to the contrary it may be
maintained that brainless animals are in a state of severe dementia
because they have lost memory and perception, but are capable,
of elementary internal and external sensations, by which their
automatic and reflex movements are regulated.
At a later point we shall discuss this question, and endeavour
to differentiate between the concepts of perception and of sensation.
VII. To determine the functional importance of the mesen-
.cephalon and thalameucephalon we need only sum up briefly the
results of the other experiments by which it has been attempted
to excite or destroy these parts separately, in order to examine
the effects and deduce conclusions as to their functions.
Direct stimulation of the roof of the mid-brain, which is
represented in birds, amphibians, reptiles, and fishes by the optic
lobes or corpora bigemina, in mammals by the corpora quadri-
gemina, gives positive results to electrical, mechanical, chemical,
and thermal excitation.
In the frog, electrical excitation of the optic lobes produces a
movement of the head towards the opposite side and upwards,
and sometimes also provokes quacking. According to Wilson, the
beats of the heart are slowed also. Chemical stimulation, as by
a crystal of sodium chloride applied to the optic lobes of the
frog, prolong the latent period of the movements evoked by the
cutaneous excitations ; sometimes there is complete inhibition of
reflexes, particularly if the cutaneous stimulus is of a painful
rather than a tactile character (Setschenow).
The optic lobes of amphibia contain centres which control the
sexual clasp. Albertoni demonstrated on toads and Tarchanoff
on tadpoles that mechanical stimulation, as pricking with a pin,
squeezing with a forceps, of the optic lobes at once ends the clasp,
while the same stimuli applied to the hemispheres and optic
thalariii have no effect 011 it. They interpret these observations
as meaning that there are inhibitory centres of the clasp in the
optic lobes, which are thrown into activity by the mechanical
stimuli. According, on the contrary, to Baglioni (1911) from
his recent experiments on toads, these are not inhibitory centres
but true excitatory centres of the clasp, which are in tonic activity
during the embrace, and are profoundly injured and put out of
ix MID- AND INTEK-BRAIN 513
action by mechanical stimuli, to which the centres are highly
sensitive. He found, in fact, that on employing electrical ex-
citation, which is more easily graduated and less destructive
than these injurious stimuli, the clasp is never interrupted, but
is actually strengthened. On the other hand the local application
of an anaesthetic, e.g. stovaine, to the dorsal surface of the optic
lobes is followed by interruption of the embrace.
In birds electrical stimulation of an optic lobe causes dilatation
of the pupil on the opposite side ; the head is also raised, and
various movements are made by the wing on the opposite side,
and by both feet (Ferrier).
Kschischkowski has recently (1911) in our laboratory employed
Baglioni's method of specific chemical stimuli (strychnine and
carbolic acid) applied locally, in order to discover the nature of
the central elements which constitute the superficial layers of the
optic lobes in the pigeon. He found that the application of
strychnine and picrotoxiu caused contraction of the skeletal
muscles of the fore- and hind -limbs and of the neck on the
opposite side. It is only when the poison is applied in larger
quantities or to a greater surface (1-2 sq. mm.) that contractions
of the homolateral muscles with circus movements towards the
same side occur. These phenomena of excitation set in a few
seconds after the application of the stimulus and last for some
minutes. Since the application of carbolic acid has no effect, we
may conclude that the elements of the superficial layer of the
optic lobes are, in relation to this chemical stimulus, of the same
character as the central elements of the dorsal half of the cord,
as well as the cells in the excitable cortex of the dog, since these
also have the specific property of reacting to strychnine and
picrotoxin and not to carbolic acid, which, on the other hand,
produces a reaction from the motor cells of the ventral horn (see
above, pp. 264 et seq.}.
In mammals faradisation of the anterior quadrigeminal body
produces pupillary dilatation on the opposite side, and at a later
stage on the same side also, and conjugate deviation of the eyes
upward and towards the opposite side, with retraction of the ear
and angle of the mouth. The same stimulus applied to the
posterior quadrigeminal body produces erection of the ear on the
opposite side and emission of cries.
Adamlik succeeded in producing different co-ordinated move-
ments of the eyes when he excited various points of the anterior
quadrigemiual bodies in the dog. After a vertical section in
the median plane the reaction only involves the eye of the side
excited.
Terrier, experimenting on monkeys, obtained similar reactions
to those seen in dogs. Unilateral electrical excitation of the
anterior quadrigeminal body produces wide dilatation of the
VOL. Ill 2 L
514 PHYSIOLOGY CHAP.
opposite pupil, followed shortly by that of the pupil on the same
side, with pronounced opening of the lids and raising of the
eyebrows. The eyes turn up and towards the opposite side ; the
head moves in the direction of the eyes ; and the ears are lowered.
If the excitation is prolonged the tail is raised, the lips spread
out, the jaws close, the angles of the mouth are drawn back as
far as possible ; the upper limbs are flexed at the elbow-joint,
adducted and drawn back. If the excitation is continued,
complete opistothomis results.
Excitation of the posterior quadrigeminal bodies in monkeys
produces the same effects, but there is further emission of sounds
of a character varying with the duration of the stimulus. The
motor effects which are at first confined to the opposite side
subsequently extend to both sides.
It is not easy to ascertain the value or physiological significance
of these experiments on the corpora quadrigemina with the
excitation method. The motor effects of electrical excitation may
depend on the transmission of the stimulus to the motor tracts
or to subjacent centres. At the same time they are evoked by
very weak currents, which are hardly perceptible at the tip of the
tongue. Other forms of excitation which are incapable of spread-
ing may also produce the same effects under certain conditions.
The phenomena produced by excitation of the corpora quadri-
gemiua are undoubtedly reflex in character, that is, they depend
on the transmission of an active state from the sensory centres
to the motor centres or tracts. The effects of momentary stimula-
tion of the mesencephalon strongly resemble the movements of
repulsion that take place when an object is suddenly brought near
the eyes, which makes it probable that the excitation gives rise
to subjective luminous sensations, and this reflexly discharges the
reaction movements.
Trismus, contraction of the facial muscles, and opistothonus,
which ensue on strong and protracted stimulation of the quadri-
geminal bodies, may be looked on as symptoms or manifestations
of pain. The dilatation of the pupil is a phenomenon of the same
character, since we know that it occurs with every sudden excita-
tion of the sensory nerves. So, too, the cries of distress due to
excitation of the posterior quadrigeminal bodies.
Danilewsky demonstrated that electrical stimulation of the
deep layers of the corpora quadrigemina produces a marked
increase in arterial pressure, which is associated with retardation
and reinforcement of the heart-beat. Eespiration is disturbed
too, expiration in particular being exaggerated. Probably these
effects are due, at least in part, to transmission of the electrical
stimulus to the subjacent cerebral peduncles.
Valentin and Budge found that electrical excitation of the
corpora quadrigemina also affected the viscera, producing con-
ix MID- AND INTEE-BEAIN 515
tractions of the stomach, intestine, and bladder. Hlasko stated
more definitely that there is a centre in the posterior corpora
quadrigemina for the contraction of the stomach which induces
vomiting. When these bodies are destroyed vomiting is no longer
produced by apomorphine. Frequently repeated vomiting may
occur in dogs in which the quadrigeminal bodies have been
partially injured, and therefore irritated, during extirpation of the
anterior vermis of the cerebellum. After three or four days the
vomiting ceases, probably owing to the cessation of the irritation.
VIII. The anatomical relations of the optic tracts with the
optic lobes and anterior corpora quadrigeniina show that these
ganglia are of supreme importance in vision. But the clearest
and most unmistakable demonstration of the different centres
that are in direct relation with the optic nerves, and therefore
function in vision, is given after extirpation of one eyeball in
young animals and in man ; this produces atrophy and partial
agenesis of the anterior quadrigeminal body and the external
geniculate body on the opposite side, as well as of the optic
thalamus and cortex of the occipital lobe, while the posterior
quadrigemiual body and internal geniculate body are spared.
Evidence for this is shown by the experiments and clinical
observations of Pauizza, Svan, Gudden, Ganser, Forel, and v.
Monakow.
Mayer, Flourens, and Budge, experimenting on pigeons and
dogs, first pointed out that the destruction of the optic lobes and
corpora quadrigemina produced loss of vision and immobility of
the, pupils. They noticed that these effects are crossed, that is,
unilateral destruction produces paralytic effects on the retina
and iris of the eye on the opposite side. Longet, Eenzi, Stefani,
and Miiuzer and Wiener confirmed these observations ; but found
that the blindness consequent on destruction of the optic lobes
was not complete. Lussana and Lemoigne stated that total blind-
ness, at least for a few days after the operation, occurred only
after destruction of the anterior corpora quadrigemina, and that
amblyopia only resulted from destruction of the posterior quadri-
geminal bodies. They further held that paralysis of the pupil
ensued only when these parts were seriously injured. Many
observers found that unilateral ablation of the quadrigemiual
bodies produced circus movements, but they do not agree as to
whether such movements were towards the healthy or the operated
side. Ataxia and disorders of equilibrium were further observed
after destruction of the quadrigeminal bodies, but they are not
unilateral and do not persist; probably they depend on injury
of the adjacent or subjacent parts. The same holds good for
functional disturbances of the internal ocular muscles, which
possibly depend on injury of the nucleus of origin of the oculo-
motor nerve.
516 PHYSIOLOGY CHAP.
" Stefani described the effects of destroying- both lobes of the
pigeon as follows : " After recovery from the destruction of the
optic lobes, they only show disturbance of vision, relative not absolute
blindness, perfectly comparable to that which follows the removal
of the cerebral hemispheres in these animals. The pigeon does
not fly away when I stretch out my hand to take it tip, nor does
it peck at the corn in front of it though hungry ; but it is able
to fly and to avoid obstacles, drops down, perches on objects, or
flies to the ground like the healthy pigeons ; while the pigeons
blinded by removing their eyes remain motionless, and when forced
to move only blunder against obstacles."
The experiments of Jappelli and Sgobbo (1900), who destroyed
the corpora quadrigemina in dogs by the ingenious method of
introducing a small galvano-cautery like a flexible sound, ending
in a tiny platinum loop, into the space between the. dura mater
and the cerebellum, are specially important. With this instrument
they succeeded in obtaining a clean and sharply defined, more or
less complete removal of one or other quadrigeminal body on one
side, which was aseptic and spared the other tissues. They kept
the animals alive till the resulting symptoms were fixed and
permanent, and correlated these permanent symptoms with the
degree and locality of the lesion. In this way they formed very
definite conclusions as to the functions of the corpora quadri-
gemiua, which partially confirmed those of the earlier observers,
partially corrected them, and added new results that harmonised
\vell with the most recent morphological investigations. We may
sum up the conclusions of this important work, keeping as closely
as possible to the terms in which they were formulated by
Sgobbo : —
(a) Visual disturbance in the eye of the opposite side results,
not only from lesions of the anterior quadrigeminal body, as many
authors suppose, but also from injury to the posterior body, as
had been previously noted only by Lussana and Lemoigne and
Bechterew.
(6) This disturbance consists, not in blindness, but in diminu-
tion of vision (amblyopia) in the whole visual field of the eye
on the opposite side. This agrees with the observations of Serres,
Renzi, and Stefani.
(c) Lesions of the posterior quadrigeminal body also produce
auditory disturbances (deafness and dullness of hearing) in the
ear of the opposite side, associated with paresis of the external ear
muscles. This observation is new, not having been made by any
previous authors. It agrees with the effects of electrical stimula-
tion of the posterior quadrigeminal body, which, as we see, causes
movements of the ear on the opposite side, and cries.
(d} The corpora quadrigemina do not contain centres for the
movements of the eyeball as other authorities supposed. After
ix MID- AND INTEE-BKAIN 517
lesions (if these bodies motor disturbances in the eye were either
totally absent or appeared only when the lesion was so extensive
as to involve the grey matter that surrounds the Sylvian aqueduct.
Hesen and Volkers and Bechterew came to the same, conclusion.
This contradicts the views of Terrier and of Adamiik, who con-
cluded from the excitation method that the anterior 1 todies con-
tained special centres for the conjugate movements of the eyes.
(e) Nor do the quadrigemina contain the centre for the move-
ments of the iris, disturbance of the latter being only seen when
the lesion extends to the oculo-motor nucleus, i.e. when it involves
the grey matter that surrounds the aqueduct of Sylvius. Lussana
and Lemoigne and Bechterew also assumed that the centre for
the iris was not situated in the corpora quadrigemina, but lay
deeper.
(/') Circus movements, paresis or paralysis of the limbs, and
disturbances of equilibrium appear as transitory phenomena when
the lesion is limited to the corpora quadrigemina. They must
therefore depend on the excitation or destruction of the subjacent
or surrounding parts. Circus movements which are usually
towards the side of the lesion are due to the hemiparesis, and
disappear as the latter wears off; the movements towards the
opposite side depend on the excitation of the, subjacent pyramidal
fibres and are quite transient.
Sgobbo follows up his series of experiments on dogs by a critical
review of the clinical cases described by various authors in which
post-mortem examination showed lesions limited to one or other or
both of the corpora quadrigemina, with a view of ascertaining the
functions of these ganglia in man.
After minutely analysing the complex symptomatology of these
cases, he came to the general conclusion that both isolated lesions
of the anterior and posterior corpora quadrigemina and lesions
involving both these bodies failed to produce any constantly
appreciable alteration in vision or hearing. It is possible that in
proportion as the prosencephalon acquires a greater importance in
the zoological scale the functional importance of the mesencephalon
in general, and of the quadrigemina in particular, may diminish.
For the better solution of this question it is desirable that a
methodical series of experiments should be carried out upon the
corpora quadrigemina of monkeys, which come nearest to man in
the relative development of these segments of the brain.
IX. The function of the centres of grey matter which lie deep
in the mid-brain and cerebral peduncles is very obscure and un-
certain. It is only known that lesions of the mesencephalon
produce forced movements as their immediate consequence.
Sherrington (1896) described some important effects of sections of
various extent, at the level of the mid-brain. In the monkey he
contirmed the fact that section in front of the mid-brain leaves
518 PHYSIOLOGY CHAP.
voice-production intact, while section behind it abolishes phonation.
He further observed a cataleptic condition in monkeys after section
in front of the mesencephalon ; reflex movements are carried out
with extreme slowness, and the attitudes assumed or passively
given are long sustained. He holds it probable that the tonic
spasms of epilepsy are due to excitation of the brain-stem, which
agrees with Ziehen's view that they are subcortical, while the
clonic spasms are cortical in origin. Verworn (1898) showed that
after decerebration it is much easier to evoke the state of forced
immobility known as hypnosis in the pigeon.
Sherrington (1898) described the persistent tonic spasm that
occurs in certain groups of muscles, after section of the brain in
front of the corpora quadrigemina, as decerebrate rigidity. This
symptom appears in apes, dogs, cats, rabbits, and guinea-pigs.
The contracted groups of muscles are the retractors of the head
and neck, the muscles of the tail, the extensors of the elbow, knee,
shoulder, and ankle. The foot and hand are but little concerned,
the ringers and toes not at all. In kittens this spasm may last
four days with little interruption. When it ceases it can easily be
evoked again by passive movements of the corresponding joints.
At first the spasm assumes the form of tonus ; subsequently it
becomes a tremor. In narcosis it dies down, and reappears as this
passes off.
The spasm depends on the integrity of the dorsal spinal roots.
In fact it does not appear, or only imperfectly, in the limits to
which the dorsal roots had been cut some days previously, and
it disappears if they are divided after it has set in.
During the state of decerebrate rigidity, stimulation of various
points of the central nervous system or of certain peripheral
nerves elicits reflexes which consist in relaxation of the contracted
muscles and contraction of the antagonists. Prolonged stimulation
sometimes results in rhythmical flexion and extension of the four
limbs, which by their co-ordination recall the complex of move-
ments present in quadruped progression (Chap. VII. et. seq.~).
After hemisection of the 'tween brain the same rigidity
appears, but it is far more marked on the side of the lesion
(Sherrington). The whole course of the effects of hemisection of
the mid- brain has been described by Probst (1904).
Probst experimented on cats. After dividing the right half of
the mid-brain midway between anterior and posterior corpora
quadrigemina, he noticed the phenomena which maybe summarised
as follows :—
Immediately after section on the right side there is curvature
of the body and head to the left side, with tonic contraction of the
musculature of the left side of the neck. The pupils are con-
stricted slit-wise, and after half an hour horizontal nystagmus may
be seen in the left eye alone. The jaws are closed, and there is
IX
MID- AND INTEE-BEAIN
519
tonic contracture of the left limbs. If the left hind-leg is passively
stretched, it remains extended while the right goes hack to its
former position. The animal lies on the left side.
An hour and a half after the operation the animal lies in the
position shown in Fig. 259, with its head turned to the left between
the two hind-limbs which are extended forwards. The right fore-
leg makes constant swimming movements ; the left limbs are
motionless.
The animal keeps up this forced position during the first three
days after the operation. The myosis diminishes, the nystagmus
ceases. Both motility and sensibility are greatly diminished on
the left, and it is necessary to feed the animal artificially.
On the seventh day the animal makes attempts to stand but
FIG. 250. — Forced curvature in cat to the left, after section of ri^ht side of mid-
brain and cerebral peduncle. (Probst.)
falls to the left. The left limbs are paretic and anaes-
thetic, and are only moved reflexly. The two pupils
are equal and react to light.
On the ninth day the animal begins to walk in a circular
direction to the left, but falls after a few steps. It begins to
support itself also on the left fore-leg, and can now turn its head to
the right.
On the eleventh day it can walk for a short distance, leaning
against the wall.
On the thirteenth day it walks better, but always in a circular
direction to the left; it frequently crosses its fore-limits. It has
regained the sensibility of the left limits; but does not correct the
abnormal position assumed by these limbs. It eats spontaneously.
On the twentieth day it still presents circus movements to the
left, but is able to jump off a chair. When called, it can turn its
head to the right, but still keeps up the forced position of the head
to the left.
520 PHYSIOLOGY CHAP.
On the twenty-first day both motor zones of the cerebral
cortex were exposed and stimulated by electrical currents. On
exciting the left sigmoid yyrus single contractions were evoked,
as well as epileptic fits confined to the right side. On exciting
the right sigmoid gyrus weak currents only elicited contractions
of the left ear and left facial muscles. Very strong currents
evoked weak contractions of the left limbs, but never epileptic
attacks.
From these facts observed after unilateral trausection of the
entire mid-brain of the cat it is clear that there is never total
paralysis of sensation and motion in the opposite half of the
animal. After three weeks it regains its capacity of walking and
jumping ; the forced postures and movements seen directly after
the operative act improve progressively, and the sensory disorders
improve rapidly.
Apart from the special cases we have been considering, it may
be stated in general terms that the intensity of the symptoms of
unilateral section of the mid-brain, including the cerebral peduncle,
depend on whether the transection is complete or not. One effect
of the coutralateral motor paresis is the circus movement of the
animal, which is generally to the opposite side, sometimes also to
the side of the lesion ; in the first case, which is the rule, the
curvature of the spinal axis predominates — in the second, the
greater extension of the limbs of the operated side, in comparison
with the paretic limb of the opposite side, prevails.
In the monkey, and more particularly in man, the effects are
greater. Clinical cases, no less than experiments on animals,
enable us to form an idea of the importance of the cerebral
peduncle, inasmuch as it contains the sensory and motor cerebro-
spinal conducting paths. In correspondence with the localisation
and extent of lesions of the peduncle there is crossed motor,
sensory, or mixed paralysis, partial or complete.
X. The physiology of the optic thalami leaves much to be
desired. This is due in great measure to the difficulty of attacking
these masses of grey matter without damaging the surrounding
organs. The method proposed and carried out by Lo Monaco in
our laboratory undoubtedly indicates considerable progress from
the point of view of technique. It consists in the partial transec-
tion of the corpus callosum, which produces no apparent disturb-
ance, and separation of the two hemispheres so as to expose the
thalami, in order to excite them or remove them entirely or in part.
Contrary to the vie\vs of other authors, electrical or other
stimulation of the thalami causes neither painful sensation nor
motor reaction, provided the stimulation does not spread to the
cerebral peduncles nor the anterior quadrigeminal bodies (Ferrier,
Lo Monaco). The effects of the destruction or removal of the
thalami varies according to different experimenters, and according
ix MID- AND INTER-BRAIN 521
to the operative methods employed and the greater or less lesions
of the adjacent parts.
The anatomical connections of the thalami with the other
portions of the 1 train (pp. 489 ct seq.) throw sufficient light on
this difficult suhject. Anatomical research, particularly the most
recent work of Dejerine and of Roussy, has proved that every part
of the cerebral cortex receives nerve-fibres from the optic thalamus.
On the other hand, the thalamus sends no fibres to the cerebral
peduncle or to the bulb and spinal cord; after destruction of the
thalamus no degeneration is seen either in the motor (pyramidal
tracts) or the sensory (lemniscus) paths.
The atrophy of the thalamus that follows excision of the
opposite eyeball (Panizza, J. Svan) shows the extreme importance
of the thalamus in vision. In the lower vertebrates the corpora
bigemina represent the principal station reached by the fibres of
the optic nerve ; but in the higher vertebrates the thalamic visual
centres are always larger in proportion to those of the mid-brain
(Gudden, v. Mouakow, Edinger, and others). Of the four masses
of grey matter into which the mammalian thalamus is divided, it
is the hindmost, the pulvinar, which directly ' receives the optic
fibres ; and the pulviuar and the external corpus geniculatum give
origin to the paths to the occipital region of the cortex and the
angular gyri (v. Monakow, Vialet, Ferrier, and Turner), which — as
we shall see iii the next chapter — represent the cortical centres
of vision.
Many fibres of the mesial fillet (lemniscus) terminate in the
lateral nucleus of the thalamus, and penetrate especially into its
ventral and posterior parts round the centre median of Luys. As
we know, this represents the continuation of the dorsal columns of
the spinal cord, and perhaps also Gowers' tract ; in a word, the long
spino-cerebral sensory paths.
From the lateral grey matter of the thalamus, fibres run to the
parietal and mesial regions of the cortex ; those to the Rolandic
area receive their medullary sheath very early, towards the ninth
month of foetal life. The fibres that run from the anterior part of
the thalamus to the frontal region of the cortex are late in acquir-
ing their sheath (fourth month after birth). A large system of
fibres that develops early unites the thalamus to the nuclei of
the corpus striatum, that is, the caudate nucleus and lenticular
nucleus. Lastly, the thalamus receives fibres from the superior
cerebellar peduncle, either directly or through the red nuclei.
These anatomical considerations as a whole naturally lead to
the conclusion that the thalamus is a great sensory centre, to
which a number of centripetal paths from different sensory organs
converge, and from which they spread out to the different regions
of the cerebral cortex. Broadly speaking, apart from exaggeration
and fancies, this was the theory sustained by Luys (1865-76)
522 PHYSIOLOGY CHAP.
on the basis of anatomical and clinical observations. Ferrier (1878)
adopted this same point of view, partially on the strength of an
experiment on a monkey. After dividing the thalamus in this
animal by an incandescent wire introduced through the occipital
lobe, he noted among other less definite phenomena cutaneous
hemianaesthesia on the opposite side, blindness, and pupillar
dilatation, from which he concluded that the thalami are centres
in which the sensory paths converge and are interrupted before
radiating to the cortex. He remarked that if the thalami are the
relay centres for the sensory tracts, it follows that lesions of these
ganglia must produce an alteration in the various forms of
sensibility. This fact seems to be better demonstrated by the
study of clinical cases than by experiments on animals. Many of
the cases described by Luys are not conclusive, since they are
tumours ; but certain cases of simple softening, confined more or
less clearly to the thalami, are very important from the physio-
logical point of view.
Among the most valuable and best described clinical cases is
one of Hughlings-Jackson's (1875). The post-mortem examination
showed a considerable depression on the posterior half of the right
thalamus. On sectioning it was found to be softened and greyish-
yellow in colour. The softening did not extend beyond the limits
of the thalamus into the white matter of the hemisphere and
peduncle, and its anterior half and the posterior half of the corpus
striatum were intact. No other lesions could be found in the
brain. The symptoms obviously present in life with this well-
defined lesion of the optic thalamus were as follows: Weakness
of movements on the left side, especially in the leg, marked
diminution of tactile sensibility on the left, diminution of smell
or at least of ordinary sensibility of left nostril, slight diminution
of taste in left half of tongue, doubtful loss of hearing in left ear,
and finally, left hemianopsia in both eyes, i.e. blindness of right
hall' of both retinae (bilateral homonymous hemianopsia).
Experimental researches, when uncomplicated by lesions of
other parts, partially confirm the results of clinical observation.
The prolonged researches of Lo Monaco (1898-1911) led to
the conclusion that of the effects of partial or total, unilateral or
bilateral extirpations of the thalami, the symptoms of visual
deficiency are the most prominent both from their gravity and
their persistence.
Lesions limited to the internal or external part of one thalamus
produce very marked amblyopia of the eye on the opposite side,
while the eye of the side operated on shows no alteration to
ordinary tests. This amblyopia is not permanent, but gradually
disappears within a few weeks. No defect of the other special
senses can be observed, but there is a diminution of tactile and
painful sensibility on the skin of the opposite side. The circus
ix MID- AND INTEE-BKAIN 523
movements noted by Magendie, and the hemiplegia described by
other authors, do not occur, though there is diminution of muscular
power on the opposite side. These symptoms disappear after a
few days.
When the unilateral ablation involves the posterior part of
tin- thalamus or the pulvinar there seems to be total blindness of
the eye on the opposite side, which apparently persists as long as
the animal survives. When the excision of the pulvinar is bi-
lateral the dog appears to be blind in both eyes ; immediately
after the operation its behaviour is similar to that of a dog in
which both eyeballs have been removed, but there is not absolute
permanent blindness. In fact, the animals had hardly recovered
from the operation when both began to walk, and they soon learned
to orientate themselves, to recognise the objects near them, and
thus to avoid them in walking.
Among Lo Monaco's experiments great importance attaches
to that performed on a dog in which the pulvinar was destroyed
on both sides, causing atrophy of the corpora quadrigemina and
the external geniculate bodies. In this animal there were obvious
visual disturbances that persisted during the eleven months that
it survived.
The dog exhibited a graver disturbance of vision than the
psychical blindness due to extirpation of both cortical visual
centres, but less than the blindness that results from extirpation
of both eyeballs.
In addition to visual disturbances there is, according to Lo
Monaco, a unilateral or bilateral affection of taste in dogs deprived
of the pulviuar on one or both sides, shown by the fact that one or
other half of the tongue, or the entire taste surface, is insensitive
to the bitterness of a saturated solution of quinine.
The sense of smell is also disturbed in dogs that have lost their
pulvinar ; they only perceive the odour of meat when it is placed
near their nostrils, while a dog blinded by extirpation of the eyes
recognises it at a much greater distance.
Lo Monaco found painful, thermal, and muscular sensibility
intact in dogs after removal of the pulvinar. After destruction of
the mesial or anterior nucleus of the thalamus, on the contrary,
tactile sensibility and muscular energy are reduced on the contra-
lateral side ; but not permanently, as no trace of diminution can
be recognised after a few days. The circus movements to the
opposite side are only seen during the first days after the operation,
and evidently depend on the prevailing action of the muscles of the
side operated on, or of the side on which the thalamus is more pro-
foundly and extensively injured.
Anatomical examination of the brains of the dogs whose
thalamus was operated on by Lo Monaco almost entirely confirms
the functional lesions observed during life. In a case of removal
524 PHYSIOLOGY CHAP.
of the anterior part of the thalamus the peripheral visual paths
(tract, chiasrna, optic nerves) were found to be completely normal ;
but there was partial degeneration of the optic radiations of
Gratiolet, which run from the thalamus and external geniculate
body to the cortex of the occipital globe. On the other hand, in
the cerebrum of the dog killed a year after the bilateral destruction
of the pulvinar, degeneration could be seen both in the peripheral
and central visual paths. In the peripheral paths the internal
side of the tract was degenerated, and in the central there was
partial degeneration of the bundle of Gratiolet, which was more
pronounced in its lower third. None of the experiments on more
or less extensive unilateral or bilateral extirpation of the thalamus,
on the contrary, showed any such degenerations in the sensory
paths of the fillet, which agrees with the fact that the disturbances
of cutaneous and muscular sensibility observed during life were
transient. This tends to some extent to modify the prevailing
anatomical concepts of the relations of the sensory paths with the
thalamus, and the too extensive interpretations given to the
symptoms observed in Hughlings- Jackson's case.
If the localisation of function in the several nuclei of the
thalami and the complex of sensory and psychical functions
carried out by the thalami is still uncertain, we know at least—
from the researches of Lo Monaco, in particular — that the pulvinar
is of great importance in vision, and also participates in the
functions of taste and smell. On the other hand, it would appear
that the sensory and motor disturbances observed in the early
post-operative period, specially after destruction of the anterior
nucleus, are simple effects of interruption of the thalarno-cortical
and cortico-thalamic fibres.
There are clinical facts in favour of the view that the thalami
exercise an influence on the mimetic or emotional manifestations.
But these are inconstant phenomena, the origin of which has not
yet been fully cleared up.
BIBLIOGRAPHY
The following are among the most important of the recent works : —
GOLTZ. Beitriige zur Lehre von den Functiouen der Nervenzentren des Frosches.
Berlin, 1869.
HUGHLINGS-JACKSON. Reprints of London Hospital Reports, 1875.
FKRRIEK. Functions of the Brain, 1876.
FANO. Arch, italiennes de biologie, 1883.
FANO. Pubbl-. del R. Istituto di Studi Sup. in Firenze, 1884.
FANO. La Salute. Genoa, 1885.
CHRISTIANI. Zur Physiologic des Gehirns. Berlin, 1885.
STEINEK. Die Functionen des Zentralnervensystems and ilire Phylogenese.
Brunswick, 1885-88.
BECHTEREW. Virchow's Arch., 1887-88.
SCHRADER, M. Pttiiger's Archiv, 1887 and 1889.
ix MID- AND INTEK-BRAIN 525
Mrxu, H. i'hor die Funktioiien des Grosshivns. Gesammelte
1890. Sitzungsbi-r. d. K. preuss. Akad. d. Wiss. zu Berlin. Jahrg. 1881-89.
l)u Bois-Reymond's Arch., 1884.
M<IXAKO\V. Arch. 1'. Psychiatric. 1888-92.
(i.n.TZ. Pfluger's Archiv, 1884-88-92.
VIA LET. Centres cerebraux dc la vision. Paris, 1893.
Lo MONACO. Rivista di patologia nervosa e mentale. Florence, 1897.
SHERRINGTON. Phil. Trans. London, 1896-98.
YERWORN. Beitriige zur Physiol. d. Zentralnervensy stems. Jena, 1898.
JAITELLI. R. Ace. Med. Chir. di Napoli, 1898.
FEIIUIER and TURNER. Phil. Trans. London, 1898.
I'.KTHE, A. Piliiger's Archiv, 1899.
SGOBBO. II Manicondo moderno. Nocera Inferiors, 1900.
DEJERINE, J. Anatomic des centres nerveux. Paris, 1907.
Lo MONACO. Sulla fisiol. dei talaini ottici, Raccolta di lavori di iisiologia e scienze
affini pel giubileo del prof. Luciaiii. Milan, 1900. Atti della R. Ace, dei
Lincei, 1910.
PROBST. Jahrbiicher f. Psych, u. Neurol., 1904.
ROUSSY, G. La Couche optique. Paris, Steinheil, 1907.
BAGLIONI. ZentralM. f. Physiol., 1911.
KSCHSCHKOWSKI. Zentralblatt f. Physiol., 1911.
ROTHMANN. Berl. mecl. Gesellsch., June 1911.
KARPLUS and KREIDL. Wiener klinische Wochenschrift, 1912.
Recent English Literature : —
GRAHAM BROWN. On Postural and Non-Postural Activities of the Mid-brain.
Proc. Royal Soc., 1913, B. Ixxxvii. 145.
SACHS. On the Structure and Functional Relations of the Optic Thalamus.
Brain, 1909, xxxii. 95.
CHAPTEE X
THE FORE-BEAIN
CONTENTS. — 1. General anatomy of telencephalon. 2. Structure of the cerebral
cortex or pallium. 3. History of cerebral localisation. 4. Excitable zone of the
cerebral cortex ; localisation in dog, monkey, man. 5. Physiological analysis of
motor reactions of cerebral cortex. 6. Inhibitory reactions. 7. Organic reactions
of cortical origin. 8. Epilepsy from cortical excitation. 9. The sensory-motor
area, deduced from effects of partial or total destruction of excitable cortex. 10.
Functions of basal ganglia or corpora striata (caudate and lenticular nuclei).
11. Visual area. 12. Auditory area. 13. Olfactory and gustatory areas. 14.
Association areas ; division of cortex into thirty-six areas, according to Flechsig's
embryological method. 15. Physiological analysis of speech disorders of cerebral
origin. 16. General theory of the psycho - physical functions of the brain.
Bibliography.
I. THE Fore-brain (prosencephalon, telencephalon, brain proper)
represents in man, as in all vertebrates, the most bulky segment of
the central nervous system. It originates in the primary cerebral
vesicle, from which at an early stage the two diverticuli, which are
known in the adult as the lateral ventricles, develop, while the
central portion of the vesicle is reduced to the small cavity of the
third ventricle. The walls of this cavity develop progressively in
the vertebrate series, and become the cerebral hemispheres.
The primary vesicle thickens at the base, where a large mass,
which ernbryologists call the basal lobe, develops. Its anterior
portion, from which the fibres of the olfactory nerve emerge, is
destined to constitute the olfactory apparatus ; the posterior part
is of a considerable size, and forms the so-called corpus striatum.
These masses are afterwards separated by a fissure from the more
conspicuous segment of the vesicle, the walls of which thicken
comparatively late, and form the mantle of the brain or pallium.
Fig. 260 is a good representation of the several parts or segments
of the human 1 >rain in its early period of development. Its various
parts are more or less developed in all mammals, both during
embryonic life and after development has been completed.
In the bony fishes the pallium is represented merely by an
epithelial layer ; in the cyclostomes the side walls alone begin to
thicken ; in certain species of selachians an enlargement takes
526
CHAP. X
THE FOEE-BRAIN
527
place in the lateral and frontal walls ; in amphibia and reptiles
the pallium is entirely composed of nerve substance; in birds and
especially in mammals it reaches a much higher development than
all the other brain segments together; and finally, in man it
attains the enormous development represented by the cerebral
hemispheres.
It is noticeable that while the development of the pallium of the
fore-brain proceeds pari 2^ssu with the higher psychical activity
of the animal, the olfactory apparatus and corpus striatum (which
develop from the basal lobe of the embryonic brain) present, like
FIG. 260. — Median section through brain of a human embryo in fifth week. (His.)
all the other segments of the cerebrospinal axis, comparatively
little difference throughout the whole scale of vertebrates.
The olfactory apparatus in the human foetus of two to four
months appears in the form of a hollow protuberance from the fore-
1 »rain ; but during development its walls thicken till the cavity is
completely obliterated. In the adult it is possible to distinguish
(Fig. 261) :-
(a) The olfactory bulb, which rests on the lamina cribrosa of the
ethmoid and receives through its pores the fibres of the olfactory
nerves that originate in the nasal mucosa ;
(&) The olfactory tract, which divides into two divergent roots ;
(c) The olfactory area, in which the median or grey roots of the
tract arise ;
(d) The posterior olfactory lobule, formed from that part of the
528
PHYSIOLOGY
CHAP.
cerebral cortex which appears on the surface of the anterior
perforated space.
The corpus striatum arises from the base of the telencephalon
in the cavity of the cerebral vesicles. Its position is invariable
from the tishes to man. Since it is covered by the pallium it
cannot lie seen in the intact brain; in teleosteans only, in which
the pallium is composed of a thin membrane, it is visible, and
composes the entire fore-brain. The fish's brain, according to
Edinger, may be morphologically compared with a human brain in
L.t.
G.s.
Ch.
FIG. 261.— Olfactory lobe of human brain. (His.) Kv,, olfactory bulb; T, tract; Tr.n., trig-one;
R, rostrum of corpus callosum ; p, peduncle of corpus callosnm, passing into U.S., gyms
subcallosus (diagonal tract, Broca); Br, Brora's area ; F.p., tissnra pnnia ; F.x., lissura serotina ;
' '.".. position of anterior commissure ; L.t., lamina terminalis ; ' //., optic chiasma ; T.o., oj)tic
tract; ?>.<>//., posterior olfactory lobe (or anterior perforated spare); m.r., mesial root; /.»•.,
lateral runt of tract.
which the hemispheres have been excised but the corpus striatum
left ; to show this it is only necessary to draw a section of the
fore-brain of a bony fish within the diagrammatic outline of a
human brain. As shown in Figure 262, the fibres of the corpus
striatum lie in the region occupied in mammals by the anterior
part of the internal capsule (cf. Fig. 247, p. 492). In the lower
vertebrates (fish, amphibia, reptiles) the pallium is little or not
at all developed as compared with the basal ganglion; in birds,
although the mantle is developed, the basal ganglia always
forms the. main part of the fore-brain; in mammals lastly, and
particularly in man, owing to the enormous development of the
pallium, the basal ganglia become a purely secondary part of
the brain.
X
THE FORE-BKA1N
529
In the
higher
vertebrates (birds and mammals) the basal
ganglion undergoes a further subdivision; the fibres which
descend from the pallium traverse it, dividing it into a lateral or
extraveutricular and a medial or intraventricular segment. The
first is generally known as the lenticular nucleus ; the second as
the caudate nucleus (Figs. 245, 246, 247). Both these nuclei of the
corpus striatum are united by
fibres to the nuclei of the optic
thalamus.
The caudate nucleus of the
human brain is pear-shaped
with the larger end anteriorly,
it lies in the wall of the anterior
horn of the lateral ventricle.
Its ventricular surface is
covered by a layer of ependyma
and of ciliated epithelium. The
mass of the ganglion consists
of a reddish -grey substance;
the microscope shows nerve-
cells generally pigmeiited in
the adult, most of which are
small and belong to Golgi's
second type with short axis-
cylinder processes running in
various directions, some into
the internal capsule (Marchi).
The lenticular nucleus is
separated from the caudate
nucleus by the layer of white
matter which forms the in-
ternal capsule. It is only
visible in sections of the hemi-
sphere (Fig. 263), in which it
appears lens -shaped. It is
smaller at both ends than the
caudate nucleus. Two white
lines or medullary laminae divide it into three zones, the outer
of which, the largest and dark red in colour, is known as the
putamen ; the two inner, of a yellower tint, are known as the
globus pallidus. Anteriorly these two nuclei of the corpus
striatum are united by their bases, and come into contact below
with another nodule of grey matter, the nucleus amygdalus, which
in its turn is continuous with the grey matter of the cortex.
The cells of the lenticular nucleus contain yellow pigment, and as
a whole resemble those of the caudate nucleus, but many of them
belong to Golgi's first type — i.e. they have long axis-cylinders.
FIG. 2li'2. — Frontal section through 1'ore-lirain of a
teleostean, Corrina nii/ni, din-ctcd obliquely
behind and down. Round this the outline of
a mammalian cerebrum is drawn, to show the.
relations between tin- basal ganglia and the
pallium. (Edinger.)
VOL. in
2 M
530
PHYSIOLOGY
CHAP.
The nuclei of the corpus striatum are connected by nerve-
fibres ; other fibres run to adjacent parts of the internal capsule,
to the corona radiata and to the cortex.
The internal capsule is the mass of white fibres situated
between the lenticular nucleus, caudate nucleus, and the optic
thalamus (Fig. 263). In front, behind, and above it is continuous
with the white matter of
the hemispheres, and is
composed of fibres that
spread out like a fan-
whence the name corona
radiata. Below, the fibres
of the internal capsule and
corona radiata are con-
tinuous with the pes of the
cerebral peduncle. In hori-
zontal sections, as in Fig.
263, the internal capsule
presents a knee, the anterior
and posterior segments join-
ing at an angle of about
120°. Clinical observations
have led to the conclusion
that the fibres running in
the middle third of the
internal capsule, i.e. those
along the globus pallidus
of the lenticular nucleus,
are in connection with the
part of the cerebral cortex
which we know as the motor
area ; those of the anterior
third with the prefrontal
region ; and those of the
posterior third with the
temporo-occipital regions of
the cortex.
The localisation in the
internal capsule of the fibres
from the nuclei of the corpus striatum, the optic thalamus, the
subthalamic region, and the cortex of the opposite hemisphere,
through the great interhemispherical commissure of the corpus
callosum, is not exactly known.
The cerebral mantle in the higher vertebrates, particularly in
man, comprises the greater part of the mass of the cerebral
hemispheres; it is divided by the sulcus longitudinalis and united
by the corpus callosum.
FIG. 263. —Horizontal section through part of cerebral
hemisphere. (Schiifer, after Shattock.) Natural
size. The section is viewed from below ; V.Z., lateral
ventricle, anterior horn; c.c., corpus callosum ;
s.l., septum lucitlum ; a./., anterior pillars of fornix ;
v3, third ventricle; tli, optic thalamus; st, stria
terminalis ; c, nucleus caudatus, and «./., nucleus
lenticularis of corpus striatum; i.e., internal capsule;
</, its knee or genu ; n.c., tail of nucleus caudatus
appearing in descending horn of lateral ventricle ;
cl, claustvum ; /, island of Reil.
THE FORE-BRAIN
531
Each hemisphere presents an outer convex surface lying in
the vault of the skull; a Hat inner or mesial surface forming one
side (if the longitudinal sulcus ; and an irregular lower surface in
which there is the deep fissure of Sylvius. As shown by Figs.
264, 265, 266, all three surfaces 'of the cerebral hemispheres
present numerous fissures or sulci, marking out as many smooth
and winding projections, the convolutions or gyri. The surface
of the brain is enormously increased by this folding into sulci
and irvri. The extent of the infolded surface is estimated at
o*/
double that of the visible surface.
The membranes that envelop the brain resemble those of the
Fir;. 204.- External aspect of left cerebral hemisphere. The names of the gyri and lobules are
marked in Roman type ; those of the sulci and fissures in italics.
spinal cord in structure. The pia mater, which is very rich in
vessels, dips down into the bottom of the sulci, while the arachnoid
passes from one convolution to the next without penetrating between
them ; the whole floats in the sac of the dura mater.
The primary sulci, which are seen in the foetal human brain
and in adult apes, must be distinguished from the secondary sulci ;
the former divide the hemispheres into lobes, the latter subdivide
the lobes into gyri or convolutions.
The primary sulci are the Sylvian fissure (fissura cerebri
lateralis), the sulcus of Rolando (sulcus centralis), and the parieto-
occipital sulcus. The lobes formed by these sulci are the frontal,
temporal, parietal, occipital, and central (or island of Reil). The
convolutions of each lobe are shown with their names in the three
diagrammatic figures.
532
PHYSIOLOGY
CHAP.
Like the rest of the brain, the cerebral hemispheres consist of
white and grey matter. The former occupies the internal part,
where it forms the so-called medullary centre ; the second forms
the superficial layer, known as the grey cerebral cortex.
The white matter of the cerebral hemisphere consists of
medullated fibres, which are generally smaller than those of
the cord. They may be grouped into three principal systems
according to their course :—
(a) Commissural or transverse fibres, which unite the two
hemispheres ;
(&) Projection fibres, that run from the brain -stem to the
hemispheres, or vice versa ;
Fio. 265.— Median longitudinal section through adult brain. The posterior parts of the thalamus,
cerebral peduncles, etc., have been removed, so as to expose the inner surface of the temporal
lobe.
(c) Association or arcuate fibres, that unite neighbouring or
remote parts of the cortex of the same hemisphere.
The cerebral cortex varies between 2 and 4 mm. in thickness,
according to the region and to age. On examination with the
naked eye in a vertical section, it is seen, not to be uniform, but
to consist of a series of parallel layers, alternately white and grey,
the number of which varies in different regions (Baillarger, 1840)
(Fig. 267). This variation in the colour shows that the structure
of the cortex is not uniform, as is also confirmed by microscopical
examination.
II. The form and arrangement of the nerve-cells vary with
the varying depth of a convolution ; there are different more or
less well-defined layers, which are not always distinct, and do not
X
THE FOEE-BEAIN
always correspond with those visible to the naked eye. Usually
tin-re may be distinguished (Meynert and Eamoii y Cajal) :
(a) a superficial molecular layer ; (&) one or two layers of large
and small pyramidal cells ; (c) one or two layers of polymorphic
and spindle-shaped cells. A marked difference is to be seen in
the various regions of the cortex in the form and size of the
FIG. 266.— Gyri at the base of the brain. Diagrammatic. The chiasma is turned backwards.
nerve-cells, and in the depth and delimitation of the different layers.
In the central convolutions, adjacent to the sulcus of Rolando,
some of the deeper pyramidal cells assume comparatively gigantic
proportions, as first noted by Betz and Bevan Lewis, but this is
not observed in the cortex of the occipital, temporal, or frontal
lobes, in which the place of the giant cells is largely occupied
by the smaller pyramidal cells and by small angular cells.
