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STUDIES IN NEUROLOGY

PUBLISHED BY THE JOINT COMMITTEE OF

HENRY FROWDE AND HODDER & STOUGHTON

17 WARWICK SQUARE, NEWGATE STREET,

LONDON, E.C. 4

STUDIES IN NEUROLOGY

HENRY HEAD, M.D., F.R.S.

IN CONJUNCTION WITH

W. H. R. RIVERS, M.D., F.R.S. JAMES SHERREN, F.R.C.S.

GORDON HOLMES, M.D., C.M.G. THEODORE THOMPSON, M.D.

GEORGE RIDDOCH, M.D.

IN TWO VOLUMES
VOL. I

HENRY FROWDE

OXFORD UNIVERSITY PRESS

LONDON

HODDER k STOUGHTON, Ltd.

WARWICK SQUARE, E.G. 4
1920

PRINTED IN GREAT BRITAIN BY RICHARD CLAY AND SONS, LTD.,
BRUNSWICK STREET, STAMFORD STREET, S.E. 1, AND BUNOAY. SUFFOLK.

PREFACE

These volumes consist mainly of a re-publication of the following
papers —

" The Afferent Nervous System from a New Aspect," by Henry Head,

W. H. R. Rivers and James Sherren {Brain, 1905, vol. xxviii. pp.

99-116).
" The Consequences of Injury to the Peripheral Nerves in Man," by

Henry Head and James Sherren {Brain, 1905, vol. xxviii. pp. 116-340).
" A Human Experiment in Nerve Division," by W. H. R. Rivers and

Henry Head {Brain, 1908, vol. xxxi. pp. 323-450).
" The Grouping of Afferent Impulses within the Spinal Cord," by Hemy

Head and Theodore Thompson {Brain, 1906, vol. xxix. pp. 537-741).
" The Automatic Bladder, Excessive Sweating and Some Other Reflex

Conditions, in Gross Injuries of the Spinal Cord," by Henry Head

and George Riddoch {Brain, 1917, vol. xl. pp. 188-263).
" Sensory Disturbances from Cerebral Lesions," by Henry Head and

Gordon Holmes {Brain, 1911-12, vol. xxxiv. pp. 102-271).
" Sensation and the Cerebral Cortex," by Hemy Head {Brain, 1918,

vol. xU. pp. 57-253).

It was thought better to make no material change in theii' arrangement ;
for each of them deals with a definite theme and is concerned with some
distinct aspect of the functions of the nervous system.

Each of these papers contained a short accoimt of the methods employed
in testing sensation ; these I have excised and written a fresh chapter in which
they are combined. I have also added an Introduction and an Epilogue
dealing with the common aims which underlie these various researches.

Finally, some of the most serious criticisms of our researches on the
functions of the peripheral nervous system have been considered in an
Appendix at the end of the second volume.

I cannot close tliis short preface without expressing my thanks to all
those who have collaborated with me. Without their help, so generously
given, this work could not have been brought to a successful termination.

H. H.

CONTENTS

PART I— INTRODUCTION AND METHODS OF EXAMINATION

CHAP. ^ PAGE

I. Introduction ............ 3

II. Methods of Examining Sensation ........ 12

(A) Spontaneous Sensations ......... 14

(B) Loss of Sensation . . . . . . . . . .15

(1) Touch . 15

(a) Light Touch 15

(6) Pressure Touch ......... 17

(2) Pain 18

(a) Superficial Pain ......... 18

(b) Pressure Pain ......... 19

(3) Temperature . . . . . . . . . . ^ . 21

(4) Roughness . . . . . . . . . . .23

(5) Tickling and Scraping ......... 24

(6) Vibration 24

(7) Locahsation ........... 25

(8) The Compass Test 26

(a) Simultaneous Apphcation of Two Points . • . . .26

(b) Successive Apphcation of Two Points ..... 29
(9) Position 30

(10) Passive Movement .......... 30

(11) Appreciation of Weight ......... 32

(a) With the Hand Supported 32

(6) With the Hands Unsupported ...... 33

(12) Appreciation of Size ......... 33

(13) Appreciation of Shape in Two Dimensions ..... 33

(14) Appreciation of Form in Three Dimensions ..... 33

(15) Appreciation of Differences in Texture ...... 34

III. Clinical Application of these Methods ....... 35

(1) With Lesions of the Peripheral Nervous System ..... 35

(2) With Lesions of the Spinal Cord, Bulb, and Mid-Brain .... 39

(3) With Cerebral Lesions .......... 46

PART II— THE PERIPHERAL NERVOUS SYSTEM

THE AFFERENT NERVOUS SYSTEM FROM A NEW ASPECT . . 55

THE CONSEQUENCES OF INJURY TO THE PERIPHERAL NERVES

OF MAN 66

Nerve Supply of the Palm oe the Hand ....... 68

§ 1. Division of the Ulnar Nerve ......... 68

§ 2. Variation in the Extent of the Area supphed by the Ulnar Nerve . . 70
§ 3. Loss of Sensation produced by Division of the Ulnar Nerve, when its Dorsal

Branch remains intact ......... 73

§ 4. Division of the Median Nerve . . . . . ■ . . . .75

vii

Vlll

CHAP.

11.

III.

IV.

VI.

VII.

VIII.

IX.

XI.

XII.

XIII.

XIV.

XV.

XVI.

CONTENTS

§ 6. Variation in the Extent of the Area supplied by the Median Nerve
§ 6. Division of both Median and Ulnar Nerves

Recovery of Sensation after Division of the Nerves of the Hand
§ 1. General Statement of the Phenomena of Recovery
§ 2. Recovery after Division of Particular Nerves

(A) Median Nerve ....

{B) Uhiar Nerve

(D) Summary .....

Recovery of Sensation after Incomplete Division of the Nerves of the
Hand ........

Nerve Supply of the Forearm .
§ 1. The Post-axial HaK of the Forearm
§ 2. The Pre-axial Half of the Forearm

Injuries to the Brachial Plexus

Loss of Sensation in the Arm from Division of Posterior Nerve Roots

Nerve Supply of the Lower Limb ......

§ 1. The Sole of the Foot

§ 2. Loss of Sensation produced by Injury to the Nerves of the Leg
§ 3. The Nerve Supply of the Leg deduced from Residual Sensibility

Deep Sensibility .

Sensations of Heat and Cold

The Compass Test.

Sensibility op the Hairs

Hyperalgesia

Changes in the Skin associated with Injuries to Peripheral Nerves

Changes in the Nails associated with Nerve Injuries

Paralysis and other Muscular Changes .....

Theoretical ..........

Description of some Illustrative Cases .....

PAGE

81
81
87
88
92
96
97

106
107
108

115

122

126
126
128
133

137

144

148

156

160

165

175

184

189

201

A HUMAN EXPERIMENT IN NERVE DIVISION

I. History of the Case 225

II. Conditions of Examination .......... 242

III. The Phenomena of Deep Sensibility 246

IV. Protopathic Sensibility .......... 257

§ 1. Borders of Dissociated Sensibihty 257

§ 2. Pain 258

§ 3. Heat and Cold ........... 261

§ 4. Hair Sensibihty ........... 272

§ 5. The Sensibihty of the Glans Penis 274

V. Epicritic Sensibility , ^ .278

§ 1. Tactile Sensibihty .......... 278

§ 2. Thermal Sensibihty 280

§ 3. The Compass Test •••.....,. 283

§ 4. The Sensibihty of the Triangle .... ... 285

CONTENTS

CHAP.

VI.

VII.

VIII.

IX.

XI.

Trophic, Vasomotor, and Pilomotor Changes

§ 1. Vasomotor and Trophic Disturbances of the Skin
§ 2. The Pilomotor Reflex .

Adaptation to Heat and Cold

Localisation and Spacial DiscRUvnNATioN

Intensity

Punctate Sensibility .
§ 1. Heat- and Cold-Spots
§ 2. Pain-Spots
§ 3. Touch-Spots

General Theoretical Conclusions

§ 1. The Integration of Afferent Impulses

§ 2. Sensory and Non-Sensory Afferent Impulses

PAGE

288
288
289

292

296

306

312
313
316
319

324
324
327

PART I

INTRODUCTION AND METHODS OF EXAMINATION

VOL. I.

CHAPTER I

INTRODUCTION

This book contains a series of researches into the physiology of the nervous
system based on clinical observations. Each section of the work formed the
subject of a separate communication pubhshed at various times in Brain ;
but they have been rearranged so as to comprise an orderly sequence extending
from the peripheral nervous system to the receptive centres of the cortex.

Tlu'oughout the last eighteen years, occupied by these investigations, I
have had the inestimable advantage of collaborating with fellow -workers each
of whom was an expert in his own aspect of the subject. Any one who compares
the various portions of this book will recognise how greatly the work has gained
by this diversity of outlook, and I cannot be sufficiently grateful to my
colleagues for all they have taught me. Our observations must of necessity
contain errors ; but these would have been many times more numerous if I
had not had the assistance of their expert knowledge.

But in spite of the diversity of outlook evident in each section of this book,
certain basic principles guided us thj'oughout and served to weld its various
portions into a coherent whole. These may be summarised under the following
headings.

1. The Tests eiyiyloyed must yield Measurable Results.

Throughout we have attempted to employ tests which yielded measurable
results. In the case of the experiment on my arm this presented no difficulty ;
we adopted, with certain modifications, the methods already in current use in
the psychological laboratory. For we were not hampered by lack of time
or opportunity. A set of observations which failed on one day could be
repeated on some subsequent occasion, and multiplied almost to any extent.
We were not compelled to consider the wishes of the patient, and had no
solicitude as to his good will.

As the outcome of these elaborate experiments on my arm and with the
gradual progress of our knowledge we were able to evolve a series of tests
appUcable to the less favourable conditions of clinical research. These are
described fully in Chapter II.

The results of these tests could be expressed in measured terms ; we
eliminated as far as possible uncorroborated opinion. But no such measure-
ments in pathological states can be of any value without some comparable

4 STUDIES IN NEUROLOGY

normal standard. It is impossible to apply to any individual patient the
average data obtained by observations on healthy human beings, however
numerous. If the abnormal measm-ements are to be of any value they must
be compared with records of the same tests appHed to normal parts of the
patient liimself.

Suppose, for example, that the sensibihty of the right hand is affected;
all the recorded measurements must be compared with those obtained from
similar j)ortions of the left hand. But if we attempt to work out on the
normal hand the exact point at Avhich any test can be appreciated, the patient's
attention is exhausted before we come to the affected parts. In most cases
it is impossible to work out a true sensory threshold even over normal areas
of the body under the conditions of time and opportunity yielded by chnical
medicine.

We have, therefore, adopted the following relative standard of comparison.
A stimulus is selected which we know to be considerably above the normal
threshold for the particular part of the body under examination. This can
be appreciated without fail provided the patient possesses the usual intelHgence
and goodwill. On apj)lying the same test to the affected parts, it may reveal
more or less gross defects in sensibihty ; the strength of the stimulus is then
gradually increased until either a threshold is revealed or no series of correct
answers can be elicited by any stimulus apphcable within the conditions of
examination.

Let us take as an example of this method the use of the tactile hairs. We
know from experience that contact with a hair exerting a force of 21 grm./mm.^
(5 grra./mm.) is above the tlu-eshold for the tips of the fingers in most persons.
On the normal hand a series of such stimuh should lead to a perfect set of
answers ; this can be rapidly determined in any patient under examination,
and we then proceed to test with the same stimulus equivalent parts on the
affected side. If the answers are defective the strength of the stimulus is
increased by selecting hairs of greater bending strain until each contact is
appreciated. It may be that this condition is not reached until the test-hair
exercises a pressm-e of 70 grm./mm.^; we then know that stimuh of this
strength are necessary to evoke a constant series of answers over the affected
parts, although the normal hand is sensitive to a hair of 21 grm./mm.^

We make no attempt to obtain an absolute threshold on the normal side ;
we estabhsh a relative difference in sensibihty, and so avoid the long and
Avearisome procedure necessary for a strict psycho-physical determination.

An exactly analogous procedure is adopted for measuring the appreciation
of passive movements or the power of discriminating the two compass points.
W^e choose a stimulus which is demonstrably super-normal in each individual
patient. Then we determine by how many times its strength must be
increased to evoke a series of correct answers over affected parts. Sometimes
this is not possible, because the rephes remain imperfect even with the higher
degree of stimulation compatible with the special conditions demanded by

INTRODUCTION 5

the test. In such a case the defective sensibihty of the abnormal parts to
the strongest suitable stimulation is still more evident, and we record that
no threshold could be obtained.

The results of all sensory testing depend greatly on personal factors in the
observer. We endeavoured to obviate this source of error as far as possible
by sharing the various examinations between us. In cases of injury to
peripheral nerves or spinal cord the patient was tested by each of us in turn ;
with lesions of the liigher centres we took notes and examined alternately.

2. The Results of our Observations are recorded in Terms of the Tests

employed.

In every instance we report the results obtained by sensory examination
in terms of the tests we have employed. Such expressions as " joint sense,"
"muscle sense," " bathysesthesia," " stereo gnosis," are strictly avoided;
" deep sensibility " has been used as a general heading only to cover several
different qualities of sensation arising in subcutaneous tissues, each of which
is recorded under some particular test.

Failure to adopt this principle leads to infinite confusion. For, owing to
the regrouping of afferent impulses on their way from the periphery to the
higher receptive centres, no one of these expressions can have the same
significance at different sensory levels. Thus the term " deep sensibility,"
as commonly used, differs profoundly with lesions in various parts of the
nervous system. A peripheral injury which destroys all the cutaneous
branches to any part of the body leaves " deep sensibihty " intact. The
patient not only recognises the posture of segments of the limb and the
vibrations of a tuning-fork, but he can appreciate the tactile and painful
aspects of pressure; moreover, he can localise with accuracy the position of
the stimulated spot.

If the lesion is situated in the posterior columns of the spinal cord " deep
sensibihty " is also said to be affected; but the qualities which are lost under
these conditions do not correspond to the varieties of sensation which remain
intact after the destruction of the nerves to the sldn. The patient, it is
true, has lost the power of recognising posture, passive movement and
vibration, but retains complete appreciation of touch and pain, however
evoked.

Even such terms as "thermal anaesthesia" should be avoided when
reporting clinical observations. For, although lesions of the spinal cord may
disturb the apj)reciation of heat or of cold independently of one another,
this is not possible with lesions of the peripheral nervous system. Here
response to the grosser thermal stimuli depends on the heat- and cold-spots,
punctate end-organs which react in a strictly specific manner. These minute
sensitive areas are scattered irregularly over the surface of the body, but
cannot be affected independently by any injury to peripheral nerves.
Dissociation, when it occurs at this level, consists of a separation of the cruder,

6 STUDIES IN NEUROLOGY

more primitive aspects of thermal sensibility from the higher forms on which
depend adaptation and the power of discriminating intermediate degrees of

heat and cold.

Not one of the descriptive terms for disordered sensation commonly used
in chnical reports is free from this ambiguity. Every loss of sensibihty must,
therefore, be recorded as a function of the test employed; "light touch"
gives place to the results obtained with " tactile " and " pressure " hairs, or
some similar means of measurement. For " analgesia " we substitute the
readings of the algesimeter (" measured prick ") or the algometer (" painful
pressure "). We do not speak of " loss of thermal sensibihty," but report
the patient's capacity to react to the more extreme degrees of heat or of cold,
and his power of discriminating intermediate temperatm-es. Similar rules apply
to the recognition of measured movement, the compass test and " spot find-
ing " ; all such expressions as " topognosis " and " perception of posture and
space " must be strenuously avoided.

All our observations were recorded in terms of the tests employed ; and it
was this method alone which enabled us to study the integrative trans-
formations to which afferent impulses are subjected on their way from the
peripheral end-organs to the highest receptive centres.

3. The Cases selected for Intensive Examination must be chosen for their

Illu strative Valu e .

Throughout this work we have been occupied with disorders of function,
and more particularly with the study of changes in sensation. This cannot be
carried out by experiments on animals, in whom it is not possible to obtain
any but the crudest sensory reactions.

On the other hand, in man the lesion is not under om* control, and the
finest examples of functional dissociation occur in otherwise healthy persons ;
the extent and nature of the structm'al changes cannot be determined anatomic-
ally. In most of the cases where a complete post-mortem examination could
be carried out the patient had died from some diffuse injury or progressive
disease and, since loss of function always exceeds anatomical destruction, the
microscopical picture is no accurate reflexion of the nature and distribution
of the sensory distm^bance. Moreover, such patients are unsuited for elaborate
psycho -physical examination by the very nature of their malady.

We have been guided, therefore, by the following principles in the selection
of our cases. For intensive examination we chose those patients in whom
the lesion is either stationary or in process of recovery ; they must be wilhng,
intelligent, not addicted to alcohol in excess, or subject to epileptiform
seizures. We were also influenced in our choice by the illustrative value of the
disturbances in function. For example, in cases of Brown-Sequard paralysis
we selected more particularly those patients in whom the spacial aspects of
sensation were disturbed in one extremity, whilst the quaUtative loss was
confined to the opposite Umb ; this enabled us to study the two forms of

INTRODUCTION 7

sensibility in uncomplicated dissociation. Similar principles guided our choice
in examples of cortical and subcortical lesions.

After this laborious analysis of disordered function in patients with some
stable lesion, we were able to interpret the less satisfactory observations which
were alone possible in those who suffered from some progressive or paroxysmal
affection.

Careful selection of the examples subjected to intensive study and this dual

attitude towards the cHnical material at our disposal is necessary before we

can hope to discover the meaning of disordered functions in the nervous

system.

4. The Importance of Residual Sensibility.

Sherrington (108; first introduced a valuable means of investigating sensa-
tion, known as the method of " Residual Sensibihty." When he wanted to
determine the extent of skin supphed from the fourth thoracic root he destroyed
several roots above and several below, whilst the fourth remained intact.
This left a sensitive area in the centre of a zone of anaesthesia ; every part
that received its innervation, however slightly, from the fourth thoracic was
marked out by residual sensibility.

The value of this method and its universal importance has been strangely
overlooked by neurologists. They continue to publish reports in which the
extent of the analgesia is solemnly discussed ; but they do not seem to recognise
the importance of considering what parts still retain their sensibility. Suppose
the seventh and eighth cervical and fu'st thoracic roots have been destroyed
in man ; certain portions of the upper extremity become insensitive to prick.
But when we have carefully determined the extent of the analgesia we are
not justified in assuming that it represents the full supply of the divided nerve
roots ; the area of sensory loss corresponds solely to those parts of the limb
which they innervate exclusively. On the other hand, the upper or head-
ward border of the loss of sensation corresponds to the lower hmits of the sixth
cervical root, which is intact ; similarly the post-axial Hmits of the analgesia
mark out the upper hmits of the second thoracic. It is not the analgesia, but
the extent of the residual sensibihty that is significant in such a case.

The same principle applies to the loss of sensation produced by lesions of
the spinal cord. All the diagrams constructed to show sensory segmentation
are built up on the study of analgesia ; in each case the borders are carefully
determined and transferred to a chart as the limits of the highest segment
affected. In reahty the sensory condition should be looked at from the
opposite point of view ; the upper border of the analgesia corresponds to the
caudal extension of the lowest unaffected portion of the spinal cord. On the
other hand, the loss of sensation corresponds to those parts of the body which
are exclusively supphed from below the lesion, a matter of httle scientific
importance.

This perverted outlook is responsible for much faulty diagnosis ; for it is
more important to know what segments are still caj)able of exercising their

8 STUDIES IN NEUROLOGY

functions than to determine what parts are utterly cut off from the sensory-
receptive centres. Loss of sensation represents the negative aspect of the
picture, whilst residual sensibihty corresponds to the functions of adjacent
but intact nerve structures.

5. The Negative and Positive Aspects of a Lesion of the Nervous System.

Fifty years ago Hughlings Jackson pointed out that most lesions of the
nervous system produced both negative and positive effects ; there is not only
a loss of function, expressing the destructive activity of the process, but
positive symptoms appear owing to release of lower centres from control.
This law was accepted as an explanation of certain individual conditions, such
as the spasticity accompanying hemiplegia, but was not generally appHed to
the phenomena of disease.

From the earhest days of om- work on the peripheral nervous system we
recognised that, when the skin was deprived of certain aspects of sensibility,
the response to those that remained might become peculiarly vivid. Reaction
to a prick was abnormal and excessive ; the patient complained that it was
more painful, although measurements showed that sensibility to this form of
stimulation was considerably lessened. Tliis is not a " hyperalgesia," but a
more primitive mode of reaction, normally held in check by coincident activity
of a higher sensory mechanism, which has been set free to exert a more
powerful influence on the ultimate afferent centres.

This conception has been combated by certain critics mainly on the ground
that the conditions under which our observations were made were " patho-
logical." To many physiologists a phenomenon which can be labelled
" pathological " is banned to the limbo of medicine, with which they refuse
to have any concern. We, on the other hand, contend that these dissocia-
tions of function give the clue to the complex activities of the nervous system.

The final act of sensation can be decomposed by changing its physiological
components. The form assumed by such dissociation may resemble nothing
that has previously existed in the phylogenetic history of man ; or the change
in function may approximate to the character of some more primitive normal
activity. This is the case with high-grade protopathic sensibihty and with
sensations from the glans penis where a normal part of the body responds
to sensory stimulation exactly hke an organ endowed with deep and
protopathic sensibihty only.

There is not a section of tliis work where Jackson's law of the positive and
negative consequences of a lesion does not illuminate the phenomena under
discussion. But chnicians are reluctant to abandon their conceptions of
" irritation " and " hypersesthesia " ; they assume that a part of the body
which reacts excessively to stimulation must be in a condition of increased
sensitiveness. They cannot be persuaded to apply the doctrine of relaxed
control to the problems of sensation, although they accept it as an explanation
of certain exaggerated motor activities.

INTRODUCTION 9

6. The Difference hetiveen Irritation and Release from Control.

It must not be supposed that we deny the existence of true irritative
phenomena. These can be studied best in cases of injury to peripheral nerves,
where they form an instructive contrast to the manifestations of protopathic
release.

Take such an instance as that described on p. Ill, where the anterior
division of the external cutaneous nerve had been accidentally wounded in the
lower part of the forearm. A considerable area became intensely tender to
the point of a pin dragged lightly across the sldn ; but sensation was perfect
to all the measured tests for prick, light touch, heat and cold, and the compass
points were discriminated with equal ease on both hands. On exploration
the nerve trunk was found to be irritated by inflammatory changes and the
full distribution of its fibres was revealed as an area of tenderness accompanied
by no coincident sensory loss.

On the contrary, protopathic over -reaction is strictly Umited to parts which
have been deprived of the higher forms of sensibiUty ; after division of the
ulnar nerve it extends no further than the borders of the loss to Ught touch.
If the same nerve is irritated the tenderness may extend far beyond these
limits and occupy all those parts of the radial palm which are innervated by
pain fibres from the ulnar nerve. This is the area that remains sensitive to
prick when the median has been completely divided. Protopathic over-
reaction is one of the phenomena of dissociation due to removal of higher
control and marks out the parts wliich have been robbed of their higher sensory
functions. Irritative tenderness, on the contrary, may be accompanied by
no loss of sensibility ; it expresses the complete peripheral distribution of
the nervous mechanism that has been subjected to excitation.

Excessive sweating is another phenomenon which may be due at one time
to irritation, at another to release of spinal centres from higher control.
After gross injury to the spinal cord outbm-sts of hyperidi'osis may occur,
which corresponds to the parts below the lesion ; these are produced by an
uncontrolled response to superficial, proprioceptive or visceral stimulation.
On the other hand, the sweating may be an irritative manifestation evoked
from the central portion of the injured cord.

Irritative phenomena can occur without any other disturbance of
function ; but release from control is always signaHsed by some coincident
defect,

7. The Necessity for avoiding a ^priori Hypotheses in the Study of Sensory

Phenomena.

The study of the phenomena of sensation has been much hampered by
a priori hypotheses. The older psychologists assumed that the immediate
consequences of stimulation corresponded categorically to the various aspects
of sensation. They failed to recognise that between the impact of a

10 STUDIES IN NEUROLOGY

physical stimulus and the act of sensation lay a multitude of physiological
transformations which could not be discovered by introspection.

At the time when we began this work, most writers assumed that each
specific quality of sensation arose from stimulation of one particular group
of end-organs. The impressions so produced were supposed to be transmitted
unchanged to the appropriate cortical centres, where they evoked some single
aspect of sensation. Special receptive organs were postulated for tactile,
painful and thermal stimuU. With the discovery of the heat- and cold-spots,
and with von Frey's further development of the doctrine of punctate sensi-
bihty to include touch and pain, a sensory mechanism seemed to have been
found capable of satisfying the required conditions.

But our discovery of the functions of deep sensibihty at once destroyed
this conception of rigid paralleUsm between peripheral end-organs and receptive
centres. For we found that many sensations, usually attributed to " Ught
touch," arose from stimulation of subcutaneous tissues, when the skin was
entirely insensitive. Pain also could be evoked in the absence of all cutaneous
sensibihty.

Obviously both sensations of " touch " and of " pain " could be caused by
the excitation of at least two peripheral mechanisms apiece. We were not,
therefore, surprised to find that in the skin itself the sensory apparatus for
heat is also double ; the " heat-spots " respond, it is true, in a specific manner,
but they account for one aspect of thermal sensibihty only. An appreciation
of minor differences in w^armth and the power of adaptation to surrounding
temperatures are functions of a higher afferent mechanism.

It has long been known that the cold-spots in the sldn react to certain
degrees of heat ; 45° C. apphed strictly to one of these spots produces a definite
sensation of cold. But if the same stimulus is apphed over a wider area,
so as to include other end-organs of a different specific reaction, the sensation
is one of heat ; impulses evoked by exciting the cold-spots are inhibited in the
presence of those due to coincident stimulation of the receptive mechanism
for heat.

Evidently the afferent impressions produced by the action on the body
of some jDhysical force, such as heat, are not only multiform, but may be
incompatible with one another. Before they can underhe a single specific
aspect of sensation, they must undergo integration within the central nervous
system.

Human sense organs have been developed out of the lowhest materials;
their functions do not correspond exactly to any of the final categories of
sensation, which are the result of innumerable physiological transformations.
These changes we have attempted to follow from the periphery to the highest
receptive centres. They are of entrancing interest, because they reveal the
method by which the sensory functions of man have been evolved from the
primitive neural activities of his humbler ancestors.

We beheve that " Sensation " was originally a vague undifferentiated state,

INTRODUCTION 11

and that progress has taken place by the slow acquirement of more specific
reactions. This has occurred not only in consequence of the development of
sense organs of higher capacity, but, to an even greater extent, by increasingly
perfect integration of afferent impulses at various sensory levels. Finally,
in man sensation is a highly differentiated reaction to physiological processes
which have undergone profound transformations on their way from the
peripheral end-organs to the highest receptive centres.

CHAPTER II

METHODS OF EXAMINING SENSATION

The value of oui' work depends in great part on the trustworthiness of
the means we have employed to examine sensation. I shall therefore devote
this chapter to a description of the tests we have used and the conditions
under which they have been carried out.

All the observations on my arm and hand were made with the pre-
cautions and safeguards customary in a psychological laboratory. The
area to be explored was not extensive and time was no object; on the
shghtest sign of fatigue the examination was discontinued, and I was allowed
a period of freedom and rest.

Such conditions are impossible clinically ; and, before we set out on the
researches embodied in this work, it was necessary to develop a series of
tests which stood midway between the rough-and-ready examination of the
clinician and the elaborate observations of the psychologist in his laboratory.
Our aim was to find a set of simple tests which would yield measurable results.
We were anxious to get rid of those statements of personal opinion which
play so large a part in clinical records.

As far as possible, our observations were made in a quiet room, apart
from the hospital ward Avith its distracting sights and sounds. On the rare
occasions when this was impossible, OAving to the difficulty in transporting the
patient, his bed was carefully screened and every method adopted to secm-e
his undivided attention. Whenever the patient was in bed the parts to be
tested were exposed as little as possible. Anything that produces a " feehng
of coldness," anything that causes shivering or the appearance of " goose
skin," greatly diminishes the accuracy of the answers to most tests. A damp,
misty or foggy day is pecuHarly unfavourable for testing sensation. The
most satisfactory conditions are a warm day of early summer, or a bright,
cool mnter morning in a well-warmed room.

It is important that the patient should be free from all visceral discomfort ;
he must not be hungry or suffer from a desire to empty his bladder. The
following instance shows how potently such conditions may affect the results
of even the grossest sensory tests. Dming the examination of R. A. H.
(p. 458) it was noticed that his answers became much less accm*ate than
they had been earlier in the day ; for he failed on the right forearm in eight
out of twenty attempts to tell the head from the point of a pin. He was

METHODS OF EXAMINING SENSATION 13

then allowed to empty his bladder, and from that time made no mistakes;
his answers, which had shown much confusion, were now uniformly correct.

At first we were in the habit of bUndfolding our patients ; but in some
cases, especially of cerebral disease, this is liable to lead to a state of defective
general attention. Dm'ing the observations on my arm, I sat with my eyes
closed, as I found that this produced in me the condition most favourable
for sensory testing ; for I always answered more correctly to those tests
which required no close introspection when I did not attempt to think of
what was going on. This was also the case with many of our patients,
especially those who tended to interpret their sensations, and were particu-
larly anxious to do well in the examination. But, with those of a lower
grade of intelHgence, closing the eyes was liable to induce a condition akin
to sleep, and they might even cease to give any answer, when tested over
normal parts of the body.

The examination was therefore begun with the eyes closed ; but, if the
results showed an unexpected want of attention on the normal half of the
body, it was continued with the eyes open with the parts to be tested carefully
screened. This was particularly useful during examination of the lower
extremities ; but it is important that the patient should not be able to see
any of the manipulations of the operation or the objects with which the
tests are carried out. Some patients are more comfortable when tliis system
is adopted than if they are forced to remain for long periods with closed eyes.

Certain well-recognised rules have guided our studies. The most important
of these is to obtain the good-will and interest of the patient ; for without tliis
it cannot be hoped that the observations will be trustworthy. When attention
begins to flag, or the patient to tire, it is necessary to interrupt the examina-
tion ; for this reason we arrange that the tests demanding the greatest effort
and concentration should be made early in the sitting, and the coarser and
subjectively easier tests reserved till the later stages of the examination.

In the second place, we have always avoided anything that might, on the
one hand, suggest a response, or, on the other, confuse it. Each test was
first explained to the patient, and he was allowed to watch it in action on the
normal side. Then his eyes were closed or the part was screened, and the
examination was begun seriously.

He was requested to reply " Yes " or to give some other simple answer
appropriate to the mode of stimulation. For example, with the compass
points he said "one," "two," or j)erhaps "I don't know"; with the test
for the appreciation of passive movement his repUes were " up," " down,"
or " bending " and " straightening." No questions were asked dming the
examination. It is most important to avoid all inquiries, such as, " Did
you feel that? " " Did I prick you? " " Was that one or two points? " or
" Did I move your finger ? " etc. Once certain that the patient understands
the nature of the test, the observer must remain absolutely silent till the
examination is over. Then he may ask questions as to what the patient

14 STUDIES IN NEUROLOGY

thinks about his sensations and the difference between normal and abnormal
parts. In many cases it is necessary to obtain an introspective description
or analysis of the sensations evoked; but we have attempted to keep this
portion of our notes strictly separate from the records obtained with the
various measm'able tests.

Our aim has been to employ a series of tests which give measurable
results without at the same time exhausting the patient, or demanding any
but the smallest amount of introspection. The measurements so obtained
are not compared mth an absolute standard, but mth the results yielded
by the same tests on the normal half of the patient under identical conditions.
Even on the normal side we do not attempt, in most instances, to discover
the true threshold. We begin each series of observations on the unaffected
half of the body with a test near the threshold value, but well mtliin the
patient's capacity. The abnormal parts are then examined \^dth the same
test, and, if a perfect series of answers cannot be obtained, the stimulus is
increased until a threshold is reached, or, if tliis is not possible, until the
task is at least many times easier than is necessary on the normal side. Thus,
all our measurements are comparative, and each case yields its own standard.
Otherwise such tests as the compasses, recognition of relative weight and
size, and all attempts to estimate painful stimuli, are useless and fallacious
for observations on the sick.

Sometimes, especially mth lesions of the spinal cord, the opposite extremity
to that mainly affected was also in a condition of abnormal sensibihty, and
it was impossible to obtain a standard for comparison from equivalent parts
of the body. Under these circumstances we were obHged to compare the
abnormal records with those from the hand or arm ; such results must,
however, be used with caution. No attention should be paid to the small
variations in accuracy of response, and we have considered large differences
only.

A. — Spontaneous Sensations

The examination was begun by obtaining from the patient a description
of any abnormal sensations he may experience in the affected parts, such as
pain, numbness or tingling. As these terms may imply in ordinary phi'aseology
very different conditions, it is necessary to determine as exactly as possible
in what sense they are used by the patient. " Numbness " may signify a
" loss of feeUng," or it may be used to describe, not a loss of function, but
a positive abnormal sensation. Sometimes it may even signify inabiUty to
make delicate movements, especially in the fingers.

When spontaneous sensations exist, it is important to ascertain the con-
ditions under which they occur, whether they are constant, and if they are
aggravated by any external agent, such as contact, heat or cold.

We are accustomed to inquire if the patient has noticed at any time that
he is unaware of the position in which the affected limbs lie, and if he

METHODS OF EXAMINING SENSATION 15

preserves an idea or mental picture of the limb. Many patients with cerebral
lesions complain that when they wake at night they do not know where the
arm is lying, and it sometimes seems as if part of the Umb, such as the hand,
had disajipeared.

In cases of injury to the spinal cord the patient not uncommonly has an
idea that his legs are in some definite position, although he is entirety
insensitive below the waist. This illusory posture may not be constant, but
may come and go, or change its direction at different periods in the course of
the illness.

B. — Loss OF Sensation

1. Touch.

{a) Light touch is always examined first by applying a wisp of fine cotton
wool gently to the skin, so that it does not produce gross pressure or deformation
of structure. But this test must be used with extreme caution. Many brands
of cotton wool, when rolled into a wisp, form so stiff a mass that sensations
of pressure are evoked ; or, on the contrary, the finer quahty of cotton wool
may fail to act as a stimulus to the horny palm of a workman, or even to
some parts of a normal well-kept hand.

Over hair-clad parts cotton wool is not a specific stimulus, but excites
both protopathic and epicritic sensibiUty. After complete division and suture
of a peripheral nerve, the affected area, if covered with hair, not uncommonly
regains its sensibiHty to contacts with cotton wool in a few weeks. But when
the hairs are removed by shaving, the sldn is found to be insensitive, and
may remain so for many months. This double tactile innervation of the
skin of hair-clad parts is particularly hable to lead to fallacious conclusions
in cases such as injury to the ulnar nerve ; it may seem as if sensibihty to
light touch had returned to the dorsal aspect of the hand, and yet after
careful shaving this area is found to be entirely insensitive to cotton wool.
This factor also played a great part in the sensations I experienced during
the recovery of my arm, which are fully described on p. 272.

In cases of thalamic over -reaction cotton wool produces over hair-clad
parts a peculiar sensation which has nothing to do with the sensory activities
of the cortex. It is an affective response, which may take the form, on the
one hand, of pleasurable " tickling," or, on the other, of uncomfortable
" itching."

We have measured the sensibiUty to Hght touch by means of von Frey's
graduated hairs ; these depend on the fact that a constant pressure is exerted
by the tip of a hair when sufficient force is used to bend it. We can arrive
at the amount of this pressure per unit area if the force exerted in bending
the hair, measured on a balance, is divided by its total area in mm.^; the
result expressed in grm./mm.^ represents the pressure per unit area.

But von Frey contends ([36] pp. 223-9), and we beUeve rightly, that
this is not a correct method of comparing the value of different hairs as a

16 STUDIES IN NEUROLOGY

measure of light touch. For this purpose he divides the pressure in milU-
grammes by the radius of a circle of the same area as the elUptical cross-
section of the hair. The result expressed in grm./mm. represents the tension
of the hair.^

Throughout the observations on my arm we were careful to bear this
difference in mind, not only in the pressm'e exerted per unit area given in
grm./mm.2, but the hair is also spoken of as "No. 3," "No. 6," etc., which
expresses the tension in grm./mm. For cUnical purposes these refinements
are unnecessary, and, whenever the tactile hairs are employed in pathological
cases, the measiu-ements are recorded in grm./mm. 2, the pressure per unit
area.

In the following table we give the necessary data for determining the
force exerted by the battery of test hairs we have used in our researches.
But it is unnecessary for the cHnical observer to provide himself with many
hairs ; those exercising a pressure of about 14, 21, 23, 35, 70 and 100 grm./mm.'^
are sufhcient for practical work. Of these the fu'st is useful for testing tactile
sensibihty on such parts as the palmar aspect of the fingers. Hairless parts,
such as the palm and sole of the foot, which respond to cotton wool, will
usually be found to be sensitive to a hair of 21 grm./mm. 2. If cutaneous
sensibility is completely absent, but the deep parts remain highly sensitive,
they may respond to a hair of from 23 to 35 grm./mm.^, which is well above
the threshold for light touch over normal areas. ^

A lesion of the cerebral cortex may produce a peculiar uncertainty in the
response to measured tactile stimuh ; the patient may be able to appreciate
the contact of a certain hair at one time, but not at another. This is not
confined to a small range of difference in the pressure exerted per unit area,
as is the case with normal sensibihty ; but the uncertain responses may be
equally evident with 21 and 100 grm./mm.^. In such cases sixteen contacts
with the same hair were made in one minute ; this rate allowed us to vary
the intervals between any two touches, so as to avoid the tendency to rhythmical
replies, so common over areas of defective sensibihty. On the affected side,
the first hair selected is one which can be easily appreciated over similar
normal parts ; then harr after hau' of increasing strength is apphed, at a rate

^ Thus on the following table the hah's which have a tension ot 4 grm./mm. and 5 grm./mm.
both happen to exercise a pressure per unit area oi i!l grm./mm.^; and yet, from the pouit ot
view of tactile sensibihty, 5 grm./mm. is undoubtedly a stronger stimulus.

^ The actual hairs we have used were made for us by Professor von Frey. They are kept
in a metal box with the handles supported on a rack, so that the hair remains entirely free
from contact when at rest. The force required to bend them vanes according to use and
to the condition of the atmosphere; but, at the end of six years' continuous work, 14 grm./mm.-
tumed the scale at 0-21 grm., 21 grm./mm.- at 0-32 grm. and 23 grm./mm.- at a little over
0-8 grm. We wish to protest against a common variation of von Frey's apparatus, which
consists of a single hair in a metal sheath, so arranged that it can be protruded or withdrawn
to a varying extent. The condition of such a hair changes greatly, and the pressure necessary
to bend it varies from time to time, even when it is extruded from its sheath to the same amount.
Moreover, in order that the hair may not suffer by the extension and withdrawal, it must of
necessity be thicker and coarser than when the test is made with a set of hairs, each
permanently affixed to its own handle.

METHODS OF EXAMINING SENSATION

of sixteen times in the minute, until either the maximum tlireshold is passed
or the strongest purely tactile hair is reached. Frequently we then go back-
wards to the hair with which the testing began. No word is spoken throughout
such a series of tests, which always end with a final set of contacts on the
normal parts. This is necessary in order to be certain that the patient's
general powers of attention have not deteriorated during the course of the
examination.

Each correct answer is recorded by a vertical stroke and failure to reply
by an 0; hallucinatory responses, if they occur, are marked by a broken
stroke. From such a record the proportion of correct answers, and the order
in which they occurred, can be studied at leisure ; thus the condition of tactile
sensibility is not a matter of unsupported personal opinion.

Pressure in
grammes.

Measured radii
in M-

Total area
in mm. 2

Radius of a

circle of the

same area in /u..

Pressure per unit
area.

Tension.

0-4

0-005

8 grm./mm ^

1 grm./mm.

0-1

47-

5 X

57-5

0-0085 ,

■ 12 grm./inm.^

2 grm./mm.

0-21

0-015

14 grm./mm.^

3 grm./mm.

0-23

0-011

21 grm./mm. 2

4 grm./mm.

0-30

0-017

73-5

21 grm./mm.^

5 grm./mm.

0-8S

100

120

0-0377

110

23 urm./mm.2

8 grmi./mm.

1-4

100

130

0-041

114

35 grm./mm.^

12 grm./mm.

1-8

115

125

0-045

120

40 grm./mm.^

15 grm./mm.

115

0-042

115

70 grm./mm. 2

26 grm./mm.

3-6

100

130

0-041

114

90 grm./mm.^

32 grm./mm.

3-5

140

0-035

110

100 grm./mm. 2

32 grm./mm.

Hairs exciting a pressure of more than 100 grm./mm.^ usually cause a
sensation of pricldng, and we have therefore avoided their use in all observa-
tions on tactile sensibility. But those ranging from 70 grm./mm.^ up to
260 grm./mm. 2 are sometimes useful as a measure of cutaneous painful
sensibility.

A camel's-hair brush is not a satisfactory method of testing Ught touch.
For, in the case of my hand, we were able to show that whether a sensation
was or was not elicited by such a stimulus, when the skin was entirely
insensitive, depended on the way in which the brush was used. If apjDhed
suddenly and vertically to the sldn, so as to cause a jarring contact, a shght
sensation of touch was produced ; but when the pressure was made more
gradually no sensation was evoked until distinct deformation of the brush
occurred ; even with these precautions it required slight pressure only to
cause a sensation. Thus a camel's-hair brush stimulates both the cutaneous
and deep sense organs, and cannot be considered as a test for superficial or
Hght touch.

(6) Pressure touch can be roughly tested by means of some blunt object,
such as the unsharpened end of a pencil or the pulp of the observer's finger,
so long as its surface temperature does not differ widely from that of the
part to be examined.

VOL. I. c

STUDIES IN NEUROLOGY

B--

For the determination of the threshold for pressure-touch we have
employed a simple form of pressure-sesthesiometer (fig. 1). This consists
of a vulcanite cyUnder (A), pierced in its length to allow a thin steel rod
(B) to move freely in it. Each end of this rod projects
some distance beyond the ends of the cyHnder ; one end
is pointed and shod with a cork or vulcanite disc 3 mm.
in diameter (F), which we have adopted as a standard area,
wliile near the other end there is a small platform (C) on
wliich weights, pierced in their centre, may rest. The weight
of the steel rod with the contact disc is 2 grm., and this is
consequently the pressure which falls on the sldn when the
unloaded instrument is brought vertically in contact with it ;
but by adding weights this pressure can be increased up to
50 grm. or more if necessary. The instrument is held by
the vulcanite cyUnder and the cork disc is brought gently in
contact with the part to be tested ; then by depressing the
cyhnder the desired weight falls on the surface. The instru-
ment is simple, and suffers only from the disadvantage that
it must be used vertically. The minimal pressm'e that can
be apphed by it is necessarily liigh, owing to the weight of
the steel rod, and is about 2 grm. This pressure on a 3 mm.
disc can be always and constantly appreciated on normal
parts, and the instrument is consequently of use only after
@F tests with von Frey's hair or cotton wool have shown that
there is an alteration of tactile sensibility.
•^^^" ^" In attempting to determine a threshold with this aesthesio-

^sthesLmeter. meter we adopt the procedure described for von Frey's hairs,
beginning with a low pressure and increasing after each series
of contacts until a weight is reached with which the sixteen successive contacts
in one minute can be appreciated.

2. Pain.

(a) Superficial pain. — Sensibility to pain may be tested first by pricking
with a sharp steel pin or needle ; the reaction to the prick should be observed,
and the patient asked to compare the sensations he experiences when normal
and affected parts are pricked in close succession. It must be remembered
that even in this simple test there is a danger of confusion, as the contact
of a point, in addition to evoking pain, gives an idea of " sharpness " due
to the appreciation of the relative smallness of the stimulating object.
Consequently, if the powder of recognising relative size is disturbed, the prick
of a pin may be described as " less sharp " on the abnormal parts, although
the pain evoked may be as great, or even greater, than on the normal side.
It is therefore necessary to ensure that the patient distinguishes between the
sharpness of the stimulus and the pain of soreness it produces. Unhappily,

METHODS OF EXAMINING SENSATION

D -.

...a

this is often difficult, and care must be taken to guard against this source
of error before deciding that sensibility to pain is disturbed solely on the
ground that pricks are described as " less sharp " than over normal parts.

If the loss is sHght, it becomes necessary to determine the threshold for
pain. We have consequently employed, as a rule, a simple form of spring
algesimeter (fig. 2). It consists of a metal tube (A) about 15 cm. in length,
closed at one end and containing at the other a piece of vulcanite (B), flattened
at its projecting end and perforated to allow the projection of a needle (C).
The tube contains a fine steel rod, to one end of which this needle is attached.
A fine spiral spring is fixed to the blunt end of this rod, and
the other end of the spring is inserted into a small bar (F)
which projects into the tube through a slit (a ... 6) in one
side of it, and is carried on a collar (E) that runs on the outer
side of the tube. The spring is so arranged that it exerts no
traction on the needle when the collar is at the highest point
of the slit, and if the instrument is then appHed vertically the
point of the needle bears its own weight only. If, however,
the collar is sHd down towards the point of the needle tension
is put on the spring and exerts a corresponding pressure on the
needle. By measuring this on a balance the instrument can be
graduated according to the pressure in grammes exerted on
the needle, when the collar stands at different points of the
scale. An instrument graded between 2 grm. and 10 grm. is
sufficient for ordinary cHnical purposes. When it is used
horizontally, or wdth the point upwards, these values vary
according to the weight of the needle, but this variation can be
easily calculated. When, however, as in our work, it is sought
to obtain a relative or comparative rather than an absolute
threshold, this is unessential, provided the instrument be appHed
at the same angle to the corresponding points of the two sides
of the body.

It has always been recognised that it is difficult to obtain
an accurate threshold for painful prick ; for if a pin be apphed
with the same moderate pressure twice in succession to the same part, one
contact may be appreciated as pain and the other as touch, depending largely
on whether a pain-spot is directly stimulated or not. We consequently apply
the algesimeter a certain number of times in close succession to the part to
be examined, asking the patient to say whether he appreciates a prick or
merely a touch, and take the reply for this series of stimulations instead of for
each individual one.

We have found the interrupted current an unsatisfactory means of
measuring sensibihty to pain, and have not used it systematically in those
researches,

(6) Pressure pain. — Whenever pressure is appreciated after division of a

-U

B-

Fig. 2.

The Spring
Algesimeter.

STUDIES IN NEUROLOGY

peripheral nerve to the skin, its steady increase leads to the production of
pain. But when the lesion is situated within the spinal cord, this is not
the case, and it is therefore necessary to have some means of measuring the
amount of pressure capable of causing pain. For this purpose we have used
a modification of Cattell's algometer suggested by Dr. Rivers. The end of

the instrument is placed on the
part to be tested, and pressure is
exerted on the round knob which
fits into the palm of the observer's
hand. This compresses a spring
in the handle. On the rod sUdes
a scale, which is pushed down as
the shaft is driven upwards by
the increasing pressure (fig. 3).

Immediately the patient calls
out that the pressure has become
painful, the instrument is removed,
the rod springs out of the handle
again, carrying with it the scale,
which remains at the point where
the rod emerged from the handle
at the moment of maximum pres-
sure reached during that observa-
tion. A Une di'awn round the rod
acts as an indicator, and the
amount of pressure applied can be
read off at leisure from the relation
of this Une to the measure on the
scale, which is graduated in kilo-
grams.

A B ^Yg have found an algometer

. ^, , , ' ' ^, , constructed on these principles

A. — fellows the algometer before use. ilie zero oi t n • t«>

the scale corresponds to the horizontal line on the rod. satisfactory. It will glve different

B.— Shows the algometer after use. The horizontal ,.p„fli^o-s; in the hands of each
line on the rod now corresponds to 10 divisions on leaomgh m ine nanas OI eacn

the scale. At this point the patient complained that observer according to variations
the pressure caused pain. The graduations correspond . ,, i ■ t. -ii

to kilograms. ^ o in the manner and rapidity with

which it is apphed. But although
the actual amount of pressure necessary to cause pain varies according to
this personal equation, a comparison of the records on the normal and
abnormal sides in the same patient shows a remarkable similarity with different
skilled observers.

At least three or more readings must be taken over every part examined,
as the answers vary considerably^ according to the state of expectation in the
patient's mind.

METHODS OF EXAMINING SENSATION 21.

3. Temperature.

Many difficulties surround the testing of sensibility to heat and cold,
particularly as minor degrees of temperature play so considerable a part in
our investigations. The use of ordinary glass test-tubes is open to serious
objection except for the coarsest observations, for the wall of the tube is
never at the same temperature as the fluid it contains. Thus, a thermometer
placed in the water does not register even approximately the actual tem-
perature applied to the patient's skin. We have therefore used flat-bottomed
silver tubes with a diameter of 1-25 cm. These tubes were filled with broken
ice, or with water at the temperature desired, and contained a thermometer.
They were never warmed or cooled from without. When used for testing
sensibility to heat, several tubes ranged in a wooden stand were filled with
water at temperatures considerably higher than those we wished to use for
testing ; from these, a tube was selected as soon as it had sunk to the
temperature required. These silver tubes lose their heat so rapidly that
it is impossible to use the same one for more than a short series of
tests.

Sometimes, when testing large areas of sensibiUty to heat or to cold
produced by lesions of the spinal cord, we have employed large copper
tubes of 4 cm. in diameter. These retain their temperature much longer
than the smaller silver tubes, and are particularly useful when we are
concerned mainly with the existence of sensibility either to heat or to cold
rather than with the exact degree of thermal stimulation ; they also form
an excellent means of evoking a thalamic over -reaction to temperature
stimuli.

It is well to remember, when testing the scalp, that the hair insulates
the skin, so that both heat and cold pass through with difficulty, and the
results are liable to be unsatisfactory.

Few difficulties attend the testing of sensibiUty to the more extreme
degrees of heat and cold. But occasionally, when the affected parts are
sensitive to painful stimuli but not to heat, a tube of 50° C. or above may
be said to be hot solely on account of the pecuUar pain produced. This is
particularly the case when sensation is returning after division of a peripheral
nerve, or with lesions of the spinal cord which destroy sensibility to heat but
not to painful stimuH. During the experiments on my arm, when tested
with these temperatures, I frequently said, " Any ordinary patient would
have called such stimuli hot, because the pain produced is of a Idnd associated
in daily life with the action of hot bodies only. Further, a patient is told
to say if he feels heat, cold, or a touch. Given, then, that he knows his
thermal sensibility is being tested, he would certainly call the sensation I
experience ' hot.' "

Occasionally contact with a neutral tube would cause an indeterminate
and somewhat tingUng sensation over the affected area; tliis was frequently

22 STUDIES IN NEUROLOGY

said to be warm, and was one of the greatest difficulties against which we had
to contend {vide p. 286).

A most distm-bing condition, famiHar to all who have investigated cases
of lesions of the spinal cord, is the tendency of the patient to call all tem-
peratm-e stimuh, whether hot or cold, by the same name. It is important,
under such circumstances, to interject frequent stimulations with a tube that
is neither hot nor cold to the normal skin. Then it may be discovered
that the neutral tube is as frequently said to be hot or cold as one which is
a positive thermal stimulus to the normal hand.

Cerebral lesions do not as a rule abohsh sensation to heat or to cold ; ice
and water at 45° C. are usually appreciated without difficulty. But such
temperatures form a ready method of applying measm-able affective stimuli,
especially in cases of the so-called " thalamic syndi'ome." Extremes of heat
and cold are uncomfortable or even painful, whilst warmth is usually distinctly
pleasant. To study this affective aspect of sensation it is generally advisable
to apply the stimulus to a larger urea, and for this purpose we have used
large copper tubes with a diameter of 4 cm. filled with water at various
temperatures.

In cases of cortical injury or disease it is important to determine the
power of distinguishing the relative warmth of two tubes, each of which is
recognised as warm. One of the most interesting defects in such cases is
the inability to appreciate mth any certainty the difference between 35° C.
and 45° C. ; and yet both are said to be warm. Sometimes the loss of dis-
crimination is less severe, but the patient cannot appreciate the difference
between 33° C. and 40° C.

Occasionally it is important to determine the threshold for heat and for
cold on similar portions of the two halves of the body ; this gives the range
of the neutral zone, which may be considerably enlarged as the result of a
cortical lesion. Tliis is frequently an extremely difficult and unsatisfactory
form of examination, for most patients possess no word which expresses a
neutral sensation. Before we begin testing with this pm"pose we therefore
suggest that the answer shall be " warm touch," " cold touch," or " nothing
but a touch." At the same time we compare the sensation evoked by the
neutral temperature with that of a distinctly warm or cold tube.

During the experiments on my hand we were much occupied with the
site and mode of reaction of the heat- and cold-spots. They are of purely
scientific interest, and can rarely be tested under chnical conditions. The
cold-spots were sought for with copper rods of about 1 mm. in diameter,
which were placed in a glass containing broken ice; on removal, each rod
was carefully wiped and, after its flat base had once been appUed to the sldn,
was returned to the ice.

For the discovery of heat-spots we used a simple method which, as far
as we can discover, has not been described before. We chose a " soldering
iron " consisting of a large copper block fixed to an iron rod let into a wooden

METHODS OF EXAMINING SENSATION 23

handle. This block, about 3 in. (7-5 cm.) in length and 1 in. (2-5 cm.) across
every face, we cut down to a pyramidal point. The apex of the pyramid
was flat and 1 mm. square. Into the copper block we bored a circular shaft
passing obUquely downwards in the direction of the point. This was of
sufficient size to contain the bulb of a thermometer, just under 1 cm. in
diameter.

Two of these irons were placed in a jug containing hot water. When
sufficiently heated, one of them was removed and di'ied ; the thermometer
was placed in the cavity and the instrument laid on a cloth until the required
temjoerature was recorded. It was then held firmly in the hand like a large
pen, and lightly applied, vertically, to the surface of the skin. So large a
block of copper retains its heat for a considerable time, and the thermometer
gives a sufficient indication of its temperatm-e. This should he between
50° C. and 40° C, preferably at about 45° C. Higher temperatures cause
distinct pain, which compUcates the observations ; a temperatm'e below 40° C,
fails to stimulate most of the heat-spots.

A low external temperature greatly increased the difficulty in discovering
both heat- and cold-spots ; and in the winter, when the affected hand seemed
numb and cold, previous immersion in warm water greatly faciUtated their
determination,

4. Roughness.

The threshold for the appreciation of roughness is most conveniently
determined by the Graham-Brown aesthesiometer. This consists of a mass of
brass with a polished surface, from which a tooth may be projected by means
of a graduated screw. The instrument is drawn firmly over the part to be
tested, and after each application the tooth is projected further until the
patient can recognise the roughness. When the threshold is normal this is
generally apparent to the observer's fingers holding the instrument at the
same time as to the patient. The tooth " rakes " the sldn, and this stimulus
is conveyed both to the observer and the sense organs of the patient, pro-
vided his sensation is normal. Throughout this work we have used the original
form of the instrument with one projection rather than that with many
projecting cylinders.

We have used for the same pm-pose emery- or glass-paper of different
degrees of roughness. We have adopted five grades, and employ as a control
a piece of smooth cardboard of the same thickness. The normal fingers,
when drawn over the rough sm'face, can recognise even the finest emery-
paper we employ as rough, and can easily distinguish the relative roughness
of any two grades. When this form of sensation is affected the finest grade
that can be recognised as rough represents the amount of the defect. This is
a useful test in cases of cerebral lesions, for by it the power of discriminating
the relative roughness of two grades tested in succession may easily be
determined.

24 STUDIES IN NEUROLOGY

5. TicMing and Scraping.

Our investigations led us to seek stimuli which are largely affective, or
which contain a considerable affective component. Apart from pain, it is
difficult to obtain a stimulus of this Idnd, but tickling unquestionably evokes
a sensation which is strongly affective and may be either pleasant or unpleasant.
The easiest method to produce tickling is to draw the pulps of the fingers
gently over the soles of the feet ; in some cases this stimulus also tickles the
palms of the hands. In certain persons a wisp of cotton wool rubbed gently
over hair-clad parts produces tickUng, especially over the pinna, on the neck
and on the hair behind the ears, although in many such a stimulus is entirely
ineffective for this purpose.

Scraping with the finger-nails is also a definite affective stimulus of the
unpleasant order, as may be seen in cases in which there is an exaggerated
response to affective stimuli. In such " thalamic " patients it may produce
an intensely unpleasant sensation.

6. Vibration.

To test the power of recognising vibration we have employed a large
tuning-fork beating 128 vibrations per second (C).

The fork, vibrating strongly, is placed on some part of the body which is
firmly supported on the bed or on a pillow. If it is normal, the patient at
once recognises the " buzzing " sensation. His eyes are closed and he is asked
to say when the vibration ceases ; as soon as he indicates that it is no longer
perceived, the fork is transferred to the corresponding portion of the other
hand. Under normal conditions the vibration usually becomes appreciable
again for a time. The period between the transference of the fork to the other
hand and the moment when its beating can no longer be recognised, is measured
with a stop-watch. In healthy individuals this may last from five up to
fifteen seconds ; but a few persons allow the fork to run down so far on its first
application that it has ceased to beat before it is transferred. Both these
modes of reaction are normal, provided the measured periods are approxi-
mately equal from right to left and from left to right. Thus it may happen
that, in one form of normal response, the records read as follows for four
observations : —

Eight to left. + 6 sec. + 4 sec.

Left to right. + 5 sec. + 4 sec.

or, according to the other mode of reaction : —

Right to left. + 0 sec. -f 0 sec.

Left to right. + Q sec. + 0 sec.

In neither instance was there any material difference between the two
hands.

METHODS OF EXAMINING SENSATION 25

A characteristic abnormal response is the following, taken from a case of
injury to the cortex : —

Thumb : —

Right to left. + 8 sec. + 9 sec.

Left to right. + 8 sec. + 7 sec.

Middle Finger : —

Right to left. + 10 sec. + 10 sec.

Left to right. + 6 sec. + 6 sec.

Little Finger : —

Right to left. + 15 sec. + 10 sec.

Left to right + 0 sec. -f 0 sec.

Here the readings from the right thumb were normal, those from the
middle finger slightly, and those from the httle finger grossly, affected.

7. Localisation.

Various methods have been described to test the faculty of locaUsation of
tactile and other stimuli on the siu^face of the body. We have experimented
with most of them, but have found a modification of Henri's method the most
suitable for cHnical purposes.

In Henri's original method the patient was required to mark on a life-sized
diagram or photograph the exact situation of the spot stimulated, while the
observer indicated on a duplicate diagram the spot he touched. Simple
though this method is, it labours under the disadvantage that many patients
find a difficult}^ in translating an image of the part tested on to a diagram
which can show onl}'' two planes of space. ^ We found that this difficulty
disappeared when the diagram was replaced by the corresponding j)art of
another individual. The part to be tested, for instance the left hand, is hidden
from the patient by a screen, wliile the left hand of one of the observers is
presented to liim, placed in a similar position to that of his own hmb. On
this Hving model of his hand the patient indicates with his other forefinger
the exact spot on which he believes he has been touched. The second observer
marks on a diagram the spot that is touched, together with the spot indicated
by the patient, and thus a permanent record is obtained. In order to point
to the spot that has been stimulated, when one hand is seriously paralysed,

^ This was by no means the case in myaelf, and in the experiment on my hand we reHed
greatly on this method. With my strong powers of visuahsation I rapidly developed what
may be called a visual map of the affected area. I had but to close my eyes to see a picture
of my hand with the affected area marked upon it as clearly as in a photograph. As soon
as a spot was stimulated, I saw its position on this map and at once described the neighbouring
landmarks. I could even give approximate measurements ; for instance, I would say that the
point stimulated lay in " the interosseous space about 1 in. from the head of the first meta-
carpal." Occasionally I was allowed to point with the index-finger of the right hand; but,
since this in itself acts as a stimulus, it should be rarely permitted and should be reserved for
special occasions.

26 STUDIES IN NEUROLOGY

the patient must usually withdraw the normal hand from behind the screen
when control observations are being made upon it.

When the loss of sensibility affects the foot, we employ an exactly analogous
method, and the errors of localisation are recorded on diagrams of the foot.
The Kving model, upon which the patient locahses the spot touched in himself,
consists either of the foot of one of the observers, or, more often, of the
corresponding lower extremity of some other patient.

Occasionally we have also used the method in which the patient names
the spot stimulated. But accurate results cannot be obtained by this method,
and it labours under the serious disadvantage that confusion frequently arises
in the terms employed to designate the different parts, such as the fingers or
their segments.^

The groping method is useless as a means of testing the power of locaUsation,
as the results obtained by it are gravely affected by any coincident distm-bance
of the power of recognising the position in space of the part tested.

8. The Com'pass Test.

{a) Simultaneous Application of Two Points. — To test the power of dis-
criminating two points we have usually employed a pair of carpenter's com-
passes, the points of wliich had been ground down until they gave no sensation
of sharpness. Most of the instruments, called " sesthesiometers," used for
this purpose are provided with points so sharp as to be wholly useless.

These large compasses are excellent for observations made in a hospital,
but they are clumsy for the daily run of clinical work. A modification,
which has been devised by Dr. Gordon Holmes, consists of two flat
triangular pieces of steel 10 cm. in length and 1-25 cm. in breadth across the
base. Each hmb ends in a rounded point which has been tmsted out of the
horizontal so that it makes an angle of roughly 45° with the axis of
the steel bar. The two Hmbs are hinged together at their broad bases so as
to form a small pair of compasses that can be carried in the waistcoat pocket.
On the flat surface of each bar, which becomes more and more exposed when
the hmbs of the compasses are separated from one another, fines are engraved
corresponding to the distance separating the points ; thus, when they are 1 cm.
apart, the edge of the flat bar corresponds to one of these lines, 2 cm. to another,
and so on, up to a distance of 10 cm.

For recording our observations we used the method suggested by McDougall
(72). The compass points were set at a certain distance from one another ;
they were then applied to the part to be tested in such a way that sometimes
two points, sometimes one point only, touched the skin. The stimufi followed
one another in an entirely ^regular order, but so that, ultimately, the patient

1 For example, the index is sometimes said to be the " first," sometimes the " second
finger ' ; the httle finger may be caUed the " fourth " or " fifth finger." The " first joint "
of a digit may be either the proximal or distal phalanx.

METHODS OF EXAMINING SENSATION 27

had been touched ten times with one point, ten times with two points. Each
correct answer was marked with a stroke, whereas a mistake was recorded
by a cross. Thus, if he answered "one" when touched with two points, a
cross was placed below the line ; if one point had been called " two," the cross
was marked above. By this method it was at once obvious in how many
instances he had answered correctly among the ten single and ten double
stimuli. The answers, whether right or wrong, were ranged in strict sequence
above and below the horizontal line.

Perfect appreciation of the compass points at a distance of 4 cm. would
be represented thus : —

. 1 I III II nil I

4 cm. H-i

nil III III

If, however, the patient was unable to differentiate the two points, answering
" one " to every stimulation, the record would stand : —

. jj im n mi

4 cm. 2 I XX XXX X xxxx

Less complete failm'e would be represented by some such formula as : —

1 I IIXX XI IXXI

4 cm.

2 I XIX IIXX XXI

In the following pages these records are sometimes translated into the
number of answers wliich were right (R.) or wrong (W.), for the sake of
simplicity.

Throughout our researches, unless expressly stated, all compass tests have
been aj^plied in the longitudinal axis of the limb.

The results obtained with this test are profoundly influenced by accessory

conditions. A stranger entering the room, or anything that disturbs the

patient's state of quiet attention, profoundly diminishes the accm^acy of his

answers. Thus in my own case on one occasion R.'s servant entered our

workroom in the middle of an almost perfect series of answers : they at once

became less accurate : —

6 cm ^1^^- ^^^-
^^ ^^- 2 I 0 R. 5 w.

After his withdraw^al I again began to answer as before : —

1 I 9 R. 1 W.

6 cm.

2 I 9 R. 1 w.

Any profound coohng of the sldn, or even the occurrence of a pilo-motor
reflex, greatly diminishes the accuracy of the answers to compass stimulation.
When the coat is removed, and the sleeve is rolled up, " goose-sldn " is fre-
quently produced ; testing should not be begun until this has entirely passed
away.

The compass points are set at a distance from one another which is just

28 STUDIES IN NEUROLOGY

above the threshold on the normal side, that is to say, at such a distance that
the patient has no difficulty in recognising the two contacts when the points
are applied simultaneously. Then the similar part on the affected half of
the body is tested in the same way, with the compass points set at the same
distance from one another. If this is found to be below the threshold, the
points are separated until a thi-eshold can be obtained, or, if this is not possible,
a record is taken with the compasses separated to a distance many times
greater than that at which a perfect reading was obtained on the normal
side.

Such was our general procedure in clinical examinations. But in the case
of my arm we were able to make more exhaustive observations, and always
began a series of tests with the compass points widely separated from one
another (9 cm.). Not uncommonly the records considerably improved as
the distance was gradually diminished, and were frequently better at 7 cm.
than at 9 cm.

This well-known phenomenon seemed, in my case, to be associated mth
the increasing detachment of attention from the procedure of testing. The
following series of records obtained from the abnormal area on the left forearm
are a good instance of such improvement : —

fi orv, M 5 R. 5 W. K ^^ 1 I 5 R. 5 W. a nrr. ^ \ 9 R. 1 W.

^ ^™- 2 I 10 R. ^ ^™- 2 I 6 R. 4 W. * ^™' 279 R. 1 W.

The improvement at 4 cm. was associated mth complete wandering of
attention from the manipulations. When at the close R. asked whether
there was anything to say about these observations, I could have beUeved
that nothing had been done. I was tliinking about a book I had been reading,
and was completely absorbed, until recalled by R.'s question.

Occasionally, especially after exercise in the open air, this condition of
detachment would pass into sleep. We noticed that the answers seemed to
imjarove up to the point at which I ceased to reply, and therefore made several
observations on the effect of somnolence on the compass records. On
October 26, 1907, I fell asleep at the close of the follomng record : —

. 1 I 7 R. 3 W.

* ^™- 2 I 7 R. 3 W.

an unusually good formula for the affected forearm. I was wakened, and after
a short interval it was found that the same distance of 4 cm. was completely
below the threshold; every double stimulation was said to be "one." I
was allowed again to settle myself in the armchair, and R. continued to test
me with the points of the compasses at the same distance. With the return
of the somnolent state the records improved; the total sixty stimulations
gave the formula : —

4 cm 1 I 21 R- 9 W.
2 I 26 R. 4 W.

METHODS OF EXAMINING SENSATION 29

but of these the first and second twenty obtained when I was more nearly
asleep were better than the last series.

4 cm

First Series. Second Series.

1 I 6 R. 4 W. 1 I 7 R. 3 W.

2 I 9 R. 1 W. 2 1 10 R.

This sleepy condition, which is so favourable for results with compasses,
is one that requires absolute freedom from all external appeal to responsible
action. It is a condition which I have never succeeded in producing sm-rounded
by the multifarious interruptions of home.

Conversely, concentration on the details of the compass test greatly
diminished the accuracy of the answers. During a large number of examina-
tions, directed towards elucidation of the phenomenon of " double ones," I
was asked to state whether the two sensations seemed to be far apart and, if
possible, to indicate the position of the two spots. This required much con-
centration of attention on the details of testing and considerably raised the
threshold.

(b) Successive Apjjlication of Two Points. — But in addition to testing the
ability to discriminate two points apj)Ued strictly simultaneously, we have
found it necessary, when dealing with sensory distui'bances from cerebral lesions,
to investigate the pow'er of recognising two points applied to the skin in close
succession. This can be carried out by bringing down first one point and,
whilst it remains in contact with the surface, rapidly placing the second point
upon the skin. Evidently, the interval of time between the successive applica-
tions must be short if the two points are to be appreciated as a double contact,
and not simply as two successive touches. The following record, obtained
from the affected forearm in a case where the power of recognising the double
nature of the compass points was lost, whether they were apphed simul-
taneously or successively, illustrates the method by which we record the
results of this test : —

im mill

15 cm. -I 2 ^1 xxxx xxxx XX

12+1 XXX xxxx XX X

Here the compass points w^ere separated by a distance of 15 cm., and the
contact of one point was recognised in every case correctly. But two points
applied simultaneously (2) or successively (2 +) were never said to be anything
but one.

If the power of localising the spot touched is unaffected, the patient wdll
retain the faculty of recognising two points applied successively, even though
he may be unable to discriminate them when brought in contact with the sldn
strictly at the same moment. A record from the finger, under such conditions,
may read as follows : —

II 1111 nil

2 cm. J 2 I XXX XX X XX XX

(2 + 1 11 nil ill 1

30 STUDIES IN NEUROLOGY

9. Position.

The power of recognising the posture of any part of the body is tested by
placing a segment of a Umb in some position and asking the patient to indicate
where it has been placed, either by description or by imitation ^vith the sound
limb. A second method is to ask him to touch with the normal hand some
definite spot, such as the tip of the index-finger or of the great toe; this
is a convenient test for knowledge of the position of the hmb as a whole,
especially if the faculty of locahsation is intact. The power to succeed in
this test may be influenced by a defect of the sense of position at any joint
of the limb.

As ability to recognise the posture of the Umb may be aided by the memory
of the passive movement by which its present position was reached, it is advis-
able to obviate this factor as far as possible. This may be done by keeping
the patient's attention diverted from the movement by conversation or
questions, and by allowing the Hmb to remain in the position to be tested for
a short time before his attention is directed to it.

A measurement of a defect in the sense of position may be obtained by the
method introduced by Horsley (56), but for this purpose it is necessary
that the opposite limb should be normal. Horsley employed a glass plate
graduated into half-centimetre squares, which could be placed, screened from
the patient's sight, in any of the three planes of space. Instead of this glass
plate, we have used a sheet of stiff cardboard, on one side of which a small depres-
sion is made to receive the tip of the index-finger of the Hmb to be tested,
while to the other side a sheet of white paper can be fastened. This card-
board is placed in any position, and the patient is required to bring the normal
index -finger towards the tip of its fellow, wliich lies on the opposite side ; the
spot on which it impinges on the paper is marked by the observer. A series
of ten successive observations is made in this way. The sheet of paper can
be then removed from the cardboard plate, and forms a permanent record
of the amount and direction of the error.

10. Passive Movement.

The power of recognising passive movement may be roughly tested by
changing the position of a segment of the Hmb and asking the patient to indicate
when he can appreciate the movement ; we then measiu-e the extent tlu-ough
which the part must be moved in order that the direction of movement can
be rightly perceived. It is always necessary to carry out control experiments
on the opposite normal Hmb.

In order to measure the angle through which a movement must be made
to be appreciated, we employ a simple instrument (fig. 4), which consists of
a long narrow plate of brass (A), fined with cloth, that can be strapped on to
any part of the Hmb by bands (B) attached to it, or held in contact with it
by the observer. At one end of this plate an arm, which carries an arc of a

METHODS OF EXAMINING SENSATION

circle witli degrees marked on it, is attached by a joint (D), movable in all
directions. Two such arcs can be adapted to this instrument, either of which
can be attached at (E) ; one (F) with a radius of 7-5 cm. for measuring move-
ments of shorter segments, as those of the fingers, and another (G) with a
radius of 15 cm. for longer segments. The brass plate is apphed to the limb
in such a way that the point (D) lies immediately over the joint at which the
movement is to be measured, and the arc is then brought into the plane of
the movement that is to be made. The range of movement necessary for
appreciation can then be easily read o& from the scale on the arc.

There are certain sources of error in obtaining such measurements. In
the first place, the patient may reply, when he feels the pressure of the observer's
fingers by which the
passive movement is
made ; but this can
be easily obviated by
grasping the part to be
moved so firmly on two
opposite surfaces that
the additional pressure
necessary to produce
the movement cannot
be distinguished. The
part should be grasped
between the fingers ap-
plied to the surfaces
that lie in the plane in
which the movement is
to be made, rather than ^'*''''''*»^ Fig 4

on the surfaces vertical r^j^^ instrument devised by Dr. Gordon Holmes to measure the

to the plane of move- extent of the smallest appreciable passive movement. The finer

. divisions of the scale are not shown upon this drawing for the sake

ment ; tor m the latter of clearness.

case the dragging and

displacement of the soft tissues may enable the patient to reply correctly,

though he cannot appreciate the actual movement.

In the second place, the rate of the passive movement may influence its
appreciation. To obviate errors from this source we have attempted to make
the movement roughly at a certain uniform rate, and, as our measm'ements
have been always considered in relation to those obtained from the opposite
sound limb, this safeguard is sufficient for clinical purposes.

Finally, in a normal limb a passive movement is appreciated, and its
direction is recognised almost simultaneously ; but, when sensibility to
passive movement is affected by a cerebral lesion, a much larger range
of movement may be required in order that the patient can obtain a
knowledge of its direction, than that which enables liim to recognise its

32 STUDIES IN NEUROLOGY

occurrence. It is therefore necessary in some cases to measui'e both
separately.

11. Appreciation of Weight.

To test the appreciation of weight we have employed circular discs of lead
3 cm. in diameter, ranging from 20 grm. to 200 grm. in weight. The sm'face
of each disc which is placed in contact with the body is covered with chamois
leather, in order to prevent the coldness of the metal affecting the sldn. Tliis
has the additional advantage that when the weights are placed one on the
top of the other they have less tendency to shp.

With these weights we carry out the following series of tests, both with
the hands fully supported and also when the patient is permitted to estimate
the relative weight by " weighing," i. e., by raising and lowering his hands.

(a) With the Hand Supported. — Two weights are placed successively on
the normal hand, and the patient is asked to say which is the heavier. With
weights, of the siu"face area we use, even the least intelligent can recognise
the difference between 70 and 100 grm., and many can give a series of right
answers with 80 and 100 grm. Two weights are found which can be correctly
distinguished on the normal hand, and they are then employed to test the
affected hand in the same way. Usuall}^ in our cases, if the power of recog-
nising weight was affected, the errors were gross, and in many instances no
pair of weights could be found which could be distinguished with certainty.
But, when the faculty of estimating relative weights was not completely lost,
we were sometimes able to work out a true difference-tlu'eshold ; that is to say,
two weights could be found bearing to one another such a relation that one
was always said to be the heavier, wliile another pair, which differed to a less
degree, could not be distinguished. At least iowc, and usually six or eight,
observations are made with each pair of weights.

Next we test the power of recognising the increase or decrease of weight.
For this purpose a thin cork disc of the same diameter as the weights is first
laid upon the palm. To this progressively heavier weights are added and
then removed until the cork alone rests upon the palm. These weights are
not added or removed in an unbroken sequence, but irregularly, and the
patient is asked to indicate whenever any alteration in weight occurs. Thus
the complete record of a series of observations might read as follows : —

Cork + 20 grm. + 40 grm. — 40 grm. + 40 grm. + 80 grm. — 80 grm. + 80 grm.
+ 100 grm. — 100 grm. — 80 grm. — 40 grm. — 20 grm.

First of all the sound hand is tested, and the patient's normal capacity
determined; then a similar series of tests is apphed to the affected hand.
When the power of recognising addition or subtraction of weight is lost, the
jarring produced by the manipulation may be appreciated ; this tactile sensa-
tion, evoked by the act of removing one weight from, or adding it to another,
is a fruitful som-ce of error, but A\ith care and practise can be reduced to a
minimum. Moreover, by gently toucliing the weight without altering it, as

METHODS OF EXAMINING SENSATION 33

it lies on the hand, we can ascertain whether the patient's replies are due to
recognition of a change in weight, or to the tactile stimulus evoked by the
manipulations of addition or removal.

Finally, the patient is asked to compare two weights placed one on each
fully supported hand.

(b) With the Hands Unsupported. — A weight is placed in each hand and
the patient is asked to " weigh " them by raising and lowering his hands.
Another method is to place a weight in one hand and then to substitute another
one for it, each weight being raised and lowered several times. In normal
persons the latter method gives the more accurate results, but our patients
often became so confused on the affected hand by the absence of a normal
standard that we have usually adopted the first form of this test.

12. Appreciation of Size.

The ability to recognise differences in size may be tested by placing in
succession two objects of different size but of the same shape in contact with
the part, and asldng the patient to distinguish which is the larger. By varying
the relative size of the objects, a threshold for this form of discrimination
can be obtained. For this purpose we employ circular ])ieces of thick leather,
increasing by half a centimetre, from 1 cm. to 4 cm. in diameter. Leather
has the advantage that it is rarely cold to the skin, and pieces 4 to 5 mm. in
thickness are sufficiently rigid for the purpose. Each disc is provided with a
handle on one surface, by which it can be manipulated with ease.

The appreciation of size is most conveniently tested on the palms, as there
the difference threshold is small.

The abiUty to distinguish the head from the point of a pin, when the latter
is applied so gently that it does not prick, depends on the power of recognising
relative size.

13. Appreciation of Shape in Tivo Dimensions.

By shape we mean the two-dimensional contom' of an object that can be
recognised on contact with the sm-face of the body. To test this faculty we
have employed simple shapes, generally a circle, a square, a triangle and an
oblong, cut out of stiff leather. In the set we have found most convenient,
each side of the square, the diameter of the circle, and the height of the triangle,
were all 3-5 cm., while the oblong was also of this length and 1-75 cm. in breadth.

The shajje of these objects can be easily distinguished on the normal palm
when they are applied firmly and evenly, but unhappily they can rarely be
recognised on most other parts of the body, including the soles of the feet.

14. Appreciation of Form in Three Dimensions.

We employ the word " form " to mean the three-dimensional shape of an
object ; we test the abiUty to appreciate it by placing objects in the patient's
hand, asldng him to determine their form by feeling them and by moving them

VOL. I. D

34 STUDIES IN NEUROLOGY

about between his fingers. Any common objects, such as a x^encil, coin,
knife, etc., may be employed for this test, but we have found it advisable to
use, in addition, standard tests of geometrical form, such as a cube, a cylinder,
an ovoid (called by the patients " an egg "), a cone and a pyramid, made in
approximately the same bulk from wood. The patient is first asked to select
his own names for them, or if description offers any difficulty he is allowed to
point to the object he identifies in duplicates placed before liim.

When there is serious paralysis of the fingers, the test-object must be
moved about by the observer in the patient's hand; we have found this
sufficient for appreciating the objects we use, when the abiHty to recognise
form is not affected.

In addition to the power of appreciating these geometrical forms, we always
test the patient's abiHty to recognise famihar objects, such as a knife, pencil
or coin placed in his hand with the eyes closed.

15. Appreciation of Differences in Texture.

Interesting facts may be obtained by testing the patient's abiHty to recog-
nise the texture of ordinary stuffs by touch. For this purpose we employ a
set of common materials, caHco, flannel, silk, cloth and ribbed velvet, wliich
the patient is allowed to feel and move about between his fingers. Those
we use can usually be identified with ease by the jDatient's normal hand.

With lesions of the cerebral cortex this test yields striking results, if
carried out in the following manner. The patient is allowed to finger the
various stuffs, first with the affected and then with the normal hand. After
his answers have been recorded, an identical piece of the same texture, e. g.
ribbed velvet, is placed in both hands at the same moment. He not infre-
quently says "they are quite different"; asked to explain this difference,
an inteUigent patient may give an interesting account of the diverse sensations
evoked by stuffs of similar texture in the two hands.

CHAPTER III

CLINICAL APPLICATION OF THESE METHODS

Such were the methods we have employed to test sensation throughout
our various researches ; some were found useful in one piece of work, some
in another, but in the preceding chapter I have grouped them together
according to the sensory categories to which they belong.

I have attempted to follow the impulses produced by an external stimulus
from their origin on the periphery to their reception in the sensory centres,
and it is obvious that some of these tests, which are of value with lesions of
one part of the nervous system, are not api)Ucable when the disturbance hes
in some other portion. I shall therefore attempt shortly to indicate the
methods which have been found most useful, when the sensory paths have
been interrupted in various anatomical situations. At the same time I have
appended a short general scheme of examination suitable to each of the main
divisions of the nervous system.

(1) With Lesions of the Peripheral Nervous System.
Name —
Address —
Age — OccuiMtion —

Injury —
Date —
Cause —
Nature —

Nerve or Nerves affected —
(Radic graphic examination if necessary.)

Motor Power —

Defects of movement-
Muscles which are paralysed or show some loss of power —
Normal muscles in the affected limb —
Wasting-
Electrical Reacticns. (These tests should be deferred until the end of

the examination.)

36 STUDIES IN NEUROLOGY

Trophic changes (nails, hair, sldn, etc.) —

Vasomotor changes and Sweating —

Sensation —

Pain or other Sj)ontaneous Sensations —

" Tenderness," " Over-reaction," " Hyperalgesia " —

Form of stimulation by Avhich it can be evoked —

Is it reheved by heat or cold ?

Character of the jDain or discomfort ; does it radiate -sAddely ?

Distribution —
Loss of sensation —

To Cotton Wool (or to tactile hairs if necessary) —

To Prick-
To Pressm-e (observe if the sensation of pressure is accm^ateh^ locaUsed
or not) —

To Painful Pressure^

To Heat and Cold—

(Recognition of Passive Movements if necessary as corroboration of
loss of deep sensibility.)

Surgical Record —

First the patient is asked to give an account of any spontaneous sensa-
tions wliich he experiences in his daily life as the result of nerve injmy. If
he suffers from pain, its distribution is recorded on a chart together with a
short account of its character. It is important to note how these abnoi-mal
sensations behave both to changes in atmospheric conditions and on warming
or cooUng the affected parts.

Then the affected limb is examined for " h\'peralgesia " and '" tender-
ness." These two conditions are not identical; for, as we have shown, a part
of the body may react excessively to painful stimuli and yet be in a condition
of lowered sensibility even to pain. No area can be called " hyperalgesic "
in the strict sense of the word unless the measm'able aspects of sensation have
at least a normal threshold. This condition is rare except as the result of
direct irritation of some nerve trunk.

On the other hand, over -reaction to potentially disagreeable stimuli is a
common sequel to lesions of the peripheral nervous system. For example,
after complete division of the median, the whole of the area assigned
anatomically to this nerve is rarely, if ever, insensitive to the prick of a pin.
Moreover, if a jiin is dragged gently across the palm from the ulnar side the
patient usually cries out as soon as it passes to the radial aspect of this
anatomical border. He complains that it is " more sensitive " ; asked to
explain his meaning he insists that " it hurts more " and that " the feehng
rvms into my fingers; it is Hke electricity." Otherwise he may say, "'it is
numb but it hurts." When a pin is dragged lightly in an opposite direction

CLINICAL APPLICATION OF THESE METHODS 37

from the radial towards the ulnar half of the hand, an intelhgent patient
recognises that sensation becomes " all right " as soon as it has passed the
anatomical boundary assigned to the median nerve. But this observation
requires more introspective abihty on the part of the patient than recognition
of a disagreeable change, when the pin travels in the opposite direction.

Many patients can mark out this border for themselves by passing the
index finger of tlie normal hand across the palm and noting the points at
which the sensation changes. This has nothing to do mth a change in the
textm'e of the skin, esj)ecially in the later stages of recovery of sensibility
after nerve injury.

The same boundaries to the abnormal area^ can be defined with the help
of hot and cold tubes, provided the temperature is above about 48° C. or
below about 15° C. Such stimuU cause discomfort, and the patient usually
withdraAvs his limb as soon as the over-reacting portions are reached.

This over-reaction to all forms of disagreeable stimulation gradually
merges into parts completely insensitive to pricldng ; tliis is the condition
so commonly found in the hand some ten days or more after division of a
peripheral nerve. But it is important to remember that in some parts of
the body the border separating normal from abnormal is a well-defined fine
with no such over -reaction. This is the case whenever the boundaries of the
loss to light touch and to prick are co-terminous, as, for example, with the
anterior and internal border of the external popliteal.

When testing mth cotton wool it is important to remember that contact
with the hairs may evoke a response although the skin itself is insensitive.
On the palm of the hand the boundaries of the loss to this form of tactile
stimulus correspond to the " fine of change," which can be worked out by
di-agging a pin hghtly across from normal to abnormal parts. But on the
back of the hand the presence of the hairs is a disturbing factor and the true
boundaries of the loss of sensibility to cotton wool can only be determined
after shaving. A similar rule appHes to the upper Hmits of the external
popliteal and to other branches supplying hair-clad areas of the body.
Shaving, however, produces a material diminution of sensibility, and testing
must not be carried out immediately after removing the hairs.

When cotton wool is employed with due precautions, the results are usually
sufficient for diagnostic purposes. But it is not a measurable stimulus and
the effects produced, even by the same wisp of cotton wool, differ according
to the characters of the part to which it is appHed and the idiosyncrasies of
the observer. Over hairless parts, however, such as the palm of the hand
and sole of the foot, the extent of the loss of sensibility usually corresponds
to that revealed by a hair of 21 grm./mm'^. (5 grm./mm.). But for all careful
testing, or whenever there is the sHghtest ambiguity about the results obtained
with cotton wool, they should be checked by means of von Frey's hairs.

Next we attempt to determine what parts are completely insensitive to
the prick of a pin. The boundaries of this area are not, as a rule, well defined.

38 STUDIES IN NEUROLOGY

but it merges gradual!}^ into portions where sensibility is present though
grossly defective; this adds to the difficulty of recording the results on a
chart. The limits of the analgesia differ from time to time and are pecuUarly
liable to vary with vascular changes or coldness of the limb.

Sometimes, when testing with a pin, the patient says that he appreciates
the stimulus, although in reaUty he has no sensation of pricking, but recognises
the pressm'e excited by the point. It is important to bear in mind this source
of error ; before recording the presence of sensibility to prick we must be
certain that the patient is responding to its painful or uncomfortable aspect.
Over areas of diminished sensation painful sensation is frequently spoken of
as a " stinging or burning feehng."

With lesions of the peripheral nerves or posterior roots, an area sensitive
to the tactile aspect of pressure also responds to the pain produced bj' raising
it to an excessive amount. For example, after complete division of the median
nerve at the ^\Tist the terminal phalanges of the middle and index fingers may
remain sensitive to fii'm contacts ; if so, discomfort can be evoked by in-
creasing the pressure. The fibres of the median nerve on which this deep
sensibility depends are given off in the forearm and pass to the fingers by
way of the long tendons. Presence or absence of sensations of pi-essure may
be, therefore, of considerable diagnostic importance, especially if the wound
is situated at the ■WTist ; for, if the tips of the index and middle fingers remain
sensitive to pressure, these fibres have escaped and the tendons are probably
intact, whilst if deep sensibihty is absent they are likely to have been divided.

With peripheral nerve lesions it is usually unnecessary to measure the
amount of pressure required to cause pain ; for if deep contacts can be appre-
ciated, increasing the stimulus evokes discomfort, and considerable areas
insensitive to prick may respond to the painful aspect of pressure. This is
not the case when the lesion is situated in the spinal cord, and such dissocia-
tion of deep and superficial sensibility to pain may sometimes help to decide
whether the injury is mainly in the posterior roots or cord.

Another function wliich depends on the presence of deep sensibility is
the power of recognising posture and passive movements at the various joints.
It is always well, especially with lesions aiiecting the upper extremity, to
carry out these tests ; but they are usually of corroborative rather than of
primary diagnostic importance. Thus, with a complete lesion of the median
nerve, the patient loses the power of appreciating movements at the terminal
joints of the index and middle fingers ; but at the same time these phalanges
become insensitive to the tactile or painful aspects of pressure.

The tuning fork is of httle value as a test with lesions of the peripheral
nerves, for the vibration spreads so widely across and along the limb that
it is certain to reach some more or less normal portion unless many nerves or
roots have been destroyed. This makes it all the more valuable as a means
of discovering those changes in sensibility of hysterical origin which so
frequently compHcate the nerve injuries of war. Suppose a man has received

CLINICAL APPLICATION OF THESE METHODS 39

a gun-shot injury of the post-axial half of the forearm, he may present a
complete loss of sensation over the post-axial portion of the palm and back
of the hand together with total anaesthesia of the little finger and either the
whole or a portion of the ring finger. When the tuning fork is placed over
the ulnar part of the hand, he does not appreciate its vibration until it has
passed to the radial side of the anaesthetic border on the palm ; and yet
the vibration can be easily recognised by the observer if he places his fingers
over the thenar eminence of the affected hand. Had the patient sufl;ered
from a complete ulnar paralysis of organic origin, he would have himself
appreciated the tuning fork everywhere except when it was placed over the
distal phalanges of the httle finger. The original defects of sensibiUty, aided
by the suggestive testing methods of the sm'geon, have evoked an hysterical
anaesthesia, and the mind refuses to receive any impressions from a stimulus
originating within this area, although it may produce widespread ph3^sical
radiation.

Many difficulties surround the testing Avith heat and cold. We usually
begin with two tubes filled with broken ice and with water at about 48° to
50° C, and with them we mark out the areas completely insensitive to thermal
stimuH. But it is most important to remember that any temperature above
about 45° C. may evoke jjain and the " stinging " it causes is frequently called
" hot " by the patient, although he may be unable to appreciate either heat
or cold.

The limits of this complete insensibihty to temperature stimuli rarely
correspond to the full extent of the thermal loss, and it is usually necessary
to carry out further observations with less extreme degrees. But tempera-
tures round about 25° C. are frequently not appreciated in the Avinter, or
the hand is cold and blue ; it is better, therefore, for diagnostic purposes to
employ tubes containing water at 40° C. or below which can be recognised
at once over the equivalent normal parts as producing a sensation of warmth.
During recovery of sensibility after injury to a peripheral nerve the whole of
the affected area may become sensitive to ice and water at 45° C, and yet
temperatures of from 35° to 40° C. may evoke no response.

(2) With Lesions of the Spinal Cord, Bulb and Mid-brain.

Name —

A ddress —

Age — Occuyatioyi —

Disease or Injury —
Date of onset —
Cause —
Nature —

Situation of Injury —
(Radiographic examination if necessary.)