To Brodmaun belongs the credit of having recently (1909)
534
PHYSIOLOGY
CHAP.
drawn attention to the structural characters of the cerehral
cortex, by study of the arrangement and morphological characters
of the cells which constitute its various layers. By long and
patient comparison of the different areas of the pallium he has
arrived at results which are of great interest, and which can be
summarised as follows :—
According to Brodmann, the fundamental type of the cerehral
cortex, from which all the other secondary types are differentiated
during foetal development (from the seventh month), consists of
six layers which may be clearly recognised, and are formed by
three strata rich in cells alternating with three layers poorer in
cells (Fig. 268). The first and sixth of these strata are constant
in all cortical regions of the adult human brain and all mammals.
Others, on the contrary, as the second and fourth granular layers,
vary greatly and may disappear in many regions of the adult
human 1 train; the remaining
layers, the third and fifth,
present an intermediate grade
of variability.
This structural six -layer
type is not permanent; 'in
many regions it is more or
less transitory. The numerous
secondary structural types that
i. ZU( . oruuiUiia Ul lid CUlrtl (JUll V vjiuunJiio. -. -. , _
(Baillarger.) Approximately natural ^ size. ^ 1, develop IrOlll it lOrill almost
nine-tenths of the entire cortex
of the adult human brain.
These secondary types may
in their turn be grouped into two great categories :—
(a) Homotypical cortical formations, in which the structure is
fundamentally unchanged, the six layers persisting (Fig. 269).
The greater part (about three-quarters) of the cortex of the human
brain comes under this category. The numerous types which it
comprises are distinguished from each other by the varying
characters of the several cell layers. These characters are par-
ticularly the depth or thickness of the cortex, the size of the cells,
and, above all, the numerical richness of the cells which make up
the different layers.
(&) Heterotypical cortical formations, which lose their funda-
mental structure during ontogeuetic development, either because
the layers increase in number, as in the case of the cortex of the
calcarine fissure (Fig. 270), or because some of the original six
layers disappear (Fig. 271).
We said that some nine-tenths of the whole cortex of the
adult human brain belong structurally to the fundamental type of
the six cellular layers, either because they retain it throughout life,
or because they exhibit it in some stage of development. The
Fio. 267. — Sections of cerebral convolutions.
show the six layers usually seen in the cortex
with the naked eye ; 2, appearance of a section
of a convolution from the neighbourhood of the
calcarine fissure.
x THE FORE-BRAIN 535
remaining tenth port, which never even during embryonic develop-
ment presents a six-layer structure, includes the cortex of the
olfactory Imlh, hippocampus, dentate fascia, etc. These portions
were termed het&rogenetic cortical areas hy Brodniann in contra-
distinction to the former, which he termed homogenetic cortical
areas.
The various cortical regions differ from one another both in
the characters of the cell layers and in the characters of the
. '
Fir,. 268. — Transverse section of cortex of calearine lissun- from a human foetus of eight months.
Cortical region in which the fundamental cytotectonic primitive type of six layers (to right)
is directly continuous at the point indicated by arrows with the eight-layered cytotectonic
type proper to the grey matter of the area striata of the calearine fissure. (Brodmann.) The
respective layers are: I, lamina zonalis ; II, lamina granularis externa ; III, lamina pyramid-
alis ; IV, lamina granularis interna ; IVa, sublamina granularis int. superficialis ; IVb, sub-
lamina granularis intermedia (Stria Gennari s. Vicq d'Azyri); TVc, sublamina granularis int.
profunda ; V, lamina ganglionaris ; VI, lamina multiformis ; Via, sublamina triangularis ;
VI'j, sublamina fusiformis.
nerve -fibres they contain, and in studying the latter different
structural types can also be distinguished ; Brodmann has studied
the mydo-architecturc of the cerebral cortex as well as its cyto-
architccturc. To enter into details would exceed the limits of
our subject, and we can only refer the student to Fig. 272, which
shows diagrammatically the combined results of the study of the
cells by Golgi's and Nissl's methods, and of the nerve-fibres by
Weigert's method (0. Vogt).
On the basis of the. results obtained from studying the cyto-
536
PHYSIOLOGY
CHAP. X
architecture of the different parts of the cerebral cortex, Brodmann
plotted out the entire cortical surface into fifty -two areas (Fig.
273 a, b) which he grouped into eleven regions or principal fields ;
the postcentral, precentral, frontal, insular, parietal, temporal,
occipital, cingular, retrosplenial, hippocampal, olfactory. In this
way he obtained a surface localisation, a sort of geographical chart,
of the cerebral cortex. The definition of the different areas is
Ilia
Hlb
>1I1
• :.
•••.."''-••• • ....'. • '. • •''• ,• .' '•• . •
FIG. 269. — Cy totectonio type of cortex of occipital lobe of adult man, in which the fundamental
type of six layers persists. (Brodmann.) Magnification 60 diameters.
possible owing to the fact that the structural peculiarities char-
acteristic of each area are sharply limited (Fig. 268), so that it
is tolerably easy in serial sections to recognise and fix the limits
which mark off each area from the adjacent regions.
The special importance of Brodmann's regional subdivision for
the physiologist and neurologist is, as he clearly brings out, that
while the greater number of the fields thus defined have as far
as is known no connection with actual physiological functions,
some of the areas, and precisely those which are characterised by
I
'i / ;•
•X 4
•
1 .;.
it .>. - .•
»vv.
>» ' ;
IV '*• *••' ""
• A* "°- «'.
-»:
«
4
ill
£:
r \ •
»• ' i
fi. -- i
* i * % •
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i"
ti
<
I1
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IVb-
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FIG. 270. — Cytotectonic type of area striata
of calcaiiii"' tissure of adult man. (Brod-
mann.) Magnified (i6 diameters.
FIG. 271. — Gifranto-pyrainidal eytotectonic ty]»'
zone of adult man. The t,wo more superlicial layers
are not reproduced. (Brodmann.) Figs. 270, 271,
272 have all the same magnification of 66 diameters,
and show the different sizes of the cells and layers in
the different regions of the cortex.
538 PHYSIOLOGY CHAP.
conspicuously differentiated structure (heterotypical formations),
coincide with, or are directly related to, the regions whose functions
are known from experimental physiological research or clinical
observations. These areas are especially : the giganto-pyramidal
area (field 4 of Broclmann) characterised by the presence of giant
pyramidal cells (Fig. 272), which occupies the precentral region
and coincides — as we shall see later — with the excitable or motor
area ; and the striated area of the calcarine fissure (field 17) in the
occipital region (Fig. 270), characterised by increase of the cellular
layers and the presence of large numbers of small cells, which
includes the visual zone.
III. The effects of complete destruction of the telencephalon in
different classes of vertebrates, as discussed in the last chapter,
showed that the view of those authors who maintain that all the
functions and acts of conscious psychical life are localised ex-
clusively in this chief segment of the brain has not been confirmed,
nor can it be confirmed by the physiological methods at our dis-
posal. There is, however, no doubt that the fore-brain is the seat
of all the higher mental activities, particularly the formation of
images, their association and calling-up in memory, and their
expression in complex voluntary acts — in a word, the highest
phenomena of the intellect.
A critical review of the theories that have prevailed as to the
material mechanism and seat of psychical phenomena was published
by Soury (1899), from a wide point of view, and with great wealth
of detail. To use the author's happy expression, it comprises the
natural history of the human mind, and could not therefore
possibly be summarised in the limits of the present volume.
Enough to say that from Alcmeon of Croton (500 B.C.), who seems
to have been the first who looked on the brain as the central organ
of the soul, to Franz Joseph Gall (1810-18), who first conceived
the brain as a collection of organs corresponding to different
mental faculties, innumerable hypotheses have been formulated to
account for the intimate relations between physiological function
and psychical activity — i.e. between body and soul. Of these
hypotheses, both in classical and in modern times, that which
regards the brain, or a part of it, as the material substrate
necessary to the activity of the mind, has certainly predominated.
This theory, however, only reached its complete expression with
Gall.
Haller (1708-77) regarded the white matter of the brain, not
the grey cortex, which he thought insensitive to stimuli, as the
seat of sensation and the source of movement. He did not allow
that different psychical functions could be assigned to particular
provinces of the brain, because the nerves of the sense organs are
connected with different points of the brain, and have no special
seat in the sensorium commune, that is in the white brain matter.
X
THE FOEE-BEAIN
539
Frochaska (1749-1820) made notable progress in defining the
seat of mental phenomena. He held the brain in general to he
iV 'v ^
, • » ' k * • :.
>*•>• r.v w ^:
.. -. . • I . . • «
.' )• ,'• :•< iJ '-j •"
'
/.'I' M* '•
Fio. 27'2. — Diagram to show tlu- layers of cells'andjfibres in tlie grey matter of the human cerebra
cortex, according to three histological methods : (a) Golgi ; ('-/) Nissl ; (r) Weigert. (O. Vogt.)
the organ of thought, but believed it not improbable that the
different acts of intelligence have distinct organs in the brain.
540
PHYSIOLOGY
CHAP.
Prochaska accounts for the dreams of sleep on the supposition that
the organ of perception, which is dulled in sleep, is distinct and
perhaps remote from the organ of ideation.
Bichat (1771-1802), on the contrary, returned partially to the
older view. Every kind of sensation has its centre in the brain,
but the brain, is never affected by the passions ; the organs of
organic life and the sympathetic ganglia are the exclusive seat of
the latter. Lesions of the liver, stomach, spleen, intestines, heart,
FIG. 273 «. —External surface of brain. Representation of cortical areas according to the cyto-
architecture of the grey matter in man. (Brodmann.) In this and the next figure the
different areas are marked by numbers and various other signs. Such are area 4, distinguished
by large black dots, which is the giganto-pyramidal area (motor zone) ; and area 17, marked by
small black points, the area striata (visual zone).
etc., produce a variety of affections which cease when the cause is
removed. Fear, for instance, arises from the stomach, choler from
the liver, goodness from the heart, joy from the intestines.
Yet more astonishing is the theory put forward by the great
anatomist Sommering in 1796, which is to some extent a return
to the ideas of Herophilus and Galen, who localised the seat of the
pneuma psychikon in the cerebral ventricles. During his anatomical
studies on the real origin of the cranial nerves, he was struck by
the 1'act that nearly all terminated in the walls of the cerebral
X
THE FOKE-BRAIN
541
ventricles, where they are Lathed by the serous fluid of these
cavities. This led him to conclude that this fluid (aqua ventri-
culorum cerebri} is the single medium of nervous activity, the
sensorium commune, the organ and seat of the soul.
Sommering dedicated his treatise, Ueber das Organ der Seele,
to Kant in order to obtain that great philosopher's opinion upon
his hypothesis. Kant's reply is worthy of him, and is of peculiar
interest in view of his bent to scepticism. He a priori rejects the
idea that the soul, which can only lie limited by time, can be
FIG. 273 6. — Internal surface of brain. Cortical areas according to cyto-architecture of grey matter
in man. (Brodmann.)
spatially localised. From the physiological point of view only the
site of the sensorium commune can be considered, that is, the organ
which makes possible "the association of all sensory representa-
tions in the mind." This sensorium commune is not the seat of
the soul, but it is the immediate organ of the soul, on the one
hand isolating the nerves which terminate there so as to keep the
sensations distinct, on the other establishing a perfect community
between them. Can this seusorium be represented by the water
of the cerebral ventricles, as assumed by Sommering ? The great
difficulty in admitting this hypothesis is — according to Kant—
that the water, being a fluid, cannot be organised, and without
organisation no matter can serve as the immediate organ of the
542 PHYSIOLOGY CHAP.
soul. In conclusion therefore (and this is the pith of Kant's
metaphysical comment on Sommering's hypothesis) it is not
impossible for the physiologist to make the collective unity of all
the sense perceptions in a common organ intelligible, though he
who attempts to solve the problem of the seat of the soul is
handling the impossible, and may be confronted with the words of
Terence, " Incerta haec si tu postules ratione certa facere, nihilo
plus agas, quam si des operam ut cum ratione insanias."
These remarks are necessary to the correct appreciation of the
physiological value of the work of Gall and his pupil and collab-
orator Spurzheim, the founders of the theory of cerebral localisa-
tion. They were the first who brought out the importance of the
grey matter of the cerebral cortex in general, and of the ganglia of
the nervous system, which they considered to be the origin of the
nerves and the organ of nutrition of the white matter. The
nervous system as a whole results from the association of several
separate systems, each of which has a different function. All
these systems, however, are united by means of commissures.
There is accordingly no common centre for all sensations, all
thoughts, all volitional impulses. Unity results from the harmony
of the individual functions brought about by the commissures.
Again the cerebral hemispheres are divisible into as many
pairs of particular organs as the distinct functions which they sub-
serve. Intellectual phenomena depend exclusively upon the cere-
brum, and its convolutions are " the organs of the mind." Gall
excludes the sense organs from any direct participation in the
phenomena of the intellect. They do not develop in proportion
with intelligence, in fact the larger number of them even stand
in inverse ratio with it. Taste and smell are more developed in
lower mammals than in man ; vision and hearing are more acute
in birds than in mammals. The cerebrum alone develops in direct
proportion with intelligence. The loss of one or more senses does
not diminish intelligence, which may persist even after the loss of
all the senses.
Gall, however, did not confine himself to the consideration of
the cerebrum as the substrate of mental phenomena ; he conceived
a psychological system, in which the intellect or psychical person-
ality of man is divided into a sum of arbitrary heterogeneous
faculties, each independent of the other, and each represented in a
special province of the cerebral cortex.
Gall's so-called phrenology started with the observation made
in his schoolboy days, when he noticed that some of his fellow-
students who had a remarkable memory for words had prominent
eyes ; this led him to conclude that the faculty of verbal memory
was localised in that part of the frontal lobe which lay above and
behind the orbital cavity.
If the capacity for learning easily by heart is associated with
x THE FOEE-BKAIN 543
such an external peculiarity, why should not other mental faculties
when they are markedly developed be associated with special
humps or prominences on the surface of the skull ? This generalisa-
tion gave rise to the subsequent researches, based on more or less
fantastic or subjective ideas, from which Gall and Spurzheim con-
structed the new science of phrenology. Its aims were study of
the most prominent mental faculties and predominating moral
characteristics of different individuals ; crauioscopic observation
of the form and varying development of the several regions of the
cerebral cortex ; and direct examination of the brain after death—
in the hope of determining the seat of the different faculties.
Although Gall was a good observer, as shown by his valuable
contributions to the anatomy of the brain, and although the
fundamental facts from which he started were correct, he lost all
critical sense in his eager attempt to solve his phrenological
problems, and accepted wholly illusory appearances for reality.
This did not prevent his theory, with Spurzheim's modifications
and additions, from obtaining a great following.
When Floureus published his researches on the physiology of
the brain (1822), he conferred a great benefit on science by rooting
out the intruding phrenological system.
He admitted with Gall that the cerebrum alone was of direct
importance to intelligence ; but absolutely rejected the, idea that
different regions of the cerebral cortex could be relative to different
intellectual functions. He found it possible to extirpate very
extensive portions of the cerebral hemispheres without producing
loss of their functions, and saw that a very small portion of the
brain sufficed for the exercise of its functions. But as larger
portions were removed all the functions became gradually weaker,
and were entirely lost when the destruction exceeded a certain
limit. Consequently the cerebral lobes must be concerned as a
whole in the exercise of their functions.
When one perception is lost, he says, all the rest go too ; if one
faculty disappears, all the others vanish. There is therefore no
definite seat for the different perceptions. The capacity for
perceiving, judging, or willing anything is located at the same
place as that of perceiving, judging, willing some other thing, and
this faculty is therefore one, and is essentially located in a single
organ.
This rejection of central localisation seemed to be the last word
on the relations of the brain to the mind. But, as the last chapter
si towed, later researches into the effects of cerebral ablation in the
different classes of vertebrates proved that this theory, on which
all psychical functions are exclusively localised in the cerebral
hemispheres — which is still maintained by Muiik and to a certain
extent by Loeb, — does not agree with the facts, and is definitely
contradicted by the behaviour of the lower vertebrates after the
544 PHYSIOLOGY CHAP.
removal of the fore-brain. The only part of Gall's theory which
Floureus accepted unreservedly is that which modern research has
proved untenable. On the other hand, the great merit of Floureus
as the pioneer in cerebral physiology is indisputable. But he went
too far in his work of destruction ; it is one thing to show that
Gall's localisations are unfounded, and another to deny absolutely
all localisation of the intellectual functions in the brain.
The most recent researches show plainly that there is a nucleus
of truth in phrenology. All portions of the cerebral hemispheres
have not the same functions ; distinct areas of the cerebral cortex
are concerned in different sense perceptions, in different ideas and
memories, and in the various voluntary impulses. But the new
theory of cerebral localisation is quite different from that proposed
by Gall, and has been gradually developed upon a scientific and
experimental basis.
G. K. Bouillaud (1825), a follower of Gall, published a memoir
called " Clinical researches to demonstrate that loss of speech
corresponds with lesions of the anterior lobules of the brain, and
to confirm Gall's opinion on the seat of the organ of articulate
language." In this memoir, which is of great historical importance,
he describes the symptoms of aphasia as observed by himself in a
series of cases, in some of which he was able to make a post-
mortem examination, and to show that in all the lesion involved
the orbital part of the frontal lobe. He drew the following general
conclusion from his clinical and anatomo-pathological observa-
tions : The human brain has an important function in the
mechanism of a great number of movements ; it regulates such as
are under the control of the intelligence and the will. There are
many special organs in the brain, each of which governs special
movements. The organs for the movements of speech are directed
by a distinct and independent brain centre, which lies in the
anterior lobes. Loss of speech is due either to loss of memory for
words, or to loss of the muscular movements from which speech
results. Loss of speech does not imply loss of the movements of
the tongue as an organ of mastication and deglutition of food, nor
loss of taste — which suggests that the tongue has three distinct con-
nections in the brain. Many nerves have their origin in the brain ;
those which innervate the muscles that co-operate in the produc-
tion of speech originate in, or at least necessarily communicate
with, the anterior lobes.
A little later (1836) M. Dax, who was probably unaware of
Bouillaud's important memoir, communicated a series of clinical
cases which demonstrated that disorders of spoken language are
constantly associated with a lesion of the left cerebral hemisphere.
A new memoir pointing out the same constant coincidence was
presented to the Academic de Paris (1863) by Dax fils, when it
was badly received by Lelut, but defended by Bouillaud.
x THE FORE-BRAIN 545
Bouillaud observed that a certain number of acts, c.y. writing,
drawing, painting, fencing, were carried out with the right hand.
They are. associated and co-ordinated movements which imply
activity of a particular cerebral organ, a given centre for sensation,
motion, and special memory, which is undoubtedly seated in the
left hemisphere. Why, he asked, should. we not be left-brained for
the movements of articulation also ?
This acute conjecture was confirmed by Paul Broca, who
showed more definitely than Gall, Spurzheim, Bouillaud, and Dax
that the true site of the special organ of verbal articulation lies in
the left hemisphere of the human brain.
In 1861 Broca presented a first memoir to the Anthropological
Society of Paris, in which he stated, on the basis of certain of his
clinical cases, that lesions of the lower segment of the third frontal
convolution of the left hemisphere (the so-called pars opercularis or
Broca's convolution) involved loss of the faculty of speech — aphemia
or aphasia. This he showed to be the seat of the cerebral organ of
verbal articulation, or more precisely of the memory of a certain
kind of co-ordinated movements necessary for the articulation of
speech. In fact, in cases of lesions of this convolution the memory
of words is not lost, nor are the nerves and muscles that come into
play in phonation and spoken language paralysed ; it is only the
memory of verbal articulation that is affected.
Broca was fully aware of the capital importance of his discovery
as the foundation-stone of a new theory of cerebral localisation in
opposition to the doctrine of Flourens. "We now know," he says,
"that all the parts of the 'brain properly so-called have not the
same functions, that all the convolutions represent, not a single
organ, but many organs or groups of organs, and that there are
large distinct regions of the brain which correspond to the large
regions of the mind." According to Broca, the new theory must be
built up upon normal anatomy and pathology, because a physio-
logical system that is not based on definite anatomical facts cannot
withstand criticism.
Another French anatomist and anthropologist, P. Gratiolet
(1861), had a yet clearer conception of the modern theory of
cerebral localisation, though his view was obscured by doubts and
contradictions, as appears from the following extract :—
:' It is legitimate to assume that there are as many distinct
regions in the cerebral hemispheres as there are different organs
of sensation at the periphery of the body. Thus we have the
brain of the eye, the ear, and so on; and in each of these brains it
would be easy to locate a memory and an imagination. But where
are we to locate general intelligence ? If there were several organs,
several brains, of what use would they be to one another? How,
for instance, could the brain of the ear assist the brain of the eye ?
The anatomical conditions of these associations and of this synergy
VOL. in 2 N
546 PHYSIOLOGY CHAP.
lie perhaps in the numerous commissures, which, since they unite
all the convolutions of a hemisphere in the most perfect manner,
determine the fundamental unity of the hrain. Is the intellect
seated simultaneously in the centrum ovale and the layers of the
cortex, or is it seated in the latter exclusively ? I doubt whether
in the physiology of the intellect it is possible to neglect the
centrum ovale with safety. Admitting, however, that the intellect
has the whole brain for its organ, it is not activated at all points
of the brain in the same way."
This statement of Gratiolet, as was opportunely pointed out by
Soury, contains almost the whole general modern theory of the
localisation of cerebral functions, which has developed in quite a
different direction from that of the older phrenology. The latter
pictured the brain as divided into so many independent organs,
intended for very complex functions. The new theory, on the
contrary, endeavours to determine the varying importance of the
different parts of the 'brain in so far as they receive centripetal
projection paths coming from the different sense-organs, centrifugal
projection paths along which the different voluntary impulses are
transmitted to the muscles, and commissural and association paths
which bring the separate fields of action into close connection.
The highest and most complex psychical functions are not localised
in these cortical fields, but are conditioned by the associative
elements, in so far as these co-operate in making the brain into a
\ single organ. The individual acts of the mind result from the
different combinations of the intellectual functions of the separate
cortical areas.
IV. From these introductory remarks, though brief and
incomplete, it will be readily seen that the theory of sensory
and motor cerebral localisation was already formulated in the
abstract, and only called for experimental evidence and better
definition, when Hitzig aud Fritsch (1870) published their first
memoir, " On the electrical excitability of the brain," which formed
the brilliant opening of a new chapter in cerebral physiology.
All the most experienced experimenters — Magendie, Longet,
Matteucci, Van Deen, Budge, Schiff — believed that the nerve-
centres of the cerebrospinal axis in general, and of the cerebral
hemispheres in particular, were — unlike the peripheral nerves—
iuexcitable to different kinds of stimuli applied directly either to
the grey or to the white matter. Fritsch and Hitzig were the
first who demonstrated the fallacy of this belief. They found, and
this was their chief discovery, that a portion of the convexity of
the cerebral hemispheres of the dog is motor, that is, it reacts
by muscular movements to the direct application of a galvanic
current, while the other portion is iuexcitable to this stimulus.
On exciting with weak currents the resulting contractions are
limited to certain groups of muscles on the opposite side of the
X
THE FOKE-BRAIN
547
body; with stronger currents the reaction spreads to more.
muscles, not only on the opposite, hut also ou the same side of the
hody. The mere displacement of the electrodes, or moving- them
away from each other, is enough to alter the form or extent of
the reaction. Lastly, if the electrodes are moved still further
from each other, or the current strengthened, epileptiform con-
vulsions set in which rapidly involve all the muscles.
Hitzig and Fritsch gave the name of centres to those areas of
the cerebral cortex which, when excited with a weak current,
induce reaction in a limited group of muscles on the opposite
side. The position of these centres
is approximately constant in the
dog, taking into account the
different conformation of the sulci
in different races. They are
grouped round the sulcus cruci-
atus, which limits the so-called
sigmoid convolutions in the dog,
and also extend to the anterior
part of the second external con-
volution, as shown in Fig. 274.
The excitable area of Fritsch
and Hitzig includes the centres for
the movements of the adductors,
flexors, and extensors of the limbs
on the opposite side, as well as the
centres which control the move-
ments of the face, head, and neck.
They evoked contractions of the
muscles of the back, tail, and
abdomen, on exciting points of
the brain surface lying between
those defined as centres, but were
unable to determine satisfactorily
any circumscribed point from which each of the above movements
could be separately excited. They stated that the whole of the
cerebral surface behind the centre for the facial muscles was
absolutely insensitive to the strongest electrical excitation.
The galvanic current is not, however, the most appropriate
stimulus for the purpose for which it was employed by Hitzig
and Fritsch. Every closure or opening of the current produces
an electrolytic change in the cerebral surface at the points of
contact of the electrodes, which rapidly depresses and abolishes
excitability. This is not the case if faradic currents are employed,
and these can moreover be readily varied so as to adapt them to
the varying excitability of the motor points of the cerebral cortex.
Ferrier (1873-1875), in determining the excitable points of the
FIG. 274.— Cortical motor centres of dog,
according to first experiments by Hitzig
and Fritsch. A, centre of neck muscles ;
+ , of extensor and adductor muscles of
anterior limb; +, of flexors and rotators
of anterior limb; {{, of muscles of posterior
limb ; Q, of muscles of the face. The two
hemispheres belong to two different kinds
of dogs.
548 PHYSIOLOGY CHAP.
cerebral cortex, used the currents from the secondary coil of Du
Bois-Keymond's sliding inductorium, coupled with a Daniell cell,
and succeeded in localising more centres, and in extending the
excitable zone, in the dog (Fig. 275). This was a marked advance,
not only as regards specialisation of the reactions, but also as to
their form. Terrier's observations, in fact, bring out clearly that
the motor reactions evoked on faradisation of the cerebral surface
have a marked character of purpose, that is, they are perfectly
analogous to the various movements co-ordinated to a given end
which the animal voluntarily performs under normal conditions
of life. These are not obtained with galvanic currents, which
induce sudden contractions of given groups of muscles at each
Fir;. 275. — Cortical motor centres of dog according to Ferrier. 1, opposite' hind-limb fuh;inn-<l ;
3, tail moved laterally ; 4, retraction and adduction of opposite hind-limb ; 5, protraction of
opposite fore-limb with elevation of shoulder; 7, closure of opposite eye, and movement of
eye-l>alls; 8, retraction and elevation of opposite angle of mouth; 9, opening of mouth and
movements of tongue; 10, retraction of angle of mouth owing to contraction of platysma ;
11, elevation of an^le of mouth and side of face, with closure of eye ; 12, opening of eyes witli
dilatation of pupils ami movements of eyes and head to opposite side ; 13, movement of eyes to
opposite side ; 14, pricking or sudden retraction of opposite ear; 15, torsion of nostril on same
side ; 10, elevation of upper lip and dilatation of nostrils.
opening and closure, which have not the perfect association and
succession characteristic of normal voluntary acts.
Working with Tamburini (1878) we brought some new facts
to light, in regard both to specialisation of the reactions from the
various excitable areas in the dog, and to their extent and
location in different individuals and in both hemispheres in one
animal. It is not accurate to say that the excitable areas which
Hitzig termed centres have an approximately constant position
in different dogs, and it is a mistake to assume with Ferrier that
they are symmetrical in the two hemispheres of the same animal.
Not only may the centres for the front limbs be grouped in two
distinct areas, capable of provoking two opposite reactions, but
a similar specialisation can more frequently be demonstrated also
in the region concerned with the movements of the hind-limb.
Lastly, not only does the excitability of the centres vary with the
THE FOEE-BEAIN
549
different experimental conditions to which the animal is exposed
(derive of narcosis, haemorrhage during the operation, hyperaemia
or isrliat'inia of the cortex), but the excitability of Hie different
centres of the same animal also varies, as well as the extent of
the areas which each occupies. This is shown diagram matically
in Fig. 276.
A new fact which we discovered in 18*78 is that the motor
centres for the limbs of the
dog are not limited to the
surface of the postcruciate part
of the sigmoid gyrus, but ex-
tend into the portion of the
cortex that dips into the sulcus,
which we found to be about
three times as extensive as the
excitable area on the surface.
When an induced current is
applied by suitably protected
electrodes, reactions of the
hind-limb on the opposite side
arc obtained when the elec-
trodes are placed on the most
internal and median part of
the introtiected cortex; and re-
actions < if the opposite fore- limb
(in exciting the outer part of
the cortex.
Later on (1883) we found
that the cortex within the
sulcus cruciatus of the dog is
excitable, not merely tO faradic FIG. 276.— Asymmetrical localisation of the motor
! . . i i i • centres in the postcruciate
stimulation, but also to mechani-
cal stimuli. To demonstrate this
it is necessary to divide the
arachnoid that unites the two
edges of the cruciate sulcus,
avoiding the vein that passes
through it, and to introduce a metal probe with sharp edges
carefully through the opening, and pass it along the sulcus so
as to scrape the introflected cortical surface. The usual com-
plex motor reactions of the muscles of the limbs on the opposite
side will be at once obtained; those of the posterior limbs on
scraping the inner and deeper part, and of the anterior limbs
on scraping the outer and superficial part of the introflected
cortex. The reactions do not differ from those obtained with
electrical stimulation, but they are usually less vigorous, and
after being once elicited, do not recur on repeating the stimulus,
postcruciate part of clod's
sigmoid gyrus. (Lnciani and Tainlmrini.) a,
abduction and flexion of posterior limb of
opposite side ; a', elevation and advance of same
limb; 6, abduction and elevation of oppn^iti'
fore-limb; V, flexion of forearm on arm with
movement of opposite shoulder ; b", retraction
and adduction of opposite fore-limb; c, move-
ments of head and neck.
550 PHYSIOLOGY CHAP.
since this partially destroys the nervous tissue and abolishes its
excitability.
The mechanical excitability of the cortex in the depths of the
cruciate sulcus is no accidental or exceptional fact ; it can invari-
ably be demonstrated in all dogs in which the electrical excitability
of the superficial cortical centres is well preserved.
All previous observers found the superficial cortex of the
sigmoid gyrus inexcitable to mechanical stimuli. In very
exceptional cases only Hitzig (1877) observed movements of one
limb during the removal of the corresponding centre. It is prob-
able that the normal mechanical excitability of the motor centres
of the cortex is easily exhausted, long before the electrical ex-
citability, by mere exposure of the surface to the air. The cortex
in the cruciate sulcus, on the contrary, keeps its excitability
longer.
The action of chemical stimuli on the cerebral cortex produces
different effects. Landois (1891) found that on sprinkling the
motor zone of the dog with various constituents of urine clonic
convulsions set in after a long latent period, which lasted a longer
or shorter time and were more or less generalised all over the
body. Maxwell (1906) observed that these symptoms of excitation
are due, not to stimulation of the ganglion cells of the cortex,
but to osmotic or chemical excitation of the nerve-fibres in the
subjacent white matter, which, as we know from other experiments
on nerve (see p. 219), react to these stimuli.
But in another series of experiments he found that certain
chemical substances, like creatine, act directly upon the elements
of the cortical grey matter. In fact, the application of creatine,
solid or strongly concentrated, to the cortex is followed after
rather a long latent period by clonic and tonic contractions,
while the injection of creatiue solutions into the depth of the
white matter, and steeping the motor nerve trunks in saturated
solution of the same substance, fails to evoke signs of reaction.
Baglioni and Magnini (1909) worked out the effects of different
chemical substances (acetic, citric, carbolic, glyceric acids, urea,
sodium chloride, sodium sulphate, strychnine, picrotoxiu, and
curare) when applied to the excitable zones of the cerebral cortex
of the dog. After exposing the motor zone and determining the
threshold of the faradic excitability of a given centre, they applied
the chemical substance, and employed the threshold of faradic
excitability to ascertain the stimulating or depressing action of
the chemical substance employed, independent of the direct motor
reactions which it produced.
From their results they were able to divide the chemical
substances which affect the centres in the motor zone into two
distinct groups.
(«) The first includes the acids employed, and glucose, urea,
X
THE FORE-BRAIN
551
chloride and sulphate of sodium. In very weak solutions these
have no effect on the faradic excitability of the cortex ; while in
stronger concentrations, or solid, they almost constantly lower the
excitability. In minimal doses they do not include spontaneous
spasms or clonic contractions; in comparatively strong doses, on
the contrary, they induce paralytic symptoms, which are evidently
due to the chemical destruction of the nerve elements.
(ft) The second group includes strychnine and picrotoxin. In
minimal doses these substances immediately raise the faradic
Fio. 277. — Surface of left hemisphere ot < '< rm- I'm. 278. — Upper surface of hemispheres of
fitli'i'iiK. (Kerrier.) I'fri'iijiillii.-ita. (Kerrier.)
1, Opposite hind-limb advanced as in walking; 2, movements of thigh, leg, and foot ; 3, move-
ments of tail; 4, retraction and adduction of opposite arm; 5, forward extension of opposite
arm and hand ; a, b, r, <1, single and combined movements of lingers and list ; (5, supination and
llexion of f ore -arm ; 7, contraction of zygomatic muscles with retraction and elevation of angle
of mouth ; 8, elevation of ala of nose and upper lip ; !>, 10, opening of mouth, advance of lips,
protrusion and retraction of tongue ; 11, retraction of opposite angle of mouth ; 12, wide opening
of eyes, dilatation of pupils, movement of eyes and head to opposite side ; 13, 13', movement of
ryes to opposite side, with upward or downward deviation and contraction of pupils ; 14,14',
pricking of opposite ear, with rotation of eyes and head to opposite side, wide dilatation of pupils.
excitability of the excitable areas, and after a very 1 rief latent
period of from a few seconds to 1-2 minutes produce the localised
movements similar to those observed on faradic excitation of the
centres, but the movements are repeated rhythmically, at the rate
of about 40-50 per minute, for a longer or shorter time (25-35
mins.) in the form of characteristic tic-like movements, whether
the animal is fixed to the apparatus, or suspended by the back, or
left free on the ground.
Probably curare should also be included in this class of
the chemical substances which are capable of directly exciting the
PHYSIOLOGY
CHAP.
ganglion cells of the cortex. Sergi (1902) observed phenomena
analogous to the above on applying curare to the cortex of the
guinea-pig; Baglioni and Magnini noted an increase of faradic
excitability, expressed by a drop in the threshold of excitability.
That the action of these specific poisons (strychnine, picro-
toxin, curare) is exerted electively on the cortical ganglion cells,
and does not spread to the nerve-fibres of the corona radiata,
is demonstrated by the fact that both the increase in faradic
excitability and the rhythmical contractions disappear immediately
FIG. 279.— Plan of li-l't hemisphere in Macacus brain. External surface. (Horsley and SchalVr.)
and for ever so soon as the poisoned area of the cortex is excised
or damaged by other poisons.
The fact that carbolic acid, which picks out the motor cells of
the ventral horn of the spinal cord, has no action nor depressing
effect on the cortex led Baglioni and Magnini to conclude that
the ganglion cells of the cortical motor zone are not of the same
nature as, and cannot be identified with, the motor cells of the
cord through which they indirectly exert their motor effect, and
should rather be compared with the cells of the dorsal horn of the
spinal cord in their property of reacting to strychnine.
Later work on the dog's brain added to the number of excit-
able centres. H. Krause (1884), on applying electrical stimuli to
an area lying somewhat external to and in front of Terrier's point
X
THE FORE-BRAIN
553
12, observed movements of deglutition and partial or total con-
strietion of the glottis and larynx associated with contract-ion of
the muscles of the neck, of the superior constrictors of the pharynx,
levatores veli-palatini, glosso-palatini, and tongue — in a word, the
muscles which come into play in deglutition and phonation.
The internal interhemi spherical surface of the brain, while less
known (perhaps because more difficult to explore), also contains
excitable areas, although these have not been localised and defined
with sufficient accuracy. Lo Monaco found that the fore-part of
MOVEMENTS OFFLEX|ON AT
TOES AND KNEE EXTENSION.
AT
FIG. 280.— Plan of left hemisphere—
Internal surface. (Horsley and
the marginal convolution contains the continuation of the sensory
motor /one of the external surface.
Ferrier first applied the method of faradisation to determining
the excitable area in the lower apes (Macacus cynomolgus). He
found that it extended over a larger surface than in the dog; in
addition to the two central or Rolandic convolutions it comprises
the angular gyrus, a portion of the upper tempero-sphenoid con-
volution, and part of the first and second frontal convolutions.
As shown by Figs. 277 and 278, a larger number of centres for
given movements of different muscular groups can lie identified in
this species of ape.
For descriptive purposes, Beevor and Horsley (1887-88)
divided the excitable zones of the cerebral cortex of Macacus into
554 PHYSIOLOGY CHAP.
fields or areas (Figs. 279 and 280) : (a) the area connected with
movements of the head and eyes ; (&) that connected with move-
ments of the face, including those of the mouth, cheeks, and
larynx ; (c) that related to the movements of the upper limhs ;
(d) that for movements of the lower limbs ; (e) that connected
with movements of the trunk and tail. These areas are not limited
by sulci or other structural features ; so they are not distinct, as
would appear from the diagram, but merge gradually one into
another. When the faradic stimulus is moderate and falls 1 letween
the limits of one of the areas, the reactions are confined to a single
region ; when the stimulus is strong and protracted the reactions
spread into the neighbouring regions ; when the stimulus falls at
the point of transition between two areas, muscular reactions can
be elicited from both regions by even a moderate excitation.
On stimulating different points of the five areas above enumer-
ated, Beevor and Horsley obtained a further specialisation of the
reactions shown on the two figures reproduced. These intra-
regional localisations are more definite and pronounced in propor-
tion as the areas are wider and the reactions more circumscribed.
This holds especially for the movements of the fore-limbs and the
face. The reactions usually permit of distinction into a relative
area and a small principal area or focal point, on stimulating
which the given movement results with greater promptness and
precision. The movement is rarely simple, e.cj. flexion or extension
of the thumb; more frequently complex movements result, simul-
taneously or in succession. The reactions obtained most constantly
and promptly may be termed primary movements in distinction
from the secondary which occur rarely.
The most salient characteristic of these reactions — as Ferrier
first pointed out — is their purposive co-ordination, as though they
were evoked by an act of volition. The impression made is that
the voluntary movements most frequently carried out by these
animals are those most readily obtained by electrical stimulation
of the cortex. Thus, on stimulating certain points of the area for
the arm, it is easy to elicit a series of prehensile movements ; 011
stimulating certain lower points of the area for the face, a series of
complex mastication movements is obtained, which are character-
istic of Macacus. When the reaction elicited by electrical stimula-
tion is not co-ordinated, it can often be shown that the surface of
the brain is in a condition of abnormal excitability, which causes
excitation to spread.
The results which Beevor and Horsley (1890) obtained by
faradising the cerebral cortex of an orang-outang, and those from
the wider experiments of Grlinbaum and Sherriugton (1901-3) on
anthropoid apes, are of great interest, since the configuration of the
anthropoid brain is closely allied to that of man.
Beevor and Horsley found that the complex excitable areas of
x THE FORE-BRAIN 555
the cortex of the orang do not overlap like those of the lower apes
(Macacus, Cerco^ithcrus), hut are separated here and there by
intermediate areas which are inexcitable even to strong currents.
The sum of the excitahle areas is relatively smaller in the orang
than in the lower apes. In tact the first frontal convolution and the
upper part of the postcentral convolution were inexcitable ; in the
fronto-parietal lohe the whole of the precentral convolution, an area
in front of the precentral sulcus, the lower two-thirds of the post-
central convolution, and the portion of the marginal gyrus which is
continuous with the superior end of the precentral were excitahle.
Griinbauni and Sherrington obtained somewhat different results
from their experiments on sixteen individuals of different species
— orangs (Opithaecus satyr us), gorillas (Troglodytes gorilla?), and
chimpanzees (Troglodytes nigcr and Troglodytes calvus). For
stimulating the cortex they preferred the method of unipolar
faradisation, hy which the excitable areas can be more precisely
differentiated.
They found in each of the animals examined that the motor
areas were present all along the precentral convolution (Fig. 281),
and continued into the cortex that dips into the central or
Rolandic sulcus, and the other secondary sulci by which this is
limited. Probably the excitable area buried in the sulci equals, if
it does not exceed, that which is uncovered. The anterior limit
of this area is not sharp, and retreats towards the central sulcus
when the excitability of the cortex is depressed. The posterior
limit, on the contrary, is sharper and more constant, and reaches
the floor of the central sulcus along its entire length, with the
exception of its upper and lower portions. In none of the animals
examined were there excitable areas in the postcentral convolution.
Sometimes, and only with strong faradisation, weak and indefinite
reactions were evoked, which are not comparable with those
obtained from the true motor area. Still it can be seen that the
motor effects of faradising the several points of the precentral
convolution with weak currents are facilitated by the simultaneous
faradisation of the points lying at the same level of the post-
central convolution. The student is advised to note this fact,
which may solve the contradiction between the results of Beevor
and Horsley and those of Grunbaum and Sherrington as regards
the excitability of the postcentral convolution.
The entire surface of the island of Reil is inexcitable even to
strong currents. On the mesial surface of the hemispheres the
excitable area is small in extent (Fig. 282). It does not reach the
sulcus calloso-marginalis. Certain points near this fissure may
evoke weak movements of the shoulder, trunk, hand, and finger ;
but, according to Grunbaum and Sherriugton, it is uncertain
whether these are of the same character as those evoked from the
true motor zone.
556
PHYSIOLOGY
CHAP.
In the cortex of the frontal lobe Griinbaum and Sherrington,
like Beevor and Horsley, found a large area completely separated
from the motor zone of the Eolandic area, faradisation of which
produces conjugate deviation of the eyes. The lower extremity of
the occipital lobe, and the region lying around the lips of the
calcarine fissure, are excitable to faradisation ; conjugate movements
of the eye! »alls may be also elicited from here. Griinbaum and
Anus
Abdomen
Chest
Fingers
c$ thumb \_
^e^ / CidLre
Nose of JAW.
Opening
ofj&w. Vocal
cords.
Salcus centralis.
FIG. 281.— External surface of brain of orang, showing excitable areas.
(Griinbaum and Sherrington.)
Sherrington, however, hesitate to include this region with the true
motor area represented by the Eolandic area.
The two figures 281 and 282 give approximately the localisation
of the areas for the face, fore-limbs, trunk, and hind-limbs, as well
as the differentiation of the excitable points contained in each
area. Among these are centres for the special movements of the
ears, nostrils, palate (acts of sucking or mastication), vocal cords,
muscles of thorax, abdomen, pelvis, and of anal and vaginal orifices.
The faradisation of certain points produces not motor but inhibitory
effects similar to those described by Sherrington.
These results of the experiments of Griinbaum and Sherrington
on anthropoid apes differ from those observed by Beevor and
THE FOBE-BEAIN
557
Horsley, since they found that the motor area, docs not, extend to
the postcentral convolution, hut is contincd to the. whole extent of
the precentral and the introflexed cortex of the Eola,ndie, sule.us,
and that the excitable areas of which it consists are not separated
from one another by intermediate inexcitahle spots, hut partially
overlap at the margins, forming a true continuous excitable /one,
like that observed on the lower apes.
It is remarkable that the topographical distribution of the
cortical centres for the musculature of the different regions of the
Sale. Central. A nu3, *
SuLc. caUcso
Sulc.precen Cr marg.
SuLc.parlfto
occip.
Sidc.calcarin
FIG. 282. — Internal or mesial snrfac.fi of brain of oraiiy, showiny excitable amis.
(Grunbanm and Sherrington.)
body lies within fairly exact limits along the precentral con-
volution, from below upward, in the segmental bulbo-spinal order
(Fig. 281).
In man, too, observations have been made with the object of
mapping out the topography of the excitable areas of the
cortex. The first attempts were made by the American surgeon
Bartholow and the Italian neurologist Sciamanna. Bnt the data,
obtained were scanty, since only very circumscribed areas of the
cortex, exposed by surgical operations, were excited. More
recently, owing to the progress of cerebral surgery, the Eolandic
region of the human brain has often been exposed in cases of
epilepsy, and excited by the same faradisation methods as are
employed in dogs and monkeys. The most important results
were obtained by Ferrier in four individuals (1890), by Horsley
558 PHYSIOLOGY CHAP.
and Beevor in six (1890), and by Bechterew in tbree adolescents
suffering from idiopathic epilepsy (1899).
The general conclusions arrived at by Becbterew, from the
results of his predecessors as well as of his own researches, are as
follows :—
(a) The general arrangement of the motor centres in man
coincides approximately with that observed in the lower apes
(Macacus, C'ercopithecus}. In fact, according to Bechterew, they
include both the central or Rolandic convolutions, besides the
adjacent regions of the frontal convolutions.
(&) The centres for the lower limits lie in the upper segment of
the postcentral convolution; the centres for the upper limbs lie in
the median segment of the two central convolutions ; immediately
below these are the centres for the thumb and fingers, and finally
the centres for the face lie in the lowest segment of the two central
convolutions.
(c1) The centres for the lateral movements of the head and eyes
correspond, as in the monkey, with the posterior segment of the
second frontal and probably extend to the adjacent regions
as well.
(d") The centres for the musculature of the back lie on the
surface of the precentral convolution, above the centres for the
upper limit, and probably extend, as in the monkey, to the adjacent
mesial surface of the hemisphere.
(e) In man, as in the monkey, there are special centres for the
thumb and fingers, which lie immediately below the motor centres
for the upper limbs.
(/) As in monkeys, the several cortical centres above
enumerated are separated in man by tracts of inexcitable cortex
(Bechterew).
This last observation merely echoes the results obtained by
Beevor and Horsley on the orang, which were contradicted by the
later and more numerous experiments of Griinbaum and Sherrington
on various species of anthropoid apes. The supposed isolation of
centres noted by these authors pro) >al >ly depends upon a depression
of the normal excitability of the cortex, due either to excessive
narcosis or to the prolonged exposure of the cerebral surface,
owing to which only the focal areas of the different centres remain
excitable, while the peripheral borders, by means of which these
centres are connected and partially overlap, have completely 1< »st
their excitability. Sherrington's observation that the anterior
limit of the excitable zone of the anthropoid apes is indefinite, and
becomes displaced backwards towards the central sulcus as the
cortical excitability is lowered, is in favour of this hypothesis.
In this class of research a positive result is invariably more
valuable than a negative result.
An important correction of Bechterew's conclusions is offered by
X
THE FORE-BRAIN
559
F. Krause's recent and numerous experiments on localisation of the
motor area in the human lirain by means of unipolar faradisation.
His results coincide perfectly with those of Sherrington for
anthropoid apes, in so far that they demonstrate the inexeitability
of the postcentral convolution, and limit the human motor
cortical area to the precentral gyrus. He further succeeded in
differentiating more fully the excitable points corresponding to
different movements of the upper limb and face (Fig. 283).
There can be no doubt — although there is no direct evidence—
that the excitable area of the human brain also extends to the
-r
Fio. 283. — Electrically excitable region of human cortex. (F. Krause.) The black dots on the
surface of the precentral convolution indicate the different motor centres ; /, sulcus centmlis
or fissure of Rolando ; n. extension and internal rotation of foot ; li, elevation and abduction of
arm ; c and rf, flexion of knee ; c, ulnar flexion ; /, palmar flexion ; ;/, radial flexion ; /(, dorsal
flexion of hand ; i, p, q, r, movements of thumb ; I, flexion ; in, extension of four fingers ; n,
extension ; o, flexion of index finger; s, extension of little finger; t, eyelid of opposite side ; »,
movements of buccal angle ; r, of zygomatic muscle and levator of upper lip ; .c, c if niassfl ITS ;
y, of external pterygoid muscle.
introfiexed cortex that dips into the lips of the Kolandic sulcus, as
has been well demonstrated in the anthropoid apes.
Some authors have contended that a stronger current is required
to elicit motor effects in man and in the anthropoid apes than in
the lower animals, and that in man it is more difficult, owing to
spread of the excitation to the subjacent centres, to arouse epilepti-
form convulsions by electrical stimulation of the cortex. Both
these statements were contradicted — by Griinbaum and Sherrington
for the anthropoid apes, and by Bechterew and Krause for man.
V. These experimental observations on the topography of the
excitable areas of the brain surface in the higher vertebrates
represent the development of the important discovery of Hitzig
560 PHYSIOLOGY CHAP.
and Fritsch. They afford a general experimental proof of the
functional specialisation of different regions of the cerehral cortex,
while telling us nothing definite about the function of the excitable
as compared with the non-excitable areas.
The objections raised against the value of the results obtained
by electrical stimulation of the cortex do not all stand criticism
and analysis. Carville and Duret, Onirnus, Dupuy, and others
showed experimentally that the electrical currents applied to the
cortex spread, more or less in proportion to their intensity, both
superficially and deeply beyond the area between the electrodes.
They concluded that the motor reactions aroused by electrical
excitation of the cortex are not sufficient proof either of its
excitability or of functional localisation, since they may be
interpreted as the effect of spread of current toward the basal
ganglia, pons, and bulb, where there are nerve elements that are
readily excitable.
But it must be remembered that :—
(a) The motor reactions confined to given groups of muscles
can also be obtained with mechanical stimulation, which does not
spread, but remains strictly localised to the regions directly
involved (Luciani).
(//) The effects of electrical excitation are quite definite. The
slightest shift in the position of the electrodes produces quite a
different reaction ; so soon as they are applied to the anterior
frontal or occipital regions all reaction ceases, even when the
strength of the stimulus is greatly increased (Hitzig, Ferrier).
(c) The convolutions of the island of Keil, though they lie
immediately above the corpus striatum, are absolutely inexcitable,
while the central or Rolandic convolutions, which are more remote
from the basal ganglia, yield with the same current very definite
reactions varying at different points of the gyri (Ferrier, Griinbaum,
and Sherrington).
(d) If the cortex of the postcruciate portion of the sigmoid
gyrus of the dog, which contains centres from which the muscles
of the limbs on the opposite side can be excited, lie cut with a
sharp knife, leaving the incised strip in position, the usual reactions
are no longer obtained on electrical stimulation, although electrical
conductivity has not been altered by the incision (Luciani and
Tamburini).
(e) If after destruction of the excitable centres for the dog's
limbs the subjacent white matter is excited, the usual reactions
are obtained ; but if at the end of a few days the brain is again
exposed, and the current applied to the bottom of the wound, no
reaction will lie obtained, although the physical conditions of
electrical diffusion are unchanged (Albertoni and Michieli).
(/) The cortical grey matter which yields motor reactions on
application of an electrical current is truly excitable ; it is not
X
THE FOEE-BEAIN
5G1
merely a physical conductor of the current to the white matter of
the centrum ovale, but its elements are physiologically excited,
and through them the excitation is transmitted to the nerve-fibres
(Frangois-Franek and Pitres).
This last fact can be demonstrated experimentally by comparing
the motor reactions evoked on exciting the cortex and those
obtained on exciting the subjacent white matter with the same
current.
After diligent research Frangois-Franek and Pitres (1878-79)
established the fact that, generally speaking, the white matter
is less excitable than the grey. If, after ascertaining the
minimal current capable of pro-
ducing a given movement by
stimulation of the cortex the grey
matter is excised, and the same
current applied to the white
matter lying immediately below A
it, the reaction is no longer
obtained. It is necessary to in-
crease the strength of the current
can
be
FIG. 284. — Lost time in muscular contraction
on exciting the cortical centre M, and the,
underlying white matter M'. (Frangois-
Franck and Pitres.) The middle line shows
the time in J-JTJ sec. The lower line marks
the application of the stimulus. In A the
lost time=Tijir sec. ; in B=-Tr>Tf sec.
before the movement
evoked again.
On the other hand, the excit-
ability of the cortex under the
action of certain toxic substances
is more easily lost than the ex-
citability of the white matter ;
this is seen after chloral narcosis.
While the dog lies in the chloral
narcosis, even the strongest
stimulation of the cortex fails
to elicit any muscular response,
while stimulation of the subjacent white matter is still effective,
even with comparatively weak currents. This fact, first observed by
Frangois-Franck and Pitres, and confirmed by Eichet, Bubnoff and
Heidenhain, and de Varigny, is of great theoretical importance.
It seems to show that the cortical substance rendered inexcitable
by chloral, may — while preserving its physical conductivity-
oppose an insurmountable barrier to the transmission of the
stimulus applied to its surface.
Another important fact brought out by Frangois-Franck and
Pitres is the delay in the muscular reaction, which is perceptibly
greater when the cortex is electrically stimulated than when the
electrical stimulus is applied to the centrum ovale. To avoid
experimental errors, or reduce them to a minimum, in demonstrat-
ing this fact it is necessary to operate on one and the same animal
by simultaneously exciting a region of the cortex and an adjacent
VOL. Ill 2 0
562
PHYSIOLOGY
CHAP.
portion of the centrum ovale in the same hemisphere, or better
in symmetrical regions of the two hemispheres. Fig. 284 is a
tracing showing the intervals between the moment at which the
current passes and the moment at which the reaction commences
on exciting the cortex and the centrum ovale. As- will be noted,
the difference is not insignificant; in this instance it amounts to
y-§^ sec., but in other cases it may attain y-g-^ sec. Bubnoff and
Heidenhain, who operated on dogs under morphia, even obtained a
difference of Vrnrtr 8ec-
Tins marked delay in response when the cortex is excited
shows that the cortical grey matter is not merely a passive inert
conductor to the subjacent white matter. It receives the stimulus,
FIG. 285. — Tracing <>t'a voluntary contraction of the opponens pollicis taken at a known vdncily
of the recording cylinder. (Schafer.) Shows the elementary vibrations that make up the
contraction.
elaborates it, and enters into the active physiological state known
as excitation, which Pfliiger proved to occur on the direct or reflex
excitation of the grey matter of the spinal cord.
To obtain a clear idea of the active state or physiological ex-
citation of the cortex, it is useful to compare the character of the
muscular contractions evoked by the voluntary impulse with those
produced by electrical excitation of the cortex.
On recording the voluntary contraction of any muscle (e.g. the
opponens muscle of the thumb), by some suitable myographic
method, the resulting curve shows undulations which are fairly
regular as to rhythm, though irregular in amplitude, with a
frequency of 10-12 per second (Fig. 285). Horsley and Schafer
showed this variation to be fairly constant in the same individual,
but variable in different subjects (from 8 to 13 contractions per
second), provided the resistance the muscle encounters in contract-
X
THE FOKK-l'.UAIN
563
ing is very slight. The subsequent work of Griffiths brought out
the fact that when this resistance increases there is a corresponding
increase in the frequency of contraction, up to 15-18 per second.
When the resistance is protracted and fatigue supervenes the
frequency diminishes. As shown by Fig. 286, an outstretched arm
holding a weight shows the same rhythm of contraction as a single
muscle.
We may thus say, with Schafer, that the average frequency of
the discharges which produce a voluntary contraction is from
10 per second, with a possible increase to 20 per second, when the
resistance opposed to the contraction is excessive. These facts
harmonise well with those given by Eichet for tremor, viz. 10-11
contractions per second. They also agree with the fact that it is
impossible to speak or sing more than eleven syllables or to play
more than eleven musical notes per second. The cortical cells
Fin. 2S(i.— Vibrations of outstretched arm holding ;i weight of about six kilos. (W. Griffiths.)
Tin1 spaces between the vertical lines represent intervals of one sec.
thrown into activity during these voluntary acts cannot discharge at
a greater rapidity than this. The most elementary psychical acts
of the cortical cells have therefore a mean duration of y^ sec. ;
but it is probable that practice and certain favourable conditions
may shorten this duration.
Let us pass on to examine the characters of the motor reactions
artificially obtained by electrical excitation of the excitable points
of the cerebral cortex, and see if they differ from those of voluntary
action.
Frangois-Franck and Pitres (1878-79) stated that stimulation
of the motor cortex, like that of the motor tracts of the cerebro-
spinal axis, gives rise to a series of contractions the rhythm
of which corresponds exactly to that of the stimulus adopted, just
as in the stimulation of a peripheral nerve. If the cortex of the
excitable zone is stimulated 5, 10, 20, 40 times per second, the
number of contractions which make up the muscular response will
be 5,10, 20, 40 per second ; above 40 per second the single contrac-
tions fuse to form a perfect tetanus. This last statement, which is
564
PHYSIOLOGY
CHAP.
too absolute, was subsequently modified by the authors themselves,
who found that the ascending line of a cortico-muscular tetanus is
invariably notched, the fusion of contractions not being always
complete if the stimuli are sent at a rate sufficient to produce
tetanus when applied to the muscle or its motor nerve.
The later work of Horsley and Schiifer (1886) led to more
exact results, which are to some extent directly contradictory of
the statements of Fran^ois-Franck and Pitres. In experimenting
FIG. 2S7. — Myographic curves from hamstring of monkey. (Horsley and Schnfer.) A, natural
contraction (voluntary); B, contraction caused by excitation of cortical leg centre by rapid
induced currents.
on monkeys, dogs, cats, and rabbits they found that when the
excitable zone of the cortex was stimulated with faradic currents of
a frequency of 10-12 per second the muscle reacted with rhythmical
contractions of the same rhythm as the current. But this
synchronism ceases when the frequency of stimulation exceeds
that limit ; the contraction curve no longer shows fusion of
the contractions, that is, complete tetanus, but it reproduces the
rhythmical oscillations of voluntary movements (Fig. 287).
From these results as a whole it seems reasonable to conclude
that the active state aroused in the cells of the cortex by direct
artificial stimulation is analogous to, if not identical with, the
x THE FOEE-BEAIN 565
active state into which it is thrown physiologically during
voluntary activity.
VI. Besides the motor reactions we must take into considera-
tion the inhibitory functions of the cortex, of which little is at
present known.
The discussion in the last chapter of the effects of cerebral
extirpation shows that the fore-brain possesses inhibitory functions.
Goltz' brainless dog, which moved constantly in its cage so long
as it was awake and not overcome by fatigue and sleep, reminds us
of the continuous movement characteristic of certain forms of
dementia. This abnormal and aimless work may be regarded as a
natural effect of the loss of the inhibitory powers of the brain. In
agreement with this is the fact observed by Goltz that a whole
series of special characteristic reflexes can be evoked in the brain-
less dog, which are not obtained with the same promptness, facility,
and constancy in the normal dog (in which the brain is capable of
inhibition). We have seen that the ablation of the cerebrum in
mammals at first produces a state of rigidity or tonic contraction
in certain muscular groups of the trunk and limbs which is an
exaggeration of the normal muscular tone, retiexly produced by
influences which reach the centres by the ordinary afferent paths
and are transmitted to the muscles by the motor paths. We saw
that after section of one side of the brain-stern the exaggeration of
t< >ne and rigidity is produced in one half of the body only, because
it is only in one half that the inhibitory influence of the higher
centres, which normally moderates the reflexes that determine the
tone of the muscles, is lost.
It is evident that the inhibitory influence of the brain may be
exercised 1 >y the will, as well as its excitatory function. We are
able at will not only to throw muscles into contraction, but also
to restrict or arrest their activity. We continuously exert a
regulating control over our reflex movements when we are awake ;
we are able to reinforce, moderate, or even arrest them. Does
this inhibition depend on the interruption of the activity of the
cortical motor centres, or on a positive activity which opposes the
impulses of these centres and suppresses their effects ? What is
the mechanism of this inhibition ? Are there in addition to the
motor centres and nerves other inhibitory cortical centres and
nerves? Or are the same motor mechanisms capable of two
opposite forms of excitation? These questions are entirely suit
j a dice, for it is possible to offer different solutions of them, with
experimental evidence in support of each. We must confine
ourselves here to recording the best-established facts.
Bubnoff and Heidenhain (1881), after they had determined the
motor area in the dog, recorded the contractions of the extensor
muscle of the toes on a revolving cylinder. Any strong excita-
tion of the foot throws this muscle into reflex contraction. If,
566 PHYSIOLOGY CHAP.
during contraction, the skin of the foot is gently stroked, or the
motor area tetanised with a small current, the muscle relaxes, and
the contraction disappears entirely or partly (Figs. 288, 289).
These tracings show that the state of activity of the motor centres
of the cortex which is elicited by strong stimulation may be
abolished by a subsequent peripheral or central stimulation of an
exceedingly mild character, which in the resting state of the
centres would lie incapal >le of producing any obvious effect.
Brown-Sequard (1884) on exciting the non-motor region of the
cortex of dogs and rabbits with strong currents was able to abolish
the excitability of the motor area for some minutes. He termed
the part of the cortex which does not react by movements to
FIG. 288.— Inhibitory effects of reflex excitations. (Bubnoff ;m<l Heidenliain.) a represents a
reflex contraction of the muscle, a /3, caused by rubbing the skin of the belly ; at y' there is a
rapid relaxation, •/ y, caused by tactile stimulation of the skin of the leg ; at S the contracture
2> &' is reinforced after lirm pressure of the leg; at e the muscle relaxes suddenly and
completely, e e', after gently stroking the skin of the leg.
stimulation, inhibitor}/ ; he denied its inexorability, and held it to
be capable of activity, and of transmitting excitation to other
centres, along the association fibres, so as to inhibit their functional
activity.
With a view to localising the inhibitory activity of the cortex,
Libertini (1895) endeavoured to determine the reflex time of the
muscles in the dog's limbs, before and after destroying certain seg-
ments of the brain. He found that a few days after the excision
of one or both pre-frontal lobes there was a marked shortening of
the reflex time of the muscles of the fore-limb. The same effect
is not obtained or only to a much less extent, after excising one or
both occipital lobes, and does not occur after excision of the
temporal lobe. The reflex time of the muscles of the hind-limb
undergoes no perceptible variation before and after the operation.
x THE FOBE-BKAIN 567
Fano determined the variations of the reflex time after
faradising the cortex. He observed that on exciting the pre-
froutal lobe for five seconds by an induction current (so strong as to
produce epileptoid convulsions when applied to the motor area),
there was invariably a depression of excitability in the cerebro-
spinal centres, lasting about three minutes. In fact during this
time if the skin of the fore-limb of the opposite side were excited
by a break current, so as to provoke a reflex contraction from the
subjacent muscles, there was a reduction in the height of the
myographic curve, and a striking lengthening of the reflex period,
that is the contrary effect to that observed by Libertini after
excision of the pre-frontal lobe.
FIG. 289. — Inhibitory effect of weak cortical stimulation. (Bubnoff and Heidenhain.) At « the
muscle contracts, a a', after the application of a strong galvanic current to the cortical centre ;
at b there is a stronger contraction, b V, after a second excitation with same current ; after
the slow relaxation, b' <.•', the muscle is suddenly elongated, c' c, by the action of a w.-ak
galvanic current on the same centre.
Simultaneously with Fano, this cerebrospinal inhibition was
demonstrated by Oddi by a different method. He applied to the
5th ventral lumbar root a pair of electrodes, connected with a
sliding induction coil and a metronome which served as an inter-
rupter, so that the nerve could he rhythmically excited. The
rhythmic contractions of the gastrocnemius muscle were recorded
on a rotating drum. After exposing the brain under a suitable
degree of narcosis, he stimulated the cortex of the pre-frontal lobes
of the side opposite to the excited spinal root with another induced
current, and noted profound changes of an inhibitory character on
the curves of the rhythmical contractions of the gastrocnemius
(Fig. 290). These inhibitory effects ensued after a fairly long
period of latent excitation, and continued for some time after the
application of the stimulus to the cortex had ceased. On
568
PHYSIOLOGY
CHAP.
faradising the pre-frontal cortex on the same side as the root
experimented on, a weaker inhibitory effect could also be observed
(Fig. 291). When, on the contrary, the occipital lobes of either
side were excited, even with very strong currents, no appreciable
alteration in the tracing could be detected.
These researches show that inhibitory effects from cortical
excitation can be transmitted not only to the muscles of the fore-,
but also to those of the hind-limbs.
Neither the experiments of Fano nor those of Oddi, however,
demonstrate that special inhibitory centres, antagonistic to the
motor centres, are contained in the cortex of the pre-frontal lobe.
The stimulus required to elicit inhibitory effects from this is always
stronger than that which elicits motor reaction when the excitable
1
RS iJ
UUlWIMIUUlJUWm
uuuuui
Flo. 2'JO. — Inhibitory effect of faradisinj; pre-frontal lobe upon contractions of gastrocriemius
muscle of opposite- side', excited by rhythmical stimulation of the fifth motor lumbar root.
(Oddi.) The middle line shows the be^innin^ ami end of the cortical excitation; the lower-
line indicates the rhythmical excitation of the spinal rout.
area is stimulated. The pre-frontal lobe contains no definite
and well-marked areas from which prompt and facile inhibitory
effects can be obtained. Oddi further observed that faradic
currents applied to the pre-frontal lobes after a marked inhibition
give rise to epileptic fits, probably because the stimulus is trans-
mitted to the motor area. All this tends to the conclusion (after
Bubnoff and Heidenhain, as above cited) that the centres contained
in the so-called motor area are capable of both motor and in-
hibitory reactions.
Sherrington (1893-95) and H. E. Bering and Sherrington (1897)
demonstrated that the faradisation of certain points of the cortex
lying in the motor area may, besides contraction, produce relaxa-
tion or depression of tone in the antagonist muscles. This effect is
obtained not on stimulating the same point of the cortex which
produces contraction, but on applying the stimulus to the area
which produces the contraction of the antagonists. There would
THE FOKE-BKAIN
569
therefore seem to be, at all events for this form of inhibition,
distinct paths for motor and for inhibitory impulses.
Among the most classical examples of this so-called reciprocal
innervation of the antagonist muscles, is that which Sherriugton
discovered for the muscles of the eye-ball. If in the cat or
monkey the oculo-rnotor and the trochlear nerves of the left side
are cut so that only one muscle, the external rectal, remains active
in the eye of this side, and the area in the frontal or the occipital
lobe which normally produces conjugate movements of both eyes
to the right (Fig. 281) is then faradised, there will lie a deviation
to the right not only of the normal right eye owing to the con-
traction of the right external rectus, but also of the paralysed
FIG. 291. — Weaker inhibitory effect after faradising the pie-frontal lobe on same side as the ga.stru-
cnemius that is making the tracing. (Oddi.) The three lines correspond to those of the previous
figure.
left eye owing to relaxation of the left external rectus. By a
similar experiment, after section of the sixth abducens nerve, an
inliibitory action on the right internal muscle of the operated
eye can be demonstrated, associated with contraction of the
internal rectus of the normal eye.
Another example of reciprocal innervation may be seen in the
extensor and flexor muscles of the extremities. In chloroform
and ether narcosis there is a stage during which a state of flexion
or tonic extension of the extremities can be observed. If in a
monkey in this state the cortical areas which determine the con-
traction of the flexors are faradised, relaxation of the extensors
can lie distinctly perceived if the muscles are felt with the hand.
If the cortical areas of the extensors are faradised, while the flexor
muscles are held in the hand, relaxation of these muscles can be
distinctly felt.
570 PHYSIOLOGY CHAP.
Similar effects to those obtained by the direct stimulation of
the cortex result both from stimulation of the nerve fibres of the
corona radiata, after removal of the grey matter, and from reflex
stimulation, due to excitation of sensory nerves on their end-
organs.
These and other similar facts have led some authors to the
conclusion that on stimulation of the cortex there is always, along
with contraction of certain muscles, relaxation of their antagonists,
and that under normal conditions there is never synchronous con-
traction of antagonistic muscles. The later observations of E. du
Bois-Eeymond (1902) show plainly that the relaxation of certain
muscles during the contraction of their antagonists is not a general
specific law ; that there is a whole series of facts which are opposed
to this so-called " law," and generally speaking that the inhibitory
effects are not confined to the antagonist muscles, but may also
extend to other muscles of any function. While admitting the
accuracy of the inhibitory phenomena described by Sherrington
and others, there is no necessity for undue generalisation.
VII. In addition to motor and inhibitory effects on the
voluntary muscles the stimulation of the excitable area of the
cortex produces effects, also motor or inhibitory, in the organs of
vegetative life.
It is a matter of common observation that emotional states of
different kinds are associated with respiratory, circulatory, and
secretory changes. Since the discovery of Hitzig and Fritsch,
a number of experimenters have tried to localise the centres
of these special reactions in the cortex by the usual method
of faradic stimulation, but these attempts have not led to any
such precise localisation as in the case of the voluntary move-
ments. Generally speaking, it may be stated that the electrical
excitation of any point of the so-called motor area may excite
respiratory, cardiac, or secretory effects. But there is no
specific localisation for these reactions, only a diffuse localisation
which extends all over the area which is known to be excitable.
Beyond this zone cortical stimulation is ineffective, when moderate
currents incapable of provoking convulsive attacks are used.
Electrical stimulation of the motor area in the dog produces
(Danilewsky, Bochefontaiue, Frangois-Franck, and Pitres) some-
times acceleration, sometimes retardation of the respiratory rhythm,
independently of the exact point of stimulation, and rather in
relation to the strength of the stimulus. Bechterew obtained
similar results, while others described special inspiratory and
expiratory effects on exciting fixed and definite points of the
motor zone.
The differences noted by the various experimenters probably
depend on the degree of anaesthesia of the animal, perhaps also
on the nature of the anaesthetic. Under chloral, Eichet observed
x THE FOEE-BEAIN 571
that OH exciting different points of the cortex there was respira-
tory arrest.
Faradisation of one point of the pre-frontal lobe, that is, of the
cortex lying in front of the motor area, also produces arrest of
respiration in the inspiratory phase, preceded by acceleration of
rhythm (H. Munk). At other points on the inferior surface of the
same lol >e it produces arrest of respiration in the expiratory phase,
also preceded by acceleration. These effects were obtained not
only on dogs but also on monkeys.
The subsequent work of W. G. Spencer showed that the
inspiratory effects obtained on exciting the cortex of the inferior
surface of the pre-frontal lobe are apparently connected with the
olfactory function.
Lastly, Langelaan and Beyermaim (1903) claimed to have
discovered on the dog an area lying at the extremity of the siguioid
gyms, where the coronary fissure meets the pre-Sylvian, the
electrical excitation of which with very weak faradic currents
produces respiratory acceleration, followed by inspiratory arrest.
On the basis of clinical observations they hold that a similar
centre also exists in man at the base of the second frontal convolu-
tion near the pre-central gyrus.
After the discovery of Hitzig and Fritsch, Schiff showed that
faradisation of the motor zone may produce cardiac and vascular
effects. Many subsequent observers have continued the study of
this subject. Danilewsky found that on exciting Hitzig's centre
for ocular movements in the curarised dog, blood pressure was
raised owing to vase-constriction and slowing of cardiac rhythm.
Bochefontaine, who also operated on curarised dogs, observed that
the circulatory effects were obtained from the whole motor area,
from a much more extensive surface than was assumed by
Danilewsky. These reactions consist in a marked increase of
arterial pressure with delay in cardiac rhythm. The pressor
effect is sometimes preceded by a depressor effect, the former is
probably due to the predominance of vascular spasm, the latter to
predominance of cardiac inhibition.
Eichet found that faradisation of the anterior part of the
sigmoid gyrus in particular produced circulatory effects ; a short
stimulation sufficed to produce a marked rise of arterial pressure,
after a long latent period ; the pressor effect persists for a very
long period ; and finally the excitability of the cortex disappears
after quite moderate stimulation, every reaction ceasing, even to
maximal currents.
Franeois-Franck and Pitres made a minute analysis of the
circulatory reactions to cerebral faradisation. In order to separate
the effects on the vessels from those on the heart, they atropinised
the animal or cut the vagi. They saw that ill operated dogs
cortical excitation produced a marked, gradual rise of arterial
572
PHYSIOLOGY
CHAP.
pressure, followed by a regular drop to the normal, and even below
it. The pressure curve is comparable with that obtained under
identical conditions of suppression of moderating influences, on
direct or reflex excitation of the bulbo-spinal centres. Only very
rarely does cortical excitation produce a depressor effect due to
vascular dilatation ; it is probable that the brain may produce
active dilatation of limited vascular regions, and does not sensibly
affect the general arterial pressure.
These vascular changes due to cortical excitation are not
Fir;. 292.— Opposite effect upon volume of kidney (rul.ll.) and arterial pressure (P.C.) of cortical
excitation (.shown on lower line). (Francois-Franok and Pitres.) Arterial pressure rises from
130 to 260 mm. Hg., while the volume of the kidney diminishes. As the animal was atropinised,
the excitation does not affect cardiac rhythm, and the pressor effect in this case evidently
depends on the contraction of the vessels, both superficial and deep or visceral.
elicited from the whole of the brain surface ; unless very strong
currents capable of producing epileptic attacks are used, fara-
disation of the anterior frontal, inferior lateral, and posterior
occipital regions are ineffective. Vaso-motor effects are constant
on stimulating the motor area ; whatever point of this region
is excited the vasomotor reaction is general and bilateral ; it is
not more pronounced in the limb that corresponds with the centre
excited, nor in the superficial than in the deep vessels (Fig. 292).
It is probable that vascular response can be produced from the
excitable area of the cortex in proportion as this contains afferent
paths to the vasomotor centres of the bulb ; the vascular reactions
x THE FORE-BRAIN 57:5
due to stimulation of the cortex are similar to those excited rcflexly
from the cutaneous or mucous sensory surfaces.
The effects on the heart of cortical stimulation are very variable,
according to Francois - Franck and Pitres ; acceleration and
retardation of rhythm appear irregularly in the course of a single
experiment, independently of the seat of stimulation. This con-
stantly occurs on applying currents capahle of provoking epileptic
fits in animals that are in light narcosis. During the tonic phase
of the epileptic attack there is thus a more or less marked slowing
of cardiac rhythm (from 150 to 110 beats per minute), while during
the clonic stage the rhythm is accelerated (e.g. rises from 125 to
250 beats per minute). In curarised animals too, in which the
Fir,. 293.— Voluntary acceleration of cardiac rhythm with no change in the respiration. Observa-
tion made i >n a young man by Patrizi. The arrow indicates the commencement of the
voluntary effort to accelerate the beat of the heart. The upper line is the tracing of thoracic
respiration by Marey's /i»c»i/n»/nij</i ; the lower, the pulse tracing from the left hand, taken
with Luciani's ralHnn-trif ijlin'e.
convulsions of the voluntary muscles are eliminated, the same
cardiac reactions can be seen on strong cortical excitation.
Changes of cardiac rhythm can also be observed on moderate
cortical excitation of brief duration, which is incapable of producing
epileptic seizures. In these cases the effect consists in regular
acceleration or retardation of rhythm. The form of the reaction
is independent of the site of the stimulation in the motor area,
and seems to depend more upon the intensity of the stimulus :
inhibition is usually due to sudden, strong excitation, acceleration
to rnild and prolonged stimuli.
In respect of these cardiac reactions the excitable surface of
the brain may again lie compared to a sensitive surface, and there
is no reason for assuming that the motor area contains special
moderator and accelerator centres for the heart.
574 PHYSIOLOGY CHAP.
The afferent paths from the cortex to the cardio-motor bulbo-
spinal centres by which changes in the frequency and intensity of
the cardiac rhythm are produced, are normally excited reflexly by
emotions, by excessive work, by the tension of the muscles, and by
variation in respiration. But there may exceptionally lie percept-
ible acceleration or diminution of the cardiac rhythm associated
with a simple, direct voluntary impulse, without obvious change in
the respiratory rhythm (Tarchanoff, Patrizi) (Fig. 293).
From the effect of the emotions on the secretions and specially
on salivation and perspiration, on the muscle cells innervated by
the sympathetic, on the skin, the alimentary tract, and the
urinary system, it is highly probable that artificial stimulation
of the cortex also produces similar effects. In fact, Bochefontaine
first, and after him many other observers, found that faradisation
of the motor area in the dog produced a now of saliva from the
salivary glands of both sides. Changes in sweat secretion were
not observed. In experimental epilepsy Franc, ois-Franck and
Pitres found, both in the goat's foot and the dog's, that drops of
sweat were exuded during the convulsions, and Adamkiewicz,
in cases of partial epilepsy in man, noted abundant perspiration
in the skin of the limb that was convulsed.
The observations of Bochefontaine and others on gastric,
biliary, and urinary secretions gave no definite results. But
Bochefontaine, Francois - Franck and Pitres, Bechterew and
Mislawsky, and Sherrington, obtained more positive vesical re-
actions on exciting different points of the motor area. According
to von Pfungen (1906), the movements of the gut can also be
influenced by cortical stimulation.
VIII. Intimately connected with the study of the motor
effects obtained on cortical faradisation, are the epileptiform
convulsive phenomena which are often produced when the currents
employed are unduly strong or applied for too long a time, or
when the cerebral cortex is abnormally excitable. Hitzig and
Fritsch, who discovered the excitability of the cortex, first pointed
out this fact, and recognised that the epileptic attacks began
with convulsions of the muscles corresponding to the centre first
excited, and afterwards spread to other muscular groups. Shortly
before their discovery, however, Hughlings Jackson had concluded
from the clinical study of epileptiform convulsions localised to
certain groups of muscles that certain forms of epilepsy depend
on lesions of cortical centres which produce periodical discharges
(discharging lesions) in the direction of the corpus striatum. The
observations of Hitzig and Fritsch and of Ferrier (187-i) may be
taken as experimental confirmation of Jackson's theory.
The epileptic convulsions obtained on cortical faradisation
differ from simple motor reactions because they persist and
sometimes increase after the stimulus has ceased, and because of
x THE FORE-BRAIN 575
their tendency to spread to adjacent groups of muscles till they
become general, as if the stimulus only discharged an excitatory
process which develops independently of external stimuli.
The epileptic discharge due to cortical faradisation always
liegins in the. muscular group which corresponds to the cortical
motor centre stimulated. According to the strength and duration
of the stimulus, or the excitability of the centre stimulated, it
may remain limited to a single group of muscles, or extend to
all the muscles of one half of the body, or involve the muscles of
both sides.
The epileptic discharge follows a certain order in spreading,
which almost always corresponds to the anatomical arrangement
of the motor centres in the cortex. This fact, which is brought
out by the observations of Ferrier, Luciani and Tamburini, and
Unverricht, proves that the spread of the attack depends on the
propagation of the active epileptic state from the cortical centre
directly excited to the contiguous centres in the motor area.
It is important also to note the mode in which the epileptic
attack spreads from one half of the body to the other. According
to the observations of Unverricht, which were confirmed by
Francois- Franck and Pitres, the epileptic attack always invades
the other half of the body in a typical and constant manner, no
matter where the fit may start. After involving all the muscles
of one side in the ascending or in the descending order, the attack
invariably spreads to the other side in the ascending order, viz.
from the muscles of the posterior to those of the anterior limb, and
from there to the muscles of the neck, face, etc. This rule for the
spread of the convulsions in experimental epilepsy, holds good also
with very rare exceptions for the spread of the convulsions of
epilepsy in man.
The duration of each experimental fit varies from a few seconds
to two or more minutes. Sometimes after the attack is over, it
recurs spontaneously after a brief pause ; at other times the
animal may pass into a true epileptic state (status epilepticus), in
which the convulsions diminish or become more severe, but do not
cease entirely. The animal of course becomes exhausted and dies
after a few hours.
It is interesting to note that both in simple epileptic seizures,
and in recurrent attacks, or in the epileptic state, the muscles are
not all equally involved in the convulsions. This agrees with the
fact that the excitability of the various cortical motor centres is
not uniform, but varies in different individuals and in the same
individual at different periods of the experiment. Often indeed a
current of moderate strength will not elicit an attack when applied
to one focus, while a weak current will suffice to provoke the
attack if applied to another centre.
According to Unverricht, the body-temperature rises from
576 PHYSIOLOGY CHAP.
1° to 2° C. during an attack of epilepsy; and in the epileptic state
the temperature may reach 44° 0. The rise of temperature during
the fits is certainly in relation with the intensity and spread of
the muscular convulsions.
When the cerebral cortex, either from individual predis-
positions, or from special conditions due to the operation, is in a
state of abnormally increased excitability, an epileptic attack may
be retiexly excited by stimulation of a sensory nerve (Franeois-
Franck). Under ordinary conditions stimulation of the inex-
citable parts of the brain cannot induce an epileptic attack, but
if the motor area, i.e. the whole or certain of the excitable parts
are in a state of hyper-excitability, owing to exposure to the air or
FIG. ~2'.H.- .17, epileptoid lit, tracing from muse, extensor CTiiris. (FianQois-Franck and Pitres.)
TliH fit falls into three periods ; 1, a tniiii- period, corresponding to the duration of the electrical
excitation K ; 2, at (lie close of cortical stimulation, the tetanic condition is reinforced ; 3, the
I'lnnii- period, in which the muscle gradually relaxes.
to previous stimulation, application of the faradic current to the
cortex of the occipital or parieto- temporal lobe (i.e. to points
more or less remote from the motor area) may also evoke an
epileptic fit. Does this fact depend on physical conduction of the
current to the hyper-excitable region, or have areas become hyper-
excitable which do not normally respond to artificial stimuli ?
The latter supposition agrees with the fact that spontaneous
epilepsy (whether idiopathic or Jacksouian) is generally preceded
by a sensory aura which varies in character, and is evidently due
to excitation of different sensory areas of the cortex. It is im-
portant to note that in Jacksonian seizures, unlike even the
mildest form of idiopathic epilepsy, the attack is accompanied by
a disturbance, but never by complete loss, of consciousness.
By means of a tracing on a rotating drum from one muscle of
a limb, Frangois-Franck and Pitres were able to investigate the
muscular phenomena of the epileptic fit produced by electrical
x THE FORE-BBAIN 577
excitation of the motor area. They observed that the attack con-
sists of two phases, a tonic and a clonic stage. As shown in Fig.
294, the tonic phase persists, and reaches its maximum after the
cessation of tetanisation ; the clonic phase lasts longer, and is
characterised by violent, but less frequent and irregular, muscular
contractions. The tonic phase may be altogether absent, especi-
ally it' the animal is deeply under the anaesthetic ; then the con-
tractions are very pronounced, and the intervals between them
increase as the muscle relaxes.
These facts were confirmed by Horsley and Schafer in both
dogs and monkeys. According to Charcot partial epileptic attacks,
which he terms vibratory, because they consist of simple clouic
spasms definitely separated from one another, can be observed in
man. In idiopathic epilepsy, on the contrary, according to Brown-
Sequard, the initial tonic phase is never absent.
We have already considered the organic changes (respiratory,
cardiac, vascular, secretory, visceral, etc.) which accompany epi-
leptic seizures. Franc,ois-Franck first analysed these minutely by
means of the graphic method, and demonstrated that the epileptic
organic effects can be elicited without convulsions of the voluntary
muscles when the cerebral cortex of a curarised dog is electrically
stimulated with strong currents, under artificial respiration.
Besides faradisation of the brain, the development of spontaneous
epileptic fits may be observed in animals in which a part of the
cortex has been destroyed. This fact affords experimental con-
firmation of Jackson's clinical observations. The first four cases
of epilepsy in dogs after extirpation of part of the motor area were
described by Hitzig. He did not discuss the pathogenesis of
epilepsy ; but confined himself to the simple statement that lesions
of the cerebral cortex may induce epilepsy.
While experimenting on the brain, we frequently had oppor-
tunities of observing various forms of epileptic convulsions which
developed spontaneously, under different conditions, in dogs and
monkeys after previous operations on the cerebral cortex, and are
significant in the pathogenesis of epilepsy. We published a
Memoir in 1878 in which — after a critical examination of the
different cases of epilepsy due to lesions of the cortex — we put
forward a general theory of the cortical origin of epilepsy, whether
Jacksonian or idiopathic, and stated that the motor area of the
cerebral cortex represents the central organ of epileptic con-
vulsions. Direct or indirect excitation of this area due to any
cause is the essential factor of the epileptic seizure. The excita-
tii in of the bulb is probably an accessory, complementary factor,
which is not indispensable. Shortly stated, the following are the
arguments in favour of, and opposed to, this theory :—
(a) When the epilepsy develops in animals after partial
destruction of the motor area on one side the tonic-clonic con-
VOL. in 2 P
578 PHYSIOLOGY CHAP.
vulsions do not involve all the muscles of the opposite side ; they
merely involve the muscular groups of which the centres are
intact, while those groups of which the centres have been excised
escape.
(6) After destruction of the whole motor area on one side,
faradisation of the subjacent white matter, even with the strongest
currents, may fail to elicit true epileptic convulsions, though these
are readily evoked when the stimulation is applied to the cortex
of the motor area (Francois-Franck and Pitres, Fig. 295).
(c) Occasionally, however, when the motor area on one side has
been extirpated, electrical stimulation of the subjacent white
matter may give rise to epilepsy. But in this case the convulsions
A B
YIG. 295. — Curves from a dog's musclf i>roilurp<l l>y strong excitation.
begin not in the muscles of the opposite side of the body, but in
those of the side excited. This shows that excitation of the white
matter produces the attack not through the bulb, but by trans-
mission of the excitation along association paths to the motor area
of the other hemisphere (Bubnoff and Heidenhain.)
(d) This is confirmed by the fact that after bilateral extirpa-
tion of the motor zone electrical stimulation of the subjacent
medullary substance invariably fails to excite an epileptic attack,
no matter how strong the current (Bubnoff and Heidenhain).
(e) If after incomplete extirpation of the motor area on one
side the portion left intact be stimulated, diffuse epileptic con-
vulsions may involve all the muscles, with the exception of
the groups represented in the area that had been destrovrd
(Uuverricht).
(/) If during the initial phase of an epileptic attack produced
by laradising the motor area the sigmoid gyrus of the dog is
x THE FORE-BRAIN 579
excised, the attack can immediately he arrested (H. Munk). In
the early stage of an epileptic attack it is not infrequently possihle
by extirpating the centre of one extremity to prevent the spread
of the convulsion to that limb, though the rest of the body is
violently convulsed. In other cases it is possible by prompt ablation
of the whole motor region on one side to arrest the convulsions on
the opposite side of the body, or on both sides. In other cases
when the general convulsions have reached their maximum
development destruction of the whole motor region of one
hemisphere fails to arrest them (Bubnoff and Heidenhain, Novi
and Luciani, Roseubach and Dauillo).
(g] The hypodermic injection of 2 mgrms. of picrotoxin, or
14 rngrms. of sulphate of quinine per kgrm. of the animal, produces
in dogs and cats vomiting, salivation, and muscular contractions in
the form of tremors or twitches of the muscles of the face, neck, and
trunk, extending subsequently to the muscles of the fore-limbs and
then to the hind -limbs. These isolated twitches become more
vigorous and frequent until the animal cries, loses consciousness,
falls on one side, and is seized with a general epileptic attack in
which the tonic phase of a few seconds is followed by a clonic
phase of one to five minutes. If the drug is again administered to
the same animal a few days after excision of the motor area on
one side, the isolated twitches of the muscles of face, trunk, and
limits, which precede the general epileptic attack, are much weaker
on the opposite side of the body. Moreover, during the fit the
convulsions are more marked in the muscles of the operated side
and less strong in the muscles of the opposite side (Rovighi and
Santini).
(h) If potassium bromide is administered to dogs for several
.days in succession the electrical excitability of the cortex is so
much reduced that even strong currents fail to produce an
epileptic attack, and when successive or lethal doses of quinine are
injected epilepsy is not evoked (Albertoni). The same negative
result is seen on injecting a dose of picrotoxin sufficient under
normal conditions to cause an epileptic, attack (Rovighi and
Santini). Inhalation of ether and chloroform also moderates and
sometimes inhibits the convulsions produced by poisoning by
picrotoxin and quinine (Rovighi and Santiui).
Certain objections, which we will examine critically in detail,
were made to these arguments which undoubtedly indicate or even
prove the cortical origin of epilepsy :—
(a) Spontaneous epileptic convulsions almost invariably develop
in animals after previous operations on the cortex, not only when
the motor area of one or the other side has been extirpated, but
also after removal of non-motor regions (Luciani). This con-
troverts the theory that the motor area is the central organ of
epilepsy (Vizioli, Morselli). Electrical stimulation of non-motor
2 P l
580 PHYSIOLOGY CHAP.
regions, as the cortex of the occipital lobe, may also produce
epilepsy (Unverricht, Framjois-Franck), arid it might be supposed,
and was in fact assumed by some, that in these cases the epileptic
attack develops independently of the motor area.
But these two groups of arguments lose all value as against
the origin of epilepsy in the cortical m< >tor area, if we admit that
in all these cases the state of excitation started in a sensory area
must necessarily be transmitted to the motor region before the
epileptic attack can occur. This is directly proved by the work
of Rosenbach and Danillo ; they found that electrical stimulation
of the occipital lobe no longer produced an epileptic attack after
the entire motor area of the homonymous side had been destroyed,
or if a narrow band of grey matter were excised between the motor
area and the excited occipital area. They further found that if
the excited occipital area were separated by an incision after the
attack had already set in, this did not cease, though it was always
arrested if the motor area was removed at the proper time.
(/3) Complete, bilateral epileptic attacks can be evoked by
exciting the motor area of one side after previous destruction of
the motor area of the opposite side (Albertoni, Fraucois-Franck
and Pitres). But this fact does not controvert the cortical origin
of epilepsy, and even confirms it, as it proves that in the bilateral
spread of the epileptic attack the epileptogenous excitation often,
if not always, diffuses to the motor centres of the bull) (or bulbo-
spinal tract), which may be considered as the accessory, comple-
mentary, though indispensable factor. Unverricht's observations
agree with this interpretation. He saw that the bilateral attack
caused by excitation of the motor zone on one side is frequently
not of equal intensity on the two sides. While the muscles of the
side opposite that excited are in dome convulsions the muscles of
the same side are in tonic contraction, or contract clonically in
the same rhythm, but less strongly than those of the opposite side.