40 STUDIES IN NEUROLOGY

Reflexes —

Wrist-jerks —

Triceps-jerks —

Superficial reflexes from palm —

Abdominal Reflexes —

Knee-jerks —

Anlde- jerks —

Ankle clonus —

Plantar reflexes (observe the action of the inner hamstrings) —

Cremaster reflex —

Bulbo-cavernosus reflex —

Perianal reflexes —

I nvoliintary Movements ("spontaneous" or evoked) —
Character of movement —
Flexor —

Up-going toe, flexion at ankle, knee, hip —
Contraction of abdomen —
Extensor —

Movements of the opposite Hmb (similar or opposed ; rhythmical)-
Field from Avhich the various involuntary movements can be evoked —
Natm-e of the stimulus necessary to evoke these movements —
FaciUtation of visceral activity —

Motor Power —

Defects of movement —

Movements Mhich can be carried out voluntarily —

Co-ordination (with eyes open and shut) —

Tone and Spasticity —

Wasting —

Power of standing (on one or both feet ; with eyes open and shut) —

Gait —

Trophic Changes —

Vaso-motor and Sweating —

Sensation —

Spontaneous (including Pains and Girdle sensations) —
Areas of over -reaction —
Loss to Touch —
Loss to Pain —

Superficial —

Pressure —
Loss to Heat and Cold —
Lo caHsation —

CLINICAL APPLICATION OF THESE METHODS 41

Compass test —

Postiu'e and Passive Movement—
(If the hand is affected — weight — -

size — -
form —
textm-e.)
Sphincters, etc.
Bladder—

Vohintary or automatic. Retention —
Measiu'ed physiological activity. FaciUtation —
Condition of sphincter-
Sensation and desire —

Rectum — ■

Voluntary or automatic. Retention —
Physiological activity. Facihtation —
Condition of sphincter-
Sensation and desire —

Genitalia —

Erection, emission, desire —

Sensory condition of penis, scrotum, testicles.

Surgical record —

Spontaneous root-pains are the most important sensations of which the
patient may complain. They usually correspond to the level of the lesion
and on the trunk extend more or less directly round the body from back to
front. If the patient is asked to point to the situation of his pain, he usually
places his hand on two spots, one behind and the other in front, which form
the " maxima " for that particular area ; sometimes in addition he selects
another point on the lateral aspect of the trunk or he may draw his hand
right round his body at a certain level.

Not uncommonly such zones can be marked out by tenderness of the
body wall. A pin is dragged gently from above downwards and then in the
opposite direction across the parts indicated by the patient as the situation
of his pain. The area which can be defined in this manner by " tenderness "
of the superficial structures is not necessarily " hyperalgesic '"' ; for sensi-
bihty to pricldng may be measurably less than normal although the reaction
evoked is greater.

The form assumed by these areas corresponds more or less closely to the
distribution of the fully developed eruption in herpes zoster ; and the level
of the affected roots can be determined by reference to the chart drawn up
by Head and Campbell (45) from a series of post-mortem examinations in
this disease. Diagrams based on analgesic borders are useless for this purpose.
The significance of these root zones can be determined solely by the study of

42 STUDIES IN NEUROLOGY

residual sensibility (Sherrington [lOS and 109]), or of some irritative condition
of radicular distribution such as the eruption of herpes zoster.

With serious injuries of the spinal cord, especially those associated with
gross loss of sensation, the patient should be asked if he recognises the existence
of the i3arts below the injury. Sometimes he " feels as if he had lost his
legs " ; "it seemed as if my legs had been blown away." Otherwise he may
recognise that his Umbs are present, but thinks they are in same particular
position, although he is entirely unable to appreciate their true posture at
any moment. One of the earUest indications that the stage of shock is passing
away is given by the appearance of " phantom " legs.

It is also important to inqune into the condition of visceral sensations.
Can the patient appreciate that his stomach is full after a meal? Does he
experience desire to micturate or to pass a motion ? Can he tell when these
acts occur ? Is he able to recognise the passage of a catheter and if so at
what point during the manipulations ? Does he suffer from pain in the bladder
and rectum ?

In the jDresence of gross loss of motion and sensation neglect of such inquiries
may lead us to conclude erroneously tliat conduction in the spinal cord is
completely destroyed. We must also bear in mind that with the severest
lesions at the level of the ninth and tenth thoracic segments the sensibihty
of the stomach remains unaffected, and even a distended bladder may be
recognised by the pressure it exerts on the abdominal viscera. Moreover,
injurj^ in the mid-lumbar region allows of pain from the trigone, although the
remainder of the bladder and ureter are entirely insensitive.

AVith lesions of the spinal cord and brain-stem it is well to begin by deter-
mining the loss of sensibility to prick. But it is important to be certain that
when the patient says he " feels the pin " he is really sensitive to the painful
aspect of pricking. The majority of the less complete lesions of the spinal
cord do not affect tactile sensibility and the power of distinguishing the head
from the point of a pin is retained ; thus the patient can recognise contact of
the head from that of the point of a pin although he is entirely insensitive
to pain on the surface of liis body. He must never be asked, " Is that the
point of a pin ? " " Am I pricking you ? " ; he should be told before the testing
begins to answer " touch," " point," or " pain," and no questions should be
put to him during the manipulations. If the observer stiU remains doubtful
whether the patient's answers are really based on the power to appreciate
pain, a test-tube containing water at 55° C, or an interrupted current just
strong enough to excite pain, can be used as controls.

The extent of the analgesia is first mapped out roughly and its borders
are then delimited with greater care. Sometimes a definite line separates
the sensitive from the insensitive parts of the body; but more often there
is no such absolute hard-and-fast boundary. If this is the case testing should
be carried out as follows : start below within the completely analgesic area
and work systematically upwards on the body until the patient appreciates

CLINICAL APPLICATION OF THESE METHODS 43

the painful aspect of the prick. Then carry out the test in the opposite
dii'ection, beginning over normal j^arts ; when passing downwards on the
body record the boundaries at which the sensation becomes abnormal and
those at which all sensibility to pain is lost. The parts which lie between
the line of change and the total analgesia form the intermediate zone where
sensation is disturbed but not abolished. The extent of this area is of great
importance both for diagnosis and prognosis. If the upper border of the
analgesia only is recorded on the chart it does not in any way indicate the
site of the lesion ; this is revealed more nearly by the line at which sensation
changes from normal to abnormal and vice versa.

On the other hand, the more complete the destruction of sensory conduc-
tion the smaller Avill be this intermediate zone ; total transverse division of
the spinal cord is frequently associated with an analgesic border so definite
that it does not vary by one centimetre in either direction.

The algometer for measuring sensibility to painful pressure should never
be applied until the close of the examination, and the greatest care should
be taken not to cause excessive discomfort. The patient should be told to
call out directly the pressure exerted becomes in the least uncomfortable ;
but the results obtained do not aid greatlj^ in clinical diagnosis, although they
are of profound scientific importance.

With lesions of the spinal cord, or brain-stem, sensibility to heat and cold
may be disturbed independently of one another. Under such circumstances
the principal aim of the thermal tests is to discover whether the patient can
recognise the two quaHties of sensation ; determination of a threshold is of
comparatively little importance. We are therefore accustomed to use the
large copper tubes containing respectively water at from 2° to 10° C. and
from 42° to 48° C. A thermometer thrust thi'ough the cork stopper tells the
temperature within, which changes comparatively slowly.

But these observations are open to several fallacies. If the temperature
of the hot tube is too high the patient is liable to call the " stinging " sensation
it evokes " heat," although he may be in reality entirely insensitive to any
thermal element in the stimulus. It is difficult to avoid knowledge on his
part that he is being tested with heat and cold, and the " sting " of water at
from 50° to 60° is so characteristic that, if he is sensitive to pain, he at once
recognises that the hot test is being applied. In the same way he may be
unable to respond to cold, but can appreciate the disagreeable aspect of low
temperatures; this may lead him to call an iced tube "cold" and to dis-
criminate it accurately from one containing hot water. In each case the
stimulus is named correctly with the help of accessory sensations that have
nothing to do with thermal sensibility.

Again, a neutral tube, which is recognised as such over normal parts,
may be persistently called either " hot " or " cold " over the affected areas
of the body. It is most important, therefore, to interpose frequent stimula-
tions with a test-tube which is neither hot nor cold to the normal sldn.

44 STUDIES IX NEUROLOGY

Another difficulty arises from the existence of " paradoxical " cold. When
a considerable area on the trunk or limbs is insensitive to heat, a temperature
of about 45° C. stimulates the cold-spots and evokes a sensation of cold ; but
all thermal sensibility disappears when the contents of the hot tube are allowed
to sink below about 40° C, although this temperature produces vivid " warmth "
over normal parts. This is the well-known phenomenon of " paradoxical
cold."

Xo analogous paradoxical sensation of heat can be demonstrated either
on the normal skin or during the course of injmies to the peripheral nervous
system. But, when all sensibility to cold is lost as the result of some struc-
tural disorder of the spinal cord, and yet heat can be appreciated, temperatures
below about 20° C. are not infrequently called " warm." This may be another
instance of the tendency to call neutral stimuli " warm," wliich is so frequently
a soiu"ce of confusion with thermal tests ; or it is possibly due to the existence
of paradoxical heat. If tliis is so the phenomenon is much less vivid and
definite than the analogous sensation of cold.

When the lesion of the spinal cord is situated in the cervical or upper
dorsal region, the sacral areas on the back of the thighs and calves not un-
commonly remain sensitive to pain, heat and cold, or to one or more of these
quahties dissociated from one another. Thus the superficial analgesia may
be complete on the abdomen and lower extremity, but the third and fourth
sacral segments remain sensitive to prick (see p. 386) ; a similar condition existed
for thermal stimuU except that the area over which sensation Avas preserved
was somewhat more extensive and included the sole of the foot. Such reten-
tion of sensibiUty over the lower segmental areas is of considerable diagnostic
importance and may be easily overlooked.

As a rule there is little difficulty in testing appreciation of the jiosture of
the limbs or the power of recognising passive movements ; for, when this
aspect of sensation is affected from some lesion of the spinal cord, the loss
is usually extremely gross. The patient may not only fail to appreciate that
the leg is being bent or straightened at the knee, but be unable to recognise
that it is resting in a flexed or extended position.

The crudest of all the tests for recognition of posture is to place one lower
extremity into a certain position and then to ask the patient to touch the
great toe with the heel of his other foot. First we make certain that tliis
movement can be carried out accm^ately, when the eyes are open and attention
is directed to the lower extremities. Then the eyes are closed or the lower
part of the body is effectively screened. If the power of recognising postm'e
is distm-bed the patient finds difficulty in approximating his sound foot to
the great toe of the affected limb, but may carry out the opposite movement
with comparative accuracy. This is, however, a coarse test and depends
greatly on the sensory condition of the joints of the hip and the knee.

"\^hen both lower extremities are affected we ask the patient to imitate
with his hand the position and movements of the foot we are testing. Thus

CLINICAL APPLICATION OF THESE METHODS 45

with extension or flexion of the great toe he raises or lowers his thumb and
indicates by movements at the ^\Tist the postm-e assumed by the foot. This
method is sometimes very successful for chagnostic purposes, but cannot be
recorded in measurable terms.

Frequently, Avhen in doubt, the patient guesses at an answer, and if this
happens to be correct it is difficult to be certain that there is no appreciation
of passive movement. We therefore continue to grasp the part firmly between
the fingers, holding it at rest for a time in the new posture. If recognition of
passive movement is gravely disturbed, the patient not infrequently describes
some fresh change of position, although the part has remained quiescent.
Such false answers may be almost as frequent on the records as his rephes to
actual changes in posture.

Occasionally after a series of observations the hmb is held in one position
and the patient is allowed to open his eyes ; his look and exclamation of
astonishment is strong corroborative evidence that his power of appreciating
movement and posture is gravely affected.

The tuning fork has long been known as one of the most valuable tests
with lesions of the spinal cord ; it is the most easily handled indicator of the
functional state of the posterior columns. So long as one lower extremity
gives normal answers to vibration, the procedure we adopt follows that laid
down in the general chapter on Methods ; but with lesions of the sj)inal cord
the sensation of both legs is frequently affected and we are forced to compare
the duration on the sole of the foot with that on the normal palm. This is
most unsatisfactory unless the difference is extreme. Fortunately, however,
if the loss of sensibihty is bilateral, it is usually so gross that the vibration is
not appreciated at all.

This test is frequently treated as if it depended on the sensibihty of bones
and other deep structures only ; but when the anaesthesia is bounded by a
1km line running from back to front across the abdomen, vibration not infre-
quently reveals a similar and definite border. This seems to be particularly
evident, when the upper limit of the loss of sensation is due to injm'y of posterior
roots. Under these conditions the tuning-fork may be of considerable use in
determining the level of the lesion.

The compass test, though of great scientific interest, is of httle diagnostic
importance in lesions of the spinal cord. Loss of abihty to discriminate two
points shows some functional distm'bance of the posterior columns, and
although this may not be exactly co-extensive with the want of recognition
of passive movement or vibration, the differences are of little practical
importance.

So long as the lesion is situated within the spinal cord locahsation of the
stimulated spot is closely associated with the condition of contact sensibihty.
We have employed as our test the modified Henri method, using a hving model
of the part under examination, as described on p. 25.

If one or both hands are affected the power of discriminating weight,

46 STUDIES IN NEUROLOGY

form and texture, can be employed as a guide to the finer functional aptitudes
depending on the condition of the posterior columns. But lesions of the
spinal cord commonly affect the trunk and lower extremities only. Here it
is not possible to apply these tests with any hope of obtaining results of any
definite value. Some jjeculiarly intelUgent patients can recognise correctly
with the soles of their feet the shape of the wooden figures we use for testing
forms in three dimensions. But the majority are unable to do so ; this renders
these tests of little practical value in most cases of disease or injury to the
spinal cord.

(3) With Cerebral Lesions.
Name —

Address —

Age — Occupation —

Disease or Injury —
Date of onset —
Cause —
Nature —
Situation of Injury —

(Exact measurements of situation of wound or opening in the skull.
Retraction, bulging and pulsation of trephine opening) —
(Radiographic examination if necessary.)

Mental State —

(Especially state of memory, attention and power of concentration,
affective condition and behaviour under examination.)

Sleep and Dreams —

Speech —

Convulsions or Seizures —

Headache —

Character, time of onset, dm-ation —

Effect of postm-e, movement and vibration (e. g. railway traveUing),

fatigue (mental and physical), concentration and intellectual effort —
Tenderness (superficial or deep) —
Consciousness of the opening or point of injmy.

Vomiting — •

Vision. (Acuity and Visual Fields.) Ophthalmoscopic examination.

Hearing —

Smell and Taste —

CLINICAL APPLICATION OF THESE METHODS 47

Affections within the territory of the Cranial Nerves —
Reaction of the Pupils —
Ptosis, or narrowing of palpebral fissure —
Ocular movements —
Nystagmus —
Sensation of the face —
Movements of the face —
Movements of the jaw —
Movements of the palate —
Movements of the tongue —

(Condition of Sterno-mastoid and Trapezius if affected) —
(Examination of Larynx if necessary.)

Motor Power —

(Recording first the condition of the upper and then of the lower
extremity) —
Loss of Voluntary Power —

(Especially individual movements.)
Movements which can be carried out voluntarily in the affected

hmbs —
Co-ordination with eyes open and shut —
Involuntary and Synergic movements —
Tremor —

Tone of the affected limbs —
Wasting —
Gait —

Power of standing (on one or both feet; with eyes open and
shut.)

Reflexes —

Wrist- jerks —

Triceps- jerks —

Abdominal reflexes —

Knee-jerks —

Ankle -jerks —

Ankle clonus —

Plantar reflexes (observe the action of the inner hamstrings) —

Sensation —

Spontaneous —

" Numbness," Pain, Tingling —

Knowledge of the existence of the affected parts, and conception of
their posture.

48 STUDIES IN NEUROLOGY

Loss of Sensation —

Touch-
Cotton wool or camel's-hair brush over hairless and hair-clad parts —
Tactile hairs —
Tickhng—

Pain-
Pricking. Threshold with Algesimeter —
Affective reaction to measured pricking and to painful pressure —

Heat and Cold —

Recognition of heat and of cold —

Discrimination of different degrees of heat or of cold —
Neutral zone comj)ared on the two sides —
Affective reaction —

To extreme degrees of heat and cold —
To pleasant warmth —

Appreciation of Posture —

Appreciation of Passive Movement —

Falhng away of the unsupported hmb, when the eyes are closed —
Measurement of the angle of the smallest movement that can be
apjjreciated and of the angle at which its direction is recognised
correctly —

(Vibration of the Tuning-Fork) —

Compass Test (points apphed strictly simultaneously) —

Localisation —

Discrimination of Weights —

With the hands fully supported. Addition and Subtraction —
" Weigliing " freely —

Discrimination of objects of various shapes —

(Nature of common objects placed in the hand) —

Recognition of Texture —

Sphincters —

]Mictmition —
Defalcation —

Surgical Record —

As a rule there is little difficulty in discovering the nature of the sensory
disorder caused by a lesion of the spinal cord or brain-stem. No elaborate
tests are requii-ed ; for the loss of sensation is usually severe and corresponds
in great part to the simple categories of touch, pain, heat and cold.

But whenever the lesion Hes above the thalamic junction, sensory testing
is Slurrounded by innum.erable difficulties. Many of the defects of sensibihty
appear to be due to a localised loss of attention ; the answers become irregular
and the patient appears to be untrustworthy. It is extremely important,

CLINICAL APPLICATION OF THESE METHODS 49

therefore, to exclude all sources of general discomfort, fatigue, or defective
concentration. On the other hand, the observer must be expert in adapting
his tests to the condition of the subject under examination ; a patient whose
general powers of attention are poor should not be exposed to an elaborate
series of observations, such as a linger to finger examination mth the tactile
bail's. The tests must be simplified and the area to be explored reduced to
the smallest measure compatible with diagnostic information. But if the
patient is intelligent, and if his psychical and physical state is favourable,
the examination can be extended with due precautions to a remarkable degree.

It is most important to adapt the methods employed to the immediate
circumstances ; such tests as the tactile hairs, vibration, and determination
of the neutral zone to thermal stimuU should not be deferred to the end of
a long sitting, even with the most apt and AvilUng |)atient. Should the time
be too limited for an elaborate series of sensory observations, it is better to
choose a few significant tests and to carry them out well rather than to attempt
a diffuse and incomplete examination. Hurried testing confuses the patient
and destroys that calm so necessary on the side of the observer. With a
lesion affecting the sensory cortex, the three tests which yield the most definite
results are passive movement, the tactile hairs, and the relative appreciation
of graduated Aveights, Should sensation be disturbed, one or more of these
methods of examination will reveal the nature of the defect and, for diagnostic
purposes, it is unnecessary to multiply sensory tests.

The condition of tactile sensibiUty can be roughly explored by a series of
contacts with cotton wool. Over the palm of the hand and sole of the foot
on the affected side some touches can be appreciated, but others may be
missed, although the patient gives a complete sequence of answers from the
normal parts. But over hair-clad areas this is not the case ; every contact
evokes a reply. If, however, the lesion is situated in the optic thalamus,
cotton wool moved over the hairs produces a remarkable sensation, usualW
spoken of as " tingling " or " itching." It radiates widely and is most char-
acteristic. But, apart from these indications of some abnormal sensory state
requiring fiu'ther investigation, cotton wool cannot be considered as a serious
method of examining the condition produced bj' cerebral lesions. This also
appUes to the use of the camel's-hair brush.

If a series of pricks with a sharp pin reveal gross loss of sensation, the
lesion cannot have affected the cortex only, provided all causes of shock are
ab.sent. Either the terminal receptive junction in the optic thalamus has
been injured or subcortical paths have been destroyed. But, although the
pin is of little value as a test for cortical affections, it is the key to the
so-called "thalamic syndrome." When the point is dragged across the trunk
from the normal half of the body, an intense over -reaction occurs as it passes
the middle Une. The patient complains that it " hurts him more," and this
is shown by the movements of withdrawal and by the expression on his face.
If the palm or the sole are pricked his suffering is obviously greater on the

VOL. I, E

50 STUDIES IX NEUROLOGY

affected side; provided the lesion is confined to the brain, tliis exaggerated
response is diagnostic of thalamic over -reaction.

When sensation is over -weighted ^\ith feehng-tone, a similar reaction
can be evoked by the large tubes containing broken ice and water at 50° C.
or above. Sometimes, by adjusting the temperature of the hot tube so that
it falls within the range of pleasant heat, it is possible to show that pleasure
is also exaggerated on the affected half of the body ; this is absolutely diagnostic
of excessive thalamic activity.

With lesions of the cerebral cortex the most significant thermal test is the
discrimination of two temperatures of the same quaht}^ but of different degrees,
such, for example, as 35° and 42° C. Both are said to be warm over the hand
and foot under normal conditions, but there is no doubt that one is hotter
than the other. On the opposite half of the body they may be confused or
thought to be identical. When the difference between the two sides is pro-
found, this abnormal response is one of the most characteristic signs of a
disturbance of thermal sensibihty. At the same time it is much more easily
and certainly determined than the threshold for heat and cold.

Roughness, tickUng and scraping are significant elements in the " thalamic
syndrome," but are not other\vise of importance A^ith lesions of the brain.

The power of recognising vibration is of great scientific importance, but
has no practical value mth cerebral disease or injm'y. This test is often
difficult to carry out successfully, and all the information it affords can be
obtained more easity by measuring the range of passive movement, which the
patient can appreciate correctly.

To test locahsation by our modification of the Henri method is easy to
carry out and often acts as a valuable confii-mation of the results obtained
by the other methods of exploring the spacial aspects of sensation.

The compass test may also furnish corroborative evidence that the sensory
disturbance is of the higher type ; but it labom's under the disadvantage that
it is profoundly affected by any disorder of tactile sensibihty and it is not,
therefore, a specific test from the cortical point of view.

One of the commonest defects produced by a cerebral lesion is want of
recognition of the posture of the affected parts. Not infrequently this can
be demonstrated in the foUo^^Ing manner. Place the arm in a resting position
on the bed and allow the patient to look at it and feel it \\ith his normal hand.
Then, having closed his eyes, remove the Hmb into some different position
and ask him to touch a definite digit Avith his normal index finger. If he has
lost the power of recognising posture to any considerable extent, he wdU grope
on the bed in the neighbourhood of the previous position of his hand.

Whenever the faculty of recognising postm-e is distm-bed fi'om a lesion of
the brain, the patient experiences gi-eater difSculty in finding the affected
Hmb -with the normal hand than vice versa; it is easier for him to indicate
some spot on the normal side with the affected Umb, provided it is not too
severely paralysed or gi-ossly inco -ordinate. For in the first case he is ignorant

CLINICAL APPLICATION OF THESE METHODS 51

of the site of the object at which he is aiming, whilst in the second he is aware
of its situation, although the instrument with which he points is faulty.

This is the exact opposite of the result not infrequently obtained in
hysterical conditions ; here it is the affected limb that fails to find the normal
one. For, since hysteria proper follows psycliical and not physiological Unes,
it is the affected parts wliich carry out their functions badly ; a " good " limb
executes all its movements normally, even when it is set to find a part of the
body whose position is presumably unknown to the patient with his eyes closed.

Of all the tests for loss of sensation, measurement of the range of passive
movement necessary to excite recognition is the most valuable from the point
of view of cerebral lesions. No sensory disturbance is so universal, and the
difference between the results, obtained from the normal and affected halves
of the body, differ so profoundly that measured movement becomes of
predominant importance both diagnostically and scientifically.

The direction of the movement carried out passively is frequently indicated
MTongly and the records may be disturbed by hallucinations. These confuse
the orderly presentation of the numerical defects, but are in themselves of
great importance diagnostically ; for they are particularly liable to occur
when the lesion affects the cortex, although they may appear with other cerebral
lesions.

AbiUty to recognise differences in the weight, size and shape of external
objects depends on one group of cortical activities. Not infrequently the
loss of sensation is so gross that the patient cannot recognise the nature of
common objects placed in his hand ; under such conditions measurements are
not necessary from a practical point of view.

But whenever the disturbance is less severe, an examination with graduated
weights is both the easiest and most satisfactory of all these tests. Fuvst the
hands must be fully supported Avith the palms upwards in an easy position;
two weights are placed successively, first on the normal hand and then on
that which is affected. The patient is asked to state which of the two weights
is the heavier. Normally there is no difficulty in recognising the difference
between 70 and 100 grms. and many persons can give a series of correct answers
with 80 and 100 grms. For cUnical purposes it is unnecessary that the weights
should differ from one another by less than 10 grms.

Then we estimate the power of recognising increase or decrease of a weight
resting on the hand according to the method described on p. 32. This is an
easy and significant test, provided care is taken to avoid excessive contact
stimuli, which are liable to arise from clumsy addition and removal of the
weights.

Finally the patient is asked to compare two weights balanced freely one
in each hand. So long as the lesion is subcortical, this faculty depends on his
capacity to estimate movement, whilst with affections of the cortex the power
of " weighing " may be preserved or lost independently of the spacial aspects
of sensation.

PART II

THE PERIPHERAL NERVOUS SYSTEM

THE AFFERENT NERVOUS SYSTEM FROM

A NEW ASPECT 1

By henry head, M.D., F.R.S.,

The conclusions expressed are drawn from investigations carried

out in conjunction ivith

W. H. R. RIVERS, M.D., F.R.S.,

Fellow of St. Johns College, Cambridge,

AND

JAMES SHERREN, F.R.C.S.,

Surgeon to the London Hospital.

It has long been recognised, by all who have interested themselves in the
problems of sensation, that no view yet advanced of the structure and functions
of the afferent nervous system is sufficient to explain obvious facts. The
teaching of the anatomist throws little hght on the difficulties with which the
surgeon is confronted. On the other hand, it is difficult to reconcile the various
views concerning the nature of common sensibility with the facts of clinical
experience.

Such want of correspondence between observed facts and the prevailing
general ideas showed that the distribution and function of the peripheral nerves
required reconsideration. In the present paper we shall put forward a new view
of the mechanism of sensation, based upon several different hnes of research.
If we may seem unduly to neglect the work of others, let it be remembered that
this paper is introductory to a series of communications, each of which will
deal with one aspect of the subject more exhaustively than is possible in a
preliminary statement of a new hypothesis.

When the median nerve is divided, sensation is entirely lost over a consider-
able part of both the index and middle fingers. Over the palm, within the area
said by the anatomists to be supplied by this nerve, sensation is usually dimin-
ished and not completely abolished. In a similar manner, cUvision of the
ulnar nerve produces complete insensibility of the httle finger, and of a variable
portion of the ulnar aspect of the palm ; but partial loss of sensation is found
over a larger area of the palm and the ulnar half of the ring finger. Such is

^ The substance of this paper was delivered on May 23, 1905, before the Royal Medical and
Chirurgical Society as the Marshall Hall address.

56 STUDIES IN NEUROLOGY

the usual statement of surgeons and anatomists. When they are asked, why
sensation is only partially lost over the palm, the usual answer is, " Because
there the nerves overlap." But if each nerve occupies the territory of the other
to an extent sufficient to prevent absolute loss of sensation over so large a
portion of the palm, it is obvious that destruction of the ulnar nerve must
cause some diminution of sensibiHty over the median half. This loss should
vary exactly in proportion to the amount of sensation that remains, after the
median has been destroyed. But the most careful examination of the hand
fails to show the slightest diminution in sensation over the median half of the
palm in consequence of division of the ulnar nerve. What has always been
called the diminished sensibility produced by the division of a nerve is really
a condition in which some kinds of sensibihty are lost and others retained.
Within such a region of altered sensibility all sensation to light touch is
abolished. If, in a patient who has divided his uhiar nerve, the ulnar half of
the palm of the hand is stimulated with cotton wool, no sensation will be
produced, while the lightest touch can be appreciated directly the line corre-
sponding to the axis of the index finger is transgressed. If the area is large
enough to apply a pair of compasses, it will be found that the patient is totally
unable to appreciate two points two centimetres apart. Not only is sensation
abolished to these tests, but careful examination shows that temperatures
between 22° C. and 40° C. are not appreciated over this area. Thus, parts
which have universally been considered to be areas of diminished sensibihty
turn out to be totally insensitive to certain higher forms of stimulation.

When the hand has settled down after the shock of the injury that has
divided one or more of the nerves to the palm, it will be formd that, although
the area we have spoken of is totally insensitive to certain higher forms of
stimulation, a stimulus producing pain, e. g. a prick of a pin, causes a more
unpleasant effect than over normal parts.

If the nerve has been imited, sensation begins to return after a variable
interval. The first sign of recovery is a gradual diminution in the extent of
the area insensitive to pain and to all forms of heat and cold.

Finally, no part of the affected hand remains completely insensitive to all
cutaneous stimuli. It is to the condition of a hand at this stage of recovery
that we wish to draw particular attention. It might be supposed that, with
the gradual disappearance of analgesia, an improvement would follow in the
higher forms of sensibiHty. This is not so. The boundary at which light
touch is lost is as definite as in the days following the injury, although sensi-
bihty to pain, to heat and to cold, has vastly improved. In this condition the
hand may remain for many months, before hght touch begins to be appreciated
over parts that Ue within the borders of altered sensibihty.

Closer examination of parts in this condition shows that, although the hand
has become sensitive to pain and to temperature, this sensibihty is strangely
altered. A prick is appreciated, but produces a sensation that radiates widely
over the affected area. It causes unnatural discomfort, and the patient has

THE AFFERENT NERVOUS SYSTEM 57

an uncontrollable desire to withdraw his hand. Moreover, although ice and
water at a temperature of 50° C. are appreciated as cold and hot, intermediate
degrees produce no sensation of temperature, and water at 25° C. or 26° C. may-
be indistinguishable from water at 40° C.

We assured ourselves of the truth of these conclusions during more than
two years spent in watching patients who had come to the London Hospital
on account of injuries to one or more peripheral nerves. But it became obvious,
that in order that we might examine more exhaustively the sensory condition
of parts that had been robbed of their nerve supply, it was necessary that the
patient should be a trained observer, and the injury determined beforehand.

On April 25, 1903, the radial (ramus cutaneous n. radiaUs) and external
cutaneous nerves were divided in the neighbourhood of my elbow, and after
small portions had been excised, the ends were united with silk sutures. Before
this operation, the sensory condition of the arm and back of the hand had been
minutely examined, and the distance at which two points of the compass could
be discriminated had been everywhere measured.

This operation produced loss of all forms of cutaneous sensibility over an
extensive area on the radial half of the forearm and back of the hand. Stimula-
tion with cotton wool, the prick of a pin, the apphcation of all forms of heat
and cold, were unappreciated, and the two points of the compasses could not
be discriminated, even when separated to the furthest extent possible. But if
this part was touched with the point of a pencil, the head of a pin or even with
the ball of the finger, the stimulus was at once appreciated, and the point of
application localised with remarkable accuracy.

We are thus face to face with the conclusion, that complete destruction of
all the sensory nerves to the sldn leaves the part sensitive to most of those
stimuU commonly used by the physician and surgeon as a test of sensibiHty
to touch. With the Graham-Brown aesthesiometer, an instrument which
measures the appreciation of irregularities in an otherwise smooth surface, the
hand that had been robbed of all its cutaneous sensibility was found to be
actually more sensitive than a similar part on the normal side.

Since all the nerves had been divided which supplied the skin, the main-
tenance of this sensibility must have been due to afferent fibres running with
motor nerves. Sherrington (111) has demonstrated the existence of such sensory
fibres and traced them to the muscles, tendons and joints. By the operation
on my arm, we had gained the unique opportunity of exposing a part, endowed
with deep sensibility only, to a series of careful tests.

The pecuhar aptitude, possessed by a part innervated solely by the afferent
fibres of a muscular nerve, is the appreciation of all stimuli which produce
deformation of structure. Pressure or any jarring of the sldn was quickly
appreciated in my case, and, on the whole, was locaHsed with remarkable
accuracy. But, when the hairs were pulled, the elevation of the skin produced
no effect upon consciousness. Pressure, which had previously caused a sensa-
tion, was no longer appreciated when applied to the skin lifted from the subcu-

58 STUDIES IN NEUROLOGY

taneous structures to form a ridge. This showed that the sensibihty to pressure
was not due to nerves still remaining in the skin after the operation. Although
pressure was locahsed with considerable accuracy, all sense of form and size
was lost over the parts affected. The prick of a pin and the interrupted current
were entirely unappreciated; but excess of pressure produced aching pain.
When the pressure was produced by means of Cattell's algometer, it was found
that pain was ehcited with a smaller pressure of the instrument than on the
sound side. The affected parts could be burnt without producing pain, and
no sensation of cold was produced, even when the hand was frozen firmly by
means of ethyl chloride.

This condition remained unaltered imtil seven weeks after the operation,
when sensation of prick began to return on the arm. Six weeks later, there was
no part of the forearm where prick could not be appreciated, and within 200
days from the time when the nerves were divided, even the back of the hand
had become sensitive to this form of stimulation. Yet, for more than a year,
both forearm and hand remained completely insensitive to light touch, and
more than two years after the operation, the hand had not completely
regained its sensibility, when tested \vith cotton wool and with the compasses.
Thus, we had ample opportunity of examining mth care the sensory con-
dition of a part sensitive to prick, but insensitive to light touch. We found that,
when the forearm or hand was pricked, the pain produced was not localised,
but radiated %videly, and was not infrequently referred to some part at a distance
from the point stimulated. Ice and water at 50° C. were appreciated, but minor
degrees of temperature produced no effect upon consciousness. This peculiarity
in the behaviom* of the hand and forearm we found to be due to what are known
as " cold- " and " heat-spots."

Blix (7 and 8) first described the presence of " cold -spots " in the skin, and
his work was ampUfied by Goldscheider (40). To some observers, such as von
Frey (32 to 36), all forms of sensation possessed by the skin are due to the existence
of small areas of specific sensibility. So extreme a view has been accepted by
few ; some even doubt the very existence of temperature spots. By suitable
methods spots can be demonstrated in the normal skin where cold alone can
be appreciated ; analogous spots, more sparsely scattered, can also be shown
to be devoted entirely to sensations of heat. In the same way it would seem
that there are spots peculiarly sensitive to the prick of a sharp needle ; but the
disturbance produced by their stimulation is so great, that they cannot be
demonstrated with the same certainty as the spots devoted to sensations of
temperature. Now fari "passu with the return of sensibility to prick and to
the extremes of heat and cold, these spots reappeared upon my arm and hand.
But whereas, in the normal skin, the heat- and cold-spots are nothing more than
minute areas peculiarly sensitive either to heat or to cold, set in a territory
over which temperature stimuli can also be appreciated, the spots which made
their reappearance on my arm during the first stage of recovery were set in an
area insensitive to temperature stimulation. Thus, they were not only clis-

THE AFFERENT NERVOUS SYSTEM 59

coverable with unusual ease, but, since the only form of temperature sensation
possessed by the recovering part was due to their presence, it was particularly
easy to investigate their sensory peculiarities. The cold-spots could be stimu-
lated by any temperature below about 24° C. ; but, whenever a spot reacted,
what might be called an explosion of cold was produced, not locahsed at the
point touched, but radiating widely, sometimes even to a very considerable
distance. A small group of spots on the wrist always produced a sensation of
cold in the forearm just below the fold of the elbow, and two spots in the forearm,
when stimulated, evoked a sensation of cold in the thumb. The heat-spots,
more sparsely scattered, behaved in a similar manner. The lower Umit of
temperature to which they reacted varied from 38° C. to 45° C. One extremely
sensitive spot even reacted to 37° C. But, whether these spots reacted slowly
or briskly, the sensation was always one of widespread heat, and, until the
painful hmit of heat was reached, it mattered little at what temperature the
stimulus was appHed, provided it lay within the Umits capable of stimulating
these spots. The following experiment, which demonstrates this pecuUarity,
was many times repeated with the same results. A cold -spot of unusual activity
was stimulated by means of a copper cyUnder of one millimetre diameter, cooled
to the temperature of melting ice. This produced a sensation of cold. Water
at 20° C. was placed in a test tube with a fiat bottom of one centimetre diameter,
and this was applied to the skin in such a way that it stimulated a constellation
of spots, among which lay the spot originally stimulated. The sensation of
cold produced by this stimulus was more intense than that produced by stimu-
lating a single spot with a temperature considerably lower. Thus we come to
the remarkable conclusion that the heat- and cold-spots are incapable of produc-
ing, in consciousness, graduated sensations of heat or of cold. Water at 20° C.
can be made to appear colder than ice, provided the stimulus is so arranged
that the former is applied over a considerably larger area than the latter. Such
spots resemble in their action the cold alarms of our greenhouses. When the
temperature falls below a certain amount, a bell is rung, but no indication is
given of the extent to which the temperature has fallen.

Although we had peculiar difficulty in demonstrating the presence of
similar spots for pain, the general behaviour of a part in this stage of recovering
sensibihty, closely resembles that of the heat- and cold-spots. Radiation takes
place Avidely ; a more intense stimulus is necessary to evoke pain, but when
evoked, the pain is greater than over the normal skin. We also found that in
this stage of recovery many of the hairs had gained a pecuhar sensibihty. When
a hair on the normal skin is gently Ufted, a sensation of touch is caused which
is extremely well locahsed. But in the stage of recovery we are now dis-
cussing, the movement of the hairs produced a curious widespread formication,
with the same reference to distant parts as in the case of temperature
and pain.

However widespread the radiation may be to prick, to heat, to cold, or on
touching the hairs, it is not fortuitous in its distribution. We found, by

60 STUDIES IN NEUROLOGY

repeated experiment, that certain areas on the hand always caused radiation
into some other part irrespective of the form of stimulation.

All these facts would seem to show that we are here face to face with an
undiscovered form of sensibility, capable of producing qualitative changes in
consciousness, but incapable of causing a quantitative change apart from the
extent of area stimulated. The position of the point stimulated cannot be
recognised and each stimulus causes a widespread, radiating sensation, not
infrequently referred to parts at a distance. To this form of sensibility we
propose to give the name " jwotopatliic.''

The return of protopathic sensibility brings a cessation of all those destruc-
tive changes in nutrition that occur in parts where the skin is insensitive.
Ulcers form, as the consequence of burns or cuts, and do not heal so readily as
on the normal sldn. But such trophic changes are confined to parts insensitive
to protopathic stimuli. With the return of protopathic sensibility, ulcers
cease to form, and sores heal as readily as ori the normal sldn, although the
parts remain insensitive to all the higher forms of stimulation, such as light
touch. Thus a part supplied by protopathic sensibility alone, grows and is
repaired, as easily as the normal skin.

After the affected part has remained for a variable period in this condition,
it begins to become sensitive to light touch, and degrees of temperature, which
produce the sensations called " warm " and " cool " on the normal skin, are
again distinguished correctly from one another. With the gradual return of
sensation, it again becomes possible to discriminate two points touching the
skin at distances more nearly normal, and the widespread radiation, so charac-
teristic of the first stage of recovery, ceases, and is replaced by an increasing
accuracy of localisation. To this form of sensibility we propose to give the
name " epicritic," since it is peculiarly associated M'ith the localisation and
discrimination of cutaneous stimuH.

So far we have demonstrated the existence in the skin of two forms of
sensibility, but have brought forward no evidence to show that they depend
upon anything more than modifications of the same system of nerve fibres and
end-organs.

I can now deal with a curious phenomenon that occurred in the case of my
arm. Over the radial half of the dorsum of the wrist, a triangular area of skin
became entirely insensitive to prick in consequence of the operation. But
this same area remained sensitive to touches with cotton wool, and also, in a
limited degree, to warmth. The area was small, and its epicritic sensibility
was of a low order ; but in spite of these disadvantages, repeated testing
seemed to show that the area was capable of responding to temperatures
between 42° and 48° C.^ It was, however, entirely insensitive to temj)eratures
of 50° C. and above. To ice and to all forms of cold, this part was equally
insensitive. It would therefore seem that, by a fortunate chance in nerve
distribution, we had divided those fibres which subserved protopathic sensi-
^ See p. 285 for a fuller account of the condition of the triangle.

THE AFFERENT NERVOUS SYSTEM 61

bility, leaving untouched, at any rate, some of those which conducted the
impulses of epicritic sensibility. Such an observation can only be explained
by assuming that the two forms of sensibihty depend upon two separate systems
in the peripheral nerves. Experiments with so delicate a sensory change can
only be carried ou^t satisfactorily by frequent repetition, by selection of occasions
when the subject is, fro mi the sensory point of view, in excellent condition, and
under the rigid check of a large number of controls. These conditions are
rarely, if ever, satisfied during the examination of patients in whom the loss of
sensation has been produced by accident.

The mode of recovery of sensation after injury to a peripheral nerve also
supports the view, that these two forms of sensibility depend upon separate
structm-es. If the nerve has been completely divided, protopathic sensibility
returns first, followed at a considerably later period by return of epicritic
sensation. Provided the nerve has been completely divided, we have never
seen the faintest sign of returning epicritic sensibility, unless sensation to prick
had akeady shown material improvement. But, if the nerve is only bruised
or injured, so that its continuity is functionally, but not structurally, destroyed,
the two forms of sensibility may return ^ari passu.

Evidently, the two systems regenerate with unequal faciUty. The proto-
pathic system regenerates more rapidly and with greater ease. It can triumph
over want of apposition and the many disadvantages that are Uable to follow
traumatic division of a nerve.

Moreover, the length of the nerve to be regenerated makes relatively little
difference to the time at which protopathic sensibility retui'ns. Although the
nerves in my arm were divided at a point at least 20 cm. above the wrist,
recovery began in seven weeks and was completed, even over the hand, in
twenty-nine weeks. This compares favourably with most of our instances of
primary suture, in which the nerve was divided at the wrist. But this is in
no way true of the epicritic system. Provided the wound is healthy, and the
operation of the primary suture has been successfully performed, the length of
time required for epicritic regeneration depends upon the distance of the
wound from the periphery. And this is why, in my case, the period between
the close of the first stage and the beginning of the second stage of recovery
was unusually prolonged.

Every peripheral nerve contains in varying proportion the fibres subserving
these two forms of sensibility. Let us consider for a moment their distri'bution
in the nerves, the trunks and the roots which supply the upper Hmb.

To simplify what must of necessity be a somewhat complex statement, I
will deal first with the supply of epicritic sensibihty only. On the palm of the
hand, the area supplied by the ulnar and median nerves overlaps to an extent
less than one-half the breadth of the finger. Consequently, the borders of
the insensitive area produced by division of one or other of these nerves is well
defined. The back of the hand can be roughly divided into two halves, by a
line running from the knuckle of the middle finger to the middle of the back

62 STUDIES IN NEUROLOGY

of the wrist. On the ulnar side of this Hne, the hand is suppUed by the uhiar
and internal cutaneous, on the radial side by a combination of external cutane-
ous, the radial and the long cutaneous branch of the musculo -spiral. If we now
include the forearm, it will be found that a line drawn up the flexor surface
continuous with the axis of the ring finger, and up the extensor surface, continu-
ous with the line just mentioned on the back of the hand, divides the whole of
the forearm and hand into a pre-axial and a post-axial portion. Of these the
post-axial portion is supphed by the uhiar and internal cutaneous, the pre-axial
portion by the median, the radial, the external cutaneous, and the long branch
of the musculo -spiral.

Another border, which has the same character as these two axial lines, is
the boundary separating the distribution of the median from that of the group
of nerves supplying the radial half of the dorsal surface of the hand.

Whenever division of any nerve branch causes loss of sensation to hght
touch along one of these lines, that border will be well defined. Division of
one branch only will produce no definite area of anaesthesia, unless that area is
bounded by one or more of these lines.

Thus, provided the peripheral nerves are gathered into certain groups, it
may be said that from the point of view of light touch, and other forms of epi-
critic sensation, very Httle overlapping occiu-s. These groups are as follows :
(1) The ulnar and internal cutaneous; (2) the median; (3) the remainder of
the pre-axial group.

From this arrangement, the distribution of protopathic sensibility differs
fundamentally. Enormous overlapping occurs, as we have already seen from
a consideration of the analgesia caused by division of the median or of the ulnar
nerves. Evidently, the peripheral nerves, looked at broadly, form the units
of epicritic supply. On the contrary, from the protopathic point of view, no
one nerve forms anything more than a tributary supply of an area innervated
by a plexus of nerves, and, whenever a single peripheral nerve is destroyed in
the upper limb, the loss of light touch always exceeds considerably the extent
of the loss to prick. But, as soon as we have to deal with destruction of the
cords of the brachial plexus, the extent of the analgesia almost equals that of
the loss to hght touch ; and, when several posterior roots have been divided,
the extent of the area insensitive to prick may actually exceed that insensitive
to light touch. Thus it is evident that, whilst the unit of supplyfor_epicritic
sensibihty, Rooked at bxoa.dly^ Jies in tke peripheral nerv-es, the unit of proto-
pathic supply lies in the po^teriar-^oots^r The more nearly a peripheral nerve
represents the supply of one or more posterior roots, the more definite mil be
the borders of the analgesia produced by dividing that nerve. The median
nerve probably contains sensorj^ fibres from the seventh and eighth cervical,
and possibly even from the sixth cervical and first dorsal. Destruction of
this nerve will therefore only cut off protopathic sensibihty from the compara-
tively insignificant area to which all the fibres from these roots run in the one
nerve. On the contrary, the distribution of the external pophteal, including

THE AFFERENT NERVOUS SYSTEM 63

its lateral cutaneous branch, corresponds closely to that of the fifth lumbar root.
Consequently, destruction of this nerve produces a widespread loss of sensation
to prick, with an extremely well-defined border on the shin and dorsal surface
of the foot.

The sensory mechanism in the peripheral nerves is thus found to consist
of three svstems : —

(I.) Deep sensibiUty, capable of answering to pressure and to the movement
of parts, and even capable of producing pain under the influence of excessive
pressure, or when the joint is injured. The fibres, subserving this form of
sensation, run mainly with the motor nerves, and are not destroyed by division
of all the sensory nerves to the skin.

(II.) Protopathic sensibility, capable of responding to painful cutaneous
stimuli, and to the extremes of heat and cold. This is the great reflex system,
producing a rapid widely diffused response, unaccompanied by any definite
appreciation of the locaHty of the spot stimulated.

(III.) Epicritic sensibility, by which we gain the power of cutaneous localisa-
tion, of the discrimination of two points, and of the finer grades of temperature,
called cool and warm.

Let us now pass to the consideration of the arrangement of sensation in
the central nervous system. The view I shall put forward is based upon the
examination of a series of cases of haemorrhage into the spinal cord, and of
injuries affecting its substance, producing what is usually known as Brown-
Sequard paralysis. With these we have compared the sensory changes in
syringomyelia and tabes dorsahs. Now, all these conditions demonstrate that,
as soon as a sensory impulse reaches its first junction in the spinal cord, it
becomes shunted into tracts devoted to the conduction of impulses, grouped
in a way different from that found in the peripheral nerves. It is no longer a
question of protopathic, epicritic, or deep sensibility ; the tracts in the central
nervous system are devoted to the conduction of impulses concerned with pain,
heat, cold, and touch.

Thus, in Brown-Sequard paralysis, motion is lost in the one limb, and all
sense of pain, heat or cold, is abolished in the other. Careful examination of
this loss of sensation shows that sensibility is equally lost to all forms of tem-
perature stimulation, and that we have here to do with no such separation into
extreme and intermediate degrees as exists in the peripheral nerves.

In the central nervous system, the impulses are co-ordinated and distributed,
just as in the central office of a newspaper the various accounts of the same
event, arriving by telephone, by tape, or by telegraph, are co-ordinated and
distributed according to their subject-matter.

It has long been recognised, that the viscera are not endowed with the same
sensibihty as the skin, and some have even questioned whether they are sensi-
tive at all. It is certain, from the observations of Lennander (66) and his
school, that the patient shows no sign of pain when the gut is incised, or even
when it is burnt ; the liver is also apparently insensitive to similar injuries,

64 STUDIES IX NEUROLOGY

and vet everyone is agreed that the parietal peritoneum is highly sensitive.
We determined to attack the problem from a somewhat different point of view.
When a colotomy has been performed, the upper end of the gut opens freely
upon the surface, and no faeces pass into the lower portion. It is therefore
possible to wash out the lower gut, and by passing a tube into its upper end to
apply heat and cold to what is now an isolated loop of intestine. By choosing
patients who were inteUigent, and such as were not cachectic or wasted from
mahgnant disease, we obtained the follo^^'ing result. Water at 40° C. and at
20"^ C, wliich seemed warm and cold respectively to the skin of the abdomen,
were entirely unappreciated when apphed A^ithin the w^alls of the gut. But
ice water was at once called "' cold," water at 50° C. was said to be uncomfort-
able, and two patients of unusual inteUigence spoke of this stimulus as '' hot."
This sensation of heat and cold was never locahsed in the abdominal ca\'ity.
If the patient was asked to indicate the position of the stimulus, he either placed
his hand over the region of the navel or pointed into the aii*. Sometimes the
sensation was said to be hke cold drops on the skin in a part of the abdomen
where it would have been impossible for any water to have fallen. Moreover,
the strictest precautions were taken to insert the tube through a ring of mucous
membrane and to surround both the tube and funnel with absorbent cotton
wool, so that no moisture could possibly escape.

These experiments are not conclusive, but thej' seem to show that, in some
ways, the sensibihty of the viscera closely resembles that which we have called
protopathic. Only, the extremes of heat and cold are recognised, and locaUsa-
tion is so defective that the patient camiot even tell whether the cold is in or
outside his abdomen.

]\lany of the afferent impulses from the viscera produce a reflex action
without affecting consciousness. When we had passed a varying quantity
of warm water into the gut, the patient complained that he wished to defsecate ;
a reflex peristalsis had been set up of which he was conscious, although he failed
completely to recognise the stimulus by which it had been evoked. Most of
the afferent impulses from the stomach and intestines probably belong to
this order.

To a certain extent, we seem able to appreciate the muscular movements
of an internal organ, such as the stomach or intestme, even although \^e cannot
recognise the position in space of the part that is moved. This power is prob-
ably the equivalent of that deep sensibihty which remains to a part deprived
of all its cutaneous sensory nerves.

Structurally, we know that the viscera are innervated from the sympathetic
system, and from a set of large afferent fibres connected with the end-organs
of Pacini. The latter so closely resemble the mechanism found in muscles,
tendons and joints, subserving what we have called deep sensibihty, that we
can assume the end-organs of Pacini to be the means by which we gain a similar
power of appreciating intestmal movement.

But apart from such sensations of movement, the viscera certainly set up

THE AFFERENT NERVOUS SYSTEM 65

afferent impulses which may affect consciousness. We have attempted to
show that, however feeble these sensations may be in consequence of the defec-
tive innervation of the intestine, they produce upon consciousness an effect
resembhng that of a low form of protopathic sensibility. Now, one of the
pecuharities of protopathic sensibility is the rapid restoration of the mechanism
upon which it is based. This it shares with the sympathetic system. More-
over, when a peripheral nerve to the hand is divided, it is noticeable that the
palm begins again to sweat at a time after union which coincides approximately
with that of the return of protopathic sensibility. This sweating is due to the
motor fibres of the sympathetic (the " autonomic fibres " of Langley) that
supply the sldn.

It will therefore be no adventurous guess to suppose that the system we
have called protopathic in the skin is one with the afferent fibres of the sympa-
thetic as they supply the viscera. In both cases the sensation is badly locahsed,
radiates widely, and is frequently referred to parts other than those stimulated.
Both systems are incapable of appreciating light touch, and both are insensitive
to the minor degrees of heat and cold. Both regenerate with the same rapidity
and completeness.

We wish, therefore, to put forward a new conception of the nature of the
afferent fibres in peripheral nerves.

The whole body within and without is supplied by the protopathic system.
The fibres of this system in the skin may be spoken of as somatic, those to the
internal organs as visceral protopathic fibres. Thus we shall no longer speak
of the afferent sympathetic system, but of the protopathic supply of the internal
organs.

Another set of afferent fibres peculiarly associated with impulses of move-
ment and pressure exist in connection with the Pacinian organs. In the body
and limbs, an analogous system is found peculiarly susceptible to pressure, to
the localisation of movement, and to the appreciation of position. The fibres
of this system run in conjunction with the motor nerves.

In addition to these two systems, which are distributed to all parts of the
body within and without, the surface of the body only is supplied by a third
system, which we have called epicritic. This endows the skin with sensibility
to fight touch. To the impulses conducted by this system we owe the power
of localising the position of cutaneous stimuli, of discerning the doubleness of
two points, and of discriminating between minor degrees of heat and cold, and
other special attributes of sensation. The fibres of this system are more easily
injured, and regenerate more slowly, than those of the protopathic system.
They are evidently more highly developed, and approach more nearly to the
motor fibres that supply voluntary muscle, in the time required for their
regeneration.

VOL. I. r

THE CONSEQUENCES OF INJURY TO THE
PERIPHERAL NERVES OF MAN

HENRY HEAD, M.D., F.R.S.,

AND

JAMES SHERREN, F.R.C.S.,

Surgeon to the London Hospital.
PREFACE

Generations of anatomists have studied the course and distribution of
the peripheral nerves, until knowledge of their more obvious features has
apparently reached finality. It is recognised that more can be learnt of their
central connections and of the relation of the larger branches to the anterior
and posterior roots. But the peripheral distribution of the nerves of the hand
is regarded as one of the commonplaces of anatomy.

And yet, whenever an attempt is made to apply this knowledge to some
case where one of these nerves has been divided, obvious facts remain unex-
plained, or accessory hypotheses must be invented to account for the apparent
difficulties of each individual instance. The more carefully the condition of
the affected part is examined, the less does the state of its sensibility correspond
mth the surgeon's expectation. After he has successfully reunited the ends
of the nerve, a conscientious examination only adds to the bewilderment of the
observer.

If, for instance, the median nerve is divided, all cutaneous sensibility is
abohshed over a considerable part of both the index and middle fingers. But
over the palm, Avithin the area supphed b}^ the median nerve, sensation may be
diminished only. In a similar manner, division of the uhiar nerve produces
complete insensibihty of the little finger and of a variable portion of the ulnar
border of the palm. Cutaneous sensibility is only partially lost over the palm
and that part of the ring finger usually assigned to the ulnar nerve. When
the surgeon or anatomist is asked why sensation is only partially lost, the usual
answer is, " Because the nerves overlap." But, if each nerve occupies the
territory of the other to an extent sufficient to prevent absolute loss of sensation
over so large a part of the palm, it is obvious that destruction of the ulnar nerve
must cause some diminution of sensibihty within the median area. This loss

INJURY TO THE PERIPHERAL NERVES 67

should vary exactly in proportion to the amount of sensation that remains
over this part of the palm, after the median nerve has been destroyed. But
the most careful examination of the hand fails to reveal the slightest diminution
of sensation over the median half of the palm, in consequence of division of the
uhiar nerve. What has always been called diminished sensibiUty ends sharply
at a line in the axis of the ring finger.

Such want of agreement between anticipated effects and the actual results
of division of a peripheral nerve pointed to a gap in our knowledge of the distri-
bution and functions of this part of the nervous system, which we have
attempted to fill.

To those who have not worked in a town Uke London, it may seem an easy
matter to examine a patient with some nerve injury at regular intervals from
the date of the accident up to complete recovery. But any systematic attempt
to carry out such an investigation is hampered by innumerable difficulties, due
solely to the conditions of Hfe among the working population of this huge city.
Firstly, the original wound may have been treated at some other hospital, or
by a private joractitioner. Often the state of the wound and the extent of the
injury can then be inferred from the patient's description only. Again, after
the nerve has been successfully reunited, he may find it more convenient to
attend some other hospital ; or may leave his hand entirely untreated, and thus
render useless the careful investigation at the time of the injury, the exploration
of the wound at the time of suture, and the observations made during his stay
in hospital.

Lastly, the investigation may be brought to a sudden end by his change of
dwelling. For instance, within the space of twelve months, one of our patients,
a married man with a family, changed his address five times. Two or three
changes in a year are of frequent occurrence, and letters remain unforwarded.
In spite of the help of an assistant, sldlled in tracing the movements of hosj^ital
patients, and in spite of the fact that compensation on an ample scale was given
for travelling expenses and loss of time, many patients disappeared entirely,
often at the most interesting period of recovery. This is particularly liable to
occur when the median has been divided. For this injury interferes httle with
the grasp of the hand, and the patient is afraid to attend the hospital, lest
his employer should consider him unfit for work. To meet this difficulty, we
found it necessary to institute frequent Sunday sittings.

No instances are included in this paper that have not been examined by one
or both of us. As far as possible, one or other of us has been present during the
operation ; but occasionally w^e have been compelled to rely on the account
given by others of the condition then found. With this exception, no note
has been included that is not the direct outcome of our personal observation.

CHAPTER I

NERVE SUPPLY OF THE PALM OF THE HAND ^

§ 1. — DI^^:sION of the Ulnar Nerve

Complete division of the ulnar nerve in the forearm above the point at
which the dorsal branch is given off produces the following changes in the
sensibility of the hand.

Touch, prick, heat and cold are no longer appreciated over the little finger
and over the ulnar border of the palm. The extent of this absolute loss of
cutaneous sensation varies in each individual, and in no two cases is it exactly
the same. In one extreme form it may occupy the little finger, one-half of the
ring finger and more than one-third of the palm and dorsum of the hand, or
sensation may only be completely lost over the little finger and ulnar border
of the palm.

When the whole ulnar nerve is divided, the area of absolute loss of cutaneous
sensation lies between these two extreme limits, the amount of loss varjdng
with each individual. And it is this loss of sensation only which can be recog-
nised by pricldng the hand with a pin. If one finger and a half are insensitive
to a prick, the surgeon is satisfied that he has to deal with a " normal " ulnar
" completely divided " ; when only the little finger is insensitive, he doubts
whether the nerve is completely divided, or looks upon it as abnormally
distributed.

But in reaUty, the sensibility of the hand is disturbed over an area consider-
ably greater than that marked out by the analgesia ; and, if cotton wool is
used as the test for sensation, touches, easily felt elsewhere on the hand, Avill
not be appreciated over the whole of that portion assigned by anatomy to the
supply of the ulnar nerve. This area is bounded by a fine running through the
longitudinal axis of the ring finger back and front, continued on the dorsal and
palmar aspects of the hand to include the greater part of its ulnar half.

The whole of this border can be marked out easily with cotton w^ool, for,
as soon as it is passed, the patient appreciates touches that previously caused
no sensation, and, if he is intelligent and quick, the passage from the insensitive
to the sensitive area is found to take place at a line which varies very httle,
whether the stimuU progress is an orderly series from the ulnar to the racUal
side of the hand, or vice versa.

1 For the extent of the nerve sujiply of the hand determined by the method of residua^
sensibihty, vide p. 114.

INJURY TO THE PERIPHERAL NERVES 69

Thus, by using cotton wool as a test, sensation can be shown to be lost at a
line corresponding to the anatomical border of the ulnar nerve.

But there are other means of showing that sensation becomes defective at
this border. If a needle or pin is dragged lightly across the skin from the sound
to the affected half of the hand, the patient complains that the " feeling " it
produces changes as soon as this line is passed. This line can also be marked
out by an interrupted current applied in the following manner : Connect one
pole of the secondary coil with a large indifferent electrode, and the other pole
with a small electrode covered with wash-leather set in a handle containing a
key, so that the current can be thrown in and out at will. Remove the iron
core from the primary coil, then place the secondary coil at such a distance
from the primary, that the current applied through the smaller electrode is
easily appreciated on the normal skin. Even though it may be strong enough
to contract the small muscles of the thumb, such a current will not be
appreciated over the area within which sensation is lost to cotton wool.

Sensation to temperature also undergoes a change at the same border. A
test tube containing water at about 22° C, and one containing water at about
40° C, cannot be discriminated, though easily appreciated as cool or warm
over the normal sldn.

Thus, division of the ulnar nerve produces complete loss of sensation to
pain and temperature over the little finger and over a variable extent of the
palmar and dorsal surfaces of the ulnar border of the hand, rarely corresponding
even approximately to the anatomical borders of the ulnar nerve. But these
borders are accurately marked out by loss of light touch (cotton wool), and of
minor degrees of temperature and by inability to appreciate the interrupted
current applied in a definite way.

Between the boundaries of this loss of light touch and those of complete
loss of cutaneous sensibility lies a territory within which sensation is profoundly
changed. The extent of this area varies in each individual case. If the inter-
mediate zone be of considerable size, so that the condition of sensation within
it is easily investigated, then it will be found that not only is all sensation
abolished to light touch, to intermediate degrees of temperature, and to a
certain form of interrupted current, but painful stimuli produce an effect
different from that upon the normal skin. As soon as the anatomical border
is transgressed towards the ulnar side, a prick may become so disagreeable that
the patient immediately withdraws his hand. He complains that it causes a
feeling of " pins and needles," not only at the point pricked, but also widely
over the intermediate zone. Asked to localise the spot pricked, he may be
able to do so, but complains that the pain produced seems to him to be spread
over a large surface, or even to be in two places at once, such as the base of the
finger and the middle of the palm. Moreover, when tested with compasses,
the points cannot .be distinguished as causing two sensations, even when
separated from one another to the greatest extent possible within the inter-
mediate zone. An interrupted induced current, with no iron in the circuit,

70 STUDIES IN NEUROLOGY

cannot be appreciated within this area, but, if bare metal points are used, or
if the iron core is inserted into the primary coil, the stimulus causes pain, even
when the distance of the coils is adjusted to compensate for the increase of
strength produced by the presence of the core.

Thus, complete division of the ulnar nerve above the dorsal branch produces
the following changes : —

(1) Loss of sensation to pain, to extremes of heat and cold (ice and water at
50° C), and to painful interrupted induced currents over an area that may vary
greatly in size ; sometimes it includes the Uttle finger, the ulnar half of the
ring finger, and more than one-tliird of the palm and dorsal sm^face ; in other
cases it is reduced to the little finger and a strip on the extreme ulnar border
of the hand.

(2) The patient is unable to distinguish two widely separated compass
points, or to appreciate hght touch, minor degrees of temperature, and the
painless interrupted current over an area occupying the little and uhiar half of
the ring fingers, and that part of the palm and dorsum of the hand on the uhiar
side of an axial Hne drawn longitudinally through the ring finger. This corre-
sponds to the border laid down by anatomy for the supply of the ulnar nerve.

(3) The sensibility of the intermediate zone on the palm, the dorsum and
the ring finger may be characterised by an increase in the discomfort produced
by painful cutaneous stimuli, and by a wide diffusion and want of localisation
in the sensation produced by a prick.

§ 2. — Variation in the Extent of the Area supplied by the Ulnar

Nerve

Complete division of the uhiar nerve produces loss of sensation to light
touch over the whole of the little finger and over some part of the ring finger
back and front. In no instance was the sensibility of the ring finger to light
touch entirely unaffected. Of nine cases in which the nerve was proved at
the operation to have been divided, this anaesthesia occupied the ulnar half of
the ring finger in six, and this may therefore be taken to represent the usual
supply.

On the palm, the loss of sensation to light touch may occupy a border
directly continuous with the axis of the ring finger, or ma}?- swing out as far as
a line drawn from the cleft between the middle and ring fingers (fig. o).

Out of these nine cases loss of hght touch occupied half the dorsal surface
of the ring finger in six ; in one, a third of this finger was affected. In one
instance, this anaesthesia occupied two-thirds of the ring finger.

On the back of the hand, the border of the area insensitive to light touch
usually follows a line continuous with the axis of the ring finger, but in two
cases it swung out to the radial side to reach the tendon of the middle finger. ^

^ Under certain circumstances the presence of hairs on the dorsal surface of the hand may
make the determination of this border untrustworthy unless the hand be shaved (vide p. 156).

INJURY TO THE PERIPHERAL NERVES

Fig. 5.

To show the loss of sensation produced by complete division of the uhiar nerve. Loss of all forms
of cutaneous sensibility is represented by the black area. The parts insensitive to light touch and to
the intermediate degrees of heat and cold are enclosed within the black line.

Most of the cases will be found on Table II., p. 92.

A is the loss of sensation in Case 18; B, Case 17; E, Case 16; F, Case 14; G, Case 15; I, Case 19
(also reported on p. 207). The case from which C was taken (No. 83) will be found reported on
p. 208; that where the loss of sensation was represented by H, on p. 210 (No. 63). D was taken
from a man in whom the ulnar nerve had been divided; secondary suture was performed, and he was
not seen again until complete I'ecovery had occurred.

72 STUDIES IN NEUROLOGY

The ulnar nerve is usually divided by a transverse cut in the neighbourhood
of the wrist, which must also sever some of the branches of the internal
cutanous nerve descending to supply the hand. Thus, in most cases, the scar
bounds the upper or central border of loss to hght touch, and it is only where
the ulnar nerve has been injured at the elbow, or high in the forearm, that the
true upper limit of the ulnar supply can be determined. Six such cases have
come under our notice, in four of which this upper hmit ran round the wrist
at the level of the styloid process, and in two it formed a curved line about
1 cm. on the distal side of this point. Evidently, as far as hght touch is con-
cerned, division of fibres of the internal cutaneous nerve plays little part in the
form usually assumed by this border after division of the ulnar nerve at the
wrist, excepting when the anaesthesia is bounded definitely by the scar.

Thus, the extent of the loss of light touch produced by division of the ulnar
nerve seems to be remarkably constant, and it varies, if at all, within small
hmits only. The borders of this area are definite ; it does not merge gradually,
but passes abruptly into parts of normal sensibility.

The area of insensibility to pain, produced by division of the ulnar nerve,
differs fundamentally in every characteristic from the condition of parts
insensitive to light touch. For, not only is the extent of the loss of sensation
subject to great variation, but the difficulty in determining the amount of
this variation is increased by the indefinite nature of the borders of the analgesic
area. At no point can it be said that here loss to pain begins ; complete sensi-
bihty to pain merges gradually into complete insensibility with no sharp
dividing hne, and all attempts to mark out circumscribed areas of analgesia
are therefore unsatisfactory. But, taldng into account solely the area of total
loss of sensation to prick, the only certain result of complete division of the
ulnar nerve is to produce analgesia over the little finger and ulnar border of
the hand. None of our cases failed to show at least so much loss to prick. But,
in extreme instances, sensation to prick may also be lost over the ulnar half of
the ring finger and over an area on the palm and dorsum of the hand almost
co-terminous with the full uhiar loss of sensation to light touch. It is in such
cases that the surgeon, using a pin as his test for sensibihty, finds that loss of
sensation occupies exactly the area he expected.

Between these two extremes, every form of variation exists ; in no two cases
is the extent of the complete analgesia exactly the same, and so diverse are the
forms assumed by this loss of sensation that no form can be said even approxi-
mately to represent the normal. We have therefore represented the extent of
the loss, in each case, in the form of a series of diagrams, from which it will be
seen how great may be the variation (fig. 5).

Apparently, the extent of the area insensitive to hght touch, and that
of the area of absolute loss of sensation to prick, vary independently of one
another. A large extent of the uhiar half of the hand may be entirely insensi-
tive to pain, and yet the extent of loss to hght touch in no way exceeds that
found when the analgesia was confined to the httle finger. For this reason,

INJURY TO THE PERIPHERAL NERVES

the extent of the intervening zone of defective sensibility varies greatly. Its
characteristics are an imperfect discrimination of two compass points and an
inability to transmit light touch and degrees of temperature between about
22° C. and 40° C. It is, however, sensitive to pain, to ice, and to temperatures
above 45° C. But, in consequence of the ill-defined borders of this total loss
of sensation, the intermediate zone may sometimes be an area of very defective
sensibiUty, or it may be sufficiently large and sensitive for careful and certain
examination of its sensory pecuharities.

§ 3. — Loss OF Sensation produced by Division of the Ulnar Nerve,
WHEN ITS Dorsal Branch remains Intact

When the ulnar nerve is divided at the wrist, its dorsal branch not uncom-
monly escapes uninjured. Such an accident makes it possible to determine
the extent to which each of the two branches supplies the ulnar area of the
hand.

Fig. 6.

To show the loss of sensation produced by division of the uhiar nerve below its dorsal branch.
The area of total loss of cutaneous sensibility is marked in black. The parts insensitive to light touch
and to the intermediate degrees of heat and cold are enclosed within a black line.

Both these cases will be found on Table II. B, p. 94. A represents the loss of sensation in Case 20 ;
B the loss of sensation which preceded and immediately followed secondary suture in Case 24.

When the dorsal branch is intact, the border of loss to light touch coincides
on the palm with that found after complete division of the ulnar nerve. The
whole palmar surface of the little finger and the greater part of the ulnar half
of the ring finger are insensitive to- cotton wool. On the dorsum of the hand,
the loss of sensation may occupy the ulnar half of the two terminal j^halanges
of the ring, and the whole of the two terminal phalanges of the little finger ;
or the whole little finger and a small portion of the ulnar border of the dorsal
surface of the hand may be insensitive to light touch. But, wherever it may
be situated in any individual case, the border separating the loss of sensation
on the palm, from the normal area on the back of the hand, is an indefinite
one. Previously, whenever loss of light touch has been under discussion, the
borders of such loss have been spoken of as lines. That is to say, the passage,
from a part over which cotton-wool is appreciated to one where it no longer
produces any sensation, is so rapid, that for practical purposes it may be repre-
sented by a line. This is not the case when the dorsal branch of the ulnar
nerve has remained intact. The ulnar portion of the palm of the hand is

74 STUDIES IN NEUROLOGY

insensitive to cotton wool ; but, as the stimulus progresses towards the dorsal
surface, the point at which it first evokes a sensation is uncertain, and the area
of anaesthesia seems to merge gradually into the complete sensibihty of the
back of the hand.

The extent to which sensation to prick and to the extremes of heat and cold
is lost seems to vary greatly. It may be that the only absolute loss of sensation
is found over the terminal two phalanges of the httle finger on the palmar aspect,
and over the terminal phalanx behind ; or the whole ulnar third of the palm,
the whole palmar surface of the httle finger and its two terminal phalanges on
the dorsal surface may be entirely insensitive.

This absolute loss of sensation, however extensive it may be, merges gradu-
ally into the area of partial loss and is not constant. Like all parts where
sensation ta prick and to the extremes of heat and cold is defective, the extent
of the loss varies according to the temperature of the hand and the general
condition of the patient. Thus in Case 24 (Table II., fig. 6, b, p. 73), the
sensibility improved and again deteriorated, although the two ends of the
divided nerve remained effectively separated.

In most cases, where the dorsal branch is intact, the considerable extent
to which the borders of loss to Ught touch and to prick are separated from one
another, renders it particularly easy to determine the character of sensation
obtained from the intermediate zone. When pricked, the patient withdi"aws
his hand with an exclamation, as soon as the area is reached where Hght touch
is lost. Ice and water at 50° C. can be appreciated, water between about
22° and 40° cause a sensation of touch only. But, even though a prick can
be perceived, it produces a widely diffused, tingling sensation, and two
compass points are not distinguished, even when separated for a distance
of 4 cm.

The dorsal branch seems to supply sensibihty to hght touch to the lower
half of the ring finger on its uhiar aspect, and to the greater part of the ulnar
third of the back of the hand. If it remains intact, there may be no loss of
sensation to prick on the palm or first and second phalanges of the little finger
after division of the ulnar nerve. Or the extent of the area supplied by the
dorsal branch may be so small that all sensation is lost over the ulnar palm,
and the analgesia occupies the two terminal phalanges of the httle finger, and
even laps shghtly on to the dorsal surface of the hand.

Thus, it would seem that the part played by the two main branches of the
ulnar nerve in supplying sensation of hght touch to the hand varies httle, but
the border between the areas they supply, unlike any touch border yet described,
is not fixed ; the parts, where sensation is lost to light toucli, merge gradually
into the back of the hand, where sensation is unaffected. But there is great
individual variation in the extent to which sensation to prick and to the
profomider degrees of heat and cold is lost. No two cases are exactly ahke,
and any focus of absolute analgesia that exists is surrounded by a wide area
of partial loss to prick.

INJURY TO THE PERIPHERAL NERVES 75

§ 4. — Division of the Median Nerve

Usually, when the median nerve is divided, the skin over the dorsal and
palmar surfaces of the two terminal phalanges of the middle and index fingers
becomes insensitive to light touch, pain and temperature. But cutaneous
sensibility may also be lost over a wider area. The palmar aspect of the thumb,
the hypothenar eminence and the greater part of the median half of the palm
may be completely insensitive to prick. In such cases, the loss of all forms of
cutaneous sensation nearly corresponds to the area assigned by anatomy to
the supply of the median nerve. But so great a loss is not present in the
majority of cases. The extent to which the palm and the palmar aspect of the
thumb are affected varies greatly ; but on the dorsal surface of the index and
middle fingers, the boundaries of the analgesia are remarkably constant,
reaching as a rule to the folds of the skin over the first interphalangeal joint
of both fingers.

The extent to which sensation to pain and to temperature is completely
lost varies greatly and cannot be said to be exactly similar in any two cases.
But the area over which light touch cannot be appreciated is more constant.
Its borders usually extend from the radial edge of the thumbnail along the radial
border of the thumb to the fold at the base of the thenar eminence ; thence it
passes up the great central line of the palm to the cleft between the middle and
ring fingers. It includes a variable portion of the radial half of the palmar
surface of the ring finger and on the dorsal surface the radial third of the terminal
two phalanges of the ring finger, and the skin over the terminal two and a
half phalanges of the middle and index fingers. From the radial side of the
index finger the border sloj)es towards the thumb, running along the extreme
free edge of the first interosseous space, and thence extends up the thumb, to
end at the ulnar border of the nail. The area, over which hght touch is lost,
corresponds on the palm almost exactly with that assigned by anatomy to the
median nerve.

Although cotton wool is the best means of marking out this border, light
touch is not the only form of sensation which there undergoes a change.
Temperatures between about 22° C. and 40° C. are entirely unperceived as
soon as this line is passed, and the painless interrupted current, generated
with no iron in the circuit, ceases at this border to cause sensation, though well
appreciated on the normal skin.

Thus, after division of the median nerve, exactly as with the ulnar nerve,
an intermediate zone makes its appearance between the boundary for loss
of light touch and the boundary of those parts over which sensation is absent
to prick. Closer examination of this intermediate zone shows that sensation,
produced by stimuli appHed within it, has the same characteristics as that from
the similar area, caused by division of the ulnar nerve. A prick usually causes
pain more disagreeable in character than that of the normal sldn. The patient
has an urgent desire to withdraw his hand and cries out, or shows some obvious

76 STUDIES IN NEUROLOGY

sign of discomfort. The sensation produced is widely diffused and badly-
localised; it is said to be a "numb, tingling pain." So characteristic may
be this form of sensation, that the border at which light touch ceases to be
perceived can be frequently marked out by dragging the point of a pin Hghtly
across the sldn from normal to abnormal parts, noting at what point the
character of the sensation so produced undergoes a change.

Temperatures between about 22° C. and 40° C. are unperceived when
applied mthin this area ; but the more extreme degrees of cold and of heat are
usually well appreciated, although they cause a diffuse, badly localised, tinghng
sensation, unhke any effect produced upon the normal skin.

§ 5. — Variation in the Extent of the Aeea supplied by the

Median Nerve

Among the twelve cases, where the median nerve proved at the operation
to have been divided, there was but Httle variation in the extent of loss of sensa-
tion to Hght touch and minor degrees of temperature. In all, the ring finger
was affected to a greater or less degree, usually one-half (six cases) or one-third
(three cases) being anaesthetic ; but in two instances the anaesthesia occupied
a small portion only of its extreme radial aspect, and in one two-thirds of the
whole finger. On the palm, the border may vary between a line drawn through
the axis of the middle, and one drawTi through the axis of the ring finger. The
small variations which occur on the dorsal sm"face, in the extent to which the
index and middle fingers are insensitive, can be best appreciated from the series
of diagrams on fig. 7. The greatest variation occurs on the middle finger,
where the anaesthesia may extend over the two terminal phalanges or may
occupy the whole finger to the base. Thus, the extent of the loss of sensation
to light touch, and to minor degrees of temperature, is remarkably constant
and varies within small limits.

These differences are trivial compared with the wide variations in the
extent of the loss of sensation to prick, variations so profound that no two
instances can be said to resemble one another exactly. In estimating the extent
of this analgesia, it is important to use cases only in which the nerve was proved
by operation to have been divided, and to choose only such observations as
were made as soon as possible after the occurrence of the injury, before recovery
could have begun.

Twelve of our cases come up to this standard. Among them five showed
so large an amount of loss of sensation to prick, that the whole of the palm
usually assigned to the median nerve, together with the palmar aspect of the
thumb and both index and middle fingers, was analgesic. In fig. 7, l, the
loss of sensation to prick on the palm was somewhat less extensive, but one-
third of the ring finger was analgesic. In every case, the extent of this loss of
sensation was different, until in fig. 7, a, it reached the smallest proportions
we have yet seen. Here, scarcely the terminal two phalanges of the index

INJURY TO THE PERIPHERAL NERVES

Fig. 7.

To show the loss of sensation produced by division of the median nerve. The area of complete
cutaneous insensibility is marked in black. The parts insensitive to light touch and to the intermediate
degrees of temperature are enclosed within a line.

Most of these cases will be found on Table I., p. 90.

A represents the loss of sensation in Case 7; B, Case 11; C, Case 13; D, Case 6; E, Case 3;
F, Case 12; G, Case 8; H, Case 4; I, Case 9; J, Case 10; L, Case 5. K is taken from a woman who
completely divided her median nerve in the neighbourhood of the elbow. We examined her on several
occasions, but she disappeared before recovery of sensation began.

78 STUDIES IN NEUROLOGY

and middle fingers were affected, and prick could be appreciated over the whole
of the palm of the hand and over the palmar aspect of the thumb.

Thus, it is impossible to lay dowTi any general rule, even with regard to
the usual extent and distribution of loss of sensation to prick when the median
nerve has been divided. We can only say, that, when it reached its wide
extent, it almost corresponded to the area of loss of sensation to Ught touch,
or, when the analgesia was reduced to its smallest proportions, scarcely the
whole of the terminal two phalanges of the index and middle fingers were
rendered insensitive to prick. Between these two extremes, every variety
may occur.

It might be supposed that the presence of a considerable area of loss of
sensation to prick on the palm depended upon injury to the descending branches
of the external cutaneous nerve. But in the patient from whom fig. 7, k, was
taken the nerve was divided by a wound in the fold of the elbow. Moreover,
in fig. 7, L, the extent of the analgesia was larger than in any other instance
that has come under our notice, and yet the nerve had been divided through
a small punctured wound at the wrist, which could not have injured any
considerable number of fibres of the external cutaneous.

§ 6. — Division of both Median and Ulnar Nerves

An extensive wound of the wrist may divide both the median and the
ulnar nerves, causing paralysis of all the intrinsic muscles of the hand and
widespread loss of sensation. To j)roduce such great destruction the wound
must be unusually severe, and, commonly, one or other nerve, though injured,
escapes complete division. This is the condition in the majority of those cases
where the median and ulnar nerves are supposed to have been divided. But
amongst om- patients were two in whom both nerves were seen to be cut across
at the time of the original wound, and one, where they were divided seven weeks
after the original injury for the purpose of secondary suture.

Taken in connection with a number of cases where both nerves were gravely
injured, this material, though small, is sufficient to determine the extent to
which fight touch is affected when the two nerves are completely divided. But
the loss of sensation to prick varied so greatly in the three instances of
undoubted division, that it is impossible to say to what extent this form of
sensation is most commonly lost.

Sensation to fight touch is abolished by this injury over the whole palm
and over the palmar aspect of the thumb and all the fingers. The outline of
this area on the thumb corresponds, when uncomplicated by injury of other
branches, to the similar border produced by division of the median nerve,
and, like it, varies in the extent to which the thenar eminence is involved.
Sometimes the anaesthesia over the proximal part of the base of the thumb is
too extensive to be due entirely to destruction of the median nerve, and is
probably caused by di\asion of fibres from the external cutaneous descending

INJURY TO THE PERIPHERAL NERVES

on to the palm. Any cut, running across the wrist from side to side completely,
must tend to divide these branches.

On the posterior surface, the border of the area over which light touch and
minor degrees of temperature are lost varies, according to whether the dorsal
branch of the ulnar nerve has been severed or not. In the three cases of
complete division of both main trunks, the ulnar nerve had been divided above
the point at which this branch was given off. The loss of sensation on the
back of the hand, therefore, corresponded to that seen after complete division
of the ulnar nerve. On the dorsal surface of the index and middle fingers,
the anaesthesia extended to the proximal fold over the first interphalangeal
joint in two cases, and to a point half-way between this fold and the knuckle
in the third. On the thumb, the border ran from the ulnar aspect of the base

Fig. 8.

To show the loss of sensation produced by complete division of both median and ulnar nerves.
The area of comiDlete cutaneous insensibility is marked in black. The parts insensitive to light touch
and to the intermediate degrees of temperature are enclosed within a line.

These cases will be found on Table III., p. 96.

A shows the loss of sensation in Case 26, B in Case 28, and C in Case 25.

of the nail to the dorsal aspect of the free edge of the first interosseous space.
Thence it passed up the radial aspect of the base of the index to join the fine
on the dorsum of this finger.

The extent to which light touch and the minor degrees of temperature were
lost corresj)ondecl exactly to the loss of sensation j)roduced by division of the
ulnar nerve, added to that caused by division of the median. Occasionally,
the loss on the palmar aspect of the thumb was a little increased by destruction
of branches of the external cutaneous running downwards over the wrist.

To prick, the loss of sensation varied so greatly that an attempt to describe
in detail its boundaries in each case would be wearisome, and the reader is
referred to fig. 8. The greatest loss appeared in Case 25 (fig. 8, c), where the
whole palm and palmar aspect of the thumb were insensitive to prick. But
it must be remembered that, in this patient, all the structures on the front of

80 STUDIES IN NEUROLOGY

the wrist had been di^dded to the bone, and amongst them must have been
inckided the descending branches of the external cutaneous nerve. In both
the other cases, loss of sensation to prick was less extensive on the palm (fig. 8),
and they probably belonged to the group in which the median nerve suppUes
exclusively the fingers only.

On the dorsal surface, the index, middle and ring fingers were insensitive
from the tip to the lowest fold over the first interphalangeal joint in two of
the cases ; in one, the dorsum of the index seemed to be sensitive to prick.
In all, the whole of the little finger and a varying portion of the uhiar aspect of
the dorsum of the hand were analgesic. The material at our disposal is small ;
but it would seem that division of the median and ulnar nerves tends to produce
the following results : — •

(1) Sensation to Hght touch is lost over the whole of the palm. Loss of
sensation on the back of the fingers extends at least to the first interphalangeal
joint ; and if the ulnar nerve has been cli\dded above its dorsal branch, the
anaesthesia invades the whole of the ulnar half of the middle finger, the whole
little finger, and a variable extent of the dorsal surface of the hand.

(2) The loss of sensation to prick varies greatly in extent. In one instance,
the whole palm was insensitive to prick. In the remainder, the thenar eminence
and the extreme radial portion of the hand were sensitive to this form of
stimulation. On the dorsal surface, the index, middle, ring, and little fingers
became analgesic over an area which varied in each case (fig. 8).

CHAPTER II
recovery of sensation after division of the nerves of the hand

§ 1. — General Statement of the Phenomena of Recovery

The ultimate consequences of division of one of the nerves of the hand
depend entirely upon the treatment adopted. If the nerve be sutured, and
the wound heal by first intention, sensation may return to a condition indis-
tinguishable from that of the normal skin. And in the progress of such return,
the hand will pass through stages that throw much light on the structure and
functions of peripheral nerves.

Division of the nerve leads at once to the production of an area of absolute
cutaneous insensibility, surrounded by an area of loss of sensation to stimuli,
such as light touch and the minor degrees of temperature. The relative extent
of these two areas differs greatly in each individual case, and the first definite
sign of recovery is shown by an increase in size of the intermediate zone between
them. At the end of a variable period after division of the nerve, the analgesia
begins to retreat from the palm of the hand and occupies the fingers only.
Gradually, it passes up the fingers joint by joint, until at last there is no part
of the hand or of the fingers where prick cannot be appreciated. During the
whole of this period, the area of loss of light touch remains as well defined as
on the day of the accident ; it takes no part in the recovery of sensation, and
yet, at the end of several months, the whole of that part of the hand sui^plied
by the affected nerve has become sensitive to painful stimulation.

Even pressure with blunt objects, such as a pencil or the head of a pin,

causes pain, and the patient complains that an accidental knock over this part

of the hand is extremely unpleasant. In quality, the sensation from the affected

half of the hand resembles that of the intermediate zone, which was found

between the border for light touch and the border for prick shortly after the

accident. Light touch is entirely unperceived, and two points of the compasses

cannot be discriminated, even when widely separated. A prick causes a diffused

sensation of " pins and needles," or " tingUng," which is locahsed, not only

at the point of application of the stimulus, but widely over the affected part of

the hand. A test tube containing water at any temperature below 20° C. is

appreciated as cold, and it matters little whether it contain ice or water at

18° C, both are said to be '* ice cold." Water at 50° C. causes a stinging,

corresponding to the unpleasant aspect of the sensation produced on the normal

hand by too hot water. This may or may not be accompanied by a true
VOL. I. 81 G

82 STUDIES IN NEUROLOGY

sensation of heat, according to the stage of recovery reached by the affected
hand. But whether true heat be present or not, patients usually speak of the
" stinging " produced by water at 50° C. as " hot " or " burning," because
no other common natural stimulus is capable of causing this pecuHar, unpleasant
sensation.

In the earlier period of recovery, whilst the analgesia is retreating from the
hand, all sensation of true heat is, not infrequently, absent. The recovering
parts are sensitive to cold and to the unpleasant " burning " or " stinging "
aspect of a hot stimulus, but not to heat itself. Sensations of cold play,
therefore, a greater part in the effect produced by this area of the skin upon
consciousness, and this part of the hand always " feels colder " than normal.
Ultimately, however, temperatures of 50° C, or above, can be appreciated
without hesitation as heat. Yet, throughout this stage of recovery, so long
as light touch is completely absent over the affected area, water at 40° C.
and below produces no sensation of warmth ; it cannot be distinguished from
water at 25° C, and is said to be neither hot nor cold.

Thus, when the whole portion of the hand affected has become sensitive to
prick, the sensations evoked closely resemble those arising from the intermediate
zone in their diffuseness and want of strict localisation, and in the fact that
degrees of temperature between about 25° C. and 40° C. cannot be appreciated.

But, although sensation from the whole affected parts of the hand closely
resembles in quahty that of the intermediate zone present immediately after
the nerve has been divided, yet, in intensity and rapidity of reaction, the
sensitiveness of the recovering parts is considerably greater. We have no
satisfactory measure of the intensity of pain, and can judge only by the state-
ment and behaviour of the patient. By such standards it is certain that a prick
now produces a more unpleasant sensation over the same parts than shortly
after the accident, before recovery could have begun. Moreover, cold and heat
are felt with greater promptitude over the recovering area of the hand than over
the intermediate zone between the touch and prick borders. Thus, although
the quality of the sensation that can be evoked from those parts of the hand
where sensibility to prick has returned, closely resembles that of the inter-
mediate zone, the intensity, and, therefore, the extent of the innervation, has
considerably increased.

At the close of tliis stage of recovery, all analgesia has disappeared, leaving
the affected part ^f the hand in a condition of sensibiUty, with the following
characteristics. Light touch cannot be appreciated. Two compass points,
even widely separated, cannot be discriminated. Sensation is lost to tempera-
tures between about 25° C. and 40° C. Prick causes a widely diffused and
pecuharly disagreeable sensation, and temperatures below 20° C. uniformly
produce a sensation of ice cold, irrespective of the degree of cold registered by
the thermometer. A stimulus between 45° C. and 50° C. will, when recovery
is well advanced, be perceived in most cases as warmth, but above 50° C. it
will be called " hot," even in the earlier stages of recovery, on account of the

INJURY TO THE PERIPHERAL NERVES 83

"stinging" it produces, whether true temperature sensation be jDresent
or not.

In this condition, the affected parts of the hand may remain for several
months. Then, if the nerve has healed well, the border for loss of light touch
is found to be no longer so definite as before. At first, that portion nearest
to the ^\Tist loses its sharpness and distinctness ; then the boundary on the palm
or on the dorsum of the hand becomes indefinite. Gradually the whole palm
and, in the case of the ulnar nerve, the back of the hand becomes sensitive to
light touch, the fingers alone remaining anaesthetic . At last, even the fingers
regain their sensibility to Hght touch. One of the earUest signs of return of
this form of sensation is the power of discriminating intermediate degrees of
temperature.

As soon as light touch begins to be appreciated over the affected parts,
water from about 35° C. to 40° C. again produces a sensation of warmth, and
any two temperatures between 25° C. and 40° C. can be discriminated, the one
being said to be warmer or cooler than the other.

Month by month, the sensation caused by painful stimuU grows less and less
diffused and loses its tinghng character. Month by month, the power of
distinguishing between two compass points improves. But, if the nerve has
been completely severed, the sensibility of the parts does not as a rule become
normal for more than two years. The old border for loss to touch can still be
marked out by a change in the character of the sensation produced by cotton
wool, a change consisting in diminution of intensity and Mdde diffusion from
the point stimulated. An even better method of marking out this border is
to drag a pin lightly across the palm from normal to affected parts. At the
original hne of loss of touch the point becomes more painful, and the pain
produced is widely diffused. This change in quahty remains many months
after sensibihty to Ught touch has been restored to all the affected parts of
the hand.

Under favom'able conditions, even these differences may disappear, and the
sensibility of the affected area may become indistinguishable from that of the
normal skin.

Should the wound have suppurated, or the nerve have been left unsutured,
sensation may still return by the same stages, but the time of restitution will
be prolonged. Whenever heaUng of the nerve is rendered less easy by want of
apposition of the divided ends, or by unfavourable conditions in the wound,
such as suppuration, the final recovery of sensation may be incomplete.

But the power of recovery possessed by a sensory nerve, even under the
most unfavourable conditions, is remarkable. We collected the names of all
those who had been admitted to the London Hospital for injury to some
peripheral nerve between the years 1892 and 1902. Several of these persons
could not be traced, but many presented themselves, and were examined by us.
Among them were fourteen cases where there was reason to suppose that the
ulnar nerve had been divided, and eight of division of the median nerve. Out

STUDIES IN NEUROLOGY

of these twenty-two patients, fourteen had recovered sensation so completely,
that no difference could be discovered between the two hands. In one man,
where primary suture had been performed four years before he came under our
observation, no recovery had apparently taken place. He was watched for a
time, and, as no improvement occurred, further operation was suggested ; from
that time he disappeared. But, although our observations are here incom-
plete, we can at any rate state with certainty that in rare cases no material
recovery may take place within four years.

Recovery may be arrested at the end of the first stage, leaving the hand
sensitive to pain and to the more extreme degrees of heat and cold, but
insensitive to hght touch. Such cases must be uncommon ; we have seen one
only.

Case 1. — Complete absence of sensation to light touch and minor degrees of temperature, more
than three years after primary suture of the median nerve, in spite of restored sensibility to prick.

On December 31, 1898, Henry S. cut his left wrist with a broken bottle, and came to the London

Hospital at once. The tendons of the flexor sublimis, flexor carpi
radialis, and palmaris longus, had been divided, and the median
nerve was completely severed. The tendons and the nerve were
reunited, and the wound is said to have healed by first intention.
When we first saw him in February, 1902, he said that his
hand only troubled him in cold weather. The abductor and
opponens poUicis acted voluntarily, and reacted to an interrupted
current. Cotton wool was not appreciated over the area shown
in fig. 9, and within these limits he was insensitive to temperatures
between 20° C. and 40° C. Even 45° C. was rarely said to be
anything but a touch. Yet ice and water at 50° C. were every-
where called cold and hot correctly. Nowhere over the median
half of the palm could the two jjoints of the compasses be
discriminated, even when they were separated to a distance of
2 cm., although, on the normal hand, he made no mistakes
when they were 1 cm. apart.
The whole of this area was sensitive to the prick of a needle, and the sensation so caused was
not only more disagreeable than over the normal parts, but was widely diffused, " running about
the hand." The borders of that jjart of the hand sujj plied by the median nerve could be marked
out, by noting the points at which a needle dragged across the palm began to cause this curious
diffused sensation.