From this he concluded that the essential part of the epileptic
attack consists in primary muscular convulsions, the indispensable,
conditions of its appearance being the integrity of the cerebral
motor area.
(y) A complete section of the corpus callosum of the cat does
not prevent the onset of a bilateral epileptic attack after electric
stimulation of the motor area of one side (Frangois-Frauck and
Pitres). But this fact does not positively exclude the interpre-
tation offered by Bubnoff and Heidenhain, that the excitation
may be transmitted from one hemisphere to the other, since the
commissural fibres of the corpus callosum have not been proved
to be the sole and exclusive connecting paths between the grey
matter of the two hemispheres. In any case the bilateral spread
of the tit may be explained by the active intervention, in a
secondary and subordinate manner, of the bulbo-spiual centres.
x THE FORE-BKAIN 581
(5) Some poisons, particularly absinthe, produce convulsive
attacks similar to those excited by electrical stimulation of the cor-
tex, when they are introduced into the circulation. These attacks
are also seen in animals in which the brain-stem is completely
severed from the brain (Magnan). Injection of a few drops of
tincture of absinthe produces inexcitability of the cerebral cortex,
with the simultaneous onset of violent epileptic seizures due to
the excitation of the bulbo- spinal centres (Francois -Franck).
Apart from these experiments we know from Owsjannikow's
work that the bulb contains a centre for common direct or reflex
convulsions, a sort of motorium commune (Chap. VII. pp. 411-13).
According to Horsley and Schiifer epileptiform convulsions can
sometimes be observed after strong and protracted stimulation of
the spinal cord, when the cord has been separated from the bulb.
These facts undoubtedly prove that diffuse epileptiform con-
vulsions may be evoked by exciting the whole of the bulbo-spinal
centres, either with circulating poisons, or by vigorous and
diffuse stimulation, independently of the brain or of the excitability
of the cerebral motor cortex. It seems, however, illogical to
compare these convulsive phenomena with genuine epileptic fits :
they have not the clinical characters of epileptic seizures which
invariably begin with symptoms of cortical disturbance, i.e. complete
loss or disturbance of consciousness, and convulsive spasms limited
to one group of muscles. If the epileptogenic excitation spreads
to the lower centres before the fit becomes general, this does not
destroy the fact that the essential origin of both Jacksonian and
idiopathic epilepsy lies in the cerebral cortex.
IX. The attempt to discover the physiological significance of
the so-called "centres" contained in the excitable area of the
cortex has produced a long series of works, giving a minute
description of the immediate and remote effects of partial or total
destruction of this area.
The majority of the experiments have been made on dogs.
If the whole of the excitable zone on one side, e.g. the left hemi-
sphere, is excised, the animal as soon as it comes out of the
anaesthetic has complete paralysis of the right side. It lies on
this side with its four limbs flexed. If the limbs are stretched
passively, it only draws the left ones back. It walks with
difficulty, turning to the left, to which side its neck and head
are also bent, and often falls owing to flexion of its right limits,
which are frequently placed with the dorsum of the foot on the
ground. The muscles of the right half of the face, which has the
immobility of a mask, are also paretic. It does not react to any
abnormal position in which the right limbs may be placed;
sensibility to pain is somewhat blunted, and tactile sensibility
seems almost lost on the right side.
This motor hemiplegia and disturbance of cutaneous and
582 PHYSIOLOGY CHAP.
muscular sensibility persists for a few hours after the operation,
but then passes off gradually, and almost entirely disappears
after a few days, so that it is difficult without careful investigation
to distinguish between the operated and the intact animal.
Evidence for these facts is given by Carville and Duret,
Albertoni and Michieli, Lussana and Lemoigne, and Luciani and
Tamburini.
The symptoms described by Goltz after complete extirpation
of the whole anterior half of the dog's left hemisphere, which
certainly included more than the whole of the excitable area on
that side, are more characteristic and detailed. At first there
was complete motor and almost complete sensory hemiplegia of
the whole of the right side. After a few days the animal improved
to the extent of walking without falling, but showed a tendency to
turn to the right, and weakness and uncertainty in the movements
of the limbs of that side. If placed on a table the animal fell
easily, and then beat the air with its right limbs, as already
noted by Hitzig. In gnawing bones, pieces readily fall out of
the right side of the mouth, as Schiff had already observed. If
the animal had been trained to give its right paw when invited,
before the operation, it would now only give the left.
According to Goltz the sensory disorders are even more
important than the motor. The disturbance of muscular sense,
as recognised by Hitzig, is unmistakable, but the disturbance of
tactile sensibility is 110 less striking, although the power of
recognising contacts on the right half of the body is not entirely
lost, as was erroneously assumed by Schiff.
JSfo less important is the description given by Goltz of the
effects of bilateral extirpation of the entire anterior half of the
hemispheres to about 7 mm. in front of the chiasma. On
recovering consciousness a few hours after the operation the
animal makes futile attempts to stand. It cannot swallow or
lap milk, but has to be artificially fed for several weeks. The
power of standing and walking, in a very shaky way at lirst and
afterwards more and more steadily, is regained before the power
of feeding itself. About two months after the operation the defect
phenomena become almost stationary.
Although the animal has recovered its power of standing
upright, walking, running, jumping, these actions are awkward
and imperfect. The hind-legs drag, and it slips easily on a smooth
floor, but can rise alone. If the bilateral lesion is tolerably sym-
metrical, it is able to walk in a straight line, or to right or left,
according to its needs ; but if the lesion is very unsymmetrical, it
leans to the side most injured, although it may turn to the opposite
side. There is no muscular paralysis, and sensibility is not lost in
any part of the body, but there is a marked hyperaesthesia of the
skin, recalling that described by Brown-Sequard after spinal liemi-
x THE FOEE-BEAIN 583
section (Chap. V. pp. .'->41 et *eq.). Notwithstanding this cutaneous
hyperaesthesia, the animal cannot use its muscles in carrying out
certain voluntary acts. It i'eeds clumsily and dirtily like a pig,
making unusual associated movements hoth with its limbs and
with its jaws and tongue. It can only pick up a hone with its
mouth after many attempts and with great trouble, and is quite
incapable of holding it between the front paws, like a normal dog,
to gnaw it. If accustomed, before the operation, to giving its paw,
the power of doing so seems entirely lost. If a piece of meat is
offered to it so that the long axis of the head has to be raised to
90°, the animal is incapable of making this movement ; it opens
and shuts its mouth in the direction of the food without power
to take it, or to direct the position of the head so that the meat
should drop into its mouth.
Another interesting result of Goltz' researches is that dogs
whose anterior cerebral lobes have been extensively mutilated on
both sides lose the power of voluntarily controlling the reflexes,
the centres of which lie in the bulbo-spinal axis. Goltz described
a series of characteristic reflex movements which are almost
constant in normal dogs on gently exciting the skin in certain
regions, and he observed that these reflexes not only persisted but
were exaggerated in dogs that had been operated on. In relation
to this diminished power of voluntary inhibition, expressed in the
apparent rise of reflex excitability, is the fact pointed out by
Goltz that dogs after removal of the anterior part of the hemispheres
become more impulsive and aggressive. Animals that had been
docile, quiet, and affectionate, became difficult to manage, ill-
tempered, and abnormally restless after the operation, and continued
so for mouths, till progressive emaciation led to death.
These facts show that the symptoms of sensory-motor paralysis
or paresis directly due to extirpation on one or both sides of the
anterior parts of the hemispheres diminish gradually till they
disappear to a large extent. The residual defect phenomena
persist till death, and consist in the animal's imperfect capacity for
acquainting itself with the position and form of objects by means
of the muscular and cutaneous senses, for using its muscles as
in the normal performance of certain voluntary acts, and ifor
voluntary inhibition. We shall presently return to this pheno-
menon in order the better to define it from the psycho-physiological
point of view.
Having thus examined the effects of total destruction of the
part of the brain which contains the excitable area, we must next,
by the method of electrical stimulation, investigate the effects of
extirpating the cortex only of certain of the lobules or centres into
which it can be divided.
Munk divided the excitable area — which he termed the
"sensory sphere" because he regarded it as the seat of tin'
584
PHYSIOLOGY
CHAP.
perceptions and representations of skin and muscle sensibility — into
seven distinct regions, corresponding to the different parts of the
opposite side of the body with which each is related, as already
demonstrated by electrical excitation. He distinguished the
centres of the anterior limb (D, Fig. 296), of the posterior limb
(0), of the head, face, and tongue (E), of the eyes (F), of the ears
(Gf), of the neck (IT), and of the back (J). As shown by the figure,
these seven regions occupy the whole of the anterior part of the
outer surface of the hemispheres: they do not form islands like
FIG. 296. — Dog's brain from above and from the side, marked out into Munk's "sensory spheres."
A, A, visual sphere ; A', focal region of visual sphere, excision of which produces psychical
blindness; It, I:, auditory sphere; J", focal region of auditory sphere, excision of which
produces ps\chic;al deafness; C-J, sensory area; < ', of tore-leg; D, of hind-leg ; E, of head ;
F, of the eye's ; G, of the ears ; H, of the neck ; ./, of the trunk.
Ferrier's excitable centres, but come into contact with one another
though they are separated by fairly sharp borders. Any lesion
in the sensory sphere must, according to Munk, result in disturb-
ance of perceptions and representations of corporeal sensibility,
differently localised according to the seat and extent of the injury.
Slight lesions only produce loss of tactile and motor representa-
tions ; graver lesions involve loss of representations of position also;
still more serious injury involves loss of representations of pressure
or contact. As the paralytic effects disappear there is recovery
first of simple representations and then of the more complex ;
the representations of pressure return first, next those of position,
lastly, the tactile and motor representations.
x THE FORE-BRAIN 585
As a concrete instance of these effects, we may, according to
Munk, describe the symptoms due to total excision of the centre
for the tore-limb in the left hemisphere (D, Fig. 296). During
the tirst three to five days after the operation these are as
follows :—
(a) Loss of appreciation of contact and pressure on the skin of
I In' /'i</ht fore-limb. — When one of the left extremities or the right
hind-limb is lightly touched with the ringer or the point of a
needle, the dog reacts at once by slight movements or tries to bite,
or, if the prick is deep, draws away its limb from the unpleasant
stimulus. When, on the contrary, the skin of the right fore-limb
is stimulated in the same way the dog takes no notice ; it only draws
the limb back when it is firmly pressed or pricked, and the animal
neither looks round nor attempts to bite, showing that the reaction
is only reflex.
(b) Loss of appreciation of the position of the same limb. — The
fore-limb can lie placed in any abnormal position, it may be adducted,
abducted, pulled forward or backward, the dorsum of the foot may
be placed on the ground, the several joints flexed or extended ; the
dog does not correct its abnormal posture and remains indifferent to
it until it begins to walk again. In the case of the other three
legs, on the contrary, the animal corrects the abnormal positions
promptly.
(c) Loss of motor representations of the right fore-limb. — This
limb is capable not only of reflex movements, but also of move-
ments associated with those of the other three limbs, as in walking,
running, and jumping. But the animal does not understand how
to use the limb separately. If it had been taught before the opera-
tion to give its right paw when desired, it is only able afterwards
to give the left ; it can no longer scratch itself, or hold a bone or
piece of meat with its right foot, but only with the left ; if placed
on a table with the right leg hanging over the edge, the animal,
though aware of the danger of falling, does not draw back its leg
for support.
(d) Loss of tactile representations in the right fore-limb. — The
operated dog is capable of walking, running, jumping, and of the
rhythmical alternation and association of movements in the four
limbs ; in a word, the coarse mechanism of the complicated move-
ments is preserved, but the finer regulation of these movements
is lost in the right fore-limb. When the animal walks it is evident
that the movements of this limb are not properly graded either in
lifting it or moving it forward, or in planting it on the ground. At
times the animal rests on the dorsum of the foot, and easily slips
on a smooth surface ; in fact, it cannot use the limb with the same
accuracy and precision as the other three legs, owing, says Munk,
to lack of tactile representations.
He defines these disturbances as "psychical paralysis of
586 PHYSIOLOGY CHAP.
sensibility and motion." They diminish gradually, and by the
second week the dog begins to recognise contacts on the skin of
the right fore -leg. The gait, too, improves. After four weeks
only a certain defect in the isolated movements of this limb can be
perceived, with a slight lack of precision and dexterity in the com-
plicated movements of locomotion. Even these small disturbances,
however, have disappeared ten weeks after the operation.
Very different are the effects of total or partial removal of the
excitable area of the cortex in the ape. Goltz described a Macacus,
in which the cortex of the frontal and parietal lobes of the left
hemisphere was destroyed by two operations. This monkey was
kept under observation for eleven years. Completely hemiplegic
immediately after the operation, after a few months it was only
hemiparetic in all the muscles of the right side. In slow walking
it used both feet and the left hand, while the right hand was
generally held up in the air. In scratching and for grasping the
food offered to it, it always used the left hand.
The clumsy, imperfect manner in which the right limbs were
used in walking, jumping, and climbing, showed that cutaneous
and muscular sensibility were affected. In fact, the ape did not
recognise slight contacts on the skin of the right limbs, while the
same contacts were readily appreciated on the left. But the skin
of the right side was not entirely insensitive ; moderate pressure on
the right paw was plainly felt by the animal, which showed that it
was able to localise it.
The inability to use the right hand in isolated purposive acts
depends partially on the blunting of cutaneous sensibility. If the
monkey is offered a large apple which it cannot hold with the left
hand alone, it uses the right hand as well to lift it to its mouth.
If the left hand is held while the monkey is offered a piece of sugar,
it stretches out its right hand slowly, evidently overcoming some
resistance to the voluntary impulses. By repeated efforts it can
learn once more to give its right hand and make a military salute
with it ; but the use of the right hand always remains a difficulty.
Some effort is evidently required to extend the fingers completely
and grasp objects with them, which implies a commencing con-
tracture of their muscles. The great difference in the power of using
the two hands is shown by the following experiment : if the monkey
is set on a table and its left hand held while some cherries are
thrown down in front of it, the animal will carefully and clumsily
use its right hand to take them one after another and put them
in its mouth. But as soon as the left hand is liberated it uses it
with astonishing dexterity to catch up the fruit.
These observations, as a whole, show that the excitable area is
more important in the monkey than in the dog for the normal
control of the muscles. Years after the operation, residual
phenomena of deficiency are recognisable in apes as a slight degree
X
THE FOEE-BEAIN
587
<>!' motor paresis and a certain blunting of cutaneous and muscular
sensibility.
Munk's experiments refer particularly, to the effects of isolated
extirpation of several regions of bis sensory sphere, which are
somewhat differently localised in monkeys and in dogs (Fig. 297).
His results are a complete contrast to those described for dogs ;
the defect phenomena in the different forms of cutaneous and
muscular sensibility are perfectly localised to the parts of which
the centre had been destroyed. Just as the movements produced
by stimulation of different regions of the Eolandic area are due
FIG. 297. — Mattmis brain from above ami from the side, showing the respective sensory areas
as in last figure. (From H. Munk.)
to awakening of the sensations which normally accompany such
movements, so the motor paralysis consequent on extirpation of
these regions is, according to Munk, due to loss of the same sensa-
tions. Again, after transaction of the dorsal roots of a limb its
voluntary motility is largely reduced or abolished (Pani/zi, Baldi).
It follows logically from Munk's theory that after total extirpation
of any one of his sensory areas, for instance area D, there must be
total loss of cutaneous and muscular sensibility in the fore-limb on
the opposite side. Yet this is not shown either by his own experi-
ments, or by those of his numerous opponents.
Schafer states positively that in the monkey careful and
complete removal of the entire region of the cortex, which on
stimulation produces movements of the hind-limb of the opposite
side (area 0 of Munk), may not be followed by any obvious
sensory paralysis, although the limb loses its power of voluntary
movement. The extirpation of the cortex can be shown to be
complete by the fact that on exciting an epileptic lit by electrical
stimulation of other areas of the cortex, the hind-limb of the
588 PHYSIOLOGY CHAP.
opposite side takes no part in it. A similar fact was demonstrated
by Fload for the motor area of the face (area E of Munk).
According to Schafer there may be complete paralysis of
voluntary movements on the opposite side, with no appreciable
loss of sensibility, not merely after removing the cortex of a
single motor area, but also when nearly the whole of the motor
cortex has been extirpated in the monkey. This was, however,
contradicted by the observations of other workers, particularly
those published by ourselves in 1885, which were fully confirmed
by Mott in 1894 Both our results and those of Mott indicate
that a more or less extensive lesion of the Eolandic area is always
followed by more or less complete motor paralysis, associated
with an appreciable degree of defective sensibility in the limbs.
Schafer's criticism of the methods which Mott employed for
testing sensibility in the monkey does not appear to us to detract
from the value of Mott's interpretation, which for the rest agrees
with the exhaustive researches of Goltz.
At the same time we accept Schafer's conclusions that the
motor paralysis present after removal of the cortex of the
Eolandic area of the monkey cannot be interpreted, with Munk,
as entirely due to loss of sensibility. Logically speaking, the
Eolandic area cannot lie denned as sensory or motor, but must
be regarded as sensory-motor. Motor, because it represents that
portion of the cortex which is directly connected by efferent or
projection fibres with the lower motor centres of the mid-brain,
bulb, and cord, and because impulses for voluntary motor activity
and the first phase of this activity originate here; sensory,
because the voluntary acts are guided and controlled 1 >y cutaneous
and muscular sensations, so that the parts of the cortex in which
they originate must be intimately connected with the perceptual
centres for these sensations ; sensory -motor, because the dis-
turbances incident on the destruction of the Eolandic area are
neither exclusively motor nor exclusively sensory.
Another more specific objection may lie raised to Munk's
theory. He assumes a constant relation between the lesion or
destruction of each sensory region, and the seat and extent of the
disturbance of cutaneous and muscular sensibility. Our own
researches with Seppilli (1885) both on dogs and monkeys failed
to confirm this view, which is obviously opposed by facts derived
from objective observation. It is practically impossible to define
the limits of the single centres of the excitable area, and to
localise the effects of their destruction in one cutaneous region or
to one group of muscles. Removal of the cortex from any one of
the areas which responds to electrical stimulation by movements
confined to a single part of the opposite side of the body produces
paralytic effects which predominate in, but are not entirely
confined to that part, as they also spread more or less to adjacent
X
THE FOEE-BEAIN
589
This shows that even it' the electrical method is a
v;ilua,l»le means of localising the foci of maximal excitability it is
worthless for defining the total area of each centre. These areas
probably radiate out from the foci, overlapping and partially
fusing with the adjacent centres of other regions of the body, so
that it is impossible to destroy them separately.
Lastly, it must be noted as a serious objection to Hunk's
theory that the paralytic phenomena which he described are
transient and disappear almost completely in a few weeks, even
when the cortex has been entirely removed from the corresponding
sensory regions. How are we to explain this fact without
FIG. L".I*. Sriis.ii y-motor ami of human cerebral cortex. The cortex of the paracentral lobe of the
mesial surface, which is nut visible in the figure, also forms part of the sensory-motor area.
admitting the existence of other sub-cortical centres, able
vicariously to assume the psychical functions of the centres that
have been destroyed? But if this theory be accepted, Munk's
hypothesis, which confines all psychical functions to the cortex, is
overthrown.
One point remains: granting the mixed sensory and motor
character of the excitable area of the cortex, are we to assume
that in this area the sensory elements are completely mingled
with the motor as first suggested by Tamburini in 1876, or are
they partially mingled and partially separate ?
The localisation in the human brain of that area of the cortex
which is in relation with voluntary movement is dependent more
on a series of clinical and anatomo-pathological observations than
on electrical stimulation of the cortex. Many reliable authors
590 PHYSIOLOGY CHAP.
held that the motor zone of the cerebral cortex of , man has
approximately the same extent as that of the inferior apes, and
comprises both the central or Kolandic convolutions and the para-
central lobe and foot of the frontal convolutions. This view is
supported by positive and negative cases. Whenever there is
paralysis of voluntary movement of cortical origin, localised to
one half of the body, the post - mortem examination shows a
destructive lesion in this region of the opposite hemispheres, while
lesions of other parts of the cortex are not accompanied by any
obvious paralysis of voluntary movement during life.
As regards the division of the human motor area into different
centres corresponding with the different muscular groups, clinical
observation agrees with the results of physiological experiment on
monkeys (Fig. 298). The paralysis of the muscles, the centre of
which has been destroyed, is usually complete, and diminishes in
adults less readily than in monkeys, showing that in man the
motor area is of more importance than in monkeys in the
execution of voluntary movements, just as it is more important in
monkeys than in dogs. In man, too, it can sometimes be shown
that a muscle which is incapable of carrying out any isolated
voluntary contraction preserves its power of acting in association
with other muscles.
Contracture is seen more readily in man than in the monkey.
It consists in a state of hypertonus of the paralysed muscles, due in
all probability to suppression of the inhibitory impulses which the
spinal centres habitually receive from the cerebral cortex, while
the tonic influences constantly flowing to these centres from the
cerebellum persist. It can be seen in man, and to a lesser degree
in monkeys, that in hemiplegia from cerebral lesions exaggera-
tion of spinal reflexes is associated with contracture, while in
paraplegia from total transverse lesions of the cord contractures
never occur, and the spinal reflexes are diminished or abolished.
So far the most reliable observers agree. But when it comes
to confirming by clinical and anatomo- pathological observation
the conclusions obtained from animals in regard to the localisation
of cutaneous and muscular sensibility in the cortex, there is
much controversy.
In their first publications (1877-79) Charcot and Pitres cited a
series of cases of cortical motor paralysis in which cutaneous and
muscular sensibility remained perfectly intact. Tripier (1880)
was the first who maintained from his own clinical observations
that the motor area of the Kolandic region is at the same time a
sensory zone, because lesions of it produce disturbances of motility
and sensibility. Petrina (1881), Exner (1881), Lisso (1882), main-
tained the same view. In a subsequent clinical study (1883),
Charcot and Pitres opposed this tendency. While admitting the
force of the clinical facts adduced by Tripier and other observers
x THE FORE-BRAIN 591
they thought it an exaggeration to assume that destructive lesions
of the motor area are invariably accompanied by disturbance
of sensibility. In their final publication (1895), which gives a
very lucid summary of the results of clinical observations as a
whole, they came to the following conclusion :—
"Paralysis < if cortical origin may be accompanied by disturbances
df cutaneous and muscular sensibility, but these sensory troubles
which are sometimes associated with the motor paralysis are in
no constant and inevitable relation with the lesions of the motor
zone. The cortical motor centres of the Rolandic area are not
therefore sensory-motor organs."
Luciani and Seppilli (1885) concluded after a critical ex-
amination of 47 clinical cases that: — "There is a vast area,
including the anterior part of the frontal lobe, the temporal
lobe, and the occipital lobe, which is in no relation with
cutaneous and muscular sensibility. As disease of the posterior
parts of the three frontal, the two ascending or central convolu-
tions, the paracentral lobule and the two parietal gyri produces
disturbances of cutaneous and muscular sensibility, we rightly
ascribe a sensory function to them, and regard them as belonging
to the centre of cutaneous-muscular sensibility in man. As we
can see, this centre is more extensive than the so-called motor
area, since in addition to the Rolandic convolutions it also com-
prises the two parietals and the posterior portions of the three
frontal c< mv< ilutions.
" Disturbance of cutaneous sensibility may occur unaccompanied
by any alteration of muscular sensation. On the other hand, in
three of our cases there was disturbance of the muscle -sense
without paralysis of movement and with no alteration of cutaneous
sensibility, so that it seems as if in man the areas of the brain
surface, lesions of which produce alteration of movement and dis-
turbance of muscular and cutaneous sensibility, are not identical."
Mills, too (1890-1901), asserted that many cases had been
published in which there were lesions of the motor area with no
disturbance of sensibility. In several cases of lesions of the cortex
of the Rolaudic area after the surgical extirpation of tumours,
careful examination of the patient showed that sensibility was
intact.
In his review- of the whole clinical literature Schafer (1900)
stated that the cases of more or less circumscribed lesions in the
h'olandic area, in which sensibility was not disturbed, amounted
to 66 per cent.
Von Monakow (1902) from his most recent observations con-
firmed the conclusion of Luciani and Seppilli. He states expressly
that lesions of the cortex of the precentral gyrus occasionally, I >ut not
always, nor permanently, cause alterations of sensibility associated
witli motor paralysis or paresis. On the other hand, he states
592
PHYSIOLOGY
CHAP.
that in recent years a large number of cases of true disturbance,
of sensibility have been published, with complete absence of henii-
plegic symptoms, due to extensive destructive lesions of the
parietal lobe, while the cortex of the precentral gyrus was intact.
The latter must therefore be the true motor area, as shown by the
experiments of Sherrington and Krause on anthropoid apes, and
on man by the electrical method (see Fig. 281, p. 556; Fig. 283,
p. 559).
These recent positive cases quoted by Cox, Mills, Eedlich,
POT
POT
A
por
Fir,. 299.— Diagram of projection and association areas. (From Flechsi^.) >'£,', sensory-motor
area; V, visual area; .•!, auditory area; F, frontal association area; /, association area <>1
insul'a; POT, parieto-oceipito-temporal association area.
Spiller, and Oppenheim, are supported by another series of older
negative cases, described by Bastian, Dana, Heuschen, Dejeriue,
and others, which confirm the same theory. So that from clinical
data we are forced to conclude with Monakow that hemiplegia
of cortical origin may occur without hemianaesthesia, and henii-
anaesthesia, particularly with disturbance of muscular sense,
without true hemiplegia. Cortical hemiplegia GC hemiparesis is
almost always associated with a lesion of the precentral con-
volution, and the hemianaesthesia or hemihypoaesthesia is
associated with lesions of the convolutions that lie behind the
central or Eolandic sulcus.
Monakow, too, applied the term sensory-motor sphere to a
THE FORE-BRAIN
593
more extended region than the Rolandic area of the human 1 train ;
this he terms the ceutro-parietal region, which includes, in addition
to the two central convolutions and the supramarginal gyrus, the
anterior part of the upper and lower parietal lohes. Within this
extensive centro-parietal region lie both the cortical terminations
of the neurones of cutaneous and muscular sensibility and the
nerve-cells in which voluntary movement is initiated. But the
sensory elements are not completely mingled with the motor ;
POT
V-
Fn
t. 300.— Plan of projection and association centres. (After Flechsig.) N/-.', sriisory-motor area ;
I", visual area; A, auditory area; F, frontal association area; /, association area of insula;
POT, parieto-occipito-temporal association area ; 0, olfactory area.
the former extend more particularly' behind the central sulcus, the
latter lie almost completely in front of it.
This theory agrees fairly well with Flechsig's observations,
which are founded on the myelination of the projection fibres of
the corona radiata during embryonic development and the first
months of extra-uterine life. He states that the centro-parietal
zone extends backward to the posterior border of the post-central
convolution and the paraceiitral lobule; forward, to the frontal
convolutions, reaching the operculum below, and the corpus
callosum at the medial surface (Figs. 299, 300). According to
Flechsig, the origins of the pyramidal tracts do not spring
uniformly from the whole of this centro-parietal zone and in
VOL. in 2 Q
594 PHYSIOLOGY CHAP.
direct relation with the sensory endings, but lie chiefly in the
paracentral lobule, the precentral gyrus, the introflexed cortex of
the Rolandic sulcus (fissure), and the posterior segment of the first
frontal convolution. According to Flechsig's later conclusions
(1904), the sensory -motor zone, properly so-called, lies only within
the Rolandic fissure ; the convexity of the precentral convolution
is almost purely motor, and the convexity of the post-central
convolution is almost purely sensory. This also agrees with the
fact that the giant pyramidal cells are very few in the cortex of
the post-central convolution (Brodmann). But Flechsig's diagram
seems to us incorrect, as it makes the boundary between the
mixed zone and the sensory and motor zones, and between these
and the inexcitable frontal and parietal limiting zones, too sharp
and distinct.
X. The functions of the sensory-motor area of the cerebral
cortex are intimately connected with those of the sub-cortical grey
nuclei which are situated toward the base of the cerebral hemi-
sphere, the principal being the so-called corpora striata, i.e. the
caudate and lenticular nuclei. As shown by Fig. 263 (p. 530), the
caudate nucleus is the medial, intra-ventricular portion, the
lenticular the lateral extra- ventricular part of the corpus striatum.
The two nuclei are separated from each other by a layer of white
fibres — the so-called internal capsule — which are continuous with
the fibres of the white matter of the hemispheres and spread out
like a fan in the direction of the cortex (corona radiata of Eeil).
The two nuclei, however, are not completely separated, as there
are a number of small bridges of grey matter, particularly in the
anterior limb of the capsule, which unite them.
From the phylogenetic and ontogenetic point of view the basal
ganglion or corpus striatum precedes the formation of the mantle
or pallium, and constitutes the base of the telencephalon or fore-
brain, which develops from the first secondary vesicle. From this
fact it may be concluded with probability that the functions of the
two principal nuclei of the corpus striatum in mammals and man
do not differ essentially from, and are of the same order as, those
of the cerebral cortex.
A number of clinical and anatomo-pathological observations on
man have proved that an apoplexy which injures the fibres of the
middle third of the internal capsule produces sensory and motor
hemiplegia on the opposite side of the body, showing that the
fibres of this segment of the capsule are in connection with the
sensory -motor area of the cortex. On the other hand, experiments
on animals have shown that total extirpation of this area pro-
duces degeneration of the whole of the pyramidal tract in the
middle third of the capsule. Lastly, it is proved by anatomy and
experiment that the fibres of the anterior segment of the capsule
are in connection with the prefrontal region of the pallium,
x THE FOKE-BKAIN 595
and those of the posterior segment with the temporo- occipital
region.
Besides these fibres whicli unite the cerebral cortex with
subcortical centres the internal capsule contains many other
bundles: as those which unite the corpus striatum with the
thalamus and those which connect the cortex with the thulamus.
lleference should be made to the most recent text-books of the
anatomy of the nerve-centres for the origin, arrangement, and
course of this very complex system of projection and association
fibres.
The nuclei of the corpus striatum, unlike those of the optic
thalamus, are not in close connection with the cerebral cortex.
This was clearly brought out by Gudden (1872), who found that
after extirpation of the sigmoid gyrus in the dog there is marked
atrophy of the thalamus, while the caudate nucleus and putamen
undergo only a slight diminution in size (Biauchi and d'Abundo).
Many of the projection fibres that run from the corona radiata to
the internal capsule also run through the corpus striatum, but are
connected with it only by slender collaterals, the principal branches
running to the grey matter of the thalamus, pons, bulb, and cord.
This different relation in which the cortex stands to the corpora
striata which form part of the prosencephalon, and to the optic
thalami which belong to the diencephalon or 'tween brain,
harmonises with the theory which holds the basal nuclei to be an
integral and complementary part of the cortical system in general,
and particularly of the sensory-motor sphere.
The physiological significance of the basal nuclei was the
subject in the past of very discordant hypotheses, 'which were
either pure speculation or were based on inadequate anatomical,
clinical, and experimental observations, which need not now
concern us. Disease confined to the grey matter of the caudate
and lenticular nuclei, without lesions of the fibres of the internal
capsule, are rare, and not always properly observed and described
in the patient's lifetime. Experimental lesions of these nuclei,
owing to their position and connections, inevitably involve damage
to 'surrounding parts. This explains why the physiology of the
corpora striata is still rudimentary.
It is possible indirectly to form an approximately correct
conception of the functions of the corpora striata, by comparing
the defect phenomena which ensue on extensive extirpation of the
cerebral cortex of the dog, including the whole sensory -motor
area, with those seen after complete destruction of the cortex and
also of the corpora striata. In our 1878 memoir (with Tamburini)
on the sensory -motor area of the dog, we put forward the.
hypothesis — in order to account for the partial and fairly rapid
compensation of the paralytic symptoms — that the basal ganglia
were capable of vicariously assuming the functions of the excised
2 Q l
596 PHYSIOLOGY CHAP.
cortical region. In our; 1885 monograph (with Seppilli) on cerebral
localisation, we supported this view by observations on a dog in
which the whole of the corpus striatum and anterior part of
the thalamus were destroyed on one side, in addition to the
excitable area. In this case the usual motor and sensory defect
phenomena of the opposite side persisted for more than nine
months after the operation, which is never the case when
the operation involves the cortex only, or the whole anterior
half of the brain is destroyed, as shown by the classical ex-
periments of Goltz. In all these cases the paralytic symptoms
are so slight after a few days or weeks that they seem to have
entirely disappeared unless they are carefully sought for. It
seems to us therefore legitimate to conclude that the basal ganglia
have the same function as the sensory-motor zone of the cortex, and
that the greater persistence and severity of the defect symptoms
in the dog were due to the destruction of both the corpora striata
and the cortex.
Direct experimental investigation of the basal ganglia was first
attempted by Nothnagel on rabbits (1876), by the injection of a
few drops of chromic acid, and by a trochar from which blades
could be projected, which he inserted through the interhemispheri-
cal fissure into the third ventricle ; on turning it round he
destroyed the head of the caudate nucleus. Among his observa-
tions the fact is worthy of notice that an irritative lesion of the
head of this nucleus, which he called nodus cursurius, produces in
the animal an irresistible tendency to run. This fact was confirmed
by Fournier and by Ifezek, but denied by Schwohu and Eckhard.
After injections of chromic acid into the anterior half of the
lenticular nucleus, Nothnagel noted paralysis of the muscles of
the limbs, without perceptible alteration of sensibility to pain.
Carville and Duret (1875), 011 repeating the experiments on the
caudate and lenticular nuclei, observed hemiplegia of the opposite
side, which was more serious when the internal capsule was
badly injured. They surmised that Nothnagel, by using chromic
acid, had also injured the capsule.
Johannsen (1885), on faradic excitation of the lenticular
nucleus, observed first tonic contractions and then clonic twitches
in the muscles of the opposite side, sometimes of the same side
also. He noted that these epileptoid effects occurred also when
the excitable cortex was partially destroyed ; and they were
consequently independent of spread of the current to the cortical
motor area. The epileptoid attacks were more diffuse on exciting
the middle and inner third of the lenticular nucleus ; and more
confined to special groups of muscles when the posterior segment
of the nucleus is excited.
Baginski and Lehmann (1886) in studying the functions of the
caudate nucleus used an aspirator, connected with a thin glass
x THE FOEE-BEAIN 597
tube introduced through ;i small aperture in the skull; on remov-
ing part of the caudate nucleus by this means they observed
symptoms of sensory and motor defect on the opposite side, but
only of short duration. They also observed a rise of the animal's
temperature, for several days, to 40°, an effect previously noted by
Sachs, Ott, and Eichet.
Sgobho (1892) again employed Nothnagel's trochar to destroy
the caudate or the lenticular nucleus alone, or the motor area, or
the motor area and basal ganglia. But his notes of the experiments
leave much to be desired ; he neglected sensory changes altogether.
Still he noted the interesting fact that simultaneous lesions of the
motor zone and the corpus striatum produce paralytic symptoms
which are more serious and last longer than those due to lesions
of one of these parts only.
Sellier and Verger (1898) succeeded in destroying small
portions of the basal ganglia without damaging the surrounding
parts, by means of bipolar electrodes covered so as to insulate
them except at the points. In a dog thus operated on and killed,
after forty-one days, they noted partial hemiplegia of the opposite
side, which persisted till death; tactile hemianaesthesia, which
diminished after the third week ; total loss of muscular sense,
and normal sensibility to pain. Examination of the brain revealed
a focus the size of a pea in the head of the caudate nucleus,
and spreading to the anterior segment of the internal capsule.
This excellent experiment demonstrates that the symptoms due
to lesions of the caudate nucleus are identical with those conse-
quent on ablation of the senso-motor zone.
Pagano (1906) by the exciting action of injections of curare,
which he had already employed on the cerebellum, attempted to
sin »w the special importance, in his opinion, of the caudate nucleus
as " the seat of physiological mechanisms which serve the ex-
pression of the emotions." When curare is injected into the inner
half of the anterior and median third of the head of the caudate
nucleus it excites symptoms which suggest fear ; injected into
the posterior third it gives rise to symptoms of anger ; lastly, when
it stimulates the outer part of the anterior third of this nucleus
marked visceral phenomena are seen. But the injection of curare
by Pagano's method is manifestly inadequate for exact localisation;
and the psycho-motor agitation which results gives rise to such
complex phenomena that any physiological analysis of them would
be exceedingly difficult.
Lo Monaco's experimental extirpation of the head of the caudate
nucleus through the inter-hemispherical sulcus, after section of the
corpus callosum, represent the most exact contributions to this
subject (Chap. IX. p. 520). In four dogs which survived long enough
to allow investigation of the effects and their course, the symptoms
were constantly and exclusively those of motor and sensory defect
598 PHYSIOLOGY CHAP.
on the opposite side, with little or no difference from those due to
ablation of the excitable area of the cortex. All four animals died
in violent attacks of epilepsy, one after about three months, the
other three a month or rather more after the operation.
Lo Monaco's attempts to extirpate the lenticular nucleus more
or less completely were less successful and conclusive, since this
involves removal, simultaneously, or by a preceding operation, of
a considerable area of cortex from the parietal and temporal lobe,
and thus produces partial loss of sight and hearing. In certain
experiments of partial destruction of the lenticular nucleus with-
out injury to the internal capsule, the sensory and motor symptoms
are similar to those that follow destruction of the head of the
caudate nucleus.
We may, therefore, conclude from the results obtained by
various physiological methods that the functions of the two nuclei
of the corpus striatum do not differ from those of the sensory-
motor area of the cortex.
The clinical and anatomo-pathological facts that can throw
light on the physiology of the corpus striatum in man are scanty,
but highly important, as they confirm and partially supplement
the incomplete results of experiment.
Charcot (1876) assumed that when lesions of the caudate and
lenticular nucleus are confined to these parts, and do not involve
the capsule, they either run a latent course or, if motor paralysis
ensues, it is invariably slight and transitory.
Nothnagel (1877), on the other hand, held that concomitant
lesions of the capsule were not necessary to produce complete
or incomplete motor paralysis, as was also believed by Gowers
and Oppenheim. To account for the disappearance of the
symptoms, he assumed that the function of one nucleus may be
supplemented by the homonymous nucleus on the opposite side,
or that the lenticular of one side may be supplanted by the
caudate of the same side, or vice versa. This strengthens the
view that the two nuclei have the same function.
Von Monakow distinguishes the effects of haemorrhagic lesions
from those of softening. The latter for the most part run a latent
course; the former, on the contrary, produce a typical hemiplegia
that gradually disappears, which he believed to be due to com-
pression of the capsule. Brissaud (1895) held the same opinion.
Mingazzini (1908), from the observations of nine lesions
limited to the lenticular nucleus, demonstrated unmistakably
that motor paresis of one whole side of the body, usually accom-
panied by diminution of muscular, painful, tactile and thermal
sensibility, is the symptom most frequently observed during life.
Mingazzini has no doubt that special motor paths run from the
lenticular nucleus (putamen) to the internal capsule, in association
with the pyramidal tract.
x THE FOBE-BEATN 599
Both experimental research on animals and clinical lads from
man therefore support the conclusion that the functions of the,
corpus striatum are homologous with those of the sensory-motor
area of the cerebral cortex.
XL The localisation of the area of the cortex which serves
the perception and memory of visual images has excited much
discussion.
The earliest anatomical studies for the purpose of ascertaining
which portion of the cerebral cortex was in relation with the optic
nerve, and therefore with vision, are those of B. Pauizza (1855).
When Hitzig (1874) announced that the lesions of one posterior
portion of the dog's hemisphere produced blindness on the opposite
side with paralytic dilatation of the pupil, he was unaware that
the same fact had been observed many years previously by
Panizza.
In his book on the functions of the brain (1875), Terrier
localised the cortical centre of vision, extirpation of which produces
blindness in the eye of the opposite side (Figs. 296, 297,
pp. 584, 587), in the angular gyrus of the monkey, and the
corresponding region of the second external convolution in dogs,
cats, and rabbits.
In his first communications on the visual sphere of the cortex
(1877-78), H. Munk maintained that after bilateral removal of the
cortex in area A' of the dog (Fig. 296), characteristic disturbances
of vision occurred, which he termed psychical blindness. In this
condition the animal can see, but no longer recognises the objects
which it sees, i.e. it receives visual sensations but has lost the
memory of previous visual images. If the whole of the occipital
lobe is destroyed (A A' A, Fig. 296), then, according to Munk, the
blindness is not only psychical, but absolute and permanent, which
he terms cortical Uindness. In monkeys, too, the visual sphere lies
in the occipital lobes. Partial lesion of the latter produces more
or less complete psychical 1 ilindness, extirpation of a whole occipital
lobe produces bilateral homonymous hemianopsia, namely, blindness
of the two halves of the retina of the operated side ; removal of
both occipital lobes leads to total and permanent cortical
blindness.
In the following year (1879) we found with Tamburini that
the visual centre in dogs is not confined to the cortex of the
occipital lobe, but spreads forwards to the frontal region; in
monkeys it includes the angular gyrus in addition to the cortex
of the occipital lobe. We first demonstrated that not only in
monkeys, but also in dogs, the visual zone of one side is in
relation with both retinae, and not merely with the retina of the
opposite side. But the bilateral homonymous hemianopsia or
total blindness which results from excision of the visual area on
one, or on both sides, is neither absolute nor permanent, even if, in
GOO PHYSIOLOGY CHAP.
the monkey, the whole of the occipital lobe and the angular gyms
of one or of both sides be extirpated. Terrier and Yeo (1880)
came to approximately the same conclusions in a further series of
researches on the monkey.
On the other hand, Munk, in subsequent communications
(1880-81), developed his famous theory of the projection of the
different segments of the retina on different areas of his visual
sphere in dogs. According to this theory the central area A'
corresponds with the macula lutea, or retinal area of distinct
vision of the eye of the opposte side ; the more external portion of
A with the outer segment of the retina on the same side ; the
more internal portion of A with the inner segment of the retina
on the opposite side : the anterior half of the visual sphere is
related to the upper halves of the two retinae, and its posterior
half to the lower halves of both retinae. According to Munk,
therefore, it is possible in dogs to produce blindness of any sector
of each retina by extirpating the corresponding cortical area in
the visual sphere. This partial blindness will be permanent, just
as the total blindness is permanent after complete extirpation
of both visual spheres. He sought to apply the same theory to
monkeys, but admitted that his attempts were not conclusive.
Undoubtedly if this theory of the projection of the retina on
the visual sphere of dogs had been founded on reliable experi-
mental facts, it would constitute the finest discovery in the physio-
logy of the cerebral cortex. But the subsequent researches of
Loeb, Goltz, and particularly of Luciani and Seppilli, who methodic-
ally re-tested Munk's theory, failed to substantiate it.
It is certain from our own experiments with Seppilli (1885)
that obvious visual disorders occur in dogs not only after extirpa-
tion of the occipital lobe, but also after removing any other
extensive portion of the cortex, including the frontal lobes, that is,
the region furthest from Munk's visual sphere. This agrees with
the previous experiments of Goltz, Luciani and Tamburini, Hitzig,
Lautenbach, and others. But on closer consideration of the effect
on the visual function of destruction of the different portions of
the brain, there is seen to be an important difference : the visual
disorders that result from destruction of the frontal and temporal
lobes are transitory, while those that follow removal of the
occipital and parietal lobes are permanent — the former do not
appear unless the frontal or temporal area destroyed is consider-
able— the latter can easily be seen when only a small portion of
the cortex of the parieto-occipital lobes is removed. This fact
shows plainly that the localisation of the visual centre of the dog-
in the cortex of the occipital lobe is mere speculation. Un-
doubtedly the cortex of the parietal lobe also forms an integral
part of this centre, which must spread even beyond its limits,
though it is not possible to determine the exact boundaries.
x THE FORE-BRAIN G01
Another indisputable fact, in which our results agree perfectly
with Munk, is that in dogs extensive extirpation of one occipital
lobe at once produces bilateral IK anonymous hemianopsia, which is
somewhat more extensive in the eye of the opposite side than in
the homolateral. This proves that each visual centre is in direct
relation with the more extensive nasal segment of the retina on
the opposite side, and with the less extensive temporal segment
of- the retina on the same side. Contrary, however, to Munk's
theory, our experiments further bring out the following un-
mistakable facts : —
(a-) Jfemiopic defects result not only after extensive and
complete destruction of one occipital lobe, but also after extensive
removal of the cortex of either the parietal or the temporal lobe.
This fact shows that in the dog the visual centre is not confined to
the occipital lobe, but also spreads in the cortex of adjacent lobes.
(6) Partial bilateral extirpation (outer or inner, in front or
behind) of the occipital lobes never produces definite symptoms
of partial blindness, but always more or less marked visual
disturbances distributed over different segments of both retinae.
This observation confutes the theory of retinal projection on to
the cortex.
(c) Neither the hemiopic defects due to extensive unilateral
extirpations of the occipital, parietal, and temporal regions of the
cortex, nor the visual disturbances spreading over the whole
retinal field, which occur after bilateral extirpations limited
to these regions, are permanent, but both gradually disappear.
The hemianopsia is transformed by degrees into hemiamblyopia ;
the diffuse blindness into diffuse amblyopia of the whole retina ;
lastly, the aniblyopia symptoms gradually diminish to phenomena
of simple psychical blindness, more or less severe and complete.
These facts are directly opposed to the theory of absolute and
permanent cortical blindness.
The above observations, published in 1885, were substantially
confirmed in 1903 by Shinkichi Iniamura in an important series
of researches carried out in Exner's laboratory at Vienna. He
admitted that the occipital lobe must stand in closer relation with
the visual function than other parts of the cerebral cortex. The
anatomical researches of v. Monakow and Probst show that the
occipital cortex is in direct connection with the subcortical visual
centres (external corpus geniculatum, pulvinar and anterior quad-
rigeminal body). Imamura was able with Marchi's method to
follow descending degenerations from the occipital cortex to the
subcortical visual centres, while this degeneration is absent when
the frontal lobes are destroyed.
Contrary to Munk's view, and in accordance with the state-
ments of Loeb, Hitzig, and Luciani, Imamura, after extirpating
any portion of the occipital lobe, always found hemianopsia and
602 PHYSIOLOGY CHAP.
hemiamblyopia of the side opposite to the injured hemisphere,
which were transient and only lasted from eight to twenty days.
Imamura confirmed the observations of Luciani, Loeh, and
Hitzig, that when the visual disturbances due to removal of one
portion of the cortex have disappeared, they reappear in an
aggravated form and in both eyes after a second symmetrical
lesion of the other hemisphere.
Lastly, in a final series of researches, Imamura also divided
the corpus callosum ; he confirmed Lo Monaco's observation that
this produces no appreciable effects in intact dogs, and he found
that if this operation is succeeded by unilateral extirpation of any
region of the convex surface of the brain, the usual visual disturb-
ances that follow show no tendency to disappear even within two
months. He further saw that if the corpus callosum is cut in
dogs in which the symptoms of cortical extirpation had been
compensated, the visual troubles reappear and persist. This
demonstrates the importance of the corpus callosum, as it contains
the paths through which compensation of the hemiamblyopia due
to unilateral lesions takes place.
The experimental conclusions obtained from the dog are in
evident contradiction with those obtained experimentally from
the monkey, and particularly with the anatomical and clinical
observations of Hun, Heuschen, Flechsig, and Niessl, on man,
which limit the visual sphere to the middle and lower surface of
the occipital lobe, precisely to the so-called calcarine area, in which,
according to the extensive histological researches of Brodmann,
the cortex assumes a quite characteristic structure (zona striata
of Brodmann).
A. Tschermak (1905) initiated a new series of researches,
intended to settle these differences and to determine the special
importance, in dogs as well, of the region homologous with the
calcariue area.
On stimulating the medial posterior surface of the dog's brain,
and particularly the cortex lying round the sulcus recurrens
superior, which is homologous with the calcarine fissure of the
monkey and of man, Tschermak obtained co-ordinated movements
of the eyes ; on excising the cortex of that area, he produced
hemianopsia and loss of the eye-reflexes on the opposite side. He
saw that these symptoms diminished, but did not entirely dis-
appear, even after a long period. Finally, he found descending
degeneration to the sul (cortical visual centres from the area
destroyed. Consequently in the dog the visual sphere is localised
to the medial surface of the hemispheres, in the region homologous
with the calcarine area. The parieto-occipital convexity may repre-
sent the association zone in the dog, as suggested by Flechsig.
Fr. Kurzveil (1909), working under Tschermak's guidance,
confirmed his results, and stated that the alterations in vision and
THE FORE-BRAIN
603
eye-reflexes (especially marked on the outer half of the visual
Held of flie eye of the side opposite that in which the, calcarine
region had been destroyed) persisted almost unaltered for over a
year. He, too, was able with Marchi's method to detect a
B
FIG. 301. — The dotted region of the occipital lobe indicates the extent of the area striata on the
superior surface, A; inferior surface, li ; and mesial or internal surface, C, of dog's brain.
(Campbell.)
degeneration descending towards the antero- lateral part of the
pulvinar, in the dogs operated on. Lastly, after extirpating the
eye of a new-born puppy, he found hypoplasia of the calcarine
region on the opposite side when development was complete.
Panizza, many years before, had described the same hypoplasia—
604 PHYSIOLOGY CHAP.
not localised, however, to the calcarine region, but diffuse all over
the controlateral occipital lobe.
Minkowski (1911) continued the work of Tschermak and
Kurzveil. Starting from the localisation and extent of the strintt.1
area, as described by Campbell on the upper, middle, and inner
surfaces of the occipital lobe of the dog's brain (Fig. 301), he
attempted to show that the destruction of this area on one side
produces amaurosis or permanent blindness in the temporal three-
fourths of the visual field of the opposite side, while there is
transitory amaurosis in a small nasal portion of the homolateral
visual field. From this he concludes that the visual sphere
coincides perfectly in the dog with the area striata, and that the
greater part (over three-fourths) of each retina is represented in
the area striata of the occipital lobe of the opposite side, and the
small remaining part in the area striata of both sides, mainly,
however, on the hoinonymous.
Bilateral removal of the striate area, according to Minkowski,
produces total and permanent blindness. He states that dogs
thus operated on for ever lose not merely perceptions but also
simple ocular reflexes to luminous stimulation, with the exception
of the pupil reflex.
The sub-cortical optic centres alone cannot therefore, according
to this author, subserve even the simplest visual reflexes.
We may ignore Minkowski's other statements and confine
ourselves to the consideration of this conclusion, which he has
confidently described in much detail. It is so diametrically
opposed to our own results that we immediately instituted an
experimental control by three different students in our laboratory.
Up to the present the results of excising Campbell's striate areas
on both sides, in three young dogs, have been in contradiction with
the statement which Minkowski uses as the basis of his entire
theory of the visual sphere in dogs.
During the first days after the operation, the three dogs which
had been deprived of Campbell's striate area on both sides were
not merely not blind, but were not even amblyopic. They were
capable, in walking, of avoiding contact or collision with the walls
surrounding them, the legs of chairs, or other furniture in the
vicinity. They never stumbled against obstacles placed on the
floor of the room, both irregularly and sometimes in lines and
close to each other, so that the dogs might easily have knocked
them over in passing between them, if their vision had been ever
so slightly affected. It was amazing to see how often they got by
without stumbling against any of the obstacles.
Such a flagrant contradiction between Minkowski's statement
and our own observations was quite unexpected. To test it we
killed the three dogs in order to make sure by examination that
the whole of the area striata had been destroyed on both sides.
x THE FOEE-BEAIN G05
It was found that in each of the three animals the cortical lesion
had not extended at all points to the limits assigned by Campbell
to the area striata, while at others it had exceeded them. A
small area in the front and deeper parts of the lower surface of
the area which lies on the tentorium escaped, while on its upper
and mesial surface the lesion extended somewhat further inwards
towards the parietal lobe.
The failure to destroy the whole of the area striata is, however,
quite inadequate to explain the discrepancies in the results,
particularly if we remember that, according to Minkowski, there
is a projection of the retinal element on to the visual cortex ; the
anterior region of the area striata would correspond with the
upper segment of the retina, the posterior region with its lower
segment. Since the portion of the area striata remaining intact
corresponds only with about the twentieth part of the total area,
it is easy to see that if Minkowski's theory were correct there
must have been absolute and permanent blindness of nineteen-
twentieths of both retinae, which would readily have been detected
in our careful and repeated investigations.
It has not therefore been demonstrated that the area striata
represents the whole of the visual sphere, or is more than its focal
area. This doubt is borne out by careful examination of the
microscopical preparations in our laboratory with the best technical
methods available. Till the contrary is proved, we are not justified
in assuming that there is not in dogs a definable area of the cortex
with a structure similar to that of the calcarine region of the
human brain.
Further, it is indisputable that the whole of the visual
functions, including the visual reflexes, are not localised in the
cortex, and that part — the most elementary — of them are subserved
by sub-cortical centres. It is impossible to overlook the results
< ii' our earlier researches which demonstrated, in dogs as well as
in the macaque monkey, that the blindness incident on bilateral
extirpation of the occipital lobe is temporary; and that it
becomes reduced in a few days to an amblyopia which gradually
disappears till the symptoms are merely those of psychical
blindness, in which the animals see, but fail to recognise the
objects which they see. All this was confirmed by Lo Monaco ;
he found, after removing the two occipital lobes in bulk, that the
blindness was neither absolute nor permanent in his dogs, and
only became so after the subsequent operative destruction of the
optic thalami.
Evidently Minkowski was led away by the preconceived ideas :
(«) that the visual sphere was confined to and strictly localised
in the area striata; (b) that all the visual functions had their
centre in the cerebral cortex.
If these two propositions were generally applied to the different
606
PHYSIOLOGY
CHAP.
qualities of sensations, it would have to be admitted that all
mental activities from the most complex to the simplest, including
the visual reflexes, must have their seat in the cerebral cortex — a
conclusion that contradicts all that has been set forth in the
previous chapters as to the functions of the cerebrospinal axis.
Let us see if Minkowski's theory is, partly at any rate,
applicable to the visual centres of the monkey. Munk, as we
have seen, left his researches incomplete as regards the visual
sphere in apes. The sole fact which he demonstrated, and which
we fully confirmed, was that bilateral homonymous hemianopsia
occurs after extirpation of a whole occipital lobe. But while he
took this to be a permanent symptom, we showed that it is
temporai'y,&n& that it may be reproduced by successive operations
on the same hemisphere. This proves
that in monkeys, too, the visual
sphere extends beyond the limits of
the occipital lobe. Munk did not
adduce a single experiment in sup-
port of his hypothesis of retinal
projection on the cortex, or show
that partial extirpation produces
partial blindness of one or the other
portion of the retina.
The experiments on the cortical
visual sphere of the monkey were
continued by Schafer and Sanger-
Brown in 1888. Extirpation of one
occipital lobe (Fig. 302) produces
bilateral homonymous hemianopsia
in monkeys : extirpation of both
occipital lobes produces total blind-
ness, which, however, is not permanent if these lobes alone are
injured. To produce permanent blindness it is necessary that
the lesion should extend beyond the occipital lobes, particularly
on the inner and lower surface, and include part of the cortex
of the temporal and parietal lobes (Fig. 303). Contrary to
Ferrier and Yeo, Schafer and Sanger-Brown exclude the cortex
of the angular gyrus from the visual area. The hemiopic
symptoms sometimes seen after removal of the cortex from
that gyrus disappear after a few days, and may depend on shock
extending to the contiguous occipital lobe. But this interpreta-
tion will not hold in view of the fact established by us, that the
residual disorders of vision due to extirpation of the occipital
lobes become aggravated after injury of the angular gyri.
Schafer and Sanger-Brown accepted projection from the retina
on the cortical centre of vision in monkeys, which Munk already
held for dogs. But in the monkey central vision — i.e. the area
Fir:. 302. — Brain of Mtwiwus from which
one occipital lobe had been entirely
removed, but the angular gyrus left
intact. (Scha'IVr and Sanger-Brown.)
X
THE FORE-BRAIN
607
of the centre of vision corresponding with the macula lutea —
lies (in the inner or mesial surface of the occipital lobe ; the
scheme proposed by- Munk for dogs is not therefore directly
applicable to monkeys. These authors did not test the effects
of partial destruction of the visual area ; they merely relied on
the reactions to electrical excitation, which varied in different
parts of the area.
It must, however, he remembered that electrical stimulation of
the angular gyrus, which — according to Schafer and Sanger-Brown
—is not comprised in the visual area, also produces movements of
the eye -balls. It should further be added that in 1895, after the
publication of Henschen's clinical researches, Panichi repeated
the experiments on the macaque monkey in gur laboratory, with
Ki<;. 303. — Maracus brain viewed from above, A, and from below, B. Both occipital lobes and, on
the under surface, part of the temporal lobes bad been cut away. (Schafer and Banger-Brown.)
quite different results from those of Schafer and Sanger-Brown.
He not only confirmed the fact that the visual area of monkeys
cannot be restricted to the occipital lobes, but his results
confute the view that the focus of central vision is seated in the
cortex of the calcarine fissure, cuneus, and, generally speaking, of
the mesial surface of the occipital lobe. So that the visual area
of monkeys has not been finally determined.
According to Brodrnann, the area striata of the lower apes
extends from the calcarine region over almost the whole lower,
mesial, and external surface of the occipital lobe. But not even
by accepting Minkowski's view that the visual sphere coincides
with the area striata is it possible to explain the fact that
after the bilateral destruction of the whole occipital lobe the
blindness which ensues is not permanent. A fresh series of
experiments directed to the solution of this problem is necessary.
As regards the visual area in man, it may at once be stated on
the strength of a large number of clinical cases that the lesions of
608 PHYSIOLOGY CHAP.
one occipital lobe produce bilateral visual disturbances which are
hemiopic in character ; the halves of the two retinae corresponding
to the side of the injured occipital lobe are blind (homonymous
bilateral hemianopsia). The perimetric observations made in
some of these cases show that the line of demarcation between the
blind and the seeing parts of the retina does not, as a rule, pass
through the fixation point, but to its blind side, i.e. the fovea is
not comprised in the hemiopic lesion.
Clinical evidence in many cases seems to show that the visual
area of man is better defined and less diffuse than in monkeys, as
in the latter it is more restricted than in dogs. Not a few clinical
cases, moreover, indicate that it is lesions of the inner or mesial
surface of the occipital lobe which cause the most serious dis-
turbances of vision.
Henschen (1892) maintained on the basis of his clinical and
anatomo-pathological researches that the visual area of the human
brain is confined to the cortex of the calcarine fissure, but critical
examination of the arguments on which he based this theory
shows that the visual centre cannot be contained within such
narrow limits. He has not cited a single case that is anatomically
sound, in which a lesion sharply limited to the calcarine area
produced total and permanent hemianopsia. In all cases so far
published of cortical hemianopsia there were more extensive
lesions, both of the mesial surface and of the convex surface of
the occipital lobe.
According to Dejerine and Vialet (1893) the cortical visual
centre of man occupies the whole extent of the mesial face of the
occipital lobe, limited in front by the parieto-occipital fissure,
above by the upper border of the hemisphere, below by the lower
border of the third occipital gyrus, behind by the occipital pole.
But lesions of the cortex of the three external occipital convolutions
can also produce hemianopsia, as proved by Turner (1895) and
Pick (1896). Crispolti (1902) concluded from a critical survey of
155 clinical cases that the cuneus is of chief importance for vision,
the lingual and fusiform gyri of less, but that the cortex of the
outer surface of the occipital lobe, i.e. of the three occipital con-
volutions, is also part of the visual centre.
Monakow came to the same conclusions (1897-1902) when
he referred the visual sphere of man to the three occipital con-
volutions, the entire cuneus, the lingual lobule, and the descending
gyrus, in addition to the calcarine region which forms its most
important part. Bernheimer (1900), with the myelination
method, arrived at the same conclusions. Flechsig (1901), by the
same method, located the central focus of vision in the calcarine
fissure, and the margins of the cuneus, the lingual lobule, and the
cortex of the external occipital pole ; but he admitted that it also
extended beyond these limits (V, Figs. 299, 300).
x THE FORE-BRAIN 609
Against Henschen's localisation, Monakow brought out the fact
that in cases of blindness acquired in infancy, with total degenera-
tion of the optic nerves, the cortex of the calcarine fissures does
not suffer a greater reduction of volume than the cortex of the
external convolutions of the occipital lobe.
Henschen tried to adapt Munk's theory of retinal projection
to the visual sphere. According to Henschen the upper quadrants
of the retina are represented in the upper border of the calcarine
fissure, the lower quadrants in its lower border. Against this
view it may be observed with Monakow that in cases of bilateral
hemianopsia of cortical origin in man, there is persistence of
central or macular vision even when the calcarine region as well
as the introflexed cortex in this fissure are affected. This proves
that the focus of distinct central vision cannot be limited to
a restricted cortical area. Both Sachs and Bernheimer reject the
theory of Munk and Henschen that the macula lutea is repre-
sented in a circumscribed area of the visual sphere.
Lesions of the occipital lobes not only produce hemianopsia,
but may also be associated with special psychical disorders,
characterised by alterations of the visual representations. These
disturbances differ in form and degree, from a slight difficulty in
rightly interpreting visual images to genuine psychical blindness
similar to that observed in monkeys after removal of both occipital
lobes, which when the symptoms of blindness and amblyopia have
passed, recover vision completely, but continue incapable of
recognising the objects which they see. The symptoms which
characterise psychical blindness in monkeys may be illustrated by
the following experiment : if some grapes or bits of dried fig are
scattered on the table with lumps of cork of the same size, the
ape which has lost both its visual spheres is incapable of dis-
tinguishing them by vision ; it picks them up indifferently, one
after the other, but retains the grapes, while it rejects the cork
directly it is taken into the mouth.
The same obtains in typical cases ot psychical blindness in
man. Although the individual sees to a certain extent, and
stereognostic vision is preserved, he is not capable of identifying
the objects he sees, even when familiar in everyday life. Psychical
blindness is a very complex disturbance, which depends on various
components. It is not exclusively dependent on the partial lesion
of the visual sphere, but may occur when some of the association
paths by which the visual cortex is brought into relation with
other cortical regions are interrupted.
A special form of incomplete psychical blindness seen in man
is the so-called word blindness which was first reported by
Kussmaul (1877). It is characterised by inability to comprehend
the significance of printed or written words, although the power of
expressing ideas in speech or writing is retained. The individual
VOL. in 2 R
610 PHYSIOLOGY CHAP.
affected with word blindness sees the letters and words, and can
even copy them; but he is incapable of reading them, combining
them together, or understanding them. In cases in which the
visual field is examined by the perimeter, it is found that word
blindness is sometimes independent of any change in the field,
and at other times is associated with a concentric contraction
of the field, or with hemianopsia.
Word blindness leads us to assume that, there is in the brain a
region for the perception of the graphic signs of speech and the
memory of them, which are necessary to the understanding of
their significance. But in which part of the brain is this special
centre for the visual perception of words located ? The fact that
word blindness can exist independently of any alteration in the
visual field, shows that the centre for verbal visual perceptions
lies beyond the sphere of vision properly so called. But the fact
that it may be associated with hemianopsia, or a concentric
restriction of the visual field, leads us to conclude that this centre
must lie contiguous to the centre of vision proper. There are
cases of word blindness on record in which the post-mortem
examination showed a lesion of the second left parietal convolu-
tion; this includes the angular gyms, which in our opinion
represents the anterior portion of the visual area of man.
XII. Less experimental work has been done on the localisa-
tion of the auditory area, no doul >t 1 tecause the sense of hearing is
less easy to examine in animals than vision.
Ferrier (1875) was the first to point out that the centre of
auditory sensation is represented in the ape by the cortex of the
first temporal convolution, and by the corresponding region of the
third external convolution in dogs (cf. points 14, 15, Figs. 275,
276). In fact, this part of the temporal lobe alone responds to
electrical stimulation by very definite reactions : by movements of
the ear muscles on the opposite side, while the eyes open widely, the
pupils dilate, and the eyes and head are suddenly turned to the
opposite side, as if the animal were surprised by some unexpected
sound on that side. To confirm this interpretation Ferrier
cauterised the temporal convolution. If the lesion was confined
to one side, the monkey continued to react to auditory sensations,
by moving its head if any one called it, 'but if the ear of the
operated side were plugged with wool, it seemed no longer aware
of sounds. After bilateral lesions of the upper temporal con-
volution the monkey no longer reacted to certain auditory stimuli
which under normal conditions excite attention. The deafness
assumed by Ferrier is obviously an erroneous interpretation of the
symptom. All subsequent investigation has shown unmistakably
that the auditory centre is not confined to the area indicated by
Ferrier, but its focal area is probably represented by that centre.
H. Munk (1878-81) stated that when area B of the temporal
x THE TORE-BRAIN (ill
lulu1 (Fig. 296) was destroyed <m both sides in dogs, it produced
a disturbance of hearing which he termed, psychical ilrufncss, its
characteristic being that although the animal hears, i.e. lias
auditory sensations, it has lost the perceptions and memory of the
auditory images perceived in its preyious life. This is a more
correct interpretation of the effects described by Terrier as due to
destruction of the upper temporal convolutions; the monkey was
not deaf, for it reacted to a sudden sound, but it did not respond
to calls nor to friendly addresses.
Munk's psychical deafness is a transient phenomenon, which
gradually disappears, so that after a few days the operated can
hardly he distinguished from the normal animal. But if the
whole of the temporal lobe is destroyed on both sides by sub-
sequent operations, the psychical deafness is transformed into
absolute and permanent deafness, which Munk terms cortical
deafness.
Our experiments with Tamburini (1879), and particularly
those with Seppilli (1885), brought out new and interesting facts.
They proved that the auditory centre cannot be restricted to the
limits laid down hy Terrier, nor those assumed by Munk. It
spreads more or less beyond the confines of the temporal lobe :
above, towards the parietal and occipital region ; behind, towards
the gyrus hippocampi, and mesially, towards the cornu Ammonis.
Unilateral extirpation of the auditory sphere causes bilateral
disturbance of hearing, principally in the ear of the opposite side.
When the effects of extirpation of the auditory sphere on one side,
e.g. the right, have subsided, and the opposite auditory sphere is
then destroyed, not only is auditory disturbance produced on the
right, but the deafness of the left ear which had disappeared
returns. This fact was unmistakable in six dogs under our own
observation. Here we have experimental proof that the cerebral-
ward paths that come from the cochlear nuclei undergo in-
complete decussation like the optic nerves ; and that neither the
crossed paths nor the direct are related to distinct portions of the
auditory centres, but both spread more or less uniformly through-
out these centres.
The effects of more or less extensive extirpations of the
auditory sphere consist in a more or less grave affection of hearing,
which never amounts to complete deafness. This auditory dis-
turbance is transitory and due to the shock of the operation ; as
it disappears, the signs of partial psychical deafness appear more
and more clearly, as seen by the animal's failure to appreciate the
value of sounds, noises, and calls, although it shows signs of hear-
ing them.
Bilateral extirpation of the auditory centres produces more
serious effects, even when incomplete. At first the disturbance of
hearing may amount to total deafness ; but this soon becomes
612 PHYSIOLOGY CHAP.
partial ; there is only a dulness of hearing that gradually diminishes
till nothing remains 1 >ut the more or less marked signs of psychical
deafness.
These results confute Munk's theory of cortical deafness.
We experimented almost entirely upon dogs, Schafer and
Sanger-Brown (1888) on monkeys. In h've macaques they
removed or destroyed the upper temporal convolution on both
sides, and in one they completely removed both temporal lobes.
The last operation for a time produced a state approximating to
idiocy, but hearing was not abolished in any of the animals,
perhaps not even diminished, since the inconstancy of reaction to
sounds may be interpreted as a sign of simple psychical deafness.
These results agree with our own observations on the dog, and
obviously strengthen the theory that the seat of auditory per-
ception is not confined to the cortex of the temporal lobe, but
spreads to the adjacent regions as well.
That the focal area of auditory perception lies in the upper
temporal convolution seems probable from the results of electrical
stimulation, and from Flechsig's observations as to the time at
which the myelination of its fibres takes place (Fig. 300), and
from v. Monakow's anatomical observations. The cortex of the
temporal lobe, and particularly that of the first convolution,
according to v. Monakow, is in direct communication with the
internal geniculate body, which in its turn is related to the
posterior quadrigeminal 1 todies, and these are connected with
the cochlear nerve by the lateral lemniscus and certain fibres of
the formatio reticularis.
The results of clinical and anatorno -pathological observations
on the auditory sphere of the human brain are interesting.
Generally speaking, they are definitely in favour of the theory
which we brought forward with Seppilli in 1885.
A fact which seems to be of special importance, because it is
at variance with Munk's cortical deafness, is the absence in
medical literature of any description of cases of deafness or marked
loss of hearing in one or both ears when the autopsy shows
clearly and conclusively that there was a destructive lesion,
exclusively localised to the cortex. Clinical observation brings
out a no less important positive fact — that lesions of the cortex
of the temporal lobes produce a curious mental disorder during
life, characterised by the fact that the patients, while perfectly
aware of the least sound or noise, are incapable of understanding
the significance of the words they hear. Wernicke (1874) first
described this condition, which he termed sensory aphasia, because
he took it to be an affection of the paths of auditory speech.
Kussmaul (1876) after a more profound analysis regarded it as an
incomplete form of psychical deafness, and called it word deafness,
which finds its complement in the word blindness above described.
x THE FORE-BRAIN 613
We collected (1885) 20 cases of word deafness from clinical
and anatomo- pathological observations, which on examination
yielded some important tacts showing that the region injured in
word deafness is the first and part of the second left temporal
Convolution.
Two other clinical facts prove the functional connection
between the left temporal lobe and the auditory paths of speech:
(a) the cases recorded of lesions of the right temporal lobe
unaccompanied in life by word deafness ; (b) lesions of the left
temporal lobe in left-handed individuals, which were unaccompanied
by word -deafness. There are authentic cases of left -handed
persons in whom destruction of the left convolution of Broca was
not betrayed by any disturbance of speech. The predominance
of the left brain in right-handed people is replaced by predomin-
ance of the right brain in the left-handed.
To confirm the theory that the central focus of the auditory
components that subserve acoustic perceptions and ideas lies in
the first temporal convolution, the fact may be adduced that
defective development of the temporal lobes, particularly of the
first temporal convolution, as compared with the rest of the brain
has frequently been noted at the post-mortem examination of
individuals who were deaf-mutes from birth.
XIII. Comparatively few investigations have been made upon
the cortical localisation of the olfactory and gustatory centres.
Ferrier, starting from the anatomical fact that there is a
direct connection between the olfactory tract and the gyms
hippocampi (subiculum cornu Ammonis), regards this region—
without defining its limits — as the olfactory centre. Electrical
excitation of the subiculum both in dogs and monkeys (15, Fig.
275) produces movements of sniffing in the nostril of the same
side, as though the animal perceived a strong smell. This effect,
which is not obtained from any other region of the cortex,
strengthens the presumption that the hippocampal region forms
part of the olfactory area.
It is probable, according to Ferrier, that the gustatory centre
is contiguous with or lies very near the olfactory. He believes
it is localised in the lower extremity of the second temporal
convolution, since electrical stimulation of this region sometimes,
but not always, provokes movements of the tongue and jaw, as
th< nigh the animal perceived a sensation of taste.
Ferrier tried to support his hypothesis by destroying this
region, in order to see if symptoms of loss of taste and smell
resulted. But the effects were few and uncertain : he found that
extensive destruction of the upper temporal region in the ape
might in addition to auditory disturbance produce signs of
affection of smell and taste. With more extensive cauterisation
of both temporal lobes, so as to destroy the whole, of it, inclusive
614
PHYSIOLOGY
CHAP.
of the hippocampus, he obtained temporary abolition of smell and
taste, in addition to loss of touch and hearing. None of these
experiments — as Ferrier expressly points out — can define the
exact limits of the centre of taste and smell ; but he believes that
the olfactory area is quite distinct from the area that reacts to
electrical stimulation.
Our experiments on dogs (1885) confirm the importance of
the hippocampal region for the olfactory sense. They further
Fie;. 304.— External surface of right hemisphere of female infant 54 cm. long, still-born a month
before normal period of foetal maturity. (Flechsig.) The explanation refers to this and the
following ligure.
The figures on this and the following illustration indicate the chronological order in which the
til ni's lying below the different cortical area become myelinated ; the letters show the order of
myelination of different segments of the same area. The dotted surface shows the distribution
of iinyelination, which is approximately the same as that observed in male infants of a month
old. The temporal lobe is pressed downwards, so as to open the Sylvian fissure and make visible
the convolutions of the island of Reil. The elementary fields become myelinated in the following
imler: 1, lamina perforata anterior, trigonum olfactorium (invisible in both figures); 2, lolmlN
paracentralis, upper third of the two central convolutions ; '2b, median third of posterior central
convolution and, later, the corresponding convex segment of the pie-central (motor area); 3,
septum lucidum ; 4tt, 4&, gyms hippocampi ; 5, lips of calcarine fissure, occipital pole, gyms
ilcM-endens ; ii, gyrus fornicatus ; 7, 1st temporal convolution; 7", upper' part of posterior con-
volution of island; 8, foot of 1st frontal; Sb, subjacent part of gyrus fornicatus; ti, supeiim
segment of cuneus ; 10, inner surface of temporal pole ; 11, transverse convolution of frontal lobe,
orbital portion of 3rd frontal; IL.', gyrus siibangularis ; 13, gyrus supra-angularis ; 14, 14b, 1st
temporal ; 15, 15b, 1st frontal, particularly the inner sin-face and anterior part of gyrus fornicatus ;
Iti, 1st parietal; 17, 17ft, areas round field 5; 18, ISb, foot of 2nd and 3rd frontal; I'.i, gyrus
.-iiprainarginalis ; 20, 3rd occipital; 21, posterior segment of 1st parietal; 22, greater part of
island; 23, gyrus occipito-temporalis ; 24, 2nd occipital; 25, small posterior inferior portion of
gyrus fornicatus (omitted); 26, at base of frontal lobe (omitted); 27, median segment of 3nl
hontal; 28, polar portion of 1st frontal (omitted); 20, rest of gyms supramarginalis (omitted) ;
30 (erroneously marked 35), upper part of 2nd frontal; 31, over field 12 (omitted); 32, lower part.
of island; 33, portion of gyrus fornicatus lying below praecuneus ; 34. gyrus angularis ; 35, inner
surface, of frontal lobe ; 36, 2nd and 3rd temporal convolution.
show that the pes hippocampi major or the cornu Ammonis is
an important part of the olfactory centre.
THE FORE-BILUX
615
This research was continued by Fasola with a view to
determining the physiological value of the cornu Ainmonis, which
is a special part of the cerebral cortex. Fasola showed that in
dogs the cornu Ainmonis is concerned not only with the olfactory
sense, but also with vision and hearing. It is a part of the brain
in which a partial fusion of different sensory centres takes place,
such as we showed in the parietal lobe of dogs.
H. Munk records the case of a dog which became blind after
the destruction of the occipital cortex, and which seemed to have
also lost the sense of smell. On making sections it was found
. ' mf Y .
\ 'y*&::£-:;.: \
\
FIG. 30"). — Internal surface of left hemisphere of same infant.
that the entire hippocampus on both sides was transformed into
a thin-walled cyst.
Hughlings Jackson and Beevor observed a case of tumour of
the right hippocampal convolution, in which the patient had
subjective olfactory sensations.
Flechsig, too, by investigating the myelination of the fibres
during development, succeeded in mapping out a cortical field in
the hippocampal region which lie held, in agreement with these
few physiological and clinical observations, to represent the
olfactory centre (Figs. 304, 305). It is probable, however, from
anatomical facts that this centre is not entirely confined to the
hippocampal region. The researches of Meynert, Brown, Golgi,
and others show that in the human brain the olfactory tract has
three roots, the outer of which ends in the hippocampal convolution,
616 PHYSIOLOGY CHAP.
the middle in the anterior perforated substance, the inner in the
frontal extremity of the gyrus corporis callosi.
Brown (1879) concluded from his comparative anatomical
observations that there were three distinct olfactory centres. By
a series of careful anatomical observations, Golgi discovered thaL
the fibres of the olfactory tracts are in close relation with the
cells of the grey matter of the frontal lobes with which they
come in contact.
The localisation of the taste-centre is at present wholly
unknown. Flechsig supposes, without any convincing evidence,
that the sense of taste is connected with the anterior part of the
gyrus fornicatus. But his latest researches on myelination have
failed to confirm this hypothesis.
XIV. A glance at Figs. 304 and 305 (Flechsig), which repre-
sent the excitable areas of the cortex, shows that they extend over
about one-third of the surface of the human brain ; they are united
by projection fibres descending through the internal capsule with
the mid-brain and the bulbo-spinal axis, which constitute the
cortical sensory and motor centres. We are so far unable to
determine the specific function of the remaining two-thirds of the
cerebral cortex, which is termed latent because stimulation of it
gives rise to no reaction, and its excision to no permanent sensory
or motor disturbance. We only know that in man as well as in
animals extensive destruction of these inexcitable areas depresses
intellectual activity, proportionately with the extent of the lesion,
but similar effects occur after destruction of the excitable areas,
in addition to the sensory or motor paralysis or paresis.
Embryological observations, particularly the work of Flechsig
(1880-1904), have thrown much light on this difficult subject.
Flechsig' s method of studying the human brain during embryonic
development consists in ascertaining at what period different
bundles of fibres that make up the corona radiata, or the so-called
centrum ovale, acquire their myelin sheaths. The myelination
of any bundle of fibres is complete when the nerve elements which
it contains have reached their functional maturity. This maturity
is attained at different times by different bundles, which are
connected with different cortical fields. In order to bring out
the successive advance of myelination, Flechsig employed Weigert's
method, which stains all the myelinated fibres, but leaves the
non-myelinated fibres uncoloured. He found that in the human
hemisphere myelination begins at the fifth month of foetal life
and continues till the fourth month of extra-uterine life.
The law of myelogenesis as formulated by Flechsig assumes
that functionally equivalent fibres become myelinated, that is,
attain their maturity, simultaneously, and fibres of different
functional value become myelinated at different periods. So that
by studying its myelogenesis the brain may be divided into a
x THE FOEE-BKAIN 617
number of parts, each representing a special centre of psyc.ho-
physical activity, which are fairly easy to localise, although their
limits are not clearly marked, and overlap.
According to Flechsig the myelogenetic cortical fields may be
grouped either from their anatomical structure — i.e. as the pro-
jection or the association hi ires predominate they are either
sensory and motor centres, or association centres ; or from the
emhryological standpoint — i.e. from the date of their myelination
they may lie classed as primary, intermediary, and terminal regions.
Flechsig's sensory and motor centres which possess mainly
centripetal and centrifugal projection nitres, are those which we
have already discussed ; they are marked in Figs. 299, 300, by the
/ones of red dots. The association centres, in which the arcuate
fibres that unite different points on the cortex predominate over
the projection fibres, are contained in the pre-frontal, the extensive
temporo-parieto-occipital, and the insular regions (convolutions of
the island of Keil). As we have seen, Flechsig's association areas
include the whole of the inexcitable cortex.
In his latest embryological studies (1904) Flechsig divides the
cerebral cortex into thirty-six elementary myelogenetic fields.
The greater part of these medullary areas myelinate before birth,
and represent primary fields which are the most important
anatomically and physiologically, because the foetus at term
already receives stimuli from without, and is beginning to elaborate
them as the intellect develops. During the first month of extra-
uterine life — foetal post-maturity as it is termed by Flechsig — the
process of myelination extends to the intermediate fields. At the
commencement of the second month myelination of the terminal
fields sets in, and may be completed, as far as the main nerve-
fibres but not their collaterals are concerned, at the close of the
fourth month of extra-uterine life.
For this text-book Figs. 304, 305 will suffice to give an idea of
the final results reached 1 >y Flechsig in his division of the cerebral
cortex into thirty-six different areas of myelination ; the functional
significance of only a few has been determined.
Certain objections were raised against Flechsig's theory by
Dejerine, 0. Vogt, Sachs, v. Monakow, Hitzig and others, but these
have neither confuted the observations on which it is based nor
diminished its importance. Dejerine was the first to argue that
the whole of the cerebral cortex, including probably the island of
O JL i/
Reil, possesses projection fibres that pass through the capsule.
The projection fibres from the association centres seem, however,
to be few in number, and it has not been demonstrated that all
projection fibres subserve sensory and motor conduction : it may
be their function to associate the cortical fields with the sub-
cortical centres, since we have no ground for denying psychical
ideative functions to the latter, and for attributing these
618 PHYSIOLOGY CHAP.
exclusively to the cortex. Dejerine recognised that the pre-frontal
lobe, which represents an association area, contains a bundle of
projection fibres running to the thalamus, and particularly to its
nucleus interims. In the parietal lobe again, and especially in the
angular gyrus, there are, according to Dejerine, projection fibres
that run to the pulvinar and posterior part of the lateral nucleus
of the thalamus, which degenerate after lesions of those regions of
the cortex. These are projection fibres whose function is not to
conduct sensory and motor impulses, but to associate the cortical
with the sub-cortical psychical centres.
Monakow, on the other hand, observed that the sensory and
motor centres are also provided with association fibres, and indeed
contain more association than projection fibres. But even if we
accept the accuracy of this fact, which Flechsig denies, it does not
follow that the structural difference between the projection centres
and association centres is not sufficiently marked to enable them
to be readily distinguished and identified by simple embryological
features. There is, of course, no absolute difference between the
two classes of centres, but merely a relative and gradual difference.
It would be a mistake if the terms sensory and 'motor centres on
the one hand and purely psychical centres on the other were taken
to exclude all representative or ideative capacity from the former.
But it is only reasonable to suppose — at least it is a probable
hypothesis — that the latter have more important psychical functions
than the former.
This hypothesis appears to be supported by comparative
anatomy and physiology, which show that the surface of the in-
excitable association centres of the cerebral cortex increases
progressively in proportion as the intelligence of the animal rises.
In the lower mammals, as the rodents, there are no association
centres, and consequently the sensory and motor centres are in
contact ; in carnivora the association centres are little developed
and hard to identify by Flechsig's method ; they increase con-
siderably from the lower apes to the anthropoids; and finally in
man they extend over the greater part of the cerel >ral cortex.
If we study the chronological order in which the nerve-fibres
of the different cortical fields become myelinated, as shown in
Figs. 299, 300, we find another argument in support of the view
that the association centres have a higher psychical function than
the sensory and motor centres. Myelination in fact commences
with the ascending cortical afferent fibres which reach the
sensory areas of the cortex : next the cortico-motor bundles
descending from the motor cortical centres become myelinated;
and lastly the arcuate fibres, which serve to bring the different
cortical fields into inter -communication, obtain their myelin
sheaths. The association centres are ontogenetically the last
to attain anatomical maturity, for the very reason that they have
x THE FOEE-BEAIN 019
higher psychical functions, which develop later, even in the phylo-
genetic series.
We must now see if this finds much or little support from the
physiologist and the clinician. Of course there is no question of
discriminating any functional difference in the various areas of the,
cortex which mature at different periods of foetal development
and make up the so-called association centres : we are still far from
this even after Brodmaim's careful work on the structure of the
different parts of the cerehral cortex. It is only the psycho-
physiological importance of the association areas as a whole that
can he briefly indicated.
It has often been assumed, from Gall to the latest obseners,
that the frontal lobes, or at least their non-excitable or pre-frontal
portions, which attain a much higher development in man than
in the lower vertebrates, are the special seat of the intellectual
faculties. Leaving aside theoretical preconceptions and hypotheses,
no one who has been long occupied with the effects of partial
destruction of the brain in dogs or monkeys can fail to note the
insignificance and brief duration of the symptoms presented by
animals after removal of the pre-frontal lobes. Neither from
Munk's experiments nor our own, nor from those of Horsley and
Schafer, does it appear that after destruction of the pre-frontal
lobes the dog and the ape differ in any obvious way from intact
animals, in regard to their intelligence.
The alterations of character described by Goltz in animals
after removal of the front half of both hemispheres are very
striking: they lose the power of inhibiting their reflexes, they
become abnormally restless and uneasy, and though formerly
docile and affectionate, become intractable and ill-tempered. But
it is evident that most of these psychical changes are due to
destruction of the sensory-motor area, and that little can be
referred to the destruction of the pre-frontal region.
L. Bianchi, following on Hitzig and Wundt, maintained that
the frontal lobe is " the organ for the physiological fusion of all
the sensory and motor products elaborated in other regions of the
cortex — the organ of conscious synthesis of the. main factors of
mental life — the region in which are stored the greatest available
number of memory images, upon which the whole of the psychical
personality depends."
Physiological experiment, however, shows clearly that the
functions thus attributed to the pre-frontal lobe are not real. The
monkey deprived of pre-frontal lobes, which Bianchi showed at the
International Congress of Medicine in Eome, 1894, manifested no
perceptible mental alteration, in the opinion of the Committee
appointed to examine it. Horsley and Schafer frequently noted
that the pre-frontal region maybe removed without producing any
obvious symptom.
620
PHYSIOLOGY
CHAP.
Sciamanna's observations at the Clinic of Psychiatry in Rome,
are more interesting; in 1905, at the International Congress of
Psychology in Rome, he exhibited two monkeys (Macacus
cynomolgus), from which he had removed the pre-frontal lobes the
year In- lore.
Previous to the operation the animals had been under the
observation of Sciamanna and his assistants, who had studied their
habits and characters, the reactions they gave to various kinds of
Fin. :;or,. — A, <lia;;]arii <>t' visual sphere, which als {tends over to tli" cortex of the im-sial ami
inferioi surface, which is nut seen in the figure. B, anditoiy *]>II«TH of dog's cerebral cortex.
( I.M-iani.)
stimuli, the complex purposive acts which they performed, e.g.
feeling for sugar in the pocket of their keeper, looking at them-
selves in a mirror, etc. After recovering from the shock of the
operation, there was no appreciable change in their behaviour;
they continued to perform all the actions learned during the
period of observation, as before.
A committee consisting of Professors Fleehsig, Henschen and
Fano reported of these apes: There were no paretic or spastic
symptoms, and no exaggeration or defect in the usual motor
activity of the monkeys. They did not assume abnormal positions
during rest; their attention was attracted by any new object.
THE FOEE-BRAIN
621
They showed a lively interest in a mirror placed before them;
they were greedy for fruit and still more for sugar, which they
sought in the pocket where they had learned to tind it; they were
on good terms with their attendant, and behaved differently to
the people they knew and to strangers. If disturbed by threats
or noises they tried to escape as far as possible; but allowed
themselves to be touched and caressed; they never showed un-
reasonable fear or an^er.
Fie;. 307. — C, olfactory spln-rc ; D, .somo-urstln't ic "i M 'usury-motor spline of iln-'.s cerebral rm tex.
Diagrammatic. (Luciani.)
After killing both monkeys under chloroform, the Committee
examined their brains. It seemed at first as if but little of the
frontal lobes had been removed, but from an accurate report
published by Cerletti, the frontal pole, which is pronounced and
bulges forward in the macaque, was entirely absent, while the
rest of the pre-frontal lobe was occupied by cicatricial tissue, so
that in both monkeys the whole of the pre-frontal lobes had been
thrown out of function.
Clinical experience also militates against the theory which
ascribes special value in regard to mental functions to the pre-
frontal lobes. Many cases have been described in which lesions
of the anterior frontal region have not been accompanied
622 PHYSIOLOGY CHAP.
by psychical symptoms. Welt (1888) compared 59 cases of
different lesions of the frontal lobes: only in 12 cases was
there any mental disturbance or change of character. Recent
observations have contributed nothing in support of the old
.hypothesis that intelligence depends particularly upon the pre-
frontal lobes. Eoncoroni (1911), from a careful review of the
most recent clinical cases, concludes that lesions of the pre-frontal
lolies do not produce motor paralysis nor sensory alterations, the
most characteristic symptoms being impulsiveness or irritability,
a tendency to irrelevant witticisms, amnesia in regard to particular
words and acts, alterations in handwriting, apraxia, ataxy, and
alterations or loss of the power of performing certain voluntary
acts. The absence of sensory and motor symptoms with lesions
in the pre-frontal lobes agrees — according to Eoncoroni — both with
the experimental facts and with the cytotectonic observations of
Brodmann, as well as with the anatomical relations of the
pre-frontal lobe. Eoncoroni in conclusion declares against the
hypothesis that the highest intellectual faculties are located in
the pre-frontal lobes.
When, on the other hand, we consider Flechsig's great posterior
association area we see at once that both physiological evidence
and the facts of morphology and anthropology point to the special
importance of this region in mental functions.
Gk>ltz' experiments upon dugs in which the whole posterior
half of the hemispheres were removed are of great importance in
estimating the value of subsequent investigations. He saw that
dogs which were lively and active before this operation became
quiet and apathetic. Even more striking than this change of
character was the marked diminution of intelligence : the animals
behaved as if they were imbecile or demented.
We observed practically the same signs of grave mental
disturbance in dogs from which the whole cortex of the parietal
lobe, or the parieto-occipital, or the parieto-temporal region, was
removed. Removal of these regions leads to serious disturbance
of all sensory function, while lesions of no other part of the
cerebral cortex of the dog produce such complex effects, which of
course imply profound mental degradation.
On comparing the four diagrams representing the visual,
auditory, tactile, and gustatory spheres in the dog (Luciani and
Seppilli, Figs. 306, 307, A, B, C, D), it is at once evident that each
sensory sphere, besides its own area, overlaps and partially fuses
with those around it. This common area is the parietal lobe,
more precisely Munk's ^'sphere (Fig. 296), which we regarded as
the most important region of the dog's hemisphere, as the centre
of centres, on which the normal association of percepts and their
memory images depend.