If the hand becomes sensitive to prick, hght touch will ultimately be appre-
ciated over the affected parts ; ^ but this restoration is not uncommonly
incomplete. Any stimulus then causes a sensation which differs from that
produced over normal parts in its diffuseness. Should the stimulus be of such
a nature that it evokes pain, this pain Avill become a more prominent feature,
and when a pin is dragged hghtly across the skin, the patient withdraws his
hand as soon as the border of the affected area is crossed, saying that it is more
painful than over normal parts. Out of twenty-three cases, seven still showed
this hne of changed sensibiHty five years after the injury, and it was evident

^ To this rule we have seen one exception only (Case 1, quoted above).

Fig. 9.

To show the area insensitive
to cotton wool and to inter-
mediate degrees of heat and
cold in Case 1. The whole
hand was sensitive to prick
and to the more extreme
degrees of temperature.

INJURY TO THE PERIPHERAL NERVES 85

in an old man whose ulnar nerve had been divided fifty-nine years before he
came under our notice.

Whenever this line of change is present, the balance has not been re-estab-
lished between that form of sensation evoked by a prick and that sensibihty
which responds to hght touch. Light touch and the intermediate degrees of
temperature can be appreciated. But, as the sensitiveness to these stimuli
is less than normal, the diffuse and disagreeable characteristics of the earlier
form of sensibility still intrude themselves, even with stimuli that are not
painful over the normal skin. Whenever this line of "change is definite, the
power of discriminating two compass points will be found to be diminished,
a sign that the highest forms of sensation have not yet completely returned.

Case 2. — To show hoiv the character of the sensibility of affected parts may remain cJmnged six
years after division of the median nerve, in spite of return of sensation to light touch.

In 1897, G. R. P. cut his left wrist with broken glass, and the wound was stitched at once
without an anasthetic. Sensation was completely lost, according to his account, over the index
and middle fingers, and was changed in the palm. When we saw him in February, 190.3, he
complained that " although I can feel, I cannot define what I touch." He was a medical student,
and daily noticed this inability of the left hand. He could not use his left hand for palpation,
and if he was told to feel resistance in the abdomen he could not localise it, although he could
appreciate the pressure against his hand. He complained that, in cold weather, the index and
middle fingers became almost powerless.

The outer thenar group of muscles (abductor and opponens pollicis) were wasted, but both
muscles acted voluntarily and reacted to the interrupted current.

The whole hand was sensitive to light touch with cotton wool, to the prick of a pin, and to
temperatures of 22° C. and 38° C. But, if a pin was dragged across the palm from the ulnar
towards the radial aspect, the sensation changed profoundly at a line corresponcUng to the border
of the median area. On the radial side of this line, the point caused a sensation which spread
widely, and produced tingling in the fingers. When the stimulus was repeated, he had an
irresistible desire to scratch the part affected.

Over this area, on the radial half of the hand, he made two mistakes in ten stimulations with
the compass points at 2 cm. At 1-5 cm., applied transversely, the mistakes were more numerous
(2 1 7 r' 3 w)- -^^^f' oil * similar part of the sound hand, his answers were perfect when the compass
points were separated for not more than 0-75 cm.

In order that this fine of change may make its appearance in its charac-
teristic form, the parts affected must have been sensitive for a considerable
period, during recovery, to pain and to the more extreme forms of temperature
alone. Then, the old boundary for loss of light touch will be marked by a
change in the character of the sensation, for many months after the whole
hand has become sensitive to all forms of cutaneous stimulation. But, when-
ever the two forms of sensation have been restored 'pari passu, this line of
change cannot be discovered.

No material part in this return of sensation to Hght touch can be attributed
to overlapping fibres from the uninjured nerve trunk. For a comparison of
the extent of the area insensitive to this stimulus produced by complete
division of the uhiar or of the median nerve shows, that they must overlap
one another to a slight amount only. Out of the nine cases where the ulnar

86 STUDIES IN NEUROLOGY

nerve was divided, the ansesthesia occupied half the ring finger in three, one-
third in three, and less than one -third in one ; in two, more than one -half the
ring finger was insensitive to light touch. Out of twelve cases of division of
the median nerve, sensation to light touch was lost over one-half the ring finger
in six, one-third in three, over less than a third in two, and over more than one-
half in one instance. In no case, where either nerve was proved to have been
divided, Avas the ring finger entirely unaffected. Thus, on the ring finger at
any rate, the overlapping must be at most one-third of the breadth of the
finger.

On the palm, the area insensitive to hght touch has an outline which
varies in each case. But here also the evidence points to no considerable over-
lapping between the supply of the median and uhiar nerves, as far as sensation
to hght touch is concerned.

The remarkable length of time required for the return of this form of sensa-
tion after complete division of the nerve, and the extraordinary fixity of the
boundaries of the ansesthesia, all show that ultimate recovery is due to return
of conduction, rather than to substitution by the overlapping fibres of the
uninjured nerve.

But the ill-defined borders and the comparatively small extent of the total
analgesia, and the fact that a large part of the palm rarely becomes insensitive
to prick from a lesion of one nerve only, all jDoint to much overlapping of the
fibres that conduct pain impressions. Such overlapping should lead to rapid
restoration of sensibiUty to prick, and in some cases possibly forms a factor
when sensation returns with unusual rapidity. Commonly, no wide loss to
prick on the palm follows division of the median nerve, because the fibres
which conduct this form of sensation are supplied from both nerves. But,
supposing the nerve supply of the median palm came overwhelmingly from
the median, division of this nerve would produce at first total analgesia. This
might rapidly pass away, to some extent, as soon as the few fibres of the ulnar
nerve to the median palm became capable of supplying sufficient sensibility
for the transmission of impulses. This certainly forms an important feature
in the recovery of sensation to prick after division of the volar branch of the
ulnar nerve.

Thus, a girl of 17 (Case 24)^ divided her ulnar nerve below the dorsal branch.
The divided tendons and the ends of the nerve were dealt with the same day,
and the wound healed by first intention. At first, sensation to prick was lost
over a small area in the centre of the ulnar palm. This loss rapidly disappeared,
leaving an area of ansesthesia to light touch over the palmar aspect of one and
a half fingers and over the uhiar half of the palm. During the remainder of
the summer, the condition of the hand improved, but remained stationary
throughout the earlier part of the winter. Then, sensation to j)rick began to
deteriorate, and the state of the nerve was therefore explored. At the operation
an extraordinary condition was discovered, which prevented all possibility

^ Reported in full on p. 209.

INJURY TO THE PERIPHERAL NERVES 87

of union. The upper end of the nerve had been sutured to the divided tendon
of the flexor carpi ulnaris, the lower end of the nerve to one of the tendons of
the flexor sublimis digitorum. Thus, all the return of sensation to prick,
which occurred during the summer months, must have been due to the inner-
vation of the parts affected by the dorsal branch of the ulnar nerve, which
had remained intact. The subsequent deterioration was probably caused
by the numbing effect of the cold weather on a part sensitive only to prick
and to extremes of heat and cold.

With so much overlapping of nerve supply, complete recovery of sensibility
to prick might occur, without union of the divided nerve, by a further develop-
ment of those fibres in the uninjured nerve which normally supply the affected
parts. In areas where sensation to prick is only partially lost, such substitution
undoubtedly occurs, as we have shown by the above example. But there is
no evidence to show that restoration of sensation can be produced in analgesic
parts without union of the divided nerve. In one instance (Case 83), where
the ulnar nerve had been operated upon repeatedly and portions removed
so as effectually to prevent all chance of its reunion, sensibihty to prick showed
no signs of return. The fibres of the median seem to have made no attempt
to encroach on the area of total analgesia, produced by the original destruction
of the ulnar nerve.

Sometimes, it is necessarj^ to divide an injured nerve, after sensibility
to prick has already begun to return to the hand, that more perfect union may
be obtained. Wherever such an operation has been performed, the parts
that had begun to recover sensibihty became again insensitive to prick, a proof
that the recovery must have been due to union, however imperfect, of the
divided nerve. Impulses from the recovering parts had passed up the injured
trunk, and not up one of the normal nerves. This contention is supported
by the following instance (Case 11).^

In May, 1901, a stonemason cut his right forearm with broken glass, dividing
the median nerve. So httle improvement had taken place up to April, 1902,
that it was determined to explore the wound. The two ends of the nerve
were found to be widely retracted, and between them lay what appeared to
be a strand of connective tissue. The ends were freshened and united. After
the operation the extent of the total loss of sensibility to prick had distinctly
increased, showing that the slight recovery which had taken place must have
been due to the strand of tissue that was found between the two ends of the
divided nerve.

§ 2. — Recovery after Division of Particular Nerves

When all the cases of nerve injury to the hand are massed together, certain
general principles emerge clearly. But as soon as each constituent group is
analysed, the number of cases becomes so small that general conclusions are

^ Reported in full on p. 204.

88 STUDIES IN NEUROLOGY

overwhelmed in the special conditions surrounding each particular instance.
Nevertheless, we have arranged our records in tabular form, and shall now
consider more in detail the manner in which sensation is restored after injury
to each of the nerves supphdng the hand. On these tables, the time of re-
covery of each of the great forms of sensation is expressed in days. But it
must be remembered that in many cases these dates are necessarily only approxi-
mate. A man, whose median nerve had been united, would be asked to come
on a particular day. But perhaps he was at work and refused, or had changed
his addi'ess and did not receive our request, or simply did not trouble himself
to obey, saying his hand was " all right." Before he could be found, or other
arrangements made, several weeks might elapse. When ultimately he pre-
sented himself for examination, the particular form of sensibility, which had
so nearly feturned on his previous visit, would probably have been restored
completely. What date are we to assign for this return ? If we enter the
return as complete on his previous visit, we shall have antedated it by perh^ips
a few days ; if we say it had returned by the date of his next visit, it is certain
that we shall overstate the time necessary for the restoration of this form of
sensation. Thus, although all the dates are given in terms of days, it must
not be thought that our observations warrant any such precision ; days have
been adopted as our unit solely to avoid the awkwardness of fractions of a
week.

(A) Median Nerve. [Table I.]

In six cases of primary suture, where the wound healed without compUca-
tion, the period between the operation and the first return of sensation averaged
65 days.

Out of these six cases the shortest period occupied was 44 days, the longest
92. It may justly be objected, that sensibility to prick might return over
large areas equally at the same time, and that the date of an obvious diminu-
tion in the size of the analgesic area does not represent the time at which re-
covery begins. This is probably true. The loss to prick has indefinite borders ;
it merges into an area of varying extent, within which sensibility to the stimulus
is greatly lowered. For a time, considerable recovery might, and almost
certainly does, take place Avithout materially pushing back the border of
absolute loss of sensation, retmn of function being confined mainly to the
outlying zone of diminished sensibihty. When the median nerve is divided,
this is pecuHarly liable to occur. For the sensibihty of the median palm to
prick is always somewhat lowered by such an injury, and it wdll depend upon
the extent of this loss, whether the analgesia appears to be confined to the
fingers or to occupy the greater part of the palm suppHed by the median nerve.

If the nerve has been reunited, and the wound has healed well, the area of
total loss to prick will begin to grow smaller in about 7 to 11 weeks, and
the palm then recovers rapidly. Three to eight weeks later, total analgesia
will be found on the fingers only; but here the skin may remain insensitive,

INJURY TO THE PERIPHERAL NERVES 89

especially over the terminal phalanges, for a considerable period. Finally,
the whole of the affected area becomes sensitive to prick in about seven months,
or 200 days, the average of four uncomplicated cases, in which the records
are perfect, was 190 days.

We have already pointed out that the area of absolute analgesia is in some
cases confined to the fingers ; but, in many instances, it occupies a greater
or less extent of the radial half of the j)alm of the hand. We beheve that when
absolute loss of sensation to prick is found on the palm, recovery begins at a
somewhat earlier date than if this loss is confined to the fingers.

Any want of health in the wound retards recovery to a remarkable degree.
In Case 7, slight suppuration took place in the original wound, which appeared
ultimately to heal. Sensation began to return after 68 days ; then no further
recovery took place for five months. During this time, a swelHng appeared
on the site of the injury which was found to contain pus, evidently due to
contamination of one of the deep stitches. In consequence of this deep sup-
puration, the return of sensation to prick was prolonged over a period of 230
days, rapid recovery following the evacuation of a small abscess.

Light touch began to be appreciated at times which varied from 173 to
324 days after sutm-e of the nerve. Among four complete cases, the average
time was 262 days. Here, again, the figures are only approximate ; for, during
the early stages of recovery, the condition of sensibihty to Hght touch depends
on cii'cumstances out of the control of the observer. If the day is bright
and warm and the patient in good bodily condition, cotton wool may be appre-
ciated faintly, but with certainty, on the palm of the hand. A week later,
in the bitter cold of early spring, the same parts may be entirely insensitive
to light touch. The length of the time required before light touch (cotton
wool) could be appreciated on every part of the affected hand varied from
331 to 468 days after suture, an average in three cases of 387 days.

But this in no way completes the recovery of sensation. Long after Ught
touch can be appreciated over the affected area, all stimuH cause a more dis-
agreeable sensation than over normal parts. When a pin is dragged Hghtly
across the skin, the borders of the area that was once anaesthetic can still be
recognised by the change in character of the sensation produced by the point.
At last, in a successful case, even this line of change disappears. We have
been able to follow two cases only up to this condition ; in No. 3 the line of
change disappeared from the affected hand 419 days after suture of the nerve.
This must be unusually early, for in No. 5, the hne of change was not aboUshed
for 877 days after the injury, and in two patients, whom we have watched for
over two years, this sign of defective sensation is still present.

Whenever this line of change is present, the appreciation of two compass
points is defective. One patient only recovered complete power of discrimi-
nating between two points, whilst in one it still remains defective 945 days
after suture when the points are not more than 2 cm. apart.

Neither simultaneous injury to tendons nor paralysis of the muscles supplied

STUDIES IN NEUROLOGY

TABLE I.—

Case.

Date of Injury.

Nature of Injury.

Operation and Result.

No. 3, W. B.

No. 4, A. C.

No. 5, T. P.

No. 6, S. H. .
[Vide p. 202.]

Dec. 19, 1901

Glass cut of wrist. Many tendons divided. Primary suture, Dec. 19.
Nerve seen to be divided (H. H. and J. S.) Healed well

Dec. 22, 1902 Glass cut of -nTist. No tendons divided.
Nerve seen to be divided (J. S.)

,Oct. 2, 1902 i I^ife cut of -vvrist. No tendons divided.
Nerve seen to be divided below a high
branch to the thumb muscles (J. S.)

Primary suture, Dec. 22.
First intention

Primary suture, Oct. 4.
First intention

Oct. 3, 1903 Razor cut of wrist. Many tendons divided, i Primary suture, Oct. 4.
Nerve completely divided i Healed well

No. 7, W. J. K. Sept. 11, 1902

No. 8, E. E. P.

Glass cut of wrist. Many tendons divided. Tendons sutured, Sept.
Nerve completely divided (J. S.) 11. Nerve sutured,

Sept. 19. Shght sup-
puration. In May,
1903, a stitch abscess
was opened and the
wound healed firmly

Feb. 7, 1903 Cut with coal. No tendons divided,
completely divided (J. S.)

Nerve

No. 9, M. A. G. Aug. 24, 1902 Glass cut of \m.st. No tendons divided.

I Nerve completely divided (J. S.)

No. 10, C. W. ... Jan. 21, 1905 Glass cut of wrist. Palmaris longus tendon

divided. Median nerve divided

No. 11, D. J. T.

[ Vide p. 204.]

May 6, 1901 Glass cut of forearm 3 cm. above fold of
wrist. No tendons divided. At operation
for secondary suture ends of nerve were
found 4 cm. apart (H. H.)

No. 12, C. F. ... Sept. 23, 1903 ■ Cut with chisel 6 cm. above fold of wrist.

Median nerve only divided (J. S.)

No. 13, P. D.

Primary suture, Feb. 9,
1903. Wound healed
by granulation

Primary suture, Aug. 25,
1902. Wound healed
by granulation

Primary suture, Jan. 21,
1905. First intention

Secondary suture. May
16, 1902 (375 days).
First intention

Secondary suture, Feb.
22, 1904 (153 days)

Glass cut of wrist. No tendons divided. At | Secondary suture, Feb. 6,
secondary suture ends of median nerve 1905
were embedded in fibrous tissue. No union
(J. S.)

INJURY TO THE PERIPHERAL NERVES

MEDIAN NERVE

Return of Sensation.

Protopathic.

Epicritic.

Final Resxilt.

Muscles.

Began March 7, 1902

(78 days).
Complete June 4, 1902

(166 days)

Began Feb. 4, 1903 (44

days).
Complete July 12, 1903

(202 days)

Began Nov. 26, 1902

(55 davs).
Complete May 24, 1903

(233 days)

Began March 30, 1904

(178 days).
Complete April 27, 1904

(205 davs)

Began Nov. 26, 1902
(68 days). Eemained
almost stationary
from Dec, 1902, to
May, 1903.

Comi^letely returned
July 15, 1903 (299
days)

Began May 13, 1903

(92 days).
Complete on Jan. 20,
1904, when he was
again found

Began Oct. 29, 1902
(65 days)

Began March 15, 1905

(54 days).
Complete June 29, 1905

(158 days)

Began Dec. 21, 1902

(220 days).
Complete Jan. 25, 1903

(254 days)

Began April 5, 1904

(42 days).
Complete Aug. 28, 1904

(187 days)

Began March 8, 1905

(30 days).
Complete Aug. 27, 1905

(202 days)

Began June 11, 1902

(173 days).
Complete Dec. 17, 1902

(363 days)

Began Sept. 6, 1903

(258 days).
Complete Nov. 18, 1903

(331 days)

Began Aug. 23, 1903

(324 days).
Complete'Jan. 13, 1904

(468 days)

Began July 8, 1905 (642
days)

Began July 15, 1903

(299 days).
Terminal phalanges

still affected, Aug.

19, 1903 (334 days)

Was lost again.

On Aug. 24, 1904, he
showed a line of
change only (560
days)

Began Jan. 31, 1904

(625 (days).
Complete April 10, 1904

(695 days)

Began June 18, 1905
(469 days)

Line of change disappeared
Feb. 11, 1903 (419 days).

Compasses almost perfect
at 1-5 cm., June 3, 1903
(530 days)

Slight lino of change only.
Compasses perfect at
1 cm., Aug. 20, 1905 (972
days)

Line of change disappeared
Feb. 26, 1905 (877 days).

Compasses not quite per-
fect at 3 cm., May 6,
1905 (945 days)

Disappeared from observa-
tion Aug. 19, 1903, with
line of change to prick,
and some loss of epicritic
sensibility over terminal
phalanges

Disappeared from observa-
tion.

Line of change still present.
With compasses at 2 cm.
everything called " two "
(1,099 days)

Reacted to induced current
July 2, 1902 (195 days).

Voluntary movement Aug.
13, 1902 (237 days).

Voluntary movement and
reaction to induced cur-
rent present Sept. 30,
1903 (282 days).

No loss of power or reaction
at any time.

When first seen by us, Jan.
13, 1904, muscles acted
shghtly and reacted to
induced current. Gradual
improvement took place.

Acted voluntarily and re-
acted to induced current
July 15, 1903 (299 days).

On Aug. 23, 1905 (924 days),
abductor and opponens
pollicis did not act volun-
tarily or react to induced
current.

Slight voluntary action and
feeble reaction to induced
current May 24, 1903 (373

days).

On Feb. 26, 1905 (369 days),
muscles reacted to inter-
rupted current.

On June 18, 1905 (481 days),
they reacted voluntarily.

STUDIES IN NEUROLOGY

by the median nerve have any obvious effect upon the rapidity of the return
of sensation. The most satisfactory and most uniform return took place
in Case 3, where the tendons were injm-ed and muscles paralysed. In another
instance (Case 5), the muscular branch was spared and no tendons were divided ;
but recovery occupied rather more than the average time. On Table I. are
three instances of secondary suture of the median nerve. But recovery of
sensation ran a course so different in the three cases, that the consideration
of the effect of secondary suture will be postponed, until we have analysed
the return of sensation after injury to the ulnar nerve.

(B) Ulnar Nerve. [Table II.]

We have been able to watch the recovery of sensation in four cases
where the ulnar nerve was divided at the wrist. In three, the wound healed

TABLE II.

(A) Total Nerve Trunk

Case.

Date of Injury.

Nature of Injury.

Operation and Result.

No. 14, J. S.

No. 16, A. P.

No. 17, J. M.

No. 18, W. W.

No. 19, L. C.
[FttZep. 207.]

June 26, 1903

No. 15, E. R. ... July 29, 1903

June 11, 1903

Aug. 26, 1904

July 16, 1902

Glass cut 6 cm. above fold of wTrist. Ten-
don of flexor carpi ulnaris and innermost
tendon of flexor sublimis divided. Nerve
completely divided (J. S.)

Glass cut 2-5 cm. above fold of wrist. Ten-
dons of flexor carpi ulnaris and ulnar
tendons of flexor sublimis divided. Nerve
completely divided (J. S.)

Primary suture, June
26, 1903. Healed by
healthy granulation

Primary suture, July 29,
1903. Considerable

suppuration. Healed
by granulation

Glass cut of wrist. All tendons divided Primary suture, .June 11,
except flexor carpi radialis and radial 1903. Wounds healed

tendons of flexor sublimis.
pletety divided (J. S.)

Nerve com-

by first intention

Glass cut of wrist. Flexor carpi ulnaris and j Tendon and nerve su-

ulnar nerve divided

tured, Aug. 26, 1904

Glass cut of elbow. Extensor communis ' Nerve sutured, Julv 31,

digitorum wounded. LTnar nerve divided

Injury to elbow-joint in childhood. Bony
outgrowths pressed upon nerve during his
work ; formation of fibroma of nerve

1902. Healed by first
intention

June 17, 1904. Resection
of 4-5 cm. of nerve at
elbow and suture of
divided ends (J. S. )

INJURY TO THE PERIPHERAL NERVES

without complication, and sensation first began to return on an average
in 109 days (92 days, 104 days, 131 days). The whole of the affected
parts had become sensitive to prick in from 16G to 181 days— an average
of 171 days.

Unfortunately, we are able to bring forward two cases only to determine
the date at which sensibility to Ught touch returns after uncomphcated
primary suture of the whole ulnar nerve. In one of these the period
was 166 days, in the other 172 days — an average of 169 days or 24
weeks.

In one instance only were we able to follow the patient to complete recovery.
Here the affected parts of the hand became sensitive to hght touch in 278 days
and the " line of change " had disappeared in 590 days ; at this date he gave
good answers to the compass test, even when the points were separated
to 1 cm. One other patient, who had been watched for a time and then

ULNAR NERVE

Return of SENSATioff.

Muscles.

Protopathic.

Epicritic.

Final Eesult.

Began Nov. 4, 1903 i

(131 days).
Complete Dec. 9, 1903

(167 days)

Began Dec. 16, 1903

(172 days).
Complete March 30,
1904 (278 days)

Line of change gone Feb. 5,
1905. Compasses perfect
at 1 cm. (590 days)

Reacted to indilced current
Oct. 30, 1904 (492 days).

Feb. 5, 1905, muscles acting
perfectly (590 days).

Began Dec. 2, 1903

(127 days).
Complete June 12, 1904

(320 days)

Began June 12, 1904

(320 days).
Complete Aug. 27, 1905

(760 days)

Line of change present
Aug. 27, 1905

June 12, 1904 (320 days), 1st
dorsal interosseous and
adductor poUicis acted
voluntarily. First dorsal
interosseous reacted to
strong induced current.

Began Sept. 23, 1903

(104 days).
Nearly complete when

he disappeared, Dec.

9, 1908 (181 days)

Recovery had not be-
gun Dec. 9, 1903, but
was complete when
he was next seen,
June 29, 1904 (383
days)

On August 3, 1904, line of
change still present, and
the compasses were badly
appreciated at 2 cm. (418
days)

All muscles reacted to in-
duced current June 29,
1904 (383 days).

Began Nov. 23, 1904

(92 days).
Complete Feb. 8, 1905

(166 days)

Began Feb. 8, 1904
(166 days)

... ... ... ...

No recovery of muscles.

Began Nov. 26, 1902

(117 days).
Complete Jan. 28, 1903

(180 days)

Began May 13, 1903

(287 days).
Complete Jan. 6, 1904

(525 days)

On June 18, 1905, line of
change gone; compasses
good at 2 cm., uniformly
wrong at 1 cm. (1,053
days)

July 3, 1904 (702 days), all
interossei acted and re-
acted to the interrupted
current. Muscles acted
voluntarily.

Began Sept. 14, 1904

(89 days).
Complete Aug. 16, 1905

(425 days)

STUDIES IN NEUROLOGY

disappeared, was rediscovered 383 days after the injury; at this time he
could appreciate light touch everywhere over the parts affected, but an
obvious hne of change was present and the compass test was defective
at 2 cm.

The ulnar nerve, in consequence of its exposed position at the elbow, is
subject to injuries at a point at least 25 cm. distant from the wrist. This
seems to make Uttle material difference to the length of time required for the
return of sensibiUty to prick. In No. 18, this form of sensation began to
return in 117 days, and the whole affected parts had become sensitive in 180
days. In No. 19, where a portion of the nerve had been excised at the elbow
and the ends reunited, sensation began to retm-n in 89 days, and in 425 days
had returned completely.

But injury at the elbow seems to cause a material delay in the final res-
titution of sensibiUty to Hght touch compared with the period required, when
the nerve has been wounded at the wrist. In No. 18 Hght touch was first
appreciated 287 days after the nerve had been sutured, and the whole area
affected did not become sensitive to cotton wool for 525 days. In this instance

TABLE II.—

(B) Dorsal Branch Intact

Case.

Date of Injury.

Nature of Injury.

Operation and Result.

No. 20, A. L. ...

No. 21, H. E.

No. 22, H. W.

No. 23, K. W.

No. 24, E. A.
[ Vide p. 209.]

Jan. 25. 1903

July 11, 1901

July 6, 1904

Between Aug.
26-31, 1901

March 7, 1902

Glass cut of wrist. Nerve divided

Primary suture, Jan.
26, 1903. Healed by
healthy granulation

Cut of wrist with a stoneware jar. Tendon Primary suture, July 11,
of flexor carpi ulnaris divided. Nerve 1901. Healed by first
completely divided (J. S.) intention

Glass cut of ■wrist. No tendons. Nerve I Primary suture, July 6,

divided below dorsal branch

1 904. Hea led by gran -
ulation

Glass cut of wrist. At operation for second- Secondary suture, Sept.
ary suture nerve was found completely j 24, 1901 (about 28

divided (H. H.)

Glass cut of wrist. At operation for second-
ary suture it was found that divided
nerve had been stitched to tendons
(J. S.)

days). Healed by first
intention

Secondarv suture, July
22, 1903 (502 days).
Healed by first inten-
tion

INJURY TO THE PERIPHERAL NERVES

the " line of change " did not disappear for nearly three years (1,053
days).

When the dorsal branch remains intact, it is usually difficult to determine
the date at which sensibiHty to prick begins to return. For the area of total
loss is mostly so small, and is at the same time so variable according to the
temperature of the hand and the general condition of the patient, that it is
sometimes impossible to say, if the obvious increase in sensibiUty is due to
recovery of the nerve or only to more favourable general conditions.

The date at which sensation to prick is completely restored can be deter-
mined more satisfactorily. The analgesia retreats to the terminal phalanx
of the Uttle finger, and it is easy to discover if this part is sensitive or not.
The average period necessary for complete recovery of sensation to prick was
133 days, but the individual variation is great, extending in our cases from
84 days^ to 192 days.

Division of the ulnar nerve below its dorsal branch causes loss of sensation
to light touch over a considerable area of the palm. In two instances of primary

ULNAR NERVE

Return of Sensation.

Protopathic.

Epicritic.

Final Result.

Muscles.

Had begun June 10,
1903 (135 days), and
was complete Aug. 5,
1903 (192 days)

Began Aug. 13, 1901

(33 days).
Complete Nov. 13, 1901

(125 days)

Had already begun on
Aug. 10, 1904 (35
days).

Complete Sept. 28, 1904
(84 days)

When seen by us there
was no loss of this
form of sensibiHty
(57 days)

Began Dec. 2, 1903

(133 days).
Complete Jan. 13, 1904

(176 days)

Began

Sept.
(234 days).
Complete March
1904 (424 days)

16, 1903 On June 8, 1904, line of

change still present.

23,' Compasses entirely

I wrong at 2 cm. (500 days)

Had not begun to re-
turn on Dec. 20, 1901

Began Nov. 16, 1904

(133 days).
Complete Feb. 8, 1905

(217 days)

Began Feb. 26, 1902

(154 days).
Complete Jupe 11, 1902

(258 days)

Began March 30, 1904

(252 days).
Complete Sept. 21, 1904

(426 days)

Died of malignant disease
of the liver, Dec. 23, 1901

June 21, 1905, compasses
perfect at 1-5 cm. ; badly
appreciated at 1 cm.

Dec. 7, 1904, line of change
present. Compasses at
2 cm. everything called
" two "

Aug. 16, 1905, line of
change present. Com-
passes perfect at 2 cm. ;
at 1-5 cm. everything
called " two " (755 days)

Acted voluntarily, and re-
acted to induced current
Dec. 9, 1903 (319 days).

On Nov. 13, 1901, no
muscles acted voluntarily
or reacted to induced
current.

Feb. 8, 1904 (217 days), 1st
dorsal interosseous re-
acted to induced cur-
rent, and showed the
first traces of voluntary
movement.

Nov. 7, 1902 (408 days), 1st
and 2nd dorsal interossei
acted voluntarily, and all
ulnar muscles reacted to
induced current,

July 27, 1904 (370 days),
1st dorsal interosseous
acted voluntarily. Ad-
ductor pollicis and ab-
ductor minimi digiti
reacted to induced car-
rent.

In a boy of 10 years of age.

STUDIES IN NEUROLOGY

suture of the nerve, this form of sensibility began to return in 234 and 133 days
(an average of 183 days). The whole affected hand had become sensitive
to Kght touch 424 and 217 days after suture.

In spite of the severity of the lesion and the great extent of the analgesia
it produces, sensibility to prick began to be restored to the affected palm in
two instances 74 and 128 days after primary suture, and the whole hand
became sensitive to prick in 140 and 295 days. One patient (No. 27) was
seen by us for the first time 245 days after primary suture, and by this time
all analgesia had disappeared.

Thus, although the material at our disposal is small, it is evident that the
length of time necessary for the restoration of sensibiUty to prick after division
of both nerves does not materially exceed that required after division of the
ulnar only. This result is particularly noteworthy, as in all the patients with

TABLE III.— DIVISION OF

Case.

Date of Injury.

Nature of Injury.

Operation and Kesult.

No. 25, A. H.

Dec. 24, 1902 [ Cut wrist with soda-water syphon. All Primary suture, Dec. 24,
structures divided down to the bone 1902. Suppurated
(J. S.)

No. 26, M. L.

Oct. 26, 1902

Cut wrist with jug. All structures divided
down to the bone

No. 27, A. W.

No. 28, G. B. ...
[Firfep. 214.]

Mar. 10, 1901 Glass cut of wrist. Both nerves divided

Sept. 24, 1902 Glass cut of wrist. Tendons were sutured,
but not nerves

Primary suture, Oct. 27,
1902. Suppurated

Primary suture at another
hospital. Suppurated

Secondary suture, April
17, 1903 (205 days).
Both nerves found di-
vided. First intention

INJURY TO THE PERIPHERAL NERVES

division of both nerves, from whom these numbers were drawn, the wound
suppurated.

As far as the return of sensibihty to prick is concerned, it seems to matter
little whether one or both nerves have been divided. But simultaneous
division of the two nerves materially delays the return of sensation to light
touch. On an average, in three instances, this form of sensibility did not
begin to return until 271 days, and was not universally restored to the affected
parts until 470 days, after suture. However, it must be remembered that in
all these patients the wound suppurated. But in spite of this objection,
we are inclined to believe that simultaneous division of both nerves materially
retards the return of sensibility to Ught touch.

(D) Summary

Our records are sadly incomplete, and it is not jDossible to determine, with
the accuracy we could wish, the period requisite for the various stages of

MEDIAN AND ULNAR NERVES

Return of Sensation.

Protopathic.

Epicritic.

Final Result.

Muscles.

Had begun Mar. 8, 1903

(74 days).
Complete May 13, 1903

(140 days)

Began Mar. 5, 1903

(128 days).
Complete Aug. 19, 1903

(295 days)

Nov. 10, 1901 (245
days), when first
seen by us. Proto-
pathic sensibility had
returned

Began Sept. 27, 1903

(163 days).
Complete Dec. 20, 1903

(247 days).

VOL. I.

Began July 12, 1903

(200 days).
Complete Sept. 23, 1903
(273 days)

Changed sensation had not
entirely disappeared July
8, 1905 (726 days). Com-
passes perfect at 2 cm.

Began Aug

(295 days).
Complete Dec. 2, 1903

(399 days)

19, 1903 i Line of change disappeared
I Feb. 17, 1904 (475 days).
Aug. 23, 1905, compasses
still bad at 2 cm.

Began Jan. 24,

(320 days).
Complete" Mar. 8,

(728 days)

1902

1903

Began April 10, 1904

(358 days).

Line of change gone May
24, 1903 (804 days).

With compasses at 3 cm.
everything called " two,"
Aug. 21, 1905

Sept. 23, 1903 (273 days),
interossei and abductor
pollicis acted voluntarily
and 1st dorsal interosse-
ous and abductor minimi
digiti reacted to the in-
terrupted current.

Sept. 2, 1903 (308 days),
opponens and abductor
pollicis reacted to strong
interrupted current. Feb.
17, 1904 (475 days), first
dorsal interosseous re-
acted to interrupted cur-
rent. July 13, 1904 (621
days), all muscles react-
ed to interrupted current.
Oct. 20, 1903 (356 days),
opponens and abductor
acted voluntarily.

Nov. 5, 1902 (605 days),
opponens and adductor
pollicis acting volun-
tarily ; did not react to
induced current. Mar.
8, 1903 (728 days), all
muscles acted voluntarily
and reacted to induced
current.

STUDIES IN NEUROLOGY

recovery. But it will be well, as far as possible, to summarise our results with
the warning that, since satisfactory cases are so few, the interjection of some
unrecognised circumstance, even in a single instance, may have materially
upset any of the following averages : —

Protopathic.

Epiceitic.

Began.

Complete.

Began. Complete.

Ulnar with dorsal branch intact

133

183

320

Complete ulnar nerve

109

171

169

278

Median nerve

190

262

387

Median and ulnar nerves

101

217

271

470

From this table it will be seen that the earliest recovery of sensibility to
prick occurs after primary suture of the median nerve. For reasons given
above, we have purposely neglected the date at which the restoration of
sensation began in those cases where the ulnar nerve was di\dded but the
dorsal branch remained intact. It is after such an injury that the analgesia
disappears completely with the greatest rapidity. Even when both nerves
had been divided, sensibility to prick was restored in 217 days, or a little over
six months.

The length of time necessary for complete recovery of sensibility to cotton
wool and to the intermediate degrees of temperature varied somewhat, but
occupied about a year in most cases. Any defect in healing, particularly
if it leads to the formation of pus, or of fibrous tissue around the nerve,
materially hinders the return of the higher forms of sensation.

CHAPTER III

RECOVERY OF SENSATION AFTER INCOMPLETE DIVISION OF THE

NERVES OF THE HAND

If a nerve has been bruised, or incompletely divided, it may become entirely
incapable of conducting impulses, and the loss of sensation at first may resemble
that which follows complete division. But, when the continuity of the nerve
has not been destroyed, recovery may take place, not only more rapidly, but
also in an entirely different manner from that observed after complete division.
At the end of a period varying with the severity of the injury, sensation to
prick begins to return. Approximately at the same time, light touch also
begins to be appreciated over those parts of the area previously insensitive
to this stimulus, which lie nearest to the wrist.

Thus, if a nerve is injured, but not divided, both sensibility to prick and to
light touch begin to return together, in contradistinction to the order in which
sensation is restored when the continuity of the nerve has been completely
destroyed.

As recovery progresses, the two forms of sensibility continue to advance
fari passu. For instance, if the median nerve has been injured, the gradual
diminution of the analgesia on the fingers is accompanied by an equivalent
increase in the sensibility of the palm of the hand to light touch.

With the power to aj)preciate light touch, the affected parts become sensi-
tive to intermediate degrees of temperature. In fact, restoration of this form
of sensibility over the proximal parts of the palm, at a time when the analgesia
has scarcely begun to diminish in extent, is one of the earliest indications that
the nerve has not been comj)letely divided.

With the return of sensation to fight touch and to the intermediate degrees
of temperature, comes a coincident imj)rovement in the answers given by the
patient to the compass test. The power of discriminating two points is not
only restored more rapidly, but more often returns completely than when the
continuity of the nerve has been destroyed.

With regard to the principle underlying the manner in which sensation is
restored, it matters little whether the nerve has been bruised or incised. We
have, therefore, gathered together all the instances of injury and incomplete
division on the same table.

But these partial injuries may produce very varying results. Sometimes
every function of the nerve is destroyed for a time ; sensation is lost and the

100

STUDIES IN NEUROLOGY

muscles are paralysed, exactly as if the nerve had been divided. This occurs
most frequently when the injury is an incised wound ; but it can also occur from
the pressure of sphnts and bandages, or even, as in the following instance, from
a blow over the uhiar nerve at the elbow.

Case 36. — Injury to the ulnar nerve at the elbow to illustrate the simultaneous return of the two
forms of cutaneous sensibility.

C. T. S., aged 27, was kicked on the inner side of the elbow whilst playing football on
February 27, 1904. The ulnar half of the hand became numb and painful, but he was able to
contmue the game. When seen by one of us on the 29 th, the trunk of the ulnar nerve was
exquisitely tender, and he had lost sensation to cotton wool over the area in fig. 10. Sensation

Incomplete' Division of the Median Nerve

TABLE IV.

Case.

Date of Injury.

Nature of Injury.

Operation and Eesiilt.

No. 29, C. B.
[FicZep. 203.]

Sept. 20, 1902

No. 30, D. B.

Nc. 3L H. B.

Cut wrist with glass bottle. Median nerve Wound explored Sept. 20.
found swollen and redder than normal; ■ Nerve left untouched,
on ulnar side it had been cut into. Ten- { Tendon sutured. First
don of flexor sublimis to index had been intention
divided (J. S.)

July 31, 1904 Glass cut of wrist. Median nerve incom- Tendons and nerve su-
pletely divided. Four tendons of flexor tured Aug. 1, 1904.
sublimis divided Healed by healthy

granulation

Dec. 18, 1904

No. 32, A. S.

April 22, 1905

Glass cut of wrist,
pletely divided

Median nerve incom-

Glass cut of wrist. Median nerve cut into
on ulnar side. Some tendons of flexor
sublimis divided

On Dec. 18, 1904, wound
stitched without an
anaesthetic. On June
15, 1905, explored and
nerve examined (J. S.)

Wound in nerve sutured
and tendons reunited,
April 22, 1905. First
intention

Injury to Median Nerve without Di\'ision

Case.

Date of Injury.

Nature of Injury.

Eesult of Injury.

No. 33, H. E. T. Dec. 26, 1903 Fractured forearm. SpUnt pressure. Volk- Complete loss of function

mann's contracture in median nerve

INJURY TO THE PERIPHERAL NERVES

101

to prick was lost over a considerable part of the ulnar palm, and over the i^alniar aspect of the little
and part of the ring fingers. Over the same parts, he was completely insensitive to water at
55° C, and to ice. That part of the back of the hand supplied by the dorsal branch of the nerve
was not affected. On March 2, four days after the accident, we were able to examine him in
greater detail. The appearance of the hand was unaltered, but sensation was profoundly affected.
Prick, water at 55° C, and ice, were not ajipreciated over the palmar surface of the little finger.
Two-thirds of the ring finger and part of the ulnar palm were insensitive to cotton wool and
the intermediate degrees of temperature.

He could perform all the movements of the hand, but abduction of the little finger was weak,
and it tended to assume the position usually seen in ulnar paralysis. The interossei also acted
feebly. All the muscles reacted to the interrupted current; to galvanism they had become
over-sensitive, reacting briskly with a current of 3 mA., and A.C.C. was considerably in excess

MEDIAN NERVE

Retukn of SENSATIO^r.

Muscles.

Protopathic.

Epicritic.

Final Result.

Began Oct. 22, 1902

Patient could not bo found

Did not cease to act volun-

(32 days).

after July 12, 1903

tarilv. Did not react to

Complete Julv 12, 1903

Nearly complete July

interrupted current be-

(294 days)

12, 1903 (294 days)

tween Oct. 22, 1902, and
Feb. 11, 1903 (143 days).
To galvanism reactions
were practically normal
throughout.

Began Sept. 7, 1904

Line of change well marked

Sept. 7, 1904 (37 days).

(37 days).

Aug. 16, 1905. Com-

abductor and opponens

Complete Dec. 14, 1904

passes good at 1-5 cm.

acted voluntarily, but

(135 days)

(380 days)

did not react to the
interrupted current until
Oct. 26, 1904 (85 days).
To galvanism reactions
were practically normal
throughout.

Began Mar. 1, 1905

Began Mar. 22, 1905

Mar. 1, 1905, muscles acted

(73 days).

(94 days).

voluntarily and reacted

Almost completely re-

Almost completeh' re-

to interrupted current (73

turned Aug. 16, 1905 i turned Aug. 16, 1905

days).

(168 days)

Began May 31, 1905

Began Aug. 30, 1905

May 31. 1905 (38 days),

(38 days).

(129 days)

reacted to interrupted

Complete Aug. 30, 1905

currents. July 14, 1905

(129 days)

(82 days), acted volun-

tarily.

Protopathic.

Epicritic.

Final Result.

Muscles.

Began July 3, 1904

(188 days).
Complete Feb. 26, 1905

(425 days)

Began July 3, 1904 | Compasses perfect at 1-5 July 24, 1904 (208 days),
(188 days). cm. Aug. 27, 1905 (606 muscles reacted to in-
Complete May 6, 1905 j days) terrupted current.
(493 days) |

102

STUDIES IN NEUROLOGY

of K.C.C. This increase of susceptibility wtxs best marked in the abductor muscles of the little
and index fingers. Compared with the reaction of similar muscles of the sound hand, the increase
was obvious and the polar reversal striking.

Sensation continued to return with rapidity ; the area of loss to prick and that of loss to light
touch retreated step by step. On March 9, the only loss of sensation that could be discovered
occupied the skin over the palmar surface of the terminal phalanx of the little finger. One week
later, this had completely disappeared.

To show the loss of sensation produced in Case 36 by a blow over the ulnar nerve at the elbow.
The area insensitive to cotton wool and to the intermediate degrees of heat and cold is surrounded
by a single line. The area of total cutaneous insensibility is marked in black. A shows the condition
on February 29, B on March 2, C on March 9.

Sometimes the injm'y is not sufficiently severe to produce complete
analgesia of any part of the area supplied by the nerve affected. But sensi-

TABLE v.—

Incomplete Division of the Ulnar Nerve

Case.

Date of Injury.

Nature of Injury.

Operation and Result.

No. 34, C. T. ...
[ Vide p. 209.]

No. 35, F. H. ...

Mar. 4, 1903
Jan. 21, 1904

Glass cut of wrist. Flexor carpi ulnaris
and ulnar artery divided. Ulnar nerve
almost completely divided below dorsal
branch

Wrist cut with knife. Trunk of ulnar nerve
cut into on ulnar aspect above oriqin of
dorsal branch. No tendons divided (J. S.)

Mar. 4, 1903. First in-
tention

Jan. 28, 1904, injured
nerve sutured with cat-
gut. First intention

INJURY TO THE PERIPHERAL NERVES

103

bility to light touch and to the minor degrees of temperature may be aboKshed
over the full extent of the injured nerve. More commonly, stimulation with
cotton wool cannot be appreciated, and the compasses show profound lowering
of sensibility, although intermediate degrees of temperature can still be appre-
ciated over the area of the injured nerve. Under such circumstances, sensation
will be restored with remarkable rapidity.

Case 35. — Incised ivound of the ulnar nerve producing partial loss of sensation.

On January 21, 1904, F. H., aged 15, cut his left forearm with a pocket knife. It bled httle,
and he did not visit a medical man imtil three days later. When first seen by us on January 28
there was an oblique wound about half an inch in length, which was
healing by granulation. It was situated one and a half inches above
the head of the ulna at the extreme border of the forearm. The
hand was held with the fingers over-extended at the metacarpo
phalangeal joints and flexed at the interphalangeal, these changes
being most marked in the little and ring fingers. The little finger
was abducted, and the hand had assumed the typical position seen
after division of the ulnar nerve. True adduction of the thumb was
impossible, and none of the interossei were acting.

Sensation to cotton wool was lost over the area in fig. 11, but
minor degrees of temperature could be appreciated. Sensation to
prick was unaffected.

The wound was explored the same day and the ulnar nerve
exposed. It was injured just above where the dorsal branch was given off, being severed for
about two-thirds of its breadth. On February 10, light touches were perceived everywhere, but
were less distinct over the area affected than elsewhere, and by April 20 no difference could be
found between the sensibiHty of the two hands.

In conclusion, we have found that injury to a peripheral nerve may produce
all the results, both sensory and motor, which follow its complete division.

Fig. 11.

From Case 35, to show the
area rendered insensitive to
light touch by an incised
wound of the ulnar nerve.

ULNAR NERVE

Return of Sensation.

Protopathic.

Epicritic.

Final Result.

Muscles.

Almost returned June
17, 1903 (104 days).

Completely returned
Aug. 26, 1903 (174
days)

No loss

Began June 17, 1903

(104 days).
Complete Aug. 26, 1903

(174 days)

Light touch only lost.
40° C. and 22° C. ap-
preciated from date
of injury.

Complete return Mar.
16, 1904 (56 days)

Sensation to fight touch
again became lost with
the cold weather and did
not clear finally until
Feb. 26, 1904 (358 days).

Line of change still present
May 6, 1905 (793 days)

No line of change. All
forms (including com-
passes) perfect April 20,
1904 (90 days)

Acted voluntarily June 17,
1903 (104 days). All re-
acted to interrupted cur-
rent Aug. 26, 1903 (174
days).

Acted voluntarilv Sept.
14, 1904 (236 days). Re-
acted to interrupted cur-
rent Nov. 2, 1904 (284
days). Reacted briskly
to galvanism from be-
ginning.

104 STUDIES IN NEUROLOGY

Injury to Ulnae, Nerve without Division.

Case.

Date of Injury.

Nature of Injury.

Result of Injury.

No. 36, C. T. S. i Feb. 27, 1904 Kick over internal condyle of humerus

No. 37, E. H... May, 1904

No. 38, T. F. ...

Sept. 10, 1904

Loss of both forms of
sensation over distribu-
tion of uhiar, except-
ing its dorsal branch

.. Struck inner side of elbow on a stone step Loss of epicritic sensi-
bility over full ulnar
area

Separated lower epiphysis of humerus. Bad Loss of epicritic sensi-
union. Oct. 28 set afresh. Forearm ban- bility over full ulnar
daged in full flexion area

TABLE VI. -INJURY TO MEDIAN AND

Case.

Date of Injury.

Nature of Injury.

Result of Injury.

No. 39, W. E.

April 30, 1904

No. 40, A. S.

April 10, 1903

No. 41, E. P.

July 26, 1902

Compound fracture of humerus. IMedian
nerve exposed in wound. Splint pressure
on forearm. Splints removed during third
week in June, 1904

Fracture of radius. Splint
appeared on fourth day.
six weeks

pressure. Sore
Arm in splints

Injury to arm. Splints fourteen days.
Blisters seen seven days after injury

Complete loss of function
in median and ulnar

nerves

Volkmann's contracture.
Complete loss of func-
tion of ulnar nerve in
the hand ; incomplete
median

Complete loss of function
in median and ulnar,
excepting its dorsal
branch

But the two forms of sensation may begin to return approximately at the
same time, and be restored 2^ari 2)assu. This method of restoration of function
differs fundamentally from that observed when the nerve has been reunited
after complete division.

INJURY TO THE PERIPHERAL NERVES

105

Return of Sensation.

Muscles.

Protopathic.

Epicritic.

Final Result.

Becran Mar. 2, 1904

Beo;an Mar. 2, 1904

Perfect Mar. 12, 1904 ...

No movement absolutely

(3 days).
Complete Mar. 12, 1904
(13 days)

lost, but abduction of
little finger was poorly
performed. Reaction to
interrupted current never
lost. Increased irritabil-
ity to galvanism.

No loss

Began Aug. 24, 1904.

Perfect Nov. 23, 1904

No paralysis. Wasting of

Complete Sept. 28, 1904

(about 181 days)

all interossei. Reaction
to interrupted current
normal.

No loss...

Had returned by Jan. 4,
1905 (67 days)

Line of change present July
14, 1905 (257 days).

Compasses perfect at 1-5
cm.

No paralysis.

ULNAR NERVES WITHOUT DIVISION

Return of Sensation.

Protopathic.

Epicritic.

Final Result.

Muscles.

Already begun Nov. 2,
1904 (185 days).

Complete Dec. 21, 1904
(233 days)

Returned completely
Sept. 30, 1903 (172
days)

Sensation had not be-
gun to return Sept.
17, 1902 (37 days).

Returned completely
Nov. 14, 1902 (94
days)

Began Dec. 7, 1904

(219 days).
Complete April 5, 1905
(337 days)

Returned
Jan. (3,
days)

completely
1904 (269

Sensation had not be-
gun to return Sept.
17, 1902 (37 days).

Had almost completely
returned Nov. 14,
1902 (94 days)

Compasses perfect at 1 cm.
April 5, 1905 (337 days)

Feb. 8, 1905 (301 days),
sensation perfect. No
line of change

Compasses at 1 cm. perfect
Fob. 18, 1903 (189 days)

Feb. 1, 1905 (274 days), first
dorsal interosseous and
abductor minimi digiti
acted voluntarilv.

April 5, 1905 (337 days), all
muscles acted and reacted
to interrupted current.

Paralysis of all intrinsic
muscles of hand. No
reaction to interrupted
current. Brisk reaction
to galvanism.

July 6, 1904 (453 days), all
muscles reacted to inter-
rupted current.

Paralysis of all intrinsic
muscles of hand. No
reaction to interrupted
current.

Feb. 18, 1903 (189 days), all
muscles acted well and
reacted to interrupted
current.

Injury to a nerve not sufficiently severe to produce analgesia may cause
complete loss of sensibility to light touch, and to intermediate degrees of heat
and cold. Or sensation to cotton wool only may be lost, while all forms of
temperature can be appreciated over the affected area.

CHAPTER IV

NERV^E SUPPLY OF THE FOREARM

Without the knowledge gained from lesions of the median and ulnar nerves,
it would be impossible to unravel the complexities of the sensory nerve supply
to the forearm. An attempt will be made in this chapter as far as possible
to analyse the part played by each of the main nerve trunks. Nowhere is their
distribution, as revealed by anatomy, less in accord with their functional
supply than on the forearm ; for the considerable anastomoses of both larger
and smaller branches make it impossible to deUmit by dissection then- ultimate
distribution. Moreover, anatomy can demonstrate only, that the branches
of one or more nerve trunks run to certain parts, without determining the form
of sensibility they mainly subserve. A part suppUed by fibres from two main
nerves is, to the anatomist, an area of overlapping sensibilit3^ But, from the
physiological aspect, the problem of nerve supply is less simple. On the palm
of the hand, as far as the higher forms of sensation are concerned, the over-
lappmg of the median and ulnar nerves is trivial ; but we have shown that the
mechanism by which the palm is rendered sensitive to prick and to the more
extreme forms of temperature overlaps, to a degree scarcely suspected by
most anatomists.

But there are other difficulties in determining the ultimate destination of
a nerve, besides the wide diversity in distribution of these two forms of
sensibihty. Division of a nerve produces loss of sensation over those parts
to which that nerve alone is distributed. Only by stimulation of the trunk
of a nerve, or by widespread destruction of surrounding nerves, can the full
extent of the parts it supplies become manifest. Now, true hyperalgesia,
which gives the full distribution of the sensibihty to pain conducted by any
nerve trunk, is so rare that it can seldom be utiUsed for this determination ;
excessive sensibility to the higher forms of sensation does not exist as a
consequence of injury to peripheral nerves.

Almost in every case, we shall first determine the extent of the loss of
sensation produced by dividing each of the nerves of the forearm. By this
means we can discover how much of the forearm is supplied exclusively from
any particular nerve. This wdll be spoken of as its " exclusive " supply.

But, in order to determine the full distribution of any single nerve, it
becomes necessary to seek for cases where that nerve has remained uninjured,
although the branches supplying adjacent areas have been completely divided.

106

INJURY TO THE PERIPHERAL NERVES

107

Any sensibility that remains must then be clue to the uninjured nerve. This
will be called the method of " residual sensibility."

In a few instances, we have seen true hyperalgesia produced by irritation
of the trunk of a nerve. From them we have been able to determine directly
the full extent of the area supplied from that particular branch with sensibihty
to prick.

§ 1, — The Post-axial Half of the Forearm

The internal cutaneous (n. cutaneus antibrachii mediaUs) takes its origin
from the inner cord of the brachial plexus in close association with the ulnar
nerve. Excej)ting for anastomoses with the lesser internal cutaneous above,

Fig. 12.

To show the loss of sensation produced in Case 42 by excision of a portion of the ulnar and internal
cutaneous nerves in the lower third of the arm. The area insensitive to light touch and to intermediate
degrees of heat and cold is enclosed in a single line. Total cutaneous insensibility is showm in black.
Above the elbow the loss could not be determined with certainty in conseq[uence of the position of
the wound.

and with the ulnar over the front and back of the hand, this nerve supplies
an isolated area on the post-axial half of the forearm. In the following case,
excision of nearly three inches of the internal cutaneous nerve high in the arm
discovered to us in full the extent and nature of its exclusive supply.

Case 42. — Excision of a jMrtion of the internal cutaneous after previous resection of the ulnar.

Edgar T., aged 57, came under the care of Mr. Jonathan Hutchinson, at the London
Hospital, suffering from loss of power and disturbance of sensibility in the hand. On the inner
side of the arm, in its lower third, a hard tumour could be felt, apparently in connection with
the ulnar nerve.

The hand was lield in the position characteristic of ulnar paralysis ; the two terminal joints
of the little finger were flexed, the metacarpo-phalangeal joint over-extended. The interosseous
spaces were wasted and all the muscles of the hand supplied by the ulnar nerve were paralysed.
Sensation to light touch, to water at 20° C. and at 40° C, were lost over the full ulnar area on
the palm and dorsal surface of the hand. On the dorsal surface, the lo.ss to prick, to heat and to
cold, corresponded in extent with that to light touch ; on the palm, the little finger, and a narrow
strip on the extreme ulnar border were alone insensitive to all cutaneous stimuli.

108 STUDIES IN NEUROLOGY

On October 26, 1904, Mr. Hutchinson cut down uison the swelling in the arm. The uhaar
nerve was traced into it from above, and the internal cutaneous lay across its surface. He,
therefore, removed the whole tumour together with about three inches of both nerves. After
the operation, the loss of sensation had extended greatly. The skin of the post-axial half of
the forearm was insensitive both in front and behind up to a line rumimg through the centre of
the wrist. Both these borders were continuous, on the front and back of the hand, with the
limits of loss to light touch that existed before the operation. In fact, the border of the final
anaesthesia closely corresponded on the flexor surface to a line drawn from the tendon of the
biceiJS to the axis of the ring finger, and from the olecranon to the axis of the same finger on
the back of the forearm. The borders of loss to prick and all degrees of heat and cold in the
forearm coincided exactly with these limits, but fell away both in front and behind in the
neighbourhood of the wrist {vide fig. 12).

In order to obtain so extensive an area as that we have just described, it
is necessary that the nerve shall be completely di\aded above the lower third
of the arm. Anywhere below the elbow, an injury usually destroys one only
of its two branches, producing loss of sensation to hght touch and minor degrees
of temperature over either the front or the back of the post -axial sm-face of
the forearm, but no absolute loss of sensibility to prick, heat and cold. If
the anterior branch is di^dded, the loss ^^ill be Umited by a sharp border on the
flexor surface, but will gradually merge into the normal parts over the back
of the forearm by a band of diminished sensibihty. Di\dsion of the posterior
branch will cause an area of anaesthesia on the back of the forearm strictly
Hmited towards the radial side, but fading gradually on the ulnar border into
parts of normal sensibihty. Thus, the internal cutaneous nerve suppUes the
skin of the post -axial half of the forearm with both forms of sensibihty. Its
two branches overlap considerably. One supphes the whole of this post-axial
area on the front (flexor aspect) of the forearm, the other its dorsal (extensor)
aspect. The indeterminate borders of these two areas of anaesthesia, where
they come into contact, show that the two branches overlap even for the
conduction of sensation of hght touch. For sensation of pain the overlapping
must be extreme, since little or no analgesia is produced by dividing one
branch only.

It is rarely possible to mark out the full supply of any nerve in the forearm
by means of the hyperalgesia produced by irritation of its trunk. But in
Case 84,1 where a bullet passed through the forearm from the radial to the
ulnar aspect, the whole extent of the area supphed with sensibihty to pain
from the internal cutaneous was intensely tender. A comparison of fig. 41
on p. 213 with that of the area obtained when the internal cutaneous was
divided (fig. 12) shows the different results produced by the two methods.

§ 2. — The Pee-axial half of the Foreaem

The sensory innervation of the f)ost-axial half of the forearm and hand is
comparatively simple ; it is carried out almost entirely through the internal

1 Vide p. 212.

INJURY TO THE PERIPHERAL NERVES 109

cutaneous and ulnar nerves. The conditions on the pre-axial half are more
complex. The musculo -cutaneous, the radial and the median, are all in some
degree responsible for its innervation, and to these nerves on the back
(extensor surface) of the forearm is added the lower external cutaneous branch
of the musculo -spiral. The sensibihty of the post-axial half of the forearm
and hand depends on two nerves only, whilst at least four enter into the supply
of the skin on the pre-axial half.

Not one of these nerve branches supplies in the forearm a self-contained
area analogous to that of the internal cutaneous. Division of any one of them
causes at most an area of loss of sensation to light touch, usually with ill-
defined borders. Sensibihty to prick is affected to an even less degree.

Radial. — (Ramus superficialis nervi radiahs). After the musculo-spiral
(nervi radiahs) has given off its three cutaneous branches and has supplied the
extensor muscles, it divides into the posterior interosseous (ramus profundus
nervi radialis), and the radial (ramus superficiaUs nervi radiahs) nerves. In all
works on anatomy, a certain portion of the sldn over the dorsal surface of the
tliumb and over the back of the hand is assigned to the latter branch. But
the anastomoses between the various nerves supplying the pre-axial border of
the forearm and hand are so free that it is impossible to determine by dissection
their ultimate distribution ; the area assigned to any one nerve in the books
on anatomy, when not fanciful, is nothing but the measure of the skill of
generations of chssectors. An area of tenderness due to irritation of the trunk
of the nerve can reveal the full extent of its distribution ; its division will show
only how far its exclusive suj)ply extends.

Nowhere is this more apparent than in the description given of the supply
of the radial nerve ; for it has long been known that division of the musculo-
spiral in the neighbourhood of the spiral groove usualty causes no definite loss
of sensation over the thumb or back of the hand. The following case adds
another to the long list scattered among the literature of the last half century
(Case 43). 1

Frank L. was admitted to Poplar HosjDital on June 28, 1903, with a fracture
of the lower end of the right humerus. Two days later, as all attempts to
reduce the deformity had failed, operation was resorted to. After the opera-
tion, paralysis of all the muscles supplied by the musculo-spiral nerve appeared,
but nowhere was there any loss of sensation. On August 3, 1903, one of us
cut down upon the site of the previous incision, and found the musculo-spiral
nerve had been divided ; the two parts were adherent to the bone, and sur-
rounded by fibrous tissue which united the retracted ends. These were excised
together with the intervening fibrous tissue, and the nerve was reunited Avith
silk sutures. A portion of the supinator longus was sewn beneath the nerve
to prevent it from again forming adhesions to the bone. All the muscles on
the extensor aspect of the forearm, including the supinator longus, were
paralysed, and did not react to the interrupted current, and yet at no time

1 Vide p. 215.

110

STUDIES IN NEUROLOGY

was there any demonstrable loss of sensation to light touch, to prick, to heat,
or to cold.

Although division of the parent trunk produces no change in sensation,
destruction of the radial nerve in the lower third of the forearm causes definite
loss over the back of the thumb and outer part of the thenar eminence. But
this loss is confined to the higher forms of sensation. Stimulation with cotton
wool or with a temperature of 40° C. is not appreciated ; a prick, ice, or water
at 50° C, evoke an immediate response.

In Lena LeB. (Case 44 ^) the radial nerve was divided for therapeutic reasons
at the point where it passes under the tendon of the supinator longus. This
abolished sensation to light touch, and to minor degrees of heat and cold, over

the back of the thumb and dorsal aspect
of the first metacarpal bone. The
boundary of this anaesthetic area (fig.
13) was firmly defined on its palmar
aspect ; there was no gradual transition
from parts insensitive to light touch to
those of normal sensibiUty. It followed
a Une of great theoretical interest run-
ning from the radial corner of the
thumb-nail along the lateral aspect of
the thumb to the metacarpo -phalangeal
joint. From this point it swung inwards
towards the thenar eminence, including
a considerable portion of the sldn that
lay over the abductor and opponens
pollicis. On the ulnar aspect of the
thumb, this anaesthetic area was also
bounded by a firm Une ; but, over the
dorsal surface of the metacarpal, the
loss of sensation merged gradually
towards the back of the hand into parts of normal sensibiUty.

Until the radial nerve reaches the wrist, the fibres of which it is composed
innervate exclusively no part of the hand. On the peripheral side of that
point, it alone supplies the higher forms of sensibiUty to an area on the back
of the thumb and to a small strip of skin on the outer side of the thenar
eminence. No loss of sensation to pain, or to the more extreme degrees of
temperatm-e, can be produced by destruction of this nerve in any part of its
course.

External cutaneous (N. cutaneus antibrachii lateraUs seu cutaneus brachii
externus). — We have seen no case where the whole external cutaneous alone was
divided. But in the following instance, part of the distribution of this nerve was
exquisitely marked out by tenderness, due to irritation of its anterior branch.

1 Vide p. 215.

Fig. 13.

To show the area that became insensitive to
light touch and minor degrees of heat and cold
in Case 44, after division of the radial nerve
(ramus super ficia lis nervi radialis). For a com-
plete series of diagrams, and for a full account
of this case, vide p. 215.

INJURY TO THE PERIPHERAL NERVES

111

Case 4t5.— Hyperalgesia over an area on the forearm produced by injury of the anterior division
of the external cutaneous nerve.

Leonard E. first came under our notice in February, 1905, with a history that, fourteen weeks
before, he had slipped with a jug in his hand and cut the front of his forearm. The wound was
sewn up at once, but two weeks later it was reopened because the patient had begun to suffer
pain. This pain slowly increased, and for about three weeks before we saw him had troubled
him greatly.

About two and a half inches (6-5 cm.) above the fold of the wrist, on the anterior (flexor)
surface of the forearm, was an almost transverse scar, three-quarters of an inch (2 cm.) in length.
On the radial side was a second smaller scar, three-eighths of an inch (1 cm.) in length, which
looked as if it might have resulted from an incision. Extending from the region of these scars
in the direction of the hand, a considerable area was
profoundly tender to a point dragged lightly across the
skin, and to pressure with any blunt object, such as the
head of a pin. To light touch, to prick, to heat, and to
cold, sensation was perfect, and with the compasses an
-equivalent record was obtained on both the sound and
affected limbs.

As the patch of hyperalgesia was obviously due to
some injury to the anterior branch of the external
cutaneous, the nerve was explored by one of us. It
was found to be adherent to the scar and involved in
fibrous tissue. A small portion was excised and the
two ends sutured together. All pain ceased immech-
ately. But the operation was followed by no diminution
in any form of sensation over any part of the area
supplied by the divided nerve.

Fig. 14.

The area which became insensitive to
light touch and minor degrees of heat and
cold after division of the posterior branch
of the external cutaneous [Case 44] is
enclosed by a thin line, that insensitive to
prick and to all degrees of temperature by
a thick black line. The radial (ramus
superficialis nervi radialis) had been pre-
viously divided, and the result is shown
on fig. 13. For a full account of this case
vide p. 215.

But, if the radial be divided in addition
even to one branch of the external cutaneous,
the loss of sensation becomes considerable.
We have no instance where the anterior
branch was affected together with the radial,
but Case 44 showed the effect produced by
dividing the posterior division of the external
cutaneous after destruction of the radial.
At the time when we undertook to make
the painful spot on her thumb insensitive, our knowledge of the distribu-
tion of these nerves to the radial half of the back of the hand was less
complete than at present. Anxious to cause as little injury as possible, we
proceeded to denervate the part by degrees, and thus at one period we had the
opportunity of examining, in an uncomplicated form, the loss of sensation
produced by destruction of the radial and posterior division of the external
cutaneous. The anaesthesia that followed division of the radial nerve has
already been described^ and appears on fig. 13. Subsequent destruction of the
posterior division of the external cutaneous produced an extension of this
loss of hght touch, which now occupied the back of the hand over the first
interosseous space and region of the knuckle of the index finger (fig. 14).

112

STUDIES IN NEUROLOGY

Di\T.sion of the radial nerve alone had produced no loss of sensibility to
prick, but subsequent destruction of the posterior branch of the external
cutaneous caused a loss of sensation to prick even more extensive than the
loss to cotton wool. Over a patch on the back of the hand, stimulation -with
cotton wool was appreciated, but all sensibiUty to prick was lost.

If, in addition to the radial, both branches of the external cutaneous are
divided, the loss of sensation both to Hght touch and to prick occupies almost
the whole of the pre-axial border of the forearm and back of the hand.

This was well seen in the case of one of us (No. 46) after the radial (ramus
superficialis nervi radiahs) and external cutaneous had been divided, for experi-
mental purposes, in the neighbourhood of the bend of the elbow. A full account

Fig. 15.

To show the loss of cutaneous sensibility produced by dividing the radial (ramus superficialis nervi
radialis) and external cutaneous nerves in the neighbourhood of the elbow. The thick line bounds the
area insensitive to prick. The thinner line encloses the parts insensitive to cotton wool. Both the
thick and the thin line are dotted wherever the borders of the area of loss of sensibility were not
sharply defined.

The triangle marked A was insensitive to prick but sensitive to stimulation with cotton wool.

of this experiment forms the subject of a subsequent section, but fig. 15 will
be sufficient to show the extent of the anaesthesia and analgesia produced by
di^dding these two nerves. The anterior border on the flexor surface of the
forearm corresponded exactly with the axis of the limb to all forms of cutaneous
stimulation. On the extensor aspect the loss of sensation was less definite ;
the loss of sensation to prick and that to light touch did not exactly coincide ;
both were bomided by a sinuous border. On the back of the hand, both
forms of loss of sensation were co-terminous except over the outer side of the
thenar eminence and both the lateral aspects of the thumb.

An exactly similar loss over the lower third of the forearm and over the
back of the hand was produced by a circular wound around the radial half
of the forearm (Case 47, p. 113). Both these instances prove that the back
of the hand and the greater part of the back of the thumb are suppHed
exclusively by the radial and external cutaneous. The flexor aspect of

INJURY TO THE PERIPHERAL NERVES

113

the pre-axial half of the forearm is innervated entirely by the external
cutaneous, and destruction of both branches of this nerve brings out a line
corresponding to the axis of the limb. But the extensor aspect receives its
supply also from the lower external cutaneous branch of the musculo-spiral,
and the full extent of skin innervated by this nerve is beautifully shown on
fig. 15. For here every nerve to the pre-axial half of the forearm, with the
exception of this branch of the musculo-spiral, had been divided; any sensa-
tion that still remained must have travelled by means of this nerve. We
know, therefore, that it suppUes sensation as low as the wrist, and that the area
of its supply merges with, and overlaps, that of the external cutaneous and
radial. It is a remarkable fact, that, in both Case 46 and Case 47, the cutane-
ous branch of the musculo-spiral seemed to be incapable of endowing as large

Fig. 16.

From Case 47 to show the area of loss of sensation produced by the accidental division of the
radial (ramus superficialis nervi radialis) and external cutaneous nerves. The jagged scar is represented
running across the flexor surface of the forearm. The area insensitive to light touch is enclosed by
a thin line, that insensitive to all cutaneous stimulation by a heavy black line (vide p. 217).

an area on the. back of the wrist with sensibility to prick as with sensibility
to light touch ; in consequence, a small area was present, especially evident
on fig. 15, where the patient was sensitive to light touch, but insensitive to
prick, heat and cold.

Before passing away from the pre-axial border of the forearm, it will be
well to consider the distribution of the median nerve in the light of the know-
ledge we have gained of the radial and external cutaneous. For, by division
of these two nerves, all collateral supply to the back of the middle and index
fingers and to the outer part of the thenar eminence is entirely cut off.

The border of the loss of light touch runs for a short distance down the axis
of the middle finger (fig. 15 and fig. 16) ; at a point about half-way down the
basal phalanx it turns sharply towards the radial side, to drop into the cleft
between the middle and index fingers. Thence it rises again, to enclose about

VOL. I. I

114 STUDIES IN NEUROLOGY

one-half of the skin over the dorsal surface of the basal phalanx of the index
finger. It then passes across the first dorsal interosseous space, close to the
free edge, to reach the lateral aspect of the thumb near the base of the first
phalanx. On the ulnar aspect of the thumb, the border of the anaesthetic
area runs almost in a straight line to the edge of the thumb-nail. On the radial
aspect of the thumb and outer aspect of the thenar eminence, the boundary
of loss of light touch corresponds exactly to that seen when the radial is
divided low in the forearm.

The loss of sensation to prick is at every point shghtly less than the loss to
light touch. Moreover, in Case 46, and Case 47, the terminal phalanx of the
thumb around the root of the nail was not completely analgesic. But, if the
median is also divided, the whole of the thumb becomes entirely insensitive
to prick. In Case 44, division of the branch of the median running to the uhiar
aspect of the thumb caused complete analgesia of that half of the terminal
phalanx which before had been partly sensitive to prick.

We are now in a position to determine, by the method of residual sensibility,
the full extent of the area on the back of the hand innervated by the median
nerve. The series of cases we have cited, where the radial and external cuta-
neous were divided, shows that the median sends fibres to the following area.
It supj)lies with sensibihty to hght touch the terminal two and a half phalanges
of the index and middle fingers, the whole palmar aspect of the thumb, and
aU excepting the outer thnd of the thenar eminence. As far as sensation to
Hght touch is concerned, this part of the thenar eminence is innervated from
the radial, but its sensibihty to pain comes through the median and external
cutaneous nerves.

The median nerve supphes sensibihty to prick, and the more extreme
degrees of temperatm-e, to the terminal phalanges and at least three-quarters
of the basal phalanx of the index and middle fingers. The proximal part of
the thenar eminence receives its sensibihty to these stimuli through both the
median and external cutaneous nerves. This accounts for the infrequency
with which the proximal part of the thenar eminence becomes analgesic in
consequence of division of the median nerve.

CHAPTER V

INJURIES TO THE BRACHIAL PLEXUS

The nerve trunks which compose the brachial plexus are not uncommonly
injured by violence to the shoulder, particularly if the humerus is dislocated.
But it is rare for such injuries to cause complete paralysis of sensation over the
distribution of any one cord; sensibility to hght touch is usually aboHshed
over a well-defined area of considerable size, but a prick is everywhere appre-
ciated, or the extent of the analgesia is comparatively trifling. The foUomng
case illustrates the usual results of such an injury.

Case 48. — Injury to the inner cord of the brachial plexus.

On January 1, 1903, an elderly man fell over a door-mat, dislocating his left shoulder. The
next morning, he noticed he could not move his hand. On the third day following the accident,
he came to the London Hospital, where the dislocation was reduced, and the arm strapped and
bandaged across his chest. So it remained for fourteen days, and when the bandages were
removed he complained of weakness of the arm and hand. On February 25, when he first came
under our care, his condition was as follows : The shoulder joint was stiff, and movement was
somewhat limited, especially when he attempted to raise his arm. There was no change in the
appearance of the skin or nails. Light touch was not appreciated over the whole ulnar aspect
of the forearm and hand on both its flexor and extensor aspects. Over this area, water at 22° C.
and at 38° C. was nowhere appreciated as cool or warm ; ice, and water at 50° C, were recognised
everywhere correctly. Sensation to prick was unaft'ected, and no definite line of change could
be marked out by drawing a pin across the skin from normal to abnormal parts.

The hand was held with the thumb abducted and extended ; the fingers were extended at the
metacarpo-phalangeal, and slightly fiexed at the interphalangeal joints, and the little finger was
also somewhat abducted. Thenar and hypothenar eminences were wasted, and the interosseous
spaces deeply hollowed. The flexor carpi ulnaris was not acting, and, on telling him to close
his fingers, the wrist was extended and the fingers feebly flexed at the interphalangeal joints.
None of the intrinsic muscles of the hand, including those of the thumb, could be voluntarily
contracted, but the long muscles of the thumb were acting well. The flexor carpi ulnaris and
all the intrinsic muscles of the hand failed to react to the intermitted current, and contracted
sluggishly to galvanism.

He rapidly recovered sensation, and by March 8, 1903, light touch, although materially
diminished, was appreciated over the whole forearm and hand. Sensibility to minor degrees of
heat and cold had also returned, and water at 22° C. and 38° C. was accurately chstinguished.

In this case, the inner cord of the brachial plexus must have suffered

in consequence of dislocation of the shoulder, the injury being sufficient

only to abohsh for a time sensibility to light touch and minor degrees of

temperature.

115

116

STUDIES IN NEUROLOGY

Case 49. — Profound loss of sensation produced by dislocation of the shoulder.

In the case of Arthur M., a similar injury produced a more profound paralysis of sensation.
On October 2, 1901, he dislocated his right humerus. He was admitted at once, and the dis-
location was reduced under an anaesthetic. The next day it was discovered that sensation was
lost over the ulnar half of the forearm and hand, and that all the muscles in the hand supplied
by the median and vdnar nerves were paralysed. When he came under our observation on
December 4, 1901, the condition was exactly that found on the morning after the dislocation had
been reduced. Over the area shown in fig. 17 every form of cutaneous sensibility was lost. No
movement of the thumb and little finger could be performed, and all the interossei were paralysed.
The flexor carpi ulnaris, the ulnar half of the flexor subHmis, and the small muscles of the hand
did not react to the interruiDted current; but the extensor muscles and flexor carpi radialis
responded normally.

Fig. 17.

To show the area which became insensitive in Case 49, in consequence of dislocation of the shoulder.
The upper two figures show the extent of the loss to light touch; the lower two the area insensitive
to prick.

Here the lesion must have been sufficiently severe completely to destroy
conduction in the inner cord of the brachial plexus on the central side of the
point where the inner head of the median is given off.

In the follo%\ing case, the injury was still more severe, and for a time
conduction must have been entirely interrupted in all the three cords of the
brachial plexus.

Case 50. — Fracture of the surgical neck of the humerus, causing rupture of cords of the brachial
plexus.

Alfred H., a boy of 14, was brought to the London Hospital on October 11, 1898, and admitted
imder the care of Mr. Jonathan Hutchinson. A large box had fallen upon him, striking his left

INJURY TO THE PERIPHERAL NERVES 117

shoulder; he was unconscious and collapsed. The humerus was fractured through its surgical
neck, and signs pointed to grave internal injury, probably rupture of the kidney. He slowly
recovered, and the bone united firmly. On December 12, 1898, he was first seen by one of us,
in consequence of the remarkable paralysis both of motion and sensation in the left arm. He
was an unusually intelligent boy, well developed for his age. All the muscles around the shoulder-
joint, in the arm, forearm, and hand were greatly wasted. The left arm hung powerless to his
side. All the muscles of the left hand and forearm, together with the brachialis anticus, biceps,
triceps, deltoid, and latissimus dorsi, were paralysed. None of the movements usually associated
with contraction of the pectoralis major could be performed. The rhomboids, serratus magnus,
and upper part of the trapezius contracted well; the lower part of the trapezius was almost
certainly acting. All reaction to the interrupted current was abolished in the muscles of the
hand and forearm, the biceps, deltoid, fiectoralis major, supra- and infra-spinati, and the latis-
simus dorsi. The serratus magnus, trapezius, and rhomboids reacted briskly. To galvanism
all the muscles that had previously failed to react to the interrupted current contracted sluggishly,
but the rhomboids, serratus, and both parts of the trapezius reacted with a brisk contraction.

All forms of cutaneous sensibility were lost over the area shown in fig. 18. Deep touch was
not appreciated up to the elbow, but undoubtedly produced sensation over the whole of the arm
above that joint.

The left hand was blue, cold, and swollen; the nails showed no definite change. He had
burnt the fingers at the fire, but the burns were healing well.

The left palpebral fissure was smaller, and the whole eye looked somewhat sunken compared
with the right. In daylight the right pupil measured 4 mm., the left 3 mm., and when shaded
the right enlarged to 6 mm., the left to 4 mm. The pupil on the affected side was somewhat
oval in shaj^e, with its long axis placed vertically; it dilated well to a 2 per cent, solution of
cocaine and became regular in outline. At the same time the narrowing of the palpebral fissure
disappeared, so that excepting for the dilated pupil no difference could be detected between the
two eyes.

On December 16, 1898, Mr. Hutchinson explored the brachial plexus above the clavicle and
found that the upper and middle trunks were matted in firm fibrous tissue ; the remaining parts
he was unable to see. Both trunks were incised and found to consist at the j)oint of the incision
of tough fibrous tissue ; a small portion was removed and the ends reunited.

This procedure made no alteration in the extent of the motor or sensory paralysis, showing
that all the fibres entering these cords from the limb had been completely interrupted as a
consequence of the accident.

By August, 1902, he had grown to be a man, but the injured arm showed an extraordinary
combination of wasting and deficient growth. The fingers were flexed into the palm ; the nails
were long and curved, but not tender. No change could be detected in the elbow joint, and
movement was free, except for the limitation due to contracture of the bicej^s. The deltoid,
triceps, supinator longus, and all the extensors were still paralysed. The pectoralis major,
latissimus dorsi, trapezius, and serratus acted well, and even the biceps, in spite of its contracted
condition and small size, was acting. The wrist was flexed by means of the flexors of the fingers,
which were permanently shortened, so that their contraction produced no movement in the
fingers. All the intrinsic muscles of the hand were entirely paralysed and profoundly wasted.

Sensation to light touch was lost over an area so exactly that of four years before that the
two figures were identical. But sensibility to prick and to the more extreme degrees of heat and
cold had recovered to a remarkable degree. The whole hand, back and front, was still insensitive,
and the analgesia extended for a short distance above the wrist, both in front and behind.
Water at 38° C. was not appreciated over the large area of the upper limb insensitive to light
touch; but ice and water at 50° C. were recognised everywhere above the lower third of the
forearm.

By August of the same year, sensibility to prick and to the extremes of temperature had
further increased, but the loss of light touch was unaltered. By March, 1904, prick was appre-

118

STUDIES IN NEUROLOGY

IlG. 18.

To show the area which became insensitive to all forms of cutaneous stimuli in Case 50, in
consequence of rupture of the cords of the brachial plexus.

INJURY TO THE PERIPHERAL NERVES 119

ciated everywhere, and even sensation to light touch had returned, excepting over the pahn
and dorsal aspect of the little and ring fingers. The palmar surface of the fingers could not be
tested in consequence of the contracture. The biceps, triceps, supinator longus and flexors, and
extensors of the wrist and fingers reacted to the interrupted current ; even the wasted remains
of the thumb muscles flickered under the application of an unusually strong interrupted current.

The lesion, which caused this extensive paralysis of motion and sensation,
must have been situated on the distal side of the point where the posterior
thoracic (n. thoracalis longus) comes off from the fifth, sixth, and seventh cer-
vical nerves to supply the serratus magnus. The nerve to the rhomboids was
unaffected, but the conductivity of the nerves to the pectorals and to the
latissimus dorsi was destroyed. Thus, the injury must have torn the brachial
plexus between the point where the long thoracic and the suprascapular nerves
are given off. The nerves forming the lower trunk must have been injured
to such a degree that no form of cutaneous sensation could reach the central
nervous system, excepting through the lesser internal cutaneous. Partial
paralysis of the cervical sympathetic is accounted for by injury to the branch
given off from the first dorsal nerve, or interference with the sympathetic
when it lies on the neck of the first rib.

In all previous instances, destruction of one or more nerve trunks always
caused a loss of sensibility more extensive to hght touch than to prick. In
this case, all forms of cutaneous sensation were aboUshed over the same area ;
the upper limit was a firm line even in the neighbourhood of the acromion,
where considerable overlapping occurs between the various peripheral nerves.

Cases of this kind reveal the physiological constitution of the brachial
plexus. But they are rare ; for its trunks or cords alone are injured in but a
small percentage of the lesions of the plexus. The majority resemble more
closely the following case, where not only the cords, but also the nerves arising
directly from them, had been damaged.

Case 51. — Fracture of the neck of the scapula with injury to the circ\imflex, the ubiar and the
internal cutaneous nerves.

On June 25, 1901, George B. was admitted to the London Hospital under the care of Mr.
Jonathan Hutchinson for paralysis of the left arm and hand. An iron girder had fallen on
to his shoulder on October 4, 1900, fracturing the neck of the scapula, and causing so much local
injury that the nervous lesion was overlooked. The onset of the loss of sensation could not be
dated, but in January, 1901, he first noticed that his arm was wasted.

The condition of his arm in July, 1901, was as follows : The deltoid and biceps were wasted
and completely paralysed ; the triceps acted poorly, and was diminished greatly in volume. All
the interossei and muscles of the little finger were wasted and paralysed, but those of the thumb
contracted normally. The deltoid, infraspinatus and biceps did not respond to the interrupted
current, and contracted sluggishly to galvanism. The condition of the triceps was doubtful.
All the muscles of the thumb reacted well, but no reaction was obtained from any other muscles
in the hand.

Sensation was lost over the area shown in fig. 19 corresponding in the forearm and hand to
an injury of the ulnar and internal cutaneous nerves just after they have left the brachial plexus.
On the flexor surface of the forearm, the loss was co-terminous for all forms of sensation ; but

120

STUDIES IN NEUROLOGY

Fig. 19.

To show the insensitive areas in Case 51, caused by an injury which fractured the neck of the
scapula. The area on the arm corresponds to the distribution of the circumflex. The loss of sensation
on the forearm and hand is due to injury of the internal cutaneous and uhiar nerves.

INJURY TO THE PERIPHERAL NERVES 121

on the extensor surface there was a difference of nearly 2 cm. between the borders of loss to
touch and to prick.

On the outer side of the arm, also over the region of the deltoid, sensation was altered within
an oval area 14 cm. in length and 6 cm. in breadth. Towards the upper and the posterior
aspects, the borders of this patch were well defined, and the loss to prick corresponded in extent
with the loss to light touch. But both the lower border and that on the anterior aspect of the
arm were indefinite, the loss of sensation merging gradually into parts of normal sensibility.
Moreover, the extent of this loss of sensibility to prick and to the extremes of heat and cold was
materially smaller than that of the loss to light touch. Thus, the relation between the loss of
light touch and of prick was exactly that seen when a peripheral nerve is injured.

On July 17, 1901, Mr. Hutchinson explored the brachial plexus above the clavicle, and fomid
no sign of any abnormality in the nerves or cords of which it is composed.

From the nature of the loss of sensation, both over the deltoid region and
in the forearm, it is probable that in the main the injiuy lay on the distal side
of the point where the nerves had combined to form the cords of the plexus.
Fracture of the neck of the scapula must certainly have injured the supra-
scapular nerve, and also the circumflex. The internal cutaneous and ulnar
nerves must also have suffered in consequence of the violence of the injury.

CHAPTER VI

LOSS OF SENSATION IN THE ARM FROM DIVISION OF POSTERIOR NERVE ROOTS

In every case we have brought forward so far, the loss of sensation has
been caused by division of afferent nerve fibres on the distal side of the posterior
root ganglion. To complete our knowledge of the distribution of sensation,
it will be necessary to consider the results which follow injury to the posterior
roots. For this purpose the consequences of disease are rarely, if ever, suffi-
ciently definite. But during the last ten years. Sir Victor Horsley has
occasionally divided the posterior roots for intolerable and obstinate pain.
To his Idndness in allowing us to examine the patients in whom he has
performed this operation, we owe the opportunity of completing this part
of our subject.

Case 52. — Excision of the fifth, sixth, seventh, and eighth cervical, and first and second dorsal
posterior roots.

Ellen E., aged 45, was admitted to the National Hospital, Queen Square, under the care of
Dr. Beevor, in March, 1898. Thirteen years before she had cut her right forearm with a glass
lamp shade, and ever since had complained of pain in the arm ; portions of various nerves were
excised on fourteen occasions. Of the condition of sensation before the nerve roots were divided,
we are unable to speak from personal observation. However, all who saw her agreed that
whatever loss of sensation may have been present ceased a few inches above the wrist.

On May 31, 1898, Sir Victor Horsley opened the dura mater, and excised the fifth, sixth,
seventh, and eighth cervical, and first and second dorsal posterior roots. She recovered perfectly
from the operation, and when seen by one of us on August 26, was bright and cheerful and free
from pain. Sensation to prick was lost over the whole of the forearm and hand, and over the
greater part of the arm, as shown in fig. 20. Cotton wool was appreciated over part of this area,
and the loss to light touch was less extensive than loss to prick everywhere on the arm. Whilst
the border of the area insensitive to prick was extremely definite, that of the loss to light touch
merged gradually into parts of normal sensibility. Water at 50° C. and ice were not appreciated
over the analgesic area.

Here the extent of the skin insensitive to prick exceeded considerably that
insensitive to Ught touch. The following case shows the remarkable behaviour
of this area Avhen tested with various degrees of temperature.

Case 53. — Division of the fifth, sixth, and seventh cervical posterior roots.

F. M., a woman of 31, had suffered from obstinate pain in the right arm for several years.
In February', 1902, Sir Victor Horsley opened the spinal canal and divided the fifth, sixth, and
seventh cervical posterior roots.

She was seen by one of us on May 15, 1905, and on several subsequent occasions, when the

122

INJURY TO THE PERIPHERAL NERVES

123

Fig. 20.

To show the loss of sensation produced by division of six posterior roots (C. 5, G, 7, 8, D. 1 and 2)
in Case 52.

As the area insensitive to prick was of greater extent than that insensitive to light touch, the
boundaries of the two areas are marked by a thick continuous and a thin dotted line respectively.

124

STUDIES IN NEUROLOGY

conditions were unusually favourable to careful examination. On account of her great intelli-
gence and remarkable trustworthiness, the sensory observations made on this patient, particularly
with regard to her sensibility to temperature, were of peculiar value.

Fig. 21.

To show the upper border of the area insensitive to prick and to the more extreme degrees of heat
and cold in Case 53. The extent of the loss of sensation to light touch and to the intermediate degrees
of heat and cold was smaller than that of the analgesia, and thus an area of dissociated sensibility
was produced, fully described in the text. The dark line encloses the parts insensitive to prick ; the
dotted area corresponds to the loss of sensation to light touch. The hand is not included, as its
sensory condition was comphcated by division of several peripheral nerves.

The area on the arm and forearm insensitive to cotton wool and the extent of the analgesia
are shown on fig. 21.

This loss of sensation is the result of division of the posterior roots. The sensory condition
of the hand will be neglected, for it was complicated by operations on the peripheral nerves,
both at the wrist and in the palm. Li the previous instance cited in this chapter, the area

INJURY TO THE PERIPHERAL NERVES 125

insensitive to prick greatly exceeded in extent that of the loss to light touch, particularly over
the outer aspect of the arm. A similar area sensitive to cotton wool but insensitive to prick
was found in F. M. ; it measured 7 cm. in the longitudinal, and 7-5 cm. in the transverse axis,
of the limb. In addition, a large part of the radial half of the flexor surface of the forearm was
in a similar condition of sensibility, analgesic to prick, but sensitive to stimulation with cotton
wool.

Tested with the compasses over the deltoid region, there was little difference between the two
sides. With the two points 4 cm. apart, applied longitudinally to the arm, she answered correctly
every time on the sound side; but, on the affected side, the record was as follows : .m'^^'r^'.
At 3 cm. the threshold had been obviously passed on both sides. Thus, she showed little differ-
ence in her power of discriminating two points on similar parts of the two arms, although the
area to which they were applied on the affected side was entirely insensitive to prick.

Sensation to pressure was retained everywhere above the wrist, and the vibrations of the
tuning-fork were appreciated both on the forearm and arm.

It is, however, to the reaction of this patient when stimulated with heat and cold that we
wish to draw particular attention. Over the deltoid region on the affected arm, she could tell
the difference between 38° C. and 25° C, saying that the first was warm, the second cool. But
she was unable to recognise any difference between ice and water at 65° C. ; 20° C. was distinctly
cold, but ice in comparison was said to be neutral. The lowest temperature she recognised lay
between 15° C, which was not appreciated, and 18° C, which seemed to her undoubtedly cool.
Her sensations of warmth ranged from about 35° C. to 55° C. ; all specific sensation ceased at
this temperature, and the stimulus was appreciated as a touch only. When 55° C. and 40° C.
were compared, the latter appeared more definitely warm, and her answers were more certain with
the lower than with the higher temperature.

The condition of the area of dissociated sensation on the forearm was, in principle, the same,
although in consequence of the general diminution of sensibility it could not be so minutely
explored. Here also ice and water at 65° C. were not ai^jireciated, but 21° C. and 38° C. were
called respectively warm and cool.