The recent work of 0. Kalischer (1907) on the psychical
x THE FOEE-BEAIN 623
functions of the auditory and visual sphere of the dog, affords
new evidence -in support of this hypothesis. He educated certain
dogs to swallow pieces of meat only on hearing a given sound,
and not to touch them at sounds of a different pitch. These
animals retained the capacity for recognising the "dinner-sound"
even when the cortex of both temporal lobes had been destroyed.
This shows — according to Kalischer — that these complex reactions
(which certainly cannot be identified with simple reflex acts) may
take place in the absence of the sensory auditory area, provided
the subcortical auditory centres are present and are functionally
intact.
Kalischer taught other dogs to touch their food only in
brilliantly lighted surroundings, and not to take it in a dim light.
This habit was also preserved after removal of both occipital lobes
(Munk's visual sphere), proving, according to Kalischer, that the
power of recognising differences of luminous intensity does not
depend on integrity of Munk's cortical visual centres. On the
other hand, the power of recognising differences in colour depends
on the integrity of the cortical visual sphere. Kalischer showed
in a recent series of experiments (1909) that dogs that were
accustomed to take pieces of meat only when light of a given
colour, e.g. red, was let into the room, and not to touch them when
the light was a different colour, entirely lost the power for recog-
nising the " dinner-colour" after removal of both occipital lobes.
These ingenious experiments should be controlled. They do
not controvert the generally accepted theory that the highest
mental functions of perception, memory, association, are seated in
the sensory spheres of vision and hearing. They rather tend to
support the hypothesis that these spheres are not sharply limited
to the cortex of the temporal and occipital lobes, but extend
upward and forward towards the parietal lobe.
Experimenting with monkeys, Horsley and Schafer confirmed
the predominating importance of the posterior regions of the
hemispheres in relation to psychical functions. They stated that
a condition of idiocy was more readily produced in the ape by
removing extensive regions of the temporal lobes on both sides
than by cutting off the pre-frontal region completely by an incision.
The most striking evidence of the psychical importance of
Flechsig's posterior association area is, however, derived from
clinical and anthropological observations. Clinical data show
that external lesions of the cortex, particularly if bilateral, are
capable of producing mental disorders or diminution of intelligence,
whatever their situation. But it is a fact that the most common
and serious of such disorders depend on lesions localised in this
area. Failure of the ideative faculty, mental confusion, dementia-,
obvious symptoms of psychical blindness and deafness, are more
or less characteristic symptoms of bilateral destructive lesions of
624 PHYSIOLOGY CHAP.
the parietal, temporal, and occipital lobes. According- to Flechsig,
in fact, it is in this region that the greater part of man's intellectual
inheritance is stored up, and the visual, auditory, tactile, and
olfactory images associated into higher mental products.
R. Wagner concluded from his comparative anthropological
studies on the brains of highly intelligent persons, and of those of
mediocre or low intellect, that the degree of development of the
intellectual faculties depends on the wealth and depth of the
sulci, that is, on the surface area of the cerebral cortex, rather
than on the weight or total volume of the brain. This tends to
support the view that the intellectual faculties are not located
in any one part of the brain, but depend on the organ as a
whole, and develop in proportion with the grey matter of the
cortex.
But after a more minute analysis of the development of the
several regions of the cerebral cortex, Eiidinger (1882) noted the
important fact that the parietal convolutions are extraordinarily
well developed in men of high intelligence, as compared with
ordinary individuals and the lower human races. He was able to
obtain eighteen brains of people with different claims to eminence,
among them Dollinger, Bischoff, Lasaulx, and Liebig. In examin-
ing these he was specially struck by the exceptional development
of the convolutions and fissures of the parietal lobe, which gives
this region quite a different aspect from that of the brains of
uncultured persons. The study of the skulls of Kant, Gauss,
Dirichlet also showed marked development of the parietal region.
In the skulls of Bach and of Beethoven, which have been
studied by His and by Flechsig, there was a marked development
of the posterior regions of the brain (parieto-occipito-temporal)
and the Rolandic region, while the pre -frontal lobes were of
only comparatively insignificant dimensions. The brain of the
astronomer Gylden, examined by Eetzius, showed considerable
development of the parietal lobe, especially of the angular gyrus.
In Helmholtz' brain, according to Hansemann, the pre-cuneus
and parietal region included between the angular gyrus and
the upper temporal gyrus were remarkable in size. Eaffaelle's
cranium, studied by Mingazzini in an authentic chalk drawing at
Urbino, shows a striking contrast between the modest height of
the forehead and great expansion of the occipital and parietal
lobes. The skulls of Gauss and Richard Wagner, according to
His and Flechsig, on the contrary exhibit a striking development
not only of the posterior association area, but also of the anterior
or pre-frontal association area of Flechzig.
On the other hand, S. Sergi (junior), in a recent study of the
brain of the various human races (1909), has brought out the fact
that the development of the frontal lobe is not in ratio with the
degree of intellectual development, and that the highest races are
x THE FOKE-BEAIN 625
characterised by predominating development of the parietal and
occipital lobes.
XV. To form a more adequate idea of the complexity of the
intellectual processes, we may briefly examine the most typical
forms of disturbance of speech.
In a wide sense speech — or language — covers the sum of
all the means which man employs to express his thoughts.
Language is mimetic, phonetic, graphic (see Chap. III.), according
to the nature of the signs employed — gestures, words, writing.
Apart from mimetic language (which is the means of com-
munication for deaf-mutes, phonetic and graphic language have a
historical development in the race as in the individual. Com-
parative philologists endeavour to reconstruct the phylogenesis of
language ; psycho-physiological observations of the manner in
which the child learns gradually to speak, read, and write, reveal
the mode of development of language in the individual. Poverty
of language indicates poverty of ideas in primitive peoples as in
children ; wealth of language is the gauge of civilisation for the
most advanced nations, as for the most gifted and most highly
developed minds.
The spoken or written word is the symbolical representation of
the idea, which is necessary in order to express it, or communicate
it to others. The highest organs of ideation, while intimately
connected with, are entirely distinct and separate from, the organs
of speech. In fact, serious mental disturbance may coexist with
perfect integrity of phonetic and graphic speech. On the other
hand, psychological analysis and clinical observations show that
the mechanism by which ideas are clothed in verbal symbols is
very complex, and involves the intervention of three associated
centres : the centre for the motor images of words ; the centre for
phonetic verbal images ; the centre for visual verbal images. The
first (Fig. 308) is Broca's centre, which occupies the foot of the
left third frontal convolution ; the second is Wernicke's centre
seated in the left first temporal convolution and supramarginal
gyrus ; the third lies in the occipito-parietal lobe near the visual
area — according to Dejeriue it is placed in the left angular gyrus.
These three centres together form an area peculiar to the
human brain, the so-called speech centre, comparable to the
sensory-motor, visual, auditory and other areas which we have
been discussing. But unlike these the speech centre is single or
unilateral ; it lies in the left hemisphere in right-handed people,
in the right hemisphere in the left-handed. This asymmetrical
unilateral development of the central organs of speech is purely
functional and not morphological, for the right hemisphere presents
the same structure and connections as the left. The different
functional importance of the two hemispheres in speech evidently
depends on the larger and almost exclusive use which the right -
VOL. in 2 s
626
PHYSIOLOGY
CHAP.
handed make of the left brain, and the left-handed of the right
brain, during the years of education, in learning to speak, read,
write, and in performing finer and more skilled work. It is there-
fore reasonable, and well-confirmed by clinical evidence, that
lesions of the normal speech centres may be functionally com-
pensated by the symmetrical area of the opposite side. This
functional compensation or substitution is effected more readily
and completely in children than in adults. Gowers and
Mingazzini sustain that in the state of infancy the central speech
mechanisms are bilateral or at least more equally distributed
FIG. 308.— Area for speech and its three centres for verbal images. (Dejerine.) A, Wernicke's
centre, for auditory verbal images ; B, Broca's centre, for motor verbal images ; PC, centre for
visual verbal images.
between the two hemispheres than in adults. But in adults, too,
according to the consensus of clinical evidence, there must be
considerable difference in individuals ; Gowers, Brans, and Collier
state that in right-handed people the left hemisphere has no
monopoly in speech. Hughlings Jackson, Bastian, and Byrom
Bramwell, also on the strength of clinical observations, have
assigned the function of premeditated speech to the left hemi-
sphere and the simpler function of automatic speech to the right
hemisphere.
Severe lesions of Broca's convolution cause aphasia, that is
loss of the power of speech, owing not to paralysis of the nerves
and muscles thrown into action during phonation, but to abolition
of the memory of a certain order of co-ordinated movements
necessary to the articulation of words. The intelligence of the
x THE FOEE-BKAIN 627
patient remains intact ; he understands what is said or read to
him, and remembers what he previously learned. His vocal
organs are also normal, but he is unable to speak, though he can
sing vocally, laugh, and express emotions by his voice. His
auditory and verbal images are preserved, along with visual
images of objects and the images of written words. He can also
write intelligently when the lesion is limited to Broca's con-
volution, and mimetic language is perfectly retained. Sometimes
he continues the use of Yes and No and a few other words, as
exclamations. Under certain emotional conditions, but not
always at will, he is able to enunciate words — a proof that the
right hemisphere too is to some extent concerned with motor
speech, as maintained by Gowers.
Broca's theory has been attacked in recent years by P. Marie,
who declares that Broca's convolution does not take part in any
way in the complex function of speech. To support this he
invokes a large number of clinical cases of motor aphasia with all
the symptoms we have described, in wrhich a post-mortem examina-
tion showed the left third frontal convolution to be absolutely
intact. He also cited a second clinical series in which motor
aphasia was absent, while examination revealed isolated destruction
of Broca's lobule.
Marie's cases do not, however, invalidate Broca's theory. If
carefully considered, it will be found that they are not irreconcilable
with that theory, as was shown by Mingazzini (1908).
Clinical experience teaches that more or less transitory motor
aphasia may be due to the shock or disturbing effect of a focal
lesion which indirectly affects the function of the elements of
Broca's convolution. Mingazzini records a case, observed by
Panegrossi, of a patient affected with paralysis of the right arm,
who for several days entirely lost his speech, though able to under-
stand questions ; he only began to articulate certain words clearly
a few days before his death. The autopsy revealed a softening in
the middle part of the pre-central convolution, while Broca's
convolution was intact. The functions of the latter were evidently
affected solely by circulatory disturbances, and oedema due to the
haemorrhagic focus, which was beginning to subside shortly before
the patient's death.
In other cases the motor aphasia may be due to arteritis or
thrombosis of the arterial branches that supply Broca's con-
volution. In a case of right hemiplegia associated with motor
aphasia, Mingazzini and Marchiafava found on post-mortem
examination arteritis and partial thrombosis of the left Sylvian
artery, with an enormous red softening which involved the
lenticular nucleus, external capsule, and the pyramidal region of
the internal capsule, without disturbance of Broca's convolution on
either side.
628 PHYSIOLOGY CHAP.
It should be noted in conclusion that the post-mortem integrity
of Broca's organ in persons who had suffered from motor aphasia
may be more apparent than real, unless a careful microscopical
examination has been made. Marie's cases, in which there was
no motor aphasia despite destruction of Broca's convolution in
right-handed patients, are not irreconcilable with the generally
accepted theory, as slowly developing changes in the opercular
portion of the third left convolution may be associated with a
progressive functional development of the corresponding right con-
volution, which is the motor centre for articulate speech in left-
handed persons.
The fact that in young persons motor aphasia due to lesions
of Broca's centre quickly disappears was used by Mingazzini as
an argument in favour of Gowers' theory, which assumes that
up to a certain age both hemispheres co-operate in the formation
of the motor images of speech, and that the function of the right
brain is only later transferred to the left hemisphere in right-handed
people, and vice versa in the left-handed.
If we accept this hypothesis there is no difficulty in assuming
that in certain individuals, particularly in the ambidextrous,
the function of speech may be distributed throughout life
in an approximately equal degree to both hemispheres, so that
even a sudden lesion of one does not abolish speech (Mingazzini).
This theory, which invalidates Marie's arguments, is supported
by all the clinical cases of motor aphasia, due to destruction of
the left centre of Broca, in which speech gradually returns after
a longer or shorter interval. The following case reported by
Oppenheim (1909) is of great importance as a physiological
experiment on man. In a patient in whom Broca's centre had
been exposed, motor aphasia occurred each time the brain was
compressed, and disappeared when the pressure was removed.
Lesions of Wernicke's centre produce word deafness', those
of the cortex of the occipital lobe or angular gyrus word blindness.
The centres of auditory and visual word memory are not
equally important in the mechanism of speech ; obviously the
former preponderates. The child learns to speak by exercising its
auditory perceptions. As the association paths that connect the
auditory word centre with the motor word centre become developed
it makes its first attempts to talk, and speech gradually becomes
more perfect as the cortical and sub-cortical centres, and paths
and peripheral organs of speech, attain full development.
Lesions of the subcortical paths and peripheral organs produce
disturbance of articulation or dysarthria, but the capacity for
internal or mental speech then remains intact. Lesions of Broca's
and Wernicke's centres may produce alterations on the sensory
side of speech, and total or partial incapacity for phonetic
expression (aphasia or dyspliasia?) with more or less disturbance
x THE FOEE-BEAIN 629
of internal speech. "The auditory images," writes Dejerine, "are
the first to be formed ; they are the most deeply traced and always
control the processes of internal language; the motor images of
articulation next form very rapidly, and unite closely with the
auditory images. The union of these two contributes the first
and indispensable basis of internal language. At a much later
stage the child learns to attach the visual image of words to the
auditory and motor images of articulation. . . ."
In reading the child gradually learns to connect the sounds of
the words it already knows with graphic characters, the meaning
of which is at first unknown to it. At the same time or shortly
after, it learns to write, i.e. to reproduce written or printed
characters, which reinforces in its memory the intimate connection
between the phonetic images primarily acquired and the newly-
learned graphic images which correspond with them.
Hence in all who are able to read and write, the mechanism of
language is more complicated than in the uneducated. It depends
on the harmonised activity not only of the auditory and motor
word centres, but also of the visual word centre. But, in both
educated and uneducated, speech depends essentially upon the \
co-ordination of word sounds with word motor images ; verbal i
images, even in those whose visual memory is exceptionally
developed, only play a subordinate part in speech, in so far as
they are intimately connected with phonetic symbols. The
scientific proof of this lies in the fact that, while there are
numerous clinical cases in which word deafness, from lesions
confined to the auditory centre, is associated with loss or disturb-
ance of speech, i.e. with aphasia or dyspliasia — which Weruicke
terms sensory to distinguish it from the motor aphasia due to
destruction of Broca's centre — there are no cases on record of
word blindness due to lesions confined to the visual sphere, in
which the patient was incapable of speaking. Kussmaurs word
blindness is characterised by inability to read and write from
dictation, i.e. alexia and agraphia, and is not associated with
aphasia or dysphasia if the lesion is limited to the visual sphere.
This theory of the absolute functional preponderance of the
auditory centre in the mechanism of speech is at variance with
the view of Charcot, who classed individuals into auditive, visual,
and motor, according as they depended chiefly on the auditory
word centre, the visual word centre, or the motor word centre in
speech. But on Charcot's theory no one can be a visual who is
unable to read, and before learning to read it is necessary to
be an auditive. We must assume, in order to explain the
change into a visual, that the practice of reading intensifies
memory of written characters so much that it becomes easier to
evoke graphic images than verbal sounds.
It is more difficult, on this theory, to understand how auditives
\
630 PHYSIOLOGY CHAP.
can become motor, i.e. how speech, which was originally dependent
on the auditory word centre, is later, in certain individuals,
associated with the motor word centre, which may thus alone
subserve it. The motor word centre is so connected with the
auditory word centre that it is inconceivable that any separate
education can make it predominant over the latter.
Among the most characteristic forms of speech disturbance
due to lesions of the cerebral cortex, is that which has been well
described as verbal amnesia, since it is clinically quite distinct from
verbal deafness. In the one there is more or less complete loss of
memory of the auditory images of speech ; in the other it is
merely the power of recalling such images that has gone. While
the patient suffering from word deafness cannot understand spoken
language and is incapable of speaking, the patient with verbal
amnesia understands perfectly, and without hesitation, whatever
is said to him ; and he can pronounce every word easily ; but his
speech is more or less hesitating and unintelligible, as he cannot
recall a large number of words, particularly proper names and
substantives. " The idea is there, but the word fails, although
articulation is not defective " (Kussmaul). " The idea does not
call up the word, but the word can always reawaken the idea, for
the patient can repeat and understand the word which is suggested
to him, and which corresponds with the idea he wants to express "
(Tamburini). The auditory and motor word centres are capable
of reacting to the external stimuli, but have become incapable of
reacting to the internal stimuli of ideational activity.
Many authors have confused amnesia with word deafness, and
maintain that they differ only in degree. It is true that word
deafness necessarily involves amnesia ; but their co-existence is
not absolutely inevitable, for verbal amnesia may be present
without a trace of word deafness.
Even if both forms imply a lesion of the auditory area,
pathological anatomy proves their different localisation. In cases
of pure verbal amnesia Wernicke's centre, i.e. the posterior part
of the left first temporal convolution, is not involved, but only the
left inferior parietal lobe, as was seen in typical cases described
by Banti, Cornil, Kussmaul, Broadbent, and others.
XVI. The new and fundamental principle which Flechsig
introduced into the physiology of the brain consists essentially, in
the distinction which he made between the sensory and voluntary
motor centres, which are united by afferent and efferent fibres
with the peripheral sensory and motor organs, and the psychical
centres properly so-called, which are connected by endogenous or
intra- central association fibres among themselves and with the
different sensory centres. According to Meynert and Weruicke
the " sensory spheres " included the whole of the cerebral cortex ;
each of them was connected with the rest by endogenous, and
x THE FOBE-BBAIN 631
with the periphery by exogenous fibres. Their functional synergy
depended on the central continence of these sensory spheres, which
rendered the cerebrum the single organ of intelligence. Munk's
general hypothesis of the psycho-physiological functions of the
brain is based upon this schema of Meynert and Wernicke.
According to our own theory, which is based on experimental
work on dogs, the several sensory centres overlap in a common
area to which we gave the name of " centre of centres." Flechsig,
too, admits that there is no absolute line of demarcation between
his cortical projection fields, which include the sensory and motor
areas, and the association jields. Between the one and the other
Flechsig sees the same relations as exist between sensibility and
intelligence " which, while theoretically separable, are really
intimately associated." Niliil est in intellectu quia prius fuerit in
sensibus. Without the sensory centres, the intellectual centres
would be ab initio incapable of producing ideas or representations ;
1 H ith normally act and react together, work for the same ends, and
aim at the same results. The material supplied by the sensations
is, so to speak, elaborated in the intellectual centres. The
functions of the one represent the receptive phase, those of the
other the reactive phase of the mental process. The former (to
adopt the classical language of Aristotle) constitute the passive
intellect, the latter the active intellect.
It was the clinicians — arguing from the symptoms of aphasia
—who first postulated the existence of an ideational centre in the
cortex distinct from the centres for verbal images (auditory, visual,
articulative). The fact that there may be total loss of the use of
words with no apparent disturbance of intelligence is the most
cogent argument that the word and the idea are formed in-
dependently of one another, in different areas of the cerebral
cortex. But it was only from the studies of Flechsig that this
hypothetical ideational centre acquired a localisation, though still
indefinite and vague. It is evident that it must lie in the associa-
tion fields, more particularly in those contained within the parieto-
occipito-temporal area of Flechsig.
The distinction between sensory -motor and psychical areas of
the cortex is intimately connected with an important question
of the general theory of Memory. Is the seat of primary precepts
or sensory images identical with or different from that of the
secondary representations or the secondary sensory images, evoked
by a simple effort of memory ? If the first hypothesis, which has
been formulated by Bibot and other psychologists, and accepted
unconditionally by physiologists and clinicians, be admitted it
follows that the sensory centres on which perception of the
external world depends are at the same time the seat at which the
memory images must be formed and stored up, but we are unable
to picture or to comprehend their nature. If we accept the second
632 PHYSIOLOGY CHAP.
alternative, we must assume that " the sensory and motor centres
serve only for immediate and ever new reactions, of which they
preserve no impressions — that the enduring or incomplete memory
of events which affect the projection centres are stored up in
other centres — that the images of things are perceived at, one point
and retained at another . . ." (Tanzi).
This hypothesis seems to us to be an arbitrary interpretation
of Flechsig's theory. Prior to the distinction of the cerebral
cortex into projection fields and association fields, when the brain
was simply held divisible into sensory and motor spheres, it was
natural to assume that the memory of sense impressions was
distributed all over the cerebral cortex. That the association
fields are the exclusive seat of memory, and that the projection
fields which are in the most immediate connection with the
peripheral sense organs are incapable of preserving the impressions
and percepts, is a necessary consequence of Flechsig's theory.
The occurrence of blindness of cortical origin without loss of
the power of evoking visual images, does not prove (as stated by
Tanzi) that the centre of visual memory is distinct and separate
from the area of visual sensibility. When we consider that visual
memory may theoretically be divided into functionally distinct
components, as the special memories of luminosity, colour, form,
dimensions, etc., it seems legitimate to assume that the lesions
which produce cortical blindness do not destroy the whole visual
fields, and do not therefore blot out the whole of the visual
memory stored in the cortex.
No argument in fact prevents us from assuming that all
cortical areas, not excluding those in most intimate relation with
the peripheral sense organs, are the seat of special memories and
contain the traces of previous percepts and representations; that
these impressions, organically distributed over countless elements,
are in more or less close inter-relationship, and are capable of
associating or combining in a thousand different ways.
This theory of memory agrees perfectly with the results of
psychological analysis of perceptions in contrast to simple
sensations ; a perception results from the synthesis of a sensory
image with the mnemonic traces left by preceding sensations. The
sensory centres of the cortex which are the seat of perception are
accordingly capable of retaining memory impressions.
On the other hand there can be no doubt that the greater
number of the nerve elements concerned with memory must be
sought in the association areas of the cortex. The physiological
proof of this is the amnesia of varying kind and degree produced
by alterations of these areas. The psychological proof lies in
the analysis of representations, in so far as these result from
association of the multiple and varied memory images which arise
in distant and distinct areas of the cortex.
x THE FOKE-BKAIN 633
In considering the theory of memory, it is important to
determine what are the stimuli which are able to revive the
memories retained in the ganglion cells of the cortex and to re-
invoke the images in the form of representations. In this psycho-
physiological process special importance is usually ascribed to
internal stimuli, which act upon the sensory organs, constantly
excite memories, and bring all the latent energies of the mind into
play. But internal stimuli coming from the vegetative organs
through the sympathetic system to the cerebral cortex, where they
excite bodily sensations and instincts in consciousness, must be
of almost equal importance to mental activity. The brain is
consequently the meeting-place for impressions from the outer
world and for those that originate within the organism. Both these
channels excite the psychical centres centripetally and the motor
system ceutrifugally.
The association between the sense centres and those of instinct
give an emotional tone to the perceptions, and thereby increase
their dynamic efficiency. The associations between the exterior
and interior sensory centres and the psychical areas proper
serve the idealisation of the images and determine the exchange of
action and reaction between the sensations and instinct, and the
intellect. It is in the struggle between impulse and inhibition
that actions acquire an ethical character. The greater the
functional energy, and the more perfect the inhibition and control,
so much the more will reason prevail over emotion.
By its investigations into the material conditions of human
activity, physiology allies itself with the moral sciences. In the
twentieth century it will pursue the scientific analysis of psycho-
physical phenomena without preconception or prejudice. It will
not be hampered as in the past by animus to the concept of
the soul, nor, on the other hand, will it fail to recognise that
psychical development, even on the ethical side, depends to a
large extent upon the somatic substrate.
The more science succeeds in revealing the nature of life in
general, and of the human mind in particular, the stronger and
clearer will be our scientific faith that behind this world of
appearances there lies a world of reality, in comparison with
which human consciousness and human knowledge • are but as a
shadow.
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INDEX OF SUBJECTS
Abducent nerve, 411
Absinthe, convulsions, 581
Absolute force, muscle, 47
Acetabulum, 100
Acid, carbolic, v. Phenol
carbonic, v. Carbon dioxide
lactic, muscle, 38, 39
uric, muscle, 38
Acids, nerve stimuli, 220
Acoustic nerve, roots, 406
Action current, muscle, 77
nerve, 210
Activity, muscular, 84
neural, 254
Aeroplane, centre of gravity, 126
Aesthesodic nerve fibres, 256
Agenesis, cerebellum, 455
nerve cells, 330
Agraphia, 629
Ala cinerea, vagus, 393
Alcohol, gait, 450
Alexia, 629
" All or nothing " heart, 13
reflexes, 317
Allocheira, spinal hemisection, 347
Amblyopia, quadrigeminal lesion, 516
thalamic lesion, 522
Ammonia, nerve, 220
Amnesia, 630
Amphiarthroses, 99
Amphioxus, brain, 380
sinus ovalis, 494
"spinal mind," 341
Anabolic nerves, 82
Anabolism, protein, 45
Anaesthesia, 417
Anaesthesia dolorosa, 202
Anaesthetics, convulsions, 579
knee-jerk, 329
nerve, 211, 212
spinal cord, 323
Anelectrotonic current, 242
Anencephaly, 509, 510
Anisotropy, muscle, 27
Anodonta, nerve conduction, 205
Ano-spinal centre, 352
Ansa peduncularis, 492
Antagonism, muscle, 35
Anthropoids, cortical localisation, 554
Ape, cerebellar ablation, 444
Aphasia, 544, 545, 612, 626
Aphonia, 140
Aplysia, oesophageal rhythm, 32
Aqueduct, of Sylvius, 488
Arachnoid, 531
Arbeitssammler, 65, 66
Area, auditory, 592, 610
calcarine, 602
gustatory, 613, 616
motor, 594
olfactory, 527, 613
sensory-motor, 592
striata, 602, 603, 604
dog, 604
monkey, 607
visual, 592, 599, 606
Areas, architectural, cerebrum, 536, 540
association, 592, 616, 618, 632
hyperalgesic, 308
projection, 592
Arm, movements, 104
Arsenic, ganglion cells, 184
Arthroses, 99
Articulation, 155
Articulations (joints), 99
Ash, muscle, 41
Asphyxia, nerve, 231
nerve centres, 267, 270
Association centres, 592, 616, 618, 632
Association fibres, cerebrum, 532
Astasia, cerebellar, 444
Asthenia, cerebellar, 442
Asynergy, cerebellar, 470
Ataxy, cerebellar, 432, 437
spinal, 298
tabetic, 469
Atony, cerebellar, 443
spinal, 300
Atrophy, cerebellum, 455
Auditory area, dog, 611, 620
man, 612
monkey, 610, 612
nerve, 405
Aura, epileptic, 576
637
638
PHYSIOLOGY
Auricle, oscillations of tonus, 32
Autonomic nervous system, 359
Autotoniy, 336
Avalanche theory, 224
Axis-cylinder, 179
Axon, 179
reflexes, 374
Balmung, 259
Barium salts, nerve, 219
Bibliography, bulb, 417
cerebellum, 484
cerebral localisation, 633
locomotion, 127
mid -brain, 524
muscle, 94
nerve, 276
nervous system, 275
spinal cord, 356
.sympathetic system, 378
voice, 173
Bird, decerebrate, 500
Blindness, cortical and psychical, 599
Blood-vessels, afferent nerves, 372
Bones, mechanics, 97, 103
Brain, amphibia, 497
Amphioxus, 495
bibliography, 634
corvina nigra, 529
development, 380
embryo, 527
fish, 528
foetal, 382
membranes, 531
psychical functions, 543
Scyllium canicula, 496
inhibition of spinal reflexes, 319
Squalius cephalus, 496
teleosteau, and human, 529
tortoise, 500
Brain-stem, transection, 517
Bromides, epilepsy, 579
Bulb, 380 et seq.
consciousness, 416
convulsions, 581
grey matter, 386
olfactory, 527
phenol, 415
posture, 414
sensory centres, 415, 416
spinal reflexes, 325
strychnine, 415
Bundle, dorsal longitudinal, 487
macular, 493
Caesium salts, nerve, 219
Calamus scriptorius, 389
Calcarine area, vision, 602
Calcium salts, nerve, 219
nerve centres, 275
Calomel, electrode, 72
Caloric yield, muscle, 67
Canaliculi, neural, 186
Canals, semicircular, 461 ct scq.
Capillary electrometer, 72
Capsule, internal, 530, 594
Carbon dioxide, muscle, 41
nerve, 228
Carcinus maenas, unipolar neurone, 260
Cardio-accelerator centres, spinal, 353
Cardiogram, 80
Carnine, muscle, 38
Cartilages, laryngeal, 133
Cassida equestris, muscle, 29
Catalepsy, mid-brain lesion, 518
Catgut, contraction, 90
Cauda equina, 280
Caudate nucleus, 529, 596
Cells, nerve, 176, 178
Centre, ano-spinal, 352
cardio-accelerator, 353
cilio-spinal, 352
convulsaut, 412
ideational, 631
of centres, 622, 631
of gravity, 109, 126
phonation, 143
speech, 545, 625
vesico-spinal, 352
Centres, association, 592, 616, 618, 632
bulbar, 412
centre of, 622, 631
cerebellar, 474, 476
cortical, 538 et seq.
cortical inhibitory, 565, 566
laryngeal, 142
phonation, 143, 553
projection, 592
psychical, 616
respiratory, 352, 412
secretory, bulbar, 405
cortical, 574
spinal, 352
thalamic visual, 521
Centrum ovale, excitation, 561
Cephalopoda, velocity of nerve impulse,
204
Cercopithecus, cortex cerebri, 551
Cerebellar, asynergy, 470
ataxy, 437, 450, 458, 465
centres, 474
cortex, 182
deficiency, 442
disease, 455 et scq.
dysmetria, 450, 460, 470
gait, 449
lesions, 431 et seq.
localisation, 474, 479
peduncles, 388, 419, 425, 427, 428
tracts, 288, 428
vertigo, 435, 436
Cerebellum, 419-484
agenesis, 455
astasia, asthenia, atonia, 442, 443,
444
atrophy, 455
INDEX OF SUBJECTS
G39
Cerebellum, bibliography, 484
co-ordination, 406
curare, 4:.!f», 436, 476
disease, 4f>f> ft w//.
equilibration, 461
excitation, 435
i'oived inoveinents, 432
functions, 430, 461
lien's jf ait, 450
labyrinth, 461
lesions, 431 ct seq.
man, 458
lobes, 421
lobules, 479
localisation, 474
muscular sense, 446, 467
nuclei, 425
olivary connexions, 387, 428
ontogeny, 473
orientation, 466
phenol, 477
phylogeny, 473
reinforcement, 483
sense organs, 473
static function, 471
sthenic function, 468, 471
structure, 424
strychnine, 477
surface, 422
tactile and muscular sense, 446
tonic function, 471
tracts from cord, 428
tract to cord, 429, 430
trophic function, 472
tumours, 457
uncrossed connexions, 478
Cerebral gyri and sulci, 531 '
hemispheres, 531
localisation, 538 ct seq.
bibliography, 633
vesicles, 380
Cerebrospiual fluid, 281
preparation, 272, 273
Cerebrum, 526 et seq.
abdominale, 373
anatomy, 526
area striata, 602, 603, 604, 607
association areas, 592, 616, 618, 632
auditory area, 592, 610
Brodmann's areas, 533, 536, 540, 594
calcarine area, 602
cerebellar lesion, 435, 441, 481, 483
cortex, 531 et seq.
cyto-architectural areas, 536, 540
gustatory area, 613
lesions, 581 et seq.
motor areas, 546 ct seq.
muscular sense, 582
myelination, 614, 616
olfactory area, 527, 613
projection areas, 592
sensory-motor area, 592
visual area, 592, 599, 606
Ghost register, 150
Chiasma, optic, 492
Chimpanzee, cortical localisation, 555
Chorda tympani, taste, 403
Chordograms, 91, 92
Chloral, cortex cerebri, 561, 570
Chromatolysis, 268
Ciliary ganglion, 375
Cilio-spinal centre, 352
nerves, 366
Cinchonidiiie ("quinine"), 579
Circulation, cortex, 571
Circus movements, quadrigeminal lesion,
517
Clavae, bulb, 385
Clot, muscle, 36, 37
Cocaine, muscle, 87
Coccygeal ganglion, 360
Cochlear nerve, 405
Collateral ganglia, 360
Collaterals, 177, 285
Column of Burdach, 288
of Clarke, 283
of Goll, 288
of Tiirck, 287
Comniissural fibres, cerebrum, 532
Commissure, Guddeu's, 493
optic, 492
Compensation, cerebellar lesions, 439,
448, 452
Conduction, nerve, 192 et seq.
spinal ganglion, 261
spinal reflexes, 314
Consciousness, bulbo-pontine, 415
decerebrate, 511
spinal, 337
Consonants, 155, 164, 167
Constant current, peripolar effects, 251
polar effects, 245, 251
Contraction, catgut, 90
idio-muscular, 5, 24
muscle, 7
mechanism, 85
secondary, 77
Pfliiger's law, 25, 248, 251
surface tension, 94
Contraction wave, muscle, 21, 23, 28,
29
Contracture, muscle, 31, 33, 50
Conus medullaris, 281
Convulsions, absinthe, 581
anaesthetics, 579
bulbar centre, 412
Co-ordination, cerebellum, 466
reflexes, 320
sympathetic, 377
Cords, vocal, 135
Core models, nerve, 243, 257
Cornea, Gasserian ganglion, 331
Corpora bigemina, 489
lesion, 516
geniculata, 491
quadrigemina, 488, 513, 515
640
PHYSIOLOGY
Corpora quadrigemina, lesion, 516
striata, functions, 594
Corpus callosum, 530
epilepsy, 580
vision, 602
striatum, body-temperature, 597
development, 528
functions, 595 et seq.
nuclei, 529
Cortex cerebelli, 182
cerebri, association areas, 592, 616,
618, 632
Brodmann's areas, 533 ct seq.
cells, 534
centre of centres, 622
cercopithecus, 551
chemical excitation, 550
chloral, 561, 570
ciuchonidine, 579
circulation, 571
contracture, 590
curare, 552
cytotectonic types, 536 et seq.
excitable area, man, 559
excitation, 560
Flechsig's centres, 630
frontal lobe, 619
inhibition, 565
kidney, 572
mechanical excitation, 550
motor areas, 546 et seq.
phenol, 552
picrotoxin, 551, 579
projection areas, 592
reflexes, 583
rhythm, 562, 564
schema, 539
sensation, 582
sensory-motor areas, 581 et seq.
spinal reflexes, 319
strychnine, 264, 551
viscera, 570
vision, 599
Cortical blindness, dog, 599
centres, 538 et seq.
dog, 548
macacus, 552
orang, 556
phonation, 143
deafness, 611
epilepsy, 574
latency, 561
lesions, 581 et seq.
dog, 585
man, 590
monkey, 586
sensation, 582, 587
localisation, 538 et seq.
anthropoids, 554
dog, 547
man, 557
monkey, 553
orang, 554
Corvina nigra, brain, 529
Crab claw, muscle, 35
Cranial autonomic system, 361
nerves, 388 et seq.
nuclei, 390
Craniota, 380
Creatine, muscle, 38
Creatiniue, muscle, 38
Crest, neural, nerve development, 236
Crura cerebelli, 388, 425, 427, 487
cerebi'i, 486
Curare, caudate nucleus, 597
cerebellum, 435, 436, 476
cortex cerebri, 552
muscle, 4
nerve-endings, 200
Current, axial, nerve, 210
demarcation, muscle, 75
nerve, 209
of action, muscle, 77
nerve, 210, 215
of injury, muscle, 76
nerve, 209, 215
of rest, muscle, 69, 73
nerve, 208
Currents, electrotonic, 242 et seq.
post-electrotonic, 244
thermal, 76
Curvature, vertebral column, 112
Cytotectonics, brain, 536 et seq.
Deafness, cortical and psychical, 611
Decerebrate bird, 500
dog, 506, 509
fish, 496
frog, 497, 498
monkey, 510
rabbit, 505
rigidity, 518
tortoise, 499
Decussation, bul bo-spinal, 342, 343
optic, 493
Degeneration, chromatolytic, 268
nerve, 232
spinal, 286 et seq., 347
Deglutition, centre, 553
Demarcation current, muscle, 75
nerve, 208
positive variation, 82
Dementia, 510
Dendrites, 179
Dermatomeres, 279
Dermatomes, 303, 306
Dextrin, muscle, 38
Dextrose, muscle, 38
Diarthroses, 99
Digitaline, muscle, 87
Diphasic variation, muscle, 79
nerve, 216
Diphthongs, 170
Dog, auditory area, 611
motor area, 547
olfactory area, 613, 614
INDEX OF SUBJECTS
641
Dog, visual area, 509
Dorsal longitudinal bundle, 487
Dura mater, 281, 531
Dynamic phenomena, cerebellar, 432,
433, 437
Dynamograph, 47
Dynamometer, 47
Dysarthria and dysphasia, 628
Dysbasia, 460
Dysmetria, 298, 450, 460, 470
Dysphasia and dysarthria, 628
Dyspnoea, vagotomy, 399
Dystasia, 460
Dystrophy, isolation, 312
nerve section, 333
Ego, divisibility, 338
Elasticity, muscle, 85
Electrical stimuli, 222
Electrocardiogram, 82
vagus, 83
Electrodes, calomel, 72
uonpolarisable, 71
polarisation, 241
Electrometer, capillary, 72
Electrophysiology, muscle, 68 ct scq.
nerve, 208 ct scq.
Electrotonic currents, ether, 244
excitability, 244
Electrotonus, 240
Eledone, nerve, 216
Embrace reflex, 311, 512
Embryo brain, 527
Emys Europaea, auricular tonus, 32
brain, 500
palustris, reflexes, 324
Energy, kinetic, muscle, 45
source of muscular, 42
Epiglottis, 134
Epilepsy, 574
bibliography, 635
body temperature, 576
bromides, 579
corpus callosum, 580
subcortical factors, 577
tonus and clonus, 577
Equilibration, cerebellum, 461
posture, 110
Erect posture, 111
Ergograms, 49
Ergograph, 48, 57
Eunuch, voice, 148
Excitability, electrotonic, 245
muscle, 3
nerve, 224
post-electrotonic, 245
Excitation, high frequency, 19
law of, 223
Excito-motor system, 341
Expression, 130
Extractives, muscle, 38
Eye, extirpation, visual cortex, 603
VOL. Ill
Facial nerve, 406
distribution, 407
function, 408
Facilitation, 259
Falsetto register, 151
Fascia dentata, 181
Fat, in muscle, 40
Fatigue, central, 51, 271
fasting, 56
food, 51
in vivo, 49
mental and muscular, 50
muscle, 38, 48, 53, 59
factors, 59
temperature, 11
nerve, 207, 225
peripheral, 51
practice, 56
recovery, 53
spinal, 50
Femur, mechanics, 98
Fibrin, proteolytic products, 45
Fillet, bulb, 385
mid-brain, 487
optic thalami, 521
Fish, decerebrate, 496
hearing, 406
Foot, mechanics, 112
Force,' absolute, 47
Forced movements, 432 ct seq.
Fore-brain, development, 526
Formant tone, 162
Formatio reticularis, 388, 413
Fractional heat coagulation, muscle, 37
Frog, balancing, 498, 499
decerebrate, 497
Frontal lobe, 619
intellect, 624
man, 622
Funiculus cuneatus, 288
gracilis, 288
Gait, cerebellar, dog, 438, 449, 451
man, 458
monkey, 451
man, alcohol, 450
Galvanometer, mirror, 70
string, 73
Galvanotonus, 251, 253
Ganglia, basal, 528
glossopharyngeal, 401
spinal, 261, 284
sympathetic, 360 et seq.
vagal, 393, 396
Gangliated plexuses, 378
Ganglion cells, 180
function, 260
Ganglion, ciliary, 375
coccygeal, 360
Gasserian, 331, 409
inferior mesenteric, 370
Meckel's, 409
nodosum, 396
2T
642
PHYSIOLOGY
Ganglion, petrosal, 401
reflexes, 373
solar, 373
sphenopalatine, 403
spiral, 405
stellate, nicotine, 368
stellatum, cephalopoda, strychnine
and phenol, 264
superior cervical, branches, 363
nicotine, 368
Gas chamber, 231, 232
Gases, muscle, 41
Gasserian ganglion, 331, 409
Gemmules, 179
Genito-spinal centres, 352
Glossopharyngeal nerve, 401
functions, 404
motor fibres, 405
salivation, 405
section, 404
taste, 401
Glottis, 135 et seq.
phonation, 144
spinal accessory, 394
Glycerol, nerve, 219
Glycocoll, muscle, 38
Glycogen, inanition, 39
muscle, 38, 39
Gorilla, cortical localisation, 555 '
Gravity, centre of, 107
Grey matter, excitability, 262
post-mortem acidification, 270
summation, 262
rami, 372
Gustatory area, 613, 616
Harmonics, 131
Hearing, cerebrum, 592, 610
fish, 406
quadrigeminal lesion, 516
Heart, cortex cerebri, 573
equipoteutial lines, 81
positive variation, 82
voluntary acceleration, 573
Heat, effect on muscle, 10, 18, 76
nerve, 211, 218
production, muscle, 59 ct seq.
nerve, 207
Hebphanomen, 298, 299
Hemianaesthesia, man, 592
Hemianopsia, 522, 599, 601, 608
Hemiplegia, 342, 581, 592
Hemisection, spinal cord, 344
Hind-brain, 419-485
Hippocampus, 614
Horizontal posture, 110
Hyperaesthesia, cortical lesion, 582
spinal lesion, 341
Hyperalgesia, cutaneous, 308
Hypnosis, decerebration, 518
Hypogastric nerve, 373
Hypoglossal nerve, dorsal root, 389
functions, 390
Hypoglossal nerve, origin, 389
paralysis, 392
recurrent sensibility, 392
Hypoxanthine, muscle, 38
Ideational centre, 631
Idio-muscular contraction, 5
Inanition, muscular metabolism, 38
nerve-centres, 269
Inductorium, 221
Infancy, speech centres, 626
Inhibition, cortical, 565
skeletal muscle, 35
spinal, 319
temperature, 35
Injury current, muscle, 76
nerve, 208, 215
Innervation, larynx, 140, 394
limbs, 305
muscles, 303
overlap, 305
pharynx, 397
reciprocal, 320
skin, 300 et seq.
Inogenetics, muscle, 93
Inosite, muscle, 38
Inotagmata, 90
Insertion, muscles, 105
Intellect, active and passive, 630
parietal gyri, 624
sulci, 624
Intermediolateral tract, 367
Internal capsule, 530, 594
Intoxication, fatigue, 59
Iron, muscle, 41
Irradiation, reflexes, 315
Island of Reil, 555
Isometry, muscle, 14
Isotony, muscle, 14
Joints, 99-102
Katabolic nerves, 82
Katelectrotonic current, 242
Kidney, cortex cerebri, 572
Kinesodic nerve-fibres, 256
Kinetic energy, muscle, 45
Knee-jerk, 326
cerebellar disease, 459
conditions, 329
decapitation, 329
latency, 327
nervous mechanism, 330
reinforcement, 330
sleep, 329
spinal disease, 329
transection, 329
Labyrinth, lesions, 299, 406
tonus, 464, 466
Lactic acid, muscle, 38, 39
INDEX OF SUBJECTS
643
Language, cortical mechanism, 625
evolution, 172
peripheral mechanism, 129
written, 172
Laryngeal cartilages, 133, 134
ligaments, 134
muscles, 136
nerves, 14CL394
centres, 142
origin, 395
respiration, 141
Laryngoscope, 145
Larynx, 1 33 et scq.
innervation, 394
mechanics, 143
spinal accessory, 394
vagotomy, 399
Latency, cortical, 561
electrotonic, 246
knee-jerk, 327
muscle, 8, 9
Lateral ganglia, 360
ventricles, 490
Law, Bell-Magendie, 292
myelogenetic, 616
of contractions, 25, 248
of nerve conduction, 197
of reflexes, Pfliiger, 314
Ritter-Valli, 232
Lecithin, muscle, 40
Lenticular nucleus, 596
Levers, bones, 103
Life, internal and external, 1
Ligaments, 99, 101
Limbs, centres, 352
metamerism, 305
trophic nerves, 332
Lingual nerve, 373
Load, muscle twitch, 13
Lobe, frontal, 619
occipital, 599, 606
olfactory, 528
parietal, 624
temporal, 610
Lobule, olfactory, 527
Lobules, of cerebellum, 479
Localisation, cerebellum, 474, 479
cerebrum, 538 et seq.