From these two cases, and from others where the lesion was less certainly
determined, it would seem that division of several posterior roots abohshes
sensation to prick over an area larger and more sharply defined than that which
becomes insensitive to fight touch. Moreover, this insensibifity to prick may be
accompanied by an inabifity to appreciate temperatures below 15° C. and above
60° C, although 40° C. and 23° C. may appear definitely warm and cool.^

^ Smce this paper was published I have examined several additional examples of division of
the posterior roots supplying the upper extremity. In every case the extent of the loss to
prick exceeded that of the loss to the tactile hairs on cotton wool ; this is the outstanding
result, which can be verified with ease. The dissociated area is not only insensitive to all
cutaneous painful stimuli, but does not resijond to tubes contaming ice or water at from 45° G.
to 50° C. It is apparently devoid of all heat- and cold-spotti. But it is extremely difficult to
be certam of the effect produced by temperatures of from 20° C. to 40° C. The portion of the
arms at our disposal is not normally endowed with high thermal sensibility, and I have found
the same tendency to call all stimuli " warm,"' which was so confusing over the triangular
area on my arm [p. 285].

CHAPTER VII

nerve supply of the lower limb

§ 1. — The Sole of the Foot

The nerves of the lower limb are much less frequently injured than those
of the arm and hand, and most of the injuries fall either upon the sciatic or
upon the external pophteal. Wounds that divide the nerves to the sole of
the foot in the neighbourhood of the ankle are so uncommon that it is
impossible to determine the distribution of the internal and external plantar ;
but the following instance shows in a remarkable way the nature and extent
of the sensibiUty supplied by the posterior tibial nerve.

Case 54. — Division of the posterior tibial nerve at the ankle.

On May 16, 1901, J. T., while serving in South Africa, was shot through the right leg. The
foot became " numb " and useless at once, but fourteen days later " feeling " came back. This
return of sensation was associated with so much pain in the sole of the foot that the condition
of the nerve was explored from the popliteal space, two months after the injury. He returned
to England on August 22, and was sent to Devonport Hospital. There the posterior tibial nerve
was cUvided just behind the internal malleolus, " in order to stop the swelling of the foot," and
in consequence the whole sole became " numb."

In August, 1902, he came under the care of one of us at the London Hospital. The scar
caused by the entry of the bullet lay just anterior to the tendon of the biceps femoris, 3 ins.
(7-5 cm.) above its insertion; the wound of exit was 4 ins. (10 cm.) above the head of the tibia
over the inner group of hamstring muscles. Li the centre of the popliteal space was a well-
healed surgical scar, a relic of the first operation, and behind the internal malleolus lay another
scar, IJ ins. (3-5 cm.) in length, due to the operation in Devonport Hospital.

All the muscles below the knee reacted to the interrupted current, but the only movement
of which they were capable was extension of the foot.

He complained that his foot was sore when he put it to the ground, and that this jirevented
him from walking.

The right sole was entirely insensitive to touch with cotton wool, a stimulus which he easily
appreciated over the whole of the normal foot. Sensibility to prick was nowhere lost, but,
wherever light touch was defective, a prick caused increased discomfort, and was associated with
a sensation of pins and needles. The whole of this area was insensitive to water at 15° C. and
at 40° C, but water at 50° C. was said to be " very hot," and ice produced a sensation of numb,
tingling cold. Over the sole of the right foot, the points of the compasses could not be dis-
criminated when separated for 6 cm., whilst on the sound foot he made two mistakes only when
they were 2 cm. apart.

We concluded from the physical signs that in this case the bullet had injured the sciatic nerve
just above the popliteal space. Sensibility to pain was probably abohshed for a few weeks only,
and then, on the way to recovery, the foot became over-sensitive to all painful stimuli.
Gradually the nerve regained its power of conduction, and the muscles their normal reaction.

126

INJURY TO THE PERIPHERAL NERVES

127

But meanwhile, in consequence of division of the posterior tibial nerve, the sole of the foot had
become insensitive, and he was in a worse position than he would have been without the operation.
On August 15, 1902, Mr. Barnard cut down on the structures behind the internal malleolus.
A mass of firm fibrous tissue was exposed, and when this was dissected away, the two ends of the
nerve were seen, the upper a bulbous mass and the lower spread out over, and closely adherent
to, the vein. The nerve was dissected with difficulty from the vein, and when completely free
was found to consist of an upper and a lower end connected by dense fibrous tissue. This
intervening tissue was incised at several points, until the normal fibres of the central end were
exposed. The distal end of the nerve was treated in a similar way, until nerve fibres in considerable
number became visible. The two ends of the nerve were then united together.

Fig. 22.

To show the area of cutaneous insensibility produced by division of the posterior tibial nerve
(Case 54). Before the operation on August 15, 1902, the whole of the parts enclosed by the single
line were insensitive to light touch, and to the minor degrees of heat and cold. After the operation
the loss of sensibility to these stimuli remained unaltered, but the parts in black became insensitive
to all cutaneous stimuli.

After this operation all pain disappeared, the extent of the loss of sensation to light
touch remained unaltered, but sensibility to prick was lost over a wide extent of the sole
(fig. 22). Over the whole of this area all degrees of temperature were unappreciated. When
passing from normal to affected parts of the foot, minor degrees of temperature, such as
20° C. and 40° C, were no longer appreciated as soon as the border for loss to light touch was
passed.

This case shows that the posterior tibial nerve supphes the sole of the
foot with all forms of cutaneous sensibility. On the inner side, the border
at which sensibihty ceases is a well-defined line identical for all forms of
sensation. But over the outer side, both the area of loss of sensation to
light touch and that of the analgesia merge gradually into parts of normal
sensibihty, the loss of hght touch exceeding in extent that of the loss to
prick. From their plantar aspect, the toes were insensitive to light touch,
but remained sensitive to prick.

Here also, as in the hand, recovery of sensation after complete division
of the nerve began with a return of sensibility to painful stimulation, and

128 STUDIES IN NEUROLOGY

to ice, and water at 50° C. The parts affected remained insensitive to light
touch and to minor degrees of heat and cold, and two points could not be
differentiated, even when separated to a distance of 6 cm.

That this return of sensibility was not due to substitution from the sur-
rounding nerves is shown by the complete loss of all sensation produced by
again dividing the affected nerve in order that its two ends might be sutured
together.

§ 2. — ^Loss OF Sensation produced by Injury to the Nerves of the Leg

Division of the external popUteal nerve, below the point at which its
lateral cutaneous branch is given off, causes loss of sensibihty to Ught touch
over a considerable portion of the outer side of the leg and over the whole of
the dorsum of the foot (fig. 23, a). Within these hmits sensibility to prick is
evidently diminished, but is nowhere lost entirely, except over the dorsum of
the foot (fig. 23, b). These figures, illustrating the loss of sensation produced
by division of the external popUteal, were obtained from the following case.

Case 55. — Injury to the external popliteal ; resection and svture of the nerve.

Joseph B. was admitted to the Poplar Hospital, under the care of Mr. Rigby, in July, 1900,
with a compound comminuted fracture of the left tibia and fibula. Whilst falling, the right
leg turned under him, and he sustained a slight womid over the external condyle of the right
femur. This wound healed rapidly, but three weeks after admission the patient was found to
show signs of paralysis of the right external pojiliteal nerve. In spite of massage, the leg was
still paralysed when he first came under our notice in October, 1901. Mr. Rigby therefore
explored the nerve at the site of the injury and found it hard and firm, embedded for a
distance of 1| ins. (4 cm.) in fibrous tissue; it had evidently been partially ruptured, and
the upper end was bulbous and united to the lower portion by a strand of fibrous tissue. An
inch and a half (.3"75 cm.) was excised and the two freshened ends were reunited with silk
sutures.

The paralysis of motion and sensation was in no way increased by this operation, proving
that the pre-existing condition was due to complete functional cUvision of the nerve.

The whole anterior tibial group of muscles (tibialis anticus, extensor longus digitorum and
extensor hallucis), together with the peronei, were paralysed and had lost their reaction
to the interrupted current. The flexor muscles of the toes and the muscles of the calf
acted well.

The loss of sensation to light touch and to the jsainless interrupted current, shown on fig. 23, A,
was bounded towards the shin and on the imier side of the dorsum of the foot by a definite line,
but above, merged gradually into parts of normal sensibility. Sensation to prick was disturbed
over an area of smaller extent (fig. 23, B), but the boimdary on the inner side of the dorsum of the
foot coincided with that of loss of light touch. Ice and water above 50° C. were not appreciated
over the analgesic area, and he was miable to discriminate minor degrees of heat and cold over
those parts where sensibility to light touch was destroyed. Deep touch and pressure were recog-
nised everywhere over the affected parts. Over the dorsum of the sound foot, he could ajjpreciate
the two points of the compasses correctly when 4 cm. apart ; at tliis distance he failed entirely
over a similar part of the affected foot.

When the external popUteal is divided below the origin of its lateral
cutaneous branch, the posterior (sural) border of the loss of sensation is always

INJURY TO THE PERIPHERAL NERVES

129

ill-defined in contrast to the astonishing definiteness of the anterior border.
But when the continuity of the whole of this division of the sciatic is destroyed
above the point where the lateral branch is given off, the posterior border in
the calf becomes as definite as that on the shin (fig. 24).

Fig. 23.

To illustrate Case 55.

A shows the extent of the leg insensitive to light touch, and the intermediate degrees of tempera-
ture after division of the external popliteal below its lateral cutaneous branch. The area of complete
insensibility is shaded.

B shows the extent of loss of sensation to prick. The area of total analgesia is marked in black.

Case 56. — Complete division of the external popliteal nerve above the origin of its lateral branch.

On December 25, 1901, whilst serving in South Africa, Charles G. was shot through the right
thigh with an explosive bullet. He fell, and at once discovered that he could not move liis leg.

When we saw him at the Royal Victoria Hospital, Netley (March 26, 1902), the wound of
entry on the posterior aspect of the thigh 5 ins. (12-5 cm.) above the centre of the popliteal sjaace
had healed. On the outer surface of the thigh was a triradiate scar nearly 4 ins. (10 cm,) from
end to end, in the centre of which lay a small area not completely healed.

VOL. I. K

130

STUDIES IN NEUROLOGY

The antorior tibial and peroneal groups of muscles were paralysed, much wasted, and did
not react to the interrupted current. The foot could be inverted and the toes flexed ; the calf
muscles, though somewhat wasted, contracted strongly and reacted to the interrupted
current.

Sensibility to light touch was lost within the dotted line on fig. 24. It Avill be evident how
closely its anterior and posterior borders correspond with the extent of the loss of sensation to
prick marked in black. The upi^er border and the border on the outer side of the foot were
indefinite, merging into parts of normal sensibility.

Fig. 24.

To illustrate the loss of sensation produced by division of the external popliteal above its lateral
cutaneous branch (Case 56).

Total cutaneous insensibility is marked in black; this area merges above and below into parts
sensitive to prick, but insensitive to light touch. The loss of sensation to light touch is enclosed in
a dotted line. Above and on the outer side of the foot this area of loss to light touch merges into
parts of normal sensibility.

Wounds of the thigh dividing the sciatic nerve completely are comparatively
so rare in civil life that we are compelled to construct the full picture of the
consequences of such an injury from a comparison of several cases, not one of
which is in itself entirely satisfactory.

Thus, in the case of Wilham B. (No. 57 i), where the injury was caused
by a bullet wound of the nerve in the region of the buttock, muscular paralysis
was complete below the knee. But we did not see him until ten months
after the injmy, and by that time sensation had already begun to improve.
Yet an examination of fig. 25 shows the well-marked border on the anterior
surface of the leg, and on the inner aspect of the foot, produced by a comj)lete
lesion of the great sciatic.

1 Vide p. 223.

INJURY TO THE PERIPHERAL NERVES 131

The full extent of the loss of sensation to light touch, produced by division
of the great sciatic, is shown on fig. 26. But here, again, although all the
muscles supplied by the great sciatic were absolutely paralysed and the antes-
thesia to light touch was of the full extent, sensibihty to prick had begun to
return on the outer side of the leg.

Fig. 25.

To illustrate Case 57. The loss of sensation, produced by injury to the small sciatic, is shown on
the thigh and buttock, total insensibility to all cutaneous stimuli being shown in black. The extent
of the loss to light touch is shown by a single dark line.

Below the knee the loss of sensation was caused by injury to the great sciatic nerve, which had
already begun to recover, the two forms of sensibility retui'ning together, as usual, with partial
injuries.

Case 58. — Complete division of the great sciatic nerve in the thigh.

On May 20, 1896, Benjamin A. was stabbed in the thigh during a brawl. About the middle
of the back of the thigh was an incised wound which had completely divided the semitendinosus
muscle. He was collapsed, having lost much blood. The wound was miited, after suture of
the muscle, and healed well.

As soon as the wound had healed, all the signs were discovered of division of the great
sciatic nerve. All movements of the foot and ankle were impossible, and sensation to touch
and to prick was lost over the outer asjDect of the leg and over the dorsum and sole of
the foot.

On July 30, 1896, the condition of the nerve was explored by Mr. Ojienshaw. It had been
entirely cut across, and the two ends were united by librous tissue ; the two ends were freshened
and reunited with silk sutures.

He was first seen by one of us in February, 1899, nearly two years and a half afcer th's opera-
tion. All the muscles supplied by the sciatic were paralysed and failed to react to the inter-

132

STUDIES IN NEUROLOGY

rupted current. The extent of the loss of sensation to cotton wool is shown on fig. 26. The
foot and a small part of the outer aspect of the leg were insensitive to prick, and to heat and
cold, but, as this form to sensibiHty had obviously begim to improve, the insensitive area has
been omitted.

The most complete loss of all forms of sensation produced by a wound
of the great sciatic which has come under our notice was in the case of H. N.
(No. 59), wounded on February 25, 1902, wliilst serving in South Africa.
When we first saw him, five months later, of the muscles below the knee, the

> ';

Fig. 26.

To show the extent of the area that became insensitive to light touch in consequence of division
of the great sciatic in the thigh (Case 58). The extent of the analgesia, which occupied the whole foot
below the level of the ankle, "has not been inserted, for the sensibility to prick had recovered considerably
before we first saw this patient.

gastrocnemius alone was acting, and all of them with this exception failed
to respond to the interrupted current. The extent to which sensibility was
lost in this case is seen on fig 27, which shows the nature of the anterior and
posterior borders, and the considerable loss on the inner aspect of the foot.

Case 59. — Bullet ivoiind of the thigh, injuring the great sciatic nerve.

Henry N., aged 22, was shot through the right thigh on February 25, 1902, whilst serving as
an Imperial Yeoman. He was removed to hospital, and the wound healed in three weeks. After
his arrival at the Royal Victoria Hospital, Xetley, on July 3, the leg was massaged daily, and when
we first saw him, on August 2, 1902, he had begmi to improve.

The bullet had entered on the posterior surface of the thigh, 4 ins. (10 cm.) above the
centre of the popliteal space ; the wound of exit lay on the anterior and internal aspect, 1 J ins.
(4 cm.) above the patella. Immediately imder the wound of exit, a well-defined hole had been
drilled through the bone by the bullet.

INJURY TO THE PERIPHERAL NERVES 133

All the muscles of the thigh were acting; but below the knee, only the gastrocnemius con-
tracted voluntarily, and that feebly. This muscle reacted to the interrupted current, and the
reaction to the constant current was normal. No other muscles below the knee reacted to
the interrupted current, and both the anterior and external groups responded more readily to
the anode than to the kathode.

Light touch was not appreciated over the area shown in fig. 27, and it will be seen how closely
this loss of sensation coincided with that to prick, excepting only at its proximal border.

Fig. 27.

To illustrate the loss of sensation in Case 59. The area insensitive to light touch, and to the
intermediate degrees of temperature, is enclosed in a dark line, dotted where the border is not well
defined. The parts insensitive to prick and to all forms of temperature stimulation are coloured
black.

§ 3. — The Nerve Supply of the Leg deduced from Residual Sensibility

So far we have attempted to determine the loss of sensation produced
by division of the main nerve trunks of the leg. But loss of sensation does
not reveal the full cutaneous distribution of an injured nerve. This we can
only learn by observing the limits of the area which remains sensitive when
all the surrounding nerves have been destroyed. In the previous section,
each case was arranged to show the loss of sensation caused by injury to a
particular nerve. Here the same cases will be regarded from the opposite
aspect ; division of the posterior tibial will be cited to reveal a portion of the
boundary of the external popliteal, and the limits of the internal saphenous
will be mapped out by a consideration of the consequences that followed
injury to the great sciatic. Where the boundaries for sensation to Ught

134

STUDIES IN NEUROLOGY

touch and to prick coincide, this method of residual sensibiUty produces results
that can be easily comprehended. But, where these borders are widely
separated, the results will appear at first complex and difficult.

We shall, therefore, begin Tvith a consideration of the boundaries of the
internal or long saphenous, a nerve whose Hmits are easily determined by
this method. When conduction in the great sciatic is completely destroyed,
the long saphenous alone supphes sensation to those parts which remain
sensitive over the lower half of the leg and inner side of the foot. By com-
paring the cases where the internal saphenous alone supplies sensation to

the leg, the nerve is found to
innervate for hght touch and for
pain the parts shown on fig. 28.
On the front of the leg, the
distribution of the two forms of
sensibility closely agrees, but on
the inner side of the foot and
over the calf of the leg, the
fibres that subserve sensibihty
to hght touch are less xvidely
distributed than those which
conduct sensation of prick.

In attempting to estimate
the full distribution of the ex-
ternal popliteal, of its lateral
cutaneous branch, or of the
external saphenous, it must be
remembered that, as far as hght
touch is concerned, these three
nerves form a group supplying
the post-axial half of the leg.
The boundaries of the area
they supply on the shin and the calf are extremely definite, but all borders
which are not coincident with these lines are ill defined. Whenever the
hmits of any one of the constituent branches coincide with one or other of
these lines, the boundary is sharpl}?- defined, at every other part its borders
merge gradually into the parts supplied by other members of the group.
This makes it impossible to map out the post-axial half of the leg into
well-defined areas, each innervated by one of the branches which forms the
constituent elements of its nerve supply. The constitution of the external
saphenous is an additional hindrance to analysis of this part of the leg. For
destruction of the whole external pophteal mil remove all the sensibility
from the outer side of the foot which depends on the integrity of its peroneal
communicating branch, whilst that part innervated by the tibial communicat-
ing will be rendered insensitive by division of the internal pophteal.

Fig. 28.

To show the area supplied by the iiiternal saphenous,
deduced from the residual sensibility after comiilete
division of the sciatic nerve. The boundaries of this area
are almost co-terminous, whether light touch or prick be
used as the stimulus. The extent of residual sensation
in the direction of the great toe varies in diiferent cases.

INJURY TO THE PERIPHERAL NERVES

135

v.. t

Fig. 29.

To show the full extent of skin supplied by the lateral cutaneous branch of the external popliteal
nerve. The upper figure (A) shows the area suppHed with sensibility to light touch; the lower
figure (B) shows the extent supplied with sensibility to pain.

Again, to complete the analysis of this part of the leg a case of complete
division of the internal saphenous is wanted, that we may observe the full
extent of skin supplied by the sciatic nerve.

On fig. 29 is shown the full distribution of the lateral cutaneous branch
obtained by subtracting the area of total loss of sensibiUty due to division

136 STUDIES IN NEUROLOGY

of the external popliteal below its lateral branch, from the complete area
supplied by the great sciatic. Both for touch and for prick the territory of
this nerve seems to be bounded by a sharply- defined border over the shin
and over the calf. But towards the periphery of the Hmb, its limits are
extremely ill defined ; a large part of the outer aspect of the leg is shared by
this branch in common with the external popliteal. As usual in such circum-
stances, the extent of skin supphed by the lateral cutaneous with sensibility
to prick is greater than that for fight touch arid the minor degrees of heat
and cold.

The full supply of the external saphenous, as far as we have been able to
determine it, consists of an ill-defined strip on the outer aspect of the foot.
The area supplied by this nerve merges at every point into parts innervated
by neighbouring branches. It is nowhere bounded by a well-defined border.
Over the outer aspect of the foot it merges into parts suppfied by the external
popliteal on the one side, by the posterior tibial on the other. Behind, as far
at any rate as sensation to prick is concerned, it overlaps the internal saphenous.
The method of residual sensibility confirms the opmion gained from dissection
that this nerve is only a temporary conjunction of fibres to complete the
supply of the outer side of the foot.

We require a case of division of the internal saphenous to complete our
knowledge of the full distribution of the posterior tibial. This nerve supj^lies
sensibility to light touch over the dorsal aspect of the toes, from the tip as far
down as the first interphalangeal joint, except in the little toe ; sensibility
to prick extends as far as the base of the toes. The distribution on the outer
side of the foot can be learnt only from a case where both external popliteal
and external saphenous have been divided, and no such case has yet come
under our notice.

We have been able so far only to show the way for future "research along
the fines that alone will reveal the full cutaneous distribution of the peripheral
nerves of the leg. By the method of residual sensibility we have mapped
out the whole of the distal portion of the internal saphenous and described
in part the boundaries of the external saphenous, the posterior tibial and the
lateral cutaneous branch of the external popliteal.

But, in order to complete our knowledge of the borders of these nerve
areas, it. will be necessary to obtain instances where the internal saphenous
nerve and the internal popliteal have been separately divided.

CHAPTER VIII

DEEP SENSIBILITY

If all the nerves svipplying a portion of the skin be divided, and at the
same time the muscular branches remain uninjured, that part will become
insensitive to aU forms of superficial stimulation, but remams sensitive to
pressure. As in the majority of our cases the injury was accidental, both
muscular and cutaneous fibres were divided together. But even these
accidental lesions, if compared the one with the other, can be made to
yield certain well-defined principles concerning the nature, capabihties and
distribution of deep sensibiUty.

In one case which came under our care (Case No. 47 ^) the radial and ex-
ternal cutaneous nerves had been divided by a transverse wound running
round the outer side of the forearm. The skin over the back of the thumb
and the radial half of the back of the hand were insensitive to light touch,
to prick, and to all forms of heat and cold. But over the whole of this area
pressure w^as at once appreciated. Even cotton wool, if rolled up tightly,
and particularly when applied suddenly and forcibly to the skin, caused a
definite sensation. Touch with the blunt head of a pin was locaUsed yviih.
remarkable accuracy, but our patient could not distinguish pressure with the
head from a prick with the point of a pin. Even when separated to 5 cm.
and applied transversely, the compasses were appreciated only as a single
" push " or focus of pressure. Any stimulus di'agged across the surface so
as to move the skin over underlying parts was at once appreciated. A piece
of cotton wool rolled up into a pledget applied to the skin with some force
produced a definite sensation. But if the skin was lifted the same method
of stimulation entirely failed to evoke any response, a proof that whatever
sensation had been previously present w^as due to the underlying structures.

Thus, if a part is deprived of aU its cutaneous nerves it becomes entirely
insensitive to light touch, to prick and to aU forms of temperature, but remains
sensitive to any stimulus which jars the skin, however lightly. The compass
points applied simultaneously are appreciated as a single impact, however
far apart they may be ; apphed successively they usually produce a sensation
of pressure in two 23laces, even when separated by a cUstance of only two
centimetres. These characteristics were even better seen in the case of one
of us [H. H.] in whom the same two nerves were divided experimentally at the

^ Eeported in full on p. 217.
137

138 STUDIES IN NEUROLOGY

elbow. In both instances, the accuracy and quickness with which even sHght
degrees of pressure were appreciated and locahsed came to us as an entirely
unexpected fact. Both H. H. and our patient J. S, (Case 47) could appre-
ciate and localise every stimulus commonly used as a test for light touch, and
all the surgeons who examined the former were certain that light touch
had not been destroyed by the operation. The touch of a finger, stimulation
with, the point of a pencil, a pen, or a tooth-pick, are tests for deep sensibiHty,
and can be appreciated even when all the nerves to the skin have been de-
stroyed. Even a touch with, a camel' s-hair brush evokes a sensation from
parts in this condition if the brush is thick and is applied vertically to the
plane of the skin.

So far the problem is simple and permits of a definite answer. Deep
sensibihty is' not materially affected by the destruction of all the nerves to the
skin, and it must reach the central nervous system by fibres that run in other
channels than the so-called sensory nerves.

But any attempt to discover by what means the deep parts receive this
innervation is hampered by the accidental nature of the lesions that come
under our observation, and by the complexity thus introduced into the experi-
mental conditions. For so long as the sensibility of the skin is unaffected,
it is impossible to investigate the sensation evoked by pressure. It is even
difficult to determine wdth certainty the condition of the sense of passive
position in the joints when superficial sensibility is perfect. The skin should
be totally insensitive to all stimuli before deep sensation can be satisfactorily
tested, a condition which greatly limits the possible opportunities of examina-
tion.

Since deep sensibility is not materially affected by complete destruction
of the nerves to the skin, its presence must depend upon the existence of
afferent fibres from one or more of the following structures — the muscles,
the tendons, the periosteum, the bones, and perhaps the arteries.

Complete division of the median nerve renders the palmar aspect of the
index and middle fingers, and occasionally part of the palm, totally insensitive
to all those forms of stimulation which appeal solelj^ to the nerves of the skin.
The only muscles to which this nerve supplies fibres below the wrist are the
opponens and abductor muscles of the thumb and the two radial lumbricales.
These structures lie in a part of the hand which does not usually become
insensitive to prick, to heat, and to cold in consequence of division of the
median nerve, and such an injurj^ occurring at the ^ATist should produce no
change in the deep sensibility of the fingers or the palm. The following
instance showed the correctness of this hypothesis.

Case 10. — Complete division of the median nerve ivith no loss of deep sensibility in the palm
or fingers. {Vide Table I., p. 90.)

Mrs. W. thrust her right hand through a window, completely dividing the n.echan nerve
at the wrist. At the subsequent operation the palmaris longus was found to be the only other
structure injured by the accident. All the tendons were intact, and the radial artery was not

INJURY TO THE PERIPHERAL NERVES 139

divided. The loss of sensibility to prick and to all forms of heat and cold was unusually
extensive, occupying a considerable portion of the radial half of the palm and the whole of the
palmar aspect of the thumb and of the index and middle fingers {vide fig. 7, J, p. 77). Over this
area, excei^ting over the tips of the fingers, pressure with the head of a pin or any blunt object
was appreciated and localised with surprising accuracy'. But she was unable to recognise the
difference between the point of a pin and pressure with the end of a cyUndrical rod 1 cm. in
diameter. Appreciation of jiassive movement at all the joints was perfect ; when the terminal
phalanx of either the index or middle finger was grasped laterally', and flexed or extended pas-
sively, she was able, though blindfold, to reproduce ■with accuracy in the corresponding finger
of the sound hand the i^osition into which the finger affected had been placed. The vibration
of a tuning-fork (C 128) was recognised perfectly everywhere over the affected area.

From these observations we may conclude that destruction of those fibres
of the median nerve, which run to the intrinsic muscles of the hand, makes
no material difference to the deep sensibility of the palm and of the two
proximal phalanges of the index and middle fingers. The deep structui'es in
the palm receive their nerve supply, for the most part, from the ulnar nerve,
and the flexor tendons or their sheaths must convey the afferent fibres of
deep sensibility to the palmar aspect of the index and middle fingers. The
tendons receive their nerve supply in the forearm, and if they are divided
at the wrist, any nerve fibres which pass along them to reach the fingers Avill
be destroyed. Division of the tendons to the index and middle fingers should
lead to loss of sensibility to pressure over the palmar aspect of these fingers,
provided that the skin has been rendered totally insensitive by simultaneous
destruction of the median nerve. Such a combination is not uncommon in
wounds of the wrist, and the follo^^dng instance shows that the result fulfils
the presupposed consequences of such an injury.

Case 7. — Division of the median nerve and of the tendons to the index and middle fingers. Loss
of deep sensibility over the palmar aspect of these fingers. {Vide Table I., p. 90, and fig. 7, a, p. 77.)

W. J. K. pushed his hand through a glass door, di^achng the median nerve and all the tendons
lying on the radial side of the wrist. At once he becair^e unable to flex the index and middle
fingers, and the whole of their jDalmar aspect became insensitive not only to prick, to heat and
to cold, but also to pressure. On their dorsal aspect pressure was everywhere appreciated, in
spite of the insensibihty of the two terminal phalanges to all skin stimuli. Pus formed around
one of the deep stitches by which the nerve had been united. This delayed the return of all
forms of skin sensibility to such an extent that eight months after suture the insensitive area
was almost as extensive as before the operation. But in this interval the j^atient had regained
the power of flexing the index and middle fingers; the long tendons had evidently united.
Pressure was now appreciated everywhere and locaUsed with accuracy over the palmar aspect
of the index and nriddle fiirgers. At this time the nrotor fibres of the median nerve had not
recovered, for the thumb could not be abducted or opposed, and the abductor and opponens
poUicis did not react to the interrupted current. Thus, the restoration of deep sensibiHty to
the index and middle fingers was probably due to fibres conducted by the flexor tendons, fibres
they had received somewhere in the forearm above the site of the injury.

AU the intrinsic structui^s in the palm of the hand are sujDplied by the
ulnar and median nerves ; ^ all the flexors to the fingers receive their nerve

^ Possibly also by perforating fibres from the radial.

140 STUDIES IN NEUROLOGY

supply in the forearm. If, therefore, it were possible to divide both nerves
at the wrist, without dividing the tendons, some sensibility to pressure should
still remain in the fingers and palm.

Such an isolated destruction of the median and ulnar nerves is extremely
unlikely to result from any ordinary accident, and no such instance has come
under our observation. For every injury, sufficiently severe to injure the two
great nerves at the wrist, divided at the same time some of the tendons in
their neighbourhood. We are, therefore, compelled to fall back upon a case
where, at the time of the injury, the tendons were united, but the divided
nerves were overlooked.

G. B. (Case 28, Table III., fig. 8, b, p. 79) cut his wrist on September 24, 1902. The wound
ran somewhat obliquely across the forearm from the ulnar to the rachal side, crossing the central
axis of the limb about 3-5 cm. above the fold of the wrist. The tendons were sutured and the
radial artery ligatured at once ; but no attention was paid to the chvided nerves. The wound
healed perfectly. Seven months later (April 16, 190.3) he came under our notice because of the
persistent loss of sensation. An exploratory operation revealed the following condition : The
median nerve was completely divided, and its lower end had been united to one of the super-
ficial tendons. The upper end of the ulnar nerve was bulbous and adherent to the tendon of the
flexor carpi ulnaris ; a thin strand of tissue ran from this bulb to the peripheral portion of the
chvided nerve. All the tendons had united firmly. Both nerves were therefore freshened, and
the ends joined with silk; the wound healed by first intention.

We were now face to face with almost exactly the conditions we desired. Both nerves were
completely divided, and any tendons that had been severed by the original cut had now united.
After this operation, rather more than one-half the palm on the ulnar side became totally anal-
gesic ; and yet, over the whole of this area, pressure was appreciated. Fuller observations were
made in August, when the general conchtion of the hand was more favourable for testing. The
extent of the palm insensitive to prick had diminished slightly, but was still of considerable
size. Within this area, pressure was appreciated and localised with remarkable accuracy. Two
compass points separated for a distance of 4 cm. were not discriminated when applied simulta-
neously, but if one point was allowed to touch the skin befoie the other, even by a fraction of
a second only, the patient knew that he had been touched in two places. On successive con-
tact he recognised the double touch without fail when the points were 2 cm. apart, and rarely
fell into error even when they were 1-5 cm. chstant from one another. The only part insensitive
to deep touch was the whole of the palmar and the greater jiart of the dorsal aspect of the
little finger, a loss of sensation which makes its appearance whenever the whole uhiar nerve
is divided.

Complete division of both nerves at the wrist does not destroy the deep
sensibihty of the palm. But if, in addition, the flexor tendons are divided,
pressure can be no longer appreciated over the area insensitive to prick.

Mrs. L. (Case 26, Table III., fig. 8, a, p. 79 ) fell with a jug in her hand, severing the median
and ulnar nerves and all the tendons on the anterior aspect of the wrist. Sensation to prick,
to heat and to cold was lost over a large part of the palm, and over the palmar aspect of all the
fingers. The whole of this area of the hand was insensitive to pressure. This comjjlete loss
of sensibility to pressure contrasts in a striking manner Avith its retention in the case described
above (No. 28), where the tendons were allowed to heal before any attempt was made to unite
the divided nerves.

INJURY TO THE PERIPHERAL NERVES 141

Division of the ulnar nerve produces results upon the sensibility of the
palm that are even more complex and difificult to unravel. This nerve supplies
in the forearm the flexor carpi ulnaris, the flexor profundus digitorum, and
almost certainly the tendons of the latter muscle inserted into the little and
ring fingers. In the palm it sends branches to all the intrinsic muscles of the
hand except the abductor, opponens, and outer head of flexor brevis pollicis,
and the two radial lumbricales. But division of the ulnar nerve renders totally
insensitive only a small part of the skin of the hand ; the field of observation
for deep sensibility is, therefore, restricted to the little finger and a strip on the
ulnar side of the palm in front and behind. Any sensation from the deep parts
in this region must pass through the ulnar nerve, whether it be due to fibres
running with the two tendons, or to those supplying the muscles and connec-
tive tissue of the palm, or to the innervation of the bones and joints of the little
finger. Complete division of the ulnar nerve at the elbow should therefore
produce the same re'sults as division of the nerve and tendons at the wrist.

In Case 19,^ the ulnar nerve, where it lay in the groove behind the internal
condyle, had become infiltrated with fibrous tissue in consequence of an old
injury to the elbow. The diseased portion was resected, and the two healthy
ends united. The total cutaneous insensibility which resulted was of consider-
able extent on both the dorsal and palmar surfaces of the hand (fig. 5, i, p. 71).
Over the whole of this area the patient was insensitive to pressure. He could
not appreciate the vibration of a tuning-fork over the whole of the little
finger, back and front, and was unable to tell into what position its phalanges
had been placed passively. Thus, division of the ulnar nerve at the elbow
had abolished the appreciation of pressure over the area totally insensitive
to cutaneous stimuli, and destroyed the sensibility of the bones, joints and
periosteum of the little finger. This patient was still able to produce some
movement of the little finger by means of the fiexor sublimis, but the tendon
of this muscle alone was unable to maintain even a trace of sensibility to
pressure in the httle finger.

In Case 83 ^ part of the ulnar nerve had been resected in the hope of curing
the neuralgia which had followed an incised wound at the wrist. The nerve
had been divided distal to the origin of its muscular branches in the forearm,
but above the point where the branch is given off to the back of the hand.
This operation abolished sensibility to pressure over the two terminal phalanges
of the little finger in front and behind ; the condition of the parts over the
palmar aspect of the basal phalanx was doubtful.

Here the conditions were simple ; the nerve lesion was known with cer-
tainty, and the clinical picture was not complicated by injury to other struc-
tures. It would seem from this case that division of the ulnar nerve, just
above the wrist, can render the two terminal phalanges of the little finger
msensitive to pressure, but does not necessarily abolish this form of sensibility
over the palm or dorsum of the hand.

1 Vide p. 207. 2 p. 208.

142

STUDIES IN NEUROLOGY

The flexor carpi ulnaris, the innermost tendon of the flexor sublimis and
the uhiar artery were divided in addition in Case 14, without adding to the area
insensitive to pressure ; it occupied the two terminal phalanges of the little
finger exactly as in the previous case. But in E. R. (Case 15, Table II., fig. 5,
G, p. 77), where the same structures were divided with the addition of the
palmaris longus, pressure was not appreciated over the whole little finger
and extreme ulnar border of the hand. It is possible that division of the
palmaris longus may have played an important part in the increased extent
of this loss ; but the innervation of the deep structures in the palm probably

varies considerably.

Whenever the nerve is divided, together with
a considerable number of tendons, the loss of
sensation to pressure tends to coincide with the
area of loss to all forms of cutaneous sensibihty.
The extent of the area of total cutaneous insensi-
bihty is always small, and the field available for
investigation is therefore restricted.

But if this cutaneous field of total insensibility
were increased from any cause, it would be possible
to examine more fully the extent of the loss of
sensation to pressure caused by division of the ulnar
nerve together with the flexor tendons of the wrist
and fingers. In the following instance, where the
median nerve was injured in addition to the above-
mentioned structures, we obtained an approximation
to these conditions. Sensibility to pressure was lost
over the back and front of the little and ring fingers
and over a considerable area on the palmar and
dorsal surfaces of the hand. Vibration of the
tuning-fork was not appreciated over the whole of
the front of the Uttle finger and over the two
terminal phalanges behind. The sense of passive position was lost in all
the interphalangeal joints of the little finger.

Case 60. — Division of the ulnar nerve, the tendons of the flexor carpi ulnaris and flexor sublimis
digitorum, together ivith injury to the median nerve.

M. G., aged 14, cut his left wrist with broken glass on November 13, 1904. The wound was
explored six hours later by one of us, and the uhiar nerve, together with all the tendons of the
flexor sublimis digitorum and the tendon of the flexor carpi uhiaris were seen to be divided.
The wound had partly divided the median nerve on its ulnar aspect. Both nerves were sutured
with catgut.

All cutaneous sensibility to touch, pain, heat and cold was abohshed over the area shown
in flg. 30, A.

He was unable to appreciate passive movements in the little and ring fingers. The \abration
of a tuning-fork (C 128) was not perceived when applied over that part of the little finger shaded
in fig. 30, B, whilst all sense of pressure was lost over the larger area enclosed within a dotted line.

Fig. 30.

A shows the extent of the
hand which became insensitive
to light touch, to prick, to heat,
and to cold in Case 60.

B, the deeply shaded area
corresponds to the parts e atirc'ly
insensitive to the vibrations of
a tuning-fork, and the dotted
lino encloses the extent of in-
sensibility to pressure produced
by the lesion in Case 60.

INJURY TO THE PERIPHERAL NERVES 143

All the intrinsic muscles of the hand were paralysed, and on November 23, lOOi, did not
react to the interrupted current.

On December 14, 1904, the abductor and opponens pollicis not only acted voluntarily, but
had regained their reaction to the interrupted current.

On February 1, 1905 (80 days after suture), sensibiHty to prick and to the extremes of tem-
perature had begun to return.

By March 8, 1905 (115 days after suture), he had regained sensibility to the vibration of the
tuning-fork over the little finger, and the area insensitive to pressure had begun to decrease in
extent. But all sense of passive movement was then absent from the little and ring fingers.

On April 5, 1905 (143 days after suture), the analgesia had been reduced to such an extent
that it was no longer possible to examine with pressure for the loss of deep sensibility. The
sense of passive movement was present in the metacarpo-phalangeal joints of both ring and little
fingers, but was still absent from the interphalangeal joints.

From this point the patient disapi^eared and could not be traced. It was, therefore, im-
possible to determine the date at which all forms of deep sensibility were restored.

We have been able to prove that complete destruction of all the sensory-
nerves to the sldn leaves the area they supply sensitive to pressure. This deep
sensibility is evoked by any stimulus that displaces the subcutaneous structures,
and when excessive, may cause pain. When heat and cold are applied over
an area of total cutaneous insensibility, they are not appreciated, and two
compass points cannot be discriminated even when separated widely, and
yet the patient still retains considerable power of localising the point at which
pressure is apphed.

This sensibility is due to afferent fibres which run with the motor nerves
and supply the muscles, tendons, fascia and joints. Even division of both
median and ulnar nerves at the wrist will produce little loss of deep sensibility,
unless the tendons be divided at the same time.

CHAPTER IX

SENSATIONS OF HEAT AND COLD

When one of the nerves of the hand is divided, it \\-ill be found that heat
and cold are no longer appreciated over those parts that are insensitive to
prick. But should the area of loss of Ught touch greatly exceed that of the
loss of sensation to prick, as is commonly the case, ice or water at 50° C. will
be found to produce a sensation of cold or of heat over the intermediate zone.
And yet this intermechate zone, though sensitive to the more extreme degrees
of temperature, has also suffered a change in sensibiUty; for water at 40° C,
warm to the normal hand, and water at 22° C, easily appreciated as cold,
there evoke no response.

Thus, division of a peripheral nerve causes loss of sensibiUty to light touch
and to temperatures between about 22° C. and 40° C. over a wide area of the
hand, and over a smaller area, loss to prick accompanied by complete insen-
sibihty to all degrees of temperature. Such are the conditions immediately
after a nerve has been di\aded.

During normal recovery we have shown that sensibility to prick is restored
over the whole hand before that to light touch shows even the slightest return ;
and it may thus come about that for a considerable period the whole of the
affected area of the hand remains insensitive to hght touch, but sensitive to
prick. This part of the hand has now reached a condition resembUng that of
the intermediate zone ; heat above. 50° C. and cold beloAv 20° C. are everywhere
appreciated, but the affected parts are insensitive to the milder degrees of
heat and cold.

By the time this condition has been reached, the hand is half-way towards
recovery, and it mil be well to trace, more in detail, the steps by which sensa-
tion has been so far restored. At first the area of complete analgesia corre-
sponded closely in extent with that of complete thermal anaesthesia. Any
want in exact correspondence is probably due to the greater intensity of the
stimulus produced by a prick. The area of total loss of sensation to prick,
to heat and to cold, is not sharply defined; it merges gradually into parts
sensitive to all these stimuli. As a prick is relatively the most urgent and
intense of these three forms of stimulation, parts of lowered sensibihty will
react to pain, although apparently entirely insensitive to heat and cold. Thus,
the extent of the total loss of sensation to prick not infrequently appears to
be somewhat less than that of the total loss to heat and cold.

144

INJURY TO THE PERIPHERAL NERVES 145

As soon as sensation to prick begins to return, step by step it is followed
by recovery of sensation to temperatures above 50° C. and below about 18° C.
Usually sensibility to heat lags somewhat behind that to cold and to prick.
This is due partly to blueness and coldness of the affected hand, and partly to
the comparative weakness of heat as a stimulus to parts of defective
sensibihty,^

But ultimately the hand becomes sensitive to prick, to cold (below 18° C),
and to heat (above 50° C.) over the whole area affected, either simultaneously
or within a comparatively short interval from the commencement of recovery.

Up to this point, the loss of sensation to light touch remains exactly as
on the first examination, and not infrequently weeks or months elapse before
it shows any sign of recovery. It is during this period that the affected area
gives the most constant abnormal reactions to heat and cold. For, although
the more extreme degrees of heat and cold are readily recognised, tempera-
tures between about 22° C. and 40° C. are not appreciated, and a test tube
containing water at 24° C. is not discriminated from one containing water
at 38° C.

It will be noticed that we have defined the more extreme forms of tem-
perature as above 50° C. and below 20° C, and from about 22° C. to 40° C.
have been called intermediate degrees. It will be shown in a subsequent
paper on the consequences of experimental division of two nerves in one of
us, that these limits can be defined more accurately when the patient is a
trained observer, capable of devoting the necessary time to examination.
But for clinical work we have selected these limits to avoid the confusion
introduced by the profound variations in sensibility due to external conditions
which cannot be avoided in practice. Fatigue and cachexia cause the affected
part of the hand to become blue and cold. When in this condition, it is
much less sensitive to all forms of temperature stimulation, more particularly
to heat and to the minor degrees of both heat and cold. Of all external
influences producing this state, the weather is the most powerful. Extreme
external cold will render the hand blue and insensitive ; but the actual external
temperature registered by the thermometer is not the sole factor in this change.
What is usually called a " raw " day, misty, damp, and cold, is more destructive
of sensibility than one of the same temperature, but bright and sunny.

A hand that has reached the end of the first stage of recovery, sensitive
to prick and to the more extreme degrees of temperature, is influenced ]3hysically
to a greater extent than normal parts when warmed and cooled. Placed in
hot water the affected half becomes warmer than the normal parts of the
palm. Conversely, when cooled with ice-water, the parts that have reached
the end of the first stage of recovery may become colder than normal.

If the external temperature is low and the affected parts of the hand are
blue, it may be necessary to lower the temperature of the test tube to 18° C.

^ A third cause, the relatively small number of heat-siiots, is considered fully in a further
communication by Dr. Rivers and one of us.

VOL. I. L

146 STUDIES IN NEUROLOGY

before parts that have recovered sensibihty to prick react, and the patient
appreciates the cold stimulus. In Uke manner even 50° C. may scarcely be
ajDpreciated as heat. Conversely on a warm summer day when the colour
of the parts affected cannot be distinguished from that of the normal hand
even 24° C. may be called cold and 40° C. hot. Such acuity of perception is
rare even under the most favourable external conditions.

In such a case, supposing a patient can appreciate 24° C, there is no gap
in his sensation at the cold end of the scale ; for on the normal skin any tem-
perature above this point is usually said to be neutral, neither hot nor cold.
But whether the highest point appreciated be 18° C. or 24° C, the sensation
of cold, produced over parts which have become sensitive to prick but not
to light touch, is profoundly abnormal. It is diffuse and radiates widely to
a distance from the point stimulated. It may even seem colder than over
normal parts, and in addition possesses a " tingUng " quality which is very
characteristic. By this we know that although sensation is produced over
the full range usually associated with cold, yet that sensation is abnormal.
It differs from that produced by 24° C. over normal parts in its diffuseness
and wide radiation. Moreover, it shares these abnormal quaUties with the
sensation to cold present over the intermediate zone and over the hand which
reacts to no cold stimulus higher than 18° C.

At the other end of the scale there is always an obvious loss of sensation,
however perfect the external conditions may be. For 40° C. is the lowest
warm stimulus to which any of our patients reacted over parts in the state
under discussion. Yet on the normal sldn 34° C. is frequently said to be warm,
and 36° C. distinctly hot. Thus, in these cases sensation to heat is absent
and not simply defective over a certain range of temperature, however favour-
able the external conditions. But here also, as with sensibility to cold, even
if 40° C. can be appreciated, the sensation produced radiates widely from the
point stimulated. It is " tingling " and diffuse.

In this condition the hand remains for a variable period sensitive to prick
and to the more extreme degrees of temperature, but insensitive to light touch
and the intermediate grades of heat and cold. With the first signs of returning
sensibility to light touch, temperatures of 22° C. and 38° C. begin to be appre-
ciated with certainty as cool and warm. If the patient is intelligent he states
that the radiation and diffusion, so intrusive over parts still in the earUer
stage of recovery, is no longer noticeable.

Among fourteen cases, where one or more nerves to the hand had been
completely divided, sensibility to Ught touch and to the intermediate degrees
of temperature was restored simultaneously in twelve. No. 18 (Table II.
and fig. 5, a) became sensitive to warmth over the proximal parts of the
affected area nearly three months before any response could be obtained to
cotton -wool. But simultaneously with this reaction to warmth, he became
sensitive to the interrupted current, produced without iron in the circuit,
to which it had been previously insensitive. In one instance only (No. 3,

INJURY TO THE PERIPHERAL NERVES 147

Table I., fig. 5, e) was stiinulation with cotton wool appreciated before the
restoration of sensibility to warmth, and in this case the interval between the
return of the two forms of sensation was not more than one month.

The following are the results to which we have arrived in this section : —

(1) Immediately after a peripheral nerve has been divided, all sensibiUty
to heat and cold is lost over the area insensitive to prick. The intermediate
zone between the borders of the loss of sensation to hght touch and the area
of total insensibility to prick remains sensitive to temperatures above 50° C.
and below 18° C, but is insensitive to any temperature between about 22° C.
and 40° C.

(2) Sensibility to the extremes of heat and cold usually returns step by
step with that to prick. At last, a stage is reached on the road to recovery,
when all the parts affected are sensitive to temperatures below 18° C. and
above 50° C. But the sensation caused by these temperatures is of a different
character from that they produce over the normal skin. It radiates widely
and is accompanied by an abnormal tingling.

(3) After the hand has remained for a variable period in this condition
of sensibility, the intermediate degrees of temperature between about 22° C.
and 40° C. begin to be again appreciated. This return usually coincides with
that of sensation to light touch, but may precede it by a short period under
favourable conditions.

CHAPTER X

THE COMPASS TEST

Discrimination of two points separated from one another for a varying
distance is one of the oldest tests for sensation. But it has fallen into disuse
as a means of cHnical investigation in consequence of the difficulties with
which it is surrounded, and the incomprehensible results yielded by the test
when carried out in the usual manner. To McDougall (72) we owe a modifica-
tion which not only makes it easy to use the two points as a test for sensation
even in hospital patients, but gives to the records a definiteness otherwise
lacking. The blunt points of a pair of compasses are separated from one
another for a measured distance. The skin of the affected part is touched,
and the patient, whose eyes are covered, is asked to say after each applica-
tion whether he Avas touched by one or two points. When they are separated
for less than a certain distance, varying with the different parts of the body,
the points no longer appear as two on the normal skin. Under the old method
the patient was also touched a few times with one point as a test of his trust-
worthiness. But in all our observations the patient was touched ten times
with one point and ten times with two points, each form of stimulation being
apf)lied entirely at random in the series. This modification of the original
method adds considerably to the value of the compass test ; for we now
pay attention not only to the number of times two points are mistaken for
one, but also lay stress upon the frequency A^dth which stimulation with
one point is said to be two. The results are recorded graphically in the
following manner : Every time the patient's answer is correct a stroke is
made, above a horizontal line if he was touched with one point, below it if
he was touched M-ith two points. An incorrect answer is recorded by a cross.
Thus, if he answers " one " when touched with two points, a cross is placed
below the Une ; if one point has been called two, the cross is drawn above the
line. A preceding stimulus frequently has an effect upon those which follow
it, and to register the order in which "the stimuli have been appHed is therefore
an additional aid to the interpretation of the records. Thus, if the testing
began with four double touches correctly answered, four strokes would be
ranged below the line from left to right. At the point above the line directly
over the last of these double touches would begin the record of the subsequent
single stimuli. In this way, the results of all fm-ther stimuli are recorded
until the number is complete. As ten stimuU of each kind are used, the results

148

INJURY TO THE PERIPHERAL NERVES 149

can be reduced to percentages at once. For additional accuracy we use the
letter " D "' whenever the patient is in doubt, and " O " whenever he fails to
answer at all.

Perfect appreciation of the compass points at a distance of 2 cm. would
be represented thus : —

1 I 111 11 mil

2 cm.

2 I 1111 111 111

If, however, the patient is unable to differentiate the two points at this dis-
tance, answering " one " to every stimulation, the record would stand :-^

o 1 I nil 11 1111

z cm — ■

- ^"^- 2 I XX XXX X XXXX

Such a formula would show that when 2 cm. apart, the sensation produced

by two points is well below the threshold at which discrimination becomes

possible. Less complete failure would be represented by some such formula

as : —

1 I IIXX IX ixxi

2 cm.

2 I XIX IIXX XXl

where 50 per cent, of the answers are wrong with one point, 60 per cent, with
two points. A curious phenomenon, upon which we shall lay considerable
stress, is the tendency to appreciate one point as two over parts of defective
sensibihty as soon as the Hmits of accurate discrimination are passed.

In every case our observations were controlled by testing a similar part
of the sound hand. We found that almost without exception two points could
be accurately discriminated over any part of the normal palm when separated
for 1 cm. and applied transversely.

The compasses may be apphed either transversely or along the vertical
axis of the hmb. We have been content in this particular research with a trans-
verse position which allows of accurate discrimination at a smaller distance
than when the two points are placed in the axis of the Hmb. But where the
area to be examined consists of a long and narrow strip upon the palm, we
have also made use of the longitudinal position controUing our observations
by an examination of a similar portion of the normal hand.

The conclusions detailed in this section are 'founded upon the results of
340 sittings, with fifty-eight patients, conducted according to the method we
have just described.

Immediately after division of a nerve trunk, a part of the hand becomes
totally insensitive. Over such parts, all sensation is abolished, and the com-
pass test is, therefore, inapplicable. But the extent of loss to light touch
usually exceeds considerably the analgesic area. This intermediate zone is
frequently of sufficient size to make the compass test possible, especially when
the loss of sensation has been produced by division of the median nerve. After
division of this nerve, nine patients failed to distinguish the two points when
they were separated for 2 cm., and three failed at a distance of 3 cm. This

150 STUDIES IN NEUROLOGY

number would probably have been greater, had it been possible to apply the
compasses at this distance more frequently. Limitation of the field to be
examined compelled us to choose some distance such as 2 cm. obviously far
above the threshold of sensibihty of the normal skin ; we then based our
judgment on the gradual improvement sho\^Ti by the formula obtained at this
distance. Had the area at our disposal been larger, we should have depended
rather on a gradual decrease of the distance between the points required for
accurate discrimination. In every case where the median nerve was known to
have been severed, the patient gave more than 50 per cent, of mistaken answers
when touched simultaneously with two points separated to a distance of 2 cm.
When the ulnar has been divided, the small extent of the intermediate
zone makes it, in many cases, impossible to apply the test with the points
at this distance. But in all five instances where such a test was possible,
owing to the relatively large extent of the intermediate zone, the patient
totally failed to discriminate between the two points at 2 cm. In two instances
we were able to use them 3 cm. apart and, even at this distance, the answers
were uniformly wrong whenever the two points were applied simultaneously.
In consequence of the comparatively small area insensitive to prick, the
extent of the palm suitable for this test becomes larger where the ulnar has
been divided on the distal side of its dorsal branch. Yet every patient with
this form of injury failed to distinguish the points at 2 cm., and in one instance,
where an unusual extent of the palm was affected, they could not be dis-
criminated even when 4 cm. apart.

Return of sensibihty to prick and to the more extreme degrees of heat
and cold, in no way improves the power of distinguishing a pair of compass
points. The whole of the affected parts of the hand may become sensitive to
such stimuli, and the patient may experience more than usual discomfort
when pricked; yet even when separated for 3 cm. he may entirely fail to
perceive that he is touched by more than one point.

Over the intermediate zone it was only possible to use the points at a
distance less than 2 cm. from one another. After the hand has become acutely
sensitive to prick two points, at this distance apphed to parts that had once
formed the intermediate zone, yielded a formula in no way superior to that
originally obtained. Evidently the retm-n of this form of sensibihty makes
no cUfference to the acuity of the patient towards the compass test. It is
frequently impossible to make use of the compasses until sensibihty to prick
has returned, in consequence of the smalhiess of the intermediate zone. Yet,
although it may not have been possible to test the hand until it has become
partly sensitive, the record of the compasses at 2 cm, is mostly so bad (Ui^^^)
that return of sensation to prick cannot have improved materially the power
of distinguishing two points.

Nowhere can this be shoA\^i in a more striking manner than after division
of the median and ulnar nerves ; at first the palm may be totally insensitive,
and compasses cannot be used. Gradually sensibihty to prick returns, the

INJURY TO THE PERIPHERAL NERVES 151

whole palm becomes available for testing, and it is found that two points
sef)arated to a distance of 5 or even 6 cm. cannot be discriminated. Thus
nine months after suture of the two nerves, Mrs. L. (Case 26, Table III.) was
unable to distinguish two points at 5 cm. (5 cm. ^.j^g^;) ; three months later the
same parts gave a perfect formula at 1 cm. In the same way seven out of ten
of the answers made by B. (Case 28, Table III.) at 6 cm., after the whole palm
had become sensitive to prick were erroneous (6 cm. 111^1*^^). But six months
later, with the points at one-third of this distance apart (2 cm.) an identical
formula (2 cm. ^ ^ '° "■ ) was registered over the same area.

Immediately light touch begins to be appreciated over the area affected
the compass records respond to the change. At first, sensation becomes
uncertain over parts in the neighbourhood of the wrist. A few weeks later
light touch can be certainly appreciated over the proximal part of the distribu-
tion of the injured nerve, although the distal parts of the palm still remain
insensitive. A hand in this condition reveals clearly the close connection
between sensibiHty to light touch and the discrimination of the compass points ;
near the ^vrist seven out of ten answers may be right, while over more distal
parts of the palm all ten may be incorrect.

Ultimately the whole of the hand becomes sensitive to light touch ; but,
although the formula shows obvious improvement and the distance between
the points can be greatly decreased, sensibiHty to this test still remains defective.
This is the stage associated with a " line of change." A pin drawn hghtly
across the skin from normal to abnormal j)arts produces a changed sensation
as soon as the boundary of the original loss of light touch is passed. The
sensation produced becomes more uncomfortable and has a curious tingling
which even patients of the meanest intelligence cannot mistake. So long as
the hand is in this condition the discrimination of the compass points remains
defective, and it would seem that the existence of this state depends on a
defect in that form of sensibiHty which gives precision to the appreciation of
two points.

At last sensation may be so completely re-established that the compasses
reveal no material cHfference between the two hands. But so perfect a
restoration requires several years, and long before it was reached most patients
considered the hand was as good as ever. They ceased to come at our request,
or failed to let us know a change of address. A few remained faithful to the
end. Amongst them one j)atient with a divided ulnar (No. 18, Table II.) gave
a perfect formula at 1 cm. exactly two years after the accident, and one with
a divided median (No. 4, Table I.) reached the same condition two years
and nine months after suture of the nerve.

If anything has happened to retard recovery, if the wound has suppurated
or the ends of the divided nerve have not been brought into apposition, com-
passes may reveal a permanent defect, although the hand has become sensitive
to all forms of stimulation. We have seen an old man who accidentally divided
his ulnar nerve in 1843. To all forms of touch, to prick and to temperature,

152 STUDIES IN NEUROLOGY

sensation had returned. But over the whole distribution of the uhiar nerve
sensation was changed, the pin point became sharper, and cotton wool caused
a tingling sensation ; compasses were defective over the whole ulnar palm
(1 cm. ^\9R.iw.\

^ 2 I 3 K.7 w.'

One of our students divided the median nerve of his right hand. When
we saw him six years later he responded to all forms of stimulation, but his
sensibility to compasses was comparatively low. On the palm of the sound
hand he was accurate at 0'5 cm. ; on the mechan area of the injured hand he
failed with both one and two points at TS cm. (TS cm. ,^J^^ *^). At the
same time he showed an exquisite line of change. In fact, we can state with
certainty, that so long as this hne of change still remains, the compass points
will show that sensation is still below the normal.

When a nerve trunk is injured, but not completely divided, the loss of
sensation depends on the gravity of the injury. All forms of sensation may
suffer so severely that to all appearances the nerve has been completely severed.
But within a month or six weeks sensation to prick may begin to return,
and with it the extent of the anaesthesia to light tovich and to minor degrees
of heat and cold diminishes. This simultaneous return of the two forms of
sensibility is a certain indication that the nerve has not been severed, however
grave the injury may have been. It is, therefore, of extreme importance to
determine with certainty whether sensibiUty to light touch is returning or
not. Cotton wool is often an untrustworthy stimulus. But the compass
points show at once if the loss to light toucli has begun to diminish in intensity
or extent. For it has been shown that return of sensibiHty to prick in no
way improves the power to appreciate two points ; any coincident improve-
ment in sensation shown by the compass test must, therefore, signify a simul-
taneous improvement in forms of sensibility other than those grouped around
sensation to prick. As a matter of fact it will be found, that whenever the
compass records show considerable improvement, the parts which have so
improved have become sensitive to minor degrees of heat.

Case 29, Table IV., p. 100,^ is an excellent instance of this condition. A young man cut his
wrist whilst loading some bottles upon a van. The loss of sensation produced by the injury
corresponded to that wliich would follow complete division of the median nerve; even the palm
was in part insensitive to prick and to the extremes of heat and cold. But exploration of the
wound by one of us showed that the nerve was injured without destruction of its continuity.
Within a month of the injury sensibility to prick had improved greatly; at the same time we
suspected that the parts in the neighbourhood of the thenar eminence were sensitive to cotton
wool. This suspicion was confirmed by the character of the records yielded by the compasses
from the palm in the neighbourhood of the thumb and at the base of the index and middle fingers.

Palm at base of thumb, 1 cm. V,^,^-] Z.

Palm at base of fingers, 1 cm. Jv4443'.

^ ' 2 I 4 K. 6 W-

It will be seen that, although the same number of wrong answers were given in both places
with two points, the single point was rightly appreciated nine times out of ten over a part where

1 Vide p. 203.

INJURY TO THE PERIPHERAL NERVES 153

sensation to touch had more distinctly returned, whilst three only out of ten answers were correct
over the remainder of the palm. This was no fortuitous difference, for in a month's time the
com23asses were perfect at 1 cm. over the neighbourhood of the thumb, though still defective over
the remainder of the palm (1 cm. ^IgRiw)'

Not infrequently, the pressure of a tight bandage or badly adjusted splint
causes a diminution of sensibility to light touch amounting even to complete
insensibility to cotton wool. Such loss is accompanied by a profound altera-
tion in the power of appreciating two points, and even if light touch, tested
with cotton wool, is present, the compasses reveal the diminution in sensibiUty
with unmistakable distinctness.

Case 61. — Diminution in sensibility to cotton ivool and to the compass test, produced by pressure
on the ulnar nerve at the elbow.

A youth, who was thought to have fractured his clavicle, was strapped by Sayre's method.
The little finger became painful during the time the strapping was in position, and later the ulnar
half of the hand became numb. When we saw him three months after the accident the muscles
of the hand were acting, and contracted normally to the interrupted and to the constant current.
Over the whole ulnar area sensation was lowered to cotton wool, and over the parts where fight
touch was diminished a prick produced a more intense and diffuse pain than over the normal
hand. Water at 25° C. and at 35° C. was everywhere appreciated. At a distance of 1 cm. two
points were not discriminated eight times out of ten (1 cm. olaR gw )• ^^^ *^° months later
light touch had everywhere returned and the record of the compasses at 1 cm. was perfect.

By means of the compasses it is possible to obtain information concerning
the relative sensibihty of parts which react to all the coarser tests. If the
hand is sensitive to all grades of temperature that can be used in practice,
and if cotton wool is appreciated over the whole extent supplied by the injured
nerve, it would be impossible without the aid of the compasses to say that
one part of this area was more advanced towards recovery than another. But
the record of the two points will show that the proximal portion of the palm
is more sensitive than that nearer the base of the fingers.

The following case (No. 34, Table V., p. 102^) is a good example of the
manner in which improvement of sensation can be measured after the hand
has become sensitive to all the ordinary stimuli.

A man of 48 years of age cut his left wrist on March 4, 1903. Under an anaesthetic the wound
was explored, and several divided tendons were sutured ; the ulnar nerve was foimd to be injured,
but not completely divided below the point at which the dorsal branch was given off. This
injury caused loss of sensibility to prick over the palmar aspect of the little finger, and ansesthesia
to light touch over the ulnar half of the ring finger, the palmar aspect of the fittle finger and the
whole ulnar palm. Over tliis area intermecfiate degrees of temperature were not appreciated.
The interosseous muscles of the second, third and fourth spaces, and the abductor mimmi digiti,
were inactive and ceased to respond to the interrujited current. Rapid improvement took
place; sensibifity to prick began to return, followed qmckly by that to light touch. By
August 26, 1903, twenty-five weeks after the accident, the hand had become sensitive to all forms
of stimulation ; but light touch was badly appreciated, and the compasses gave a defective record

Vide p. 209.

154 STUDIES IN NEUROLOGY

at 2 cm. The affected parts improved, until just a year after the accident (February 28, 1904)
all parts of the palm appeared to be equally sensitive to all forms of stimulation. But over that
part nearer to the wrist the compass points gave a record at 1 cm., which showed that the thres-
hold had been approached (1 cm. 2|6r 4w-)- Nearer to the base of the fingers the two points were
wrongly appreciated in every instance (1 cm. ^1^°^ ). This difference proved that sensibihty
was steadily returning from the more central to the more peripheral j)arts of the affected area.
On September 25, 1904, eighteen months after the injury, sensation was still changed over the
ulnar area ; the i:)oint of a jjin caused more discomfort, and this increased reaction began at the
old line of anaesthesia to light touch. Over the proximal jjarts of the palm at 1 cm. the compasses
yielded a somewhat improved record (1 cm. 2 1 7 b° f w ^' ^^ore chstal portions stiU showed ten
false answers with the two points (1 cm. |jy^).

All the higher forms of sensibility are pecuUarly susceptible to the influence
of bodily states. We have dwelt upon the way in which recovery may appear
to be arrested in consequence of cold or unpropitious weather. But the
records yielded by compasses are also influenced by other conditions, such
as mental fatigue and particularly alcohol.

By the method we have adopted, an erroneous appreciation of one point
is registered equally with the misapprehension of two. And among the
formulae cited to support our contentions in this chapter, the reader will have
been struck with the frequency of mistakes in the upper row of symbols. By
most clinical observers such errors are supposed to show that the patient is
untrustworthy ; but experimental psychologists have long recognised that
this doubling of a single stimulus is a phenomenon closely associated with an
approach to the threshold of sensation. If the compasses are separated for
a distance too small for just appreciation, every stimulus, whether by one or
two points, is frankly called one. But, if the distance is increased, some
stimuU with two points will be called " one," some with one wiU be called
" tw^o." Occasionally every touch with a single point appears to be double,
although every touch with two points is correctly appreciated. Such a com-
plete reversal never occurs in our experience with hospital patients, except
over parts where the sensibihty has been lowered by a definite nerve injury.
For however careless, stupid, or alcohohc may have been the subject of our
examination, we never observed an unbroken series of doubled single touches
amongst the control tests we always apphed to the uninjured hand.

Case 5 (Table I. and fig. 7, l.). — Oradiuil recovery of sensibility to the compass test after suture
of the median nerve.

On October 2, 1902, a butcher cut his wrist with a knife. Two days later sensation was
lost over the area shown in fig. 3, l. The space between the border of the loss to prick and that
to light touch was sufficient to permit of the compass points being applied at a distance of 2 cm.
apart, and the records were as follows : —

October 4, 1902, 2 cm. |Li^., 1 cm. l\^-,

At the operation on October 4 the median nerve was sutured, and sensibility to prick began
to return in the usual way. Thirty-three weeks later (May 24, 1903) light touch appeared to be
ost over the whole median area, but the compasses showed slight improvement over the jjalm.

INJURY TO THE PERIPHERAL NERVES 155

May 24, 1903, 2 cm. |f^^, 1 cm. WUtZ'-

By September 23, 1903, light touch was no longer lost over the palm, and the compass records
showed material improvement.

September 27, 1903, 2 cm. ^^-^^J ^J/, 1 cm. '-j^^o^-

On November 25, 1903, all forms of sensation were appreciated, but a well-defined change
occurred at a line corresponding to the border of the previous anaesthesia to light touch. The com-
passes showed still further improvement in that the record at 2 cm. was now perfect (2 cm. y,^^.) •
At a distance of 1 cm. every stimulation with a single point was called " two," the phenomenon
of " double ones " in a perfect form.

2 cm.

Oct. 4. May 24. Sept. 27.

1 I 10 R 1 I 7 R. 3 W. 1 I 9 R. 1 W.

2 i 4 R. 6 W. 2 1 10 R. 2 I 9 R. 1 W.

Nov. 25.
1 1 10 R.

2
1 1

1 10 R.
10 W.

1 I 10 R. 1 I 6 R. 4 W. 1 I 4 R. 6 W. - , -- ..-

1 cm. 2 I 10 W. 2 I 8 R. 2 W. 2 I 10 R. 2 | 10 R.

The above table shows clearly that recovery of sensibihty is accompanied,
not only by an increased appreciation of two points, but also by a simultaneous
uncertainty in the sensation produced by single stimuli. At any one distance,
such as 2 cm., the power of discrimmation gradually increases until at last
the record of both one and two points may become free from error.

But, in the above instance, when the points were 1 cm. apart every single
stimulus was thought to be double, though every double stimulation was
rightly appreciated. The serial arrangement of the records at this distance
shows the gradual evolution of this phenomenon.

CHAPTER XI

SENSIBILITY OF THE HAIRS

Whilst watching the recovery of sensation after division of the uhiar
nerve in one of our patients of unusual intelUgence, we were astonished at
the rapidity with which the back of the hand became sensitive to cotton
wool. We imagined that this was an individual peculiarity, until he gave us
the clue, that led us back to a reconsideration of the sensibihty of the hairs.
When we stimulated with cotton wool that part of the dorsal surface of the
hand supplied by the ulnar nerve, he told us that the sensation radiated widely
over the parts affected, and possessed a tnigling character foreign to the
sensation produced by stimulating normal parts of the hand. Now radiation
and a tingUng quaUty had come to be associated in our minds mth that form
of sensibihty which returns early to the affected hand; pain, cold and heat,
in as far as they are appreciated by a hand in the first stage of recovery, all
produce sensation with this pecuharity. It seemed, then, that on the dorsal
surface of the hand some structure had become sensitive to cotton wool at
about the time when sensibility to prick was fully established. Such a structure
is to be found in the hairs which are never absent from the back of the hand
of men, and are present even on the hands of most women.

Case 15 {vide Table II., p. 92 and fig. 5, g, p. 71). — Complete division of the ulnar nerve at the
point where its dorsal branch is given off. Presence of sensation to cotton wool due to the innervation
of the hairs before the return to the hairless skin of sensibility to light touch.

A lighterman, aged 29, was admitted to the Poplar Hospital on July 29, 1903, with a cut across
his left wrist. He had lost sensation over the full ulnar area shown in fig. 5, G, p. 71. The woimd
was explored and the ulnar nerve was seen to be divided at the point where it gave off its dorsal
branch. The upper end, a single trunk, was sutured to the two branches which constituted the
peripheral portion of the nerve. All the muscles in the hand supjilied by the ulnar nerve were
completely paralysed and ultimately lost their reaction to the interrupted current. The wound
suppurated and did not heal for seven weeks.

On December 2, 1903, sensibility to jsrick and to ice had returned over the palm, but was
absent over the same area as before on the dorsal surface of the hand, which chd not become
sensitive to these stimuli imtil March 23, 1904 (237 days after suture).

By Jime 12, 1904 (320 days after suture), the whole of the dorsal surface of the hand not only
reacted to prick and to ice, but had become sensitive to stimulation with cotton wool. But
when that part of the hand supplied by the dorsal branch of the ulnar nerve was shaved, it became
at once entirely insensitive to any form of light touch. This experiment was repeated many
times under varjdng conditions, for it was not until April 9, 1905 (619 days after suture), that
this portion of the hand became sensitive to cotton wool, when shaved.

156

INJURY TO THE PERIPHERAL NERVES 157

From the beginning, this i)atient recognised that the sensation caused by cotton wool over
the normal parts of the back of the hand was different from that over the affected area. He
said : " When you touch the back of my hand (over the ulnar border) it is a kind of crawling,
prickly feeling." Later, he learnt to associate this peculiar sensation so definitely with hairs,
that he could tell us if after shaving we had left any still standing above the surface. This ex-
planation received additional support from the fact that sensibility to warmth (below 40° C.)
and to the painless interrupted current was absent over the area on the dorsal surface of the hand,
which exhibited this radiating and abnormal sensibility to cotton wool.

A similar condition appeared in H. H. during the recovery of the radial
half of the back of the hand after experimental division of the radial (ramus
superficialis nervi radialis) and external cutaneous nerves in the neighbourhood
of the elbow. Within eight months of the operation, this part of the back of
the hand had become sensitive to prick, to ice, and to water at 50° C. With
this return of sensibility, the hairs began to react to cotton wool, and this
stimulus evoked a curious radiating sensation with a characteristic tingling
quality. True localisation was impossible, and the skin over the same parts
became, when shaved, entirely insensitive to cotton wool.

In both these instances recovery was considerably delayed. The wound in
the first suppurated badly ; in the second case the nerves had been divided at
the elbow, and the period between the return of sensibility to prick and that
of the recovery of light touch was consequently longer than usual. This return
to the hairs of a peculiar form of sensibility characterised by wide radiation
seems to occur when the sensation to prick, to ice, and to water at 50° C. has
been present alone over the affected parts sufficiently long to be fully restored.

It would seem, then, that return of sensibility to prick and to the more,
extreme degrees of heat and cold brings a return of sensation to the hairs on
the back of the hand. They then react not with that well-locahsed sensation
we are accustomed to associate with stimulation of hairs, but with a widespread
tingling, analogous to the radiating sensation j)roduced by a prick or by cold
water at the same stage of recovery.

Sensibility is gradually restored, and the back of the hand becomes sensitive
to cotton wool even when shaved. As sensation becomes more perfect the
tingling quality disappears, the stimulus can be localised correctly, and the
hairs regain their normal sensibility.

We have shown that, under certain conditions, the hairs may regain a
pecuhar form of sensibihty at the time when the affected parts are sensitive
only to prick and to the extremes of heat and cold.

Plucking a normal hair will, in most cases, cause pain, and it is this sensibility
to pain that returns to the hairs when they react in this manner to stimulation
with cotton wool.

But it is obvious that stimulation of normal hairs produces a well-defined
and well-localised sensation differing entirely from the radiation and tingling
so characteristic of all sensation at the close of the first stage of recovery. The
hairs must, therefore, be endowed with some additional innervation other than
that which may be restored with the return of sensibility to prick.

158 STUDIES IN NEUROLOGY

If it were possible to examine a part sensitive to light touch only, the signifi-
cance of this innervation would become manifest. We have fortunately been
able to examine five cases where sensibility to cotton wool was present over
parts insensitive to prick and to the extremes of heat and cold. Here the hairs
were in a sensory condition, complementary to that described in the first part
of this chapter.

The first instance (Case 85) ^ of this remarkable condition occurred in a
plumber who divided the median together with the radial and part of the
external cutaneous nerve in the neighbourhood of the wrist. Over the back of
the hand in the region of the first interosseous space was a small area entirely
insensitive to prick and to the extremes of heat and cold. But over this patch
of sldn he was sensitive to stimulation with cotton-wool, or to any other stimulus
which affected the hairs. Here he also correctly appreciated the difference
between water at 25° C. and 38° C.

Fig. 31.

To show the extent of the loss of sensation produced by division of the internal branch of the radial
and posterior branch of the external cutaneous nerves in Case 62.

The dotted area was insensitive to all forms of cutaneous stimulation. Within the area enclosed
by a thick black line the hairs were sensitive, but all sensation of pain, heat, and cold, was absent.

This was almost exactly the condition of the triangular patch of dissociated
sensation which appeared in H. H. after experimental division of the radial
(ramus superficiahs nervi radiaUs) and external cutaneous nerves at the elbow.

This power of appreciating the movement of hairs, and of locahsing the point
at which the stimulus is applied, can be present although the skin is insensitive
to all forms of temperature, and even when, after shaving, it becomes entirely
anaesthetic, as shoAvn by the following instance.

Case 62. — Division of the internal branch of the radial nerve {ramus dorsalis nervi radialis super-
ficialis), with the posterior branch of the external cutaneous at the wrist, producing an area of dissociated
sensibility.

W. C, aged 21, cut his right wrist with glass on May 18, 1905. The same evening the internal
branch of the radial nerve and the tendon of the supinator longus were sutured.

On May 24 we found that he was insensitive to prick over the radial half of the dorsum of the
hand (fig. 31). Sensation was unaltered over the thumb and fingers. The whole of this area was
insensitive to all degrees of temperature, but he responded briskly to pressure or any form of
deep touch.

Stimulation with cotton wool was not appreciated over a considerable portion of this area.
But over a strip towards its ulnar side, about 4-5 cm. in length and from 1-2 to 1-5 cm. in breadth,

1 Vide p. 218.

INJURY TO THE PERIPHERAL NERVES 159

cot ton -wool iirocluced a tickling sensation. Over the normal parts lilucking a hair caused him to
say that he was being pricked ; but within the area of dissociated sensation he said : " You are
touching me, you tickle me." Over the area insensitive to all cutaneous stimuli but sensitive to
deep touch, he failed entirely to appreciate a jjuU sufficiently severe to lead to the removal of
the hair.

The sensation produced by cotton wool within this area of dissociated sensibility was a well-
locahsed tickhng, entirely different from the radiating tingUng sensation described in the first half
of this chapter.

He failed in every case to discriminate two points of the compasses at 4 cm., applied longitudin-
ally over this area; over a similar part of the sound hand the test gave a perfect result at 2-5 cm.

After completing these observations the back of the hand was shaved. The whole of the parts
insensitive to prick and to temperature were then found to be entirely anaesthetic to cotton wool,
proving that the sensibility previously existing must have been due to the hairs. Over normal
parts of the back of the hand when shaved cotton wool could be accurately appreciated.

Thus, in conclusion, we believe that the hairs receive a double innervation.
When all cutaneous nerves are divided and deep sensibility alone remains a
hair can be plucked out without producing any sensation. But as soon as the
hand has become fully sensitive to prick and to the extremes of heat and cold,
pulUng the hairs produces pain, and stimulation with cotton wool evokes a
peculiar radiating, tingling sensation. Later, when the hand has regained
sensibility to hght touch, this tingling quality disappears, giving place to the
well-locahsed sensation produced when normal hairs are gently moved.

Should the part be sensitive to hght touch, though insensitive to prick,
movement of the hairs will produce a well-localised tickling sensation. But a
hair can be plucked out without producing more than a sensation of touch.

CHAPTER XII

HYPERALGESIA

A HAND that has passed through the first stage of recovery has become
sensitive to prick. So great is the discomfort, and so brisk the movement of
withdrawal, when the hand is pricked, that the parts affected are not
infrequently said to be " hypersesthetic " or " hyperalgesic." We have
shown that excessive reaction to this form of stimulation is associated with
loss of all the finer forms of sensation ; it is due to the presence of a peculiar
form of sensibility. It is, in fact, the expression of a deficiency rather than
of excess, and it disappears gradually with the return of the higher forms of
sensation.

But a true exaggeration of sensibility to pain may exist apart from any
defect in sensation of light touch. Such hyperalgesia is rarely the result of
wounds of peripheral nerves in modern surgical practice, but it underlies the
remarkable condition described by Weir-^NIitchell (133) under the name of
" causalgia," and can still be seen as he described it after injmies particularly
with the older forms of bullets. L. G. H. (Case 63) ^ showed this sensitiveness
in so typical a form that a description of his condition might have been taken
from the pages of Weir-Mitchell.

He was wounded at Tweefontein on July 22, 1901, by a bullet that entered
4| ins. (irS cm.) below the internal condyle of the humerus, passing across the
forearm to the radial side. Not until he had been in hospital three weeks
did the hand become painful. The pain became steacUly more intense, and
when we saw him first (January 26, 1902) was constant. At that time, the
skin of the hand was characteristically smooth, glossy and of a pinkish-blue
colour, the fingers tapered and the nails were long and curved.

The hand was intensely tender over a large area, occupying the palm, the
ulnar half of the thenar eminence, the palmar aspect of the thumb and the
palmar aspect of the little, ring and middle fingers. Over the dorsal surface
this tenderness occupied the ulnar half of the hand and extended to the tendon
of the ring finger. The skin of the dorsal surface of the Httle, ring and middle
fingers was intensely sensitive to pinching, to pressure with the head of a pin
and to the pin-point.

Sensation to light touch and to the painless interrupted current was lost
over the usual ulnar area, and here the discrimination of the compass points

1 Vide p. 210.
160

INJURY TO THE PERIPHERAL NERVES

161

was extremely defective. Sensibility to the more extreme degrees of tempera-
ture was perfect everywhere, but ice and water at 50° C. tended to cause
pain.

This man's hand, as far as the loss of sensation was concerned, was exactly
in the condition which follows an injury without complete destruction of the
ulnar nerve. Hitherto in all our cases excessive sensibility to prick has been
confined to the so-called anatomical distribution of the affected nerve ; that is
to say, over-sensitiveness to prick so far has always coincided with the Umits
of loss to the higher forms of sensation. When the ulnar nerve was destroyed
it lay within an area on the palm to the ulnar side of a line through the axis of
the ring finger.

A shows the ex.tent of the hyperalgesia produced by irritation of the uhiar nerve in Case 63.
B shows the extent of the loss of sensation to light touch present before the operation.
C shows the loss of sensation produced by dividing the ulnar nerve in the same patient.

But here the tenderness exceeded the area of loss of sensation caused by
injury to the nerve, extending on to the median half of the j)alm. Moreover,
it was found over parts that were in no way insensitive to light touch, the
interrupted current, or the two points of the compasses.

Obviously this wide extent of hyperalgesia might be explained by supposing
that the median nerve had also been affected by the injur3^ But, apart from
the total absence of motor or sensory paralysis pointing to injurj^ of this nerve,
this explanation was at once negatived by the results that followed division of
the ulnar. On the afternoon of January 30, the ulnar nerve was separated
from fibrous tissue, the two ends freshened, and then united by means of a
graft. Next morning all pain and tenderness had gone from the hand, and the
sensation of the ulnar half was such as might have been expected after total
division of the ulnar nerve.

VOL. I. M

162 STUDIES IN NEUROLOGY

It is therefore certain that the impulses, which produced the true hyperal-
gesia over the median half of the palm, must have travelled by way of the ulnar
nerve. The pain must have been caused by some irritation of the trunk of
this nerve ; and yet the tenderness far exceeded any area of loss of sensation
produced by division of the ulnar nerve.

The following case illustrates a similar hyperalgesia produced by injury of
the median. The absence of any exploratory operation and our consequent
ignorance of the limits of the loss of sensation that would have been caused by
division of the nerve affected make it less convincing ; but, in the light of the
previous observation, the condition would appear to have been caused by injury
of the nerve combined with irritation of its trunk.

J. W. (Case 64),^ an Imperial Yeoman, was shot through the arm with a
Martini bullet on August 1, 1901. The Boers took from him all they wanted,
and he lay for two days and one night on the veldt. He was then found and
taken to hospital. The wound " became very foul," and did not heal for more
than five weeks. At first the arm was painless, but about a month after he was
wounded, pain began in the hand and steadily increased. After a while the
pain was always present and of about the same intensity, except when the
weather was cold. In the winter it was scarcely troublesome so long as the
hand was exposed to the cold, and cold water always removed the pain for a
time.

The bullet had entered the left arm at a point 1| ins. (4 cm.) above the
external condyle of the humerus; 2| ins. (7 cm.) above the internal condyle
lay the wound of exit, oval in shape and 1 in. (25 cm.) in its longest diameter.
Both scars showed a tendency to become keloid.

This case was complicated from both motor and sensory aspects by injury
to the musculo -spiral nerve. But for the purposes of the present chapter, it
will be well to concentrate our attention on the sensory condition of the palm.
Injury to the median nerve had produced loss of sensation exactly corresponding
to that usually found, when the loss to prick has cleared away from the palm.
Light touch and the minor degrees of heat and cold were lost over an area
occupying the radial half of the palm, the index, middle, and half the ring
fingers. The palmar aspect of the index and middle fingers and of the thumb
were insensitive to prick and to the extremes of heat and cold.

At the same time, the opponens and abductor pollicis muscles were
paralysed, wasted and inactive to the interrupted current.

This loss both of motion and sensation pointed to an injury amounting to
functional interruption of the trunk of the median nerve. But in addition to
these paralytic symptoms, J. W. complained of intense tenderness in the palm
of the hand. The elbow supported by a sling, he walked about with his hand
exposed, terrified lest it should be touched or jarred. The extent of this tender-
ness could be marked out by pressure with the head of a pin or by dragging the
point lightly across the skin from normal to abnormal parts. Comparison of

1 Vide p. 221.

INJURY TO THE PERIPHERAL NERVES

163

the two figures (fig. 33, a and b) shows that the distribution of the tenderness
considerably exceeded the area insensitive to light touch, extending to the ulnar
side of the palm and occupying the whole of the ring finger. To the radial side

I'".

B
Fig. 33.

A, to show the area which became intensely tender in Case 64.

B, to show the extent of the loss of sensation in the same case. Total cutaneous insensibility is
showii in black. The area of loss of the higher forms of sensation (light touch, etc.) is enclosed in a
single line.

it transgressed the line of anaesthesia to light touch on the thenar eminence and
occupied the skin over the dorsal surface of the terminal jDlialanx of the thumb.
The suffering caused, when the skin of the tender area was touched, exceeded
anything we have seen in parts that have become over-sensitive to pain as a
result of destruction of the higher forms of sensibility.

164 STUDIES IN NEUROLOGY

Thus we must conclude that this man suffered from an injury which inter-
fered with both sensory and motor functions of the median nerve, and at the
same time produ.ced an irritative state manifested by tenderness of the palm of
the hand of unusually wide distribution. This true hyperalgesia was absent
over those parts of the hand which were totally analgesic, and did not invade
the little finger or extreme ulnar border of the hand which, as we have seen,
become totally analgesic when the ulnar nerve is divided.

In both the examples already given, the hyperalgesia was accompanied by
some loss of sensation over the area supplied by the injured nerve. But in the
following instance injury to the anterior division of the external cutaneous
caused true hyperalgesia uncomplicated by any loss, even of the higher forms
of sensation.

L. E. (Case 45, v/fZep. Ill) fell on to a china jug, injuring the anterior division
of the external cutaneous in the lower third of the forearm. Two weeks later
he complained of pain, and the wound was reopened. When we examined him
first, fourteen weeks after the accident, he was complaining of pain over an
area extending from the position of the scar to the ball of the thumb.

Over the outer aspect of the forearm below the scar was an area, extending
on to the thenar eminence, exquisitely tender to any form of pressure or to the
point of a pin. Here sensation to cotton wool was perfect, and two points
could be discriminated at a distance of 3 cm. when applied in the longitudinal
axis of the Umb. To this test there was no material difference between the two
forearms.

From these examples it would seem that true hyperalgesia may make its
appearance. But it is of rare occurrence and seldom arises immediately after
injury.

It may co-exist with a variable amount of diminution in the sensory
functions of the nerve, but disappears if the nerve is divided. It tends to
return unless the injured portion is excised and the two ends sutured together.
Simple division of the nerve does not suffice to effect a permanent ciu'e.

The area occupied by this hyperalgesia extends to the remotest ramifications
of the injured nerve as discovered by anatomical dissection and transcends on
all sides the limits of even the most extensive loss of sensation produced when
the same nerve is di\4ded. When it occupies parts that are sensitive to light
touch, its presence does not disturb the normal distance at which two compass
points can be distinguished.

CHAPTER XIII

CHANGES IN THE SKIN ASSOCIATED WITH INJURIES TO PERIPHERAL NERVES

It is a matter of universal experience, that parts within the territory of an
injured nerve are Hable to undergo changes in the rate and nature of their growth.
The nails may grow with unusual rapidity, and the skin become thin and glossy ;
or the epithelium remains heaped up into masses, and the gro^vth of the nails
may be scarcely perceptible. The parts may ulcerate, and painless whitlows
be produced, in consequence of trivial injuries. Bhsters arise without a burn
or other assignable cause.

Such changes fall natiu-ally into two groups, those associated with absence
of sensibility to pain, and those that occur in parts that are hyperalgesic and
the seat of spontaneous pain. Of these we shall first consider disturbances of
nutrition in parts insensitive to pain, not only because they more commonly
follow the nerve wounds of civil life, but because they yield data required for a
complete understanding of the trophic changes which accompany hyperalgesia.

When one of the nerves of the palm is completely divided the skin no longer
desquamates so readily over the area of complete analgesia. This is particularly
obvious when the patient happens to be a man who works with his hands.
^Normal parts of his horny palm protected by the cotton wool of the dressings
tend to become softer with disuse, but over the abnormal area the epithelium
is not shed, remaining for many weeks as a rough layer on the surface.

When the wound is healed, and the splint removed from the hand, this want
of desquamation is still visible in patients of the hosj)ital class. But, if the
hand is well scrubbed with soap and warm water, the dry epithelium comes away
in flakes, exposmg skin over the affected area, j)inld8h-blue in colour, colder
than normal to the touch. This skin is inelastic and wrinkled, and the normal
whorled markings are intersected by innumerable fine Hues.

Over the back of the hand, these changes are even better seen than over the
palm. Division of the radial and external cutaneous nerves in H.H. caused the
skin of the radial half of the back of the hand to become inelastic ; it somewhat
resembled the skin of an old man. But in addition to this senile appearance,
the superficial layers of the epithelium had formed scales ; the affected parts
were evidently cMer than the normal skin, and the cracks better marked. This
gave to the radial half of the hand an appearance resembling the skin of a toad.
These changes correspond exactly with the area insensitive to prick, to heat and

165

166

STUDIES IN NEUROLOGY

TABLE VII.— TROPHIC DISTURBANCES OF THE SKIN

No.

Mature of Injury.

Nerve
United.

Nature of Trophic Disturbance.

Case 65

Case 19

Case 15

Case 18

Case 30

Case 29

Case 31
Case 13
Case 12
Case 6

Ulnar. Glass cut. Primary
suture. Suppurated

Dec. 27, Blister on ubiar side of palm

1S98

Ulnar. Nerve divided and June 17,
resuturod 1904

Whole of little finger red and shiny. Larffo blister

Case

Case 66

Case 5

Case 8

Ulnar. Primary suture ...

Ulnar. Glass cut. Sutured
fourteen days later

Median incomplete. Glass
cut

Median, incomplete. Glass
cut, Sept. 20, 1902

Median, incomplete. Dec.
18, 1904. Glass cut

Median. Secondary suture

Median. Razor cut. Pri-
mary suture

In consequence of a stitch
abscess sensation became
lost again

Median. Glass cut. Suture
eight davs later

July 29, I Ulnar side of little finger, ulcer covered with scab
1903

Julv 31.
1902

July 31,

Dec. 3, 1992. — Sore on dorsum of first phalanx little
finger

Oct. 7. — Small blister on tip of middle finger.

1904 Oct. 22. — Irritated to a large sore

Explored
same day

Feb. 6,
1905

Feb. 22,
1904

Oct. 3,
1903

Sept. 14,
...1902

Case 85

Median, incomplete. Glass
cut, Aug., 1901

Median. Knife cut. Opera-
tion two days later

Nov. 26.- — Blisters on index and middle fingers

Feb. 15, 1905. — Blister on index

Feb. 22. — Blisters between index and middle and
middle and ring fingers

June 8.^ — -Blister on palmar surface of terminal
phalanx middle finger

Jan. 10, 1904. — Blisters on tip of index and middle

fingers
Oct. 26, 1904.- — ^Oval ulcer, came as a bhster in night

on terminal phalanx middle finger.
Dec. 22, 1904. — Large bUster over index

Nov. 26, 1902.— Bhster on index. Second " blood
blister " on same site a few days later

Nov. 4, 1901. — Tips of index and middle fingers
bulbous. Both nails gone; nail-beds granulating
surfaces

Oct. 4, Dec. 10, 1902. — Ulcer and blisters index.
1902 I Dec. 30.— Many fresh ulcers.

March 8, 1903. — Black blisters on tip of index

Median. Wrist cut with a Feb. 9, March 4, 1903. — Two ulcers and a blister on index,
piece of coal, Feb. 7, | 1903 Blister on palmar surface of middle finger.

1903

Median with radial and
part of external cuta-
neous. Glass cut, April
29, 1902. Secondary
suture

May 13. — Whole terminal phalanx of middle finger
an open sore. Nail gone

June 3, Aug. 14. — Many ulcers and blisters on thumb, index
1902 and middle fingers.

Sores continued to appear and tip of index became
disorganised

INJURY TO THE PERIPHERAL NERVES

167

FOLLOWING DIVISION OF THE NERVES OF THE HAND

Cause Assigned.

Result.

Condition of Sensation at Time of Appearance of
Tropliic Change.

Burn ...

None

Burn, Nov. 18

Paibbing the affected
jjarts

No definite cause. Sore
irritated with oxalic
acid

Driving

Burn with cigarette ...

None ...

Pinched finger

None ...
None ...

Work as a butcher. No
cause known

All said to be due to
burns. These healed,
but the finger broke
out again when he
began to clean jdcw-
ter with sand and
soda water

Healed well
Healed in one month
Healed in eight weeks
Healed Dec. 31

Healed with return of
sensation Dec. 14

HealedbyFeb. 11, 1903

Healed by March 1 ...

Healed by March 8 ...

Healed by July 13

Healed by March 30 ...
Healed by Nov. 16.

Healed by Jan. 7, 1903

Nails began to reform
Jan., 1902

Healed Dec. 30.
No trophic changes
after May, 1903

Burns during work as a All healed soundly by

plumber

Dec. 20, 1903

Pr(jtopathic loss over little finger and ulnar border of
hand.

Protopathic loss over little finger and ulnar border of
hand.

Protopathic loss over little finger, but recovered on
palm.

Protopathic clearing rapidlj\ Loss over little finger.
Cleared Jan. 14, 1903.

Protopathic loss had begun to clear and soon corre-
sponded almost exactly with the large bUster.
Protopathic cleared Dec. 14.

Oct. 22.- — Both forms of sensation began to clear
together. Protopathic loss over last two phalanges
middle and ring fingers on Nov. 26.

Protopathic loss index and middle fingers. Had begun
to clear rapidly.

Protopathic loss middle and index fingers.

Protopathic loss two terminal phalanges index and
middle fingers. Cleared Aug. 28.

Protopathic loss on index and middle fingers. Not
clearing. Cleared by April 27.

Protopathic loss over two terminal phalanges of
middle finger. Clearing rapidly. Then remameJ
stationary throughout winter. Cleared June, 1903.

Protopathic loss over two terminal phalanges index
and middle fingers. Cleared May, 1902.

Protopathic loss index and middle fingers. Began to
clear March, 1903. Cleared May 24.

Protopathic loss had begun to clear from palm on
March 4, but index and middle fingers were insensi-
tive. May 13, protoi^athic sensibility lost over one
and a half terminal phalanges of middle finger.

Protopathic lost completely over thumb, index and
middle fingers. Protopatliic sensibihty returned
completely Dec. 20, 1903.

168

STUDIES IN NEUROLOGY

No.

Nature of Injury.

Nerve
United.

Nature of Trophic Disturbance.

Case

Median.
1901

Glass cut, May,

Median. Glass cut. Pri-
mary suture

Median and ulnar. Glass
cut, Sept. 24, 1902

Complete ulnar, partial
median. Glass cut. Pri-
mary suture

Median and ulnar. Glass
cut. Primary suture

Partial median and ulnar.
Cut wrist with penknife,
Oct. 21, 1903. Secondary
suture of ulnar

Median and ulnar. Cut with
jug. Primary suture

May 16, ! On Julj' 15, 1901, ulcers were present on thumb,

1902 ' index and middle finorers. Began as blistei's;
showed no signs of healing. Fresh sores appeared
and by April, 1902, two terminal phalanges index
and middle fingers, were enlarged, and tip of index
was destro,yed.

No ulcers during two months out of work.

Oct. — JMiddle finger amputation for necrosis of bone.

Dec. 21, 1902.— Fresh ulcer

Jan. 21, March 15. — BUster on index. Cut on tip of index
1905 has formed a small sore.

April 19. — Whole tij) of finger ulcerated. Terminal
two phalanges involved in a large blister

April 17, ! March, 1903. — Tips of fingers grew hard and dis-

1903 charged. Placed in hot water they became
blistered.

April 16. — Nail destroj'ed; granulating sore. Whole
terminal phalanx of index enlarged

Nov. 30, Jan. 14, 1905.^ — Two blister.s on dorsum of little and

1904 ring fingers.
Jan. 26. — Further blisters appeared

Dec. 24, March 8, 1903. — Dorsal surface second phalanx
1902 middle and ring fingers scabbed ulcer

Jan. 11, Dec. 21, 1903. — Blisters on middle and ring fingers.
1904 None elsewhere. These formed ulcers

Oct. 26, March 4. — On tip of index a brown callosity, and on
1902 middle finger a bhster

to cold. The hairs were very irregular and did not he in sweeping masses ;
they stood up or were laid in an uneven manner, each hair occupying a different
position, as on an uncombed head. The whole of this area was of a slightly
deeper red than the rest of the skm of the hand, and so definite was the difference
in colour that it became impressed on the photographic plate as a well-defined
patch darker than the surrounding sldn (fig. 49, p. 227).

In this condition the whole of the area insensitive to prick does not sweat.
This causes a dryness which adds greatly to the scaly appearance of the affected
part. If a pin is dragged lightly from normal to abnormal parts, it produces
over the healthy sldn a fine red mark which disappears rapidly, but over parts
insensitive to prick, the point produces a white j)owdery line that lasts for
many hours, or even days. This is best seen over the forearm or back of the
hand, and is evidently due to the removal of dry epithelial scales.

A prick over an area in this condition draws blood easily, and the marks
caused by this stimulation last for many hours after they have faded from the
normal skin.

All these abnormalities disappear with the return of sensibility to prick.

INJURY TO THE PERIPHERAL NERVES

169

Cause Assigned.

Result.

Condition of Sensation at Time of Appearance of
Trophic Change.

Worked as a stone
sawver

Due to iisina; a knife,
April 19. Attributed to
hot water

Work as a carpenter ,

Burn

Attributed to hot water
into which whole
hand was dipped

Jan. 25, 1903, all sores
healed, and in spite
of work none have
appeared since

All sores healed after
operation, April 17,
1903. Then broke
out again and lasted
until Dec. 20, 1903

All healed March 8,
1905

Healed by July, 1903

Healed by June, 1903

Protopathic sensibility returned Jan. 2,5, 1903.

Protopathic loss clearing rapidly April 19, 1905.

Protopathic sensation began to return by April, 1903.
Finally returned Dec. 20, 1903.

Protopathic sensation began to return to the palm
on Feb. 1, 1905.

Protopathic sensation returned completely July 12,
1903.

Middle and ring fingers only were analgesic. Proto-
pathic sensibility returned rapidly after secondary
suture, but had begun to clear before the operation.

March 4. — Protopathic sensibility showed first sign
of returning. Completely returned August, 1903.

The hand or other affected part begins again to sweat, and may become moister
than the surrounding skin. On the arm and leg, when sensibihty to prick
has returned, the skin no longer shows any distinctive peculiarity. But over
the hand it becomes of a pinkish colour, and the rough hand of a man may gain
an almost feminine fineness.

As soon as the hand becomes sensitive to prick, the original sensation of
stiffness disappears and is replaced by soreness. It no longer seems to be en-
cased in a tight glove, or to be painted with a layer of collodion ; movement
now causes pain, as if a bruised part were disturbed.

During the time when the skin is insensitive to pain it is peculiarly liable
to injury ; a burn or a cut is unperceived and it is therefore neglected. In this
way sores and ulcers are j)roduced, which from their situation or from the
nature of the infection may lead to the destruction of a considerable portion
of the finger. One of our patients, a stonemason, refusing to trouble about a
painless ulcer, ground away the terminal phalanx of his finger against the stone
he was occupied in sawing. If protected from injury and infection, these sores
heal completely; but comparative trivial injury will cause them to break out

170 STUDIES IN NEUROLOGY

again. The healing differs from that of an nicer on normal parts only m the
slowness of the process. Blisters are liable to form a callositj'', which if removed
leaves a raw surface. From such a sore, especially when situated in the loose
skin on the back of the hand, blood and serum can be expressed by manipula-
tions, insufficient to cause such exudate from a sore healing under normal
conditions. The defective elasticity of the skin will cause these sores to reopen,
and a sore on the back of the hand broke open when apparently healed, in
consequence of the stretching caused by gripping firmly the handle of a bicycle.

If the patient is engaged on any work that mjures his hand, even slightly,
these injuries will lead to the formation of ulcers that may necessitate the
removal of the finger. A potman who had divided his median nerve cleaned
the pewters with silver sand and soda water : the terminal phalanx of the
middle finger became an open sore, the matrix of the nail necrosed, and the nail
was lost. Another patient, a plumber by trade, repeatedly burnt the affected
fingers in the act of soldering.

But ulcers may make their appearance, when the hand is insensitive to
prick, apart from any recognisable injury. Such ulcers always start as blisters
which break. Sometimes the contents are serous, but they may be blood-
stamed and form the so-called '" blood blister." Such blisters usually arise
at a time when sensibility to prick is beginning to return, but the analgesia
has not disappeared from the parts over which the blister is situated.

Whatever their cause, whether they arise from external injury or not, all
these defects of nutrition disappear with the return of sensibility to pain, and
to the more extreme forms of heat and cold. In the case of a plumber (Case
85) 1 a series of ulcers caused by trivial injuries in his trade had led to destruc-
tion of the top of his index finger. The whole of the index and middle fingers
except the terminal phalanges had become sensitive to prick by October 25,
1903, and all but the ulcer over the terminal phalanx of the middle finger
had healed. By December 20, 1903, the whole hand had become sensitive
to painful stimulation, and not only had all the sores healed, but no others
made their appearance, although the median area of the hand was still insensi-
tive to light touch and to minor degrees of temperature. This immunity from
ulceration existed in spite of work continued under unaltered conditions.
Similarly a carpenter who had divided both median and ulnar (Case 28, Table
III., p. 96) '^ suffered before and after secondary suture of the nerves from ulcers,
caused by bums or by blisters arising from the use of his tools. They troubled
him up till the complete return of sensibility to prick, eight months after suture,
when they healed firmly and never recurred. In April, 1905, the whole palm
and fhigers were insensitive to light touch and to minor degrees of temperature ;
but, whenever he burnt his hand the blister healed as quickly and firmly as
on the normal side.

In this connection Case 6 (Table I., p. 90)^ is of interest.' On October 3,
1903, he divided the median nerve of his right hand, together with most of
1 Vide p. 218. 2 p, 214. 1 Vide p. 202.

INJURY TO THE PERIPHERAL NERVES 171

the tendons on the front of his wrist. The divided tendons and nerve were
united next day and the wound healed. In January, 1904, blisters appeared
on the termination of the index and middle fingers, said to be caused by burns ;
those on the radial side of the index finger formed shallow ulcers, which did not
heal until April, 1904. By April 27, sensibility to prick and to the extremes
of temperature had returned to all parts of the hand, but the whole median
area of the palm remained msensitive to light touch. He steadily improved
until the end of August, when a swelling appeared at the site of the original
wound. This was opened and pus evacuated, probably due to infection of
one of the silk sutures, by which the nerve had been united. This suppuration
threw back the recovery of the hand to such an extent that the two terminal
phalanges of the middle and ring fingers became again insensitive to all degrees
of temperature and totally analgesic. On October 23, on waking in the morn-
ing, he noticed a blister on the terminal phalanx of the middle finger. Except-
ing that it was entirely insensitive, this finger was not affected the night before
when he went to bed. On October 31 the site of the wound was explored by
one of us and the nerve was found to be embedded in a mass of fibrous tissue ;
it was freed and in a month sensation had begun to improve. But on December
18, when he woke m the morning a large blister had appeared on the dorsal
aspect of the terminal phalanx of the index finger. This formed a sore, which
did not heal until July, 1905. By this date, all analgesia had disappeared and
the affected parts had become sensitive to prick and to the extremes of heat
and cold, but remained insensitive to light touch. From this time no further
blisters have made their appearance.

The distribution of these ulcers is a further proof of the close association
between trophic defects and the absence of sensibility to pain. Under no cir-
cumstances, unless complicated by acute sepsis, do they extend beyond the
analgesic area. A youth, aged 14 (Case 30, Table IV., p. 100), cut his wrist with
broken glass, injuring, but not completely dividing, his median nerve (July 31,
1904). Sensation to prick began to return in September, and by October only
the terminal phalanges of the middle and index fingers remamed insensitive.
On October 12, the skin over the tip of the middle finger broke, formmg a sore.
On October 22, he cleaned the brass of some bedsteads, using oxalic acid for
the purpose. When we saw him four days later the skin over the whole terminal
phalanx of the middle finger was raised to form a large blister. This occupied
the whole analgesic area and was strictly limited to the parts insensitive to
pain. At this time sensibility was returning rapidly and the raw surface healed
steadily, keeping pace with the return of sensation. By December 14, it had
healed completely and the middle finger had become sensitive to the tip.

That the neuralgia consequent on injury to a nerve may be associated with
changes in the skin has been known for nearly a century. In 1813, Alexander
Denmark (26) reported the case of a man wounded at the storming of Badajos.
The bullet entered 1| ins. above the inner condyle of the humerus and came out
on the outer side, in front of the elbow-joint. No date is given for the onset

172 STUDIES IN NEUROLOGY

of the pain, which was intense. " I always found him with the forearm bent
and in the supine position, supported by the firm grasp of the other hand. . . ."
He described the sensation of pain as beginning at the extremities of the thumb
and all the fingers except the little one, and extending up the arm to the part
wounded. " It was of a burning nature and so violent as to cause a continual
perspiration from hiii face. He had an excoriation on the palm from which
exuded an ichorous discharge."

Although this is an excellent description of the condition so fully described
by Weir-Mitchell, Morehouse and Keen, under the name of causalgia,
Denmark makes no mention of the glossy skin that so commonly accompanies
this form of hyperalgesia. The first description of this condition was given
by Hamilton (43) in 1838. He described the pain and tenderness which may
follow nerve injuries, and states that they may be accompanied by redness and
swelling resembling the appearance of the skin in infiammation of the fascia
or a deep collection of matter.

The first complete account of this state occurs in a clinical lecture by Paget
(89) delivered in 1864. As some want of apprehension of his teaching has led
to subsequent misunderstanding we give his summary in full.

" Glossy fingers appear to be a sign of peculiar Ij^ impaired nutrition and cir-
culation due to the injury of nerves. They are not observed in all cases of
injured nerves and I cannot tell what are the peculiar conditions of the cases in
which they are found ; but they are a very notable sign and are always associ-
ated, I think, with distressing and hardly manageable pain and disability. In
well-marked cases the fingers which are affected are usually tapering, smooth,
hairless, almost devoid of wTinkles, glossy pink or ruddy, or blotched, as if
with permanent chilblains. They are commonly also very painful, especially
on motion, and pain often extends from them up the arm. In most of the
cases this condition of the fingers is attended with very distinct neuralgia both
in them and in the whole arm, and its relation to disturbance of the nervous
condition of the part is, moreover, indicated by its occasional occurrence in
cases where neuralgia continues after an attack of shingles affecting the arm."

To Weir-Mitchell, Morehouse and Keen is due the credit of a complete
description of a series of cases illustrating this condition. This they published
in 1864, in a volume long out of print, but the original description is quoted
and amplified by Weir-Mtchell (133) in his book on the Injuries of Nerves.
He says : " The skin affected in these cases was deep red or mottled, or red and
pale in patches. The epithelium appeared to have been partially lost, so that
the cutis was exposed in places. The subcuticular tissues were nearly all
shrunken, and where the palm alone was attacked the part so diseased seemed
to be a little depressed and firmer and less elastic than common. In the
fingers there were often cracks in the altered skin and the integuments presented
the appearance of being tightly drawn over the subjacent tissues. The surface
of all the affected parts was glossy and shining, as though it had been skilfully
varnished. Nothing more curious than these red and shining tissues can be

INJURY TO THE PERIPHERAL NERVES 173

conceived of. In most of them the part was devoid of wrinkles and perfectly
free from hair. Mr. Paget's comparison of chilblains is one we often used to
describe these appearances ; but in some instances we have been more strikingly
reminded of the characters of certain large thin and polished scars."

In recent years this condition so accurately described by Paget and Weir-
Mtchell, and by them associated correctly with pain and tenderness, has been
confused with the atrophic conditions that accompany loss of sensibility.
Some writers, by the statement that glossy skin is not associated with pain
and tenderness, show that they have failed to recognise the essential difference
between the condition described by Paget and Weir-Mtchell and the atrophic
skin which not infrequently results from division of a peripheral nerve. This
confusion is fatal to a comprehension of that condition to which the name
" glossy skin " can alone be applied with propriety.

WTien considering in a previous chapter the hyperalgesia which may
follow a nerve injury, we quoted the case of a gunshot wound of the ulnar nerve
(Case 63).^ The whole palm of the affected hand was of a pinkish colour and
smooth. The markings were not absent, but the injured hand appeared as
if seen through a layer of collodion. Over the dorsal surface of the fingers,
particularly over the last two phalanges, the skm was thin and shmy, and the
hairs had disappeared. This glossy appearance occupied the thumb, index,
middle, ring and little fingers on their palmar aspect and the dorsal surface of
the two terminal phalanges of all four fingers.

The palm was intensely tender and hyperalgesia was found over the palmar
aspect of the little, ring and middle fingers. On the dorsal surface, the ulnar
half of the back of the hand, together with the whole of the little and ring and
the greater part of the middle finger, was intensely tender to pressure or to the
point of a pin.

The skin was glossy over an extent somewhat wider than that of the hyperal-
gesia, but both greatly exceeded the area which subsequently became insensitive
after the nerve had been divided (fig. 32, a and c, p. 161).

The characteristic condition of the nails will be dealt with in the next
chapter; they were curved and exquisitely tender. On January 30, 1902,
the ulnar nerve was dissected at the site of the injury, the two ends freshened
and united by a graft. On February 4, the glossy appearance of the skin and
all hyperalgesia had disappeared, the sensory state of the hand beiiig that which
follows complete division of the ulnar nerve.

True hyperalgesia may exist without the skin becoming glossy, and of the
remaining instances cited in Chapter XII, to illustrate this form of tenderness,
none were accompanied by this characteristic change. Its full significance
can only be determined by an examination of a series of cases, an opportunity
that is not likely to occur in civil practice.

We have already dealt with the blisters which are liable to appear over parts
totally insensitive to cutaneous stimuli ; Weir-lVIitchell describes the various

1 Reported in full on p. 210.

174 STUDIES IN NEUROLOGY

forms of eruption that can accompany hyperalgesia. He says : "It was some-
what rare to see any case of glossy sldn, especially with causalgia, unattended
with vesicles." But in the only complete instance of this condition which has
come under our notice, no rash had been present at any time. In one patient
who suffered wdth true hyperalgesia (Case 64) ^ a herpetiforra rash was said to
have appeared over the little and ring fingers, and ulnar half of the palm, four
months before we first saw him.

1 Reported in full on p. 221.

CHAPTER XIV

CHANGES IN THE NAILS ASSOCIATED WITH NERVE INJURIES

Since Weir-Mitchell first described systematically the changes in the nails
which follow nerve injuries, most observers have contented themselves with
supporting or qualifying his statements.

No one can doubt that the growth and texture of the nails is profoundly
affected when a nerve to the hand is injured, but no systematic observations
have been instituted to discover the cause of these changes. The general
acceptance, overtly or by implication, of some trophic influence exercised by
nerves on epithelial structures has led to an absence of that rigid series of control
experiments Avhich are necessary, before any such theory can be upheld.

A nerve injury affecting the hand produces a combination of extremely
complex conditions. To ensure union of the divided nerve, the arm is placed
upon a splint. The muscles of the hand may be paralysed and useless for manj"
months, so that all those movements necessitated by daily life are materially
restricted. Division of one or more arteries at the time of the accident may
diminish the supply of blood to the hand, and vasomotor changes may result
from the nerve injury. Moreover, the fact that nerve influence has been
removed from the hand renders that part increasingly sensitive to the vascular
influence of cold ; it will become blue at temperatures that produce no such
effect upon the normal skin. To correct these bad effects the hand is not un-
commonly massaged, and we shall show that this also has a material influence
on the growth of the nails.

We tried many methods for registering the growth of the nails, but returned
to that originally recommended by Weir-Mitchell. A mark is made with nitric
acid on that part of the base of the nail which has jvist emerged from the cover
of the skin ; week by week we register the passage of this orange streak until
it reaches the free edge and is removed by the scissors. Care must be taken that
the acid does not excoriate the nails but acts only as an indelible stain. This
is not always easy to carry out in practice, in consequence of the different
texture of the nails of the sound and affected hands. If the nails are rough,
an application which scarcely stains the normal nail will bum those that are
abnormal ; or the density and firmness, noticeable in nails in which growth has
been long delayed, may render staining difficult without repeated application.
After the acid has been placed upon the nails, it is well to wait until the stain
begins to appear ; then the hand should be well washed and dried before the

175

176

STUDIES IN NEUROLOGY

patient is dismissed, to make certain that the acid does not continue to act
harmfully.

Immobilisation of the hand upon a splint retards profoundly the growth
of the nails. After a fortnight, the nails on the free hand may have grown
to three times the extent of those on the hand that was restrained. These
changes are so startling, and have so completely failed to attract attention,
that we give shortly the details of some of our most satisfactory observations.

TABLE VIII

•-i

Growth of Nails.

No.

Age.

Sex.

Fracture.

a-r

Aflfected Side.

Normal Side.

Case 68

Right Colles'

1 mm.

3 mm.

Case 69

Right CoUes'

1-5, 1-0, 0-5, 0-5,
0'5 mm.

Case 70

Right radius ...

1 mm.

2 mm.

Case 71

Left radius

2-5 mm.

3-5 mm.

Case 72

Left radius

0-5 mm.

2 mm.

Case 73

Right uhia

2 mm.

3-5 mm.

Case 74

Left radius

2-5 mm.

Case 75

Right radius and uhia

0-5 mm.

1-5 ram.

Case 76

Left radius and uhia

1-5 mm.

Case 77

Separated lower epiphysis of left
lumerus

1-5 mm.

2-5 mm.

Case 78

Separated lower epiphj^sis of left
humerus

2 mm.

3 mm.

Case 79

Shaft of left humerus

3 mm.

4 mm.

Case 80

Shaft of left humerus ...

3 mm.

On this table one number only is given, whenever the nails on all the fingers grew to the same
amount. But if they grew differently on any of the fingers, the measure of their growth is given in
a series beginning with that of the thumb.

It will be seen that the patients were of diverse ages, and the injuries for which
the arm was placed in the splint ranged from fracture of the humerus to fracture
of the lower end of the radius. In no case was the growth on the two sides
even approximately equal, and the uniformity of growth in all the nails of the
quiescent hand was remarkable. This diminution of growth is not due to
any change in the blood supply of the arm, produced by either bandages or
splints, for if the arm is bandaged to a splint, but the hand left free, growth
is not materially retarded.

In No. 75, in consequence of fracture of the right radius and ulna, the arm

INJURY TO THE PERIPHERAL NERVES

177

was placed on a splint with the hand immobilised for fourteen days ; in this
time the nails had grown three times as much on the left as on the right hand.
For the next twelve days the right arm remained on the splint but the hand
was freed, and the patient was encouraged to move the fingers. Growth was
now equal in the nails of both hands (TS mm.). For this reason a sling makes
no material difference to the growth of the nails, provided that it is not used in
consequence of some affection tending to cause restriction m the movements
of the hand. A boy, aged 9 (Case 76), fractured his left radius and ulna ;
he was put into splints for fourteen days, during which time the nails of the left
hand did not grow to any measurable amount. During the next eight days
the arm was kept in a sling, but the nails grew equally on both hands.

Massage causes little definite increase in the growth of the nails of a hand
in ordinary daily use. A healthy young woman who had no daily occupation
attended the massage department regularly from August 10 to September 21.
Her left hand was rubbed for twenty minutes, three times a week, but it is
impossible to say that this treatment made any perceptible difference to the
growth of her nails.

Forty-six Days without Massage.

Le]t.

Right.

Thumb . .

5 mm.

5 mm

Index

5 mm

Middle . .

5 mm.

6 mm

Ring

5-5 mm. . .

6 mm

Little

5 mm.

5 mm

Forty-two Days, Left Hand Massaged Three Times a Week.

Left. Right.

Thumb . . . . . . 6 mm. . . . . . . 7 mm.

Index
Middle
Ring
Little

6 mm.
6 mm.
6 mm.
5 mm.

6 mm.
6 mm.
6 mm.
6 mm.

But if the hand is protected from the cold and rubbed repeatedly, the nails
may grow excessively, even though the arm remain in a sling. Of this, Case 80
i5 an excellent instance. This man fractured his left humerus, and durmg
the twenty-eight days his arm remained in splints the nails of his left hand
did not grow appreciably. During the following fortnight, the left arm was
kept in a sling, but the hand and arm were massaged every second day. At
the end of fourteen days the growth was as follows : —

Lejt {affected).

Right (sound).

Thumb . .

2 mm.

1 mm.

Index

4 mm.

0-5 mm.

Middle . .

4 mm.

0-5 mm.

Ring

4 mm.

1 mm.

Little

?> mm.

0-5 mm.

VOL. I.

178

STUDIES IN NEUROLOGY

Throughout the next two weeks he wore no sling, and the hand was rubbed
five times only.

Left [affected). Right {sound).

Thumb . . . . . . 2 mm. . . . . . . 1-5 mm.

Index
Middle
Ring
Little

1 mm.

1 mm.
1 mm.
r.5 mm.

2 mm.
2 mm.
1-5 mm.
2 mm.

In this instance, the return of the hand to its ordinary uses threw back
the growth of the nails to a figure on the whole slightly below that of the normal
hand. This is an unusual experience ; more commonly, the nails of the two
hands grow equally if the hand is kept in a sling and massaged every second
day.

Thus, whilst immobilisation of the hand on a splint measurably retards
the growth of the nails, massage does not universally produce a correspondmg
increase, provided the hand be normal.

But, when the hand is paralysed or incapacitated from sharing to the
usual extent in the necessary movements of daily life, regular massage tends
to prevent the extreme retardation of growth that would otherwise occur, and
the nails may grow only sightly less rapidly than those of the normal hand.

Muscular paralysis alone will greatly retard the growth of the nails, and
probably for this reason irregularity of growth is so manifest a consequence
of division of the ulnar nerve. This we had hoped to show from cases of motor
paralysis affecting the hand due to destruction of the anterior horns of the
spinal cord. But instances where anterior poliomyelitis has affected one hand
only so gravely that all movement has been destroyed, are uncommon ;
the following case shows how considerable may be the retardation of growth
from this cause. A child of four years old became suddenly ill in July, 1902,
and four days later the right arm and hand were found to be useless.

In February, 1903, she showed all the signs of the paralysis due to anterior
poliomyelitis. The right arm was flaccid ; the muscles of the shoulder were not
acting, with the exception of the upper part of the trapezius. She could
slightly extend the middle and ring fingers, but could make no other movement
of the hand, forearm or arm. During the summer the hand was neither blue
nor cold, but throughout the winter months it was constantly somewhat
colder to touch than the normal hand. All forms of sensation were perfect,
including the sense of passive position. From February 11 to May 13, a
period of ninety-one days, the growth of the nails was almost twice as great
on the sound as on the paralysed hand.

Eight (affected).

Left (sound)

Thumb .

5 mm.

8 mm.

Index

5 mm.

8 mm.

Middle .

5 mm.

9 mm.

Ring

5 mm.

9 mm.

Little

4 mm.

7 mm.

INJURY TO THE PERIPHERAL NERVES 179

During seventy-seven days (from November 4 to January 20) the growth
mamtamed almost exactly the same proportion, showing that the defect was
not due to coldness of the hand.

Right {affected).

Left [sound)

Thumb . .

5 mm.

7 mm.

Index

4 mm.

7 mm.

Middle

4-5 mm. . .

7 mm.

Ring

4-5 mm. . .

7 mm.

Little

4 mm.

5-5 mm.

Whenever we marked the nails of the affected hand we also marked those
on the sound side. By this means we gradually accumulated a large number
of observations on the growth of normal nails extending, in seventeen cases,
over a period of more than a year. Several of these patients remained under
observation consecutively for three years. We noticed that the rate of
growth differed considerably from time to time, and expected to fuid that
this variation was coincident with the seasons of the year. In a few instances
it certainly seemed that the nails grew more rapidly between May and July,
and more slowly between November and March. But of the whole seventeen
cases only six came within this category, and since normally the growth of
the nails is liable to inexplicable variations, we do not consider that our
observations are sufficient to establish any such general rule.

So far we have examined only the result of immobilisation and of other
conditions acting on a hand whose nerves were uninjured and have shown that
limitation of movement is a potent influence in retarding the growth of normal
nails.

Turning to cases of complete division of one or more nerves of the hand,
we find that want of movement is also the prime factor in the profoundly
altered growth of the nails which follows any lesion causing paralysis.

Division of a sensory nerve alone produces no change in the growth of the
nails that spring from the fingers which have become completely insensitive.

Case 81. — Division of the digital brandies of the median and ulnar nerves supplying the ring finger.
Total loss of cutaneous sensibility over the two terminal phalanges. Absence of any alteration in the
growth of the nail of the affected finger.

On October 12, 1903, whilst working as a cabinet maker, G. W. cut the palm of his hand with
a chisel. He came the same night to the London Hospital and two tendons were sutured ; the
wound is said to have healed well.

When he first came under our notice on December 16, 1903, a longitudinal scar ran from the
head of the fourth metacarpal bone to \ in. (about 1-2 cm.) below the fold of the wrist. This
scar, about 2\ ins. (6.5 cm.) in length, was crossed somewhat obliquely at about its centre by a
second smaller scar.

None of the intrinsic muscles of the hand were jiaralysed or wasted and the tendon of the
flexor sublimis that went to the ring finger had united jierfectly.

From the moment of the accident, he recognised that the ring finger was numb. The whole
of the skin over the two terminal phalanges we found to be insensitive to prick and to all forms

180

STUDIES IN NEUROLOGY

of heat and cold; the area of insensibihty to light touch corresponded on the dorsal surface of
the finger to this analgesia but extended on the jialmar aspect as far as its base.

A rounded ulcer with thickened edges and a smooth granulating floor was situated over the
l^almar aspect of the terminal phalanx of the ring finger, evidently healing slowly.

For forty-two days the condition of sensation did not change materially. In tliis time the
nails grew but slightly less on the affected finger than on that of the somid hand. IMoreover, this
small difference was found in all the four fingers and can be accoimted for most probably by some
want of use.

Lejt (affected).

Eight (sound)

Thumb . .

4-5 mm. . .

4-5 mm.

Index

4-5 mm. . .

5 mm.

Middle . .

4 mm.

4-5 mm.

Ring

4 mm.

4-5 mm.

Little

3 mm.

3-5 mm.

In the case of one of us, where the radial and external cutaneous nerves
were divided at the elbow, the nail of the thumb grew to exactly the same
extent on the two sides, although the nail-bed and dorsal surface of the thumb
were insensitive to all cutaneous stimulation.

Division of the median nerve at the A\Tist without injury to the tendons
is an occasional accident. In such a case it will be found that the nails grow
equally on the two sides. Thus after suture of the divided median nerve,
A. C. (Case 4, Table I., p. 90) was kept for thirty-five days on splints. During
this time the nails grew to the following amount : —

Left (affected).

Eight (sound)

Thumb . .

1 mm.

5-5 mm.

Index

1-5 mm.

5-5 mm.

Middle

1 mm.

5 mm.

Eing

2-5 mm

5 mm.

Little

3 mm.

5-5 mm.

But in the thirty-nme days which followed they grew equally, in spite of the
absolute loss of cutaneous sensibility in the mdex and middle fuigers produced
by the nerve injury {vide fig. 7, h, p. 77).

In Case 13 (Table I., p. 90) we had the opportunity of measuring the growth
of the nails after the median nerve had been divided without injury to the
tendoiis, and found that they grew equally on the two sides. Then the wound
was explored and the two completely separated ends were freshened and
reunited.

For sixteen days the hand remained in splints and the nails grew to the
followmg amount : —

Eight (affected).

Left (sound)

Thumb . .

. . 1 mm.

• •

3 mm.

Lidex

2-5 mm. . .

, ,

3 mm.

Middle . .

1-5 mm. . .

. •

3-5 mm.

Ring . . .

2-5 mm. . .

. .

3 mm.

Little

2 mm.

« •

3-5 mm.

INJURY TO THE PERIPHERAL NERVES

181

But as soon as the hand was freed, the nails again grew equally, in spite of the
total cutaneous insensibility of the index and middle fingers.

Complete loss of sensibility to light touch and to the minor degrees of
heat and cold makes no difference to the growth of the nails. In Case 12
(Table I., p. 90, and fig. 7, F, p. 77) all sensation to light touch was lost over
the full median area and yet for sixty-three days the nails grew equally on
both hands. During this period all movements of the hand were perfect except
those of the abductor and opponens pollicis.

Sometimes an incomplete division of the median produces the full loss of
sensation that usually follows complete division of the nerve, without muscular
paralysis. An instance of this condition is to be found in Case 29.^ This
youth showed to a profound degree the influence of immobilisation. During
the thirty-two days after the operation when the hand remained on a splint
the nails grew very little on the affected side.

Left (affected).

Bight [sound)

Thumb . .

1-5 mm. . .

4 mm.

Index

0 mm.

2 mm.

]\Iiddle . .

0 mm.

2-5 mm.

Ring

1-5 mm. . .

3 o mm.

Little

J 1_ P M

2 mm

3 mm.
it . -1

But during the following thirty-five days the nails on the two hands grew
equally in spite of the loss of sensation.

Loss of sensation alone, whether complete or partial, makes no material
difference to the growth of the nails. How, then, are we to explain the pro-
found alteration produced by division of the ulnar nerves ?

A characteristic instance of this defective growth was seen in Case 63,
where sensation was lost over the full ulnar area (fig. 5, h, p. 71). No
tendons were divided and the following differences must have been due
solely to the consequences of division of the ulnar nerve. In one hundred
and thirty days, during which sensation showed no sign of return, the
growth was as follows : —

Right [affected).

Left [sound)

Index

16 mm.

Middle . .

15 mm.

17 mm.

Ring

11-5 mm

14-5 mm.

Little

10 mm.

14 mm.

But this result, so characteristic of lesions of the ulnar nerve, cannot be
due to any direct effect of the nerves upon the growth of the nails ; for in a
woman, aged 36 (Case 23, Table II., p. 94), in whom the ulnar nerve had been
reunited, the change was equally definite, although all sensation had returned.

1 Reported in full on p. 203, vide also Table IV., p. 100.

182

STUDIES IN NEUROLOGY

But at this time none of the muscles of the hand supplied by that nerve were
acting voluntarily.

Right {affected). Left (sound).

Index
Mddle
Ring
Little

/ mm.
6 mm.
5 mm.

4 mm.

8 mm.

9 mm.
7 mm.

Here the paralysis alone must have been the cause of this difference in
growth, a difference which can be partly prevented by the use of regular
massage. Case 19,^ shows how closely the deficient growth after division of
the ulnar nerve depends upon want of movement. At &st, durmg the thirty-
four days the hand was on splmts, the nails grew to the followmg extent :■ —

Left {affected).

Bight.

Thumb . .

1-5 mm. . .

4 mm.

Index

I mm.

aiiddle . .

2-5 mm. . .

4 mm.

Ring

2-5 mm. . .

4 mm

Little

• 1 on 1

2 mm.

T 11

4 mm
1 . • 1

During a period of forty-nme days, when all sensation was lost over the
ulnar area, their growth was as follows :■ —

Left (affected).

Bight.

Thumb . .

6 mm.

7 mm.

Index

6-5 mm. . .

7 mm.

Jliddle . .

6-5 mm. . .

6-5 mm

Ring

6-5 mm. . .

6 mm.

Little

5 mm.

6 mm.

But durmg this time the hand was massaged regularly three times a week.
Later this treatment was discontinued, and for forty-nine days he relapsed
into the deficient growth so characteristic after division of the ulnar nerve.

Left (affected).

Bight.

Thumb . .

6 mm.

5 mm.

Index

4 mm.

5 mm.

Middle . .

4 mm.

6 mm.

Ring

3 mm

6 mm.

Little

1-5 mm. . .

4-5 mm

The fact that the nails of the middle, ring and little fingers, and not
infrequently that of the index, are affected after injury to the ulnar nerve is
sufficient alone to show that its sensory branches can have little to do with this
characteristic change.

In conclusion, we believe that the most potent cause of diminished growth
in the nails after division of a peripheral nerve is want of movement. ^Vhenever

^ Reported in full on p. 207.

INJURY TO THE PERIPHERAL NERVES 183

the skin becomes insensitive and the injury has not divided tendons or paralysed
muscles, the nails do not show any deficiency in growth. The profound altera-
tion that follows division of the ulnar nerve is produced by paralysis of the
intrinsic muscles of the hand, and stands in no relation to the loss of sensibility.

When the skin of the hand becomes glossy and when hyperalgesia is well
developed, the nails undergo a change radically different from that seen after
division of a nerve. Weir-Mitchell says : " When the depraved nutritive
state (glossy skm) has lasted for some months, the hair commonly disappears
from the fingers affected, and the nails undergo remarkable alterations. . . .
The alteration in the nail consists of a curve in its long axis, an extreme lateral
archmg, and sometimes a thickening of the cutis beneath its extremity. In
other cases a change takes place which is quite peculiar, or which to us at least
was new. The skin at that end of the nail next to the third finger joint becomes
retracted, leaving the sensitive matrix partly exposed. At the same time
the upper line of union of skin and nail retreats into or under the latter part,
and in place of a smooth edge is seen through the nail as a ragged and notched
border."

In the only instance of true glossy skin that has come under our notice
(Case 63) the nails of the little and ring and middle fuigers curved longitudinally
and horizontall3^ They were not ribbed but were thin and exquisitely tender.
The patient was certain that these nails grew faster than those on the sound
hand ; but owing to the shortness of the period during which he was under
our observation before the nerve was divided and sutured, we were unable
to verify his statement by measurement. The remaining instance of hyper-
algesia did not affect the tips of the fingers, and threw no light on this increased
growth of the nails. But whenever a curved nail is growing slowly it is thick
and hard. In the case of L. G. H. (No. 63) the nails were, on the contrary,
smooth and thin, collateral evidence that they were growing faster than
normal.

CHAPTER XV

PARALYSIS AND OTHER MUSCULAR CHANGES

The motor supply of one nerve rarely overlaps that of another, and can
be readily determined by dissection. The examination of cases where a
peripheral nerve has been divided has not led us to doubt the usual teaching
concerning the supply of any of those muscles of the limbs that have come
under our observation. This chapter will therefore be devoted mainly to a
consideration of the time required for the recovery of muscular power, the dis-
appearance of the wasting and the restoration of irritability to the interrupted
current.

Before passing to the results of our observations, we wish to call attention
to some possible sources of error in the methods usually employed to determine
whether a muscle is acting voluntarily.

The little finger is abducted by the combined action of two muscles, the
abductor and the extensor minimi digiti. If the former is paralysed, as is
the case after division of the ulnar nerve, false abduction can be produced by
means of the extensor. The nature of this movement can be at once recognised
by the extension which accompanies it. When the hand is placed flat on the
table the little finger is seen to be raised if the abduction is caused by the
extensor only.

Another fruitful source of error, as pointed out by Beevor (5), is false
abduction of the thumb by means of its extensor muscles. True abduction
of the thumb takes place in a plane at right angles to that of the palm, and
this is the action of the abductor pollicis. But under ordinary circumstances
this muscle acts in combmation with the extensors, and when the abductor
and opponens pollicis are paralysed from division of the median nerve, the
extensor muscles alone can produce some abduction. The true nature of this
movement is betrayed by the impossibility of performing it without extending
the thumb.

In like manner, the movement produced by the opponens can be simulated
by contraction of the flexor longus pollicis and of the adductors of the thumb.
The true mechanism of this movement can be recognised by the flexion of the
terminal phalanx with which it is associated.

The index finger can be abducted slightly by means of its extensor, and this
may cause some difficulty, after division of the ulnar nerve, in determining
whether the first dorsal interosseous is acting.

184

INJURY TO THE PERIPHERAL NERVES 185

Another difficulty in connection with this muscle arises when it is tested
electrically. After the ulnar nerve has been divided the first dorsal inter-
osseous muscle wastes. But in the position of the wasted muscle, contraction
can be frequently obtained by means of the interrupted current. This is
due to stimulation of the first lumbricalis inserted into the dorsal expansion
of the extensor tendon and supplied by the median nerve.

Division of a motor nerve causes immediate paralysis in the muscles it
supplies. But they continue to react to the interrupted current for from
three to five days. After the fourth to the seventh day we obtained no
response to the interrupted current in the muscles of the hand supplied by
the median or by the ulnar nerve. Here our experience coincides with that
of Bowlby (10), who states that he has been unable to obtain any reaction to
the strongest current as early as the third or fourth day after division of the
nerve. Statements assigning a considerably later date are probably vitiated
by the inclusion of cases of injury or incomplete division of a nerve. In about
ten days it may be extremely difficult to obtain any response from the paralysed
muscles by means of the constant current ; or the characteristic sluggish
contraction may begin to make its appearance shortly after all reaction to
the interrupted current has been abolished.

After complete division of the ulnar nerve all the muscles of the hand
become paralysed except the two radial lumbricales and the abductor and
opponens poUicis. The muscles affected waste, and the hand assumes the
appearance so characteristic of this injury. The little finger is abducted and
somewhat over-extended at the metacarpo-phalangeal joint ; the remaining
fingers are slightly extended at the same joint, and are out of alignment with
one another. A striking feature is the profound wasting in the first inter-
osseous space.

In five cases of primary suture of the ulnar where we were able to prove
that the nerve had been completely divided, the period at which motion first
returned to the paralysed muscles was, on an average, 346 days.

It so happened that in each of these cases contractility to the interrupted
current was rediscovered for the first time on the same date as the return of
voluntary power.

Of these five patients, two disappeared before the hand had again become
completely normal in appearance. But in the remainder the wasted muscles
had been restored, and the hand had regained its usual appearance in twelve
months (Case 22, Table II.), twenty months (Case 14, Table II.), and two
years (Case 15, Table II.).

Of all the patients we have examined, in whom the median nerve was
completely divided, we have been able to follow three only to the end.
Voluntary power returned to the outer thenar group of muscles on an average
in 272 days (237, 282, 299). In two instances the first reaction to the inter-
rupted current was noted on the same date as the return of voluntary power ;
in one, it was rediscovered five weeks before any voluntary contraction could

186 STUDIES IN NEUROLOGY

be observed. One patient recovered so completely, that fifteen months after
primary suture no difference could be noticed in the appearance of the two
hands. But, in another instance, some wasting was still visible two and a half
years after suture.^

In every patient watched by us to complete recovery, after coincident
division of the median and ulnar nerves, the wound suppurated to a greater
or less extent. This probably accounts for the considerable diversity in the
time required among the three instances for the return of voluntary power to
the paralysed muscles. But, however these cases differ from one another,
they have one feature in common ; both voluntary power and reaction to the
interrupted current returned earlier in the opponens and abductor poUicis
than in any of the muscles supplied by the ulnar nerve. The period necessary
for the return of voluntary power in these three complete cases was 273, 356,
and 605 days, whilst a response was obtained to the interrupted current in
273, 308, and 728 days respectively.

Among these cases of coincident division of the median and ulnar nerves,
one patient only recovered so completely that no difference could be noticed
between the two hands ; this condition was reached two and a half years after
suture of the nerve. Another patient, in whom the wound suppurated badly
(Case 27, Table III.), still showed some wasting of the thenar eminence and
interosseous spaces four years and five months after the nerves had been
united.

Thus, as far as the muscles of the hand are concerned, it would seem that
voluntary power returns earlier when the median nerve is divided. After
coincident division of both nerves, the opponens and abductor pollicis are
restored more quickly than the muscles supplied by the ulnar nerve.

Out of eleven cases of primary suture after division of one or more nerves
to the hand, in eight the muscles first reacted again to the interrupted current
at the same date on which the first voluntary contraction was observed. In
one instance of division of the median (Case 3, Table I.), and in one (Case 26,
Table III.) where both nerves had been divided, the muscles first responded
to the interrupted current shortly before any volimtary contraction could be
obtained. One case only showed any return of voluntary power before a
reaction was obtamed to the interrupted current.

Voluntary power ultimately returned to all the paralysed muscles in every
patient whom we have observed from the time when the nerves were sutured.

In order to discover if, in some mstances, the paralysed muscles did not
recover, we examined a number of patients in whom primary suture of one
or more of the nerves to the hand had been performed at the London Hospital
before the beginning of our research. Of four cases where the ulnar had been

^ We wish to call attention to a possible source of error after division of the median nerve.
That branch which supplies the muscles of the hand may leave the main stem of the nerve in the
lower part of the forearm, and thus escape injury when the wo mid is at the wrist. We have seen
such a branch uninjured in one instance (Case 5, Table I.) at the operation for primary suture.

INJURY TO THE PERIPHERAL NERVES 187

divided, one showed complete paralysis of all the muscles supplied by that
nerve five and a half years after its suture. All the others had recovered when
first seen by us from two to four years after the injury.

Five of the six patients in whom the median nerve had been divided had
completely recovered when we first saw them two to four and a half years
after suture ; one still showed no return of motor power eighteen months after
the nerve had been reunited.

Thus, we may say that most patients regain voluntary power in the affected
muscles after primary suture of one or more of the nerves of the hand ; but
the strength of the contraction and the ability of the hand not infrequently
remain permanently less than normal.

Primary suture implies the reunion of the ends of a nerve within a few
hours of its division ; the only variable in the case is therefore the period
necessary for the return of function. But secondary suture may be carried
out at the most diverse periods from the date of injury. This involves a second
variable factor ; for it is desirable to determine, if possible, not only the date
of return of function, but also the effect produced upon this return by the
length of time during which the nerve has remained completely divided.

A general statement of the results of secondary suture necessitates an
investigation of numerous instances, but in the majority of patients the nerves
are sutured before the accidental wound has healed, and cases of secondary
suture are rare. We have as yet been able to follow six patients only up to
complete recovery of voluntary power and muscular reaction. Among them
the time at which the ends of the nerve were reunited varied from 15 to 502
days after division.

The following table shows these cases and the time of their recovery : —

Ulnar Nerve.

Period after Division

at which Secondary

Suture was Performed.

Return of

Voluntary

Power.

Return of Reaction

to the Interrupted

Current.

^0.

18 .

23 .

24 .

15 days
28 „
502 „

702 days
408 „
370 „

702 days.
. . 408 „
. . 370 „

Median Nerve.

85 .
12 .
11

66 days
yoo ,, • • • •

816 days
481 „ . .
373 „

635 days
. . 369 „
. . 373 „

It will be noticed that there is no instance among them of that remarkable
recovery of muscular power recorded by Kennedy (58) after secondary suture.
The earliest return of voluntary power occurred in 370 days after the nerves
had been reunited.

We possess among our records one complete case of secondary suture of

188 STUDIES IN NEUROLOGY

the musculo-spiral nerve (No. 43, reported in full on p. 215). Voluntary
power reappeared in the paralysed muscles 272 days after the ends of the
nerve had been reunited. This boy was intolerant of the interrupted current,
and no contraction could be obtained to this stimulus until fifty-eight days
later ; the muscles then reacted well even to weak currents such as he bore
with equanimity.

The external popliteal is not infrequently injured by a crush of the leg,
or as a consequence of fractures below the knee. Such injuries do not usually
cause complete division of the nerve, and in one instance only were we able
to watch the results caused by reunion of the divided ends after complete
section. WTienever the nerve is injured severely, recovery takes place
extremely slowly ; in the only instance where it was completely divided volun-
tary power had not returned to the paralysed muscles three and a half years
after the ends of the nerve had been reunited.

When a nerve is incompletely divided the injurj^ may produce the most
varjdng results upon muscular power and on the reaction to electrical stimula-
tion. In many cases voluntary power may not be lost in the muscles supplied
by the injured nerve, and they may react normally to both forms of electrical
stimulation. Voluntary power may remain, but reaction to the interrupted
current be lost ; the muscles will then respond more readily to the constant
current. The contraction still occurs to the negative pole more readily than
to the positive, but the strength of current necessary to cause contraction is
considerably reduced. This facile reaction to the constant current also occurs
after incomplete division of the nerve when voluntary power is lost, and all
response to the interrupted current is abolished. It is therefore a valuable
indication that the nerve has not been completely severed.

CHAPTER XVI

THEORETICAL

The observations detailed in the previous chapters are so completely out
of accord with any view of the mechanism of sensation as yet put forward
that it will be well to summarise the facts before attempting to co-ordinate
them into a new theory.

It has long been known that, when a nerve to the hand is divided, some
sensibility to pressure with the finger still remains, even in parts insensitive
to the prick of a pin. This fact led Letievant (67) to enunciate his theory of
" supplementary sensation " (sensibilite suppUee). In the early 'sixties, " cette
epoque de foi robuste," surgeons brought forward cases of return of sensation
and motion within a few days, or even hours, after reunion of a divided nerve.
Letievant demonstrated by a series of cases that this so-called return was due
in reality to the retention of sensation over the affected parts. When the
median nerve was divided, stimulation with the feathers of a quill or with
the head of a pin could be appreciated in some cases over the whole area
supplied by that nerve, including even the fingers. But these parts were
entirely insensitive to temperature, and the compass points could not be
discriminated even when 6 cm. apart.

He showed that, after division of the median nerve, the movement resembling
opposition of the thumb was due to contraction of its adductor and flexor
muscles. He also recognised false abduction, attributing it to " Faction du
long abducteur du pouce " (extensor ossis metacarpi pollicis).

On the sensory side, he beaeved the absence of complete insensibility was
due to anastomosing branches and to the conduction of mechanical vibrations
on to neighbouring parts where the nerve end organs were intact.

His observations were correct and his criticisms just. But unfortunately
surgeons failed to appreciate the significance of this work, although ready to
invoke "supplementary sensation," when the condition of sensibility did not
accord with their expectations. Thirty years after the publication of Letie-
vant's book, neglect of his warning has led to the advent of another generation
of robust believers, who report cases where suture of divided nerves has led
to immediate or strikingly rapid return of sensation.

Letievant and his contemporaries knew nothing of afferent fibres running

with motor nerves, and to them the conception of deep sensibility put forward

by us was therefore impossible. But, after Sherrington's demonstration (110)

189

190 STUDIES IN NEUROLOGY

of the existence of such afferent fibres, we were compelled, early in our research,
to examine their function in man ; for such fibres may remain uninjured after
complete destruction of all the nerves to the skin.

This led to the division in one of us of the radial and external cutaneous
nerves and to a series of observations to be reported in full later in conjunction
with Dr. Rivers. The knowledge of the properties of deep sensibility, gained
from this experiment, enabled us to understand the full significance of the
various forms of residual sensation, discovered after division of peripheral
nerves.

Complete division of all the sensory nerves to the sldn leaves the part
sensitive to those stimuli commonly employed by the surgeon as a test for
sensibility to touch.

All forrris of pressure, such as a touch with a pencil or the feathers of a
quill, can be appreciated and localised with considerable accuracy. Two
points applied successively can be recognised, but, if applied simultaneously,
the patient entirely fails to discriminate them, even when the compasses are
widely separated. The denervated part is insensitive to all forms of heat
and cold. Pain can only be evoked by pressure, and then has that peculiar
aching character associated with a crush or contusion.

We have shown that this deep sensibility is restored rapidly, and seems
to reach the hand by way of the tendons and fibrous structures connected with
them. Division of the median nerve without injury to these structures leaves
the response to all forms of pressure almost unaffected.

Clear recognition of these facts is necessary before we can attempt to
explain the condition of cutaneous sensibility after division of a peripheral
nerve. Stimulation can rarely be made without some pressure, but every
stimulus must be of so specific a nature that the pressure element in the
sensation passes into the background. A pin-prick may be appreciated and
localised, but, unless it is recognised as causing pain, its appreciation may
have been entirely due to deep sensibility. To say that " a prick with a pin
was felt and well localised " is no evidence of the presence of cutaneous
sensibility to pain.

We have shown that when a nerve, such as the median or ulnar, is divided,
the area it supplies does not become uniformly insensitive.

All previous observers have stated that sensation is diminished over the
full area usually assigned to the injured nerve, and lost completely over a small
portion only. We have shown that this " diminution of sensation " is, in
reality, a total loss of sensibility to stimulation with cotton wool, to the com-
pass test, and to the painless interrupted current. Moreover, this area of
" diminished " sensation is insensitive to degrees of temperature between
about 22° C. and 40° C, although within its borders ice and water at 50° C.
can be appreciated.

Moreover, if a nerve has been completely severed, recovery of sensation
does not take place, as is usually believed, by a gradual increase in sensibility,

INJURY TO THE PERIPHERAL NERVES 191

beginning in parts where sensation has never been lost entirely ; but the hand
first becomes sensitive to prick and to the more extreme forms of heat and cold.
Only after an interval of some months do the higher forms of sensibility begin
to return.

The intermediate zone and a hand in the first stage of recovery are alike
in their insensibility to cotton wool and to temperatures between about 25° C.
and 40° C. ; the compass test fails utterly, even when the points are separated
to many times the distance necessary upon the normal hand. All the finer and
more delicate sensations involving discrimination and differentiation are
wanting. Alike in these defects, the sensibility of the intermediate zone and
that of the recovering hand resemble one another in the peculiar character
of their response to stimulation. A prick causes immediate withdrawal of the
hand with evident signs of discomfort, and the sensation it produces is badly
localised, radiating widely over the parts affected. Stimulation with tempera-
tures below 20° C. evokes a sensation of cold which radiates widely and is of a
tingling character. If the point of a pin is dragged lightly across the skin from
normal to abnormal parts, sensation changes immediately the line is crossed
at which light touch is no longer recognised. There is no gradual passage
from parts of normal to those of abnormal sensibility ; the line of transition
is abrupt.

But, although the intermediate zone and the hand at the end of the first
stage of recovery resemble one another in their want of response to the more
delicate forms of stimulation and in the wide radiation of any sensation evoked
from them, they differ in one important particular. An intelligent patient is
aware that sensibility is materially diminished, even to the point of a pin, over
the intermediate zone. He speaks of the skin of this area as " numb, but
not dead." But from parts that had reached the end of the first stage of
recovery the response to the point of a pin is greater than that from the normal
skin. A prick causes instant withdrawal of the hand, with evident signs of
extreme discomfort. Ice and water at 50° C. seem respectively colder and
hotter over the affected area than over normal parts of the hand. Sensation
is less acute, but more vivid than that from the normal skin.

Thus the sensibility of the intermediate zone and that of the recovering
hand are similar in kind ; but, whilst the latter reacts more briskly than
normal to its peculiar stimuli, sensation over the intermediate zone is
obviously defective. The intermediate zone, apart altogether from its insensi-
tiveness to light touch, may be rightly spoken of as an area of diminished
sensibility.

This form of sensibility, so characteristic of parts to which sensation is
returning, we call protopathic.

It will be well to formulate the essential characteristics of this form of
sensibility as manifested in a hand that has reached the end of the first stage
of recovery. Every stimulus, to which the part reacts, produces a sensation
that radiates widely and is accompanied by a peculiar tuigling quality. The

192 STUDIES IN NEUROLOGY

point of stimulation is recognised with considerable accuracy in consequence
of the sensibility of the subcutaneous structures to the pressure that neces-
sarily accompanies almost every stimulus. But the specific sensation of pain,
of cold, or of heat, seems to be situated in some remote part, such as the fingers,
or to extend widely over the palm. Sometimes an intelligent patient will say :
" You touched me on the palm, but the prick is all over the fingers." As far
as we have observed, the radiation never spreads to parts over which light
touch is perfect and the compass test gives a normal record ; conversely, a
prick over normal parts does not produce any sensation within a contiguous
area of protopathic sensibility.

Although parts in this condition react more vehemently to painful
stimulation than those that are imaffected, the stimulus necessary to evoke
sensation appears to be greater. When the normal hand is pricked with a
pin, a sensation of sharpness is produced almost as soon as the point touches
the skin. Over protopathic parts the point must be applied more firmly
before pain is produced, and this sensation not only arises more slowly, but
lasts after the stimulus is removed. The widespread, aching pain produced
by a prick of just sufiEicient force to arouse the sensibility of a protopathic
area is more intolerable than the sensation caused by a prick of considerable
violence over normal parts. The patient cries out, and withdraws his hand
rapidly. Thus, although a stronger stimulus is necessary to evoke a painful
response from parts in a condition of protopathic sensibility than from those
where sensation is normal, the discomfort manifested by the patient is obviously
greater.

Temperatures below 40° C. do not, as a rule, evoke a sensation of heat
from parts in this condition, when the patient belongs to the ordinary hospital
class. But, in one of us, the back of the hand, endowed only with protopathic
sensibility, habitually reacted to 38° C. over one small area of maximal
sensibility. Over parts at the end of the first stage of recovery, water at 45° C.
will certainly be recognised as warm during the summer months ; but over the
intermediate zone with its lowered protopathic sensibility, or when the cold of
winter has rendered the affected parts less sensitive, a temperature of 50° C.
may be required before any sensation of heat is produced. Such a tempera-
ture is capable of producing pain, even over the normal hand, and it might be
objected, that the sensation it produces over such protopathic parts is in
reality one of pain rather than of temperature. But the patient states, that
though pain and tingling are evoked by stimuli at this temperature, they are
accompanied by a definite sensation of heat.

An area supplied only with protopathic sensibility reacts more vehemently
than normal parts to all temperatures capable of evoking a response. If a
test tube containing water at 45° C. is moved across the hand from normal to
abnormal parts, it appears to become hotter as soon as the protopathic area is
reached. And yet this same area is totally insensitive to water at 35° C,
which is decidedly warm to the normal hand. Thus, the increased reaction

INJURY TO THE PERIPHERAL NERVES 193

to 45° C. over the protopathic area is in no way due to an increased sensitiveness
to heat as a whole.

This over-action to the more extreme degrees of heat can be well showTi
at a somewhat later stage of recovery. The hand may then have regained some
sensibility to warmth (34° C. to 38° C), but still shows the characteristic
response to prick, and a sharp line of change to the point of a pin dragged
across the skm. If, when the hand is in this condition, a test tube containing
water at 45° C. is passed across the palm, it appears to grow hotter over the
protopathic area. But when the same procedure is carried out with a test
tube at 37° C. it appears to grow cooler as soon as the affected parts are reached.
The recovering parts in this experiment react less briskly to the one tempera-
ture (37° C.) and more briskly to another (45° C.) than parts of normal sensibility.

To cold stimuli, especially when the temperature is below 18° C, the
reaction of protopathic parts is equally characteristic ; no stimulus produces
more striking radiation and diffusion. The sensation of cold appears to extend
widely, or to be situated in some distant parts of the affected area. Moreover,
the reaction produced by temperatures below 18° C. is greater over protopathic
than over normal parts ; the stimulus seems to the patient to be colder.

If the affected part happens to be endowed with hair, it will be found that
many of the hairs when pulled cause pain. This pain is not localised, but
radiates widely. But, in addition, any movement of these hairs, such as is
produced by brushing the part lightly with cotton wool, will cause a sensation
differing from that over normal parts. For not only does it consist of a curious
tinglmg, or formication, but it radiates widely and is frequently referred to
parts at a distance. This sensation can be evoked only by stimulating the
hairs, and, unlike the normal skm, the part becomes entirely insensitive to
cotton wool when shaved.

Whatever may be the stimulus that evokes a sensation from protopathic
parts, that sensation is always characterised by a " tingling " quality and by
defective localisation. So erroneous may be this localisation, that although
the impact of the stimulating body is perceived and localised correctly, the
pain, or the cold, or the tickling of hairs, may be appreciated in some area
far from the point of stimulation.

The return of sensation to light touch brings a gradual diminution in this
tmgling and widespread radiation so characteristic of protopathic sensibility.

Gradually the patient becomes able to distinguish two points of the com-
passes when separated to a distance more nearly approaching that at which
they can be discriminated over the normal skin.

It might be urged that the gradual disappearance of radiation and defective
localisation was due to the steady improvement of protopathic sensibility
comcident with recovery of the nerve. On such a view, the word " proto-
pathic " would be a convenient name for a stage m the recovery of sensation,
but would have no further significance.

But everything seems to point to the introduction of a new factor rather

VOL. I. o

194 STUDIES IN NEUROLOGY

than to the gradual improvement of a function already present. For, before
the advent of light touch, the patient could appreciate correctly the point
which had been pricked, or the area stimulated with ice, by means of the
pressure so produced. But this did not hinder wide radiation of the specific
sensation. This radiation is only brought to an end by the return of sensibility
to light touch and the recovery of power to discriminate two compass points.

All power of localisation present before the return of light touch must
have been due to what we have called deep sensibility. It is conceivable
that the final disappearance of radiation and the other protopathic character-
istics might be due to the development of a new quality that made localisation
in the skin a possibility. This quality would be in some way associated with
the return of sensibility to light touch. But this return could have no direct
effect upon sensations of temperature, and yet one of the most definite features
of this stage of recovery is the appreciation of intermediate degrees of
temperature to which the part in the protopathic condition was insensitive.

Moreover, the return of sensibility to light touch seems so closely bound
up with the recovery of sensation to intermediate temperatures and with the
discrimmation of the compass points that we have united these three factors
under the name of epicritic sensibility.

T\n[iatever the specific nature of the sensations we have grouped under
this name, they are all well localised and their reappearance within the affected
area is accompanied by a coincidental decrease in radiation.

The use of these terms, " protopathic " and " epicritic," would be con-
venient even if they represented nothing but stages in recovery after division
of a peripheral nerve. But we believe that each corresponds to the function
of a distinct system of nerve fibres and end-organs.

In a previous part of this paper (Chapter I) we showed from a series of
cases that the area rendered insensitive to light touch by division of the median
or of the ulnar nerve varied little in extent.

In sharp contrast to this slight variation stood the extreme differences
in extent of the loss of sensation to prick which followed division of either of
these nerves. So greatly did the area of cutaneous analgesia vary in each
individual instance that it was impossible to formulate any general statement
concerning the normal extent of the area rendered insensitive to prick by divi-
sion of the median or of the ulnar nerves. Moreover, the extent of the loss
of sensation to light touch and to prick vary independently of one another.
The most extensive cutaneous analgesia is not necessarily associated with an
increased area of insensibility to light touch. Conversely, when the loss of
sensation to prick occupies but a small extent of the hand, or is confuied
to the fingers, the area insensitive to light touch is not of necessity smaller in
proportion. Tliis want of relation between the extent of the loss of sensation
to prick and to light touch after complete division of a nerve renders it unlikely
that the two forms of sensibility are due to the same anatomical system of
nerve fibres and end-organs.

INJURY TO THE PERIPHERAL NERVES 195

When the ends of a divided nerve have been successfully sutured, proto-
pathic sensibility not only returns first, but the whole of the affected parts
may remain for many months entirely insensitive to all the higher stimuli.
If protopathic and epicritic sensibility were only functional modifications in
the activity of one anatomical system, it would be difficult to explain how the
complete restoration of the one could leave entirely unaffected the extent
of the area over which the other was absent. The improvement should be
general, and should lead to a gradual retreat of the borders of the area in-
sensitive to the higher stimuli step by step with the disappearance of the
cutaneous analgesia. This actually occurs when a nerve has been injured and
not completely divided. After such a lesion no widespread regeneration is
necessary ; the nerve fibres have but to recover their function temporarily
in abeyance. But, after suture of a completely divided nerve, the two systems
of fibres evidently regenerate with, unequal facility, and thus the one form of
sensibility is re-established before the other shows any signs of return. The
results that follow the unaccompanied restoration of protopathic sensation
have been fully described when we considered the condition of a part at the
end of the first stage of recovery.

Protopathic sensibility is restored under conditions which materially hamper
the return of the higher forms of sensibility. The formation of fibrous tissue
between the two ends of a nerve greatly retards the restoration of sensation,
but, when this fibrous tissue is removed at the operation for secondary suture,
it sometimes happens that the extent of the protopathic loss is increased
(Case 11, Case 28). This increase must have been due to the removal of nerve
fibres intermingled with the fibrous tissue, which were capable of endowing
the part with protopathic sensibility. Here a condition capable of preventing
the return of the higher forms of sensation did not form an effectual bar to the
regeneration of the fibres subserving protopathic sensibility.

With two systems of nerve fibres we should expect that occasionally injury
of a peripheral nerve would produce the converse form of dissociated sensibility.
On this hypothesis it is unlikely that the fibres would be distributed uniformly
to every peripheral nerve, and we should find occasionally that a part in-
sensitive to prick reacted to the lightest touch. Such a dissociation is rare, but
seems to exist especially after division of the posterior roots that supply the arm.
In one such instance (Case 53, p. 122) we were able to show that an area in the
region of the deltoid was insensitive to prick and to ice, but was sensitive, even
after shaving, to cotton wool and to the minor degrees of heat and cold. Here,
too, sensation was good, although not perfect, when tested with the compasses.

The opportunity of testing an area of so considerable a size seldom arises,
but in the case of one of us, after division of two nerves in the forearm, a
triangular area insensitive to prick, but sensitive to light touch, made its
appearance in the neighbourhood of the wrist. Here ice and water at 50° C.
were not appreciated, but sensation seemed to be retained to temperatures
between 36° C. and 45° C.

196 STUDIES IN NEUROLOGY

In Case 85, a small patch of dissociated sensation appeared on the back
of the hand m consequence of division of the median and part of the radial
and external cutaneous nerves at the A\Tist. Here the patient could appreciate
stimulation with cotton wool and with \Aarmth, but was insensitive to prick
and to the application of ice.

Thus, in conclusion, we believe that the following reasons render it probable
that what we have called " protopathic " and " epicritic " sensibility depend
on two anatomically^ separate systems of fibres and end-organs.

Firstly, it is difficult to see how else can be explained the want of relation
between the extent of the area rendered insensitive to light touch and that
insensitive to prick after division of a peripheral nerve. Secondly, the com-
paratively early return of protopathic sensibility after suture of a completely
divided nefve brmgs with it no diminution m the area insensitive to light
touch and minor degrees of temperature. AMiereas, if the nerve has been in-
jured, but not completely divided, the two forms of sensibility return step by
step. Thirdly, we have found on rare occasions that, after division of a
peripheral nerve, a small portion of the insensitive area may react to stimula-
tion with cotton wool and to minor degrees of heat, but not to prick or to ice.

We have now reached the conclusion that every part of the limbs and
surface of the body possesses three systems of afferent fibres. The first of
these runs with the motor nerves, and is not destroyed by the division of
all cutaneous sensory branches. These afferent fibres supply the part with
deep sensibility, and are responsible for much of the sensation that remains
after division of peripheral nerves.

They run with the motor nerves from the periphery to the point where
motor and sensory fibres separate, forming the anterior and posterior roots.
Here they join the posterior roots and pass into the posterior columns of the
spinal cord. In the case of the hand, we brought forward evidence to show
that deep sensibility was materially diminished by division of the long tendons
at the \ATist. The afferent fibres upon which this sensibility depends must
therefore have passed from the palm and fingers along the tendons ; they
then join in the forearm, the motor fibres to that muscle of which the tendon
is only a prolongation. If we know the anterior root by which these motor
fibres pass to innervate the muscle, we may assume that the equivalent posterior
root will carry the afferent fibres connected with the tendon and its fibrous
projection. Given the tendons and the aponeuroses which are necessary
for the maintenance of deep sensibility to any part, we can then work out its
segmental innervation.^

The observations detailed in this paper do not permit us to make any more

^ We have spoken throughout as if no fibres existed in the skin concerned with the
conduction of pressure impulses. It must not be supposed that we do not believe such fibres
exist. We are compelled to neglect them because these fibres are probably removed when all
cutaneous sensory nerves have been divided. Since our only knowledge of the properties and
distribution of deep sensibility can be gained from parts that have been deprived of all their
cutaneous sensorj- nerves, any fibres concerned with deep sensibility existing in the skin are
outside the hmits of our method of observation.

INJURY TO THE PERIPHERAL NERVES 197

definite statement with regard to the distribution of these afferent fibres
concerned Avith deep sensibility. The question of the nature and extent of
pain arising in connection with this system must be reserved for a future
communication .

The laws which govern the two cutaneous systems can be laid down with
greater certainty, at any rate as far as the limbs are concerned. In many ways
the supply of epicritic sensibility is the simpler, especially from the peripheral
aspect. We shall therefore begin with the epicritic supply of the arm and hand ;
then we shall consider their protopathic innervation, and, finally, we shall
apply the laws so established to the cutaneous nerves of the leg.

We have shown that the epicritic supply of the median and ulnar nerves
overlaps little on the palm. When the ulnar is divided, the residual
sensibility, maintained by the median, does not extend further on the palm
than a line drawn through the axis of the ring finger ; nor does it occupy more
than two-thirds of that finger. In no instance was the median capable of
supplying epicritic sensibility to the whole of the ring finger after complete
division of the ulnar nerve. Conversely, after division of the median, the
radial half of the palm has in every case been insensitive up to a line drawn
from the cleft between the middle and ring fingers. This boundary has a
sinuous outline, but, roughly speaking, it corresponds to the vertical line just
described. In no instance has the intact ulnar been able to innervate the whole
of the ring finger after division of the median. These two nerves, as far as
their epicritic supply is concerned, cannot overlap one another by the breadth
of a single finger.

In the same way the border on the thenar eminence between the supply
of the median and that of the combined pre-axial group of nerves (ramus
cutaneus nervi radialis and external cuta neous) is singularly constant and
definite. After the median has been completely divided, the borders of the loss
of sensation on the thumb and outer part of the thenar eminence correspond
almost exactly to the radial boundary of the area that becomes insensitive
to epicritic stimulation after destruction of the pre-axial group of nerves in
the forearm.

Whenever the adjacent borders of two anaesthetic areas correspond closely
in this manner, the two nerves by which they are supplied can overlap little
as far as that particular form of sensibility is concerned.

On the back of the index and middle fingers the epicritic supply of the
median overlaps that of the pre-axial group by rather less than three-fourths
of the extent of the basal phalanx.

On the dorsum of the hand, the epicritic boundary between the post-axial
(ulnar and internal cutaneous) and the pre-axial group (ramus cutaneus n.
radialis, external cutaneous and lower external cutaneous branch of the
musculo-spiral) is formed by a line continuous with the axis of the ring finger.

In the forearm a sharp boundary separates the epicritic supply of the
pre-axial from that of the post-axial group on both the flexor and extensor

198 STUDIES IN NEUROLOGY

surfaces of the forearm. The branches of which the pre-axial group is
composed overlap considerably, and destruction of any one of them leads to
no well-defined area of anaesthesia to epicritic stimuli.

Thus, the epicritic supply of the nerves of the forearm and hand overlap
little provided the anatomical branches are grouped as follows : (1) the ulnar
and internal cutaneous, (2) the median, (3) the remainder of the pre-axial
group.

Division of the branches forming any one of these groups will produce an
area of epicritic insensibility, almost exactly corresponding to the extent of
the residual sensation present when that nerve group alone remains intact.
This correspondence between the extent of the area of epicritic anaesthesia
and that of residual epicritic sensibility, show^s that the supply of the nerve
groups cantiot overlap to any considerable extent.

But, when we examine lesions of trunks of the brachial plexus or of the
posterior roots, these firm borders are no longer present. The remaining
epicritic sensibility in the palm extends beyond the borders of either the
median or ulnar nerve, and the area of epicritic insensibility is bounded by no
definite borders.

Thus the supply of the epicritic system seems to be laid down in units that
correspond in the upper limb with certain groups of anatomical nerves. Here
lesions produce well-defined defects in sensation. The nearer we approach
the posterior roots the less definite are the boundaries of the area insensitive
to epicritic stimuli and the greater the overlapping of the injured cords or
roots.

This was the conclusion to which Sherrington (109) arrived from experi-
ments on monkeys. After determining by his method of residual sensibility
the amount of overlapping between the posterior roots that innervate the hand,
he wished to see to what extent this overlapping was represented in the median
and ulnar. " It is then clear," he says, " that in the hand ... of Macaeus
the extent of overlap of the skin fields of the peripheral nerve trunks, even on
the exquisitely sensitive . . . palmar surface is much less than that of the
cutaneous areas of the nerve roots ; it is, in fact, not so great as may be the
overlap of the fields of nerve roots three segments distant from one another." ^

This complete accord between the results of our observations on man, and
those made by Sherrington on monkeys, shows that the stimuli he used
appealed to what we have called the epicritic system.

When we turn to the distribution of protopathic sensibility we come face
to face with an arrangement fundamentally different. Division of the median
or the ulnar nerve produces loss of protopathic sensibility over a comparatively
small area with indefinite borders. The residual sensibility to protopathic
stimuli present after the median nerve has been divided extends, in many
instances, over the whole palm. After division of the ulnar the palm remains

^ Phil. Trans. Roy. Soc, 1898, vol. cxc, p. 109. Compare also the figures on p. 108, which
are wrongly numbered ; the figure on the left of the reader is No. 2, that on the right No. 1.

INJURY TO THE PERIPHERAL NERVES 199

sensitive to such stimuli everywhere, except over the extreme uhiar border.
Moreover, when the trunk of the uhiar nerve was irritated (Case 63, p. 210),
the tenderness spread across the palm to the thumb and base of the index and
middle fingers. The consequences of both division and irritation of these
nerves show that, as far as protopathic sensibility is concerned, they overlap
to an enormous extent.

The anatomical expression of this overlapping is found in the anastomotic
branches which probably exist in order that the fibres subserving protopathic
sensibility may pass from the territory of one nerve into that of the other.
On the back of the hand the ulnar and internal cutaneous extend as far as
a line that corresponds roughly with the tendon of the middle finger. This
post-axial group also supplies protopathic sensibility to the whole of the ring
finger, except about one-third of the radial aspect of the terminal two phalaiiges ;
it also sends fibres to the ulnar half of the basal phalanx of the middle finger.
The careful and laborious dissections of Brooks (12) and Hedon (51) bring
out these points admirably, and show that the branches traced by them
across the usual anatomical borders subserve the overlapping protopathic
sensibility.

On the forearm division of the radial (ramus superficialis nervi radialis) and
external cutaneous produces an area of protopathic insensibility with a w^ell-
defined border on the flexor surface of the forearm. This border corresponds
closely, except at the wrist, with that of epicritic loss ; but at the wrist the
protopathic fibres of the post- and pre-axial groups overlap greatly, and the
loss of sensation to prick is less extensive than that to light touch.

Everywhere in the forearm and hand division of a peripheral nerve causes
loss of protopathic sensation over an area of smaller extent than the accom-
panying epicritic insensibility ; but, as soon as the nerve is injured on the
central side of the brachial plexus, and especially if it be the roots that have
suffered division, this rule may be reversed. The loss of protopathic sensi-
bility exceeds in extent the area insensitive to epicritic stimuli, and the skin
may be in parts sensitive to light touch, but not to prick (Cases 52, 53, p. 122).
The nearer the lesion is situated to the posterior roots the more extensive
and definite is the loss of protopathic sensibility ; the more nearly the injury
divides one of the nerve groups described above, such as the median, the
ulnar, or the pre-axial nerves, the more definite and extensive is the epicritic
loss. It would seem, then, as if each of these peripheral nerves, or nerve
groups, formed a unit of the epicritic system ; the protopathic unit must be
sought in one or more posterior nerve roots.

This does not imply that division of a single posterior root would produce
an area insensitive to protopathic stimuli, but sensitive to light touch and to
the minor degrees of heat and cold. For even from the protopathic aspect,
fibres of any two posterior roots overlap one another especially on the limbs.
But this overlapping is considerably less for the protopathic fibres of any one
posterior root than for those which subserve epicritic sensibility.

200 STUDIES IN NEUROLOGY

From this it follows that the area which becomes totally insensitive to
protopathic stimulation after a peripheral nerve has been divided, represents the
extent of skin supplied by those fibres of one or more posterior roots which run
exclusively in that nerve. For instance, the area of total cutaneous insensi-
bility which follows division of the ulnar, represents that part of the hand
supplied solely by those protopathic fibres of the first dorsal root, which run
in the trunk of that nerve. Every other part of the hand supplied by fibres
that run in the first dorsal posterior root, will remain sensitive to protopathic
stimuli because it is innervated also from the median.

If, then, it should happen that the area supplied by a peripheral nerve
coincided with that of one or more posterior roots, division of that nerve
would produce a patch of total cutaneous insensibility co-terminous for both
epicritic and protopathic stimulation.

The external popliteal, including its lateral cutaneous branch, closely
corresponds to such a nerve, excepting in the region of the knee and outer
side of the foot. Complete division of this nerve produces an area of epicritic
loss, bounded by a line which slants across the shin to a point just in front
of the inner malleolus. In the region of the calf the boundary of the loss of
this form of sensation runs vertically doAMi the leg to the outer side of the
tendo Achillis.

Both these lines also form the boundaries of the loss of protopathic sensi-
bility, so that here we find a remarkable coincidence of the borders of the loss
to protopathic and epicritic stimuli, a condition foreshadowed by the conse-
quences that follow division of the mternal cutaneous in the forearm.

It must not be supposed that we believe that each of these systems has
one set of end organs only, and that each end-organ is sensitive to every form
of stimulus to which that system responds. In a subsequent paper it will
be shown that, as far as protopathic sensibility is concerned, at least three
end-organs exist and each of these reacts only to a specific stimulus. In the
present communication we are dealing only with the distribution of the fibres
that underlie the two main forms of cutaneous sensibility.

In conclusion, we believe that the afferent fibres in the peripheral nerves
can be divided into three systems.

(1) Those which subserve deep sensibility and conduct the impulses pro-
duced by pressure. The fibres of this system run mainly with the motor
nerves, and are not destroyed by division of all the sensory nerves to
the skin.

(2) Those which subserve protopathic sensibility. This system of fibres
and end-organs responds to painful cutaneous stimuli, and to the extremes
of heat and cold. It also endows the hairs with the power of reacting to
painful stimulation and movement.

These fibres regenerate rapidly after the ends of the nerve have been
reunited ; if the operation has been successfully performed sensation begins
to return within from seven to ten weeks.

INJURY TO THE PERIPHERAL NERVES

201

In any peripheral nerve the distribution of the protopathic fibres usually
overlaps greatly the area supplied by the fibres of the adjacent nerves.

(3) Those which subserve epicritic sensibility. The nerve fibres and end-
organs of this system endow the part with the power of responding to light
touch with a well-localised sensation. The existence of this system enables
us to discriminate two points and to appreciate the finer grades of temperature
called cool and warm.

These fibres regenerate more slowly than those which subserve protopathic
sensibility after reunion of a divided nerve, and sensation does not usually
begin to return in less than six months under the most favourable conditions.

The distribution of these fibres in the larger peripheral nerves, such as the
median and ulnar, overlaps little compared with the great overlapping of the
protopathic supply.

SHORT ACCOUNT OF SOME ILLUSTRATIVE CASES.

Case 4. — Division of ike median nene.

A. C, aged 20, cut his left wrist with glass on December 22, 1902. He was admitted
to the London Hospital and seen by one of us five hours after the accident.

A transverse wound was present just above the wrist between
the tendons of the flexor carpi radialis and the palmaris longus.

He was insensitive to all cutaneous stimuli over the darkened
area shown in fig. 34, corresponding almost in extent with the
area anaesthetic to cotton wool and to the minor degrees of
temperature.

The wound was explored an hour later, and the median
nerve fomid to be divided ; no other deep structure was severed.
The wound was sutured, after the nerve had been united with
a catgut stitch.

No diminution in the extent of the area insensitive to all
cutaneous stimuli took place while ho was in the hospital, and
he was discharged on December 31, the wound having healed by
first intention.

By February 4, 1903, the area of analgesia on the palm had begim to diminish in size, and on
March 4, only the terminal two jahalanges of the index and middle fingers and the palmar surface
of the terminal phalanx of the thumb were insensitive to prick and to the more extreme degrees
of heat and cold.

All analgesia had disappeared by July 17, but the area insensitive to cotton wool and the
intermediate degrees of temperatuie remained as extensive, and its borders were as well defined
as on the day of the accident.

Until February 4, the hand and fingers were kept at rest and the nails grew unequally.

Fig. 34.

To show the extent of the
loss of sensation in Case 4 pro-
duced by complete division of
the median nerve.

Left (affected).

Right.

Thumb

5-5 mm.

Index

5-5 mm.

Middle . .

5-5 mm.

Ring

5 mm.

Little

5*5 mm.

202

STUDIES IN NEUROLOGY

He started work on June 3, and used both hands alike ; the nails now grew to an equal extent
on both hands.

Left (affected). Bight.

Thumb . . . . . . 7 mm. . . . . . . 6 mm.

Index
Middle
Ring
Little

6 mm.
0 mm.
6 mm.
6 mm.

6 mm.
6 mm.
6 mm.
6 mm.

By September 6, he could appreciate light touch and water at 22° C. and at 40° C. over the
proximal portion of the affected half of the palm ; over these parts the compass test was good
at 2 cm.

On September 30, the opi^onens and abductor muscles acted volmatarih^ and reacted to the
interrupted current. Cotton wool and the minor degrees of temperature were appreciated over
the whole affected palm on this date, but the fingers remained anjesthetic until November 18.

A definite line of change to prick was present, boimding the old ansesthetic area until June,
1905. By August 21, 1905, this had disappeared, and the compass test Mar- perfect at 1 cm.

Case 6. — Division of the median nerve. Recovery thrown hack by the formation of an abscess
at the site of the healed icound. Trophic disturbances of the skin.

S. H., a barber, aged 21, cut his right wrist with a razor on October 3, 1903. The womid
was explored the following day : the median nerve, the tendons of the flexor sublimis digitorum,

flexor longus poUicis, and sevei'al of those of the flexor profundus,
M I A A A |?| were found to have been divided. The nerve was sutured with

.'II iB i l?\ ^^^^■' *h® tendons with catgut.

On January 13, 1904, when he first came under our observa-
tion, the outer group of thenar muscles was much wasted, but
contracted volmitarily and reacted to a strong interruiited
current.

The skin of the median half of the affected palm was dry

and liarsh, contrasting with the smooth, moist appearance of the

unaffected portion. On the radial side of the tips of tlie index

and middle fingers were blisters ; these he had noticed on wakmg

They had not been present when he M'ent to l)ed, and were caused

Fig. 35.

To show the extent of the
loss of sensation in Case 6.

three mornings previously,
by no knowni injury.

He was insensitive to stimulation with cotton wool, and the minor degrees of temperature
over the area shown in fig. 35. Over the terminal two phalanges of the index and middle fingers,
the palmar surface of the terminal phalanx of the thumb, and the extreme radial border of the
last two phalanges of the ring finger, he failed to appreciate a j)rick, ice, water at 60° C, and
pressure.

On ]\Iarch 30, 1904, we noticed the first sign of recoverj^; the area insensitiA'e to prick and
to the extremes of heat and cold had diminished in size on the index and middle fingers, and had
entirely disappeared from the thumb and ring finger. Up to this date, numerous blisters had
appeared on the analgesic portions of the index and middle fingers. Some had dried, leaving a
mass of thickened epithelium; others had formed shallow ulcers. On March 30, for the first
time, the skin was free from any lesion of this character.

By April 27, 1904, all analgesia had disappeared, and water at 60° C. and ice were everywhere
appreciated.

The hand remained in tliis conchtion, sensitive to prick, but amesthetic to cotton wool, until
August 10, 1904. The borders of the ana'sthetic area were well defined, and within it he failed
entirely to discriminate the two points of a pair of compasses separated for a distance of 2 cm.

Shortly after this visit, an abscess appeared at the scar ; it had been ojiened and had healed

INJURY TO THE PERIPHERAL NERVES 203

when we next saw him on September 21, 1904. We then found that a change had taken place
in the condition of liis aensibihty. He no longer appreciated a prick and the extremes of heat
and cold over the same area, that was insensitive to these stimuli, when we first saw him eleven
months before.

On October 23, 1904, he discovered a blister on the terminal phalanx of the middle finger.
When we saw him next, four days later, it had broken, and a superficial ulcer marked its site.
Sensibility to prick was still lost over the original ai-ea, but he occasionally appreciated ice, and
water at 50° C.

From this time onward, blisters made their appearance at intervals, usually without any
history of injury, and when we saw him on March 30, 1905, the terminal phalanges of index and
middle fingers were still analgesic, and ulcers were present. By July 8, these had healed, and
the appearance of the skin approached the normal ; all analgesia had cUsappeared.

He still showed a definite line of change to prick on the palm, and within the boundaries of
tliis line he was now sensitive to stimulation with cotton wool, and the intermediate degrees
of temperature. But within this area, he was miable to discriminate two i)oints at a distance
of 3 cm.

Case, 29. — Injury to the median nerve, produced hy a cut at the wrist. Simultaneous return of
the two forms of cutaneous sensibility.

On September 20, 1902, whilst loading a van, G. B., aged 27, slipped and cut his left wrist on
a broken bottle. He came to the London Hospital at once, and was seen by us, one and a half
hours after the accident. He complained of " pins and needles "
and " numbness " of the thumb, index, and middle fingers,
which had been present since the injury. The wound was
oblique, running from the tendon of the flexor carpi radialis,
close to the fold of the wrist, upwards and ulnarwards for a
distance of IJ ins. (4 cm.).

The opponens and abductor muscles of the thumb were
acting well. He was unable to appreciate light touch over the
full median area on the palm and fingers. Sensation to prick Yig. 36.

and to the extremes of temperature was abolished over the 'Jq show the extent of the loss
palmar surface of the index and middle fingers and over an of sensation in Case 29.

area on the palm at their base {vide fig. 36). Over the dorsal

surface of the two terminal phalanges of the middle finger, the ulnar half of the terminal phalanx
of the index and the extreme radial border of the ring fingers, sensibility to prick was also
destroyed.

The wound was explored one hour later by one of us, and the median nerve was found to have
been injured ; it was swollen, and had been cut into on its ulnar side. The tendon of the flexor
sublimis chgitorum going to the index finger was also divided. After suture of the tendon, the
womid was closed and healed by first intention.

On October 22, analgesia was present over the index and middle fingers onlj", and he was able
to appreciate light touch over the proximal part of the palm, both forms of sensation returning
together in the manner usual after incomplete division of a nerve. The abductor and opponens
poUicis muscles were wasted, but acted readily ; they did not react to the interrupted, but reacted
normally to the constant current.

By February 11, 1903, he could apjDreciate a prick everywhere, except over the terminal
phalanx of the index and middle fingers : light touch was lost over these two fingers only and the
palmar surface of the thumb. All the nmscles reacted perfectly to the interrupted current and
were no longer wasted.

On July 12, the last occasion on which we saw him, he was able to appreciate a prick everj'-
where, but the last two phalanges of the index and middle fingers and the palmar surface of thie

204 STUDIES IN NEUROLOGY

thumb were still insensitive to light touch and the minor degrees of temperature. To the compass
test at 2 cm., he showed the phenomenon of " double ones " to perfection.

Case 82. — Division of the median nerve. Imj)rovement after five years.

J. R., a youth of 16, cut his left wrist with glass on February 20, 1897. He was admitted to
the London Hospital the same day, and the median nerve was sutured. The wound suppurated
and did not finally heal for over four months.

He first came under our observation on January 29, 1902, complaining that " numbness ''
was still present in the index and middle fingers.

The whole of the affected hand was of a bluish colour, and seemed undoubtedly colder to the
touch than the sound hand. The outer thenar group of muscles was slightlj- wasted, but was
acting feebly, and reacted to a strong interrupted current.

The last two phalanges of the index and middle fingers on their dorsal and palmar aspects
were insensitive to prick, to ice, and to water at 50° C. Over the usual median area on the palm
and the extreme rachal border of the ring finger, light touch, the minor degrees of teiriperature
and the interrupted current, applied with no iron in the circuit, were unappreciated. Within
this area, he failed to distinguish the points of the compasses, even when separated to a distance
of 3 cm.

By August 24, considerable improvement had taken place. There was now no change in the
appearance of the skin, all muscular wasting had disappeared, and the contraction evoked by
the interrupted current was normal. Analgesia was jiresent only over the terminal phalanx of
the middle finger on its palmar aspect. Light touch and the minor degrees of temperature were
appreciated over the palm of the hand. Considerable improvement had taken place in his abiUty
to distinguish the compass points; he was now perfect at 2 cm., and his answers at 1-5 cm. were
good.

By November 16, all analgesia had disappeared, and he could appreciate light touch and the
minor degrees of temperature over the whole of the affected parts. This area was bounded by a
line of change to prick presenting the usual characteristics ; no further improvement had taken
place in his ability to appreciate the compass test.

When we last saw him, on January 25, 1903, the condition of the hand remained the same;
the blueness and coldness which were present when he first came under observation had dis-
appeared, and had not returned with the advent of winter.

Case 11. — Division of the median nerve. Trophic changes consisting of blisters, ulcers, and
necrosis of the terminal phalan.v of the middle finger.

D. J. T., a stonemason, cut his right wrist with glass in May, 1901. The wound was sutured
at once without an anasthetie.

He first came imder our observation on November 27, 1901. An oblique scar ran upwards
towards the ulnar side across the lower third of the forearm, from the tendon of the flexor carpi
radialis almost to the flexor carpi ulnaris.

The index and middle fingers were the seat of ulcers Avhich had developed as the consequence
of infection of what he called " water blisters." On the radial side of the distal phalanx of the
index finger, distinct loss of tissue had been produced by a small deep ulcer with indurated edges.
On the palmar surface of the same finger were two superficial ulcers, surrounded by a fringe of
skin representing the blister from which they had originated. A small blister was pjesent on the
dorsum of the second phalanx of the middle finger.

The outer part of the thenar eminence was wasted, and the abductor and opponens pollicis
were not acting; these muscles did not react to the interruj^ted current and reacted in a typicall.y
sluggish manner to galvanic stimulation.

Light touch was lost over the median half of the palm; the palmar suiface of the thumb.
Index and middle fingers, and the radial border of the ring finger, were insensitive to this form of

INJURY TO THE PERIPHERAL NERVES 205

stimulation. The last two phalanges of the index and nearly the whole of the last two phalanges
of the middle finger were analgesic.

He remained at his work until ]\Iay, 1902. During this time the "trophic" changes in
liis fingers became more pronounced. On April 0, 1902, the last two phalanges of the index
and middle fingers were enlarged and the skin thickened. The tip of the index finger was
occupied by an ulcer; its nail was represented by a rough, irregular mas.s. The nail of the
middle finger had been cut away to expose an ulcer occupying the tip of the finger, and the
nail- bed.

The area of loss of sensation to light touch and to prick remained unchanged on May 14.
Two days later, Mi\ Eve exposed the nerve and found that it had been comr>letely divided ; the
ends were lying about 3 cm. apart, rmited by fibrous tissue. They were freshened and reunited,
and the wound healed by first intention {vide fig. 7, B, p. 77).

During his stay in the Hospital, the ulcers on the index and middle fingers healed, and the
skin regained its normal appearance. He started work again during the last week in July, and
a week later a " blood blister " appeared on the tip of the middle finger. By August 6 this had
become a shallow ulcer surrounded by thickened epithelium, and on the radial side of the finger
was another small dry blood blister. He remained at his work, and the condition of the middle
finger became worse; necrosis of the terminal pha,lanx supervened, necessitating amputation
through the second phalanx on November 4.