Locomotion, 96-128
bibliography, 127
chronophotograms, 116, 117, 118
gait, 126
galloping, 124
jumping, 124
mechanics, 97
oscillations, 121
pace, 118
pressure, 119
swimming, 125
walking, 114
curves, 116
work, 97
Lumbricus, neurofibrils, 185
Macula lutea, visual area, 609
Malapterurus, velocity of nerve impulse,
204
Maltose, muscle, 38
Man, auditory area, 612
motor area, 559
smell, 615
visual area, 607
Mass, centre of, 107
Masticatory nerve, 410
Maximum work, 52
Mechanical stimuli, 220
Mechanics, bones, 97
foot, 112
larynx, 143
muscles, 102
posture, 107
vertebral column, 111
Medulla oblongata, 380-418
bibliography, 417
centres, 412
posture, 414
spinal reflexes, 325
tracts, 383
Membranes, brain, 531
spinal cord, 281
Memory, 340, 509, 545, 599, 631
unconscious, 341
verbal, 630
Mesencephalon, 381, 486-525
development, 486
excitation, 512
lesions, 494 et seq.
spinal reflexes, 319
Metameres, Amphioxus, 495
Metamerism, bibliography, 356
limbs, 305
trunk, 301, 303
Metencephalon, 381
Microcephaly, 510
Micturition, inhibition, 319
Mid-brain, 486
ablation, fish, 497
frog, 498
toad, 499
bibliography, 524
hemisection, 518
lesion, rabbit, 505
tortoise, 500
tortoise, 500
Moments, muscular, 105, 106
Monkey, area striata, 607
auditory area, 610
motor area, 552 et scq.
olfactory area, 613
visual area, 606
Muscle, 1-95
absolute force, 47
acidity, 40, 41
action current, 77
activity, lactic acid, 39
Amici's line, 27
anisotropy, 27
644
PHYSIOLOGY
Muscle, ash, 41
bibliography, 94
chemical energy, 88
chemistry, 36
circulation, 5
clot, 36
Cohnheim's areas, 26
contraction, 7 et seq.
optical changes, 28
contracture, 31
curare, 4
current of action, 77
of rest, 69, 73
diphasic variation, 79
discs, 91
disuse, 6
efficiency, 67
elasticity, 85
fatigue, 87
poisons, 87
electrical wave, 93
electro-physiology, 68
energy, 42, 93
excitability, 3
extractives, 38
fatigue, 48, 52
temperature, 11
fats, 40
fibres, 26
fibrils, 27
fixed contraction wave, 28
fractional heat coagulation, 37
galvauogram, 78
gases, 41
heat, production, 59
tension, 65
fatigue, 65
histology, 2, 25
inhibition, 35
injury current, 76
inogenesis, 93
intensity of stimulus, 13
isotony and isometry, 14
kinetic energy, 45
Krause's membrane, 27
latency, 8, 9
of inhibition, 36
load, 53
mechanical work, 46
mechanism of activity, 84
metabolism, nitrogenous, 42
starvation, 38
work, 39, 40
nuclei, 25
optical properties, 27
phosphates, 39
pigments, 38
plasma, 36
proteins, 37
proteogenesis, 45
proteolysis, 44
proteose, 37
quick and sluggish fibres, 10
Muscle reaction, 39, 40
recovery, 12
red and pale, 9, 24
relaxation, 14, 30, 88
respiration, 42
rigor mortis, 36
salts, 41
sarcolemma, 25 ,
sarcomeres, 27
sarcoplasm, 26
secondary contraction, 77
serum, 36
simple twitch, 8
sound, 19, 31
staircase contraction, 11
survival, 5
tension, 30
tetanus, 33
thermal currents, 76
thermodynamic theory, 89
thermo-electric theory, 92
thermogenesis and inogenesis, 93
tonus, 30
inhibition, 35
oscillation, 32
trophic influence of central nervous
system, 6
twitch, load, 13, 16
temperature, 10, 16
veratrine, 31
volume, contraction, 21
voluntary contraction, 19
water content, 41
wave, 21, 24
Weber's paradox, 86
work, diet, 44
heat, 62. 66, 67
respiration, 62
Muscles, insertion, 105
laryngeal, 136
mechanics, 102, 105, 106
metamerism, 306
monomeric and polymeric, 306
resolution of forces, 105
Muscular sense, cerebellum, 446, 467
cerebrum, 582
Musculin, 38
Musical instruments, 132
Myelencephalon, 381
Myelination, cerebrum, 614, 616
spinal cord, 290
Myelomeres, 279, 310
Myoalbumiu, 38
Myoglobulin, 38
Myograms, 6
Myograph, 6, 22
Myohaematin, 38
Myomeres, 279
Myosin, 36, 37
Myosinogen, 37
Myotomes, 303
Narcosis, 310
INDEX OF SUBJECTS
645
Negative variation, muscle, 77
nerve, 210
Nerve, abducens, 411
activity, nature, 254, 256
i<mir theory, 259
alkali, 220
auabolism, 207
anaesthetics, 211, 212
asphyxia, 231
auditory, 405
autogenesis, 236
axial current, 210
bibliography, 276
carbou dioxide, 228
cells. 176 et scq.
agenesis, 330
arsenic, 184
artefacts, 190
caualiculi, 186
chromatolysis, 268, 269
fatigue, 268
metabolism, 268
Nissl granules, 189
regeneration, 268
centres, 259 et scq.
agenesis, 330
alkali, 274
anaemia, 266
asphyxia, 267, 270
atrophy, 330
bibliography, 276
bulbar, 412
calcium salts, 275
circulation, 266
facilitation, 259
fatigue, 271
heat paralysis, 271
inhibition, 259
metabolism, 266, 269, 271
perfusion, 274
poisons, 264
respiration, 272, 273
respiratory quotient, 273
rhythm, 21, 263
salts, 274
spinal, 352 et scq.
cochlear, 405
compression, 193
conduction, 192, 257, 258
degeneration, 254
electrotonic, 247, 254
oxygen, 205
core models, 243, 257
current of action, 210, 211, 215
of rest, 208, 209
degeneration, 232
diphasic action current, 216
double conduction, 197, 200
drugs, 212, 214
effect of salts, 212, 219
electrical stimuli, 222
electrophysiology, 208 et seq.
electrotonic currents, 242
Nerve, electrotonus, 240
excitability, 224
and conductivity, 229
oxygen, 230
facial, 406
fatigue, 227, 228
iluid, 255
forward conduction, 197
galvanic excitability, 248
gas chamber, 231, 232
gases, 212
glossopharyngeal, 401
hypogastric, 373
hypoglossal, 389
impulse, temperature, 205
velocity, 202, 205
factors, 205
wave length, 215
inexhaustibility, '207, 225
isolated conduction, 196
lingual, 373
masticatory, 410
mechanical stimuli, 220
metabolism, 206
oculomotor, 411
optic, 492
oxygen, 207
polarisation, 242
after effect, 250
post-electrotonic current, 244
reaction of degeneration, 253
regeneration, 234
respiration, 231
Hitter- Valli law, 232
roots, Bell-Magendie law, 292
bibliography, 356
section of, 232, 268
specific functions, 262
stimuli, 217
strychnine, 207
survival, 225
syncytium, 235
temperature, 218
tetanisation, 213
thermogenesis, 207
trigeminal, 409
taste, 403
trophic action, 331
tripolar excitation, 250
trochlear, 411
trophic centres, 233
vestibular, 405
Nerves, afferent and efferent, 293
centripetal and centrifugal, 293
cranial, 388
laryngeal, 140, 394
trophic, 331
Nervous system, general physiology,
175-277
morphology, bibliography, 275
plan, 176
Neural crest, nerve development, 236
Neurite, 179
646
PHYSIOLOGY
Neuro blasts, 182
Neurofibrils, 183
Neuromeres, 279
Neurone theory, 179, 180, 191
Neurones, development, 179
unipolar, 260
Neuropile, 260
Neurotaxis, 235
Nicotine method, 367
Nitrogenous metabolism, muscle, 42
Nodus cursorius, 596
Non-polarisable electrodes, 71
Nuclei, corpus striatum, 529
cranial nerves, 390
optic thalamus, 491
Nucleus anibiguus, 401
Bechterew's, 428
caudate, 529, 596
curare, 597
lesion, 596
Deiters', 288, 428
dentatus, 425
emboliformis, 425
fastigii, 425
globosus, 425
lenticular, 529
excitation, 596
lesion, 596
red, 426
Rollers's, 389
Stilling's, 283
Nystagmus, cerebellar, 432
Occipital lobe, vision, 599, 606
Octopus, nerve, 216
Oculomotor nerve, 411
Olfactory apparatus, 527
area, 527, 613, 614, 621
lobule, 527
tract, 527, 615
trigone, 528
Olive, bulb, 387
cerebellar tracts, 429
cerebellum, 387, 428
vertigo, 436
Optic chiasma, 492, 495
lobes, bird, 513
excitation, 512
frog, 512
lesion, 516
phenol, 513
strychnine, 513
nerves, 492
thalami, 490
cortical connexion, 521
excitation, 520
functions, 521
hemianopsia, 522
lesion, 522, 524
nuclei, 491
smell and taste, 523
vision, 521, 522
tract, 493
Orang-outang, cortical localisation, 554
Orientation, cerebellum, 466
Overlapping nerve fields, 303
Over-tones, 131
Oxidation, animal, 43
Oxygen, muscle, 41
rigor mortis, 42
Pallium, 526
Panophthalmitis, trigeminal section, 331
Paraplegia, 342
Parietal lobe, intellect, 624
Pars opercularis, 545
Peduncles, cerebellar, 388, 425, 427, 487
cerebral, 486
Peripheral reflexes, 378
Pharynx, innervation, 397, 405
Phenol, bulb, 415
cerebellum, 477
cortex cerebri, 552
optic lobes, 513
spinal cord, 264
Phonation, 130
bulbar centre, 143
cortical centre, 553
glottis, 144, 145
mid-braiii lesion, 517
pressure, 146
resonance, 147
Phonophotography, 131
Phrenology, 542
Physostigmiue, muscle, 87
Pia mater, 531
Picrotoxin, cortex cerebri, 551, 579
Pigeon, decerebrate, 500
Pigments, muscle, 38
Pitch, sound, 132
Planimetry, spinal cord, 282
Plasma, muscle, 36
Plexus, brachial, 280, 301
cardiac, 398
coeliac, 398
lumbo-sacral, 280, 301
oesophageal, 398
pharyngeal, 397
pulmonary, 398
Plexuses, gangliated, 378
Pneumonia, vagotomy, 399
Polarisation, after effect, 250
electrodes, 241
Pons Varolii, 413 el seq.
sensibility, 416
structure, 420
Post-cellular fibres, 369
Post-ganglionic fibres, 368
Posture, cerebellar lesions, 432
equilibration, 110
erect, 111
expression, 130
mechanics, 107
sitting, 110
Potassium salts, muscle, 41
nerve, 219
INDEX OF SUBJECTS
647
Precellular fibres, 369
Preganglionic fibres, 368
Prevertebral ganglia, 360
Progression, bulbar centre, 413
Projection areas, cerebrum, 592
fibres, cerebrum, 532
of sensation, 202
retino-cerebral, 600
Prosencephalon, 380, 526-635
Protein, lactic acid, 39
metabolism muscle, 43, 45
Proteogenesis, muscle, 45
Proteolysis, muscle, 44
products, 45
Proteose, muscle, 37
Pseudo-reflexes, 374
Psychical blindness, dog, 599
man, 609
deafness, 611
functions, 623
bulbar and pontine, 415
spinal, 311
Puberty, voice, 148
Ptilvinar, 490
lesion, 523
vision, 522
Pyramidal tracts, 287 et seq.
comparative anatomy, 342
origin, 593
Quasi-consciousness, bulb and pons, 415
Quasi-reflexes, 374
Kami communicantes, 365
Reciprocal inuervation, 320, 569
Recitation, 153
Recurrent laryngeal nerve, 140
sensibility, 294, 392
Reflex action, 310 et seq.
final common path, 323
receptive field, 322
receptors, 321
arc, 322
scratch, 321
Reflexes, allied, 323
antagonistic, 323
axon, 374
long and short, 313
Pfliiger's laws, 314
spinal, 313
bibliography, 356
spread, 313
sympathetic, peripheral, 378
Refractory period, spinal cord, 265
Regeneration, nerve, 234
Reinforcement, cerebellar, 483
dorsal spinal roots, 297
sympathetic ganglia, 376
Relaxation, active, 30
muscle, 88
Resolution, forces, 105
tones, 131
Resonators, 131
Respiration, cortical excitation, 570
laryugeal, 141
muscle, 42
nerve, 231
Respiratory centres, bulbar, 412
spinal, 352
quotient, muscle, 42
nerve-centres, 273
Rheochord, 75
Rhinophones, 165
Rhythm, cortex cerebri, 562, 564
oesophageal, Aplysia, 32
tremor, 563
Rigidity, decerebrate, 518
Rigor mortis, 36, 42
Rubidium salts, nerve, 219
Running, curves, 122
Sacral autonomic system, 361, 372
Salivary glands, trophic nerves, 332
Salivation, glossopharyngeal, 405
Salts, nerve stimuli, 219
Sarcolemma, 25
Sarcomeres, 27
Sarcoplasm, 26, 33
Sartorius, contraction wave, 23
innervation, 5
Scratch reflex, 321
Secondary contraction, 77
Secretion, cortex cerebri, 574
Secretory centres, bulbar, 405
cortical, 574
spinal, 352
Segmental limb fields, 304
muscular fields, 303
skin field, 303
Semivowels, 164
Sensation, projection, 202
Sensory-motor area, cortex, 581
dog, 621
man, 589
monkey, 552
Sensory sphere, dog, 583, 584
macacus, 587
Sentences, 171
Serum, muscle, 36
Ship, centre of gravity, 126
Shock, 294, 312, 336, 351, 353
duration, 312
inhibition, 312
Shoes, recording, 115
Sigmoid gyrus, 547
Singing, art, 153
Sinus ovalis, amphioxus, 494
Sitting posture, 110
Skin, innervation, 303 et seq.
trophic nerves, 332
Sleep, knee-jerk, 329
Smell, pulvinar, 523
Solar ganglion, 373
Sound, muscle, 19
physics, 130, 131
Specific nerve energy, 262
648
PHYSIOLOGY
Speech, 625
centre, 545, 625
development, 171
Sphincter ani, extra-spinal centres, 354
Spinal accessory, dyspnoea, 394
functions, 394
larynx, 394
nerve, 392
nuclei, 393
animal, convulsions, 412
cat, 315
centres, rhythm, 324
Spinal cord, 278-358
ablation, 353
anaesthetics, 323
ascending degeneration, 289
at birth, 286
automatism, 323
bibliography, 356
Burdach's tract, 288
cell groups, 283
centres, 351
cerebellar lesion, 429
tracts, 288
Clarke's column, 283, 288
convulsions, 581
degeneration from hemisection, 347
descending degeneration, 290
dorsal column, 285, 289, 350
roots, 284, 293, 295, 296
endogenous fibres, 289
fatigue, 50
Coil's tract, 288
Gower's tract, 288
grey matter, 290
ground bundle, 289
hemisection, 344
lateral columns, 346
long tracts, 341
membranes, 281
motor and sensory decussation, 343
motor path, 345
Miiller's preparation, 292
myelination, 290
nerve roots, 290
pathic path, 290, 345
phenol, 264
pseudo-psychical functions, 338
pyramidal tracts, 287, 342
reflex functions, 310
refractory period, 265
respiration, 272, 273
SchifF's criteria, 344
scratch reflex, 321
segmental relations, 301
sensory paths, 350
Stilling's nucleus, 283
strychnine, 264
tactile path, 345
tonic functions, 323
tracts, 286 et scq.
" unconscious memory," 341
unilateral lesions, man, 349
Spinal cord, vasomotor nerves, 294
ventral zone, 289
visceral functions, 354
white matter, 284
dog, 316
frog, 316, 335
ganglion, conduction, 261
lesions, dystrophies, 353
shock, 353
mind, amphioxus, 341
nerve roots, 280
nerves, 279, 280
metamerism, 301
pigeon, 316
preparation, Baglioni, 272
rabbit, 318
rat, 316
reflexes, circulation, 318
condition of centres, 318
conduction, 314
co-ordination, 320, 335
duck, 337
facilitation, 319, 321
inhibition, 319, 321
irradiation, 315
man, 327, 337
stimuli, 316, 317
symmetry, 314
tonus, oscillations, 324
Staircase contraction, 11
Status epilepticus, 575
Stellate ganglion, cepalopoda, 378
Stimuli, experimental, 217, 218
adequate, 217
chemical, 219
electrical, 222
high frequency, 223
mechanical, 220
specific, 217
summation, 17
thermal, 218
String galvanometer, 73
Strontium salts, nerve, 219
Strychnine, bulb, 415
cerebellum, 477
cortex cerebri, 264, 551
optic lobes, 513
spinal cord, 264
Snbstantia nigra, 487
Sugars, nerve, 219
Sulcus cruciatus, 547
Summation, of stimuli, 17
Superior cervical ganglia, corneal ulcer,
331
laryngeal nerve, 142
Super-position of contractions, 17
Surface tension, contraction, 94
Survival, muscle, 5
nerve, 225
spinal cord, 272
Swimming, 125
Syllables, 170
accent, 171
INDEX OF SUBJECTS
649
Syllables, quantity, 171
Sylvian aqueduct, 488
Sympathetic ganglia, 360 et scq.
analogies, 377
co-ordination, 377
functions, 373
tonic action, 375
fibivs, 362
afferent, 370
analogies, 377
Bell-Magendie law, 292, 365
efferent, 364
nerves, distribution, 363
system, 359-379
anatomy, 360
bibliography, 378
physiological analysis, 365
schema, 371
Synarthroses, 99
Synchoudroses, 99
Syncytium, neural, 183
Synovia, 99
Tabes, ataxy, 469
hyperalgesia, 309
Tactile sense, cerebellum, 446
Tambour myograph, 22
Taste, chorda tympani, 403
cortex cerebri, 616
facial paralysis, 403
glossopharyngeal, 401
nerves, 401
pulvinar, 523
Taurine, muscle, 38
Tegmentum, 486
Telencephalou, 526
Temperature, corpus striatum, 597
muscle, fatigue, 11
inhibition, 35
muscle twitch, 10
nerve, 218
impulse, 205
Temporal lobe, excitation, 610
lesion, 610
Tension, muscle, work, 65
heat, 65
Terminal ganglia, 360
Testis, trophic nerves, 332
Tetanomotor, 221
Tetanus, muscle, 17
opening, 25
Thalamencephalon, 381
development, 489
Thelephorus melanurus, contraction
wave, 28
Thernio-galvanograms, muscle, 61
Thermogenesis, methods, 60
muscle, 59
nerve, 207
Thermometer, Baudin's, 61
Thermopile, muscle, 60
Timbre, 131
Titubatiou, cerebellar, 444
Toad, phenol, and strychnine, 265
Tone, muscular, see Tonus
Tones, fundamental, 131
partial, 131
resolution, 131
vowel, 158
Tonus, muscle, 31
cerebellar, 466
labyrinth, 464
oscillation, muscle, 33
spinal, 323
Tortoise, decerebrate, 499
Tract, Burdach's, 288
direct cerebellar, 288
Coil's, 288
Gower's, 288
intermediolateval, 367
olfactory, 527, 615
optic, 493
pyramidal, 287, 342, 593
Tiirck's, 287
Tracts, cerebellar, 288, 385, 428, 430
Tremor, rhythm, 563
Trigemiual nerve, 409
distribution, 409
functions, 410
paralysis, 410
roots, 409
Trigone, olfactory, 528
Tripolar excitation, 250
polarisation, 247
Trochlear nerve, 411
Trophic nerves, 331
function, cerebellum, 472
Twitch, muscle, 8
Unconscious memory, 341
Unipolar nerve cell, conduction, 261
neurone, Carcinus, 260
stimulation. 251
Urea, muscle, 38
nerve, 219
Uric acid, muscle, 38
Vagotomy, 398
Vagus nerve, 392 el seq.
branches, 393
cardiac fibres, 396
distribution, 397, 402
electrocardiogram, 83
nuclei, 393
reflex vomiting, 397
velocity of nerve impulse, 204
Valve, of Vieusseus, 420
Variation, diphasic, muscle, 79
nerve, 216
negative, 77, 210, 215
positive, 76
Vasomotor centres, spinal, 352
Velocity, muscle wave, 23
nerve impulse, 202, 205
Ventricle, fourth, 389
of Morgagni, 135
650
PHYSIOLOGY
Ventricles, lateral, 490
Veratrine, muscle, 31, 34
Verrnis, lesions, 432, 478
Vertebral column, 111
ganglia, 360
Vertigo, cerebellar, 435
galvanic, 436
olivary, 436
vestibular, 436
Vesicles, cerebral, 380
Vesico-spinal centre, 352
Vestibular nerve, 405
section, 405
Viscera, afferent nerves, 372
cortical excitation, 570
innervation, 370
Visceral disease, cutaneous hyperalgesia,
308
Vision, calcariue area, 602
pulvinar, 524
Visual area, 599
dog, 602, 620
man, 602, 607
monkey, 606
Vocal cords, 135
pbonatiou, 147
Voice, 127-174
bibliography, 173
compass, 148
crescendo, decrescendo, 152
qualities, 149
recitation, 153
Voice registers, 150
singing, 148
Volume-contraction, muscle, 21
Vowel analysis, 160
sounds, nasal, 164
tones, 158, 160
resonance, 159
Vowels, 155, 157
diphthongs, 158
flame pictures, 161
formant tone, 162
pitch, 163
Wave, contraction, 21
White rami, 366
Word blindness, 609, 628
deafness, 612, 628
memory, 630
Words, formation, 170
Work, and metabolism, muscle, 43
and respiration, muscle, 43
locomotion, 97
maximum, 53
Xanthine, muscle, 38
Yellow spot, cortical representation, 609
Zinc electrodes, 71
Zinc salts, nerve, 220
Zones, cutaneous, 308
INDEX OF AUTHOES
ABELOUS, fatigue, '227
D'ABUNDO, corpus striatum, 595
optic thalamus, 595
AUAMKIEWICZ, cortex, secretion, 574
ADAMUK, corpora quadrigemina, 513,
517
medulla oblongata, 418
ABLER, cerebellar lesions, 455, 458,
459, 484
ADRIAN, nerve, conduction, 276, 277
AEBY, contraction wave, 24
AFANASIEFF, nerve, temperature, 218
AIKIN, voice, 174
ALBERTONI, epilepsy, 579, 580, 635
cortical excitation, 560
lesion, 582
optic lobes, 512
ALBRECHT, nerve, electrical excitation,
224
ALCMEON, brain, 538
ALCOCK, taste, 402, 403
nerves, 277
ALDEHOFF, glycogen, inanition, 39
ALDINI, animal electricity, 68
AMICI, line, muscle, 27
muscle mechanism, 91
ANDERSON, hypogastric nerve, 373
sympathetic, 367, 368, 378
white rami, 366
ANDRAL, cerebellum, 484
ANREP, muscle elasticity, 87
APATHY, neuronbrils, 185, 262
neurone theory, 183, 275
ARAKI, lactic acid, muscle, 39
ARISTOTLE, intellect, 631
ARLOING, nerve conduction, 198
sensory roots, 294, 356
D'ARSONVAL, electrodes, 71
high frequency excitation, 19
muscle, contraction, 94
energy, 92
thermopile, 60
ASCOLI, semi- vowels, 173
AUERBACH, plexus, 378
spinal cord, 339
vowels, 160, 173
BABINSKI, asynergy, 470
BABUCHIN, nerve conduction, 199, 204
v. BAEYER, nerve asphyxia, 230
oxygen, 206
BAGINSKI, corpus striatum, 596
8th nerve, 405
BAGLIONI, articulation, 165 ct seq.
bulb, sensory centres, 415
cortex cerebri, 550, 634
dorsal roots, 300
electric organs, 93
grey matter, 263
medulla oblongata, 418
mid-brain, 525
nerve-centres, 272
poisons, 264
nerve roots, 356
optic lobes, 512
reflexes, 276
rhinophones, 165
spinal asphyxia, 412
frog, 316
reflexes, 316
stellate ganglion, cephalopoda, 378
sympathetic, 371
BAILLARGER, cerebral convolutions,
534
cortex cerebri, 532
BALDI, dorsal roots, 298, 356
nerve section, 332
voluntary movement, 587
BALFOUR, nerve origin, 182
BANCHI, nerve autogenesis, 236
BANCROFT, muscle, calcium, 95
BANTI, speech, 634
BARBE, knee-jerk, 329
BARRINGTON, micturition, 379
BARTHEZ, locomotion, 97
BARTHOLOW, cortical localisation, 557
BARTOLOMEI, bulb, 415, 418
BARZELOTTI, muscle, contraction, 21,
22
BASLER, muscle fibres, 10
BASTIAN, cortex cerebri, man, 592, 635
speech, 626, 634
BATESON, hearing, fish, 406, 418
651
652
PHYSIOLOGY
BATTELLI, pcrfusion of spinal cord, 274,
276
BAUDIN, thermometer, 61
BAUER, cerebellum, 485
BAXT, velocity of nerve impulse, 203
nerve conduction, 205
BEAKD, nerve origin, 182
BEAUNIS, vagotomy, 399
v. BECHTEREW, bulb, 417
cerebellar peduncles, 427
cerebellum, equilibration, 461, 484
corpora quadrigemina, 517
cortex cerebri, bladder, 574
respiration, 570
localisation, man, 558
mid-brain, 524
nucleus of, 428
spinal cord, 356
vertigo, 436
BECK, cerebellum, drugs, 478, 485
BECKER, neuroh'brils, 184
BECLARD, muscle, heat, 60
BECQUEREL, muscle, heat, 60
BEEVOR, localisation, man, 558
monkey, 553, 634
smell, man, 615
spinal accessory, 397
BELL, A. M., sound, 173
BELL, C., anatomy of brain, 356
facial nerve, 408
muscular sense, 467
natural system of nerves, 417
spinal nerve roots, 291, 356
trigeminal nerve, 410
BELL, GRAHAM, phonograph, 191
BELLINGERI, facial nerve, 408
trigeminal nerve, 410
BELMONDO, nerve roots, 297, 356
BENECKE, nerve regeneration, 235
BENTZ, spinal accessory, 397
BERNARD, C., aphonia, 140
dorsal roots, 298
ganglion reflexes, 373
hype-glossal, 391
muscle, circulation, 5
excitability, 4
respiration, work, 62
nerve roots, 291
nervous system, 356, 418
rami communicantes, 366
recurrent sensibility, 293
spinal accessory, 394
strychnine, 265
superior cervical ganglion, 331
taste, 403
vagotomy, 398
vagus, 397
BERNHEIMER, visual area, 608
BERNSTEIN, bio -electricity, 258
contraction wave, 23
muscle, action current, 77
demarcation current, 75
physics, 94, 95
BERNSTEIN, muscle, surface tension, 94
waves, 93
nerve, action current, 215, 276
fatigue, 225
rheotome, 77
tetanus, 19
BERT, P., lumbar plexus, 302
nerve conduction, 198
BETHE, brain, fish, 496, 497
mid-brain, 525
nerve-cell function, 260
nerve, compression, 195
degeneration, 234
origin, 182, 275
regeneration^ 235
neurofibrils, 186
BETZ, cortex cerebri, 533
BEYERMANN, cortex cerebri, respiration,
571, 635
spinal skin fields, 303
v. BEZOLD, contraction wave, 24
muscle, veratrin, 31
nerve roots, 297
Plliiger's law, 25
BIANCHI, G., cerebellum, 478
BIANCHI, L., corpus striatum, 595
frontal lobe, 619
BICHAT, brain, 540
life, 1
nervous system, 278
BICKEL, ataxy, 299
inhibition, 321
mid-brain, tortoise, 500
BIDDER, larynx, 395
nerve, conduction, 198
section, 332
sympathetic ganglia, 376
BIEDERMANN, crab claw, 35
electrophysiology, 94, 276
electrotouic current, 244
muscle antagonism, 35
contraction, 93
current, 76
muscular nerves, 36
nerve cells, 179
conduction, 258
BIEHL, vestibular nerve, 405
BIELCHOWSKY, nerve cell, 191
BIFFI, taste, 403, 418
BIKELES, cerebellum, drugs, 478, 485
BILANCIONI, cerebellum, 478
BINNERT, cerebellar localisation, 481,
485
BIRGE, grey matter, 263
spinal nerve roots, 280
BISCHOFF, muscle, urea, 42
spinal accessory, 394
vagus, 392
BLANSCHKO, decerebrate frog, 498
BLIX, muscle elasticity, 87
heat, 66
myography, 8
BOAS, nerve asphyxia, 231
INDEX OF AUTHOES
653
BOCHEFONTAINE, cortex cerebri, bladder,
574
circulation, 571
respiration, 570
secretion, 574
BODDAERT, vagotomy, 400, 418
BOECK, muscle, anisotropy, 27
DE BOECK, spinal inhibition. 321
BoiiM, muscle, veratrin, 31
rigor mortis, 39
BOEKE, vowel analysis, 162
BOERHAAVE, hypoglossal, 391
BOGDANOW, muscle fat, 40
BOLK, cerebellum, 421, 471, 473, 484
development of limbs, 304
spinal metamerism, 303, 356
BOLL, neurofibrils, 184
BOLTON, frontal lobes, 635
BONNE, spinal nerves, 295
BORCHERT, spinal cord, 350, 357
BORELLI, centre of gravity, 107
de rnotu auimalium, 97, 127
muscle, configuration, 47
contraction, 21
excitability, 3
BORUTTAU, core model, 257
muscle, 94
nerve, activity, 259, 276
drugs, 214
BOTTAZZI, muscle contraction, 32
muscle tonus, 33
veratrine, 32
sarcoplasm, 33
spinal hemisection, 348, 357
sympathetic, 378
BOUCHE, cerebellum, 485
BOUDET, contracture, 31
BOUILLAUD, aphasia, 544
cerebellum, 431, 484
cerebrum, 502
BOWDITCH, "All or nothing," 13
knee-jerk, 330
nerve, inexhaustibility, 227
BOYER, pyramidal tract, 342
BRAMWELL, B., speech, 626
BRAUGHTON, taste, 401
BRATJNE, centre of gravity, 108
chronophotography, 116, 127
posture, 110
BRAUNSTEIN, sympathetic ganglia, 375
BRAUS, nerve autogenesis, 236
BRECHET, muscle, heat, 60
BREYMANN, phonetics, 173
BRISSAUD, contracture, 31
corpus striatum, 598
BRISSEAU, knee-jerk, 327
BROADBENT, verbal memory, 630
BROCA, aphasia, 545
speech centre, 545, 625, 634
BRODIE, ruyography, 8
nerve, heat, 276
BRODMANN, area striata, 607
calcarine area, 602
BRODMANN, cortical architecture, 533,
536, 594
localisation, 635
BRONDGEEST, spinal nerves, 296, 356
spinal tonus, 323
BROOKS, spinal reflexes, 357
BROWN, olfactory tract, 615
BROWN, GRAHAM, cortex cerebri,
baboon, 635
mid-brain, 525
progression, 128
spinal cord, 358
BROWN, SANGER, auditory area, 612
visual area, 606
BROWN-SEQUARD, cerebellar lesions, 433
cerebellum, 431
cortical inhibition, 566
epilepsy, 577
motor decussation, 342
muscle, circulation, 5
nerve section, 232
sensory decussation, 343
spinal cord, hemisection, 344, 357
BRUCE, axon reflexes, 379
BRUCKE, diphthongs, 158
muscle fibre, 27
rigor mortis, 36
voice, 173
vowel system, 156
BRUNINGS, muscle sound, 21
BRUGIA, electrotonus, 254
BUBNOFF, cortex cerebri, 561
cortical inhibition, 565
epilepsy, 578, 635
spinal reflexes, 357
BUCHNER, chemical stimuli, 219
BUDGE, corpora quadrigemina, 514
cortex, 546
medulla oblongata, 418
optic lobes, 515
spinal cord, 343
sympathetic ganglia, 375
v. BiiNGNER, nerve regeneration, 235
BiiTNER, fifth nerve, 331
BUNGE, alcohol, 450
muscle ash, 41
BURCH, nerve, action current, 215, 276
BURCKHARD, spinal accessory, 394
BURDACH, tract, 288
BURRIDGE, muscle, fatigue, 95
CAGNIARD-LATOUR, phonation, 146
CALUGAREANU, nerve compression, 195
CAMIS, motor centres, 358
CAMPBELL, area striata, 603
cortex cerebri, 635
CAPOBIANCHO, nerve origin, 182
CARINCOLA, spinal convulsions, 412
CARL, taste, 404
CARLET, locomotion, 97, 127
walking, 115
CARVALHO, muscle, 32
CARVILLE, corpus striatum, 596
654
PHYSIOLOGY
CARVILLE, cortical lesion, 582
excitation of cortex, 560
CATTANI, nerve regeneration, 235
CAZALIS, taste, 403
CERLETTI, frontal lesion, 621
CESANA, G., spinal oscillations, 326
spinal reflexes, 316, 356
CHANDELON, muscle glycogen, 39
CHARCOT, corpus striatum, 598
cortex, man, 590, 634
epilepsy, 577
speech, 629
spinal decussation, 343
CHAUVEAU, muscle circulation, 5
muscle elasticity, 87
energy, 88
spinal accessory, 397
unipolar stimulation, 251
velocity of nerve impulse, 204
CHIAKUGI, hypoglossal, 389
CHRISTIANI, decerebrate rabbit, 505
mid-brain, 524
CLARKE, LOCKHART, column of, 283
intermedi< 'lateral tract, 367
CLARKE, R. H., cerebellum, 476, 485
CLAUSIUS, law of thermodynamics, 89
COENEN, skin fields, 303, 356
COHNHEIM, areas, muscle, 26
COLASANTI, muscle, lactic acid, 40
COLLIER, speech, 626
COLLINS, sympathetic origin, 367
CORNIL, word memory, 630
COWL, inhibition, muscle, 36
Cox, chromatolysis, 268
cortex, man, 592
CRISPOLTI, visual area, 608
GUSHING, cortex cerebri, 635
taste, 418
CUVIER, cerebrum, 416
CYON, labyrinth, 564
nerve roots, 296, 356
spinal tonus, 323
CZERMAK, laryngoscope, 173
vowel sounds, 157
DALTON, cerebellum, 431, 484
DANA, cortex, man, 592
DANILEWSKY, amphioxus, 495
corpora quadigemina, 514
cortex, respiration, 570
muscle, heat, 66
myosin, 37
tripolar electrodes, 247
DANILLO, epilepsy, 579
DASTRE, vasomotors, 293
DAVIES, fifth nerve, 418
DAX, M., aphasia, 544
v. DEEN, aesthesodic nerve-fibres, 256
cortex, 546
spinal cord, 343
DEGANELLO, cerebellum, 484
eighth nerve, 405
labyrinth, 463
DEITERS, formatio reticularis, 388
nerve cells, 177
nucleus, 288
spinal nerve roots, 284
DEJEIUNE, cortex, man, 592, 634
mid-brain, 525
myelogenetic areas, 617
optic thalami, 521
red nucleus, 426
speech centre, 625
visual area, 608
DEMANT, muscle creatine, 38
rigor mortis, 39
DERCUM, cerebellar disease, 459
DESMOULINS, brain, frog, 498
bulbar sensibility, 416
DICKINSON, nicotine method, 368
DOGIEL, neurofibrils, 184
DOHRN, nerve, origin, 182
DONAGGIO, chromatolysis, 269
neurofibrils, 184, 188, 269
DONDERS, muscle, elasticity, 87
nerve section, 334
voice, 151, 173
vowel tones, 159
DREIFUSS, cerebellum, 484
Du BOIS-REYMOND, E., current of rest,
70
electrophysiology, 276
electro tonus, 241
key, 222
law of excitation, 223
mechanical stimuli, 221
muscle, contraction, 93
currents, 70
muscle sound, 20
nerve axial current, 210
current, 208
pre-existence theory, 70
unpolarisable electrodes, 73
Du BOIS-REYMOND, R., antagonist
muscles, 570
locomotion, 128
muscle, 128
DUCCESCHI, cerebellar ablation, 447
cerebellum, 484
nerve centres, 276
conduction, 193, 276
excitability, 224
perfusion of spinal cord, 274
DUCHENNE, locomotion, 97, 127
taste, 403
walking, 115
DUMAS, muscle, mechanism, 91
DUPUY, excitation of cortex, 560
DURET, corpus striatum, 596
cortical lesion, 582
excitation of cortex, 560
DUVAL, bulb, 418
ECKHARD, chemical stimuli, 220
corpus striatum, 596
spinal accessory, 396
INDEX OF AUTHOES
655
ECKHARD, spinal nerves, 301
thermal stimuli, 218
trophic action of ganglia, 331
vagus, 396
EPINGER, brain, anatomy, 356
fish and man, 529
cerebellar tracts, 428
fish brain, 528
formatio reticularis, 388
sensory cerebellar tract, 428
spinal cord, 286, 290
thalamus, 521
EDISON, phonograph, 191
EDWARDS, sympathetic, 379
EFRON, nerve compression, 193
EHRENRERG, nerve cells, 177
EHKLICH, nerve cell, 179
EIGENBRODT, spinal cord, 343
EINTHOVEN, galvanometer, 73
high frequency excitation, 19
muscle, physics, 94
ELLIOTT, sympathetic, 379
ENGEL, voice, 148
ENGELMANN, chordograms, 92
inotagmata, 90
muscle energy, 89, 93
injury current, 70
nerve degeneration, 233
injury current, 209
Pfliiger's law, 25
Thelephorus, 28
ERASISTBA.TUS, nerves, 291
ERB, knee-jerk, 326
reaction of degeneration, 6, 253
spinal cord, 281
degenerations, 287, 357
ERMAN, muscle contraction, 22
ESCHRICHT, fifth nerve, 410
ESMARCH, bandage, 329
EULENBERG, knee-jerk, 327
EWALD, ablation of cord, 353
labyrinth, 461, 484
muscle contraction, 22
spinal cord, 357
EWART, muscle and electric organs, 93
EWING, vowel tones, 162, 173
EXNER, "Bahnung," 321
cortex, man, 590, 634
spinal ganglion cell, 261
reflexes, 356
FANO, bulb, 418
cortical inhibition, 567
frontal lesion, 620
mid-brain, toad, 499, 524
tortoise, 500
muscle tonus, 32
oscillation of tonus, 324
progression, 413
reflexes, 324
spinal cord, 357
vagus, electro-cardiogram, 83
FASOLA, hippocampus, 615
FERREIN, larynx, 143
FEURIER, auditory area, 610
brachial plexus, 302
brain, monkey, 551
cerebellum, 431, 484
disease, 459
equilibration, 461
functions, 465
lesions, 434
corpora quadrigemina, 513
cortex cerebri, 548
epilepsy, 574, 635
excitation, 560
functions of brain, 634
mid-brain, 524
olfactory area, 613
optic lobes, 513
thalamus, 520, 522
restiform body, 428
vermis, 478
visual area, 606
FICK, isotony and isometry, 14
joints, 99
locomotion, 127
muscle, energy, 88
heat, 65, 94
thermodynamics, 89
veratrin, 31
nerve conduction, 205
post-electrotonic current, 244
walking, 114
FIENGA, grey matter, 263
spinal preparation, 272
FISCHER, 0., arm movements, 104
centre of gravity, 108
walking, 116, 120, 127
FLECHSIG, anencephaly, 509
auditory cortex, 612
brain and mind, 634
cerebellar tract, 288
cortical areas, 592
centres, 630
frontal lesion, 620
hippocampus, 615
myelogenetic law, 616
spinal tracts, 285
taste, 616
visual area, 602, 60S
v. FLEISCHL, nerve excitability, 224
FLEMMING, chromatolysis, 268
neurofibrils, 184
FLOAD, cortical lesion, 588
FLOURENS, brain, bird, 500
frog, 498
bulb, 418
cerebellum, 430, 461, 467, 484
cerebrum, 543
consciousness, 416
labyrinth, 406, 461
optic lobes, 515
FODERA, cerebellum, 430
fifth nerve, 331, 410
spinal cord, 343
656
PHYSIOLOGY
FODERA, spinal nerve-roots, 292
taste, 401
FONTANA, decerebrate tortoise, 413
muscle elasticity, 85
nerve conduction, 193
FORBES, reflex rhythms, 358
FOREL, corpora quadrigemina, 515
eighth nerve, 405
FORGUE, spinal roots, 302
FOSTER, nerve metabolism, 206
spinal frog, 339
FOURNIE, voice, 173
FOURNIER, corpus striatum, 596
FRAGNITO, nerve origin, 182
FRANQOIS - FRANCK, brain, motor
functions, 634
cortex, circulation, 571
respiration, 570
cortical excitation, 561
rhythm, 563
epilepsy, 575, 635
FRANK, 0., muscle, thermodynamics, 94
FREDERICQ, autotomy, 336
nerve, axial current, 210
centres, anaemia, 266
survival, 225
velocity of nerve impulse, 204
FRENCH, falsetto voice, 151, 173
FREUSBERG, bulb, 418
spinal asphyxia, 412
v. FREY, muscle, R.Q., 42
twitch and tetanus, 33
FRITSCH, cortex cerebri, 546
epilepsy, 574, 635
Lophius piscatorius, 266
FROHLICH, FR., cephalopod ganglion, 264
nerve, drugs, 214
excitability, 276
fatigue, 228
oxygen, 205, 207
staircase contraction, 11
tetanus, 34
V. FtiRTH, muscle, chemistry, 94
rigor mortis, 37
FUNKE, nerve, strychnine, 207
GABRI, spinal nerves, 295
GAD, inhibition of tonus, 36
muscle, latency, 9
thermodynamics, 89
twitch, 16
temperature, 10
nerve, repair, 207
spinal nerves, 295
GAGLIO, cerebellum, 484
space-perception, 464
GALEN, aphonia, 141
hypoglossal, 390
nerves, 291
spinal cord, 343
GALEOTTI, muscle, contraction, 94
physics, 94, 95
nerve, regeneration, 235
GALL, F. J., brain, 538
phrenology, 542
GALVANI, electrical excitation, 224
muscle, electricity, 68
GANSER, corpora quadrigemina, 515
GARCIA, M., laryngoscope, 145
voice, 151, 173
GARTEN, nerve fatigue, 227
GASKELL, heart currents, 82
sympathetic, 360, 366, 378
GAVARRET, phouation, 173
v. GEHUCHTEN, nerve-cells, 178
nerve-cell degeneration, 268
GERDY, locomotion, 97
GERLACH, nervous anastomosis, 177
GHILARDUCCI, reaction at a distance,
253
GIANNUZZI, vagus, 396
GIERSE, muscle, heat, 60
GLEY, medulla oblongata, 418
GLISSON, muscle contraction, 21
GLUGE, nerve conduction, 198
GOIDANICH, vowel sounds, 158, 174
GOLGI, cerebellar cortex, 182
nerve-cells and fibres, 177, 275
neurone theory, 180, 188
olfactory tract, 615
pericellular net- work, 187
tendon organ, 320
GOLL, tract, 288
GOLTZ, ablation of cord, 353
brain, frog, 497
bulb, 418
cortex cerebri, 634
vision, 600
cortical lesion, dog, 582
monkey, 586
decerebrate dog, 506
labyrinth, 463
mid- brain, 524
posture, 415
reflexes, 356
shock, 312
spinal centres, 352, 357
co-ordination, 335
frog, 340
GOTCH, Malapterurus, 204
muscle, action current, 77
nerve, action current, 210, 215
conduction, 197, 276
electrophysiology, 276
refractory period, 277
temperature, 205
spinal paths, 348, 357
GOTSCHLICH, muscle reaction, 40
GOWERS, W. R., aphasia, 626
cerebellar disease, 459
corpus striatum, 598
diseases of nervous system, 356
knee-jerk, 327
speech centres, 626, 634
spinal cord, 282
tract, 288
INDEX OF AUTHOES
657
K.i;, cerebellar lesions, 481, 485
larynura.1 nerves, 1-10, 395
medulla olilmigata, 418
GRAINGER, .-pinal reflexes, 335
GiiATioi.KT, 1'. , ansa peduncularis, 492
eeivbral localisation, ;". l.~>
CRIFKI rns, cortical rhythm, 563
spinal ganglia. 357
GROSSMANN, laryngeul nerves, 396,
MS
Gui'MiAi'M, cortical excitation, 560
cortical localisation. 555, '!" I
spinal cord, 'JS9
OiirxnAGEX, core model, 1243
elect rotonic latency, 246
nerve, CO,, 228
GRI rzsEi:, chemical stimuli, 219
muscle fibres, 10
muscle, veratriu, 32
nerve current. 210
excitability, 224, 276
phouation, 146
tetanus, 33
\ ocal conls, 139
\ <.wels, 163
(ii:i X.MACH, diphthongs, 158
GSCHEIDLKX, grey matter, 270
GrDDEN, commissure, 493
corpora qualrigemina, 515
internal capsule, 595
method of, 268
olive, 387
optic thalamic, 521
Gf NTHEU, nerve degeneration, 233
Ci TZMAXN, voice, 174
GUZOT, taste, 403
HAGEMAXX, muscle, efficiency, 67
HALL, taste, 401
HALL, MARSHALL, excitomotor system,
341
shock, 312
spinal reflexes, 337, 357
HALL, STANLEY, muscle sound, 21
v. HALLER, aphonia, 141
brain, 538
muscle, excitability, 3
neural activity, 255
HALLIBURTON, biochemistry, 277
heat coagulation, 37
muscle, chemistry, 94
proteins, 37
nerve, heat contraction, 276
HALLOCK, voice, 173
vowel analysis. 161
HAM.MAKSTEN, muscle, chemistry, 38
HANNOVER, nerve cells, 177
HANSEMAXN, cerebrum, intellect, 624
HARLESS, centre of gravity, 108
spinal nerves, 296
tetanus, 19
vocal cords, 136
voice, 173
VOL. Ill
HARRISON, nerve development, 236
nerve origin, 182
II \KTWELL, antagonist muscles, 306
HAUGIITON, muscle, absolute force, 47
HAUSEN, neural activity, 255
HEAD, cerebral lesions, 358, 635
sensory zones, 308, 356
nerves, 277
spinal cord, 358
HEIDENHAIN, cortex cerebri, 561
cortical inhibition, 565, 566
epilepsy, 578, 635
muscle, heat, 61
nerve, excitability, 224
thermogenesis, 207
spinal accessory, 394
reflexes, 357
tetanomotor, 221
tetanus, 19
vagus, 396
HELD, neurofibrils, 184
neurone theory, 188
HELI.WAG, vowel sounds, 155
HELJIHOLTZ, muscle, glycogen, 39
latency, 8
sound, 20
thermopile, 61
waves, 93
nerve cells, 177
excitability, 276
temperature, 205
thermogenesis, 207
superposition of contractions, 17
tetanus, 17
tones, 131, 173
velocity of nerve impulse, 202
vowel tones, 159
HENKE, joints, 97
muscle, absolute force, 47
HENLE, bulb, 385
laryngeal cartilages, 134
lateral ventricles, 490
HENSOHEN, cortex, man, 592
frontal lesion, 620
localisation, 634
visual area, 602, 608
HENSEN, singing, 154
voice, 173
vowel analysis, 162
HERING, E., core model, 243
muscle current, 76
nerve current, 210
Pfliiger's law, 25, 250
unconscious memory, 341
HERING, H. E., cortical inhibition, 568
dorsal roots, 298
strychnine, 265
HEKLITZKA, nerve centres, 275, 276
HERMANN, bulbar convulsions, 412
contraction wave, 24
core model, 243, 257
muscle, currents, 70
diphasic variation, 80
2u
658
PHYSIOLOGY
HERMANN, muscle, gases, 41
heat, 65
physiology, 94
nerve, conduction, 199, 201, 257
diphasic variation, 216
electrophysiology, 276
injury current, 209
phonophotography, 131
semivowels, 166
thermal currents, 76
voice, 173
vowel tones, 162
HEROPHILUS, nerves, 291
HERRING, sympathetic, origin, 367
HERTZ, waves, 223
HERZEN, A., vagotomy, 398
HESEN, corpora quadrigeiuina, 517
HEYMANNS, muscle twitch, tempera-
ture, 10
HIGHMORE, antrum, 409
HILL, A. V., muscle, physics, 95
HIRSCHMANN, nicotine, 368
His, embryo brain, 527
foetal brain, 382
nerves, 181
olfactory lobe, 528
HITZIG, cerebellum, 484
cortex cerebri, 546
epilepsy, 574
vision, 599
cortical excitation, 560, 633
myelogenetic areas, 617
vertigo, 436
HLASKO, corpora quadrigemina, 515
HOFMANN, F. B., end -plate fatigue,
226
muscle, 94
sympathetic co-ordination, 377
HOLMES, GORDON, cerebral lesions, 358,
635
pyramidal tract, 635
HOLMGREN, nerve-cell, 186
HOPPE-SEYLER, myohaematin, 38
HORBACZEWSKY, eighth nerve, 405
HORSLEY, cerebellum, 485
cortex, monkey, 552
cortical localisation, 634
rhythm, 562
epilepsy, 577
excitation of cerebellum, 476
glottis, 142
localisation, man, 557
monkey, 553
motor area, 635
nerve, action current, 210
conduction, 197
spinal accessory, 397
convulsions, 581
paths, 348, 485
HORTON-SMITH, spinal nerves, 293
HUBER, nerve regeneration, 235
HURTHLE, muscle contraction, 30
nerve, stimuli, 223
v. HUMBOLDT, muscle electricity, 68
nerve, excitation, 224
HUN, visual area, 602
IMAMURA, SHINKICHI, cortex cerebri, 634
vision, 601
IMBERT, muscle, contraction, 94
INANZI, taste, 403
INGELS, cerebellum, agenesis, 456
JACKSON, HUGHLINGS, cerebellar disease,
459
epilepsy, 574, 635
mid-brain, 524
optic thalami, 522
smell, man, 615
speech, 626
JACOB, ataxy, 299
myomeres, 304
JACOBSOX, nerve, 400
JAEDERHOLM, nerve artefacts, 190
JAMES, W., conduction, 197
JAPPELLI, corpora quadrigemiua, 516
mid-brain, 525
JENDRASSIK, knee-jerk, 330
JENKIN, FLEEMING, vowel analysis,
162, 173
JENSEN, muscle, contraction, 94, 95
JESPERSEN, phonetics, 173
JOHANNSEN, corpus striatum, 596
JOLYET, spinal accessory and vagus, 396
JOSEPH, M., spinal nerves, 295
KAISER, muscle relaxation, 14
KALISCHER, auditory and visual area,
dog, 622, 634
KANT, soul and brain, 541
KARPLUS, cortex cerebri, 634
decerebrate monkey, 510
mid-brain, 525
KATZENSTEIN, cerebellum, 485
VAN KEMPEN, spinal accessory, 395
KEY, nerve cells, 178
KLEIN, pharynx, 405
KLUNDER, singing, 154
KNOLL, muscle fat, 40
KNORZ, muscle, absolute force, 47
KOCH, hypoglossal nucleus, 391
KOCHER, spinal lesions, 349, 357
spinal metamerism, 303
v. KOLLIKER, dorsal roots, 284
formatio reticularis, 388
histology, 356
muscle, excitability, 4
waves, 93
nerve cells, 178
sympathetic cells, 361
nerve, 369, 378
KONIG, acetabulum, 100
manometric flames, 131
vowel tones, 161
VAN DER KOLK SCHRODER, spinal roots,
301
INDEX OF AUTHOKS
659
K<)i:\].'Ki.i>. taste, 401
Ki'^'HKU NiKnKF, spinal nerves, 301
KnsTi--.il, muscle, absolute force, 47
KOWAI.K.WSKY, pupil, 375
KuAr.i'KUN, fatigue, 51
KKATSK, F., localisation, man, 559,
634
KiiArsK, H., cortical centres, 552
iiifiiiliraii'1, muscle, 27
metamerism, 301
muscle and electric organ, 91
KRATSS, muscle glycogen, 39
KUEIDI,. bulb, 418
cortex cerebri, 634
decerebrate monkey, 510
hearing, fish, 406
mid-brain, 525
vox KRIES, muscle sound, 21
tetanus, 33
KROXECKEU, grey matter, 263
muscle, fatigue, 11
sound, 21
tetanus, 18
KUONEXBERG, spinal roots, 301
KSCHISCHOWSKI, optic lobes, 513, 525
KUHXK, chemical stimuli, 220
gracilis experiment, 200
muscle, electric organs, 91
excitability, 4
pigments, 38
nerve conduction, 199, 276
rigor mortis, 36
KfPFFER, amphioxus brain, 380
nerve, origin, 182
KURZVEIL, FR., cortex cerebri, 634
visual area, 602
KUSSMAUL. alexia, 629
bulbar convulsions, 412
cortex cerebri, 634
word blindness, 609
deafness, 612
LAFARGUE, cerebellum, 433
LAMBERT, nerve cell, 268
nerve, inexhaustibility, 227
LANDERGRBN, asphyxia, 267
LANDOIS, bulbar convulsions, 412
cortex, 550
LAXGE, cerebellum, 484
labyrinth, 462
LANGELAAN, cerebellar ataxy, 453
cerebellum, 484
cortex, respiration, 571
hyperalgesic areas, 308
skin fields, 303, 356
LAXGENDORFF, grey matter,
mortem acidification, 270
mechanical excitation, 221
pupil, 375
spinal reflexes, 316
tonus, 326
superior cervical ganglion, 369
LANGER, locomotion, 97
LANGLEY, autonomic system, 359, 361,
365, 368
axon reflex, 375
hypogastric nerve, 373
muscle, receptive substance, 95
nicotine method, 367
rami communicantes, 366
sympathetic reinforcement, 376
system, 378
LANNEGRACE, spinal roots, 302
LAPINSKY, spinal centres, 351, 357
LAULANIE, muscle elasticity, 87
LAUTEXBACH, cortex, vision, 600
nerve conduction, 205
LEAPER, nerve, pressure, 277
LEE, hearing, fish, 406
medulla oblongata, 418
LEGALLOIS, vagotomy, 398
LEHFELDT, voice, 151
LEHMANN, muscle efficiency, 67
corpus striatum, 596
LEMOIGNE, cerebrum, 502
corpora quadrigemina, 515
cortical lesion, 582
VON LENKOSSEK, nerve-cells, 178
neurofibrils, 184
pyramidal tract, 342
spinal nerve roots, 293
LEPSIUS, alphabet, 173
LEVEN, cerebellum, 431, 484
LEVI, nerve regeneration, 235
neurofibrils, 185
LEVY, myohaematin, 38
LEWANDOWSKY, cerebellum, 435, 468,
484
pupil, 375
LEWIS, BEVAN, cortex cerebri, 533
LIBERTIXI, cortical inhibition, 566
LIEBIG, muscle energy, 42
muscle reaction, 39
LIEDLER, cerebellum, 485
LILLIE, muscle, contraction, 95
LINGLE, muscular tone, 358
LIPPMAXN, electrometer, 72
LISKOVIUS, phonation, 173
Lisso, cortex, man, 590
LLOYD, vowel analysis, 162
LOEB, brain, fish, 497
frog, 498
consciousness, 511
cortex, vision, 600
psychical functions, 543
LOMBARD, fatigue, 50, 95
Lo MONACO, corpus striatum, 597
cortical centres, 553, 634
optic thalami, 520, 522, 525
LONGET, aphonia, 141
brain, frog, 498
cerebellar lesions, 433, 484
cerebrum, 502
cortex cerebri, 546
hypoglossal, 391
muscle, excitability, 4
2 U 2
660
PHYSIOLOGY
LONGKT, nerve roots, 291, 356
nerve section, 232, 357
optic lobes, 515
pons, 416
recurrent sensibility, 293
singing, 153
spinal accessory, 394
trigeminus, 331
vocal cords, 138
LOURIE, cerebellum, 485
LOV^N, muscle sound, 21
vagus, 397
LucAs, muscle, contraction, 95
myography, 8
nerve, conduction, 276
LUCHSINGER, Bell's law, 293
muscle, antagonism, 35
glycogen, 39
nerve, excitability and conductivity,
229
LUCIANI, active relaxation, 30
area striata, 604
auditory area, 611
centre of centres, 622, 631
cerebellar ataxy, 465
extirpation, 426
gait, 438, 440, 451
cerebellum, 431, 484
corpus striatum, 595
cortex, man, 591
sensation, 588
vision, 599
cortical excitation, 560
lesion, 582
localisation, 634
dog, 548
dysmetria, 298
epilepsy, 575, 635
joints, 106
muscle, relaxation, 88
nerve, currents, 243
olfactory area, 614
olive, 387
orthography, 174
rhinophones, 165
spinal hemisection, 348
nerve, roots, 356
word deafness, 613
LUDWIG, glossopharyngeal, 405
muscle, circulation, 5
R.Q., 42
taste, 405
LUDERITZ, nerve conduction, 193
LUGARO, nerve centres, 276
neurofibrils, 184
nerve-cell degeneration, 268
LUNA, cerebellar localisation, 481, 484
LUSSANA, cerebellum, 431, 461, 467, 484
cerebrum, 502
corpora quadrigemina, 515
cortical lesion, 582
medulla oblongata, 418
taste, 403
Lrvs, centre median, 521
cerebellum, 461, 484
thalamus, 521
MACDONALD, muscle, structure, 95
nerve, concentration cell, 258
temperature, 205
MACDONNEL, muscle, glycogen, 39
MAcDoucALL, fatigue, 95, 358
inhibition, 358
MACH, stroboscopic disc, 145
M'KENDRICK, vowel analysis, 162
MAG-MUNN, myohaematiu, 38
MAcNALTY, spinal tracts, 485
MACWILLIAM, knee-jerk, 327
MAGENDIE, aphonia, 141
brain, frog, 498
bulbar sensibility, 416
cerebellar lesions, 433
cerebellum, 431, 484
equilibration, 461
cerebrum, 502
cortex, cerebi'i, 546
fifth nerve, 331, 410
hypoglossal, 391
nervous system, 418
phonation, 144
recurrent sensibility, 293
spinal cord, 357
nerve roots, 291, 356
taste, 401
MAGGIORA, fatigue, 50, 95
MAGNAN, epilepsy, 581
MAGNINI, bulb, 415. 418
cerebellum, drugs, 477
localisation, 485
cortex, ccrebri, 550, 634
strychnine, brain, 264
MAGNUS, intestine, 378
MALGAIGNE, glottis, 144
MANCHE, muscle glycogen, 39
MANDL, glottis, loi
MANGOLD, muscular nerves, 36
MANN, nerve-cell, 268
v. MANSFELT, muscle elasticity, 87
MANTEGAZZA, nerve section, 332
MARASSINI, cerebellar localisation, 481,
485
MARCACCI, lumbar plexus, 302
nerve roots, 297
MARCHAND, grey matter, 263
MARCHI, caudate nucleus, 529
cerebellar tract, 288, 429, 484
cerebellum, 426
method of staining degenerated nerve,
234
Purkinje's cells, 427
MARCHIAFAVA, aphasia, 627
MARCUSE, muscle acidity, 40
MAREY, gait, 126
graphic method, 128
locomotion, 97, 128
muscle contraction, 22. 24
INDEX OF AUTHORS
661
MAKKY, muscle, elasticity, 87
myograph, 22
velocity of nerve impulse, 203
walking, 115
MA i HE, P., aphasia, 627
M viiiNKsr,!, nerve - cell, degeneration,
268
nerve centres, 276
neurotibrils, 184
M \UTIN, antagonist muscles, 306
M AUIINOTTI, spinal cord, 357
MATHISOX, asphyxia, 418
MATTEUCCI, animal electricity, 255, 276
core model, 243
cortex, 546
reflexes, 316
secondary contraction, 69, 77
spinal nerve roots, 356
tetanus, 17
.MATTHIAS, semi-vowels, 166
MAXWELL, cortex cerebri, 550, 634
.MAY, PAGE, afferent path, 358
pyramidal tracts, 635
MAYER, optic lobes, 515
MAYER, C., hypoglossal, 389
spinal nerves, 301
MAYER, G. R., thermodynamics, 89
MAYER, S., sympathetic, 378
MAYO, fifth nerve, 331
glottis, 144
hypoglossal, 391
taste, 401
MI-.KK. nerve conductivity, 277
MEIGS, muscle, heat coagulation, 95
MEISSNER, bulb, 418
nerve section, 334
MELLONI, thermopile, 61
MELLTIS, pyramidal tract, 342
MENDELSOHN, excitation of cerebellum,
475
nerve axial current, 210
spinal reflexes, 357
MEKKEL, vowel tones, 160, 173
MERZBACHER, ataxy, 299
MEYER, C., vocal cords, 139
MEYER, centre of gravity, 108
locotnotioD, 127
muscle mechanism, 91
MEYER, G. H., vertebral column, 112
MEYER, H., locomotion, 97
MEYXERT, cerebellum, 428
cortex cerebri, 533
olfactory tract, 615
MICHIELI, cortical excitation, 560
cortical lesion, 582
MiES'-'HER, spinal cord, 346, 357
MILLS, cortex, man, 591
MINES, summation of contractions, 95
M i KGAZZINI, G., brain, 634
cerebellar agenesis, 455
lesions, 485
peduncles, 425
cerebello-spinal paths, 430
MINGAZZIXI,G., cerebrum, intellect, 624
corpus striatum, 598
Purkinje's cells, 427
speech centres, 626, 634
spinal cord, 290
MINKIIWSKI, cortex cerebri, 634
visual area, dog, 604
MISLAWSKY, cortex, secretion, 574
MITCHELL, WEIR, cerebellum, 431, 484
MODENA, nerve regeneration, 240, 276
MHXCKEBERG, nerve degeneration, 234
MHMMSEN, spinal tonus, 324
v. MONAKOW, auditory cortex, 612
cerebellar ataxy, 458
cerebellum, 484
corpora qiiadrigemina, 515
corpus striatum, 598
cortex cerebri, localisation, 634
man, 591, 592
mid-brain, 525
myelogenetic areas, 617
occipital cortex, 601
speech, 634
visual area, 608
MONARI, muscle creatine, 38
MONROE, spinal roots, 301
MONTI, A., chromatolysis, 269
MOORE, spinal ganglion conduction,
262
MORAT, spinal nerves, 295
MORAWITZ, spinal cord, 274
MOREAU, spinal nerve roots, 292
MORGAGNI, vagotomy, 398
ventricle, 135
MORGANTI, medulla oblongata, 418
spinal accessory, 394
taste, 403
MORIGGIA, nerve, salts, 220
MORSELLI, dynamograph, 48
epilepsy, 579
MOSCATELLI, muscle, lactic acid, 40
Mosso, ergograph, 48, 95
fatigue, intoxication, 59
Mosso, U., fatigue, food, 51
MOTT, cortex, localisation, gibbon, 635
sensation, 588
dorsal roots, 298
spinal heniisection, 346, 357
nerve roots, 356
sympathetic, origin, 367
visual area, 635
voice, 174
MULLER, ERIK, neurofibrils, 184
MULLER, G. E., muscle, energy, 92
MULLER, H., muscle waves, 93
MULLER, JOHANNES, aphonia, 141
bulbar sensibility, 416
larynx, 143
muscle contraction, 21
spinal nerves, 291, 356
taste, 401
velocity of nerve impulse, 202
MULLEII, W., spinal decussation, 343
662
PHYSIOLOGY
MUNK, H., auditory area, 610
brain, frog, 498
cerebellum, 484
cortex cerebri, 634
respiration, 571
cortex, vision, 599
decerebrate pigeon, 502
rabbit, 505
dursal roots, 299
epilepsy, 579
mid-brain, 525
psychical functions, 54-'!
sensory sphere, 583
spinal nerve roots, 356
word blindness, 609
deafness, 610
MUNK, J., cerebellum, 435
MUNZER, optic decussation, 493
optic lobes, 515
spinal cord, 289
nerves, 295
MURATOFF, pyramidal tract, 342
MURRI, cerebellum, 465, 484
MrssKX, hypoglossal, 418
MUYBRIDGE, locomotion, 97
NAGY v. REGECZY, inhibition of tonus,
36
NANSEN, nerve-cell function, 261
NASSE, muscle glycogen, 39
nerve degeneration, 233
NAVRATIL, spinal accessory, 395
NAWALICHIN, muscle, heat, 64
NAWROCKI, bladder, 373
muscle creatine, 38
spinal cord, 346, 357
NEGRO, cerebellar localisation, 476
NELATON, nerve section, 332
NELLS, chromatolysis, 268
NERNST, nerve activity, 259
NEUMEISTER, physiological chemistry,
94
NICOLAIDES, grey matter, 263
vagotomy, 398
NISSL, nerve cell, 189, 268, 275
nerve centres, 276
neurone theory, 183
visual area, 602
NOBILI, animal electricity, 255
electrotonic excitability, 245
muscle electricity, 69
NOTHNAGEL, bulbar convulsant centre,
412
cerebellum, 431, 484
ataxy, 458
excitation, 435, 475
corpus striatum, 596, 598
cortex cerebri, 634
Novi, electrotonus, 254
epilepsy, 579, 635
muscle, fatigue, 12
NUSSBAUM, bladder, 373
OBERSTEINER. cerebellar tracts, 428
OBOLENSKY, nerve section, 332
OCANA, GOMEZ, vagotomy, 398
ODDI, cortical inhibition, 567
nerve roots, 297, 356
OERTEL, laryngoscopy, 145
voice registers, 173
OKER-BLOM, concentration cells, 258
electrode, 71
OLLIVIER, cerebellum, 431, 484
ONIMUK, excitation of cortex, 560
ONUF, sympathetic, origin, 367
ONUFROWICZ, eighth nerve, 405
OPPENHEIM, aphasia, 628, 634
corpus striatum, 598
cortex, man, 592
ORBELLI, sympathetic, 378
OSTVVALD, bioelectric phenomena, 258
electrode, 71
OTT, corpus striatum, 597
OWSJANNIKOW, bulb, convulsions, 413,
418, 581
PAGANO, cerebellum, curare, 435, 476,
485
localisation, 481
corpus striatum, 597
PALADINO, nerve, origin, 182
PANCONCELLI-CALZIA, phonetics, 174
PANEGROSSI, aphasia, 627
PANICHI, spinal nerves, 295
visual area, 607
PANIZZA, corpora quadrigemina, 515
cortex, vision, 599
dorsal roots, 298
eye, cortex cerebri, 603
hypoglossal, 391
medulla oblongata, 417
muscular sense, 467
nerve roots, 291, 356
taste, 401
voluntary movement, 587
PARKER, hearing, fish, 406, 418
PASSY, phonetics, 174
PATRIZI, cerebellar ataxy, 445
cerebellum, 484
heart, acceleration, 573
muscle, fatigue, 95
hibernation, 10
PAUKUL, muscle fibres, 10
PAULSEN, voice, 148
PAWLOW, vagotomy, 398
PERRONCITO, nerve regeneration, 237,
238
DU PETIT, cerebellum, 433
PETREN, spinal lesions, 350, 357
PETRINA, cortex, man, 590
PETTENKOFER, muscle, work, 43
PETTIGREW, locomotion, 127
PEYER, metamerism, 301
PFAFF, electrical excitation, 224
PFLUGER, animal oxidation, 43
avalanche theory, 224
INDEX OF AUTHOES
663
I'KI.I tiKii, electrotonic excitability, 245
law of contraction, 25, 248
laws of reflex action, 314
muscle energy, 88
myograph, 7
protein and work, 43
spinal cord, 339, 356
v. PFUNGEN, cortex cerebri, gut, 574
I'liiiJi'K.vrx, nerve, conduction, 198
TICK, cerebellar tract, 430
fibrin proteolysis, 45
visual area, 608
PILCHEU, vasomotor centre, 418
PIOTUOWSKI, muscle inhibition, 35
nerve, 229
PIPPING, vowel analysis, 162, 173
PITRES, cortex, man, 590, 634
respiration, 570
cortical excitation, 561
rhythm, 563
epilepsy, 575, 635
pyramidal tract, 342
spinal decussation, 343
POIROT, phonetics, 174
POISSON, locomotion, work, 97
POL, HULSHOFF, cerebellar localisation,
481, 485
POLIMANTI, nerve roots, 297, 302, 356
PORTER, spinal reflexes, 358
PRAUSNITZ, muscle glycogen, 39
PREVOST, muscle, mechanism, 91
taste, 403
PROBST, cerebellum, 484
mid-brain, 518, 525
occipital cortex, 601
vertigo, 436
PROCHASKA, perception, 540
PRUSS, cerebellar localisation, 476, 485
PURKINJE, cells, 424
vertigo, 436
PURPURA, nerve fusion, 240, 276
nerve regeneration, 236
RAFFAELE, nerve origin, 182
RAHN, glossopharyngeal, 405
RAMON Y CAJAL, cortex cerebri, 533
dentate nucleus, 426
dorsal roots, 284
nerve cells, 177, 275
neurofibrils, 190
neurone theory, 180
Purkinje's cells, 427
spinal nerve roots, 293
unipolar nerve cell, 261
RANKE, fatigue intoxication, 59
nerve, fatigue, 228
RANVIER, muscle, 28, 94
red and pale, 9
nerve degeneration, 232, 233
regeneration, 234
ueurofibrils, 184
RECKLINGHAUSEN, cerebellum, 503
REDI, progression, 413
REDLICH, cortex, man, 592
RICGNAT, nerve cell, 268
REID, taste, 403
REIL, fillet, 487
spinal nerves, 301
REMAK, nerve cells, 177
RENZI, cerebrum, 502
optic lobes, 515
posture, 414
RETZIUS, cerebrum, intellect, 624
nerve cells, 178
REYNOLDS, spinal ganglion, conduction,
262
REZEK, corpus striatum, 596
RIBOT, memory, 631
RICHARDSON, myography, 8
RICHET, contracture, 31
cortex cerebri, 561
circulation, 571
crab claw, 35
muscle, excitability, 4
heat, 59
physiology, 94
nerve conduction, 205
summation of stimuli, 17
tremor, 563
RITTER, nerve, excitability, 224
section, 232
opening tetanus, 250
RIVERS, nerve section, 277
ROBE, spinal paths, 358
ROBER, muscle, fatigue, 76
ROBERTSON, nervous system, 275
ROBINSON, neural activity, 255
ROHMANN, nerve, torpedo, 207
ROLANDO, brain, birds, 500
cerebellum, 430, 466, 484
mid-brain, 413
sulcus of, 531
ROLLER, nucleus of, 389
ROLLESTON, nerve, thermogenesis, 207
ROLLET, contraction wave, 28
muscle, 94
nerve, excitability, 224
RONCORONI, frontal lobe, 622
speech, 634
ROSAENDA, cerebellar localisation, 476,
485
ROSENBACH, epilepsy, 579, 635
ROSENTHAL, muscle, absolute force, 47
muscle, current, 75
physiology, 94
nerve conduction, 198, 205
temperature, 218
spinal inhibition, 321
reflexes, 357
ROSSBACH, muscle elasticity, 87
Rossi, cerebellar ablation, 483
cerebellum, 485
ROTHMANN, cerebellar lesions, 481, 485
cortex cerebri, 634
decerebrate dog, 509, 525
ROUSSELOT, phonetics, 173
664
PHYSIOLOGY
ROUSSY, optic thalami, 521, 525
ROVIGHI, cortex, drugs, 579
epilepsy, 635
RUDINGKU, cerebrum, iutellect, 624
RUMPELT, phonetics, 173
RUSSELL, RISIEN, cerebellum, 484
ablation, 482
disease, 459
spinal metamerism, 302, 356
VAN RYNBERK, cerebellar localisation,
479, 485
dermatomes, 306
skin fields, 303
spinal metamerism, 303, 306, 356
SABBATINI, cortex cerebri, calcium, 275
SACHS, caudate nucleus, 597
mid-brain, 525
myelogenetic areas, 617
visual area, 609
SALOMONSON, high frequency excitation,
19
SAMELSOHN, macular bundle, 493
SAMUEL, nerve section, 335
SAMWAYS, core model, 257
SANDERS-BUN, grey matter, 263
SANDERSON, BURDON, muscle current,
77
latency, 9
SANKEY, cerebellum, 425
SANTESSON, muscle, work, 15
SANTINI, cortex, drugs, 579
epilepsy, 635
SAPPEY, cerebellar peduncles, 388
cerebellum, 422
laryngeal nerves, 140
vagus, 393
SAROKIN, muscle creatine, 38
SAUBERSCHWARTZ, vowels, 163
DE SAUVAGES, neural activity, 255
SCAFFIDI, sympathetic origin, 367
SCARPA, ganglion, 405
spinal roots, 301
vagus, 392
SCHAFER, auditory area, 612
cerebellum, 423
chromatolysis, 269
cortex, man, 591
monkey, 552
sensation, 587
cortical rhythm, 562
epilepsy, 577
fourth ventricle, 389
localisation, 634
mesencephalon, 487, 488
muscle contraction, 30
sound, 21
pons, 421
spinal convulsions, 581
visual area, 606
SCHECH, spinal accessory, 395
SCHENK, muscle, fatigue, 58, 95
SCHEVEN, patellar reflex, 326, 327
SCHIFF, aesthesodic nerve-fibres, 256
bulb, 418
cerebellum, 431, 433, 484
cortex cerebri, 546
circulation, 571
idio-muscular contraction, 5, 24
nerve conduction, 193
fatigue, 226
section, 332, 334
thermogenesis, 207
spinal accessory, 394
cord, 290, 357
hemisection, 344, 357
nerve roots, 292, 295, 356
taste, 403
vagotomy, 398
vagus, 396
SCHIFFER, muscle, circulation, 5
SCHIPILOFF, C., myosin, 37
SCHMIDT, muscle, R.Q., 42
SCHMIEDEBERG, alcohol, 450
SCHNEEBELI, voice, 173
SCHON, nerve degeneration, 233
SCHOPS, spinal cord, 343
SCHRADER, brain, frog, 497
lesion, 503
mid-brain, 524
SCHULTZ, pupil, 375
quasi-reflexes, 375
SCHULTZE, M., ganglion cells, 183
nerve, autogenesis, 236
SCHUSTER, localisation, gibbon, 635
SCHWALBE, bulb, 387
neurotibrils, 184
pons, 420
SCHWAMMERDAM, muscle, contraction,
21
SCHWANN, nerve conduction, 198
SCHWOHN, corpus striatum, 596
SCIAMANNA, frontal lobe, 620
knee-jerk, 327, 357
localisation, man, 557
SCOTT, nerve-cells, 277
SCRIPTURE, speech, 173, 174
SCZELKOW, muscle, R. Q., 42
SEEMANN, muscle twitch, 16
SELLIEK, corpus striatum, 597
SEMI-MEYER, neurofibrils, 188
SEMON, glottis, 142
voice, 173
SENFTLEBEN, trophic action of ganglia,
331
SEPPILLI, auditory area, 611
corpus striatum, 596
cortex, man, 591
localisation, 634
sensation, 588
vision, 600
epilepsy, 635
SERGI, cerebellar lesion, 435, 447,
484
cortex cerebri, curare, 552
frontal lobe, 624
INDEX OF AUTHORS
665
SKI; R us, cerebi'llum, 431
corpora quadrigemina, 516
SKTSCHKNOW, inhibition of reflexes,
319, 356
optic lobes, 512
SKWAI.L, superposition of contractions,
18
SimiiiKi, corpora quadrigemina, 515
corpus stria turn, 597
mid-brain, 525
SiiATTurK, brain, 530
SHKRRINUTON, cortex, secretion, 574
cortical excitation, 560
inhibition, 568
localisation, 555, 634, 635
decerebrate rigidity, 518
dorsal roots, 298
facilitation, 321
inhibition, 320, 357
integrative action, 485
knee-jerk, 329, 330
localisation, 634
metamerism, 301
mid-brain, 525
phonation, 517
pyramidal tract, 342
rami communicantes, 366
reciprocal innervation, 320, 357, 569
shock, 312
spinal cord, 289, 290
metamerism, 302, 356
nerves, 295, 356
preparation, 357
reflexes, 313, 315, 320, 357
tonus, 357
stepping, 128, 358
SIEVEKS, voice, 173
SINGER, optic decussation, 493
spinal nerves, 295
SINITZIN, Gasserian ganglion, 331
spinal cord, 357
SKABIT.SCHEWSKI, bladder, 373
SMITH, MEADE, muscle heat, 62
SMELLEN, nerve section, 334
vagus, 397
SNYDER, knee-jerk, 358
SOKOWIN, bladder, 373
SOLLMANN, vasomotor centre, 418
SOLVAY, muscle efficiency, 89
SO.MMEU, rigor mortis, 36
SUMMERING, brain, 540
spinal roots, 301
SORIENTE, epilepsy, 635
SOURY, brain, 538, 633
cerebral localisation, 546
SOWTOX, reflex inhibition, 358
SPALLANZANI, embrace reflex, 311
SPALLITTA, trophic action of ganglia,
331, 357
SPENCER, W. G., cortex, inspiration,
571
SPILLER, cortex, man, 592
SPIRO, muscle, lactic acid, 40
SPITZKA, pyramidal tract, 342
SPURZHEIM, phrenology, 542
STANNIUS, spinal nerve roots, 292
taste, 401
STARR, ALLEN, segmental limb fields,
304
STEFANI, cerebellum, equilibration,
461, 484
labyrinth, 463
optic lobes, 515
STEINACH, spinal nerves, 293
unipolar nerve cell, 261
STEINBRUCK, nerve conduction, 198
nerve degeneration, 233
STEINER, amphioxus, 495
metameres, 380
brain, fish, 496, 497
contraction wave, 24
mid-brain, 524
posture, 414
STENSEN, N., muscle, circulation, 5
STENSON, nerve centres, anaemia, 266
STERN, muscle sound, 21
STEWARD, vagotomy, 400
STILLING, cerebellum, 426
dorsal roots, 298
pons, 420
spinal accessory, 395
cord, 343
nerves, 356
nucleus, 283
STINTZINQ, muscle gases, 41
STIRLING, summation of stimuli, 263
tetanus, 18
STUHR, sympathetic ganglia, 362
STORX, phonetics, 173
STRICKER, vasodilatators, 293
STROBE, nerve, regeneration, 234
STRUMPELL, spinal degeneration, 287
SVAN, corpora quadrigemina, 515
optic thalamus, 521
SWEET, phonetics, 173
SZIMANOWSKY, glottis, 145
SZYMONOWICZ, muscle fibre, 27
TAMBURINI, auditory area, 611
corpus striatum, 595
cortex, sensory-motor function, 589
vision, 599
cortical excitation, 560
lesion, 582
localisation, 634
epilepsy, 575
localisation, dog, 548
speech, 634
TANZI, memory, 632
TARCHANOFF, cortex, heart, 574
optic lobes, 512
spinal reflexes, 337
TARULLI, spinal nerves, 295
TECHMER, phonetics, 173
TENNER, bulbar convulsions, 412
TENON, capsule, 363
666
PHYSIOLOGY
TERENCE, soul and brain, 542
TESLA, high-frequency excitation, 19
TESTUT, mesencephalon, 491
optic nerve, 494
thalamencephalon, 492
THANE, facial nerve, 407
eighth nerve, 406
THAUSING, voice, 173
THIERNESSE, nerve conduction, 198
THORNER, W., nerve excitability, 276
THOMAS, cerebellar tracts, 428, 429, 484
cerebellum, equilibration, 461
THOMPSON, spinal cord, 358
THOMSON, ALLEN, brain, 382, 383
nerves, 279, 280
THOMSON, W., galvanometer, 71
THORBURN, spinal metamerism, 304
THUNBEUG, nerve respiration, 207, 231
TIGERSTEDT, muscle latency, 9
nerve, electrophysiology, 276
excitability, 224
tetanomotor, 221
TILLIE, nerve centres, curare, 476
TIZZONI, nerve regeneration, 235
TRAUBE, muscle, protein metabolism, 43
vagotomy, 398
TRENDELENBURG, ataxy, 299
atomy, 300
spinal nerves, 356
TIIEVES, ergograph, 57
muscle, fatigue, 52, 95
TRIPIER, cortex, man, 590
nerve, conduction, 198
sensory roots, 294, 356
TSCHAGOWETZ, bioelectricity, 258
TSCHERMAK, A., cerebral localisation,
634
vision, dog, 602
TURCK, spinal metamerism, 301
tract, 287
TURNER, cerebellum, 484
mid-brain, 525
restiform body, 428
visual area, 608
UCHTOMSKY, cortex, 634
v. UEXKULL, mechanical excitor, 221
velocity of nerve impulse, 204
UNVERRICHT, epilepsy, 575, 578, 634
v. URBANTSCHITSCH, taste, 404
USPENSKY, nerve roots, 297
VALENTIN, corpora quadrigemina, 514
spinal cord, 343
taste, 401
thermal stimulus, 218
VALLI, muscle electricity, 68
nerve section, 232
VALSALVA, vagotomy, 398
VANLAIR, nerve, regeneration, 234
vagotomy, 398
DE VARIGNY, cortex cerebri, 561
VEJAS, spinal nerves, 295
VAN DER VELDE, velocity of nerve
impulse, 204
VERATTI, nerve-cells, 180
neuroh'brils, 186
VERGER, corpus striatum, 597
VERWORN, contraction, 94, 95
hypnosis, 518
muscle work, 44
nerve activity, 259
centres, 270, 276
reciprocal innervation, 320
spinal reflexes, 357
unipolar nerve cell, 261
VIALET, optic chiasma, 495
visual area, 525, 608
VIERORDT, posture, 113
VINCENZONI, cerebellum, 485
VINTSCHGAU, nerve conduction, 205
VIZIOLI, epilepsy, 579
VOGT, cortex cerebri, 539
myelogenetic areas, 617
VOIT, muscle, contraction, 91
muscle, urea, 42
VOLKERS, corpora quadrigemina, 517
VOLKMANN, glossopharyngeal, 404
larynx, 395
pharynx, 405
sympathetic ganglia, 376
VOLTA, muscle electricity, 68
tetanus, 17
VULPIAN, cerebellar lesions, 433
cerebellum, 431
hypoglossal, 389
medulla oblongata, 418
muscle, heat, 59
nerve, conduction, 198
section, 332
phonation centre, 143
pontine sensibility, 416
posture, 414
vagus, 396
WAGNER, cerebellum, 431, 484
laryngeal nerves, 395
spinal nerve roots, 292
sulci, intellect, 624
taste, 401
WALDEYER, nervous system, 275
neurone, 179
WALKER, nerve roots, 291
WALLENBERG, vestibular nerve, 405
WALLER, A., nerve section, 232
spinal accessory, 394
nerve roots, 295
trophic centres, 233
vagus, 396, 418
WALLER, A. D., animal electricity, 276
Bell's law, 358
cardiogram, 80
dynaniograph, 47
electrotonic currents, 242, 245
electrotonus, man, 248, 251
fatigue, 48, 227
INDEX OF AUTHOKS
667
W U.LKI:, A. D., heart, equipotential
lines, 81
knee-jerk, 327, 357
muscle, galvanogram, 78
\\ork. 46
myograph, 7
nerve, CO.,, 206
drills, 211
thermo-galvanograms, 61
WALSH, torpedo, 255
WALTER, coccygeal ganglion, 360
WAUUEN, knee-jerk, 330
W \I;I;IN<;TI»X, sensory roots, 330
DE WATTEVILLE, electrotonus, man,
248, 251
WEBER, E. H., joints, 100
muscle, 47
contraction, 21, 85
elasticity, 86
nerve, conduction, 193
temperature, 218
WEBER, E. and W., centre of gravity,
107
locomotion, 97, 127
reflexes, 319
walking, 114
WEBER, W. , sound, 144
WEDENSKY, muscle sound, 21
telephone, 77
nerve action current, 215, 276
fatigue, 226
WEISS, labyrinth, 463
muscle, glycogen, 39
veratrin, 32
nerve, axial current, 210
WELT, frontal lobe, 622
WERNICKE, sensory aphasia, 614, 634
speech centre, 625
WERTHER, muscle acidity, 40
WESTPHAL, knee-jerk, 326, 357
WHEATSTONE, vowel tones, 159
WHYTT, reflex action, 311
WICHMANN, muscle iields, 303
WIEDEMANN, galvanometer, 71
WIENER, optic lobes, 515
WILLIE, speech, disorders, 173
WILLIS, hypoglossal, 391
muscle, excitability, 3
vowel tones, 159
WILSON, optic lobes, 512
WINKLER, skin fields, 303, 306, 356
WINTEUSTEIN, muscle chemistry, 94
nerve centres, 271, 276
rigor mortis, 42
WISLICENUS, muscle metabolism, 43
WOLF, vowel sounds, 158
WOLLASTON, muscle sound, 19
WOLLENBERG, vestibular nerve, 405
WORM-MULLER, thermal currents, 76
WOROSCHILOFF, spinal cord, 283
spinal lesions, 345, 346, 357
WUNDERLICH, muscle, heat, 59
WUNDT, frontal lobe, 619
muscle, fatigue, 12
nerve, 276
opening tetanus, 25
spinal ganglion cell, 262
tetanomotor, 221
YEO, brachial plexus, 302
muscle latency, 9
visual area, 606
ZAAIJER, femur, 98
ZEDERBAUM, nerve conduction, 193, 276
ZEYNEK, nerve activity, 259
ZIEHEN, convulsions, 518
ZIEMSSEX, muscle, heat, 60
ZIM.MEUMANN, walking, 117
ZUNTZ, fatigue, food, 51
muscle, efficiency, 67
END OF VOL. Ill
Printed by R. & R. CLARK, LIMITED, Edinburgh.
HUMAN PHYSIOLOGY
By PROF. LUIGI LUCIANI
Translated by FRANCES A. WELBY. With a Preface by
Prof. J. N. LANGLEY, F.R.S.
In Five volumes. Illustrated. 8vo.
Vol. I. CIRCULATION AND RESPIRATION. iSs. net.
Vol. II. INTERNAL SECRETION — DIGESTION — EXCRETION- -THE
SKIN. iSs. net.
Vol. III. MUSCULAR AND NERVOUS SYSTEMS.
SOME PRESS OPINIONS
VOL. I
LANCET. — "We offer a hearty welcome to the work of the veteran
professor of physiology in Rome, one of the early Italian pupils of Ludwig
and the successor of Moleschott. Few men have such an all-round know-
ledge of physiology as Luigi Luciani, or so wide an outlook on physiological
problems, both in their modern and in their historical aspects. Moreover,
this treatise will introduce to English readers much of the work done by
his compatriots, which is none too well known in either England or America.
It is rather remarkable that the translation into English of such an all-round
comprehensive work should have been so long delayed. All the more,
therefore, do we congratulate Miss Welby on the successful manner in which
she has performed her work. We wish this and the succeeding volumes
every success in their English garb, and we hope that the other three
volumes will soon make their appearance."
BRITISH MEDICAL JOURNAL. — "The text-book is one which
should be read by those studying for higher examinations, and all who wish
for a literary and philosophic treatment of the subject. Luciani has the
same lucidity and charm of style which Sir Michael Foster possessed, and
his text-book fills almost exactly the place which Foster's text-book held in
English literature. Very good are the admirable historical summaries by
which each subject is introduced. . . . An excellent feature is the way he
sets forth classical experiments which prove the points he is discussing.
He writes knowing that he has breadth and room enough in his four
volumes, and owing to this his work gains enormously over the dull, un-
embroidered one-volumed text- book. The student could not have a better
introduction to physiology than Luciani's chapter on living matter.
Miss Welby has done her work very well."
SOME PRESS OPINIONS OF VOL. I.— Continued.
NA TURE. — " The arduous labour of translation has been carried out
very efficiently, the English version being clear, accurate, and eminently
readable. . . . The references to the literature of the subject appended to
the various sections of the work form a very useful feature. The editor,
Dr. M. Camis, has rendered these more complete by the addition of the
chief recent English and American physiological papers. These references
will undoubtedly offer valuable guidance to senior students of physiology
desirous of extending their knowledge of physiology beyond the limits of
their text-books. . . . The book is a remarkable achievement, especially in
view of the fact that it is the work of a single author, and appears to the
reviewer to possess special qualities and merits, which entitle it to a high
place amongst the existing English text-books of physiology."
VOL. II
BRITISH MEDICAL JOURNAL.—" Luciani is especially valuable
in giving the student admirable summaries of the history of the science,
and he writes with a philosophic grace and literary style such as Michael
Foster possessed, and which Miss Welby renders into English very well
indeed. . . . We cordially recommend the perusal of this volume to those
who are studying physiology with other aims than the passing of examina-
tion papers."
LANCET. — " The orderly statement of facts and theories with reference
to digestion are most excellent, and the same may be said as regards the
functional processes of the kidneys and the skin. . . . We feel sure that
this volume will be welcomed by English physiologists and practitioners of
medicine, as well as by students who are in pursuit of knowledge carefully
sifted and pleasantly presented. The translation does Miss Welby much
credit."
EDINBURGH MEDICAL JOURNAL.— " The various problems
are discussed in a critical and judicial manner, and the growth of know-
ledge in each department is set forth in a fashion which brings clearly
before the reader the way whereby our present-day opinions have been
elaborated and matured. The text is thoroughly up-to-date in each section
of the treatise, and presents the views of the learned writer in excellent
idiomatic English. The volume is a further instalment of a work that should
be in the hands of every one who is interested in the science of physiology."
NATURE. — "The important character of Prof. Luciani's text-book
was well recognised by English readers when the translation of the first
volume made its appearance. The second volume, which has just been
issued, confirms this impression. The subject-matter is treated, as a rule,
in an interesting way, pros and cons on disputed points are discussed
intelligently, and the work of past researchers, though in the main chiefly
interesting to the historian, is presented with great fulness and lucidity.
The book will prove a valuable asset to the professed physiologist and to
the advanced student."
LONDON : MACMILLAN AND CO., LTD.
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