On December 21 the area of analgesia had become smaller. The general nutrition of the
fingers had improved, but there were still small ulcers on the index and middle fingers within
the analgesic area.

By January 2.5, 190-3, a prick, ice, and water at 40° C, could be appreciated everywhere
within the affected area. All the ulcers had healed, and no further trophic changes made their
appearance, although he continued his work as a stonemason.

The opponens pollicis acted voluntarily and responded to a strong interrupted current on
May 24, 1903.

The hand remained sensitive to prick and the extremes of temperatuie, but insensitive to
light touch, and water at 22° C. and 38° C, until January 31, 1904. On this date, the borders
of the anaesthetic area were as well defined as immediately after suture.

When we again saw him, on April 10, he could appreciate light touch and the minor degrees
of temperature everywhere over the affected hand. A definite line of change to \iv\ck was p? esent,
and two points were badly discriminated at 2 cm. He remained in this condition, until we
finally lost sight of him in March, 1905.

Case 64. — Incomplete division of the median nerve. .Recovery of the hvo forms of sensibility
pari passu. Trophic changes of the nails.

G. L., aged 13, cut his right wrist with glass in August, 1901. The wound was stitched without
an anaesthetic, and the condition of the median nerve was not explored.

He came under our observation on November 4, 1901, comj^laining of " sore nails."

Ever since the accident he had noticed numbness of the hand, and for a month the nails had
been '" sore." Three weeks before we saw him, the nails of the index and middle fingers
" came off."

A transverse scar w'as present over the situation of the median nerve, 2-5 cm. above the fold
of the wrist. The outer group of thenar muscles was wasted, but acted voluntarily and responded
to stimulation with the interrupted current. The terminal phalanges of the index and middle
fingers were bulbous, the nails had been shed, and the nail-beds had become ulcers with pro-
tuberant granulations forming their floor. The nails of the thumb, ring, and little fingers showed
no obvious abnormality.

Cotton wool, the interrupted current generated without iron in the circuit, and the minor
degrees of temperature, were unappreciated over the full median area. Sensibility to prick was
lost over the terminal two phalanges of the index and middle fingers. He entirely failed to

206 STUDIES IN NEUROLOGY

discriminate two points when separated for a distance of 2 cm. ; on a similar portion of the sound
palm he made no mistakes at 1 cm.

By February 26, 1902, the area of loss to cotton wool, the interrupted current, and the minor
degrees of temperature, had retreated to the fingers, but the terminal phalanges of the index
and middle fingers were still insensitive to prick. He had imjoroved greatly to the compass
test, and could discriminate the two points at 2 cm. correct!}' over the affected palm. The nails
had begun to grow, and the nail-beds were no longer ulcerated.

All analgesia had disappeared on April 16, 1902, but he was still insensitive to stimulation
with cotton wool and to the minor degrees of temperature over the last two phalanges of index
and middle fingers. A well-marked line of change to prick was present on the palm and on the
dorsal surface of the index and middle fingers, boimding the old area ana?sthetic to cotton wool.
Within this area he appreciated two points separated to a distance of 1'5 cm. After this date
he changed his address and we were miable to see him again.

Case Z^.— Injury to the forearm ; Volhnann's contracture. Implication of the median nerve
in scar tissue.

H. E. T., aged 20, fell while playing football on December 26, 1903, and injured his left arm.
He was taken at once to an infirmary and his forearm put up in internal and external splints.
When these were removed a week later, " a long black bruise " was foimd over the anterior
(flexor) surface of the forearm and a smaller one on the dorsal surface near the wrist. Soon " the
bruise began to take a bad turn," the skin broke, and an ulcer appeared, which did not heal for
over three months. Fourteen days after the accident '" the arm was rebroken and set in a
special splint so that the ulcer could be dressed." His forearm remained in sjilints for three
months, and when these were removed, he noticed that the fingers were numb and becoming
bent.

When he came under our observation on July 2, 1904, an adherent scar marked the site of
the ulcer on the anterior surface of the forearm ; over the lower end of the radius, a scar marked
the site of the smaller ulcer which had been present there. All the movements of his forearm
were free, excepting supination, which was slightly limited. The seat of the fracture was marked
by no bony thickening or deformity.

The hand was held a little flexed at the wrist, with the fingers and thumb slightly flexed into
the palm. On extension of the wrist, the fingers could not be brought into line with the palm,
but when the wrist was flexed they could be almost fully extended. He thus showed the signs
of Volkniann's contracture in a slight degree.

The fingers of the aflected hand were tapering, and the skin of the palm and fingers smooth,
that of the latter being of a reddish blue colour. A blister, for which he could not account, was
present on the palmar surface of the terminal phalanx of the index finger. All the nails of the
affected hand " were growing more slowly " than those on the sound side, and showed marked
transverse ridges.

The intrinsic muscles of the hand were wasted, but acted voluntarily, and reacted to the
interrupted current, with the exception of the abductor and opponens pollicis.

He was insensitive to all forms of cutaneous stimulation over the last two phalanges of the
index and middle fingers. Light touch and the minor degrees of temperature were not appreci-
ated over the full median area ; this was well defined, except at its proximal border. Over the
distal portion of the affected part of the palm, he failed to discriminate two points separated for
a distance of 3 cm., but over the proximal portion, the formula yielded at this distance was good
(^1 7E 3w )• I^PSP touch and the vibrations of a tuning-fork (C 128) were recognised over the whole
of that portion of the hand which was analgesic.

We next saw him on July 24, 1904. During the three weeks that had elapsed, he had received
no treatment of any kind, and the nails of the affected hand had grown more slowly than those
on the sound side.

INJURY TO THE PERIPHERAL NERVES

207

Thumb
Index

Middle

Ring

Little

Left (affected)

3 mm.

2-5 mm.

3 mm.

EigJit.
4 mm.
4 mm.
4 mm.
4 mm.
4 mm.

The appearance of the hand remained the same, but all the muscles now responded to the
interrupted current and the outer thenar group reacted to the constant current at 2 mA. with a
brisk contraction, K.C.C. appearing before A.C.O.

On August 11, IMr. Dean explored the median nerve in the forearm. The fibrous tissue com-
posing the scar passed deeply, and was adherent to the periosteum of the ulna. In this mass
the median nerve was embedded ; it was freed and the wound
closed. Healing took place by first intention.

The first effect of the operation was to throw back the
sensory and motor condition of the hand. The loss of prick
became as extensive as when we first saw him, and the abductor
and ojaponens muscles lost their reaction to the interrupted
current. Xo improvement took place for about two months ;
then both forms of sensation began to return together, and by
the end of Xovember, 1901, were lost over the index and middle
fingers only. All analgesia had disappeared by February 26,
1905, leaving the terminal phalanges of the index and middle
fingers still insensitive to light touch and the minor degrees of
temperature. By this date the abductor and opponens muscles
had regained their reaction to the interrupted current.

As the result of regular massage, the contracted condition of
his fingers had improved considerably and was hardly noticeable
on August 27, 1905. At this time he could appreciate light
touch and the minor degrees of temperature everywhere, and
was perfect to the compass test at 1*5 cm.

Case 19. — To show the effect of surgical division of the ulnar
nene at the elbow upon deep sensibility and cutaneous sensation of
the hand.

Fig. 37.

To illustrate Case 19.

A shows the area 'of insensi-
bility to light touch and to the
intermediate degrees of heat
and cold present before the
operation.

B shows the loss of sensation
which followed division and
reunion of the divided ends of
the ulnar at the elbow.

L. C, a tailor, aged 36, came under our care on June 8, 1901.
He complained of weakness of the hand, and of pain in the ulnar
side, especiallj" troublesome while at work. These symptoms had
been present for seven months, and were increasing in severity.

He was unable to appreciate light touch over the full extent of the ulnar area (fig. 37). He
could appreciate a prick everywhere, but ice, and water at 30' C. were onlj' recognised over the
proximal portion of the palm.

The hand was in the typical ulnar position ; all the muscles in the forearm and hand supplied
by the ulnar nerve were paralysed and much wasted. They did not react to the interrupted
current, but responded to galvanic stimulation with a sluggish contraction.

Pronounced changes were present in the lower end of the humerus. The carrying angle of
the forearm was much diminished and the internal condyle enlarged and irregular. A swelling
was present on the ulnar nerve where it passed between the olecranon and internal condyle, but
the nerve could not be displaced. The movement in the elbow joint was surprisingly good,
supmation alone being slightly limited. He was not aware of the deformity, and no history
could be obtained of any injury during childhood.

From our examination we concluded that the original injury had been a separation of the

208 STUDIES IN NEUROLOGY

lower epiphysis of the humerus in early life. It seemed probable that the nerve had been injured
as the result of long-continued pressure from the deformed internal condyle. In accordance with
this diagnosis, the ulnar nerve was exposed by one of us at the elbow on Jirne 17, 1901. In this
situation about IJ in.s. (4 cm.) of the nerve was hard, fibrous, and swollen; If ins. (15 cm.) of
the nerve, including the swelling, was removed, after a groove had been made in the bone to
prevent the recurrence of the pressure; the ends of the nerve were then sutured. The wound
healed bj' first intention.

This oiieration chd not increase the area within which he was unable to appreciate light touch,
but the extent of the area insensitive to prick was greatly enlarged (tig. 37, n). Deep touch,
tested with the head of pin, could not be appreciated over an area a little smaller in all directions
than that for loss of prick. The vibrations of a tuning-fork (C 128) evoked no sensation over
the little finger.

By September 14, the analgesic area had diminished considerably in size, and on December 21
occupied the little finger only. Deep touch and the vibrations of a tuning-fork (C 128) were
recognised everywhere by May 17, 1905. On August 16, all analgesia had disappeared, and ice
could be appreciated over the whole affected area, but he was unable to recognise water at 50" C.
over the little finger. The borders of the area insensitive to light touch remained as definite as
immediately after section of the nerve.

Case 83. — Excision of a portion of the ulnar nerve in Ihe forearm.

In August, 1899, Ernest C, aged 27, cut his wrist severely as he was opening a window. The
wound was not stitched, but it healed in a week. About ten days after the accident, pain of a

neuralgic character started in the scar, and at last became so

troublesome that, in October, 1899, the wound was explored in

St. Thomas's Hospital. As the pain did not decrease, he again

entered the Hospital on November 30, and on December 21 the

ulnar nerve was stretched at the wrist. In February, 1900, the

nerve was again explored and freed from cicatricial tissue. As

the pain was not materially relieved by these operations, he

entered Guy's Hospital in November, J900. Here the nerve

Fig. 38. was first stretched, then divided, and, finally, on two separate

To show the loss of sensation occasions, a considerable portion was removed in the forearm.

produced in Case 83 by excision ^^e saw him first on November 20, 1901; at that time the

of a portion of the ulnar nerve , , , i , , , , , i . . . j.

in the forearm whole hand was wasted, except the muscles over the outer part

of the thenar eminence. The fingers were maintamed in the
position typical of ulnar paralysis. The little finger was blue and cold, and the nails of all the
fingers were curved in both directions.

He complained of pain starting over the metacarpal bone of the little finger and travelling
along the ulnar side of the hand to the scar on the ulnar aspect of the forearm. This jjain he
described as neuralgic and shooting in character, not constantly present, and ceasing for forty-
eight hours at a time. It was worse in cold weather, and could be started by pressure upon
the scar.

Deep touch was lost over the terminal two phalanges of the little finger and over a small area
on the ulnar border of the hand. All other forms of sensation Mere absent over the darklj' shaded
portion in fig. 38. Cotton wool was not apjireciated over the area enclosed within a single line,
and these parts were also insensitive to the interrupted current produced without iron in the
cii'cuit and to intermediate degrees of heat and cold. Localisation was extremely defective
over the intermediate zone that lay between the border of loss to light touch and that of complete
analgesia. Within this zone, the patient was unduly sensitive to all painful stimuli.

The whole of the intrinsic muscles of the hand, excepting the abductor and opponens pollicis,
were paralysed, and did not react to the interrupted current. They were so jirofoundly wasted
that we were in doubt whether anj' reaction was present to the constant current.

INJURY TO THE PERIPHERAL NERVES 209

Case 3'i. — Partial division of the ulnar nerve. Rapid return of both forms of sensibility.

C. T,, aged 28, jDut his left hand through a glass window on March 4, 1905, cutting the wrist.
He immediately felt '" pins and needles " in all the fingers of the affected hand.

He came to the London Hospital and the wound was explored four hours after the accident.
The ulnar nerve was found to have been cut into below the pomt where the dorsal branch was
given off, and the tendon of the flexor carpi ulnaris had been completely divided. Both nerve
and tendon were sutured.

When we saw him on April S, the womid had healed by first intention, leaving an oblique
scar, running from the extreme ulnar border of the wrist upwards and radialwards. The hand
was in the position characteristic of ulnar paralysis, and none of its muscles supplied by the
ulnar nerve were acting with the exception of the first dorsal interosseous. Stimulation with an
interrupted current failed to elicit any contraction from these muscles.

Sensibility to light touch and to the intermediate degrees of temperature was lost over the
area usually insensitive to these stimuli after division of the ulnar nerve below its dorsal branch.
He was unable to api^reciate a prick and the more extreme degrees of temperature over the
palmar surface of the little finger.

By June 17 the wasting of muscles had almost disappeared, but the hand still retained its
abnormal position ; all the muscles were acting and responded normally to stimulation with the
interrupted and with the constant currents. The analgesia had retreated to the terminal jihalanx
of the little finger on its palmar aspect, and he could appreciate touches with cotton wool over
the dorsal surface of the little finger, the area on the palm remaining as definite as when we fir.st
saw him.

On August 20, cotton wool, and water at 24° C. and at 34° C. could be appreciated every-
where within the affected area; but a line of change to prick marked orit the old anyesthetic
border on the palm and on the dorsum of the fingers. Over the palm to the ulnar side of this
line the compass test gave the following results : 2 cm. g { 7 e 3 w > ^ '^™- 2if^7^- Over a similar
portion of the sound hand no mistakes were made with the points 1 cm. apart.

On May 6, 1905, all muscular wasting had disappeared, and all the intrinsic muscles of the
hand were acting well, but the little finger still remained a little abducted and extended at the
metacarpo-phalangeal joint.

The hand was sensitive to all stimuli, but the line of change to prick was still present, and he
showed no further improvement to the compass test.

Case 24. — Division of the ulnar nerve below its dorsal branch. Complete separation of the ends
for a year and four months. Degradation of sensibility in cold weather.

Edith A., a girl of 17, cut her right wrist with a fragment of a broken bottle on March 7, 1902.
The wo mid was explored and the two ends of the tendon of the divided flexor carpi ulnaris were
said to have been sutured ; the condition of the ulnar nerve was not investigated. The wound
healed by first intention.

She came under our observation on May 28, 1902, complaining of numbness of the ulnar side
of the palm and inabifity to straighten her fingers. She was an anaemic girl with well-marked
signs of congenital syphilis.

A semilunar scar was present, 4 cm. above the fold of the left wrist, running with its convexity
downwards from the inner side of the tendon of the flexor carpi ulnaris to the palmaris longus.
The hand was held in the position typical of ulnar paralysis ; the inner group of thenar muscles
and the interosseous spaces were wasted, and all the intrinsic muscles of the hand supplied by the
ulnar nerve were paralysed and failed to respond to the interrupted current.

She was unable to appreciate light touch over the area in fig. 39 ; the radial boundarj^ of this

area was well defined, but that on its ulnar side merged gradually into the normal sensibility of

the dorsum of the hand. Within this area of loss of light touch on the palm was a small oval

area where she was insensitive to prick. Ice, and water at 00° C. were recognised except over the

VOL. T. P

210

STUDIES IN NEUROLOGY

palmar surface of the little finger and within the area of loss of sensation to prick. She failed
to discriminate the two points of the compasses within the area insensitive to light touch, but
sensitive to prick, when the points were separated for a distance of 2 cm. On the similar portion
of the sound hand, no mistakes were made at 1 cm.

When we next saw her, on July 11, sensibility to prick was everywhere present, and ice, and
water at 60° C. were well recognised over the whole affected area. From this time, her power to
appreciate temperature deteriorated ; on August 8, water at 60° C. was nowhere recognised, and
ice was only appreciated on the palm, when the test tube was laid longitudinally and allowed to
remain in contact with the skin for some seconds. By Xovember 14, ice was only appreciated
over the proximal portion of the palm, although a prick was readily recognised everywhere.

The hand remained in this condition imtil March 9, 1903. On this date, great diminution
in her power of appreciating prick was noticed, and by May 13 the area of analgesia almost corre-
sponded with the area of loss of light touch. Thus it remained
until July, varying, within small limits, from time to time
(fig. 39, B).

On July 22, 1903, the condition of the nerve was explored
by one of us. It was found to be divided below the point
where its dorsal branch is given off, and a remarkable condition
was present, effectually preventing all chance of union between
its two ends. On tracing the upper portion of the nerve down-
wards, it was seen to bifurcate ; its inner portion had been
p n rt united to the upper end of the divided tendon of the flexor

• [1 ^1' f] A carpi ulnaris, its outer to the lower end of the same tendon.

■[ ¥ -1l /9 f^s ^ll^i i8 ^^® lower end of the nerve had been sutured to the divided
W y I \Y- '■••.y tendon of the flexor subhmis going to the little finger. The
m / \ I nerve was reunited after its ends had been freshened.

Z/ y \ V This operation produced no immediate alteration in the dis-

j / B \ f tributionor extent of the loss of sensation. On January 14, 1 904,

all analgesia had disappeared, but she failed to recognise ice over
an oval area on the palm, corresponding to that present when
we saw her first. Water at 60° C. produced no sensation of
warmth over an area almost as extensive as that of the loss of
hght touch. She could appreciate ice everywhere on IVIarch 30,
but even on this date water at 60° C. produced no sensation of
warmth over the whole affected area, and it was not mitil
June 21 that she was able to recogm'se this form of stimulation.
Sensibility to light touch began to return over the proximal portion of the palm on March 30,
1904, and by June 27 was lost only over the little finger. It had completely returned by Sep-
tember 21, leaving a well-marked line of change to prick. But on this date water at 40° C. and at
20° C. failed to evoke any sensation of temperature within the line of change, and it was not
until May 31, 1905, that these minor degrees were recognised.

On August 16, 1905, the line of change to prick was still present. The compass test was
perfect at 2 cm., poor at 1-5 cm. ; and at 1 cm., out of ten stimulations with two points, a correct
answer was given on two occasions only.

On July 27, 1904, the first dorsal interosseous muscle responded to the interrupted current,
and acted voluntarily. She is now (August, 1905) able to contract all the affected muscles feebty.

Case 63.— Bullet wound of the ulnar nerve in tlia forearm. Partial loss of sensation over the
ulnar area. Widespread hyperalgesia. Resection and reunion of the two ends of the nerve. Dis-
appearance of all hyperalgesia.

On July 22, 1901, L. G. H., aged 26, was wounded at Tweefontein ; the bullet ricochetted
from the butt of his rifle and entered his forearm on the ulnar side in front of the bone, 4J ins.

B \

Fig. 39.

To illustrate Case 24.

A shows the area of loss of
sensation present when the
patient first came under our
notice in May, 1902.

B shows the loss of sensation
which preceded and followed the
operation in July, 1903.

INJURY TO THE PERIPHERAL NERVES

211

(11'5 cm.) below the irmercondyle of the humerus. It passed across the arm, and was extracted
from the radial side eight hours later. When hit, he was retiring with his rifle " at the trail,"'
and it fell from his hand. A severe tingling sensation appeared at once, and he could neither
open nor close his hand. After he had been in hospital three weeks, his hand became more
painful, and about four weeks after the injury, the excessive sweating and the change in the
appearance of the hand was first noticed. During the last two months of IflOl, the pain steadily
increased ; it was worse in a warm room, but if he could keep his hand in cither hot or cold water,
the throbbing pain ceased. The pain did not keep him awake at night, and never extended higher
in the forearm than the wound. The nails began to grow fastei- than on the sound hand, and
that of the little finger grew faster than any other.

Owing to the kindness of Professor Barker, we were permitted to see this man in University
College Hospital on January
26, 1902. ^pl^ ^^^

He lay in bed with his
arm raised, with the radial
side of his hand resting on
the pillow, so that nothing
was in contact with the ulnar
half. He was in evident
distress, and anxious lest his
hand should be touched.

The radial palm and ulnar
aspect of the thumb, index,
and middle fingers were
covered with heavy beads of
sweat such as is rarely seen
upon the hand, even in a
Turkish bath, and the skin
over these parts had a soft,
sodden feeling, as if from
fomentations. The ulnar half
of the palm and the palmar
aspect of the little finger were
drJ^ The whole hand on the
palmar surface was smooth
and of a pinkish-blue colour ;
markings were not absent,
but they were less numerous

and less deep than on the normal hand. On the dorsum the skin was but little affected, but over
the dorsal surface of the fingers, particularly over the last two phalanges, the skin was thin and
shiny. All the fingers and the thumb tapered from the base upwards, whereas on the somid
hand they were more spatulate in form. The nails were curved horizontally and longitudinally,
and those of the little, ring, and middle fingers were so painful and tender that he dared not
cut them.

He complained of spontaneous throbbing pain mostly in the little, middle, and ring fingeis:
occasionallj^ the pain invaded the index finger, and it was almost always present over the palmar
aspect of the terminal phalanx of the thumb. This pain never extended above the wrist, and did
not affect the dorsum of the hand.

He was insensitive to. cotton wool over the ulnar half of the hand, over the little finger, and
over the ulnar half of the ring finger (fig. 40, b). The interrupted current, generated without iron
in the circuit, was not appreciated over the same area. When V6 cm. apart, the two points of
the compasses were wrongly appreciated eight times out of ten over the ulnar half of the palm.

To illustrate Case 63.

A shows the area which was intensely hyperalgesic to all cutaneous
stimuli causing pain.

B shows the extent of the loss of sensation to light touch when
the patient first came under our observation.

C shows the extent of the loss of sensation after excision of a
portion of the ulnar nerve and reunion of the divided ends by means
of a graft.

212 STUDIES IN NEUROLOGY

Over the radial half of the affected band and over the ulnar half of the normal hand, tliey were
not only perfect at this distance, but were recognised without uiistakes when 1 cm. apart.

The whole of the palm of the hand was profoundly hyperalgesic, and if the point of a pin was
dragged bghtly from the radial side of the thenar eminence towards the ulnar half of the palm
he cried out at once that it caused excessive pain when the border marked in fig. 40, A, was passed.

Within the area included by this line, picking up the skin or stimulation with the blmit head
of a pin caused intense pain. I'he borders of this hyperalgesia were difficult to define on the
dorsum of the hand, but it seemed to occupy the ulnar half and the whole dorsal surface of the
little, middle, and ring fingers. The index finger was not affected, excepting at its extreme
base on the ulnar side. Ice, and water at 55° C. were correctly appreciated everywhere. No
part of the hand was insensitive to pressure, and within the hyperalgesic area it was uniformly
disagreeable.

All the interosseous spaces were profoundly wasted; the muscles of the thenar eminence
supplied by the median were miaffected, and he could abduct and oppose the thumb normally.
Abduction and adduction of the fingers were impossible; they were out of alignment, and the
ulnar two lumbricales were not acting. The thenar muscles supplied by the median nerve
reacted well to the interrupted current ; but he could stand no current sufficiently strong to test
the reaction of the interossei.

On January 30, 1902, Professor Barker exposed the ulnar nerve. The lower end was easilj'
found and was traced up into a mass of firm fibrous tissue where it disappeared ; the upper end
was lost in the same dense tissue. The two ends were at least 1 cm. apart, and were not in the
same direct line. The bullet had apparently injured the nerve in its passage across the limb,
and its track was represented by the dense fibrous tissue in which ended both the upper and the
lower portions of the nerve; 1 cm. was removed from the upper portion, and the lower end was
divided at different levels until healthy nerve fibre^s were reached. After the track of the nerve
had been cleared from fibrous tissue, the two ends were so widely separated, that it was deter-
mined to fill the gap with the sciatic nerve of a freshly killed cat. To .'5 cm. of this nerve the
upper and the lower ends of the ulnar nerve were sutured by means of linen thread, and the
forearm was bandaged to a splint with the hand midway between flexion and extension.

He was kept under morphia mitil the morning after the operation. When he recovered
consciousness, he suffered from a good deal of pain in the wound, but all pain and tenderness had
left the hand. On February 2, lie would permit the hand to be manipulated, and pressure or
picking up the skin failed to produce any discomfort.

The whole of the ulnar half of the hand was totally analgesic, the loss of sensation to prick
and to the extremes of temperature extending over the ulnar half of the ring finger. The area
over which light touch was lost almost exa^jtly coincided with that of loss of sensation to prick
{vide fig. 40, c).

On ]March 7, the condition of the hand was that described above, except that the loss of sensa-
tion to prick and to the extremes of heat and cold did not extend quite so far towards the radial
side ; thus there was now a zone of I'S cm. in breadth which was sensitive to prick, but insensiti\'e
to light touch. By September 3 this had increased considerably. Over this intermediate zone
not only was light touch lost, but water at 20° C. and at 40° C. were not appreciated ; sensation
to prick, to water at 45° C, and to ice was present over this part of the hand. The patient was
then compelled to return to his home in Jamaica, and we were unable to examine him furthei'.

Case 84. — Bullet wound of the forearm, causing hyperalgesia over the distribution of the ulnar
and internal cidaneous nenes.

In September, 1901, at Blood River Poort, J. D., aged 21, a corporal in Cough's IMounted
Infantry, was shot through the left forearm. His arm dropped at once, and the ulnar half
of the hand became numb.

The bullet entered 4 cm. below the head of the radius on the outer surface of the forearm,
and passed out on the anterior surface, 8 cm. below the internal condyle of the humerus.

INJURY TO THE PERIPHERAL NERVES

213

We first saw him at Netley on March 2, 1902. He complained of a constant tingling pain,
particularly troublesome in cold weather, over the whole ulnar side of the forearm and hand.
He had also noticed that the affected portion of his palm sweated more than a similar part of the
sound hand.

Running downwards from the scar on the anterior surface of the forearm was an area of
hyperalgesia extending on to the hand (fig. 41). It could be marked out with ease by dragging

■"'•.■^>

wm^

Fig. 41.
To illustrate Case 84.
A shows the extent of the hyperalgesia.
B the extent of the loss of sensation to light touch, and to the intermediate degrees of heat and cold.

a point from the sound towards the affected side of the forearm and hand, or by picking up
the skin.

On the anterior surface of the forearm, the boundary of the hyperalgesic area ran downwards
towards the wrist, a little to the radial side of a line continued ujswards from the axis of the ring
finger. At the junction of the middle and lower thirds of the forearm, the area extended towards
the radial side, reaching the proximal portion of the thenar eminence; from this point it was
bounded by a line continued to the radial edge of the thumb-nail. The whole of the palmar

214

STUDIES IN NEUROLOGY

surface of tlie hand and fingers was hyperalgesic with the exception of the index and the terminal
two phalanges of the midcUe finger (fig. 41, a).

On the dorsal (extensor) surface, the boundary of this area of hyperalgesia corresponded in
its upper two-thirds to a line continued upwards to the scar from the cleft between the middle
and ring fingers. In the lower third of the forearm it swmig outwards, reaching nearly to the
tendon of the extensor ossis metacarjDi laoUicis at the wrist. Thence it was continued down
towards the knuckle of the middle finger. The whole of the dorsal surface of the hand up to this
line, the dorsal surface of little and ring fingers, together with the ulnar two-thirds of the first
phalanx of the middle finger, were tender.

Cotton wool and the minor degrees of temperature could not be appreciated over the full
area in the hand supjilied by the uhiar nerve (fig. 41, b). Sensation to prick and to the extremes

of heat and cold was everywhere present.

iA A A A There was no marked muscular wasting, and all the muscles

I 1 11 A acted perfectly and reacted to the interrupted current.

Case 28. — Division of the median and ulnar nerves, together with
several tendons. Primary union of tendons. Secondary suture of
the nerves after the tendons had healed. Condition of deep sensibility.

G. B., a carpenter, aged 24, cut his right forearm with glass
on September 24, 1902. The womid was explored the same day
without an anaesthetic ; several divided tendons were sutured, but
the nerve injury was not discovered. Two or three days later he
noticed that he had " lost aU feeling " in the pako of the hand
and fingers.

He was admitted to the London Hospital on April 15, 1903,
and we saw him the following day. He had been at work for five
weeks ; a week after he had begun work a blister had appeared on
the fingers, wliich had burst and discharged, leaving an ulcer.

In order to treat this conchtion he placed the fingers in hot
water, and so jDroduced further blisters. This resulted in the
following condition, which was present when we first saw him.
A superficial ulcer occupied the surface of the last two phalanges
of the index finger ; the nail had chsappeared, leaving a granulating
surface dischargmg pus. The terminal phalanx of the middle
finger was in a similar condition. No blisters had aj^peared on the other fingers, although
the whole hand had been placed in the hot water.

A flap-shaped scar was present on the anterior surface of the forearm, extending downwards
and radialwards from 8 cm. above the head of the ulnar to 3 cm. above the fold of the wrist at
the tendon of the flexor carpi racUalis; here it changed its direction and ran almost vertically
upwards for 3 cm.

The hand was in the position typical of ulnar paralysis, and all its intrinsic muscles were
wasted and j^aralysed; they did not respond to stimulation with the interrupted current.
Sensibihty to light touch and to prick were lost over the areas in fig. 42, A.
On April 17 the conchtion of the nerves was explored. The median was found to have been
completely chAided and its ends separated, the lower being miited to a tendon. The upper end
of the ulnar was bulbous and united to the lower by a thin strand of tissue. Both nerves were
remiited after the ends had been freed and freshened.

This operation resulted in a considerable increase in the area insensitive to prick and to the
more extreme degrees of heat and cold (fig. 42, b).

No improvement in the sensory condition of the hand took place until after August 23. The
area insensitive to light touch and to jorick remained as extensive and well defined as immedi-
ately after suture. He failed to appreciate ice, and water at 50° C. over the area insensitive to

Fig. 42.

To illustrate Case 28.

A shows the loss of sensation
before the operation.

B shows the loss of sensation
produced by the operation of
April 17.

INJURY TO THE PERIPHERAL NERVES 215

prick, and over the area anaesthetic to cotton-wool he could not recognise water at 22° C. and at
40° C. Sensibility to deep touch was jsresent and well localised everywhere except over the
little finger. To the compass test applied over the median half of the palm, he failed entirely
at 3 cm., but when the two points were ajiplied successively, he made no mistakes at 2 cm.
and was rarely wrong at 1-5 cm.

By September 27, he could aj)iireciate a prick and the more extreme degrees of temperature
over the whole of the palm and dorsum of the hand, the fingers still remaining insensitive to
these stimuli. By December 20, all analgesia had disappeared and he could appreciate stimu-
lation witJi cotton wool over the dorsum of the hand, but if this area was shaved, it was found
to be entirely insensitive to this stimulus.

Case 43. — Complete division of the musculo-spiral nerve,

F. L., a boy of 9, fractured the lower end of his right humerus on Jmie 28, 1903. Two days
later an open operation was performed in order to reduce the deformity.

Paralysis of the muscles of the forearm supplied by the musculo-spiral nerve resulted from
this operation. In consequence of this condition he came under the care of one of us at the
Poplar Hospital for Accidents on July 28, 1903.

All the muscles in the forearm sujjplied by the musculo-spiral nerve were wasted and para-
lysed; they did not react to the interrupted current, but responded with a characteristically
sluggish contraction to the constant current to which they reacted more readily with the positive
than with the negative pole.

No loss of sensibility to any form of stimulation could be discovered, either in the forearm
or hand.

On August 3, an exploratory operation showed the nerve to have been completely divided.-
The two ends were adherent to the bone and imited by a thin strand of fibrous tissue. They
were freed, freshened, and again united.

No change in sensation was produced by this operation, and the woimd healed by first
intention.

On February 22, 1904, the extensors of the wrist acted voluntarily, and responded to stimu-
lation with a strong interrupted current. All the affected muscles acted voluntarily on May 2,
but no response could be obtained to stimulation with the weak interrupted currents he would
tolerate at this date, although they reacted briskly to the normal pole of the constant current.
On Jmie 29 they reacted to the interrupted current, and by September 14, 1904, all muscular
wasting had disappeared.

Case 44. — Surgical division of the radial nerve {ramus superficialis nervi radialis) at the wrist,
followed by division of the posterior branch of the external cutaneous at the elbow. Subsequent
division of the branch of the median to the ulnar half of the thumb.

L. L., a dressmaker, aged 33, came under our care in August, 1934.

For five years she had suffered from a " neuralgic " pain, starting in the left thumb and shooting
up the arm to the axilla. If she accidentally knocked the thumb, the pain became so severe
that she " almost fainted."

The ulnar portion of the terminal phalanx of the thumb was tender to pressure with the head
or point of a pin, but all forms of sensation were otherwise normally present. The radial and
musculo-spiral nerves were tender throughout their course.

On August 27, 1904, the radial nerve was exposed just after it had passed under the tendon of
the supinator longus and an inch removed.

As the result of this operation, light touch, and water at 23° C. and 40° C. were not appreciated
over the area in fig. 43, A. The boundary of this loss of sensation on the thenar eminence and
both borders on the dorsum of the thumb were well defined, while that on the dorsum of the
hand merged gradually into parts of normal sensibility. A prick, ice, and water at 50° C. were

216

STUDIES IN NEUROLOGY

appreciated everywhere. The tender area on the dorsum of the thumb was still present, 'although
the tenderness was less pronounced. Consequently, on September 9, 1904, the posterior division
of the external cutaneous nerve was divided at the bend of the elbow. This operation increased
slightly the area insensitive to hght touch on the dorsum of the hand, but left it unaltered on the

To illustrate Case 44.

A shows the area which became insensitive to light touch in consequence of division of the radial
nerve (ramus superficialis nervi radialis) at the WTist.

B shows the areas of loss of sensation produced by subsequent division of the posterior branch of
the external cutaneous nerve at the elbow. The thick line encloses the parts insensitive to prick, the
thin line the parts insensitive to cotton wool.

C shows the additional loss of sensation on the thumb caused by subsequent division of the branch
of the median nerve to the ulnar half of the thumb.

thenar eminence and thumb. A prick and the more extreme degrees of temperature could not
be appreciated over an area almost as extensive as that within which light touch was lost, but
a small area of dissociated sensation was present on the dorsum of the hand sensitive to cotton
wool, but insensitive to prick and to aU degrees of temperature {vide fig. 43, b). Deep touch was

INJURY TO THE PERIPHERAL NERVES

217

appreciated over the whole of the affected area. No loss of sensation resulted in the forearm
from this operation.

As a little tenderness still remained at the extreme ulnar border of the tip of the thumb,
the branch of the median nerve supplying the irmer side of the thumb was divided on October 5.
1904. This rendered the ulnar border of its terminal phalanx entirely insensitive to all forms of
cutaneous stimulation (fig. 43, c).

Case 47. — Accidental division of the radial {ramus superficialis nervi radialis) and external
cutaneous nerves in the forearm. The case illustrates the characteristics of deep sensihility.

G. S., a cabinet-maker, aged 23, cut his left forearm with a broken window on July 23, 1903.
The wound was sutured immediately, but suppurated severely, and he was admitted to the
London Hospital with secondary haemorrhage ten days later.

He first came under our observation on October 25, 1903.

From Case 47, to show the area of loss of sensation produced by the accidental division of the
radial (ramus superficialis nervi radialis) and external cutaneous nerves. The jagged scar is
represented running across the flexor surface of the forearm. The area insensitive to light touch is
enclosed by a thin line, that insensitive to all cutaneous stimulation by a heavy black line.

On the radial border of the lower third of the forearm was a multiradiate scar, its centre
situated 9 cm. above the wrist, depressed and adherent to the underlying structures.

All the movements of the hand and fingers were perfect, and there were no obvious changes
in the appearance of the skin.

He was unable to appreciate a prick, light touch, and all degrees of temperature over an area
on the forearm and hand shown in fig. 44. The boundary of the loss of each of these forms of
sensibility was identical, except over a triangular area situated just above the wrist. Over tliis
portion of the dorsum of the hand, measuring 5 cm. in length and 4 cm. in breadth at its widest
part, cotton wool was definitely appreciated, but sensibility to all degrees of temperature was
abolished.

Deep sensibility was present over the whole of the affected area, and he localised well the
point of application of the stimulus. He readily appreciated stimulation with cotton wool
rolled up into a pledget and applied vertically, or dabbed on to the hand. But he entirely failed
to distinguish between the point of a pin and pressure with a steel rod 2 cm. in diameter. If
the skin was raised from the underlying structures, he lost all power of appreciating pressure.

Over the affected area on the dorsum of the hand, he was unable to discriminate two points
at 5 cm., applied simultaneously in a longitudinal direction. But when the points were applied

218 STUDIES IN NEUROLOGY

successively, he frequently recognised the double natme of the stimulus, although the points
were only 2 cm. apart. Over a similar portion of the sound hand he made no mistakes at 3 cm,,
and only two at 2 cm.

We had the oiDportunity of examining this patient on many subsequent occasions. The
area of loss of aU forms of cutaneous sensibihty remained mialtered, and the triangular area of
dissociated sensibility persisted; but the amount of sensation evoked by cotton wool varied
considerably, being considerably less in the winter.

When we last saw him on September 11, 1905, this area was as evident as when we first
tested him, and the character of its sensibihty remained unchanged. After shaving, it became
entirely insensitive to cotton wool, and the area of loss to this form of stimulation then corre-
sponded exactly to that of the loss of prick.

Case 85. — Division of the median, radial and fart of the external cutaneous nerves. Trophic
changes in the shin of the insensitive fingers. Dissociated sensibility on the radial side of the back
of the hand.

T. S., a plumber, aged 30, was admitted to the London Hospital on May 12, 1902.

Six weeks previously (March 29) he' had put his right hand through a glass panel, cutting
the wrist. The wound was sewn up the next day, and " never properly healed." He noticed
that the radial half of the hand was numb immediately after the accident.

A transverse scar ran round the radial portion of the wrist from the base of the third meta-
carpal bone on the back of the hand to the second on its palmar surface. In the centre of this
wound was a small granulating area.

The hand was held adducted to the ulnar side and slightly flexed. The outer group of thenar
muscles was wasted, and the abductor and opponens poUicis were not acting and did not respond
to stimulation with the interrupted current. The flexor and extensor tendons of the thumb,
the flexors of the index finger, and the radial extensors of the wrist, were seen to be divided on
throwing the muscles into action.

The skin over the whole palm was desquamating ; the middle and index fingers were covered
with rough scales, but the little and ring fingers had already completely desquamated.

The boundaries of the area of loss of sensation corresponded almost exactly on the palm for
all forms of cutaneous stimulation, and the borders were well defined {vide fig. 45). On the
dorsum, over the distal portion of the first interosseous space, light touch, though diminished,
was appreciated over a small triangular area where he was entirely insensitive to prick and all
degrees of temperature.

The boimdary of the loss to light touch was here ill-defined, and the area of loss merged on
the ulnar side into parts of normal sensibihty.

On June 3, the median and radial nerves were exposed. They were fomid to have been
divided, and were reunited.

Xo change in the sensory condition of the hand resulted from this operation. It was not
until November 16, 1902 (166 days after suture), that the analgesia had retreated from the i^alni.
By September 6, 1903, he could appreciate a prick and the more extreme degrees of temperature
everywhere over the affected hand except the terminal phalanges of the index and middle
fingers. The area insensitive to cotton wool remained as extensive and well defined as before
suture.

Up to this date, bums and injuries arising during his work as a plumber had resulted in the
formation of ulcers, but with the return of sensibihty to prick all the ulcers had healed and none
appeared subsequently.

By December 20, 1903 (565 days), the area on the palm and dorsum of the hand anaesthetic
to light touch had diminished in extent, and on January 31, 1904, occupied the last two
phalanges of the fingers and terminal phalanx of the thumb only ; water at 24° C. and at 40° C.
were appreciated except over these parts. To the compass test at 2 cm. he made only two
mistakes, but 1-5 cm. was obviously below the threshold.

INJURY TO THE PERIPHERAL NERVES

219

On February 24, 1904 (G34 days), the opponens and abductor reacted to the interrupted
current, but no vohmtary movement was observed until August 28. At this time he was still
insensitive to cotton wool and the intermediate degrees of temperature over the terminal
phalanges of the index and middle fingers.

Fig. 45.

To illustrate Case 85.

A represents the area insensitive to light touch; the dotted line enclosed an area of diminished
sensibility.

B shows the parts insensitive to prick and to heat and cold.

C shows the parts insensitive to prick in black and those insensitive to light touch enclosed by
a line.

Case 86. — Bullet wound of the ulnar and musculo-spiral nerves. Hyperalgesia over the peri-
pheral distribution of both nerves. Loss of sensation to light touch and to the intermediate degrees
of heat and cold over the full ulnar area.

R. M., a corporal in the Imperial Yeomanry, serving in South Africa, was shot through the
left shoulder at iifty yards, on November 25, 1901.

He immediately felt as if he had received " a sharp blow on the shoulder," and found that
his arm was numb and useless. He fainted, and falling from his horse lay on the veldt for about
two hours. When he regained consciousness, he had so far lost all sense of the position of the
Umb that, as he told us, he " felt for it here and it was there."

Seven days after the injury, the shoulder began to swell and " was swollen to several times its
usual size for four or five days." Ten days after he had been woimded, pain began in the shoulder,
and " gradually worked down the arm, leaving the shoulder free, settling in the hand." The
wound was completely healed in three weeks.

He came under our observation at the Royal Victoria Hospital, Netley, on March 24, 1902,
and again in August of the same year. No change took place in his condition during this
time.

The wound of entry was situated at the junction of the arm with the anterior axillary fold,
7-5 cm. below the coracoid process. The wound of exit lay over the inferior border of the scapula,
11-5 cm. below its spine. All the muscles of the shoulder and arm were wasted, and the biceps
being less affected than the others stood out prominently. All except the triceps were acting
volmitarily. The muscles of the forearm were wasted and the wrist was dropped; all power
of extension of the wrist and fingers was lost and the supinator longus was not acting. All the
flexor muscles acted feebly. The whole hand appeared wasted, and the muscles supplied by the
ulnar nerve were paralysed.

220

STUDIES IN NEUROLOGY

The biceps, extensors of the wi'ist and fingers, supmator longus, interossei and adductors
of the thumb did not react to the interrupted current.

The skin of the affected palm was smooth, pink and mottled. The little finger and ulnar
border of the hand were blue and wrinkled. All the fingers tapered and the nails were kept long
on account of the pain caused by cutting them. They were smooth, and showed excessive
curving, both transversely and longitudinally.

He complained of pain in the hand " as if it were going to burst," and said : " I have often
looked at it, fancying it must be bleeding." The pain was continuous, and he could only obtain
relief by rubbing it with oHve oil, which eased him for about an hour.

Fig. 46.
To illustrate Case 86.
A shows the extent of the hyperalgesia.
B shows the area insensitive to light touch.
C shows the area insensitive to prick and to all degrees of heat and cold.

Extreme hyperalgesia existed over the area shown in fig. 46a. Sensibihty to cotton wool
was absent over the full ulnar area, which merged on the dorsum, by means of a band of chmin-
ished sensibihty into an area on the radial side within which he usually failed to recognise a touch
with cotton wool. Water at 22° C. and at 38° C. were not appreciated over that portion of the
hand where light touch was affected. He was unable to appreciate prick, ice, and water at
55° C. over the area shown in fig. 46, B.

After leavmg Netley on August 26, 1902, he attended a civil hospital imtil February, 1904,
and was treated with massage and galvanism. All pain and tenderness gradually disappeared.

When we saw him again on April 3, 1905, all the muscles of the upper limb were wasted.
Those on the extensor surface of the limb acted voluntarily except the extensor longus poUicis,
and all responded to stimulation with the interrupted current.

None of the intrinsic muscles of the hand acted, or reacted to the interrupted current.

All trace of hyperalgesia had disappeared, and he was able to appreciate a prick and the

INJURY TO THE PERIPHERAL NERVES 221

extreme degrees of temperature over the whole of the affected hand. He was anaesthetic to
cotton wool over the ulnar area on the palm, but ap]3reciated it everywhere on the dorsum, even
after the hand was shaved.

Case 64. — Bullet wound of the arm injuring the musculo- spiral, median and internal cutaneous
nerves. True hyperalgesia. Two forms of cutaneous trophic change.

James W., aged 23, a corporal in the Imperial Yeomanry (Royal Victoria Hospital, Netley).
On August 1, 1901, he was shot through the left arm with a Martini bullet. He fainted and
fell from his horse, but suffered no jiain. The Boers came up, took what they wanted from liim,
and left him lying for two days and one night on the veldt. He was then taken to hospital, but
the "wound became very foul," and did not heal for more than five weeks.

At first the arm was entirely painless ; but about a month after the injury the hand began
to be painful. The pain steadily increased until it became constant. It did not vary to any
considerable extent except in cold weather. In the winter it was scarcely troublesome so long
as the hand was exposed to cold, and cold water always removed the pain for a time.

We first saw him on March 3, 1902. He was then a well-built, healthy looking man, with a
somewhat anxious expression. He carried his arm in a sling with the hand exposed, and was
evidently terrified lest it should be touched or jarred.

The wound of entry was situated 1| in. (4 cm.) above the external condyle of the humerus.
It was triradiate in shape, measuring IJ in. (3 cm.) by J in. (1-2 cm.). Two and three-quarter
inches (7 cm.) above the internal condyle was the wound of exit, oval in shape, 1 in. (2-5 cm.)
by I in. (2 cm.) in size. Both wounds showed a tendency to keloid formation.

The whole of the left hand was smooth and of a bluish-pink colour, the two terminal phalanges
of the index and middle fingers were cold and blue. The radial half of the palm and the index
and middle fingers did not sweat, whereas the whole of the remainder of the palm was sweating
profusely.

The muscles on the extensor surface of the forearm and the outer group of the thenar muscles
were much wasted. Ko extension was possible at the wrist, but, with the fingers extended, the
hand could be raised to the horizontal. The supinator longus was acting well. All movement
was absent in the abductor and opponens pollicis. All the muscles supplied by the ulnar nerve
reacted perfectly to the interrupted current, but no reaction was obtained from the opponens
and abductor poUicis. Neither of the extensors of the wrist nor those of the fingers reacted to
the interrupted current, but all the remaining muscles of the forearm responded. The exten-
sors of the fingers acted feebly, but failed to respond to farachc stimulation. The muscles supplied
by the median nerve neither acted voluntarily nor reacted to the interrupted current.

He complained of great tenderness over the ulnar half of the palm of the hand, and over the
greater part of the dorsum. The head of a pin caused considerable pain when the limits of the
area in fig. 47, a, were reached. Sensibility to cotton wool was lost over an area that occupied
the ulnar half of the forearm on the dorsal surface. To the radial side, this anaesthetic strip
was sharply marked off from the remainder of the arm, but the proximal and distal ends, and
the limits of loss to light touch on the front of the forearm, were indefinite, merging gradually
into parts ot norinal sensibility. On the palm of the hand and over the fingers, light touch was
lost within the area shown in fig. 47, b, corresponding to that commonly seen after division of
the median nerve. Sensation to prick was absent from the index and middle fingers over two
and a half phalanges on the palmar aspect, and the two terminal phalanges on the dorsal surface.
Water at 40° C. was not appreciated over the area where light touch was lost on the forearm and
palm of the hand. Ice, and wiiter at 50" C. produced a sensation of cold and of heat, excepting
over those parts of the fingers insensitive to prick. Tested with the compass points over the
normal palm and over the ulnar portion of the affected palm, the record was perfect at 1-5 cm.
Over the ladial half of the palm of the affected hand within the limits insensitive to light touch,
but sensitive to prick, ten stimuli with the two points at 3 cm. were called " one " ; right answers
were given in every case when one point only was used. By this test there was no material

222

STUDIES IN NEUROLOGY

diininution of sensation over the ulnar half of the affected palm, but over the median half^the
points at 3 cm. were evidently below the threshold of sensation.

On March 27, 1902, we saw him again and found that a sore had made its appearance over the
terminal phalanx of the middle finger; it first appeared as a blister without known cause, and
was entirely painless. It had all the appearances of a trophic sore of a kind not infrequently

Fig. 47.
To illustrate Case 64.
A shows the area that was hyperalgesic.

B shows the area insensitive to light touch enclosed in a single Hne. The parts insensitive to prick
and to all degrees of heat and cold are coloured black.

seen over totally analgesic parts. We were told by the medical officer in charge of the case that
in December, 1901. a herpetiform rash had made its appearance over the ulnar half of the palm
of the hand, and part of the little and ring fingers, that is to say, within tbe area of true hyper-
algesia. Thus, this man showed both forms of trojihic lesion of the skin wliich make their
appearance in consequence of injuries to nerves.

INJURY TO THE PERIPHERAL NERVES

223

On our first visit we had noticed that the nails of the thumb, index and middle fingers were
abnormally curved, both in a transverse and longitudinal direction. He stated that these nails
did not grow so quickly as those of the normal hand, and this statement was borne out by measure-
ments made at our second visit. In the twenty-four days which had elapsed, the growth of the
nails of the two sides was as follows : —

Sound Hand.

Affected Hand

Thumb . .

5 mm.

• •

.3 mm.

Index

0 mm.

. .

1-5 mm.

Mddle . .

B-5 mm. . .

. .

4 mm.

Ring

5 mm.

• ■

5 mm.

Little

4 mm.

1 ^

4 mm.

Thus, although the nails of the ring and little fingers showed an equal amount of growth on
the afi'ected hand, those of the index and middle fell far behind.

We were able to confirm our previous observations on the limits of the hyperalgesia, and
loss to light touch. The extent of the loss to prick was somewhat less than on our first visit.

Fig. 48.

To illustrate the loss of sensation produced in Case 57 by an injury to the great and small sciatic
nerves. Total loss of cutaneous sensibility is represented in black. Loss of sensation to light touch
is enclosed by a line.

Case 57. — Bullet wound of the great and small sciatic nerves.

J. W. B., a private in the 1st Manchester Regiment, was womided at Witklip on October 4,
1901. He was ambushed when on water picket and shot from a distance of about twenty yards.
He at once felt great pain down the back of the leg. The woimd was dressed half an hour later,
and he was taken to Leidenberg Hospital the same daj'.

He came under our observation at Netley in August, 1902. The wound of entrance, situated

224 STUDIES IN NEUROLOGY

2-5 cm. to the right of the spine of the third sacral vertebra, had not yet healed ; 4 cm. anterior
to the upper border of the great trochanter was a small surgical scar through which the bullet
had been extracted.

All the muscles of the lower limb supplied by the sciatic nerve were wasted, and, with the
exception of the hamstring muscles, were paralysed. None of the muscles supplied by the sciatic
nerve contracted to the interrupted current, and to the constant current all reacted sluggishly.
These muscles responded more easily to the positive than to the negative pole, but no reaction
could be obtained from the hamstring muscles, even with a current sufficiently strong to cause
contraction in the muscles on the anterior surface of the limb.

Extending downwards from the fold of the buttock for about 40 cm. was a strip, within which
he was unable to appreciate prick and the more extreme degrees of temperature. Surrounding
this in every direction, and extending on to the buttock, was an area anaesthetic to cotton
wool (fig. 88).

Over the greater part of the foot and outer portion of the lower third of the leg, light touch,
prick, and all degrees of temperature were unappreciated; the borders of loss of sensation to
each of these stimuli were almost exactly co-terminous.

This area was continued upwards into parts insensitive to cotton wool, and to intermediate
temperatures, but sensitive to prick, and to the more extreme degrees of heat and cold. Above
the loss of sensation merged gradually into parts of normal sensibiUty.

A HUMAN EXPERIMENT IN NERVE DIVISION

By W. H. R. rivers, M.D., F.R.S.,

Fellow of St. John's College, Cambridge ;

AND

HENRY HEAD, M.D., F.R.S.

CHAPTER I

HISTORY OF THE CASE

It had long been recognised that the consequences of injury to a peripheral
nerve could not be adequately explained on any accepted theory of its structure
and function. In 1901, Dr. Head and Mr. Sherren therefore determined to
make a systematic examination of the patients attending the London Hospital
for some nerve injury. The hospital patient is frequently an admirable subject
for sensory experiments; at his best he answers "Yes" and "No" with
certainty, and is commendably steady under the fatigue of control experiments.
Moreover, the number of patients, who come to the London HosiJital for such
injuries, is so large that it is possible to eliminate entirely those who are found
to be untrustworthy in consequence of misuse of alcohol or other causes.

Most of the main facts of nerve distribution and recovery of sensation can
be elicited from a study of hospital patients by means of simple tests requiring
no undue expenditure of time. But such patients can tell little or nothing
of the nature of their sensations, and the time they are able, or willing, to give
is insufficient for elaborate psycho -physical testing.

It soon became obvious that many observed facts would remain inexpHcable
without experimentation carried out more carefully and for a longer period
than was possible wdth a patient, however willing, whose ultimate object in
submitting himself to observation is the cure of his disease. For instance,
an examination of the part played by heat- and cold-spots in the return of
sensation was impossible under clinical conditions.

It is also unwise to demand any but the simplest introspection from

patients, to whatever class they may belong. This side of the investigation

was, therefore, almost entu'ely closed to IVIr. Sherren and Dr. Head. From

the early days of their research, Dr. Rivers had acted as their guide and

counsellor. His interest lay rather in the psycho -physical aspect of the work.
VOL. I, 225 Q

226 STUDIES IN NEUROLOGY

and he was impressed with the insecurity of this side of the investigation.
Introspection could be made fruitful by the personal experiences of a trained
observer only.

Lastly, we were anxious to investigate the functions of deep sensibility.
Sherrington [110] had shown that muscular nerves contained a large number
of afferent fibres. From the beginning of their research, Head and Sherren
had tried to determine the sensibility remaining after complete division of
all cutaneous nerves without injury to the muscular branches. But accidental
injuries of this kind are excessively rare, and they were compelled to attack
the problem by indirect and less satisfactory methods. As soon, therefore,
as it was determined to make an experimental division of peripheral nerves,
means were taken to ensure that the nature of these deep afferent fibres should
come clearly to experimental investigation.

At the time of the experiment, H. was nearly 42 years of age and in
perfect health. Since boyhood he had suffered from no illnesses, excepting
as the consequence of wounds in the post-mortem room. None of these had
attacked his left arm or hand, which were entirely free from scars or other
deformities.

For two years before these experiments began he had given up smoking
entiraly. No alcohol was ever taken on the days during which he was under
examination, and for some years he had abstained from alcohol except on
holidays.

On April 25, 1903, the following operation was performed by Mr. Dean,
assisted by IVIr. Sherren.

An incision 6| in. (16-5 cm.) long was made in the outer bicipital fossa
extending along the axial line of the left upper extremity ; this wound was
almost exactly bisected by the fold of the elbow. After turning back the
skin, the supinator longus was hooked outwards, and the radial nerve (ramus
superficialis nervi radialis) was divided at the point where it arises from the
musculo -spiral (n. radialis). A small portion was excised, and the ends united
with two fine silk sutures. The external cutaneous nerve (n. cutaneus anti-
brachii laterahs) was also divided where it perforates the fascia, above the
point where its two branches are given off to supply the anterior and posterior
aspects of the pre-axial half of .the forearm. The nerve was sutured with fine
silk, and the wound was closed with silk sutures, without drainage. The
limb was put up on a spUnt with the forearm flexed at the elbow, and the whole
hand was left free for testing. The wound healed by first intention.

The following morning (April 26, 1903), the radial half of the back of the
hand and dorsal surface of the thumb were found to be insensitive to stimula-
tion with cotton wool, to pricking with a pin, and to all degrees of heat and cold .
Around the base of the index and middle fingers was a small area insensitive
to stimulation with cotton wool and von Frey's hairs, where a response was

1 To Mr. Dean our best thanks are due, not only for the exactitude with which he carried out
our wishes, but also for his kindness in receiving Dr. Head into his house for the operation.

A HUMAN EXPERIMENT IN NERVE DIVISION 227

obtained to the prick of a pin. No sensation was evoked by any manipulation
of the hairs within the affected parts on the back of the hand.

The area insensitive to cotton wool extended slightly further towards the
ulnar aspect of the back of the hand than that of the cutaneous analgesia.
Between the two lay a narrow zone, where a painful cutaneous stimulus
produced a more unpleasant sensation than over the normal skin.

The most strildng fact, however, was the maintenance of deep sensibility
over the whole of the affected parts on the back of the hand. Pressure with
the finger, with a pencil, or any blunt object was immediately appreciated.
All those stimuli commonly used by the clinician to test the presence of

Fju. 49.

To show the extent of the loss of sensation produced by the operation.

The anaesthesia to cotton wool and to von Frey's hairs is bounded by the black line. The analgesia
to prick and other cutaneous painful stimuli lay within the red crosses.

The darkness of the affected area is due to its deep red colour compared with the rest of the hand.

" touch " were appreciated and well localised. Mr. Dean, who was not familiar
with our previous observations, said he should have thought that sensation
of touch was intact, had he not known the nerves had been divided.

On May 4, nine days after the operation, the hand was exposed to a
long series of experiments. The most striking features of this examination
were : —

(a) That very moderate pressure on the abnormal area of the sldn was
appreciated and could be well localised, whilst touches with cotton wool, or
deformations of the skin, produced by drawing the hair outwards, caused
absolutely no sensation.

(6) In spite of the existence of this sensibility, two compass points could

228 STUDIES IN NEUROLOGY

In fact, the condition might easily have been mistaken for one of analgesia
and thermo-ansesthesia with intact sensibihty to touch.

(d) Between the extent of the analgesic area and that insensitive to cotton
wool, lay a border where the prick of a pin was abnormally painful.

(e) None of the cold-spots marked out before the operation reacted to the
usual stimuh.

By May 4 the skin on the back of the hand had assumed a peculiar con-
dition, which was described on the 7th b}^ Dr. J. H. Sequeka in the following
words : —

" The whole of the affected area is of a shghtly deeper red than the rest of
the skin of the hand. It is diy, and covered Avith minute hair-hke scales.

To show the extent of the loss of sensation twenty-one days after the operation (May 16, 1903),
The black line encloses the loss to cutaneous tactile stimuli; the red line encloses the cutaneous
analgesia. Wherever these lines are broken the border was an indefinite one.

On palpation, the skin appears to be thickened and looks as if it were sHghtly
oedematous ; but it does not pit on pressure. A strildng feature is the absence
of the normal elasticity, which is in remarkable contrast with the rest of
the skin. The affected parts do not sweat, while the rest of the hand is
permanently slightly moist."

From the time of the operation until the removal of the splint (May 23),
the borders of the loss of sensation on the forearm underwent no material
change. But H.'s skin had always been peculiarly susceptible to the action
of chemical antiseptics, and the necessary cleansing at the time of the operation
led to desquamation to within about 3 in. to 4 in. of the wrist. Fortunately,
the hand had entirely escaped their action.

On the extensor aspect of the forearm, the loss of all forms of cutaneous
sensation was bounded for the greater part by a definite Hue. Towards the

A HUMAN EXPERIMENT IN NERVE DIVISION 229

radial aspect, the loss of sensation merged more gradually into parts of normal
sensibility. The borders formed a sinuous line, seen on figs. 51 and 52. Over
the greater part of the forearm, the loss of sensation to prick was less extensive

Fig. 51.
Lateral view on the same date (May 16, 1903).

than that to cotton wool ; but nearer to the wrist, the reverse condition seemed
to exist.

The extent of the cutaneous analgesia on the hand was shghtly less than

Fig. 52.
Flexor aspect of the forearm on the same date (May 16, 1903).

that of the loss of sensation to cotton wool and von Frey's hairs, and to these
stimuli all the boundaries were sharply defined, except at the base of the index
and middle fingers.

The sphnt was removed on May 23, and it was then possible to wash the

230

STUDIES IN NEUROLOGY

arm vigorously and to remove the loose scales of epithelium. We then
discovered that the loss of sensation to prick was everywhere coterminous
with, or sKghtly less extensive than, the loss to cotton wool, except near the
wrist. Here there was a triangular area, shown on fig. 53, where cotton wool
and No. 5 of von Frey's hairs ^ were undoubtedly appreciated, although the
skin was insensitive to prick.

On the back of the hand, sensibihty remained exactly in the condition
described immediately after the operation. Over the whole area of cutaneous
anaesthesia, pressure touches were appreciated and well localised. Pain could
be produced as easily by pressure with the algometer over the back of the
affected as over similar parts of the normal hand. Electrical stimuh pro-

To show the loss of sensation on May 26, 1903 (thirty-one days after the operation). On the
lateral aspect of the forearm near the wTist is showTi the triangular area insensitive to prick and other
cutaneous painful stimuli but sensitive to stimulation with cotton wool.

duced no sensation except when the muscles contracted ; then the smallest
visible movement was appreciated. To recognis3 pure movement, produced
electrically, without a concomitant cutaneous sensation is a remarkable
experience.

Though sensitive to the tactile and painful elements of pressure, and to
the passive movement of muscles, the back of the hand was anaesthetic to all
thermal stimuh ; the tissues could be frozen firmly wdth ethyl chloride without
the production of even the slightest sensation.

The first noticeable change in the extent of the loss of sensation was dis-
covered on June 7, forty-three days after the operation. The borders of the
area insensitive to cotton wool remained unaltered, but the cutaneous

^ Throughout this part of the work Von Frey's hairs were used almost exclusively as light
tactile stimuli. Usually, therefore, they are spoken of as " No. 5," etc., their tension value,
rather than by the pressure they exert per unit a:ea [vide p. 15).

A HUMAN EXPERIMENT IN NERVE DIVISION 231

analgesia was distinctly less extensive, and no longer coincided with it on the
flexor aspect of the forearm ; the extent of the cutaneous analgesia had
diminished for 3 in. (8 cm.), or more, peripheral to the scar. This was
particularly noticeable, because the borders of the loss of sensation to cotton
wool had remained unchanged.

Moreover, the boundaries of the cutaneous analgesia were no longer
definite, but were made up of islets, or points, of sensation. Passing from
the area of complete loss to parts normally sensitive to a prick, the pin struck
spots, where it produced a slowly developed, dull but painful sensation. If,
however, this particular spot was not struck, it might be that sensibility was

Fig. 54.
To show the loss of sensation on June 14, 1903 (fifty days after the operation).

not encountered until another spot was reached, some millimetres nearer the
unaffected parts of the limb.

On June 14, fifty days after the operation, the gradual shrinking in extent
of the cutaneous analgesia on the arm was found to have continued (figs. 54, 55
and 56), although the borders of the loss of sensation to cotton wool remained
entirely unaltered. The loss of sensation to cold corresponded in extent
with that of the loss to prick ; but, wherever the part was feebl}^ sensitive to
the latter stimulus, sensibility to cold seemed to be absent. To all degrees
of heat the borders of the loss of sensation had remained unchanged, and the
extent of the anaesthesia, even to temperatures between 50° C. and 60^ C.
uniformly exceeded that of the loss to prick.

232

STUDIES IN NEUROLOGY

By June 20 (fifty-six days after the operation), recovery of sensation had
progressed still further. Not only had the extent of the absolute cutaneous
analgesia shrunk considerably on the forearm, but the terminal phalanx and

Fig. 55.
Lateral view of the forearm and hand on June 14, 1903.

Fig. 56.
Flexor aspect of the forearm on June 14, 1903.

a portion of the basal phalanx of the thumb had become sensitive to prick.
The extent of the area between the borders of the loss of sensation to cotton
wool and to prick in the first interosseous space had increased to nearly 2 cm.

A HUMAN EXPERIMENT IN NERVE DIVISION 233

(fig. 57). At this date, the marldngs of the previous week were still visible
on the arm, and the boundary of the analgesia lay in many places 0-5 cm.
within those determined six days before. And yet, m spite of this rapid
improvement in sensibility to prick, the borders of the anaesthesia to cotton
wool and von Frey's tactile hairs remained absolutely unchanged.

On the flexor surface of the forearm, there was nothing to show that cold
could be appreciated within the border of cutaneous tactile anaesthesia. In
the first interosseous space, cold was certainly appreciated well inside the

Fig. 57.

To show the loss of sensation on June 20 (fifty-six days after the operation). The cutaneous
analgesia on the forearm could not now be defined accurately, but merged everywhere into parts
sensitive to prick. It is therefore surrounded by a dotted broken border.

limits of the loss of sensation to cotton wool ; the border of the loss to cold lay
about midway between that for cotton wool and that for prick.

By July 20 (eighty-six days after the operation), there was no part of the
forearm where a prick could not be occasionally appreciated, although in many
places this form of sensation was extremely defective. Moreover, consider-
able changes had occurred in the condition of the hand ; the whole of the thumb
and the skin over the radial half of the first metacarpal had become sensitive to
prick. The analgesic area on the back of the hand was diminishing from its
radial aspect.

In spite of these changes, the borders for the loss of sensation to cotton
wool remained exactly as before.

234

STUDIES IX NEUROLOGY

On the forearm, ice was not appreciated with certainty, until the original
border of cutaneous analgesia was passed. Water above 50° C. produced pain
Mdthin the parts now sensitive to a prick, but it was impossible to say whether
the pain was accompanied b}^ any thermal quality.

The terminal phalanx of the thumb was certainly sensitive to cold below
17° C. and more doubtfully to heat above 45° C. Within the area of dissociated
sensibility in the first interosseous space, and over the ball of the thumb, it
was difficult to be sure that any sensation of temperature was jDroduced by
ice-cold and hot water ; but the border of the thermo-ansesthesia probably lay
sUghtly within that for sensibihty to cotton wool.

At this time, some of the hairs on the forearm within the affected area
became sensitive to pulling. The sensation produced was slowly developed

Fig. 58.

To show the condition on July 20, 1903 (eighty-six days after the operation). No part of the forearm
was entirelj^ insensitive to cutaneous painful stimuli.

and excessively unpleasant. It died away, and recurred again, without further
stimulation. These hairs lay entirely within the upper anaesthetic patch.

On August 10 (107 days after the operation), the sensibility to prick had
further improved, although the extent of the anaesthesia to cotton wool
remained entirely unaltered. On August 15, for the first time since the
recovery of sensation began, it could be said that parts which were at first
insensitive to heat and cold now responded definitely and constantly to these
stimuU. Over the upper patch on the forearm, ice uniformly produced a
sensation of cold. Temjieratures above 50° C. caused a stinging sensation,
usually called " burning," but it is doubtful to what extent this contained
more than the painful element of heat.

The terminal phalanx of the thumb undoubtedly responded to tempera-
tures above 45° C, and the sensation produced by temperatures above 50° C.
contained a thermal element in addition to the stinging pain. Even the

A HUMAN EXPERIMENT IN NERVE DIVISION 235

proximal phalanx of tlie thumb had become sensitive to ice, although still
anaesthetic to heat.

On August 15 and 16, these observations on the upper patch of the fore-
arm and the terminal phalanx were confirmed, and within these areas we were
able to mark out definite cold-spots for the first time since the operation.
Four of these lay in the upper patch, and four over the terminal phalanx of
the thumb.

By September 9 (137 days after the operation), the whole forearm had
become sensitive to cold, and cold-spots were discovered not only in the upper
patch on the forearm and in the terminal phalanx of the thumb, but also over
the more distal portions of the affected area. The forearm still remained

Fig. 59.

To show the condition on September 24, 1903 (152 clays after the operation). Over the small
irregular area on the back of the hand sensibihty to cutaneous iDainful stimuH was greatly diminished
and in places was absent.

The area occupied by the trophic sore is marked with a circle.

insensitive to heat, except in as far as temperatures above 50^ C. produced a
peculiar form of painful sensation, usually called " burning."

In spite of the complete absence of any change in the behaviour of the
affected parts to cotton wool, sensibility to prick continued to return steadily,
and by September 24 (152 days after the operation) a small area only on the
back of the hand remained insensitive to this stimulus (fig. 59).

Since July 10, when the back of the hand had been too energetically frozen
with ethyl chloride, an indolent sore had existed in the centre of the affected
area. It tended to heal if protected, but would break down again under the
influence of the slight accidents of ordinary life. On September 23, attention
was attracted to its condition by the presence of tinghng, which had never
been noticed before. This led to the discovery that painful sensation, of a
dull and ill-defined character, was present in the neighbourhood of the sore.

236 STUDIES IN NEUROLOGY

From this time it healed with great rapidity, although no special care was
taken to protect it. Once healed, it never broke dowTi again after the return
of sensibihty to painful cutaneous stimuli.

About this time, part of the first interosseous space, which had become
sensitive to prick, began to respond to ice ; this return of sensation was found
to be associated with a few definite cold-spots. But the affected area still
remained insensitive to heat.

On October 3 (161 days after the operation), we noticed, for the first time,
that cotton wool produced some sensation over the upper patch on the fore-
arm. This change advanced with considerable rapidity, and on October 6
sensibihty to cotton wool was present in a very defective form over both upper
and lower forearm patches. The upper of these areas seemed to become
sensitive by gradual encroachment from the edges, whilst the loAver appeared
to recover at the centre as quickly as at the periphery. Later we found that
this response was due entirely to the retui-n to the hairs of a pecuHar form of
sensibihty {vide p. 272).

About this time (October 8), the upper patch on the forearm became
undoubtedly sensitive to temperatures of and above 45° C. An excellent
heat-spot was found in the centre of the patch, to which this return was
certainly due.

By October 15 (173 days after the operation), no part of the hand was
entirely insensitive to prick, although sensation was defective over the parts
dotted on fig. 60.

The greater part of the back of the hand now reacted to the more extreme
degrees of cold, and the cold-spots had multiplied greatly. By November 1
(190 days after the operation), cold could be appreciated everywhere over the
back of the hand, and tAventy-four cold-spots were discovered within the
affected area. At the same time, one heat-spot was found near the base of
the first phalanx of the thumb. This was the only part of the affected area
on the hand sensitive to heat.

From this time, the cold-spots and heat-spots rapidly increased in number
over the back of the hand, the increase proceeding step by step with the
recovery of sensibihty to cold and to heat.

With the gradual return of sensibihty to pain, cold, and heat, Ave noticed
that the sensation tended to be widely diffused, and was not infrequently
locahsed in some part remote from the point of stimulation (September, 1903).
If, for instance, ice was applied to the proximal portion of the forearm, a
sensation of coldness was produced in the thumb. The site of this referred
sensation remained the same, whatever the nature of the stimulus, provided
it was one to which the affected area had become sensitive.

By December 3 (222 days after the operation), the pecuhar tinghng sensa-
tion i3roduced by cotton wool could be evoked by stimulating the thumb and
the adjoining interosseous space. This sensibihty rapidly increased in extent,
until there was scarcely any part of the affected area from whicli it could not

A HUMAN EXPERIMENT IN NERVE DIVISION 237

be produced (December 6). The sensation was one which could be expressed
only as a general state of diffuse painless tingling. Moreover, it was found
that parts which gave this reaction to cotton wool were insensitive to No. 5
of von Frey's hairs and to the painless interrupted current, just as in the early
days after the operation. Exactly the same borders could be marked out both
on the forearm and hand by dragging a pin lightly from normal to abnormal
parts ; for as soon as the old border of cutaneous anaesthesia to touch was
passed, the sensation became a widely diffused tingling pain.

Thus it would seem that the sensibility to cotton wool, which began to
return to the forearm 161 days, and to the hand 224 days, after the operation,

Fig. go.

To show the condition of the back of the hand on October 15, 1903 (173 days after the operation).
The healed sore can be seen as a scar in the neighbourhood of the red dots.

was not the equivalent of the normal sensation of light touch over hairless
parts, but was a peculiar form of hair-sensibility. For the areas endowed with
it remained anaesthetic to the painless interrupted current and to No. 5 of von
Frey's hairs ; moreover, the sensation produced was widely diffused and was
referred to remote parts, exactly like the sensation of prick and ice-cold over
the same regions. This hypothesis was found at a later date to be correct.
For on shaving the areas endowed with this form of sensibility, they became
entirely insensitive to cotton wool.

We could not be certain that the forearm was sensitive to cotton wool
when carefully shaved, until April 24, 1904, exactly a year after the operation.

On June 5, 1904 (407 days after the operation), the affected area on the
forearm responded to temperatures of 37° C. This sensibility to warmth rapidly

238

STUDIES IN NEUROLOGY

increased, and on June 26 was obtained, even with 34° C. Moreover, the sensa-
tion produced was one of warmth localised in the part touched. Except that
it was not quite so acute, it exactly resembled that produced on the normal skin
under similar circumstances. It had none of the diffuse radiation and tendency
to reference into remote parts, so characteristic of the sensation evoked by
stimulating heat-spots.

It was not until November 12, 1904 (567 days after the operation), that
a portion of the back of the hand (fig. 61) began to be undoubtedly sensitive
to warmth (35-5° C.) and to cotton wool after shaving. The diffusion and
radiation so characteristic of the previous stage of recovery were at once

Fig. 61.

November 12, 1904 (567 clays after the operation).

To show the manner in which f-ensibility returned to cutaneous tactile stimuli. The dotted area
corresponds to the parts sensitive after shaving to cotton wool and to von Frey's tactile hairs (No. 5).
These parts were also sensitive to temperatures of about 36° C.

greatly diminished ; so profound was this change that we recognised it before
we could be certain of the increased sensibility to thermal and tactile stimuli.

Up till the end of November, 1904, the improvement continued rapidly.
But with the advent of winter cold the condition of the hand went back ; the
referred sensations reappeared, to become as definite as they had been six
months before, and the hand became less sensitive to warmth, and to cotton
wool after shaving.

In March, 1905, it again began to improve. Part of the affected area on
the back of the hand became sensitive to No. 5 of von Frey's hairs, and
reference greatly diminished. By May 21, a large area on the back of the hand
had become sensitive to cotton wool and to minor degrees of heat ; stimulation
with No. 5 was widely appreciated. A referred sensation could no longer be
produced from any part in this condition.

A HUMAN EXPERIMENT IN NERVE DIVISION 239

Although this improvement continued throughout the summer of 1905, a
small portion of the affected area, lying mainly in the neighbourhood of the
knuckles of the index and middle finger, has remained insensitive to No. 5,

Fig. 62.

To show the extent of the affected area, which is still (1908) supplied with deep and protopathic
sensibility only. Its radial border merges gradually into parts that have recovered more completely.

or to cotton wool after shaving (fig. 62). Even at the present time, this part
still is in a purely protopathic condition, sensitive to prick, to ice and to water
above 37° C. All these stimuli cause sensations, referred to the dorsal aspect
of the thumb and diffused widely around the point to which they are applied.

240 STUDIES IN NEUROLOGY

It seems as if one of the branches of the external cutaneous had not reunited,
leaving this part of the affected area to be supplied by its fellow and by the
radial.

The history of the case may be summed up in the form of the folloAving
diary : —

On April 23, 1903, the radial (ramus superficialis nervi radialis) and both
branches of the external cutaneous (n. cutaneus antibrachii lateralis) were
divided in the neighbourhood of the elbow. Both nerves were reunited with
silk sutures and the wound healed by first intention.

This operation did not interfere with sensibility to the tactile and painful
aspects of pressure. But the whole of the affected area became insensitive to
prick, to heat, and to cold ; two points of the compasses, applied simultaneously,
could not be appreciated, but localisation was preserved.

Forty-three days after the operation (June 7), the extent of the cutaneous
analgesia had begun to diminish.

Fifty-six days after the operation (June 20), the analgesia on the forearm
had greatly diminished, and the thumb had become sensitive to prick.

Eighty-six days after the operation (July 20), the whole forearm responded
to prick, and the back of the hand was becoming rapidly sensitive to this form
of stimulation. Cold was not appreciated except over the terminal phalanx
of the thumb, and 50° C. gave rise to no sensation of heat.

One hundred and tivelve days after the operation (August 15), the proximal
part of the affected area over the forearm had become sensitive to cold.

One hundred and thirty-seven days after the operation (September 9), the
whole forearm had become sensitive to cold.

One hundred and fifty-two days after the operation (September 24), the
whole of the affected area, excepting a small spot on the back of the hand,
had become sensitive to prick ; the trophic sore healed.

One hundred and sixty-one days after the operation (October 3), cotton
wool began to produce a diffuse tingling sensation over the forearm when the
hairs were stimulated, but the whole of the affected area still remained
insensitive to von Frey's tactile hairs. About the same time, the proximal
patch on the forearm began to be sensitive to heat, and a defuiite heat-spot
was discovered in this position.

One hundred and seveyity-three days after the operation (October 15), the
whole of the back of the hand had become sensitive to prick and, in a less
degree, to cold.

One hundred and ninety days after the operation (November 1), the first
heat-spot was discovered on the back of the hand.

Two hundred and twenty-five days after the operation (December 6), the
hairs on the back of the hand responded with a diffused tingling to cotton
wool, but the whole affected area of the forearm and hand still remained
insensitive to von Frey's tactile hairs. This sensibility to cotton wool
disappeared at once, if the arm was carefully shaved.

A HUMAN EXPERIMENT IN NERVE DIVISION 241

Three hundred and sixty- five days after the operation (April 24, 1904), the
proximal patch on the forearm began to be sensitive to cotton wool after
sha\Tng.

Between four hundred and seven and four hundred and twenty-eight days
after the operation (June 5 to Jmie 26, 1904), the affected area on the forearm
became sensitive to temperatures between 37° C. and 34° C. The tendency
to diffusion and reference greatly diminished.

Five hundred and sixty-seven days after the operation (November 12, 1904),
the greater part of the affected area on the back of the hand had become
sensitive to cutaneous tactile stimuli, and temperatures below 37° C. evoked
sensations of warmth.

VOL. r. R

CHAPTER II

CONDITIONS OF EXAINIINATION

It was recognised by experiments before the operation that the ordinary
distractions of a busy life were fatal to the detachment required by the sensory
tests we wished to apply. We therefore determined that the work should be
carried out in St. John's College, Cambridge. ^ The mner of a set of rooms on
the top floor of the second court, belonging to Dr. Rivers, was devoted to these
observations. Here, absolutely quiet and undisturbed, free from the petty
worries of a busy life, H. gave himself over entirely to exammation.

As a rule, he travelled to Cambridge on Saturday, after spending several
hours in the out-patient department of the London Hospital. But, on Saturday
evening, he was found to be in a condition of so great fatigue that no observa-
tions could be made mitil Sunday morning. If, therefore, it was necessary to
carr}^ out a long-continued series of tests, H. came to Cambridge on Friday
night, returning to London on Monday mornmg. Occasionally longer periods
could be devoted to these observations.

Between April 25, 1903, the date of the operation, and the last sitting
with Dr. Rivers on December 13, 1907, 167 davs were devoted to this
investigation.

The greater part of the work was done in the morning. Then H. went
for a walk or a ride, and in the summer occasionally spent the afternoon on
the river. The time between 5 p.m. and 7 p.m. was commonly spent in control
experiments on normal parts, or in amplifying the results obtained earlier
in the day. Durmg the evening, these were talked over whilst H. marked
out the hand, and determined the position of the cold- and heat-spots in
preparation for further tests next day.

The plan of investigation was debated beforehand, and was frequently
committed to paper the night before the testing began. But R. always varied
this order to such an extent, that H. remained ignorant of the results luitil
the close of the sitting. This was especially the case with the compass-
records ; for instance, during many months, H. purposely refrained from
inquiring mto the nature of R.'s series of observations on the phenomenon
of " double ones."

Throughout the examination, R. recorded exactly the procedure and H.'s

^ Dr. Head wishes to take this opportunity of expressing his gratitude to the President and
Fellow;; of St. John's College, Cambridge, for the generous hospitaUty extended to him durmg
the five years he was their frequent guest.

242

A HUMAN EXPERIMENT IN NERVE DIVISION 243

answer at the time. At the close of a series, whilst still ignorant of the actual
tests applied by R., H. dictated a note commenting on his experiences. Even
then he was not told the nature of R.'s manipulations, unless some new fact
had appeared w-hich demanded immediate consideration.

Under no circumstances was H. allowed to know at the time whether his
answers were right or wrong. For if he was told he had answered wrongly,
he was roused to an intense determination to do better, producing thus a
mental condition which was found to be unfavourable for the appreciation of
sensory stimuli. Knowing his answers had not been correct, he would catch
at every accessory circumstance in his attempt to interpret his sensations.

H. always sat with his eyes closed throughout the examination, as he
found that this produced in him the condition most favourable for sensory
testing. He always answered more correctly to all tests which required no
close introspection when he did not attempt to think of what was going on.
He would sit with closed eyes, his head resting on the right hand and his atten-
tion wandering widely over internal images. He soon learnt to adopt at will
this state of passivity, provided he was undisturbed. But a knock at the door,
or the entry of the servant, would rouse him into a state in which he again
began to interpret his sensations.

H.'s mental processes are based upon visual images to a remarkable degree.
Every thought is in some way bound up with internal vision, and even numbers,
the days of the week and abstract ideas, such as virtue and cowardice, are
associated with images of varying tones of white and black. He cannot
recall musical sounds, except by seemg the notes or attaching the sounds to
words which are clearly visualised. He has no power of reproducing directly
scents or cutaneous sensations. He knows that the scent of violets is pleasing,
and recognises it with ease whenever it is present ; but he is unable to recall
a scent or a tactile impression in the same way that he can project the memory
picture of an object once seen.

In all these points, he corresponds to the common group of strong visualisers
who learn to depend so exclusively on visual images that all other less dominant
faculties of sensory reproduction fall into disuse. Throughout this paper we
shall frequently allude to the part played in H.'s answers by these vivid mental
images.

He was able to reproduce the image of a thing seen with such accuracy
that it could be searched for details, at first unnoticed. But this was not the
case with any other sensory impression. As soon as the stimulus was removed,
he retained so much only as had been noticed at the time ; for he was unable
to reproduce any sensory images, except those of vision. This peculiarity
common to most of those who visualise strongly leads to the following difficulty
in testing sensation. Suppose that H. was retummg correct answers to stimuli
of different kinds applied to the affected area ; the one was said to cause a
sensation of touch, another appeared hot, and a thkd seemed to be cold. If,
after withdrawing the cold object, R. inquired unexpectedly concerning the

244 STUDIES IN NEUROLOGY

nature of the referred sensation, H. was frequently puzzled. Had the question
referred to the qualities of a thing seen, H. would have recalled the visual
image, examined it carefully and answered accordingly. But as he could
not recall any tactile or thermal image of the cold object, he was unable to
answer a question relatmg to some sensory quality to which his attention
had not been directed at the time. A prick or other painful stimulus, however
intense, evoked a sensation that could not be reproduced.

In the same way when tested with the compasses, H. might answer " two "
rightl}^ or wrongly ; but if, after the points were withdrawn, he was asked
miexpectedly whether they seemed close together or far apart, he was unable
to give an opinion. This occurred when the test was applied over both normal
and abnormal parts, provided the compasses were suitably adapted.

Again, some unexpected feature m the sensation might arouse H.'s
attention, but inability to reproduce the sensory image greatly hindered its
mtrospective study. It was often necessary to repeat the stimulus several
times before H. could appreciate each separate aspect of the sensation.

Now, sense-organs, and particularly those of the skin, do not react in an
exactly similar way to every repetition of the stimulus. As this is particu-
larly the case with those of the protopathic system, H.'s mability to recapture
the features of a somatic sensation in the form of a reproduced image con-
siderably hindered his mtrospective analysis. For this reason, every record
dictated by H. was the direct result of introspection exercised durmg the
period occupied b}^ the stimulus. We have laid stress on this peculiarity,
because the majority of persons in this country seem to belong to the group
of those who depend on visual images, and approximate, at any rate as far as
somatic sensations are concerned, to the condition of H.

Since H. was at the same time collaborator and patient, we took unusual
precautions to avoid the possibility of suggestion. No questions were asked
until the termination of a series of tests ; for we found it was scarcely possible,
in the long run, to ask even simple questions without giving a suggestion
either for or against the right answer. Sounds and movements, that would
have conveyed no information to an ordinary person, would disturb H.'s
judgment in a case requiring fuie discrimination. The clinking of ice against
the glass, the removal of the kettle from the hob, tended to prejudice his
answers and destroyed that negative attitude of attention essential for such
experiments. R. was therefore particularly careful to make all his prepara-
tions beforehand ; the iced tubes were filled and jugs of hot and cold water
ranged within easy reach of his hand, so that water of the temperature required
might be mixed silently.

Towards the end of a series of observations with finer tests over an area of
defective sensibility, H. would frequently become uncertain in his answers,
because he had forgotten his sensations with the coarser forms of the same
stimuli. He might, for instance, speak of contact with the neutral tube as
warmth. But occasional unexpected stimulation with a tube at 38° C. would

A HUMAN EXPERIMENT IN NERVE DIVISION 245

at once correct this tendency, and throughout the further observations the
neutral tube would be recognised with certainty. After a long series of "double
ones," the application of the compasses widely separated so as to produce a
definite sensation of two points frequently produced a similar steadying effect.

At first, we marked out both the affected area of the forearm and back
of the hand into squares of approximately 1 cm. But we found the larger
area on the forearm unmanageable, especially during the period when sensation
changed rapidly. We therefore confined our attention, for the more minute
investigations, mainly to a portion of the radial half of the back of the hand
5 cm. in every direction. This was marked out as follows : the hand was laid
flat on the table and a line drawn along the axis of the third metacarpal bone.
This corresponded almost exactly to the boundary between the normal and
affected parts of the back of the hand. As base line, we used a fold of skin
over the wrist which was prolonged backwards to meet the longitudinal line
at a right angle. From this point, the line along the metacarpal was divided
into seven portions, each 1 cm. in length. From the seventh division a line
was drawn in the direction of the thumb at right angles to the longitudinal
border. This was divided into five portions of 1 cm. in length. By drawing
longitudinal lines from each of these pomts parallel to the axis of the third
metacarpal, and by crossing these by five transverse lines parallel to the distal
base line, a series of 1 cm. squares, twenty-five in number, could be constructed.
On most occasions, we used these squares only as shown on fig. 65, but at times
the whole of the back of the hand was marked out into centimetre squares
(fig. 69). This was a somewhat tiresome procedure and materially disturbed
the sensibility of the affected area. Such marking should never be undertaken
shortly before sensory tests are employed. Moreover, it is extremely difficult,
even with the greatest care, to ensure the exact correspondence of the squares
on different occasions. The skin on the back of the hand is extraordinarily
flexible, and any change in the position of the fingers modifies the size and
appearance of the squares to a remarkable degree. After the base lines had
been settled, we therefore attempted to mark out the squares with the hand
exactly in the position adopted in the photographs. Occasionally, these squares
were not allowed to become erased for long periods (e. q. from January 28 to
March 12, 1906), so that, whatever its faults, we might be certam we were
photographing the same field. ^

On returning to London after each series of sittmgs, life-sized photographs
were taken of the markings on the back of the hand and another set on a
smaller scale, including the forearm.

1 We would suggest that if this experiment is repeated it would be wise to tattoo certain
fixed points on the skin before the operation. This would ensure that each square always occupied
exactly the same area.

CHAPTER III

THE PHENOMENA OF DEEP SENSIBILITY

That the muscles were endowed with sensory nerves was a necessary-
corollary to the universal acceptance of a " muscle sense." But Sherrington
[ 1 10] was the first to demonstrate afferent fibres in the nerves of skeletal muscles.
By degenerative methods he traced their course to the muscles, and, m the
opposite direction, showed that they entered the spinal cord by the posterior
roots of those segments which gave rise to the motor fibres of the same muscles.
This discovery did not receive the attention which w^as due to it, because it
seemed to be little more than the last stone necessary to support the universally
accepted hypothesis of " muscular sense."

But we long ago suspected that the existence of so many afferent fibres
in the muscular nerves was not connected with the power of estimating
movement only.

At the beginning of their investigation, Head and Sherren were brought
face to face with the problem of " deep sensibility." They found, when all
the cutaneous sensory nerves to a part were divided, that it was not of necessity
totally anaesthetic. But, although they saw that the only structures which
could account for the existence of this sensibility were the afferent fibres in
the nerves of the muscles and tendons, accidental lesions of nerve trunks gave
little opportunity for brmgmg this question to a direct issue. Accidental
lesions usually divide mixed nerves containing both the fibres to the skin and
to the muscles. By chance it may happen that one group has regenerated
whilst the other group remams divided (as in Case 28, p. 214). But it is
impossible to say how far the characters manifested under these conditions
by deep sensibility are normal, and how far they are due to incomplete
regeneration.

We therefore determmed in our experiment on nerve division to bring this
question to a direct issue. A large area of skin was to be robbed of its sensory
functions entirely, but the sensibility of the deep parts was to remain un-
disturbed. By this means, we hoped to have the opportunity of discovering
the nature of the sensibility subserved by the afferent fibres of the nerves to
the muscles and other deep structures. The result far exceeded our expecta-
tion. We fomid that deep sensibility is an important factor in the sum of
afferent impulses which pass into the central nervous system. For the
impulses conducted by the afferent fibres of these deep nerves underlie our

246

A HUMAN EXPERIMENT IN NERVE DIVISION 247

sensations of tactile and painful pressure, of the locality of deep touch, and
of the position of the parts in space.

All these sensory qualities are associated with some aspect of pressure, and
all are undisturbed by the denervation of the skin. They can therefore be
united into one group under the name of " deep sensibility," which will form
the subject of the present chapter.

The observations upon which the statements in this chapter are based
were made between April 26 and July 20, 1903, when cutaneous sensation
began to return to the back of the hand. Durmg this period the sittings
occupied twenty-two separate days ; so that we had ample opportunity for
studying the peculiar behaviour of a part where the skin had been rendered
totally insensitive.

(1) Tactile Pressure

As soon as H. regained consciousness after the operation, he was delighted
to find that no part of the back of the hand was insensitive to a touch with
the finger or similar hard object. The next day he was carefully tested by
Mr. Sherren, who found that over the area of cutaneous insensibility on the
back of the hand a pressure touch with the rounded end of a pencil was not
only appreciated every time, but was localised to within | m. (1-25 cm.) of the
spot touched.

Nine days after the operation, Dr. Rivers summed up the results of an
extended series of observations in the following words : — •

" The most striking features of the examination of May 4 were that slight
pressure on the abnormal area of the skin was appreciated and could be
localised, whilst touches with cotton wool or deformations of the skin, caused
by drawing a hair outwards, produced absolutely no sensation."

Whether a sensation was or was not elicited, when a thick camel's hair
brush was applied to the dorsum of the hand, depended largely on the way in
which the brush was used. If applied suddenly and vertically to the skin so
as to cause a jar, a slight sensation of touch was produced ; but \A^hen the
pressure was made more gradually, no sensation was appreciated until distinct
deformation of the brush occurred. Even in this case slight pressure only
was necessary to evoke a sensation.

In the same way, stroking the part gently with a wisp of cotton wool was
entirely unperceived, in spite of the thick growth of hair on the back of H.'s
hand. But cotton wool, balled together into a " swab," such as is used for
sponging a wound, caused a sensation if pressed upon the affected area. Slight
pressure with such a ball of cotton wool might be perceived when it was put
on or taken off only, and it was possible to place it on the skin with so slight
a pressure that it was not appreciated at all.

The more gradually contact was established between the stimulating object
and the affected part, and the smaller the pressure applied, the less likely was
it that a sensation would result. All our observations showed that parts

248 STUDIES IN NEUROLOGY

endowed with deep sensibility only are especially sensitive to jarring
impact.

Not even stimulation with No. 8 of von Frey's hairs could be recognised,
when applied to the affected area on the back of the hand.

^Yh.en the sldn was gently raised between the finger and the thumb so as to
form a loose fold, it was found to be entirely insensitive, even to grave pressure.

Similarly, no sensation was experienced when considerable traction was
exerted on a hair ; the skin could be elevated to the maximum extent until
the hair was pulled out, and no sensation was evoked. But a scarcely visible
deformation of the skin by pressure was at once appreciated.

On several occasions, when the back of the hand was deeply frozen with
ethyl chloride, touches were distinctly appreciated on the frozen area. On
one occasiori, H. stated that he could recognise no difference between the
touches on the frozen portion and those on the surrounding parts. In this
observation, not only was any possible sensibility of the skin excluded, but
also that of the more superficial layers of the subcutaneous tissues, and it
shows that they are endowed with sensibility at a considerable depth.

Several introspective observations w^ere made on the character of the
sensations of deep touch. On one occasion, H. recorded that without careful
attention, no difference in quality would have been noticed between touches
produced by pressure on the anaesthetic and normal areas. Pressure with the
head of a pm on the normal skin produced a tactile sensation, together with
sensations of slight cold and of hair-stimulation. On the affected area, the
latter elements were no longer present, but the fundamental quality of the
sensation seemed to remain the same, so that when the head of the pin was
passed across the border separating the normal and affected areas, a con-
siderable effort of attention was necessary to detect when the change occurred.
The differences in quality were of such a kind that it is very improbable they
would be noticed by any but a trained observer. On a later occasion, observa-
tions were made by stimulating the normal right hand covered with a thin
rubber glove, when H. noted that the quality of the touches resembled that
experienced from the abnormal area.

The most extended observations were made on the back of the affected
hand, because of the rapidity with which sensation began to return to the skin
of the forearm. But during the short time at our disposal, the ansesthetic
parts of the forearm were found to behave exactly in the same way as the
insensitive area on the dorsum of the hand.

In conclusion, there is no doubt that the back of the hand was so sensitive
to contact, that most observers would have said the sensation of touch was
unaffected.

(2) Roughness

One of the most striking features of a part endowed with deep sensibility
is the ease with which roughness can be appreciated.

A HUMAN EXPERIMENT IN NERVE DIVISION 249

The utility of Graham Brown's sesthesiometer depends on our power of
appreciating roughness, when small cylinders are made to project for a measur-
able distance from a smooth metal surface. When these projections can be
perceived, the sensation is one as if the part was " raked," It was found that,
in this respect, the affected parts of the left hand were in no way inferior to
similar parts of the right hand.

Thus on June 7 the following readings were obtained : —

Right {sound). Left (affected).

0-025 mm. Not appreciated . . . . Not appreciated.

0-033 mm. Slightly rough . . . . More definitely rough.

0-041 mm. Definitely rough . . . . Definitely rough.

There was no gross difference between the two sides, but, if anythmg, the
superiority was on the side of the affected hand. On this occasion, H. dictated
the following note : " When the instrument was moved across the first
interosseous space, I was more certain on the left hand than on the right that
it was smooth or rough. On the sound hand I was more frequently confused
by the sensation which arose from the necessary contact with hairs ; no such
confusing accessory sensations arose on the abnormal hand. The sensation
of raking was much purer on the affected side."

If the anaesthetic skin was gently lifted into a large fold, this roughness
ceased to be appreciated until the projections were extended to 0*65 mm. or
0"75 mm. Even then, the "raking" was rarely appreciated, and it was
doubtful whether this sensation was not due to traction communicated to
deeper structures.

Thus, the power of appreciating roughness is evidently a function of deep
sensibility. Complete anaesthesia of the skin, far from diminishing this
sensation, seems to make its recognition slightly more easy by removing
the possibility of other disturbing sensations.

(3) Painful Pressure

Although the skin of the affected area was totally analgesic to prick and to
the painful interrupted current, excessive pressure produced a characteristic
aching pain over the back of the hand from the beginning of the experiment.

The first measurements with the pressure algometer were made on June 7,
and resulted as follows : —

Eight. Left.

(i .. ..1-5

First series . . . . \i-5 . . . . 2-0

U .. ..20

3-5 .. .. 3 5

Second series . . . . -! 3-5 . . . . 2-0

|l -

(4-0 . . . . 2-5

250 STUDIES IN NEUROLOGY

Another series gave the followmg results, when pressure was applied in the
first interosseous space :■ —

Right. Left.

3-25 .... . . 2-0

2-5 2-5

3-25 1-75

3-25 20

These observations showed so consistent a tendency for lower readmgs
to appear on the affected than on the sound hand that pressure was increased,
until H. said the pain was severe. This point was reached on the left (affected)
side at 3" 5, at 5 on the right (sound) hand.

There were local differences on both sides in the amount of pressure neces-
sary to cause pain, but in every case the readings were less over the affected
area than over similar parts of the somid hand.

Comparative readings were taken over the second metacarpal bone and
over the interosseous space, with the followmg result :• —

Right.

Left.

4 3

..2 2

3 4-25 ..

.. 3-5 3-25

Over the metacarpal bone

Over the muscle of the interosseous space . .

H. thought that the difference between the two hands lay not so much
in the quality of the sensation as in the way it developed. On the affected
side, pain emerged rather quickly as a definite aching from a dull sensation
of deep pressure. On the sound side, the development was more gradual out
of a mixed general sensibility. Desire to withdraw the hand was more urgent
on the affected side. Moreover, H. said, " I feel more frightened at the
application of pressure on the affected side."

Allien the algometer was pressed on a raised fold of skm against counter
pressure of R.'s fhigers, no pain was produced with pressures of 85. On the
normal side, pain was produced with a pressure of 2' 25.

Thus, in conclusion we can say that it is one of the properties of deep
sensibility to answer to the stimulus of excessive pressure by the production
of pain. This pressure pain is apparently wholly due to the activity of those
nervous structures which are not mterfered with by complete denervation
of the skin.

(4) Localisation

The most surprising quality of this deep sensibility is the ease with which
tactile pressure is localised. Three methods were employed for testmg the
power of localisation. First, H. kept his eyes closed, but tried to pomt to
the spot touched with his right hand ; or he was allowed to open his eyes and
point, without contact with the skin, to the place he supposed had been touched.
Lastly, R. touched the affected area at a spot he had marked on a life-sized

A HUMAN EXPERIMENT IN NERVE DIVISION 251

Fig. r3.

Reduced to two-thirds the natural size (May 17, 1903).

Certain spots were marked on a Hfe-sized photograph of H.'s hand. These are shown by black
numbers within a circle of 1 cm. in diameter.

H. was given a similar photograph and marked upon it in each case the spot he thought R. had
touched.

The photograph showing the spots stimulated and that showing H.'s locahsation have been
combined; the marks made by H. are printed in red. Thus, for instance, a red 3 shows the spot
marked by H. as the locality of a stimulus applied by R. to the area marked with a black 3.

The order of stimulation is given in the text.

photograph of the left hand, whilst H. attempted to mark the spot on a similar
photograph. This is the method of Victor Henri [52], and in this case it gave
surprisingly good results.

252 STUDIES IN NEUROLOGY

A fortnight after the operation, on May 9, it was found that of twenty-
nine touches within the affected area, seventeen were quickly appreciated
and accurately localised, six were not localised correctly, and six were not
appreciated at all. It must be remembered, that at this stage the skin over
the affected area was swollen, which somewhat hmdered these experiments.
The passing away of the swelling rendered the later experiments even more
striking.

On May 17 a series of twenty-four observations was recorded by Henri's
method on life-sized photographs. The results were remarkable, and it could
not be said that there was any difference between the two hands in the
quicliness and accuracy with which pressure touches were localised.

R. chose nine spots in various parts of the affected area unkno\\ii to H. ;
these are marked in black on the annexed figures (figs. 63 and 64). The
following table gives the places stimulated in order and the position of the
spots marked by H. on his photograph : —

(2) Localised exactly.

(3) Localised 1'3 cm. from the spot touched,

(4) Localised exactly,

(8) Lay over the interphalangeal joint of the thumb, and was locahsed
near the metacarpo-phalangeal joint at a distance of 25 cm.

(1) Localised exactly,

(9) Over metacarpal of thumb — localised at a spot 2' 5 cm. distant in
interosseous space.

(6) Localised 0*5 cm. from spot touched,

(5) Localised 075 cm. from the spot touched,

(7) Localised I'O cm. on the proximal side of the point touched.

(2) Localised exactly,

(4) Localised exactly, so much so that the mark of the previous record was
identical with that of this stimulation.

(7) Localised I'O cm. from point touched over the same spot as before.

(6) Localised exactly.

(8) Localised exactly.

(9) Localised 3 cm. distal to the spot stimulated.

(7) Localised exactly,

(3) Localised exactly,

(6) Localised exactly,

(7) Localised exactly.

(9) Localised 2 cm. distal to the point stimulated.
(3) Localised exactly.

(8) Localised exactly.
(2) Localised exactly.
(6) Localised exactly.

Point 2 was touched three times and in every case was localised exactly.
Point 3 was localised twice exactly and once 1*3 cm, from the spot touched.

A HUMAN EXPERIMENT IN NERVE DIVISION 253

Fig. 64.

In order to test the localisation over the spots 8, 7, 6, 9 and 3 two photographs of the latera aspect
of the hand were used exactly as described under Fig. 63. These have been combined in the same
way and the marivs made by H. have been printed in red.

Point 4 was localised twice exactly.

Point 6 was twice localised exactly and twice within 0'75 cm. of the spot
touched.

Point 7 was twice localised exactly and twice I'O cm. from spot touched.
The two erroneous localisations fell over the same point.

Point 8 was twice localised exactly. Once it was localised over the
proximal joint at a distance of 2*5 cm.

254 STUDIES IN NEUROLOGY

Poiiit 9 showed the worst localisation of any of the spots chosen, and was
always localised distal to the point of stimulation ; twice 3 cm., and once 2 cm.

Thus, all our experiments showed that the localisation of a touch sufficiently
heavy to cause a sensation was remarkably accurate. This power of local-
isation remained after freezing vAth. ethyl chloride, though, owing to the haste
with which such observations had to be made, it was somewhat less accurate
than at other times.

(5) Spacial Discrimination (Compasses)

In spite of the remarkable power of localisation, H. was entirely unable
to discriminate one from two pomts of the compasses, even when separated
for the widest distance permitted by the size of the affected area on the hand,
6 cm. in a direction longitudinal to the axis of the limb. And yet, over a
similar part of the normal hand, a perfect record was obtained at 2 cm.^

But, as soon as the second point was placed upon the skin a fraction of a
second later than the first, H. at once recognised that he was being touched
in two places.

When the compasses were 3 cm. apart, he called every simultaneous contact
" one," whilst four out of five stimulations with two points successively were
recognised and the fifth was said to be doubtful : —

One point 1111 1

3 cm. •! Two points simultaneously 1 1 1 1 1

I Two points successively 2 2 2 D 2

Even at a distance of 1*5 cm. H. was surprisingly often right in his answers
provided stimulation was successive : —

(One point 11 1

Two points simultaneously 11 1 11

Two points successively 1222 22 D2D

On the sound side the formula was as follows : — ■

rOne point 1 111

1"5 cm. J Two points simultaneously 12 2 2 2

iTwo points successively 2 2 2 2 2

And in every case where a right answer was given, H. recognised whether
the two points were applied simultaneously or successively.

Thus it is evident that the presence of deep sensibility alone does not make
it possible to discriminate tAvo points applied simultaneously.

' Occasionally, when the compasses were applied over the anassthetic skin of the forearm
with the points at distances exceeding 10 cm., H. recognised them as two. But he was clear
that this depended on the localisation of one point at one place and the other in a widely distant
part of the limb. He had no sense of inevitable " twoness, " as when the two points were separated
to a distance above the threshold on the normal skin. The process was one of judgment, in that
he knew he was being touched near the wrist and also somewhere up the forearm.

A HUMAN EXPERIMENT IN NERVE DIVISION 255

(6) Appreciation of Size and Shape

All appreciation of size was lost over the affected area endowed with deep
sensibility only. Even the flat and the edge of a laiife could not be distin-
guished from one another. H, seemed to have no power of telling the relative
size of a series of wax figures, although he at once recognised the relative
pressure with which they were applied.

A small square of 1 cm. was placed on the skin with considerable pressure
and compared with another figure 4 cm. in diameter applied with little pressure.
H. made no statement with regard to the relative size of the objects, but said
the first gave a sense of greater pressure. This was repeated many times on
different occasions with the same result.

All power of telling the head from the point of a pin was entirely absent
over the affected parts.

Unfortunately, the size of the area on the hand did not permit of the
complete application of tests for shape. It was found that even a circle, a
square or a triangle, cut out of wax so that all lay entirely within a 4 cm.
square, could not be distinguished with certainty on the dorsal surface of the
sound hand. But, although the answers were wrong as regards the shape,
H. had a definite sensation of pressure on a circumscribed surface, a surface
with borders and angles. On the affected hand, the sensation was one of pure
pressure accompanied by no idea that the object by which the pressure was
produced had any shape. Thus, on June 22, it was noted that on the back
of the left hand there was a complete absence of any element of shape in the
sensations. Pressure was experienced, and this was well localised, but there
was nothing to indicate that the body producing the pressure had any shape.
But on the sound side there was a distinct impression of form, chiefly of angles
here and there, though the total shape could not be perceived correctly.

When a very large surface was applied, H. thought it seemed to him large,
because he had a visual picture of his hand on which he had certain points of
reference, such as the first and second metacarpal bones with their tendons.
He imagined the object was large, because he perceived a sensation from both
these widely separated places. But this failed entirely if both spots could be
touched strictly simultaneously when the large object was applied to the skin.

(7) Perception of Movement on the Skin

In some of the observations in which the skin was stimulated successively
with compass points, the sensation produced was not so much one of " two-
ness " as of rocking or pushmg on the skin. This led us to test whether the
affected area was especially sensitive both to progressive movement over
'the skin and to rotatory movement of a round object in which the stimulated
area of the skin remained the same.

Slight movements were readily appreciated on the affected side, but we

256 STUDIES IN NEUROLOGY

could not detect any definite difference in sensitiveness between the two
hands.

(8) Recognition of Muscular Movement

Head and Sherren were able to show that perfect recognition of passive
movement of the joints was possible when the nerves to deep parts alone
were intact. In the case of H. we had no means of attacking the problem,
for no part of any finger was totally insensitive to cutaneous stimulation.

But we were able to show that the interrupted current could produce
sensation by contracting the muscles only. Even the slightest contraction
of the abductor indicis or the adductor pollicis produced a distinct sensation
of movement, localised in the muscle. No pain was evoked, unless the muscle
was thrown dnto cramp.

(9) Temperature

The existence of deep sensibility conveys no capacity for appreciating
stimulation with any degree of temperature. Ice and water at 60° C. were
equally incapable of evoking a response over the affected area of the hand.
The parts could be frozen stiffly with ethyl chloride, and H. remained uncon-
scious of any stimulation, provided the normal skin was carefully protected
with a thick layer of impervious material.

This freezing produced a numb aching, in no way allied to a thermal
sensation, but resembling the " numbness " produced by extended exposure
of the hands to severe external cold.

In conclusion, we have shown that the peculiar aptitude possessed by a
part innervated solely by the afferent fibres of a muscular nerve is the appre-
ciation of all stimuli which produce deformation of structure. Pressure or
jarring contact are quickly appreciated and localised with remarkable accuracy.
" Roughness " is as well recognised on the affected as on the sound hand.

Two points can be discriminated if applied successively, but not when
contact is made strictly simultaneously.

Although pressure is well localised, all sense of relative size is lost over the
affected parts.

Excess of pressure produces an aching pain ; and the cramp, caused by
repeated electrical stimulation of the muscles, is at once appreciated.

Pressure, which ordinarily causes a sensation of touch or of pain, produces
no effect upon consciousness when applied to a fold of skin elevated into a
ridge, thus proving that the sensations which are present are not due to any
end-organs remaining in the skm.

The presence of deep sensibility conveys no power of appreciating any
temperature stimulus.

CHAPTER IV

protopathic sensibility

§ 1. — Borders of Dissociated Sensibility

The nature of our experiment laid bare the peculiar qualities of deep
sensibility in an unequivocal manner ; for all sensory impulses were destroyed,
except those passing by way of the afferent fibres of nerves of muscles and
tendons. Deep sensibility, as we have described it, is the expression of one
set of afferent impulses, uncomplicated by the simultaneous activity of those
arising in the skin. It cannot be the result of any abnormal reaction on the
part of the central nervous system, nor can it bear any relation to the processes
of regeneration.

But when we attempt to analyse the complex of afferent impulses, which
travel by way of the cutaneous nerves, we are hampered by the following
difficulty : It is not possible to arrange the experiment in such a manner that
a large area of skin shall be rendered insensitive to certain stimuli, Avithout
at the same time gravely impairing its sensibility to those we desire to study.
It is impossible to produce a condition analogous to that of total cutaneous
anaesthesia with complete integrity of deep sensibility. We can, it is true,
find parts that are sensitive to one group of cutaneous stimuli and insensitive
to another ; but even these are areas of lowered sensibility.

In our case, we had even less opportunity than usual for studying the
primary dissociation of cutaneous sensibility. For, on the anterior surface
of the forearm, the loss of sensation to prick and to cotton wool corresponded
exactly. Towards the radial aspect its boundaries were ill-defined to both
stimuli, merging gradually into parts of normal sensibility. But over the
back of the hand lay a narrow border, 2 mm. in breadth, insensitive to cotton
wool but sensitive to prick. Within this area, so vivid was the response that
the skin might have been considered over-sensitive to painful stimuli. Within
ten days of the operation, R. noted that the border on the back of the hand
was " hyperalgesic." H., describing his sensations, said that within this area
the prick of a pin was intensely disagreeable, far m excess of anything experi-
enced on normal parts ; he could not refrain from crying out and withdrawing
his hand. When the hairs were pulled, no response was obtained from any
part of the analgesic area. But, as soon as that portion was reached where the
skm was sensitive to prick but not to light touch, H. at once exclaimed that
the sensation was " stinging " ; he was unaware of the nature of the stimulus,
but experienced a diffuse unusually disagreeable sensation only. If the
VOL. I. 257 s

258 STUDIES IN NEUROLOGY

induction coil was so arranged that it produced a current, scarcely, if at all,
painful over the normal skin, it caused a more disagreeable sensation over the
area of dissociated sensibility.

WTien the normal sldn was pricked, H. at once said, " That was a prick,"
but did not cry out or withdraw his hand. But a prick or any other pamful
stimulus applied within the area of dissociated sensibility produced an immedi-
ate withdrawal of the hand and an exclamation of pain. Yet, in spite of this
vigorous expression of discomfort, he was able to recognise that the dissociated
border was less sensitive even to cutaneous painful stimuli than the normal
skin. A stronger stimulus was required to produce pain, but when once
evoked the sensation was more disagreeable than over normal parts.

Within three weeks of the operation, another small dissociated zone
appeared in the first interosseous space around the distal border of the affected
area. Here sensibility to pamful cutaneous stimuli was so low that they
were followed by no increased reaction. A prick produced a slowly developed,
dull achmg, different from the exaggerated discomfort evoked on stimulating
the border on the back of the hand. Moreover, this small area in the inter-
osseous space was insensitive to all thermal stimuli, and neither cold- nor
heat-spots could be discovered within it. It was evidently so little sensitive
to protopathic stimuli that the skin could respond to painful stimulation
only, and even this response was extremely feeble.

§ 2.— Patx

The back of the hand became sensitive to painful cutaneous stimuli within
eighty-six days of the operation. With the steady increase of this form of
sensibility, the response to the prick of a pin began to assume the characters
of diffuseness and increased unpleasantness, with which the sensations from
the dissociated border on the back of the hand had already familiarised us.

At first the sensibility was low and the innervation evidently defective.
But in time the whole of the back of the hand responded vividly to cutaneous
pamful stimuli, though still anaesthetic to von Frey's hairs and other forms
of light touch. Within this area the prick of a pin produced an intensely
unpleasant sensation of pain. Allien the point was dragged across the hand
from normal to abnormal parts, the sensation became more unpleasant
immediately the boundary of the affected area was passed. The change Avas
so sudden and the new sensation so disagreeable that the border could be
marked out to within 2 mm.

But although the response was greater, H. early recognised that sensi-
bility to prick was still defective. Tested with the algesimeter,^ it was found

^ Li tliis research we used an instrument specially constructed by Dr. Rivers. It consisted
essentiall}^ of ^ sharp needle attached by a flexible joint to a rigid rod. This is weighted and sUdes
freely through two sujjports placed 10 cm. apart, projecting horizontal!}^ from a vertical brass
bar. When the needle is brought into contact with the skin, the full pressure of the weight on
the rod would be exerted on its point, were it not for a fine counteracting spring. Tliis spring.

A HUMAN EXPERIMENT IN NERVE DIVISION 259

that pain was not produced until the instrument registered from 30 to 40,
whilst on similar parts of the normal hand the point was painful at about 25.
Thus, although the sensation produced over this protopathio area was much
more unpleasant than over normal parts, the sensibility, as measured by the
pressure exerted on the point, was distinctly diminished.

Most clinical observations on parts m a protopathio condition must of
necessity be made before this form of sensibility has been completely restored.
For in most cases epicritic sensibility begms to return whilst the measured
pain-threshold is considerably higher than that over similar parts of the
normal limb.

Fortunately, a portion of the affected area on the back of the hand still
remains msensitive to all epicritic stimuli at the end of five years. Here
protopathic sensibility has reached a high grade, and pain is produced as
readily by the algesimeter as over normal parts. But, although the stimuli
are identical, the sensation over the protopathic area is much more unpleasant.
It would be certamly described as " more painful *' by any ordinary patient.

The threshold for painful sensation measured by means of the " pam-
hairs "' is the same over this protopathic area as over an analogous part of
the sound hand. 120 grm./mm.^ was painless, but 150 grm./mm.'- caused distinct
pain over many places on both hands ; with 200 grm./mm. 2, the points from
which the characteristic stmgmg pain could be evoked Avere very numerous.
But, although the threshold was the same in the two cases, the sensation
produced was much more unpleasant over the protopathic area. It radiated
widely and was localised m remote parts ; ever3d;hmg conduced to the
impression that the pain was greater.

Thus, we may conclude that painful cutaneous stimuli produce a more
unpleasant and more diffused sensation within highly protopathic areas than
over normal parts. Moreover, this is the case even when such tests as the
algesimeter and the pam-hairs show that the threshold of painful sensation
still remams higher than normal.

Existence in the normal skui of what may be called " the sense of a point "
renders difhcult all comparison of the threshold for pain over normal and

attached to the rod and to the upper brass support, exactly balances the weight, and the needle
exerts no pressui'e. But if the instrument is pressed on the skin, this spring is no longer com-
pletely extended and the weight exerts a pressure in proportion to the amount, to which it is
no longer counterbalanced by the coiled spring. Tlais is read off on a scale attached to the bar,
that unites the two guiding arms of the instrument.

Six diAisions of this scale corresjionded to a pressure of 1 grni. ; but reachngs below 15 are
of Uttle value as the weight hardly comes into action owing to the friction of the rod. Thus
the corrected readings are as follows : — ■

25 scale divisions = 5 grms.

<j1 >» ,, = D ,,

43 „ „ - 8 „

4" ,, ,, = y „

This instrument suffers from the disadvantage that it must be appHed vertically to the surface.
It is therefore useless for clinical observations, and for this purpose we have employed the form
of algesimeter constructed by Dr. Gordon Holmes (p. 19).

260 STUDIES IN NEUROLOGY

protopathic areas. As soon as a sharp point is brought into contact with the
normal skin of the hand, a person recognises that he is touched with a pointed
object ; even with the indicator of the algesimeter at zero, H. always Ivnew
that he was about to be pricked on the normal skin, although no actual pain
was produced until it registered from 20 to 30 on the scale. Over proto-
pathic parts this sense of a point was absent. Contact with the instrument
produced no response, if jarring was avoided. With gradually increasing
pressure, a diffuse sensation of pain slowly developed, preceded by no indica-
tion that the stimulus was a pointed object. This would certainly mislead
an ordinary patient ; but H. fomid with practice that he could recognise,
over normal parts, when this sensation of a pomt changed to pain.

We have spoken of the wide diffusion of the painful sensation and of its
tendency to be localised in parts widely remote from the point stimulated.
This reference is not fortuitous, but stimulation of the same spot usually
produced a sensation m the same remote area. Thus, the skin between the
knuckles of the index and middle fingers was linked up in a remarkable manner
with the dorsal aspect of the thumb, and an area in the neighbourhood of
the wrist was peculiarly associated with sensations in the proximal part of
the forearm. A full description of these referred sensations will be given in
Chapter VIII.

During the period of returning sensibility to prick, it was evident that
some points within the affected area responded, whilst others remained insen-
sitive. Recovery was not uniform, but the skin became dotted with spots
sensitive to pamful stimuli.

Von Frey has shown that within any chosen area of the normal sldn certain
points respond more readily to painful stimulation. A stiff hair of known
bending strain will cause pain at some spots but not at others. By this means
it is possible to measure the force necessary to cause pain in any part of the
body. These small areas have been called pam-spots on the analogy of the
well-known heat- and cold-spots. But they are in reality points of maximum
sensibility to pain, and when von Frey states that a certain hair evokes sensa-
tion from the pain-spots of a particular area, he in no way denies that hairs
of greater bending strain may cause paui at other points within it.

When we attempted to map out these maximum spots within an area of
recovering sensibility, we met with many difficulties. Spots could be marked
out which were sensitive to painful cutaneous stimuli ; but on again testing
the area, many of these spots would not react, and new sensitive points were
found between them. Moreover, even those which seemed to be constant
from day to day were easily fatigued, and consecutive stimulations rarely
produced the same results. Thus, we prefer to say that sensibility to prick
returned by means of small sensitive spots within the analgesic area ; these
increased in number as the innervation of the part improved.

Long after the back of the hand had become sensitive to prick, the high
threshold for pain showed that its innervation was still defective. But nearly

A HUMAN EXPERIMENT IN NERVE DIVISION 261

five years after the operation the threshold over the permanently protopathic
area had fallen to normal. It might have been thought that this would have
formed a perfect field for the investigation of pain-spots. Here 200 grm./mm.^
everywhere produced a painful sensation, resembling the sting of an insect.
At some points, this was more intense than at others ; but we were unable to
mark out definite pain-spots with this stimulus. When we used 150 grm./mm.^
pam was produced at some points but not at others, exactly as on the normal
skin. Yet when these spots were tested from day to day, they were not
constant. Sometimes they reacted to 150 grm./mm.^, and sometimes they
failed to respond. Here and there, we found a particularly active spot which
sometimes reacted to 70 grm./mm.^. By using hairs between 70 and
150 grm./mm.2, ^j^jg spot could generally be rediscovered, but not always
with the same stimulus.

Thus it would seem, that, when a portion of the skin has long been sensitive
to pain, but does not respond to tactile stimuli, spots of maximum sensibility
may be found equivalent to those described by von Frey. But at no point
is it certain that pain can not be produced by increasing the strength of the
cutaneous stimulus.

In conclusion, we fuid that, during the greater part of the protopathic
period of recovery, the threshold for cutaneous painful stimuli is higher
than normal. But a small area on the back of H.'s hand has remamed in
this condition up to the present time (1908); here the threshold, measured
with hairs of known bendmg strain, has sunk to normal. But in both cases,
even when the protopathic sensibility of the affected area was demonstrably
defective, the sensation of pam evoked radiated widely and was referred
into remote parts. It was more unpleasant and was usually said to be " more
painful " than the pain which followed application of the same stimulus to
the normal skin. We believe that the sensation of pain evoked by punctate
cutaneous stimuli is due to small sensitive areas in the skm analogous to
the heat- and cold-spots. These vary greatly in activity and threshold,
and the " Schmerzpunkte " of von Frey are the pain-spots of the lowest
threshold in any particular part of the skm.

§ 3. — Heat and Cold

No return of sensation to any form of thermal stimulus could be discovered
on the forearm until August 15 (112 days after the operation). We then
found that the proximal portion of the affected area was sensitive to ice-cold.
The next day cold-spots had reappeared over these parts, but nowhere else
within the affected area. Of these spots, four lay within the upper (proximal)
forearm patch ^ and five over the dorsal aspect of the thumb ; five responded

1 The area of disturbed sensation on the foreaini could be divided roughly into three portions
(fig. 51). The upper patch extended for about 2 in. (5 cm.) distal to the scar : this was followed
by a more elongated laatch, passing by means of a narrow neck into the anaesthetic area on the
back of the hand. I'hese will frequently be spoken of as the " upper " and " lower " forearm
patches and the " neck."

262 STUDIES IN NEUROLOGY

uniformly, even to a drop of cold fluid, whilst four were what we have called
spots of the second grade. It is therefore certain that the earliest return of
sensibility to cold coincided with the reappearance of cold-spots.

A similar return of sensation (September 9) within the lower (distal) fore-
arm patch was associated with the reappearance of six cold -spots. When
this area was stimulated with a cold test-tube, a sensation was experienced
in the region of the metacarpal of the thumb. This is the phenomenon of
" reference," which will be considered fully later. We found that this peculiar
sensation at a distance could be evoked by stimulatmg a smgle cold-spot.
The character of the reaction to widespread stimulation was the same as that
of an isolated spot, additional evidence that the sensibility to cold depended
on the reappearance of the cold-spots.

In the same way, the return of sensibility to cold in the neighbourhood of
the base of the first phalanx of the thumb was associated with the appearance
of a single cold-spot. On September 20, we found that whenever the silver
test-tube fell within a certain area of about 1 cm. in diameter, it caused a
brisk sensation of cold. On testing this part with the ice-cold rods, a single
spot was discovered, to which the sensibility of the whole area was evidently
due.

Over the lower part of the forearm, in the neighbourhood of the wrist,
lay a triangular area, sensitive to cotton wool, but entirely insensitive to
prick and to cold. On October 15, for the first time, a test-tube contaming
ice evoked a sensation of cold ; this was due to the reappearance of a single
cold-spot in the centre of the triangle.

Parts on the back of the hand, such as the mterosseous space, first responded
to cold on October 10. Here also the return of sensibility was coincident
with the reappearance of cold-spots. Moreover, in consequence of the wide
distances between them in this early stage of recovery, we were able to show
that sensibility to cold Avas confuied to the neighbourhood of the cold-spots ;
parts which lay between them were insensitive to all cold stimuli.

The return of sensibility to heat was considerably delayed in comparison
with that to cold ; but its relation to the reappearance of heat-spots was
strikmgiy evident. The sparsity of these organs, and the large area of skin
between any two groups of heat-spots, make it peculiarly easy to prove that
they are responsible for all the sensations of heat experienced during the
protopathic period of returning sensibility.

Until October 8, heat produced no sensation anywhere within the affected
area of the forearm or hand. But on this date, 166 days after the operation,
tubes at 45° C. were occasionally said to be hot when applied to the upper
patch on the forearm. Here a definite heat-spot w^as found to have made
its appearance.

On November 1, the back of the hand reacted for the first time to tem-
peratures above 45° C, in the neighbourhood of the head of the first meta-
carpal bone. Here a distmct spot was found which subsequently proved to

A HUMAN EXPERIMENT IN NERVE DIVISION 263

be one of the most constant and active of all the heat-spots on H.'s hand.
By November 9, a second spot had made its appearance, which reacted con-
stantly and vividly, producing a sensation of warmth which radiated over the
greater part of the first interosseous space.

From this time the total number of heat-spots increased greatly ; but by
January 25, 1904, the total number withm the affected area on the back of
the hand did not exceed fifteen. In the space between these spots it was
easily shown that the skin was entirely insensitive to all degrees of heat (figs. 65
and 66).

Fig. 05.

To show the photographic record taken on October 3, 1904, when the affected area of the hand
was in a purely protopathic condition. Within the twenty-five squares each of 1 cm. tlie dots
represent cold-spots, the crosses heat-spots. This photograph records the results of investigations
which lasted six days.

It was evident that the return of thermal sensibility at this stage
was entirely dependent on the existence of cold- and heat-spots. Owing
to the complete absence of sensibility to such stimuli everywhere except
in the neighbourhood of these spots, investigation of their reactions
was particularly easy, and an enumeration of the characters of thermal
sensibility in the protopathic stage becomes an account of their peculiar
properties.

One of the difficulties associated with the investigation of punctate sensi-
bility is the difference in the certainty and vividness with which the various
spots react. Provided the conditions are favourable, some spots respond to
every suitable stimulation, and H. learnt to recognise these first-grade spots,
calling them by different names. They could be marked out with ease, what-
ever H.'s condition might be. But a considerable number of cold-spots

264

STUDIES IN NEUROLOGY

responded with certainty only after a night's rest, when first stimulated, or
when the rod had been recently removed from the ice. Such second-grade
spots can be found over normal parts, but their discovery within a protopathic
area is made easy by the total absence of any but punctate thermal
sensibility.

Some of these second-grade spots will be found recorded on one photo-
graf)h, some on another, and it is their existence which makes the marked
area appear so different on various occasions. For instance, on a certain
Saturday evening (July 9, 1904) all the cold-spots that could be discovered
were those with which we had been familiar for many previous months. Next
morning, we not only confirmed those marked out the night before, but

Fig. 66.
Lateral view of the hand taken on October 3, 1904.
The dotted line encloses the area of diminished sensibiUty. The unbroken line on both Figs. 65
and 66 encloses the parts in a condition of protopathic sensibiUty only.

obtained a response from a considerable number of other spots. On the
third day, many, but not all, of these additional spots could be confirmed :
but every one of those marked out on Saturday night, w^hen H. was fatigued,
responded readily throughout the whole sitting. Thus, it can never be said
at any moment that all the cold-spots in existence have been marked. How-
ever carefully the squares may have been examined, it will always be found
at another sitting under different conditions that some spots have escaped
discovery and that some previously recorded no longer react. But, by extend-
ing the sittings over several days, and by preventing for long periods the
disappearance of the marks on the back of the hand, we were able to show
that, at this stage of recovery, wide spaces existed where the skin never reacted
to punctate thermal stimuli.

Von Frey long ago used a fine drop of ether, or even cold water, for dis-

A HUMAN EXPERIMENT IN NERVE DIVISION 265

covering cold-spots, and we found that those of the first grade responded even
to the drop of ink used to record their position. A spot was discovered by
means of the ice-cold rod and then marked with coloured fluid at the tem-
perature of the room. This produced a sensation of cold if the spot was an
active one ; the antecedent stimulation with the ice-cold rod did not exhaust
a first-grade spot sufficiently to prevent an active response, even to so feeble
a punctate stimulus as a drop of fluid at a temperature of about 13° C. to
18° C. This " reaction to marking " became, therefore, a useful criterion
of the activity of any particular cold-spot.

Among the heat-spots we found fewer differences in activity. Most of
them reacted constantly to suitable stimuli, and could be roused to activity
time after time at short intervals. For mstance, we never failed to discover
those within the affected area in the adjacent angles of 26 E and 25 D. On
the normal part of the back of H.'s left hand, a spot in the fourth interosseous
space and the spot in the extreme upper corner of square 26 A responded on
every occasion. So constant was this last spot that we were able to use it
as a test for the accuracy with which we had marked the vertical base Ime
of the system of squares.

The heat-spots are not only less numerous than the cold-spots, but they
respond more constantly to suitable stimuli. Most of them are so isolated
that their position can be rediscovered without difficulty and recorded with
certamty. Some confusion arose at first in our records, because we did not
recognise that some of the heat-spots lay in groups. Thus, in the adjacent
angles of the squares 26 D and E, 25 D and E, lay a number of spots so close
together that they were difficult to separate : sometimes one, sometimes
another member of this constellation appeared m our photographs. In the
same way, at the angle between 23 E and 22 D, lay spots which were sometimes
recorded as lymg in the extreme lower corner of the one or the extreme upper
corner of the other square. But many like 26 A and 25 B lay completely
isolated. Such spots were rediscovered or not according to the activity of
their reaction ; there was no doubt as to their position when once they
responded to the warm point.

The most striking fact revealed by our photographic records, extending
over nearly four years, is the large number of squares on the back of the hand
from which heat-spots were uniformly absent. These squares remained
totally insensitive to all degrees of heat, until after the return of sensibility
to light touch. Out of the twenty-five squares, thirteen were completely
devoid of heat-spots.

Fig. 67 shows the position of the heat-spots within the twenty-five squares
on the back of the hand from photographs taken between the years 1904 and
1907. Many of them were recognised during the period of returning proto-
pathic sensibility; but by April, 1904, twelve months after the operation,
every heat-spot, with one exception, had been discovered. From this time
we were unable to obtain any reaction to punctate heat stimuli from any part

266

STUDIES IN NEUROLOGY

of this area in which a spot had not ah'eady been marked, and most of these
heat-spots are easily demonstrable at the present 'time.

When we consider that these
observations extended over four
years, and were made under vary-
ing conditions of external tempera-
ture and bodily health, it is
remarkable with what constancy
many of these spots reacted.

By collatmg the photographs
taken on eighteen occasions at
the close of the observations,
which were extended in some cases
over weeks or even months, we
obtained the followmg results : —

Of the sixteen positions shown
on fig. 67, thirteen were marked
out on ten or more of the photo-
graphic records as the site of an
active heat-spot. Most of these
are still easily discoverable, in
spite of the return of sensibility
to mmor degrees of heat over the
greater part of this area on the
back of the hand.

Absent.
0

A B

C D E

y i r> ]

' V ft

- _ Q} -z -_

1 i

r~\ 1 1

iA 1

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Fig. 67.

To show the position of the heat-spots within the
twenty-five squares obtained by collating the eighteen
photographic records.

Where a group of spots are enclosed they lie so
thickly that sometimes one and sometimes another
appeared on the photographs.

The numbers from 22 to 26 follow the longitudinal
axis of the third metacarpal. The letters A to E lie
directly at right angles across the back of the hand
(cf. Figs. 65 and 66).

Present.
Group at the angle of 26 E, 25 E and 25 T) 18
26 A . .

25 B . .

26 El . .
26 Bi . .
25 D' . .
22 E . .

24 E

. .

. . . .

. .

. . . .

. .

13 consecutive times after

4 (aft

er Jan. 29,
1906)

Kand22D .

discovery (Dec. 5,
. 13

1904)

13 (1 doubtful)

G
5

. . . .

•

10
13
13

Croup at the angle of 23 T,
Of this group 22 D- was

2G E-'

26 B^

25 D'

24 B

22 D'

22 A

It is difficult to make an analogous study of the distribution of the cold-
spots on account of their greater number and the proportional increase of

A HUMAN EXPERIMENT IN NERVE DIVISION 267

those of the second grade. This leads to a confusing diversity in the records.
For when many cold-spots lie within each centimetre square, it is less possible
to be certain of their identity than w^hen it contains a single constellation.
If two or three heat-spots are massed in the corner of a square, it matters
little whether one or other of the group reacted on a particular occasion ;
they form an isolated unit in a wide area insensitive to heat. But it matters
greatly if one member of a group of cold-spots Avas marked at one time, whilst
a second one appeared on another record. A comparatively small diversity
in response will materially change the relative position of the marked spot
to the remaining groups within the
same square and may make sub-
sequent identification impossible.

On three occasions (October,
1904; March, 1906; and August,
1907), we not only made the usual
photographic records of the spots
which reacted at the time, but we
also recorded on key-maps the site
and characters of the various first-
grade spots deduced from continu-
ous observations extending over
several weeks (fig. 68).

On collating these records,
sixty-eight points in all were found
to be marked as the site of cold-
spots ; of these, thirteen were pre-
sent in all three sets of maps and
photographs. But the uniformity
with which these spots were
recognised depends not only on the readiness with which they responded,
but to some extent on their position. Two lying in close proximity to heat-
spots of the first grade (26 A, 25 D) could never be missed. Others lay in
some peculiar situation which made their recognition unusually easy. Thus,
the square 24 E contamed one spot only. But m a square such as 26 B it is
obvious that several groups of cold-spots are present, some of which were
marked at one time, some at another. Of these No. 3 alone could be recognised
with certainty in all the records.

The average number of cold-spots within the twenty-five squares, obtained
by collating the whole series of photographic records, is fifty-one. On the
photograph taken in March, 1906, at the conclusion of a series of observations
lasting over many weeks, the cold-spots numbered in all fifty-eight, of which
twenty-eight were said to belong to the first grade. But these spots are so
unevenly distributed that in most of the photographs seven squares contain
none at all.

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Fig. 68.

To show the position of the cold-spots within the
twenty-five squares compiled from the records of
October, 1904; March, 1906; and August, 1907.

268 STUDIES IN NEUROLOGY

General fatigue plays a considerable part in the ease with which a sensa-
tion can be evoked from temperatnre-spots even over normal parts. After a
tiring day, H. was able to mark out those of the first grade only, and could
obtain no reaction from the many second-grade spots which were easily
discovered after a night's rest.

If first-grade spots are selected for examination, it is not difficult to show
most of the phenomena of spot-sensibility on the normal skin. But in our
case the demonstration was greatly facilitated by the entire absence of any
temperature sensibility apart from spots.

The range to which heat- and cold-spots react varies considerably according
to the temperature of the hand and to other conditions, of which fatigue is
the most important. But at no time could we find a heat-spot from which
any sensation could be evoked by any temperature below 37° C.

At first, few heat-spots responded to temperatures below 45° C. ; but as
recovery progressed, the first-grade spots began to react to 40° C. Two spots
only were sensitive to 37° C. under favourable conditions. Even now that
part of the back of the hand which remains in a condition of protopathic
sensibility is still insensitive to temperatures below 37° C. ; the temperature
most favourable for evokmg a sensation of uncomplicated heat still lies between
about 44° C. and 48° C. At 50° C, a stinging is produced which complicates
the purity of the sensation of heat by the introduction of a new element.

We wish to warn observers against the difficulties caused by using too high
temperatures. Over a first-grade spot, 55° C. produces first a sensation of
heat ; this is accompanied by a peculiar tingling, foreign to spot-sensation
in its pure form. It resembles more clearly the tingling produced by a mild
but painful interrupted current. This sensation increases rapidly in intensity
and ultimately ousts the warm sensation from consciousness. Finally, an
intense pain is produced, in which H. can recognise no element of heat. This
would not be called hot but for the antecedent sensation of warmth and for
the fact that, in ordinary life, this painful sensation usually arises in conse-
quence of excessive heat.

At about 50° C. the pleasant feeling-tone of spot-warmth is still obvious,
in spite of the presence of a tingling which contains an element of discomfort,
scarcely to be called pain. These sensations are as distinct as if a hot test-
tube and an interrupted current were being applied together. At 52° C,
this tingling rises in intensity and becomes decidedly painful. As soon as
the temperature of the test-tube falls again to about 48° C, the tingling
lessens and the pleasurable spot-heat reasserts itself as if a covering had been
removed.

The properties of heat-spots can be investigated only by working with
temperatures which do not evoke this accessory tingling. This caution, so
necessary for all who work on the normal skin, is equally obligatory when
examining parts in a condition of protopathic sensibility.

The highest temperature to which the cold-spots within the affected area

A HUMAN EXPERIMENT IN NERVE DIVISION 269

reacted varied greatly. External cold, especially when associated with damp-
ness and fog, greatly lowers the sensibility of the hand. No cold-spot reacted
to temperatures above 26° C, even under the most favourable conditions,
and few responded habitually to 25° C.

At first, during the earlier protopathic stages, no sensation of cold might
be evoked by temperatures above 20° C. ; but with rapid recovery of this f orni
of sensibility, the part became increasingly sensitive to temperatures up to
24° C. With this gradual improvement, the first-grade spots responded with
increasing constancy to the same range of temperature.

Five years after the operation, an area between the knuckles of the index
and middle fingers, though highly sensitive, still remained in a purely proto-
pathic condition. Within its limits lie many active cold-spots, but not one
of these reacts to temperatures above 26° C, and many scarcely react to 24° C.

When an area supplied with protopathic sensibility only is stimulated by
means of a cold object, a sensation is evoked which differs greatly from that
produced over the normal skin. When first the cold test-tube is applied, no
result is produced ; the sensation of cold makes its appearance after a short
interval and slowly mcreases, until at last it possesses a quality of freezing,
to an uncomfortable degree. On contact with a correspondmg part of the
normal skin the same tube is at once appreciated as cold. But the unpleasant
quality does not reach the severity of that produced over the affected area.
The difference between the response of the two parts consists, first, in the
slower development of the sensation on the abnormal side, and, secondly,
in the greater intensity of its unpleasant quality. This would certainly lead
an ordinary patient to say that the sensation was '' colder " on the affected
side.

Not only has this sensation on a protopathic area a more unpleasant
quality, but it is diffused over a wider extent. By stimulating a group of
cold-spots with a drop of ether, it is possible to avoid all localisation by way
of deep sensibility. In this manner, we have obtained from a small group of
spots the most intense sensation of cold not confined to the point stimulated,
but affecting the greater part of the abnormal area on the back of the hand.
This wide diffusion would also tend to make an unskilled observer say that
the sensation produced from the protopathic area was " colder " than that
from the normal skin.

Stimulation of an active heat-spot produced a response that could not be
mistaken. The sensation seemed to flash up like a bright light in the darkness.
From January, 1905, onwards, the area on the back of the hand was in a
perfect condition for observing the difference between the effect of heat applied
to these spots or to parts between them. Several first-grade spots lay in an
area of about 5 cm. by 2 cm., which was totally insensitive to cotton wool
after the hand had been shaved. Here no sensation was produced by heat,
unless one of these spots was included within the area stimulated. Moreover,
to be effective, the temperature must have been higher than 37° C.

270 STUDIES IN NEUROLOGY

But at this time the proximal part of the affected area on the back of the
hand had already become sensitive to cotton wool and to von Prey's tactile
hairs. Here a tube at 36° C. produced an immediate sensation of warmth ;
this gradually increased in intensity, and was strictly associated with the
sensations of touch produced by the contact of the tube. Touch and warmth
formed an entity, giving the impression of a single object.

Early in this research H. became conscious that he was frequently confused
about the intensity of the cold of the stimulating object. A test-tube con-
taining water at 20° C. would produce a sensation apparently colder than
that caused by stimulating an active cold-spot with an ice-cold rod.

To investigate this condition, a group of active cold-spots was selected
within a protopathic area, and one of them was stimulated with an ice-cold
copper rod. After an interval, the bottom of a silver test-tube contaming
water at 19° C. was placed over the group of spots. H. invariably thought
that the tube at 19° C. was " colder " than the iced rod. The two stimulations
were repeated m irregular sequence, care being taken that a sufficient mterval
was allowed to elapse between them. Throughout these experiments H. was
unable to recognise by means of his tactile sensations whether he was being
stimulated by the tube or the rod ; in one case, after the tube had been applied,
he said, " That is a good spot," comparing it with the previous stimulation
with the ice-cold rod. The test-tube in every case produced a far more exten-
sive sensation, and H. said that this would certainly have been regarded as
colder by the ordinary patient.

Within wide limits it would seem that the number of spots stimulated is
of greater importance than the intensity of the cold by which the sensation
is evoked. If the two objects are of equal area, the one which is of lower
temperature will produce the more extensive sensation, and will therefore be
called " colder." But an ice-cold rod, which can stimulate one cold-spot
only, will seem less cold than a tube containing water that is only cool to the
normal sldn.

Another factor, which tells in the same direction, is the wide extent of
the referred sensation produced by stimulating a protopathic area. Stimu-
lation of a single spot with an ice-cold rod may produce coldness in a remote
part ; but excitation of a group of spots, even with a temperature of 20° C,
causes a still more extensive referred sensation of cold. This wdll usually be
called " colder " than the sensation produced by stimulating a single spot,
however intense may be the cold employed.

Owing to the scattered position of the heat-spots on the back of the hand
we were unable to perform the analogous experiment with any certamty.

If active cold-spots are stimulated with heat, a vivid sensation of cold is
produced, exactly resembling that caused by a cold rod. This is the familiar
phenomenon laiown as " paradox-cold," and can be demonstrated on the
normal skm. But, over parts in a condition of protopathic sensibility, this
peculiar reaction can be studied with an ease impossible elsewhere. The

A HUMAN EXPERIMENT IN NERVE DIVISION 271

scattered distribution of the heat-spots and the absence of all sensibility to
heat in the intervening spaces makes it possible to find large areas where the
only parts sensitive to thermal stimuli are the cold-spots. Stimulation of
these cold-spots with the copper soldering iron at any temperature above
about 44° C. will evoke a vivid sensation of cold. Moreover, the sensation
has the same qualities as that produced by the cold rod ; it is widely diffused
and tends to be referred into remote parts. If a certain group of cold-spots
has a tendency to produce a sensation in some definite part at a distance, the
paradox-cold will be referred to the same part.

In common with all other observers, we have been unable to produce an
analogous sensation of heat by stimulating the heat-spots with a cold object.
But the experimental conditions are entirely different in the two cases. When
the hand was in a protopathic condition large areas could be found sensitive
to cold only ; but there was no heat-spot that was not surrounded by a con-
stellation of cold-spots. It was therefore impossible to apply cold to a heat-
spot on the back of the affected hand without at the same time stimulating
one or more of the cold-spots which lay so thickly around it.

We were unable to convince ourselves that the prick of a fine needle,
accurately thrust into the site of an active cold- or heat-spot, produced any
thermal sensation. The same may be said of other forms of mechanical
stimulation.

We attempted to discover whether these spots responded to electrical
stimulation, but were greatly hampered by the difficulty that the electrode
was in itself a cause of thermal stimulation. However, we overcame this
source of error by using the head of a small pin which had been warmed to
about 30° C. One pole of the coil was connected with the pin, the other with
a large flat electrode upon which H. rested the palm of his hand. A shunt-key
was placed in the circuit and was controlled by R. The minute testing elec-
trode was placed over one of the active spots and, after we were certain that
no thermal sensation was produced, R. opened and closed the key without
H.'s knowledge. In no case was any true sensation of heat or cold produced.
We must therefore conclude that these temperature-spots are insensitive
equally to mechanical and electrical stimulation.

In conclusion, we believe that all sensibility to heat and cold, present
during the protopathic stage of recovery, is due to the activity of heat- and
cold-spots. Within the twenty-five squares of 1 cm. on the back of H.'s
affected hand, we found sixteen heat-spots and an average of fifty-one cold-
spots. The heat-spots did not react to temperatures below 37° C, and we
found no cold-spot that responded to a cold stimulus at a temperature above
26° C. But paradox-cold can be evoked from the cold-spots of the normal
and protopathic skin with punctate stimuli at temperatures between about
45° C. and 50° C.

Any thermal sensation produced by an adequate stimulus to a protopathic
area tends to be widely diffused and to be referred into remote parts. In

272 STUDIES IN NEUROLOGY

the attempt to estimate the relative intensity of two stimuli, a less cold object
covering a larger area of the skin may evoke a more vivid sensation than one
of smaller size but of lower temperature. H. mvariably thought the former
was " colder " than the latter; and yet if the two stimuli covered approxi-
mately the same area, he could recognise which of them was at the lower
temperature.

§ 4. — Hair Sensibility

The hairs within the affected area of the forearm and hand remained totally
insensitive to all forms of stimulation until Jul}^ 20, 1903, eighty-six days
after the operation. We then discovered that, within the upper patch on the
forearm, lay four hairs from which a sensation was evoked by pullmg. At
a distinct interval after the hair was pulled, H. experienced a slowly developmg
vague sensation which was neither defuiitely pamful nor unpleasant. It
died away, and recurred as a pamful sensation which faded, and agam recurred
as pain. The sensibility of these four hairs varied greatly; but slow de-
velopment and a tendency to recur were the most certam characteristics of
the sensation evoked when they w^ere stimulated. This mode of reaction
of the hairs was the beginnmg of the gradual restitution of a certam form
of sensibility.

On the forearm and over the thumb, the return of painful sensibility was
developed earlier and more widely to prick than to plucldng the hairs. Over
areas where few hairs were painful we found mnumerable points \A^here prick
was distinctly appreciated. But there was no doubt that the upper patch
on the forearm with a larger number of painful hairs was also more sensitive
to prick than the more distal parts of the limb, where these hairs were less
numerous.

On October 3, 1903, 161 days after the operation, we found that the affected
area was no longer completely insensitive to cotton wool. Three days later,
sensibility had so greatly mcreased that a sensation was evoked by cotton
wool everywhere over the forearm. So curious and abnormal was its character,
that the borders of the original anaesthetic area could be marked out precisely,
by noting the point at which the sensation changed when cotton wool was
dragged across the arm from normal to abnormal parts.

Throughout the period during which the hairs of the forearm were regaming
their sensibilit}?^, the skin of the back of the hand had remained entirely msen-
sitive. But on December 3, 222 days after the operation, the thumb and
adjoining portion of the first interosseous space seemed to be sensitive to
cotton wool. Three days later (December 6), cotton wool produced a definite
sensation over the basal and termmal phalanges of the thumb, and over the
back of the hand this stimulus was distmctly appreciated in many situations,
especially within the first interosseous space. When stimuli were repeated
at intervals of a few seconds, a diffuse general painless tingling resulted ; if
a longer pause was allowed to elapse between them, the general tmglmg died

A HUMAN EXPERIiNIENT IN NERVE DIVISION 273

away and Avas slowly renewed. H. was then unable to say exactly at what
point of time the stimulus had been applied which had caused this renewal
of the sensation.

Within less than a week (December 13), a few scattered hairs in the first
interosseous space caused a painful sensation when pulled.

This sensibility of the hairs on the back of the hand rapidly increased.
On January 4, 1904, 254 days after the operation, no part of the affected area
which possessed hairs failed to respond.

This response was of the same extraordinary character as that with which
we became familiar when testing the hairs of the forearm, and consisted of a
genera] tingling. Not only was it diffused widely, but a sensation was evoked
which seemed to lie over parts of the affected area remote from the point of
stimulation. For instance, when the neighbourhood of the index knuckle
was gently rubbed with cotton wool, a tmglmg was produced all over the
metacarpal of the thumb. Moreover, if the hairs were pulled, the pain which
resulted was also referred to the same remote parts as the sensation produced
by stroking with cotton wool.

Here again we were face to face with the same tendency for a sensation
to be referred to remote parts as was the case when a protopathic area was
exposed to thermal or painful stimuli. Moreover, the sensation was referred
to the same situation, whether the stimulus consisted of mechanical stimulation
of the hairs, the prick of a pin, a hot or a cold test-tube.

Throughout the period during which the hairs of the forearm and hand
had grown increasingly sensitive to pulling and to stimulation with cotton wool,
the whole affected area had remained entirely insensitive to the careful applica-
tion of No. 5 of von Frey's hairs. But if it was allowed to touch any part of
the hairs which lay above the surface of the skin, the same diffuse tingling was
produced as with any other mechanical stimulation.

Now, there is no part of the normal forearm or hand where No. 5 does not
produce a sensation, if the point is placed on the windward side of a hair. For
almost every hair is closely associated with one of von Frey's touch-points.
The total failure of the affected area to react to No. 5 showed, either that the
threshold was abnormally high, or that the hairs had become endowed with a
form of sensibility independent of that usually called light cutaneous touch.
The latter hypothesis seems to be the correct one. For when normal hair-clad
parts are shaved, it is found that the skin, at any rate of the forearm and hand,
remains sensitive to cotton wool. But as soon as the affected area was shaved,
cotton wool no longer produced a sensation of any kind, and the original
anaesthetic borders could be marked out as accurately as on the day after the
operation. The peculiar reaction we have described is therefore associated
solely with the innervation of the hairs.

Fortunately, a small portion of the hairless skm of the thenar eminence
was included within the anaesthetic area. In spite of the universal development
of this tingling reaction to cotton wool over the hair-clad parts of the affected

VOL. I. T

274 STUDIES IN NEUROLOGY

skin, this portion of the thenar eminence remained throughout the whole of
this period, insensitive to cotton wool and to von Frey's tactile hairs. ^\Tien
cotton wool was applied in such a way that it was distmctly appreciated over
the normal parts of the thenar emmence, all sensation was lost in the neighbour-
hood of the boundary of the affected area. On moving the cotton wool further
in the radial direction, the typical tinglmg sensation was evoked and the cotton
wool was again appreciated, but in a new way. This was particularly well
seen in the region of the head of the metacarpal of the thumb, where some
long hairs tend to lie athwart the axis of the bone. As soon as the tips of these
hairs were reached, H. called out, " Hair stimulation." He said, " I recognise
the extreme difference between the two conditions. The skin of the normal
thenar eminence gives rise to a sensation different from that produced by stimu-
lating normal hair-clad parts. During the observations described above,
this sensation ceased entirely for considerable periods "' (these coincided with
the stimulation by R. of the hairless insensitive portion of the thenar eminence).
" Suddenly an entirely new sensation made its appearance which I have learnt
to associate with the stimulation of hairs within the affected area. This is
characterised by a diffuse tmgling, and by extraordinary reference to parts at
a distance."

The part of the skin of the hand which lies between the knuckle of the index
and middle fuigers still remains in a condition of protopathic sensibilitj^ So
long as the hairs are intact, cotton wool causes an unusually intense tingling
sensation, but as soon as the part is shaved it becomes entirely insensitive to
cotton wool, ^^^lether the hairs are intact or not, careful stimulation with
von Frey's No. 5 fails entirely to elicit any sensation ; and yet, before the
operation, there were many spots in this situation which reacted to this stimulus.

In conclusion, we find that the period of recovery associated with the
existence of protopathic sensibility brings to the hairs a capacity for reacting
to mechanical stimulation. But the resultmg sensation is tingling and diffused,
and tends to be referred to parts remote from the point stimulated. Moreover,
the return of this form of sensibility does not bring to the skm after shaving
any power of reacting to stimulation with cotton wool or von Frey's No. 5.

§ 5. — The Sensibility of the Glans Penis

At an early stage in our observations on the consequences of injury to peri-
pheral nerves, we began to search the body to see if perhaps some part of the
normal skin might exhibit protopathic characters. For if a protopathic re-
sponse is associated with a more primitive form of sensibility, it was always
possible that some area might have remamed normally in this condition. We
then discovered that the glans penis responded to cutaneous stimuli in that
pecuUar manner with which we were already familiar from our study of the
first stage of recovery after nerve division.

On turning to von Frey's account of the glans penis ([34] p. 175) we found

A HUMAN EXPERIMENT IN NERVE DIVISION 275

a brilliant description of a part endowed with protopathic and deep sensibility
only. We can add nothing material to this remarkable description, but shall
attempt to show how exactly in the case of H. the response of this organ to
cutaneous stimuli corresponds to that of the highly protopathic area, which
remains on the back of his hand.

The protected position of the glans hidden away under the foreskin has
no fundamental bearing on the nature of its response. Observations on H..
exactly corresponded with those obtained from another subject who had been
circumcised many years ago.

The glans is entirely msensitive to stimulation with cotton wool and with
the tactile hairs. This is expressed by von Frey in the statement that the
threshold for mechanical stimulation has a high value ; he continues : " Es
stellte sich dabei heraus dass die hohe Reizschwelle bedingt ist durch das
Fehlen der Druckpuncte. Der seinerzeit bestimmte Schwellenwerth ist die
Schmerzschwelle. ' '

As soon as hairs of greater bending strain, the so-called " pain-hairs," are
used, the glans is found to be sensitive to from 70 to 90 grm./mm.^ This
produces a characteristic diffuse boring or stinging pain much more unpleasant
than over the skin of the penis or foreskin ; von Frey specially remarks that
the pain is of a different character from that over the normal skin.

The abnormal behaviour of the glans to painful cutaneous stimuli is well
shown by means of the algesimeter. Wlien the needle was brought into contact
with the skin, such as that of the body of the penis, H. was at once conscious
that he was being touched with a pointed object. At a variable pressure of
from 20° upwards, the sensation became one of pam. But when the instrument
was applied to the glans no sensation was produced until it registered over 20°.
Then, if a sensitive spot had been chosen, pain appeared and was so excessively
unpleasant that H. cried out and started away. This pam was not localised,
but radiated widely and seemed to be situated in the urethra as well as in the
glans. If the point impinged on a less sensitive spot, pain might not be caused
until the mstrument registered 40°. In this case a distinct sensation of deep
touch appeared at about 30°, which merged gradually into the characteristic
diffuse pain as the pressure was increased.

In the same way, an interrupted current almost painless on the normal
skin causes an aching, tmgling sensation over the glans which is extremely
unpleasant. The characteristic " whirring " sensation is absent and is replaced
by a slowly increasing diffused pain.

The most remarkable peculiarities are shown in the behaviour of the glans
to heat and cold. In the case of H., there appear to be no heat-spots except
in the neighbourhood of the corona ; the body and tip of the glans are entirely
insensitive to heat. But cold-spots abound and paradox-cold can be as easily
evoked as from the protopathic hand.

We therefore made a number of observations in the following manner.
The foreskin was drawn back, and the penis allowed to hang downwards. A

276 STUDIES IN NEUROLOGY

number of drinking glasses were prepared containing water at different tempera-
tures. H. stood with his eyes closed, and R. gradually approached one of the
glasses until the surface of the water covered the glans but did not touch
the foreskin. Contact with the fluid was not appreciated ; if, therefore, the
temperature of the water was such that it did not produce a sensation of heat
or cold, H. was unaware that anything had been done.

Prom 0° C. to 21° C. a sensation of cold was always produced which seemed
" colder " than over the skin of the penis. Between 21° C, and 26° C. the
answers were not uniform ; sometimes the water was said to be cool, sometimes
H. did not recognise that he had been stimulated. Above this temperature
he uniformly failed to respond, although 27*5° C. seemed cool as soon as the
water reached the fores km.

With warm water at temperatures below 38° C, no sensation of any kind
was produced until the foreskin was reached. At 38° C. H. complained of a
slight aching, which increased in intensity until at about 43° C. it became
extremely painful. At 45° C. the sensation was usually said to be cold. This
is that paradox-cold, so frequent a phenomenon over the protopathic area on
the back of the hand.

But if the glass was carefully raised, so that the water reached the neigh-
bourhood of the corona without stimulating the frenulum or the foresldn, the
same temperature was called pleasant heat. In the case of the other subject,
heat-spots were present in the neighbourhood of the meatus, and temperatures
above 40° C, were uniformly said to be warm.

So intense and widespread may be the sensation of cold or of heat, that von
Frey speaks of the corona and neck of the glans as the most sensitive parts of
the body to temperature. But these parts do not react to temperatures between
26° C. and 37° C. The threshold, judged by the range of reaction, is obviously
raised, but judged by the intensitj^ of the response, the part would be called
one of increased sensibility to heat and cold. This is exactly the condition
with which we are familiar, from our observations on the affected hand. The
surface of the glans penis is a region highly endowed with protopathic sensibility.
But, in addition, the glans seems to have many of the characters of a part
innervated from the deep system. If the needle of the algesimeter is replaced
bj^ a small piece of cork, no sensation is produced, until the instrument registers
between 30° and 40°. This pressure, however, causes a distinct sensation of
touch, which is usually well localised. As soon as the cork is withdra\Mi and
the sharp needle substituted, pain is produced by this pressure, and the point
of application camiot be localised with any approach to accuracy. We became
familiar with this phenomenon when protopathic sensibility returned to the
back of the hand already imiervated from the deep system of afferent nerves.
But the localisation of tactile pressure on the glans is not of such a high order
as over the hand endowed with deep sensibility only.

Another feature in which the glans resembles a part endowed with deep and
protopathic sensibility is the absence of any appreciation of the relative size

A HUMAN EXPERIMENT IN NERVE DIVISION 277

of the stimulating object. H. could not distinguish from one another a point,
a rod with a circular base 2 mm. across, and one of 2 cm. diameter. But, as
soon as they were applied with different pressures, whatever the size of the
object, the greatest pressure was at once recognised. During the first of these
observations, H. noted that he had experienced no pressure sensations so clear
and definite since the days when the hand was innervated from the deep afferent
fibres only. The defuiiteness of these sensations arose from the fact that they
were uncomplicated by any accessory tactile phenomena.

In conclusion, we believe that the glans penis is an organ endowed with
protopathic and deep sensibility only. It is not sensitive to cutaneous tactile
stimuli, but pressure is correctly appreciated and localised with fair accuracy.
Sensations of pain evoked by cutaneous stimulation are diffuse and more
unpleasant than over normal parts. Sensibility to heat and cold is dependent
entirely on the presence of heat- and cold-spots. If the former are absent from
any part of the glans, temperatures of 45° C. produce a sensation of cold,
indistinguishable from that caused by stimulation with a cold object. In every
case the reaction appears to be more vivid than over normal parts, and yet
the glans is entirely insensitive to temperatures between 26° C. and 37° C.

CHAPTER V
epicritic sensibility

§ 1. — Tactile Sensibility

Throughout the first year after the operation, the sensibility of the
affected area to protopathic stimuli steadily mcreased, the response to a
prick became more uniform, and the heat- and cold-spots more numerous.
But it was not until 365 days after the operation (April 24, 1904), that
the proximal part of the forearm first became sensitive to cotton wool when
shaved. Nearly a fortnight before (April 17, 1904), we had discovered six
spots within this area which responded to No. 5 of von Frey's hairs, even
when care was taken to avoid contact with the projecting stumps of the
hairs.

From this date, the forearm became increasingly sensitive to all cutaneous
tactile stimuli. Step by step with this change, the tingling and referred sensa-
tions gradually dimmished, until it was no longer possible to mark out with
certainty the borders of the affected area on the forearm by means of cotton
wool.

This disappearance of the tendency to refer into remote parts was the most
striking sign of returning sensibility to tactile cutaneous stimuli. When the
sensory condition of the forearm went back durmg the winter of 1904-5, this
phenomenon reappeared as clearly as before. During every subsequent
summer the sensibility improved, and every winter it tended to fall back some-
what. But at the end of four years after the operation, sensation had so com-
pletely returned to the forearm that it was no longer possible, even during the
following winter, to discover any material abnormality in this part of the
affected area. Brushing the hairs with cotton wool no longer caused a diffuse
tmgling and this stimulus was appreciated, even when the forearm was carefully
shaved. Moreover, within the whole area, a multitude of points responded
even to No. 3.

Owing to the detailed nature of our previous observations, we were able
to watch the consequences of returning sensation on the back of the hand with
greater minuteness. Here the first signs of sensibility to cotton wool after
shaving appeared 567 days after the operation (November 12, 1904), in the
neighbourhood of the radial aspect of the carpus and the proximal portion of
the metacarpal of the thumb ; these parts still remained insensitive to No. 5
(fig. 61). But though this response to cutaneous tactile stimuli was very

278

A HUMAN EXPERIMENT IN NERVE DIVISION 279

defective, reference was profoundlj^ inhibited. The sensation evoked was
diffuse, but it was no longer situated in some remote part.

With the coming of the winter cold (December, 1904), the greater part of
the recovering area on the hand again became insensitive to cotton wool after
shaving, and the referred sensations were as definite as before.

It was not until March 26, 1905, that the small patch which had remained
sensitive to tactile cutaneous stimuli, began to extend rapidly again in the
direction of the thumb and first interosseous space. Over almost the whole
of these parts, No. 5 was now appreciated. Steady improvement took place
throughout the summer, and even the hairless portion of the thenar eminence
which lay within the limits of the affected area became sensitive to tactile
cutaneous stimuli.

Accurate localisation of touches with cotton wool now became possible
over the greater part of the back of the hand and the dorsal aspect of the thumb.
Tingling and referred sensations ceased, except over the distal part of the
affected area, which, five years after the operation, has not become sensitive
to cotton wool after shaving (fig. 62).

At the present time, the back of the hand still presents two parts in different
states of sensibility. The proximal part responds to cotton wool when shaved,
to No. 5 and occasionally to No. 4 of the tactile hairs. This includes the basal
phalanx of the thumb. The more distal portions of the affected area remain
in a purely protopathic condition, entirely insensitive to cutaneous tactile
stimuli.

In association with this gradual return of cutaneous tactile sensibility,
H. regained the power of appreciating the " pointedness " of a needle or pin.
Over normal parts of the hand, it is almost impossible to touch the skm with a
sharp point, such as that of the algesimeter, without producmg a sensation
which betrays its pointed nature. This sensation is not painful, but conveys
the impression that the stimulating object is sharp. It was totally absent from
all parts in the purely protopathic condition. Even at the present time, the
highly sensitive protopathic portion of the back of the hand is incapable of
responding to the algesimeter, until it registers 30 or more degrees, and hairs
of from 50 to 70 grm./mm.^ evoke sensation of pressure only.

This power of recognising the sharpness of a stimulating object, under-
Ijdng the discrimination of the head from the point of a pin, is a function
of the appreciation of relative size. It is restored to the affected skin
together with the sensation of cutaneous touch and other functions of epicritic
sensibility.

Thus, when a part previously in a condition of protopathic sensibility
begins to respond to cotton wool after careful shavmg, the diffuse tingling
diminishes, the sensation is no longer referred to remote parts, and correct
localisation becomes possible. At the same time, the power of distinguishing
the point from the head of the pin and the appreciation of relative size are
gradually restored.

280 STUDIES IN NEUROLOGY

§ 2. — Thermal Sensibility

Returning sensibility of the skin to tactile stimuli was associated with a
profound change in the response to heat and cold. Temperatures to which the
protopathic parts were insensitive now evoked a sensation, and both radiation
and reference of heat and cold ultimately disappeared entirely.

These changes could best be studied over the back of the hand ; for during
the eighteen months which preceded the first signs of returning epicritic sensi-
bility, we had become familiar with the position of all the prmcipal heat-
and cold-spots within this part of the affected area. We shall therefore begm
our account of the effect produced by the return of epicritic sensibility with a
description of the thermal reactions on the hand, dealmg later with the
similar changes which occurred in the forearm at an earlier date.

Before the skin in the neighbourhood of the wrist had become sensitive
to cotton wool, we noticed that temperatures of 36° C. or even 34° C. occasion-
ally caused a sensation of warmth (October 23, 1904). This differed materially
from the response obtained by stimulating heat-spots ; it was well localised
and seemed to develop in close association with the touch of the stimulating
object. Moreover, it was evoked from parts where no heat-spots had ever been
discovered. By November 12, 1904, temperatures of 36° C. produced an un-
doubted sensation of warmth over an area which included the site of the most
sensitive group of heat-spots on the hand. But we found that, although the
parts around now responded to 36° C, the spots themselves still failed to react
to any temperature below 38° C.

The results obtained by stimulating this area with low temperatures were
less striking, but seemed to point to the conclusion that an analogous change
was taking place in the sensibility of the hand to cold. Temperatures of 26- 5° C.
and 25-5° C. were said to be cool in the neighbourhood of the wrist, although
no other part of the affected area reacted at that time to anything above 24° C.

It was plain that certain parts of the back of the hand, especially in the
neighbourhood of the A\Tist and over the metacarpal of the thumb, had become
sensitive to temperatures, to which the remainder of the affected area, endowed
with heat- and cold-spots only, did not respond. It was these same parts
which about this time became sensitive to cotton wool when shaved.

Throughout the winter, the hand made little further progress towards
recovery, and at one time seemed to fall back mto an earlier condition. But,
whenever the days were bright and the temperature more favourable, we were
able to confirm the return of sensibility to temperatures between 33° C. and
37° C.

During this period, the hand was in an excellent condition for observing
the difference between the sensations produced from a part innervated by heat-
spots only and those due to stimulation of the recovering area with temperatures
to which not even the most sensitive heat-spot reacted.

Over the centre of the back of the hand (26 and 25 B), lay a group of

A HUMAN EXPERIMENT IN NERVE DIVISION 281

unnsiially, active spots, within an area which did not otherwise respond to
heat ; here the sldn was anaesthetic to cotton wool when shaved and to von
Frey's tactile hairs. No temperature below 38° C. produced any sensation of
heat, and higher degrees caused the characteristic response, radiating widely
and referred to some remote part.

But, over the proximal portion of the first interosseous space and the head
of the metacarpal of the thumb, lay an area sensitive to cutaneous tactile
stimuli. Here 36° C. uniformly produced a sensation of warmth which was
strictly associated with those of touch and pressure. Touch, pressure and
warmth formed an entity, giving the impression of a single object. With
higher temperatures such as 40° C. capable of stimulating the heat-spots in
this region, this sensation of warmth merged gradually into pleasurable spot-
heat. But this differed greatly from the response obtained on stimulating
heat-spots over parts that had not entered on the final stage of recovery ; for
it was no longer referred to some remote part, but was closely associated with
the other local sensations. The coming of the new reaction to warmth had not
only increased the range of the sensitiveness of the skin to thermal stimuli, but
had inhibited the tendency to refer into remote parts.

This part of the hand not only recovered its sensibility to less intense
degrees of heat, but when the weather was favourable, temperatures of 27° C.
began to be appreciated as cool. Throughout the greater part of the period
of this experiment, the external temperature was seldom above 20° C, and the
hand was always adapted to cold to a varying degree. But durmg the summer,
especially of 1906, we made several observations which showed that the proxi-
mal part of the affected area on the hand responded to temperatures such as
27° C, to which the cold-spots never reacted.

This increased sensitiveness to thermal stimuli was not associated with
any increase in the number of the heat- and cold-spots. In fact, it became
evident with the return of sensibility to cutaneous tactile stimuli that many
of the cold-spots were less easily marked out than before. During the purely
protopathic stage of recovery, no sensibility to heat and cold existed, except
in the position of the spots. They were therefore easier to mark out than when
the intervening portions of the skin had become sensitive to the intermediate
degrees of temperature.

But, apart from this technical difficulty, it seemed as if the increased
sensibility diminished the activity of the temperature-spots. First-grade
spots could be discovered as easily as before, although they no longer produced
a widespread referred sensation ; but those of the second grade were less numer-
ous over the proximal squares on the hand than before this part responded
to minor degrees of heat and cold. This was not due to any general change in
the condition of the back of the hand, for the temperature-spots in the distal
squares showed no diminution.

The diminished vivichiess of reaction, the increased range of sensibility
and the inhibition of reference into remote parts were not due to an mcrease

282 STUDIES IN NEUROLOGY

of the sensibility which had previously been present, but to the advent of a new
sensory factor. This was proved by the experiment first made m May, 1905,
of cooling the hand. We found that the mechanism upon which this new form
of response depended was peculiarly susceptible to external cold.

After an extended series of observations, we placed the palm of the hand
upon ice for a few minutes. It was then withdrawn and laid upon a towel as
usual, and those parts from which no referred sensations had been obtamed
were again tested with an ice-cold tube. In every case, a sensation was evoked
in some remote part as vivid and distinct as m the days before the hand became
sensitive to intermediate degrees of temperature. External cold had thro"WTti
back the recovering area into a protopathic condition.

Before cooling the hand. After cooling the Jiand.

(5) Local cold. All over interosseous ppace.

(10) Local cold. Up the arm to the scar.

(3) Local cold. Head of first metacarpal and base

of first phalanx of thumb.
(9) A diffuse sensation around Metacarpal of thumb,

the sjDOt touched.

(The numbers represent the part to which the stimulus was applied, as shown on fig. 69,
p. 300.)

By agam warming the hand, the previous condition could be revived ;
reference disappeared from this part of the affected area which regained its
sensibility to intermediate degrees of temperature. Further experiments
on these lines will be described in Chapter VII.

The affected area on the forearm first began to respond to temperatures
between 37° C. and 34° C. in Jmie, 1904. The sensation produced was not
referred to some distant part, but was that of warmth localised to the point
stimulated. At the same time, that portion of the forearm which had become
increasingly sensitive no longer responded so vividly to temperatures below
22° C. Stimulation with 20° C. was frequently said to be neutral over
the proximal patch, although definitely cold over the distal part of the
forearm.

As the general sensibility of the forearm increased, spreading slowly in a
distal direction, the response to temperatures between 18° C. and 40° C. became
very erratic. A stage was reached in which the protopathic hand gave more
definite results and would have been considered more sensitive than the forearm
which had already advanced another stage to recovery. This was due to the
diminished ease with which the full reaction could be evoked from the cold-spots,
inhibited by the newl}^ developed sensory function.

This disturbing uncertainty slowly passed away and the whole of the affected
area on the forearm has become uniformly sensitive to temperatures above
35° C. ; even 33° C, under favourable conditions, produces a sensation of
warmth.

A HUMAN EXPERIMENT IN NERVE DIVISION 283

In conclusion, we found that the return of sensibility to cutaneous tactile
stimuli was associated with a tendency to respond to temperatures between
26° C. and 37° C. This increase in thermal sensibility was not accompanied
by an increase in number of the heat- and cold-spots. Radiation and reference
into remote parts steadily diminished, and the sensations excited by a hot or
cold object became closely associated with those produced by contact at the
point of stimulation. During the recovery of epicritic thermal sensibility, the
hand could be degraded by cooling into a purely protopathic condition ; radia-
tion and reference returned as vividly as before, to disappear on again warming
the hand.

§ 3. — The Compass Test

Tactile discrimination was absent throughout the stage when the affected
area of the forearm and hand was innervated by deep sensibility only. Two
points applied simultaneously were not distinguished, and every application
of the compasses was said to produce a single sensation. H. showed no tendency
to speak of the contact of a single point as " two."

With the return of protopathic sensibility, the compass records became
extremely irregular ; not only were two points said to be one, but one point
was as frequently thought to be two. Over the normal skin, this tendency to
" double ones " commonly appears just before the threshold is reached and a
slight increase in the distance between the two points will produce a record
entirely free from mistakes. But in the protopathic stage, however highly
the skin is endowed with this form of sensibility, uncontrolled by epicritic
impulses, the single point frequently produced a double sensation even although
the double stimuli were made with the points 10 cm. apart.

At a later period of recovery, when part of the affected area had become
sensitive to cutaneous tactile stimuli, this doubling of the single point rendered
all attempts to obtain an accurate threshold impossible. We were, however,
able to show that it was peculiarly liable to occur, when one point of the com-
passes fell over distal parts of the limb, which were in a less advanced stage of
recovery. Thus, in the forearm better records were obtained when the single
point was applied in the upper patch than in the lower (distal), although the
double stimulations were always made over the same spots.

This phenomenon of " double ones," as it occurred during H.'s recovery,
seemed to be based on several different conditions. Stimulation with a single
point sometimes produced two equally distinct tactile sensations or one was
more distinct than the other. Lastly, the sensation was occasionally of wide
longitudinal extent, and so gave the impression that it was caused by two points
at a distance from one another.

At the same time, stimulation with two points was sometimes called " one,"
because it produced a single tactile sensation with no abnormal quality ; or
the sensation was that of one point which seemed abnormally heavy. This
was extremely puzzling, because its singleness compelled H. to call it " one,"

284 STUDIES IN NEUROLOGY

although the additional heaviness led him to think that it must have been
produced by two points.

These abnormalities seem to be due for the most part to the radiation and
reference so characteristic of protopathic sensibility. In the case of the hand,
where one part still remains in a protopathic condition, the records are still bad
in proportion as one point of the compasses falls within the limits of this area.
Moreover, on those occasions when the sensibility of the skhi fell back into an
active protopathic state, in consequence of unfavourable external conditions,
the records even at 8 cm. became almost worthless.

In spite, however, of the difficulty caused by these " double ones," we could
watch the gradual return of epicritic sensibility in the lowering of the threshold
at which one and two points produced an indistinguishable sensation. In
November, 1903, when the forearm was still in a purely protopathic condition,
this limit was reached at 6 cm. Together with the return of sensibility to
warmth in June, 1904, a change for the better in this respect came over the
compass records, and in August of the same year, the threshold at which the
compass stimuli became indistinguishable had sunk to 5 cm. Finally, in
June, 1905, a formula was obtamed :• —

1 I 9 R. 1 w.
4 cm. 2 I 9R. iw.

■ — almost comparable with that from a similar part of the normal forearm —

. 1 I 9R. 1 W.

4 cm. 2 I 10 R.

But, although the threshold at which the stimuli of the compasses became
indistinguishable was greatly lowered, every application of the test even at
distances of 8 or 9 cm. produced records containing an unusual number of errors,
both in the recognition of one and of two points. Over the normal forearm, no
mistakes were made, until within about 2 cm. of the distance at which every
stimulus was called " one." But over the abnormal area, even when it had
been sensitive for more than three years to cutaneous tactile stimuli and to
warmth below 37° C, a large number of single compass stimulations were
thought to be double. For instance, on August 25, 1907, we obtained the
following formulae : —

Affected forearm. Normal forearm.

1 I 7 R. 3 W. 1 I 10 R.

6 cm.
5 cm.
4 cm.

2 I 10 R. 2 I 10 R.

1 I 6 R. 4 W. 1 I 9 R. 1 W^

2 I lOR. 2 1 9R. 1 W.

1 I 10 R. 1 I 10 R.

2 I 3 R. 7 W. 2 I 10 W.

In conclusion, we believe that spacial discrimination, as tested by the
simultaneous application of two compass points, is a function of epicritic
sensibility. A protopathic condition of the skin leads to intense confusion,

A HUMAN EXPERIMENT IN NERVE DIVISION 285

in consequence mainly of radiation and reference. The first effect on the com-
pass records of the return of epicritic sensibility is the reduction of the distance
at which one and two compass points produce a similar sensation. Then the
erroneous " double ones " are gradually reduced in number. But, even at
the end of five years after the operation, many errors of this kind were still
present when the compasses are applied, even at a distance of 8 cm. over the
abnormal area of the forearm.

§ 4. — The Sensibility of the Triangle

A month after the operation, we discovered that a small triangular portion
of the affected area near the wrist was in a remarkable condition, insensitive
to a prick but responding to cutaneous tactile stimuli. We failed to recognise
its existence until May 25, 1903, partly because its sensibility was defective
even to those stimuli to which it responded, but principally owing to the con-
dition of the skin produced by the antiseptics. As soon, however, as all
bandages were removed and the forearm thoroughly cleansed of the epithelial
flakes, the remarkable condition of this part of the forearm became evident.

From the first, there was no doubt concerning the main sensory characters
of this area. It had the form roughly of a right-angled triangle with the base
(3 cm.) towards the hand and the hypotenuse (4' 5 cm.) on the extensor aspect
of the wrist. The third side measured about 4 cm. in length (fig. 53).

Like all the rest of the affected area, it was obviously endowed with deep
sensibility. Tactile pressure was appreciated and well localised. The sense
of roughness, measured by Graham Brown's sesthesiometer, was equal to that
of a similar area on the sound wrist.

But, unlike any other part within the borders of the loss of sensation, the
skui was undoubtedly sensitive to cutaneous tactile stimuli ; No. 5 of von Frey's
hairs and, to a less extent. No. 4, were appreciated. Cotton wool produced
a sensation indistinguishable from that over the normal skin, unaccompanied
by tingling, diffusion or reference into remote parts. Gently blowing on the
hairs through a tube was at once appreciated. Within this area, from the day
of its discovery, the point could always be distinguished with certainty from the
head of a pin, although the skin was entirely insensitive to cutaneous painful
stimuli. Localisation, not only of pressure but also of cutaneous tactile stimuli,
was as good as on a similar part of the normal forearm.

The remarkable feature of this area was the complete absence of all sensi-
bility to cutaneous painful stimuli. A prick produced no sensation of pain,
although the stimulus was recognised as a point. Pulling the hairs, so sensitive
to the slightest movement, caused no pain.

The anomalous condition could best be demonstrated by electrical stimula-
tion. Strong interrupted currents unbearably painful over the normal skin
produced the characteristic whirring sensation devoid of any element of pain.
But if the coils were separated so that the current was just appreciated, the

286 STUDIES IN NEUROLOGY

threshold was only slightly higher over the triangle than over the corresponding
area on the normal sldn. (Coil distance, normal 2'5 cm., triangle 4'5 cm.)

Thus, although this area responded to tactile stimuli, its sensibility was less
than normal. Although No. 5 produced a distinct sensation within the triangle,
No. 4 was frequently not appreciated ; but over the normal wTist many spots
responded, even to No. 2. A similar slight diminution of sensibility was shown
in the results of the compass test. Over the normal wrist, when the points
were separated to 3 cm., H. made no mistakes in the twenty applications, and
the threshold lay between 3 cm. and 2 cm. But, over the triangle under similar
conditions, four mistakes were made at this distance : —

o 1 I 8 R. 2 W.

"^ ^^^- 2 I 8 R. 2 W.

When we turn to the observations on the thermal sensibility of this triangle,
we are face to face with many difficulties. Our earlier experiments were made
with ordinary test-tubes of glass, and it was not until August 15, when the
sensory condition had materially changed, that we used silver tubes. Again,
it was difficult to prevent radiation to normal parts when testing an area of
this size. Moreover, we were not at this time fully alive to the importance of
the external temperature ; we did not recognise that in the climate of this
country the hands are usually adapted to cold.

But, in spite of these defects, we can say with certainty that the triangle
remained insensitive to all temperatures below 22° C, until the appearance of
the first cold-spot (October 15, 1903). Careful and repeated examination with
the cold rods and with test-tubes containing ice failed to elicit any sensation
of cold from any part of this area.

Similarly, we could discover no signs of heat-spots until November 9, 1903,
But one of the most remarkable features of this area was its response to heat,
applied not to points but to areas of 1 or more centimetres in diameter. Tem-
peratures of from about 42° C. to 48° C. were at once said to be warm. But if
the tube was at 50° C. or above, it was either called a touch or was said to be
slightly warm, passing quickly into neutral. Had the warmth, appreciated
when the stimulus was at 42° C, been due to radiation, a tube at 50^ C. or above
would have produced it with even greater certainty. Time after time the
relative temperature of two tubes at 44° C. and at 55° C. were compared, when
the former was invariably said to be the hotter of the two.

So far the results of our observations are definite. But one of the greatest
difficulties was the tendency which H. showed to call cold stimuli " warm "
within the limits of the triangle. \Mienever a thermal sensation was produced
at all, it was one of warmth ; some of the most satisfactory warm sensations
were evoked by an ice-cold tube and yet, at this time, temperatures of 50° C.
and above were not appreciated. Even in the later days, when the triangle
had become sensitive to prick, these higher temperatures evoked a sensation
of pam only.

A HUMAN EXPERIMENT IN NERVE DIVISION 287

The first change which occurred in the sensibility of this area was on July 10,
1903, seventy six-days after the operation ; it then became sensitive to painful
cutaneous stimuli, such as a prick and the painful interrupted current. But it
did not respond with a sensation of cold to temperatures below 22° C. until
October 15, 1903, 173 days after the operation, when the first cold-spot was
discovered within its limits. The cold test-tube laid on the skin elsewhere
within the triangle caused no sensation of cold. On November 9, 1903, 198
days after the operation, the first heat-spots made their appearance, and from
that time onwards the return of sensibility took place rapidly.

But throughout the whole of this period, the sensations which returned were
not diffused or referred into remote parts. They were not more but less vivid
than normal and in no way resembled those evoked from the greater part of
the forearm and hand which had assumed the protopathic condition.

Here, owing to a fortunate anatomical peculiarity, the operation had
produced on a small area of skm a condition of dissociated sensibility which was
the converse of that of the protopathic parts. It was sensitive to cutaneous
tactile stimuli, but insensitive to those which would normally produce pain.
Cold was not recognised, and temperatures above 50° C, were not appreciated ;
yet 42° C. to 49° C. seemed to produce a sensation of warmth, and were always
said to be hotter than those of 50° C. and above.

CHAPTER VI

trophic, vasomotor, and pilomotor changes

§ 1.' — Vasomotor and Trophic Disturbances of the Skin

Changes in the nutrition and vascular supplj^ of the part are among the
usual consequences of dividing peripheral nerves. But if the injury is acci-
dental, motor and sensory fibres are commonly destroyed together and much
of the atrophy is due to the paralysis of the muscles. Even changes in the
growth of the nails may be produced by the consequent immobility of the limb
(Head and Sherren, p. 165).

But in our experiment all these sources of error were elimmated. Afferent
nerves were alone divided, and during the period when the arm was immobilised
on a splint, H. could move his fuigers freely.

Care had been taken during the operation to protect the back of the hand
from mechanical injury and irritation by antiseptics. But four days afterwards
(April 29), the analgesic portion began to assume a somewhat swollen appear-
ance. The surface was rough and the skin appeared white owing to the adher-
ence of epithelial scales ; with a magnifiydng glass it had a peculiar translucent
appearance. A week later, the skin over the radial half of the back of the hand
and dorsal surface of the thumb had become melastic and wrinkled like that
of an old man. This want of elasticity produced a sensation as if the back
of the thumb were covered with collodion. But in addition the superficial
layers of epithelium had formed minute bran-like scales ; the affected portion
was drier than the normal skin and the cracks more evident. The whole area
was of a slightl}^ deeper red than the rest of the skin of the hand, and therefore
showed clearly on the photograph taken at this time (fig. 49). The hairs were
disordered and did not lie m sweepmg masses ; they stood up or lay in an irregu-
lar manner, each hair assuming a different direction. The extent of these
changes corresponded exactly with the area insensitive to prick.

The insensitive parts did not sweat, and in the hot weather of July, 1903,
the difference between the normal and affected portion of the hand was strikmg.
The normal skin was soft, moist and velvety, whilst the abnormal area was dry
and inelastic. If a needle was dragged across the back of the hand, the white
marks produced by the scratch disappeared rapidly from the normal skin ; over
the affected portion they remained sometimes for several days as white powdery
lines. Midge-bites, which occurred five days before, were still evident as pmkish
round swellings, although those on the rest of the hand were no longer visible.

288

A HIBIAX EXPERIMENT IN NERVE DIVISION 289

This dryness and absence of sweating began to disappear from the proximal
part of the affected area 112 days after the operation, and they were no longer
present over the forearm after 136 days. But the skin of the hand remained
in an abnormal condition and did not cease to be dry until about 189 days after
the operation (November 1, 1903). With this return of sweating, the hand lost
the peculiar bluish colour which had characterised it throughout the first five
months of the experiment (October 6, 1903).

Evidently the vaso-constrictor fibres and those which govern the sweating
of the skin began to function 107 days after the operation and had regained
their function even over the hand within 190 days.

In spite of these changes in the skm, the operation in no way affected the
growth of the thumb-nail. Before the operation, the nails of both thumbs
were marked with nitric acid and were found to be growmg equally. After-
wards, they continued to grow equally, even when the affected area was supplied
with deep sensibility only and throughout the whole period of protopathic
recovery. The actual amount of growth varied considerably at different
seasons of the year, but this variation affected the nails of both hands to the
same extent.

In July, 1903, as the sequel to an extensive series of observations on the
sensibility of the frozen hand, we noticed that a sore had appeared in the centre
of the affected area, evidently the consequence of a cold bum produced by ethyl
chloride. It seemed to start as a vesicle which had contained a minute quantity
of fluid ; the surface of this blister was removed in the course of washing and a
raw surface was exposed. If protected, this sore tended to heal, but broke
down again in consequence of the small injuries of ordinary life. Thus, any
act which tightened the skin, such as grasping an oar or the handle-bar of a
bicycle, opened the sore again after it had formed a scab. By taking the skin
between the finger and thumb, serum and even blood could be expressed from
its edges.

In this condition the sore remained until 152 days after the operation
(September 24, 1903). It then showed signs of healing and became dry and
scaly. From the periphery, epithelium appeared to be growing in. Speaking
broadly, the surface which a fortnight before appeared callous and unlikely
to heal was now healing soundly and normally. This was coincident with the
return of sensibility to prick to that part of the skin within which lay the sore.
But its extreme proximal edge still remained analgesic, and it was not until
185 days after the operation (October 27), that this part of the hand became
sensitive to prick and this edge of the sore healed finally. The strict relation
between the healing of this trophic ulcer and the return of sensibility to prick
was evident.

§ 2. — The Pilomotor Reflex

Throughout the period when the skin of the forearm and hand was com-
pletely insensitive, it was impossible to produce erection of the hairs within

VOL. I. u

290 STUDIES IN NEUROLOGY

the affected area. Vigorous stimulation of the skin of the chest with ice or
other means would start the condition kno\!^Ti as " goose-skin " which usually
spread to both arms (Mackenzie [74]). Over the sound limb, all the hairs
would be more or less erected, but on the left forearm, those of the affected
area remamed unchanged ; this probably accounted for their disordered
appearance.

With the return of protopathic sensibility, we noticed that the hairs could
again be erected by suitable pilomotor stimuli. The exact date of the return
of this reflex was not noted ; but we gradually became aware that pricking
the skm, pulling the hairs, or the application of the cold tube would occasionally
give rise to a condition of " goose-skin " within the area we were testing.

As protopathic sensibility increased, this reflex could be evoked more easily
from the affected area than from the normal skin. The iced tube placed on
any active protopathic part might produce a widespread erection of the hairs
over both the flexor and extensor aspect of the forearm which not infrequently
spread beyond the limits of the area of defective sensibility. Even brushing
the hairs with cotton wool in this stage of recovery would start a pilomotor
reflex.

With the gradual return of epicritic sensibility to the forearm, this increased
response died away, and at the present time it is no more easy to produce a
pilomotor reflex from the affected area of the forearm than from other parts.

It is evident that the existence of a high degree of protopathic sensibility
renders it easier to evoke a pilomotor effect. This excessive response is
inhibited on the return of epicritic impulses.

Although stimulation of a protopathic area evoked a stronger pilomotor
response, the erection of the hairs withm this area was no greater than else-
where, if the reflex was a general one produced by placing ice upon the chest.
The increased effect caused by stimulating a protopathic area must therefore
have been due to physiological conditions affecting its afferent impulses and
not to any structural change in the central mechanism. Absence of that
control usually produced by the coincident activity of epicritic impulses
allowed those from the protopathic area to exercise a greater influence upon
the central pilomotor mechanism. Had the excessive reaction been due to
an anatomical change in the centre, a reflex evoked by general means, such
as ice applied to the chest, would have produced a greater erection of hairs
over the affected area than elsewhere ; this was not the case.

During the period when the back of the hand was in a condition of active
protopathic sensibility, we noticed that a referred sensation was liable to be
associated with erection of the hairs over the remote area in which it was
situated. Thus, pricldng the region near the wrist would produce not only
a sensation, but also erection of the hairs of the forearm near the scar. If
the stimulus produced a severe protopathic reaction, this pilomotor reflex
would become general ; but if slighter, it tended to appear at the site of the
referred sensation.

A HUMAN EXPERIMENT IN NERVE DIVISION 291

Whilst engaged on these experiments, we discovered that the " thrill "
called forth by sesthetic pleasure is accompanied by erection of the hairs.
In H.'s case, it started in the region of the neck and spread rapidly down
the arms, over the trunk, the thighs and outer aspect of the legs. If he sat
with his arms bared to the shoulder in a carefully warmed room he could evoke
the reflex by reading aloud some favourite poem. At a certain point he
would call out that the thrill was beginning and shortly afterwards the long
hairs on both forearms were seen to be erected, and the characteristic acuminate
appearance was noticed upon the skin. This general pilomotor reflex was
no greater over the highly protopathic area than elsewhere on the arms.

CHAPTER A^I

ADAPTATION TO HEAT AND COLD

After we had convinced ourselves by repeated experiment that the affected
hand behaved differently in the winter and in the summer, we attempted, by
changing its temperature, to alter its reaction to thermal stimuli. We found
that, by laying the palm of the hand upon ice, we could throw back the greater
part of the affected area mto the protopathic condition. Cold had so reduced
the sensibility of the skin that parts, which had almost returned to the normal
condition, reacted as if they were in an earlier stage of recovery.

This led us on to examine the behaviour of the affected area when adapted
to moderate degrees of heat and cold. If one hand is dipped into warm water,
the other into cold, the same object at an intermediate temperature will seem
cold to the former and warm to the latter. This is the well-kno\^Ti experi-
ment on adaptation. We modified it by adapting both hands to the same
temperatures and comparing the sensation produced by the same object
over normal and abnormal parts.

The majority of these observations were made at sittings between
December 2, 1906, and March 24, 1907. By a fortunate chance, the external
temperature was on every occasion almost exactly the same ; the highest
reading was 14° C, the lowest 13° C. All these experiments, therefore, were
begun with the hands adapted to a temperature of from 13° C. to 14° C.

Throughout the following experiments, two regions within the affected
area were distinguished by their behaviour : (1) a purely protopathic part
in the neighbourhood of the second metacarpal and occupying the space
between the knuckles of the index and middle fingers ; (2) that portion of
the affected area, already far on towards recovery, which lay over the wrist
and first metacarpal bone. But, since the latter behaved throughout like a
normal area of lowered sensibility, attention will be directed mainly to the
sensations produced from the protopathic parts of the affected hand.

The simplest form of the experiment was carried out in the following way.

By preliminary observations, we found that a copper block at a temperature

of 29° C. did not appear hot or cold over any part of either hand. Both

hands were then placed in a basin of water at 50° C. After a time, they were

removed, dried and placed in the usual position for testing. The stimulus

at 29° C. now seemed cold when applied to the right hand and to the normal

parts of the left, and cool over the metacarpal portion of the affected area.

292

A HUMAN EXPERIMENT IN NERVE DIVISION 293

But elsewhere over this part of the hand, it produced no sensation of either
heat or cold. So definite was this absence of sensation, that it could be used
to mark out the boundaries of the affected area.

The hands were then put into water containing melting ice. When they
were removed, the copper block at 29° C. seemed warm over the right hand
and over normal parts of the left. Within the affected area, it produced no
thermal sensation, excepting over the metacarpal portion, where it seemed
to be Avarm.

This experiment shows that the thermal sensibility of protopathic parts
did not undergo that shifting of threshold, which can make a temperature of
29° C. seem at one time hot and at another cold.

But the threshold of thermal sensibility over protopathic parts may shift,
although not to this extreme degree. We therefore carried out a series of
observations of which the most complete were made on March 2, 1907. The
external temperature was 14° C. The hands were adapted to water at 45° C,
removed from the basin and dried ; after a few observations, they were
returned to the basin, within which the water was kept at a constant tem-
perature. Thus, they could be maintained in a condition of warm adaptation
for the long period necessary for the following observations. In this condition
33° C. was found to give a neutral sensation over the normal hand and over
normal parts of the left hand; temperatures of 30° C, 31° C. and 315° C.
were called " cool neutral," and 29° C. seemed definitely cold. But over the
protopathic area, none of these temperatures gave any thermal sensation.
Cold was not evoked until the temperature was reduced below 24° C.

Over the right hand and normal parts of the left, 35° C. was said to be
" warm neutral " ; but 37° C. seemed definitelv warm, even at a distance
from heat-spots. Within the affected area, no sensation of heat was pro-
duced, until the stimulus reached 41° C, when it caused a characteristic
outburst over the group of heat-spots in squares 26 B, 26 E, and 25 D ;
elsewhere it caused no sensation.

Thus, when the hands were warm-adapted (45° C), the neutral point over
normal parts seemed to lie at about 33° C. Temperatures of 29° C. were said
to be definitely " cold," and 31*5° C. was called " cold neutral." At the
opposite end of the scale, 35° C. produced a sensation of warmth which rose
to definite heat at 37° C. But over protopathic parts, no temperature above
24° C. caused a sensation of cold, and no sensation of heat was produced by
any temperature below 40° C. Moreover, whether the stimulus seemed to be
hot or cold, the sensation had the characters of that evoked from spots.

When the hands were adapted to water at 13° C, 27° C. was found to be
neutral everywhere over normal parts ; 28° C. and all temperatures above
seemed definitely warm. But over the protopathic area, no sensation of heat
was produced until the stimulus reached from 39° C. to 41° C. A temperature
of 20° C. evoked a sensation of cold from both normal and affected parts of
the hand.

294 STUDIES IN NEUROLOGY

If the water in which the hands are adapted was lowered to 10° C, it
occasionally happened under suitable conditions that a temperature of 22° C.
seemed neutral over normal parts, but caused a definite outburst of spot-cold
when applied to the affected area. We thus produced the paradoxical result,
that parts of low general sensibility reacted definitely to temperatures which
produced no sensation over the normal skm.

These experiments on cold adaptation are more difficult to carry out than
those in which the hand is warmed. Throughout a great part of the year,
the external temperature is so low that the exposed parts of the body are per-
manently adapted to cold. An attempt further to lower the temperature of
the hand may cause it to become blue and cold, and lead to a serious diminu-
tion of general sensibility which frustrates the object of the experiment. Even
18° C. may then produce no sensation of cold over the affected area or any
other part of the hand, the cold-spots may react feebly to temperatures that
are usually effective and the intensity of the referred sensation is diminished.

Thus, dipping the hand mto cold water may produce three separate con-
ditions according to circumstances. Firstly, over normal parts a simple
shifting of threshold may take place ; secondly, a part on the way to recovery
and showing definite signs of epicritic sensibility may be thrust back to a
purely protopathic condition. Thirdly, especially in winter when the hand
tends to be constantly cold-adapted, the application of severe cold may
produce a condition of lowered general vitality, which diminishes the reaction,
even of protopathic parts.

Allien the normal hand is adapted to heat, 33° C. becomes the neutral
point, 35° C. seems to be warm and 31° C. cool. Carefully adapted to cold,
the neutral pomt shifts to 27° C. and all temperatures above 28° C. are said
to be warm.

Now, the highest temperature to which the cold-spots reacted was 26° C,
and most of them did not respond to 24° C. Even when the hand was adapted
to heat, no sensation was produced by any higher temperature. It is there-
fore evident, that some mechanism other than the cold-spots must exist in
the normal skm by which a sensation of cold is evoked with temperatures
between 24° C. and 31° C.

In the same way, when carefully adapted to cold, 28° C. may seem warm
to the normal hand ; yet the purely protopathic part never responded to
temperatures below 37° C. and most heat-spots are insensitive to temperatures
below 40° C. It is equally evident that there must be a mechanism other
than the heat-spots by which sensations of warmth can be evoked with
temperatures between 28° C. and 37° C.

These observations remove the difficulty experienced by Head and
Sherren in proving the existence of the sensation of coolness, apart from
the reaction of cold-spots. Under the usual conditions, working with hospital
patients, they could obtain no sensation of cold with temperatures above
24° C, and they found that even protopathic parts would respond to such

A HmiAN EXPERIMENT IN NERVE DIVISION 295

stimuli under favourable conditions. But we have shown that, by adapting
the hand to heat, there is a range of at least 5° C. above the highest limit of
the cold-spots, within which stimulation of normal parts may produce a
sensation of cold.

These observations may be summed up in the following conclusions :• — •

(1) Over normal parts, the neutral point of thermal sensibility shifts
according as the hand is adapted to heat or to cold.

Over protopathic parts, no such change occurs. The heat-spots do not
react to temperatures below 37° C, even when the hand is adapted to cold,
nor does adaptation to heat raise the highest limit of the cold-spots above
26° C.

(2) It follows that some innervation other than protopathic must exist
in the normal skm, which renders it sensitive to temperatures between 26° C.
and 37° C, and that this mechanism is capable of adaptation within a wide
range.

(3) By carefully adapting the hand to cold, a paradoxical condition can
be reached, m which a temperature of 22° C. produces no sensation of cold
over normal parts, although it evokes a definite sensation from the affected
area. This is due to the fact that protopathic parts are incapable of adapta-
tion to any material extent, and the cold-spots continue to react to 22° C,
although it produces little or no sensation over the normal cold-adapted
hand. By this experiment, parts in a condition of defective sensibility have
been rendered apparently more sensitive to the specific stimulus of cold.^

^ The significance of these experiments depends upon the suj^position that the norn^al and
abnormal parts of the hand do not assume materially different temjieratures after cooling and
warming. To investigate this not improbable source of error we obtained the help of Dr. Bayliss,
who kindly carried out with us a series of experiments on the temperature of the skin with a
thermo-electric junction, in the Physiological Laboratory at University College. We tested
the temperature of the dorsal surface of the hands after they had been warrced in water at 45° C.
and cooled in water at 15° C. Two areas were chosen on each hand, one in the first and the
other in the fourth interosseous space. By this means we tested on the left hand the behaviour
of a normal against an abnormal area of skin ; but, lest these two spots should naturally behave
differently to warming and cooling, we carried out a series of tests over similar spots on the right
hand. The results showed that the small differences in the temperatuio of the noimal and
abnormal parts after warming and cooling, lay within the limits of experimental error. The
following table gives the results obtained in the most satisfactory series : —

Left hand.

Eight hand.

Cooled in water at 15° C.
Warmed in water at 45° C.

First inter-

Fourth inter-

osseous space.

osseous space

. 19-2

19-2

. 30-4

31-4

. 201

19-4

. 31-S

31-6

CHAPTER VIII

LOCALISATION AND SPACIAL DISCRIMINATION

Among the many curious facts elicited by this inquiry, none are more
remarkable tjian those bearing on localisation. At the time when the affected
area was innervated by the afferent fibres of muscular nerves only, tactile
pressure was localised accurately, although two pomts simultaneously applied
to the skin could not be discriminated. Then followed the period when
protopathic sensibility returned, and cutaneous stimuli began to be localised
over some area at a distance from the point of impact. Slowly, with the
return of epicritic sensibility, the power of accurate localisation of cutaneous
stimuli was restored.

Each of these conditions has been described in its proper place ; but many
of our observations are of such psychological interest, that we have deemed
them worthy of more detailed consideration.

(1) Deep Sensibility

After division of all the nerves to any area of the skin, the part is supplied
solely with deep sensibility^ A touch made with a certain amount of pressure
can be localised with remarkable accuracy. At first, our observations were
complicated by the unsatisfactory condition of the skin ; but as soon as the
oedema and swelling had passed away, we could not discover any obvious
difference in the accuracy with which tactile pressure could be localised over
corresponding parts of the two hands. H. visualises strongly,^ and his accurate
localisation over the affected area was best shown when he was asked to mark
the spot touched on a life-sized photograph of his hand (figs. 63 and 64). More-
over, when allowed to indicate the place that had been touched, his answers
were as accurate on the one hand as on the other, though his eyes remained
closed throughout.

But in spite of this he could not cliscrimmate two points apphed simul-
taneously to the skin, even when separated to the greatest distance possible
over the affected area on the back of the hand. Two points applied successively
were at once recognised, even when 1'5 cm. distant from one another.

^ On p. 243 stress was laid on the diflSculties which arise, in consequence of the inability of a
strong visualiser to reproduce cutaneous sensations. But throughout these experiments on
locaUsation and special discrimination, H. locahsed every sensation on a visual picture which
corresponded remarkably with, the proportions of the normal hand. This gave his answers a
definiteness and security, unattainable when the quality of the sensation was in question.

296

A HUMAN EXPERIMENT IN NERVE DIVISION 297

All appreciation of size and shape was lost over this area ; the fiat of a
knife could not be distinguished from its edge, nor the head from the point
of a pin. When a very large surface was applied to the back of the hand,
H. thought it seemed to him large, because he had a visual picture of his hand
upon which were certain points of reference such as the index knuckle and head
of the first metacarpal. It was not possible to apply a large surface to the
affected area in such a way that these points of reference would be stimulated
simultaneously ; and even a small interval between the moments at which
different parts of the stimulating surface came into contact with the skin
was sufficient to evoke the picture of two points. If these points were widely
distant from one another, H. judged that the object must be of large size.
But the more nearly the various distant parts of the affected area were touched
at' the same moment, the less was he able to recognise the extent of the surface
stimulated.

Deep sensibility conveys the power of appreciating the locality of the part
pressed upon, but not the ability to discriminate two points applied to the
skin simultaneously. Nor does it convey any of those sensory qualities
which underlie the appreciation of size and shape.

Head and Sherren were able to show that, if a part possessed deep
sensibility only, the position and movements of the joints could be
accurately recognised. This question did not come to direct experiment in
the case of H., but we can be certain from cases of accidental injury that the
presence of deep sensibility enables the patient not only to localise the spot
touched but to recognise the position of his limbs in space.

(2) Protopathic Sensibility

So long as the affected area was innervated by the afferent fibres of mus-
cular nerves only, the position of a touch was well localised. But with the
first signs of returning protopathic sensibility, localisation became gravely
disturbed. This disturbance took two forms. The sensation seemed to
be diffused to a varying extent roimd the point actually stimulated, and for
this phenomenon we have throughout this paper used the term " radiation."
In the other form there was produced a sensation also diffuse, but situated in
a region remote from the point stimulated ; this phenomenon we term " refer-
ence." Cold or a prick applied to the forearm not only radiated widely but
produced a sensation in the thumb, and H. could no longer recognise which
part of the affected area had been stimulated. With the return of cuta-
neous painful and thermal sensations, the power of localisation, previously
sufficiently accurate, was greatly disturbed.

As protopathic sensibility improved, the radiation greatly increased, and
the tendency to refer the sensation into remote parts became more definite.
H. was conscious of a struggle between the local sensations, evoked by the
pressure of a cold tube, and the coldness which seemed to be situated in some
part at a distance from the point stimulated. In the early days of returning

298 STUDIES IN NEUROLOGY

protopathic sensibility, the former was dominant, and correct localisation
was possible, in spite of the radiating and remote sensations of tingling, cold
or pain. Later^ when protopathic sensibility had reached a high stage of
development, this was no longer the case, unless the tube was applied with
considerable pressure to the skin.

To evade the localisation due to deep sensibility, we employed minute
drops of ether or of ethyl chloride, instead of the ice-cold tube ; the charac-
teristic radiating and referred sensations of cold then appeared unhampered
by the consequences of pressure. Such a stimulus applied to the wrist might
cause the whole affected area on the back of the hand, including the greater
part of the thumb, to become icy cold, and stimulation of a group of spots
on the forearm was followed by an intense coldness over the whole dorsal
surface of th6 thumb.

In these experiments, H. was in every case unconscious of the actual
place of stimulation. He sat with his eyes closed, and in consequence of the
even temperature of the room experienced no spontaneous sensations from
the hand. Gradually out of this state of quiescence arose a more or less
definite sensation of cold, entirely free from any element of touch, pain or
tingling. This seemed to be situated over an area of considerable size, and
was never limited to a point corresponding with that actually covered by the
stimulus. There was no consciousness of anything in contact with the skin ;
the sensation was one of pure cold, and corresponded with nothing previously
experienced by H.

The relative intensity of the radiating sensation and of that referred to
some remote part varied greatly. But in every instance, the stimulus, how-
ever little tactile its character, was accompanied by some difiuse sensation
in a situation approximate to the point stimulated. In some cases this might
be so faint compared with the vivid reference that it scarcely aroused con-
sciousness ; on the other hand, the disturbance around the site of the stimulus
might be so great that the remote sensation would have escaped notice without
careful introspection.

To test the constancy of this reference, eleven situations were chosen
over the back of the hand and marked on a life-sized photograph. These
situations were repeatedly tested between January, 1904, and the end of
1907 with every form of stimulus to which protopathic sensibility responds.

The back of the hand was also marked out into squares, and the position
of the referred sensation determined for each square centimetre (fig. 69).

Of all stimuli, cold gave the best results ; for it could be applied exactly
to any point, whilst with cotton wool the rubbing backwards and forwards
was liable to stimulate hairs which belonged to areas not directly over the
situation desired. Pricking was also unsatisfactory, because of the duration
of its after-effect and the prolonged diminution of sensibility by which a
vigorous reaction to this stimulus was followed. Pulling the hairs was also
comparatively unsatisfactory for the same reasons.

A HUMAN P:XPERIMENT IN NERVE DIVISION 299

The eleven situations selected within the affected area on the back of the
hand were tested on thirty-seven occasions with cotton wool, thirty-five
times by stimulation with an ice-cold tube, six times with the prick of a pin,
and four times by pulling hairs.

As a general rule, the constancy of reference was greater in the case of
the cold tube than with cotton wool ; this probably depends on the difficulty
in limiting the latter mode of stimulation in every case to the same spot. In
order to study reference, cold was always evoked by placing the flat end of
the silver tube on the skin, so that the area covered was well defuiecl and
accurately limited to the region it was intended to stimulate. Cotton wool,
however, had to be swept over the skin with some vigour, in order to elicit
a sensation of sufficient intensity to provoke distinct reference, and, though
every endeavour was made to limit the extent of the stimulus, it must have
been usually wider than the area covered by the bottom of the cold tube.
Further, even if the spot actually touched with cotton wool were strictly
limited, the area of skin affected would be considerably larger, owing to the
slope of the hairs ; for a touch on one spot may, by moving a hair, actually
stimulate a part of the skin 1 cm. or 2 cm. distant. The extent of the referred
sensation was usually greater with cotton wool than with the cold tube,
although the latter was a more intense stimulus. This must certainly have
been due to the larger area stimulated by the cotton wool.

Of all the situations chosen (fig. 69), No. 10, l}ang close to the extensor
tendons of the thumb, produced the most constant referred sensation. When
stimulated with cotton wool, a characteristic tingling was produced in that
part of the forearm which has been called the upper patch and lies in the
neighbourhood of the distal end of the scar. Radiation was present around
the wrist, but reference occurred invariably to the forearm. A cold test-tube
produced equally constant results ; on the twenty occasions upon which a
referred sensation was evoked, it was situated in the same part of the forearm.
Here no confusion was possible between radiation and reference. The one
sensation seemed to be widely distributed over the back of the wrist within
the affected area, whilst the other lay in the proximal part of the forearm.

No. 1, lying between the knuckles of the index and middle fingers, was
another area from which reference to a remote part was almost constant.
Forty-four times (twenty with cotton wool and twenty-four with cold) some
portion of the thumb or its metacarpal was the seat of the referred sensation ;
twice only was it said to be over the radial aspect of the first interosseous
space.

Stimulation of the two neighbouring situations, No. 8 and No. 4, gave
results of almost equal constancy. In the case of the former, reference took
place to the metacarpal of the thumb in forty-six instances (twenty-two with
cotton wool, twenty-four with cold), and ten times to the radial aspect of
the interosseous space, whilst stimulation of No. 8 was followed in fifty-three
cases (twenty-six with cotton wool, twenty-seven with cold) by reference to

300 STUDIES IN NEUROLOGY

the metacarpal or some part of the thumb ; eight times to the radial aspect
of the space and once to the ^\Tist.

The two phalanges of the thumb lay outside the situations originally chosen,

Hippm^^H^ ,f ^^iB^^^^i

■

■ Mp^ ft ^V

HP HP^^ ^^^ \

^^^^^^^^Hrf jh

^^B; -... . ^^E^ '

^^^^^^^^p

P-'

;- 1

^- "

■

>^H

A ^B

r - - - - , - ;

■

^™

29 : \ ■ :

^^1

^^K..

W' \ J

I^H

27
26
25

;

. D ^

(2)

1
■

24
23

1 I

22
21

^ranj^g

i (S) [

«_- i_ i

Fig. 69.

The circular numbered areas show the spots habitually stimulated when investigating the position
of the referred sensation.

The squares marked in unbroken lines are those used throughout the whole research. Those
enclosed within dotted lines were used to determine the position of the referred sensation when
stimulating isolated heat- and cold-spots.

but have lately been the subject of an extended study in connection with the
confhct of referred and local sensations. The terminal phalanx is in the case
of H. entirely devoid of hairs and could not be stimulated with cotton wool

A HUMAN EXPERIMENT IN NERVE DIVISION 301

in its purely protopathic condition. But with cold and with heat, the referred
sensation was in every case situated over the region between the knuckles
of the index and middle fingers.

Reference from the basal phalanx of the thumb took place invariably to
the same part ; but when the fold of skin over the interphalangeal joint was
stimulated, the sensation was referred occasionally to the wrist or to the
index knuckle.

Less constant results were produced by stimulating the remaining situa-
tions on the back of the hand. One cause of this discrepancy, especially in
the earlier observations, was the failure to distinguish between radiation
and reference. As H. Avas in all cases ignorant of the actual position of the
point stimulated, except in as far as he was guided by accompanying sensations
of pressure, he was frequently unable to distinguish the two sensations. But,
if the radiation and reference were widely separated, as when stimulation of the
index knuckle produced a sensation in the thumb, no confusion was possible ;
it was from such situations that the answers were found to be most constant.

Moreover, several of the chosen situations seem to lie within areas which
may refer to two different places. This is well illustrated by the results obtained
from stimulating No. 3 on the dorsal surface of the wrist. On twenty-two
occasions, the remote sensation seemed to be situated in the first metacarpal,
and twelve times in the basal phalanx, making in all thirty-four times to some
part of the thumb. But a definite referred sensation to the forearm was
produced nmeteen times from the same spot. We found that by shifting the
tube slightly we were able to change the position of the referred coldness from
the thumb to the forearm. Evidently No. 3 lay in the neighbourhood of two
areas, one of which tends to be associated with reference to the thumb, the
other to the forearm.

By combining all our observations, made by stimulating chosen situations
or squares marked on the back of the hand, it appears that reference takes
place somewhat as follows. The area on fig. 70, I. refers usually to some part
of the forearm, that on fig. 70, III. tends to refer mainly into the thumb, and
the whole thumb, including a small portion of the radial half of the first
interosseous space, is associated with reference to the region of the index
knuckle. In the same way, stimulation of the proximal patch on the forearm
(fig. 70, IV. A) tended to evoke a sensation in the back of the hand, and the
distal area (fig. 70, IV. B) was similarly associated with the skin over the base
of the metacarpal of the thumb.

As far as we could tell, the various specific sense-organs, cold-spots, heat-
spots and pain-hairs situated in any small area of the skin were associated with
sensations referred to the same remote parts. Heat-spots were so scattered
and so few in number that the material for such a generalisation was scanty.
But whenever the heat-spot was active, it was found that the sensation of
heat was referred to the same area as the coldness produced by stimulating
the adjacent cold-spots.

302

STUDIES IN NEUROLOGY

Stimulation of the area on the dorsal aspect of the thumb, sho^vn on fig. 70, II.
caused a sensation referred to the distal and ulnar aspect of the affected area
on the back of the hand. Conversely, stimulation of this region of the sldn
(fig. 70, III.) caused a referred sensation in the thumb. So constant was this
cross reference that it could be utilised for a series of experiments on inhibition.

During the earlier stages of recovery, we were not sufficiently aware
of the constancy of this cross reference. But we were repeatedly struck

III.

IV.

Fig. 70.

By marking ont the whole of the dorsum of the hand with squares we found that stimulation of the
area sho-mi on I. caused a referred sensation in the forearm in the neighbourhood of IV. A.

Stimulation of the area showTi on II. caused a referred sensation in the region of the index knuckle.

Stimulation of the area showii on III. caused a sensation in the thumb.

Stimulation of the area marked A on IV. evoked a sensation over the dorsal surface of the hand
near the wrist and that of B caused a referred sensation in the thumb.

with the tendency of the proximal part of the affected area on the forearm
(fig. 70, IV. A) to be associated with the area on the back of the hand ;
similarly, stimulation of the distal portion of the affected forearm
(fig. 70, IV. B) tended to be associated with a sensation over the metacarpal
of the thumb. We were, however, unable to work out this relation so com-
pletely on the forearm as on the hand, for by the time reference from the hand
to the forearm was fully established, recovery had so far advanced that the
forearm no longer produced a referred sensation.

A HUMAN EXPERIMENT IN NERVE DIVISION 303

Throughout this long series of observations, reference was always to a
part within the affected area ; it never lay over any normal part of the hand.
Long after the forearm had returned so nearly to a condition of normal sensi-
bility that stimulation with cold was no longer associated with reference, it
was still possible to produce a sensation in the forearm by stimulating the back
of the ^vrist. The parts over the metacarpal of the thumb have so far regamed
sensibiUty that no remote sensation can now be induced by stimulating the
skin. But this part of the hand is still the seat of vivid referred sensations,
whenever the ulnar and distal portions of the affected area are stimulated with
cold or with cotton wool.

Throughout the whole period of protopathic recovery, localisation was
profoundly changed. At the same time, all spacial discrimmation was absent,
including all recognition of relative size. The results obtained with the com-
pass-points were even less accurate than when the hand was innervated by
deep sensibility only. Then the contact of a single pomt was rarely said to be
two ; but in the protopathic stage this occurred repeatedly. The application
of a single point not only evoked a widespread tingling, but also in many
cases a distinct remote sensation which greatly confused the answers to the
compass test.

(3) Epicritic Sensibility

With the first signs of returning epicritic sensibility, reference occurred
less frequently and radiation became dimmished.

In the early part of November, 1904, when the shaved hand first became
sensitive to cotton wool, it was found that a change had come over the nature
of the reaction to an ice-cold tube ; the sensation radiated widely around the
spot stimulated, but was referred less than usual to remote situations. From
those parts, however, which showed no return of epicritic sensibility, such as
the neighbourhood of the index knuckle, the referred sensation was as vehement
as ever.

In December of the same year, the sensibility of the hand went back in
consequence of the winter cold ; radiation and reference were as vivid as in
the purely protopathic condition, and little if any of the affected portion of the
hand was sensitive to cotton wool after shaving. In February, 1905, there was
not a single situation within the affected area from which we did not obtain
a referred sensation. From No. 10 near the wrist it was projected into the
upper patch on the forearm as intensely as before.

With the coming of spring (April, 1905), seven out of the twelve situations
gave local radiation without reference on stimulation with the ice-co.d tube.
There was coincident improvement of sensibility to cotton wool, and the results
of the compass test were the best so far recorded.

In June, 1905, the hand had further improved and a referred sensation
was obtained on stimulation of the parts near the index knuckle only. Sensi-
bility of the shaved hand to cotton wool had greatly mcreased, and the compass

304 STUDIES IN NEUROLOGY

test gave good results at 4 cm. when the points were placed longitudinally so as
to fall as much as possible within the area of partial recovery.

Sensibility agam degraded during the winter of 1905-6, accompanied by
the reappearance of the phenomena of reference and widespread radiation.
We therefore had the opportunity of confirming and amplifying our previous
observations. But it is not necessary to wait for these annual fluctuations
of temperature ; artificial cooling will produce similar changes in the sensibility
of the recovering parts. On July 6, 1905, reference was almost entirely absent
and radiation greatly diminished. But after the palm of the left hand had
been laid upon ice for a short time a referred sensation could be evoked from
every situation within the affected area ; even stimulation of the parts near
the wrist was associated with coldness or tingling in the forearm. Similar
changes were observed throughout the long series of experiments or adaptation
made during the winter of 1906-7.

The inhibition of reference and radiation, which accompanies the return
of epicritic sensibility, is evidently due to the opening up of fresh paths in the
peripheral nervous system. The mechanism associated with protopathic
sensibility is not gradually educated into something higher ; but the conse-
quences of its peculiar activity are checked in the central nervous system
by the coincident existence of epicritic impulses. Inhibited and controlled,
they are ready to burst out in the form of radiation and reference, as soon as
the activity of the dominant mechanism is diminished by cooling the hand.

We therefore determined to test this control, by placing an ice-cold tube
partly within and partly without the protopathic area on the back of the hand.
The distal part of the affected area was still in an actively protopathic condi-
tion during the winter of 1907. It was separated from normal skin by a well-
defined border almost coincident with the line of the third metacarpal bone.
Here we could place an ice-cold tube so that tlie circular area of its base might
be distributed in varying proportion between parts of normal and abnormal
sensibility. When the tube was placed so that one half fell on the normal,
the other on the abnormal side of the border in the region of square 27 A, a
vivid coldness appeared in the thumb which disappeared, and was replaced
by an entirely local sensation. Reference was wiped out as completely as if
a current had been switched off. Sometimes the remote sensation reappeared
in a fainter form to be abolished again completely.

This control of radiation and reference cannot be definitely said to be asso-
ciated with any one factor in epicritic sensibility. The change occurred with
the first signs that the affected hand was sensitive to warmth and to cotton
wool after shaving. The compass test still gave poor results at 6 cm. ; but
it must be remembered that the extent of skin to which epicritic sensibility
was returning was at first so situated that the two points of the compasses
could not be placed simultaneously wdthin it. Later, we always found that
row D gave uniformly better results than row B, which shows that with return-
ing sensibility to warmth and to cotton wool after shaving came an increased

A HUMAN EXPERIMENT IN NERVE DIVISION 305

power of spacial discrimination. This is the only new spacial faculty restored
by the recovery of epicritic sensibility. Tactile localisation and the sense of
passive position were present from the begimiing of the experiment ; spacial
discrimination alone was absent. If therefore the disappearance of radiation
and reference is to be associated with any one element of epicritic sensibility,
it is probably spacial discrimination which is responsible for the cessation of
the abnormally wide diffusion of protopathic sensations.

The results at which we have arrived in this chapter may be summed up
as follows : —

(1) Accurate tactile localisation is possible even when the part is supplied
with deep sensibility only, provided the pressure is sufficient to stimulate the
deep afferent system.

Accurate localisation of cutaneous stimuli does not return until the skm
becomes sensitive to von Frey's tactile hairs and to cotton wool after shaving.

(2) It is possible to recognise the position of the parts in space and to
appreciate the movement of the jomts even though the limb is innervated by
deep sensibility only.

(3) Tactile discrimination, the recognition of two compass points applied
simultaneously to the skin, is impossible in the absence of epicritic sensibihty,
except at distances enormously in excess of the normal.

(4) The protopathic condition is associated with a tendency to produce
sensations in parts remote from the point of stimulation. If care is taken
to avoid tactile pressure, it may be impossible to recognise to what part of the
skin the stimulus has been actually applied.

The existence of epicritic impulses inhibits this tendency to refer into
remote parts. Thus, the first signs of returning sensibility to cutaneous touch
and to minor degrees of heat led to a diminution of these referred sensations.
In the same way, the return of sensation to prick and to the extremes of heat
and cold to a part such as the triangle, previously sensitive to cutaneous tactile
stimuli, was not associated with any tendency to reference. Even coincident
stimulation of an adjacent part in the normal condition seems to have an
inhibiting effect on this tendency of the protopathic sldn.

(5) Localisation is in all probability the sum of two sets of sensations,
one of which arises from deep, the other from cutaneous stimulation. But
with the remaining spacial elements the conditions are somewhat different.
Deep sensibility is responsible for our knowledge of the position of our limbs
in space, whilst stimulation of the epicritic system is necessary to evoke the
power of spacial discrimination. Each of the two systems brings its addition
to the impulses which underlie localisation ; but sense of position in space
depends on deep sensibility alone, spacial discrimination on the activity of
the epicritic system only.

VOL. I.

CHAPTER IX

INTENSITY

Throughout the previous chapters, we have repeatedly dwelt on the
vivid response of protopathic sensibility to painful stimuli. A prick, which
on the normal skin gives rise to little more than a sensation of sharpness, may
in the protopathic condition produce a response so unpleasant that it would
in ordinary language be said to be much more painful. ^ We have little doubt
that the trained psychologist experiencing the two sensations would say that
the pain in the second case was of greater intensity, and, if speakmg in terms
of the sensibility of the skin, he would say that m the protopathic condition
it was more sensitive. On exact examination, he would expect to find that
the skm had a lower threshold for pain, i. e., that pain would be produced with
a smaller stimulus than over normal parts.

Observations made with the algesimeter and ^\ith von Frey's pain-hairs
have sho^\^l that this is not the case. The increased response to painful
stimuh may even occur mth a threshold considerably raised.

For, during a considerable part of the five years that have elapsed since
the operation, the back of the hand was in a condition of low protopathic
sensibihty. Not only was the sldn insensitive to such stimuli as Ught touch
and warmth, but even painful sensations had a higher threshold than over
normal parts. Yet in spite of the incomplete restoration of protopathic
sensibihty, the response to painful cutaneous stimuU was greater than normal.
If attention is paid to the character of the sensation resulting from an equal
stimulus to similar parts on the two hands, the affected area would seem to be
more sensitive on account of the greater painfulness. But if the sensibihty
of the sldn was measured by the threshold of stimulation, the affected area
would be called less sensitive than normal.

This difference came out clearly, when the point of a pin was dragged
across the back of the hand from normal to protopathic parts. The change
was so sudden and the new sensation so painful, that the border could be

^ All unpleasant protopathic sensations are associated with an unusually disagreeable feehng-
tone. Those which are pleasant, such as the heat evoked bj^ stimulating heat-spots, are unusually
agreeable. Thus a temperature of 40° C. applied to a part devoid of heat-spots is less distinctly
pleasant than when it is brought to bear on a group of active heat-spots in a protopathic area.
Conversely, jsain evoked even from a protopathic area of defective sensibility is more disagreeable
than that produced by the same stimulus ai^plied to the normal skin. Li addition to pain, which
is a measurable sensation, we must distinguish discomfort (" Unlust "). In cases of injury to
the spinal cord discomfort may be produced over a totally analgesic area by potentially painful
stimuU {vide p. 405).

306

A HUMAN EXPERIMENT IN NERVE DIVISION 307

marked out to within 2 mm. And yet at the same time the threshold for
painful stimuli was higher than normal over the affected area.

It might be supposed that the exaggerated response of protopathic pain
was due to some incomplete restoration of the functions of the mechanism for
painful sensations, which would diminish or pass away with the lowering of
the threshold to the normal. But this is not the case. Fortunately, a small
part of the affected area still remains in a purely protopathic condition. Here
the threshold for painful cutaneous stimuli does not materially differ from that
over a similar part of the normal hand. But the sensations evoked from the
affected area are still both more unpleasant and of greater extent than normal.
The approximation of the threshold for painful stimulation to that over normal
parts, far from decreasing, seems actually to have increased the vividness,
the extent and the unpleasantness of the resulting sensation.

And yet H., like all patients in this condition, never for a moment doubts
that the protopathic area is one of defective sensibility. Over normal parts
of the hand, it is almost impossible to touch the sldn with a sharp point, how-
ever lightly, without producing a sensation which he knows if increased will
gradually pass into pain. The normal skin responds to a point with a sensa-
tion which is not painful, but which conveys the impression that the stimulating
object is sharp. This is absent over protopathic parts. When the needle
of the algesimeter is applied carefully, even over a highly sensitive protopathic
area, the pressure can be increased without evoking any response mitil the
scale shows about 20°. Then a sensation of pressure is evoked in consequence
of the stimulus to deep sensibility. Increase the pressure further and
at about 30° to 35° pain is produced, either suddenly or as a gradually
increasing ache.

The sensibility of the protopathic area in the neighbourhood of the index
knuckle (fig. 62) has so greatly increased, that the threshold for cutaneous
painful sensations, tested with von Frey's hairs, is now the same as that of a
similar part of the normal hand. But although the threshold for pain over
this highly protopatliic part has sunk to the normal, the sensibihty of the two
areas, tested by means of a sharp point, is fundamentally different. From
the sldn in a protopathic condition, pain is evoked without the preUminary
painless sensation of a point.

These observations show that we must readjust the usual psychological
conception of intensity, at any rate as far as painful sensibility is concerned.

On turning to the phenomena of thermal sensibility, many facts point to
an equal need for revision of the usual views on intensity. On comparing the
sensations from normal and protopathic parts, the same cold tube 20° C. is
commonly said to be colder over the affected area. But, if the threshold be
determined in the usual way by lowering the temperature of the stimulus from
neutral to the just perceptibly cold, it will be found that the protopathic region
will seem to be by far less sensitive. A temperature of 30° C. or even 31° C.
may be called cool over normal parts under favourable conditions, but 27° C.

308 STUDIES IN NEUROLOGY

never produced a sensation of cold over smy portion of the affected area. A
part which reacted with a more vivid sensation of cold when stimulated with
20° C. was incapable of responding to temperatures well within the range of the
normal sldn.

Return of epicritic sensibihty diminishes the vividness of response to
protopathic stimuh. The part of the affected area in the neighbourhood of
the first metacarpal has become sensitive to hght touch after shaving and
responds to minor degrees of heat ; sensibihty is almost completely restored.
Temperatures of 26° C. and 27° C. produce a sensation of coldness and, measured
by all the usual criteria, it is a highly sensitive part. But a tube at 20° C
seems less cold than over the neighbouring purely protopathic area.

The same condition was repeatedly observed throughout the period during
which the forearm was recovering. Thus, on December 1, 1906, 26° C. seemed
cool to the affected area on the forearm but produced no sensation of tem-
perature over the back of the hand ; but 23° C. was said to be cool over the
forearm and intensely cold over the back of the hand. On August 7, 1904,
20° C. produced a cool sensation (" poor cold ") only over the proximal part
of the affected area on the forearm, " good cold " over the distal patch and
"tremendous spot-cold " over the back of the hand.

At this time stimulation of the protopathic area in the neighbourhood
of the wrist uniformly caused a sensation of cold, referred to the proximal
patch on the forearm in the neighbourhood of the scar. By this means, a
colder sensation could be produced than by applying the same tube directly to
that part of the forearm. We are thus face to face \\ith the following significant
anomaly. A cold stimulus evoked a sensation of cold over a certain part of
the forearm ; but, when this stimulus was apphed to a protopathic part on the
hand, it produced a sensation referred to the same area of much greater cold-
ness than that which followed direct apphcation of an identical stimulus to
the same part.

By carefully adapting the hand to cold, a condition can be produced in
which 22° C. continues to cause a vivid sensation of cold from the protopathic
area, but seems neutral to normal parts of the hand. An area of undoubtedly
lowered sensibihty then reacts with a specific sensation to a temperature,
incapable under the circumstances of evoldng a sensation from the normal
skin.

An interesting example of failure to recognise this ambiguity with regard
to intensity in the case of protopathic sensibihty is given by von Frey's state-
ment that the glans penis is the most sensitive part of the body to tempera-
ture. Now we have shown that this organ reacts to thermal stimuh hke the
skin in the protopathic stage after nerve division. It is a part of the body
which is normally devoid of epicritic sensibihty. A tube of 20° C. placed on
the corona of the glans penis is said to be decidedly colder than on the
adjoining skin; but tubes of 27° C. and 28° C, which produce obvious cold
on the skin, evoke no such sensation from the glans. A region which has been

A HUMAN EXPERIMENT IN NERVE DIVISION 309

called the most sensitive part of the body is as a matter of fact one of low
sensibility, if tested by the customary measure of the threshold.

In the case of heat the results are the same ; but, owing to the narrow
range of temperature at our disposal, their demonstration is not so easy.
Merely judged by the vividness of the response, a protoj^athic region would
be called more sensitive than normal. A tube at 40^ C. placed over a group
of spots within the protopathic portion of the back of the hand seemed hotter
than over normal j)arts ; yet this area did not respond to any temperature
below 37° C. When a silver tube containing water at 47° C. was rolled across
the hand from normal to abnormal parts, it became " hotter " over the affected
area. But a tube at 35° C, obviously warm over the normal sldn, no longer
caused any sensation of warmth as soon as the protopathic border was passed.
Judged by the standard of threshold, the protopathic area was less sensitive,
although a temperature of 47° C. seemed hotter than over the normal hand.

At an early stage of recovery, the hairs regained a peculiar form of sensi-
bility to contact. Strolung a hair-clad part with cotton wool produced a
widespread tingUng referred to parts at a distance, identical with those for
the sensations evoked by painful and thermal stimuli. This tingling seemed
to be more intense than the sensation which follows the brushing of normal
hairs with cotton wool. But, when the roots of the hairs were tested by
von Frey's method, not one of them was found to react to No. 5, although
over norma] parts the majority are sensitive even to stimulation with No. 3 ;
and if the skin of the affected area was shaved, it became entirely insensitive
to all cutaneous tactile stimuli.

Whatever the effective stimulus applied to an area in a condition of high
protopathic sensibility, the specific sensation evoked will seem to be more
vivid than that over normal parts. A prick will seem more unpleasant, cold
will appear to be colder and brushing the hairs will cause a widespread tingling
apparently more intense than any sensation produced by brushing the normal
hair-clad skin.

Yet in every case the protopathic area is one of defective sensibility in
spite of its more vivid response. Stimulation of the normal skin with a needle
produces almost at once the sensation of a pointed object, which with increas-
ing pressure passes gradually into pain. Thus, even if the threshold for painful
stimuli may have sunk approximately to normal over protopathic parts,
they still fail to respond to the antecedent sensation of a point. In the case
of heat and cold, it can be shown that the threshold is always higher than over
the normal skin. Even the tingling evoked by touching the hairs of a proto-
pathic part, requires a stronger stimulus than when the skin is endowed with
epicritic sensibility.

All forms of sensation evoked from protopathic areas have a high thres-
hold, whether the condition be normal as in the case of the penis, or a stage
in the recovery of sensibility after nerve division.

The most striking feature of the response from protopathic parts is its

310 STUDIES IN NEUROLOGY

wide extensity. Each strictly local stimulation is followed, not by a localised
sensation, but by an outburst of pain, heat, cold or tingling which may extend
over the greater part of the affected area.

How large a part is played by this wide extent of the sensation, in our
judgment of the relative coldness of a stimulus applied to protopathic parts,
is shoA\ai by the following experiment. After the cold-spots had been marked
out carefully, the protopathic area was stimulated with the flat circular bottom
of a silver tube 1.25 cm. in diameter containing water at 20° C. This produced
a sensation of cold. One active spot within the area covered by the tube Avas
then stimulated with a copper rod 1 mm. in diameter which had been cooled to
the temperature of ice. This caused a sensation, apparently " less intense " than
that from the tube at 20° C, and the result was not altered by changing the
order of the two stimuli. In these observations, H. was unable to recognise
whether the smaller or the larger object was being applied ; in one case when
the tube had been used he said, " That is a good spot," comparing it with the
previous stimulation with the rod only.

Increasing the area of stimulation produced the same effect as increasing
the intensity of the stimulus. H. would have said that the tube at 20° C. was
uniformly " colder " than the rod, had he not recognised that in many cases
the coldness was not greater. Yet, although the resulting sensation was not
more " icy," it was so much more extensive that his natural tendency was to
call the tube a stimulus of greater intensity. This he might have corrected,
had he been able to recognise that a larger area of skin was stimulated by
the tube than by the rod ; since this was impossible over a purely protopathic
area, his only guide to the intensity of the stimulus was the extent of the
sensation evoked.

But it must not be supposed that he was entirely unable to appreciate
a difference in intensity between two stimuli of equal extent applied to a
protopathic area. A tube containing ice will produce a colder sensation than
the same tube containing water at 20° C. applied to the same parts. But, if
once the stimulus is of a temperature low enough to excite the cold-spots to
a full explosion of activity, the extent of the stimulus is of greater importance
than its intensity.

In considering the direction in which the current notion of intensity might
be revised, we must limit the application of the term in its strict sense to
epicritic and to deep sensibility. In protopathic manifestations, there is
undoubtedly a " more-or-lessness," which is of the same nature as that denoted
by the term intensity, though it is liable to be obscured by variations in the
extent of the stimulus.

It would even seem as if sometimes a less cold object applied to a larger
surface will cause a sensation more intensely cold than the stimulation of a
single spot by an iced rod.

Thus, even when we confine ourselves rigidly to the consideration of
actual more-or-less coldness, a more extensive stimulus at a higher temperature

A HUMAN EXPERIMENT IN NERVE DIVISION 311

may produce a definitely colder sensation, apart altogether from the fact that
it radiates over a wider area.

From these facts, it follows that Weber's law or other expressions of exact
quantitative relations between stimulus and sensation must undergo revision.
In the case of the protopathic system, it is clear that there can be no question
of any such exact relation. In the sensations from a protopathic area, there
may exist a more-or-lessness which can be called intensity. But this is of so
indefinite a character, and its relation to the intensity of the stimulus may
be so obscured by differences in the extent of stimulation, that there can be
no question of any such defuiite association between stimulus and sensation,
as those formulated in Weber's law or Fechner's formula. As far as Weber's
law holds good for the temperature sense of the skin, we should expect it to
be the expression of epicritic thermal sensibility. That is to say, it should
be demonstrable, more particularly between 26° C. and 37° C, the highest
pomt of the cold-spots and the lowest to which the heat-spots reacted. Fur-
ther, the discriminative sensibility as revealed by the just-perceptible difference
or the difference threshold should be greater between these limits. It is
remarkable that two of those who have investigated the validity of Weber's
law for the temperature-sense have given figures corresponding closely with
those to be expected on the basis of our view that the law holds true of epi-
critic sensibility only. Lindemann [69] found the discriminative sensibility
to be greatest on the hand between the temperatures of 26° C and 39° C. ;
the just-observable difference within these limits was 1*20° C, Nothnagel
[87] found the most delicate discrimination between 27° C. and 33° C. ; the
just-perceptible difference was slightly larger only up to 39° C. and was also
fair between 27° C. and 14° C. These observations help to support our view as
far as the skin is concerned, Weber's law applies to epicritic sensibility only.

The results at which we have arrived in this chapter may be summed up
as follows : —

(1) Parts in a condition of f>rotopathic sensibihty respond more vividly
than the normal skin to all stimuh capable of evoldng a sensation.

(2) This sensation is usually more intense and always of much greater extent
than over normal parts.

(3) For all effective stimuli, the threshold is high in a protopathic area,
and, in spite of the vivid response, it is obviously one of defective sensibihty.
Epicritic sensibility with its low threshold must be present, before the sensory
complex resembles that from the normal skin.

(4) An effective protopathic stimulus of low intensity, but covering a larger
area, may produce a sensation of greater apparent intensity than a more re-
stricted stimulation of greater strength. Not only is the sensation more
extensive, but at times it may seem to be specifically more intense.

(5) The usual psychological view that an increased sensory reaction corre-
sponds to a lowered threshold must be readjusted. It is true in the strict
sense only of epicritic and deep sensibihty.

CHAPTER X

PUNCTATE SENSIBILITY

Although our observations on the distribution and functions of the cold-
and heat-spots agree substantially with those of previous observers, we differ
from them fundamentally in our views of the nature of punctate sensibiUty.
Blix ([7] and [8]) was the first who examined the skin minutely with stimuli
of small extent, and discovered the heat- and cold-spots. He was followed by
Donaldson [27] and later by von Frey ([32], [33], [34], [35], [36]) with a superb

- • ,

Sfjk •

•

• «

• •• V

•
•

• •

* • • • •

. 1

II.

IV.
Fig. 71.

III.

'~ Photographed from Blix [7].

^ In the original the black dots are red and correspond to the heat-spots. The lighter dots are green

and represent the cold-spots.

I. — An area on the dorsal aspect of the left hand at the base of the middle finger.
' II. — An area on the -mist.

III. — An area on the arm (" Armlange ").
r IV. — An area on the dorsal aspect of the left hand of another observer.

series of observations which greatly extended the original conception of pmictate
sensibility.

In consequence, it became a matter of general beUef that the skin was
endowed with sensitive spots, each of which reacted to a specific stimulus.
Not only were there spots for cold and for heat, but also for pressure and for
pain. To the activity of this mechanism were attributed all the sensory
impulses arising from cutaneous stimulation.

312

A HUMAN EXPERIMENT IN NERVE DIVISION 313

But this minute concentration on the functions of the sldn led to a neglect
of those forms of sensation produced by the coarser stimuli, such as pressure.
Any object, however light or heavy, was thought to be appreciated in con-
sequence of impulses from the " pressure spots," so long as no movement of
muscles or joints occurred. So soon, however, as the weight was supported
by muscular effort, the " muscle-sense " came into action, based on afferent
impulses conducted from the tendons, joints and other subcutaneous structures.

But division of all the nerves to the skin in our experiment showed that
this deep innervation played a greater part in the sum of sensory impulses from
the periphery than had been previously suspected. Much of what is commonly
called " touch " is due to the activity of this afferent mechanism, and not to
stimulation of the cutaneous " pressure-spots " only.

Excessive pressure was also found to produce pain when the cutaneous
nerves were divided, and it is therefore certain that the " pain-spots " of the
skin are not responsible for all painful sensations from the periphery. The
pain of pressure and rending is due to the stimulation of end-organs of the deep
afferent system.

It is therefore obvious that, of the sum of afferent impulses starting from
the periphery, a large number arise from the activity of organs situated else-
where than in the sldn. On tliis side om' observations are accessory to, but
do not trench on, those on von Frey and his fellow -workers. But even when
we confined our attention to the sldn, we found that the sensory spots did not
account for all the afferent impulses of cutaneous origin which reached the
central nervous system. It is therefore obhgatory on us to show in how far
we agree with, or differ from, the conclusions of previous observers with regard
to punctate sensibility.

§ 1. — Heat- and Cold -Spots

The existence of heat- and cold-spots has not been seriously called in
question since they were first described by BHx [7]. They are easily demon-
strable, scattered irregularly over the surface of the body. The cold-spots
preponderate greatly; according to Blix there are from two to four cold-
spots to one heat-spot. It is difficult to compare his results numerically with
our own, because the size of the area chosen for investigation in different parts
of the body evidently varied greatly, and he does not state whether his maps
were drawn strictly to scale. Donaldson [27] marked out six squares of 1 cm.
on the dorsal surface of each hand ; in these six squares he found on the right
fifty-six cold-spots, and on the left fifty -nine. Within the same Hmits the
heat-spots numbered seventeen and thirty-seven (fig. 72).

The area on the back of the affected hand closely investigated by us con-
sisted of twenty-five squares each of 1 cm. Here we found about sixty-eight
cold-spots, and from fourteen to sixteen heat-spots. Some of these were more

314

STUDIES IN NEUROLOGY

constant than others, and a certain number were discovered at every examina-
tion throughout the four years which followed their reappearance (c/. p. 226
and figs, 67 and 68).

'<i (I

IP'

itm

t2R

4H^

._jL

-KV

-vi-

<K^

iLlt

in'

'nr

Fig. 72.

Somewhat enlarged from Donaldson [27].

The black dots indicate cold-spots. The larger ones represent the spots which gave a strong
reaction, the smaller those which gave a weak one. Circles represent the heat-spots.

A. represents the distribution of the temperature-spots over six squares each of 1 cm. on the back
of the left hand. B. represents a similar map of a symmetrical part of the right hand. Thus each
map is 2 cm. broad and 3 cm. in height.

The upper boundary is peripheral, the lower central; the left of the observer corresponds to the
ulnar aspect, the right to the radial.

Similar results were obtained by Sommer (114) ; von Frey gives no maps
of these spots, but from observations made by him on H.'s hand both before
and after the operation, we can state that our results are numerically in
complete accord with those obtained by his methods.

m:j>

Fig. 73.

Photographed from Goldscheider [40], Tafel 1.

In the original the cold-spots on A. are red, whilst the heat-spots on B. are blue.

Each area rei^resents 4 cm. from the back of the hand.

It is obvious that both heat- and cold-spots vastly outnumber those recorded by other observers.

This remarkable harmonj- in the results of most observers is disturbed by
the statements of Goldscheider [40] only. His maps reproduced in fig. 73
differ so greatly from the results of all other workers, that we can only assume
he was not deaUng \\\t\\ punctate sensibility as generally understood.

A HUMAN EXPERIMENT IN NERVE DIVISION 315

These spots respond to stimulation in a strictly specific manner. Thus,
stimulation of the cold-spots with temperatures of 45° C. produces a sensation
of cold. We have been imable to stimulate either the cold- or heat-spots with
the interrupted current, provided all precautions are taken to exclude thermal
stimuli and the effect of suggestion ; in this we are at variance with Bhx, We
diflfer also from Goldscheider [40] in that we have been unaljle to evoke a sensa-
tion of heat or of cold by mechanical irritation of these sj)ots, if the stimulating
object be maintained at a neutral temperature.

Our observations have shown (Chapter IV., p. 261) that the reaction
of these spots is pecuhar and characteristic. When sensibihty to heat and
cold depends on the existence of spots alone, any effective stimulus tends to
produce a more vivid response than from the normal sldn. Not only is the
sensation evoked from a protopathic area of wider extent than normal, but
at times it seems to be actually colder (c/. p. 308). Yet, in spite of this greater
vi\adness, such parts as the affected area on the back of the hand and the
normal penis did not respond to temperatures between 26° C. and 37° C. The
degree of temj)erature necessary to stimulate individual spots varied greatly ;
but no heat- or cold-spots on the back of the affected hand responded to tem-
peratures between these limits. This combination of an abnormally vivid
response to effective stimuU, mth failure to react to temperatures capable of
exciting the normal skin, is a characteristic feature of all parts, where thermal
sensibihty depends on the existence of heat- and cold-spots only.

Moreover, so long as the thermal sensibihty of a part depends entirely on
these spots, it is incapable of that wide range of adaptation which is an inherent
function of the normal skin (c/. p. 308). Soaking the hand in water at 45° C.
does not cause the cold-spots to resjDond to temperatures above 26° C, and
careful cooling does not increase the range of sensitiveness of the heat-spots.
And yet, under such circumstances on the normal hand, adaptation would
occur and the same intermediate temperature would appear at one time cool
and at another warm.

It might be supposed that the vivid response, the high threshold and the
want of adaptation so characteristic of punctate thermal sensibihty on the
affected parts were due to defective regeneration of the mechanism of the heat-
and cold-spots. But the normal glans penis is unable to respond to tempera-
tures between 26° C. and 37° C, not only when the stimulus is punctiform,
but also when the whole organ is immersed in water. But so vivid are the
sensations evoked by effective thermal stimuli, that von Frey calls it the most
sensitive part of the body.

It is therefore certain that the cold- and heat-spots cannot account for all
the thermal sensibility of the normal skin. Some other nervous mechanism
must be present, which endows the skin with the power of reacting to inter-
mediate degrees, and is capable of thermal adaptation.

But when all the cold- and heat-spots have been marked out on the normal
skin, considerable spaces remain between insensitive to punctate thermal

316 STUDIES IN NEUROLOGY

stimuli. These, if sufficiently extensive to be tested with a tube, will be found
to be sensitive to water above 26° C. and below 37° C, especially after the
part has been suitably adapted.

We therefore beheve that the skin is endowed Mith two thermal mechan-
isms, one of which reacts to pmictate stimuH and has a high threshold judged
by the inabiUty to respond to temperatures between 26° C. and 37° C. Its
end-organs are strictly specific and are dotted about irregularly throughout
the skin, in such a way that large spaces may be entirely devoid of heat-spots.

The second mechanism is incapable of reacting to pimctate stimulation,
but responds readily to temperatures above 26° C. and below 37° C, Avhen
appUed over an area of some extent. The nature of this response depends on
the temperature to which the part is adapted. At one moment 30° C. may
seem warm, at another cold, according to whether the sldn has been previously
adapted to cold or to heat respectively.

§ 2.— Pain-Spots

Bhx [8] denied that sensibihty to pain was associated wdth any mechanism
analogous to the heat- and cold-spots. But in consequence of the mdely
extended observations of von Frey on various forms of pmictate sensibihty,
the idea has gradually grown up that pain-spots exist in the skin in every way
comparable to, but more numerous than, the cold- and heat-spots. Thus
Thimberg ([123], p. 651) says: " Erst v. Frey fand dass die Verhaltnisse hier
(for pain) ganz analog denjenigen der anderen Sinnespmikte Uegen."

But no observations by von Frey bear such an interpretation. His great
contribution to the subject of skin -sensibihty was the introduction of measm^e-
able mechanical stimuli, not only for touch but for pain. He selected a large
number of hairs of different sectional area and bending strain, and showed
that as soon as a certain pressure per unit area was exceeded, pain was produced.
This threshold for pain of cutaneous origin differed greatly in various parts of
the body. If a test-hair was chosen which just exceeded this amoimt, it formed
a mmimal pain-stimulus for that particular part of the body. Such a hair
will be found to cause the characteristic pricldng sensation at a few points
only. These are von Frey's " pain-spots " (Schmerzpmikte). But by increas-
ing the strength of the stimuli, i.e. by using hairs of greater bending strain,
many more points can be discovered from which pain can be evoked ; at last,
the number of such points within anj^ square centimetre becomes so great that
it is scarcely possible to map them with accuracy.

Suppose, however, that one or more square centimetres has been examined
exhaustively and that these minimal pam-spots have been marked on the
skin. On subsequent examination, even an horn- or two later, it will be found
that many of the spots no longer respond to the same stimulus ; for instance,
those which had previously reacted to 75 grm./mm.^ may be insensitive to hairs
of less than 150 to 200 grm./mm.^. Moreover, many unmarked places will be

A HUMAN EXPERi:\IENT IN NERVE DIVISION 317

found to respond even to hairs which exert a comparatively low pressure per
unit area. Whatever ultimate view we may take of the nature of pain-spots,
experimental observations on their distribution are much less conclusive than
those on the heat- and cold-spots.

The true nature of cutaneous painful sensibility cannot be settled by
examination of the normal sldn. But the answer is given at once when we turn
to the permanently protopathic area on the back of H.'s hand. Here the skin
responds to temperatures below 26° C. and above 37° C. only, and painless
stimulation of the hairs produces the characteristic diffuse sensation ; pain
extending widely, and referred to remote parts, can be evoked by stimulation
with the stiffer test-hairs. Such an area is usually supposed to be in a low
state of sensibiUty. But on testing with graded haii's, the threshold for pain
is found to be the same as that for the normal sldn. Sometimes, owing to the
greater teclmical ease of the observations, this protopathic area gave a painful
response to hairs of a lower grade than was the case over an equivalent part of
the normal skin. Far from being a region of defective painful sensibihty, the
threshold for cutaneous pain was here as low (1908), and possibly even lower
than normal. This we can affirm, not only from our own observations, but
from a careful examination made by Professor von Frey of that part of H.'s
hand.

But, although fully sensitive to pain, this area is entirely insensitive to the
tactile test-hairs. Pain, instead of developing gradually out of the sensation
of contact with a pointed object, arises mthout warning as soon as the force
exerted by the " pain-hair " exceeds the threshold for the particular spot to
which it is appHed.

Within this protopathic area, in spite of the simpler condition, we find
exactly the same inconstancy of reaction to cutaneous painful stimuU as in the
normal sldn. By using hairs which just exceed the pain-threshold, two or
three spots can be marked out in each centimetre ; these are the minimal
pain-spots of von Frey. Even these are inconstant in reaction, and by using
hairs of greater bending strain, a multitude of further spots can be discovered
within each square.

Thus it would seem, that the pain-spots within any square centimetre are
extremely numerous and possess widely different thresholds. Moreover, they
are inconstant, varying in sensitiveness from time to time.

This variabiUty and inconstancy of reaction they share with the heat- and
cold-spots. Within the twenty-five squares on the back of H.'s hand, lay
sixteen points where at one time or another heat was evoked by pimctate
stimulation ; of these, thirteen were marked out as the site of heat-spots on
ten or more of the eighteen photographic records, that is to say three heat-
spots were so inconstant that they were frequently missed.

But even amongst those spots which could be discovered without diflficulty,
the threshold was by no means the same. Two of them usually reacted to
38° C, but a large proportion did not respond to temperatures below 40° C. ;

318 STUDIES IN NEUROLOGY

in order to be certain that every spot had been fully tested, we always employed
an iron at about 45° C.

When we examine the records of the more numerous cold-spots, the pro-
portion of inconstant ones greatly increases. In fact, the photographs are so
diverse that we have been compelled to confine our attention to those which
are accompanied by an explanatory key recording the constancy of response.
Among the sixty-eight spots, thirteen only are present in all three sets of maps
and photographs.

The small number of the heat-spots and the complete absence of sensibiUty
to heat in the intervening spaces of the protopathic skin made it easy to settle
their number and to record their position. This is more difficult with the cold-
spots and, with the further increase in number shown by the pain-spots, becomes
an impossibiUty. Moreover, it is easy to be certain that no active cold-spots
have escaped, by using a rod at the temperature of melting ice. But, with
the pain-spots, a great increase in the strength of the stimulus leads to such
deformation of the sldn that the stimulus no longer acts in a punctiform
manner.

But in spite of the technical diflficullies in mapping out the pain-spots, they
are evidently closely allied in origin and function to those for heat and cold.
After division of a peripheral nerve, the three sets of organs recover their
functions approximately together, and a part may remain for a long period
sensitive to painful and to the more extreme degrees of thermal stimulation
only. Sometimes, regeneration may stop short at this j)rotoj)athic stage, and
the hairless sldn will then be sensitive exclusively to stimuli capable of exciting
the pain-, heat- and cold-spots. This is not due to defective restoration of
the nerve-mechanism of the spots themselves, for the cutaneous sensibility
of the glans penis depends entirely on the acti\dty of these spots ; it is a part
of the sldn which has remained normally in a protopathic condition.

Moreover, so long as the skin is innervated through these spots only, the
sensation is widely diffused, and referred into some remote part w-hich is con-
stant whatever stimulus be applied, provided the area stimulated is the same.

Thus, it is obvious that the cutaneous mechanism wiiich underlies painful
sensibility belongs to the same order as the heat- and cold-spots, both in the
period at which it regenerates and in the nature of its response to stimulation.

The heat- and cold-spots form a thermal mechanism with a high sensory
threshold, incapable of responding to temperatures betw^een 26° C. and 37° C.
But a cutaneous painful sensation can be evoked from a liighly developed
protopathic part as easily, and in some cases even more easily, than from the
normal sldn. It would seem at first sight as if protopathic sensibiUty was not
in this case associated with a high threshold.

But careful analj^sis of the effect produced by stimulation with graduated
hairs shows that, although pain is produced as easily over highly protopathic
parts as over the normal sldn, the complex of sensations is different. When
a hair of betw^een 70 and 100 grm./mm.- is appUed to the protopathic area, a

A HUMAN EXPERIMENT IN NERVE DIVISION 319

sensation of localised pressure is produced, followed by the gradual develop-
ment of the characteristic stinging pain. Over the normal skin, the first
sensation, when the hair is appUed, is one of a circumscribed pointed object ;
to this, a definite pamful element is gradually added. At pressures incapable
of producing pain, the sensation of a point warns the patient that the stimulus,
if increased in strength, may become painful. This recognition of the pointed
nature of the stimulus is due to the power of appreciating relative size, a faculty
which depends on impulses arising in the epicritic mechanism. •

Pain is always a high threshold sensation as shown by the fact that it is
not evoked by punctiform stimuli until the pressure exceeds 70 grm./mm.^.
The low threshold contribution to the sensory complex, introduced by the
existence of epicritic sensibility, consists in the power of recognising that the
stimulus is pointed, before the pressure is sufificient to cause pain.

In conclusion, we beUeve that the sensibiUty of the sldn to painful stimulation
depends upon organs analogous to the heat- and cold-spots ; and just as the
latter are more numerous than the former, so the pain-spots exceed the cold-
spots in number. With this excess is associated a A\ide diversity of threshold
and a greater inconstancy of response, so that it is experimentally impossible
to mark out with certainty all the pain-spots in a given area. Von Frey's
pain-spots comprise those of the lowest threshold only, which react to the
minimal punctate pain-stimulus for any particular area of the skin.

The pain-spots resemble those for heat and cold in that the threshold of
even the most sensitive is remarkably high. Stimulation of the skin with
graduated hairs produces a mdely diffused sensation of pain, wdth no ante-
cedent appreciation of the pointed nature of the stimulus. This faculty first
returns wdth the restoration of the low threshold impulses of the epicritic
system.

§ 3.— Touch-Spots

So far we have considered the reaction to punctate stimuli of three sets
of end-organs, which recover their function early within approximately the
same period after nerve division. A portion of the skin, innervated by these
organs only, shows sensory pecuUarities which we have called protopathic and
is entirely insensitive to cutaneous tactile stimuU, provided the hairs are not
disturbed.

But it is universally recognised that on the normal sldn, punctate stimuli
produce a sensation of touch. Blix described what he called " Druckpunkte,"
points in the skin pecuharly sensitive to touch, in close relation to the roots
of the hairs. These observations were amphfied by von Frey, who found that
these " Druckpunkte " possessed a remarkably low threshold. He was, how-
ever, unaware of the phenomena of deep sensibiHty and did not recognise that
comparatively slight pressure could produce a localised sensation, although the
sldn was entirely insensitive. This name is therefore unfortunate, and we shall

320 STUDIES IN NEUROLOGY

speak of " touch-spots," whenever we allude to these sensitive cutaneous
points (" Druckpunkte ").

These spots belong to a different order from those of pain, heat and cold.
They regain their function at a much later period of regeneration, if the nerve
has been completely divided. Thus the proximal patch on H.'s forearm became
sensitive to prick 56 days after the operation ; sensibihty to cold returned in
112 days, and in 161 days this part responded to heat. But it was not until
366 days after the operation, that the same area when shaved became sensitive
to cutaneous tactile stimuli.

Should any part of the sldn happen to remain permanently in a protopathic
condition, it will show all the properties of punctate sensibility to pain, to heat
and to cold, but will be devoid of touch-spots. This is the normal condition
of the glans penis.

Conversely, the skin of the " triangle " was sensitive to cutaneous tactile
stimuli and was endowed with touch-spots resembhng in function those of the
normal skin. But no pain-, heat- or cold-spots could be found anywhere
within this area.

We have already described the close association between the returning
response to cutaneous tactile stimuli and the recovery of sensibihty to inter-
mediate degrees of temperature, more particularly to warmth. Thus, a part
such as the back of the hand may remain for a long while innervated by pain-,
heat- and cold-spots only, insensitive to temjjeratures between 26° C. and
37° C. and to painless stimulation with von Frey's test-hairs. As soon, how-
ever, as the touch-spots reappear, the part will be found to have regained in
addition its sensibihty to intermediate degrees of temperature.

Moreover, the return of fmiction to the touch-spots is closely associated
with recovery of the power of accurately locahsing cutaneous tactile stimuU.
Before this group of sensory functions has reappeared, discrimination of two
points apphed simultaneously is impossible. But with the recovery of sen-
sibihty to von Frey's tactile hairs, accurate localisation and discrimination
become possible. The wide radiation and reference into remote parts, so char-
acteristic of the unchecked activity of heat-, cold- and pain-spots, ceases and
is replaced by a less Advid sensation, restricted to the immediate neighbourhood
of the point of contact. Thus, the return of function to that sensory mechan-
ism of which the touch-spots form a component, actuaUy diminishes the sensa-
tions associated with the activity of those organs, which are universally accepted
as the type of cutaneous sensory spots.

Over hair-clad parts, these touch-spots are strictly associated with the
roots of the hairs ; they express the sensibihty to mechanical stimuh of that
part of the hair which lies beneath the surface of the skin. Almost every hair
is a delicate tactile sense-organ ; any movement of its tip is transmitted to its
root with the increased power of a lever, setting up tactile impulses. It is not
remarkable, therefore, that mechanical stimulation, apphed directly to the
hair-root, produces similar tactile sensations. But owing to the want of

A HUMAN EXPERIMENT IN NERVE DIVISION 321

leverage, this method of stimulation is less effective, and the force required to
produce a sensation is higher than when the free portion of the hair is disturbed.

Even when care is taken to touch no part of a hair lying above the
sldn, the threshold for punctate tactile sensibility is extremely low. Out
of 303 touch-spots on von Frey's forearm, 221 reacted to a force of or below
1 grm./mm. (8 grm./mm.^) ; sixty-six required 2 grm./mm. (12 grm./mm.-), and
there was not one which did not respond to 4 grm./mm. (21 grm./mm. 2).
Such threshold values are roughly one-fourth of those required over the same
parts to produce a painful sensation.

But it must not be supposed that these touch-spots are the same as those
for pain. The majority of the pain-spots lie between hairs, whilst on hair-clad
parts touch-spots correspond almost exclusively to hair-roots. It must not be
forgotten that a hair-root may be found to be the seat of both a touch- and
pain-spot owing to the sensibiUty of many of the hairs, both to tactile and
to painful stimuli. But, whereas the spaces between the hairs contain many
pain-spots, touch-spots are almost entirely absent. Von Frey discovered three
touch-spots only which were not definitely associated wdth the hair-roots, in
a space of seven 1 cm. squares on the calf of the leg. Within the same area he
marked out seventy-seven touch-spots connected with the hairs ([36], p. 233).

Almost all the observations on touch-spots have been made on hair-clad
parts of the sldn ; here, as von Frey has shown, they correspond to the sub-
cutaneous portions of a hair. But the tips of the fingers are even more sensitive
to the test-hairs than any hair-clad part. Thus the finger responds to
3 grm./mm. 2, but the back of the hand requires 12 grm./mm. 2. Here the
existence of definite touch-spots cannot be demonstrated with certainty, so
numerous are the points sensitive to stimulation with test-hairs.

We have shown that when any part of the skin, whether endowed \vith hairs
or not, becomes sensitive to punctate tactile stimuli, it shortly regains its
sensibility to temperatures between 26° C. and 37° C. Yet the heat-spots are
not increased in number and do not react to thermal stimuli below 37° C.
This return of function must be due to some mechanism of a different order
from the heat-spots.

In the same way, we believe that the return of cutaneous tactile sensibiUty
is coincident with the restoration of function to a set of end-organs of a different
order from the heat- and cold-spots. On hairless parts of the skin, such as the
finger-tips, they are so thickly scattered that it is impossible to demonstrate
their punctate distribution. But over hair-clad parts they are associated
pecuHarly with the hairs, and every hair root therefore becomes a sensory spot.

The conclusions arrived at in this chapter can be summed up as
follows : —

(1) The skin is supplied by two anatomically distinct systems which have

been called protopathic and epicritic, and regenerate at different periods after

complete nerve division. Moreover, a part of the sldn may be supphed by one

of these systems only. Thus, the cutaneous sensibiUty of the normal glans

vol.. T. V

322 STUDIES IN NEUROLOGY

penis is protoi3athic, closely resembling the present condition of a small portion
of the affected area on the back of H/s hand. Conversely, the " triangle "
was sensitive to tactile test-hairs and to warmth, but was completely devoid
of heat-, cold- and pain spots.

(2) Protopathic sensibiUty depends upon specific end-organs gathered
together within the skin to form sensory spots ; the spaces between are in-
sensitive to cutaneous stimuh, if the part is endowed with protopathic sensi-
bility only.

Owing to the sparseness of the heat-spots, their characteristics can be easily
demonstrated; cold-spots are more numerous and correspondingly difficult
to investigate. The pain-spots are so closely distributed thi-oughout the skin
that it is impossible to study them with the accuracy of the heat- and cold-
spots ; but the character of their response, and the period at which they
regenerate, show that they belong to the same order.

(3) Whenever the skin is supphed by protopathic end-organs only, any
sensation evoked radiates widely and tends to be referred to remote parts.
These are the same, whichever kind of spot be stimulated, so long as it Ues
witliin the same area of the sldn.

Radiation and reference are abolished, as soon as the part becomes sensitive
to cutaneous tactile stimuh and to intermediate degrees of temperature.

(4) Any part of the skin, innervated by heat- and cold-spots only, is in-
capable of that wide adaptation to external temperatures so characteristic
a function of the normal skin.

(5) Cutaneous tactile sensibility is due to the activity of a sensory mechan-
ism of a different order from the heat-, cold-, and pain-spots. It regenerates
much later after complete nerve-division. The restoration of cutaneous
tactile sensibihty is closely associated with the return of the capacity to apj)re-
ciate temperatures between 26° C. and 37° C, with the pow'er of accurate
cutaneous localisation and with the discrimination of two points.

Its end-organs become susceptible of investigation with punctate stimuli
over hair-clad parts, owing to their close association with the roots of the hairs.
But these " touch-spots " (Druckpunkte of BHx and von Frey) are not analo-
gous to those for heat, cold, and pain.

(6) All protopathic sense-organs have a high threshold ; the heat-spots
do not react to temperatures below 37° C, the cold-sjDots do not respond to
temperatures above 26° C. and the pain-spots on the back of the hand are
insensitive to pressures below- about 70 grm./mm.^

All epicritic sense-organs have a low^ threshold. They respond to tem-
peratures betw^een 26° C. and 38° C, and the back of the hand is sensitive to
12 grm./mm.^.

A protopathic part, whether it be the normal glans penis, or the affected
part of H.'s left hand, is in a condition of high threshold sensibiUty. When
the normal skin is stimulated, the defects of protopathic sensibihty are corrected
and compensated by the simultaneous activity of the low threshold epicritic

A HUMAN EXPERIMENT IN NERVE DIVISION 323

system. Temperatures between 26° C. and 37° C. can produce sensory im-
pulses, and the epicritic mechanism is highly adaptable. The threshold for
painful sensations is the same over normal and over highly protopathic parts,
but on the normal sldn the approach of pain is preceded by the sensation of
contact with a pointed object. This is absent over protopathic parts. The
130wer of recognising the pointed nature of the stimulating object depends on the
existence of epicritic sensibility, and belongs to that group of sensations by
which we estimate relative size.

VOL. r. Y 2

CHAPTER XI

general theoretical conclusions

§ 1. — The Integration of Afferent Impulses

Throughout this paper we have spoken of three forms of sensibility, and
in the previous chapter we gave our reasons for the belief, that they were
associated with the activity of three anatomically distinct systems.

Johannes Miiller believed that on stimulating the body-wall a specific
impulse was initiated, which passed unaltered to the brain, forming the basis
of a specific sensation. In the same way Blix [7], when he discovered the
heat- and cold-spots, thought that the impulses arising in these specific organs
passed unchanged through the nervous system to underUe all sensations of heat
and cold.

But we have been able to show that the process is one of much greater
complexity. Under normal conditions there are no " protopathic " or
" epicritic sensations." These terms may be justly applied to two anatomically
distinct peripheral systems, or to the sensibihty with which the skin becomes
endowed by the preponderating activity of one or other nervous mechanism.
They can also be used to distinguish two groups of impulses set free by stimula-
tion of the end-organs in the skin. But sensations must be described solely
by their specific quahties, and not by these names which apply to the peripheral
physiological level only.

For, as soon as they reach the first junction in the central nervous system,
sensory impulses are transformed into more directly specific groups. Both
protopathic and epicritic end-organs may be stimulated by heat appHed to the
skin and the resulting impulses will travel by separate peripheral paths to the
spinal cord. There they become united and pass on, as a single isolated group,
to underhe, in the highest centres, specific sensations of heat.

A similar fusion of originally separable elements occui's when the sldn is
stimulated with cold, and the intramedullary path transmits an equally specific
group of impulses.

In the same way, the physiological basis of a sensation of j^ain may be
compounded of elements due to stimulation of the end-organs of the sldn and
of the deep afferent system. These, when united, pass up together in the same
isolated paths devoted to the transmission of sensory impulses evoked by painful
stimuli.

Epicritic tactile impulses become combined with those arriving by way

324

A HUMAN EXPERIMENT IN NERVE DIVISION 325

of the deep afferent system into a single tactile group. Once past the first
synaptic junction, ei^icritic impulses, evoked by the lightest perceptible touches,
become simply the minimal physiological elements in a tactile group, of which
the maximal constituents, produced by pressure, arrive by way of the deep
afferent system.

But pressure acting on the end-organs of this deep system may cause sensa-
tions of pain in addition to those of touch. Under such circumstances, the
tactile imj^ulses evoked by jDressm-e will arrive at the spinal cord in company
with those Avhich underUe pain. On reaching the first synaptic junction,
these two elements become separated. The tactile impulses are combined
with those arriving b^^ way of the epicritic system ; whilst those associated with
the painful asj^ect of pressure pass into a secondary path, in conjunction
with impulses arising from stimulation of the pain-spots in the sldn. When
once the secondary afferent system has been reached, no traces remain of the
original grouping in the peripheral path.

This integration takes place on a physiological level ; the whole process
remains entirely outside consciousness. Throughout their passage from the
periphery to the highest centres, these impulses undergo redistribution from
the complex elementary grouping to something simple and specific.

The process, so far as we have yet considered it, has been one of sorting
only. Impulses, originated by similar aspects of the same stimulus, have
been gathered together, although they arose in end-organs of different systems.
When, however, we consider that a temperature of 45° C, applied to the normal
sldn, can be shown to stimulate the heat-spots, the cold-spots and the epicritic
thermal mechanism, it is obvious that some of these peripheral impulses must
be inhibited; they never reach the highest centres to form the basis of a
sensation. It might be objected that under normal circumstances the cold-
spots are not stimulated by a temperature of 45° C. ; but, provided the heat
is applied directly to a cold-spot, paradox-cold is easily evoked from the normal
skin. As soon, however, as a heat-spot is stimulated at the same time, the
cold sensation disappears, giving place to one of heat. Evidently, the impulses
produced by the action of 45° C. on the heat-spots and epicritic thermal mechan-
ism are dominant to those evoked from the cold-spots. During the protopathic
stage of recovery, it was possible to find parts where the thermal mechanism
consisted of cold-spots only. Here even tubes containing water at 45° C.
caused a sensation of cold.

The behaviour of the penis forms an excellent example of such inhibition.
In the case of H., the tip happens to be devoid of heat-spots but is sensitive
to cold and to pain. When, therefore, it was dipped into water at 40° C, no
sensation of heat was produced, but H. experienced an unusually disagreeable
sensation of pain. When the water was raised to 45° C, this was to a great
extent displaced by a vivid sensation of cold. But, as soon as the water
covered the corona without reaching the foresldn, both cold and pain dis-
appeared, giving place to an exquisitely pleasant sensation of heat. The

326 STUDIES IN NEUROLOGY

corona is richly endowed with all forms of protopatliic sensibihty; but the
imiDulses, which must have been evoked from the end-organs for pain and for
cold by contact ^vith. the water at 45° C, were inhibited by those consequent
on stimulation of the heat-spots. Moreover, we can estimate the relative
dominance of the impulses evoked by any particular temperatm^e. At 45° C.
those which form the basis of sensations of pain are controlled by those evoked
from stimulation of the cold-spots, and both recede before the impulses which
miderlie a sensation of heat. But a further rise in the temperatm-e of the
stimulus to about 50° C. causes a sensation of pain together with one of heat,
and the only inliibited impulses are those from the cold-spots.

The following experiment on H.'s hand shows this inliibition in a still more
remarkable manner. A portion of the affected area in the neighbourhood of
the index knuckle remains in a purely protopatliic condition, and adequate
stimulation of the skin still causes a ^dvid sensation of cold referred to the
dorsal aspect of the thumb. If this part of the thumb was brought into contact
^\ith a large vessel containing water at between 40° C. and 44° C, H. experienced
a pleasurable sensation of heat . A cold tube was then appUed to the neighbour-
hood of the index kiruckle, and the impulses which would normally have evoked
a sensation of cold in the thumb were neutralised by contact of this part of the
skin A\ith the warm vessel. All sensations of heat at once disappeared from
this portion of the thumb, and gave way to a new sensation, that of pain. As
we know from experiments on the penis, temperatures of from 40° C. to 44° C.
can evoke pain in the absence of the thermal mechanism. Evidently, there-
fore, the warm vessel stimulated the pain-spots in the thumb, but the impulses
so caused were inhibited by those which underlay the sensation of heat. When
these impulses were neutralised by the application of cold to the region of the
index knuclde, those evoked from the pain-spots were no longer blocked, but
passed onwards to form the basis of a painful sensation.

Throughout the fii'st or protopatliic stage of recovery in our experiment,
the vividness and extent of the reaction became greater mth the gradual
retiu-n of sensibility to pain and the increasing number of heat- and cold-spots.
This tendency to evoke a sensation, in parts remote from the point of stimula-
tion, was curtailed or even aboHshed, at the height of its development, with
the first signs of returning sensibihty to cutaneous touch and to minor degrees
of heat. Had the recovery of sensation taken place by gradual increments,
we should have expected the steady increase in protopathic sensibihty to be
associated with, a simultaneous decrease in radiation and reference. But in
no part of the afifected area was this form of sensibihty so high and references
so vi\dd as in the patch on the back of the hand, which still shows no signs
of epicritic recavery (autumn of 1908). The return of epicritic imjiulses
diminishes protopathic activity, as expressed in the sensations evoked by
stimulation of the end-organs of this system.

This is proved by the behaviour of the recovering hand after it had been
cooled. Epicritic sensibihty is hable to be affected by external cold, especially

A HUMAN EXPERIMENT IN NERVE DIVISION 327

before it has been completely restored. At a time when almost the whole of
the back of H.'s hand had so far recovered that referred sensations could no
longer be produced, it was rapidlj'^ cooled ; it thereupon ceased to respond to
cotton Avool when shaved. Radiation and reference returned as vividly as of
old, and the hand was thrown back into a purely protopathic condition. The
newly recovered activity of the deUcate epicritic mechanism was disturbed
by the cold, and protopathic impulses previously inliibited now passed through
uncontrolled.

This control can be exerted even by epicritic imjDulses from the adjacent
normal sldn. If a cold tube was placed so that it fell wholly mtliin that part
of the affected hand which remains in a protopathic condition, a vivid referred
sensation was always experienced in the thumb. But when the base of the
tube fell partly within the abnormal area and partly on the neighbouring skin,
reference was abohshed; the only sensation produced was one of coldness
around the spot on the back of the hand in contact with the tube.

The first stage of recovery after complete division of all the peripheral
nerves to any part of the skin is occupied in the restoration of protopathic
sensibiUty. Throughout this period, protopathic impulses are not inliibited ;
owing to the absence of the epicritic system and the sensations of pain, heat
and cold are not only more vivid, but are referred into remote parts. But
none of these phenomena accompanied the return of sensibihty to the heat-,
cold- and pain-spots witliin the " triangle." This area on the back of the
wrist was from the first sensitive to cutaneous tactile stimuH, and two points
apj)Ued simultaneously within it could be discriminated ; but we were unable
to discover any signs of punctate sensibihty to pain, heat or cold. Gradually
these spots reappeared ; but the sensations evoked when they were stimulated
were no more vivid or extensive than normal. The existence of epicritic sensi-
bihty throughout the period of protopathic regeneration controlled the aberrant
manifestations of this system.

§ 2. — Sensory and Non-Sensory Afferent Impulses

Some afferent impulses never reach consciousness at all, but carry out their
functions reflexly on the physiological level. To this group belong those which
influence muscular tone, and control the condition of the vessels.

But many impulses capable of forming the basis of a sensation are pre-
vented under normal conditions from reaching the highest centres ; or, if
their forward path is not completely barred, they pass on in a profoundly
modified form, in consequence of the concuiTent activity of other sensory end-
organs. The utihty of this arrangement is obvious, especially in the case of
those impulses which underhe sensations of pain. Temperatures of from
40° C. to 45° C. normally cause a pleasurable sensation of heat, although, in
the absence of the heat-spots and epicritic thermal mechanism, pain is produced.
Such temperatures suffice to stimulate to the pain-spots, at any rate on the

328 STUDIES IN NEUROLOGY

back of the hand, but the impulses evoked are prevented from reaching the
highest centres by the effects of coincident stimulation of the thermal end-
organs. As the temperatures rise, these potentially painful impulses increase
in strength, until they can no longer be inhibited; they then form the basis
of a sensation of pain. In this case, consciousness is not disturbed, until
impulses are produced, not only in themselves of adequate strength to evoke
a sensation, but able to overcome the inhibitory effect of the activity of other
specific end-organs.

In a similar way, the return of epicritic sensibility reduces the amount
of pain caused by cutaneous stimuH, without at the same time raising the
threshold. Radiation and reference are inliibited, and the pain produced by
a prick is restricted to the immediate neighbourhood of the spot stimulated.
This diminution in extent reduces the amount of pain suffered by the patient,
although the measured threshold for painful sensations may be actually lower
than during the preceding protopathic stage.

So long as a part of the body is innervated by the end-organs of the deep
and protopathic systems, two incompatible forms of locahsation are possible.
Painless pressure will be locaUsed in the neighbourhood of the spot to which
it is apphed ; but the sensation evoked by purely cutaneous stimuU ^vill radiate
widely, and be referred into some remote part. Both forms of localisation
may be present in consciousness together. When a cold test-tube is apphed
to the permanently protopatliic area on the back of H.'s hand, the pressure
of the tube is locahsed in the neighbourhood of the point of contact, but the
cold sensation is said to lie mainly in the thumb. Thus, the existence of
comparatively accurate tactile locahsation, due to the deep afferent system,
does not seem to inhibit or control the impulses produced by stimulation of
protopathic end-organs. But, when once a part of the body is endowed with
epicritic sensibihty, reference ceases entirely.

It has been suggested (von Frey [39]) that protopathic sensibihty is due
to anatomical changes which have taken place within the central nervous
system, in consequence of the abnormal state of the injured nerve. On the
other hand, we beheve that this condition is due to the uncontrolled passage
of a set of impulses, wliich normally undergo modification or inhibition before
they reach the liighest centres. This view is supported by the existence of a
normal protopathic siuface, such as that of the glans penis.

Most of the characteristic reactions obtained from a part in a condition of
protopathic sensibihty undergo modification with the return of epicritic im-
pulses; reference alone is completely abohshed. It may be asked why a
function apparently so useless remains, though in a condition of permanent
suppression. The answer to this question is given by the existence of referred
pain in disease of the internal organs. These parts are probably innervated,
hke the glans penis, from the deep and protopathic systems. But, unhke
the glans, their sensibihty is extremely low; heat- and cold-spots must be
scanty or even absent from most parts of the stomach and intestines. More-

A HUMAN EXPERIMENT IN NERVE DIVISION 329

over, pain cannot be produced by such stimuli as the prick of a pin, sufficient
to evoke sensations from protopathic parts on the surface of the body. Inter-
nal surfaces cannot respond to artificial stimuli, to which they have never
been exposed during the hfe of the individual or the race.

Even if a stimulus is able to evoke impulses from these sheltered parts
of defective sensibility, it does not usually produce a sensation, in con-
sequence of the concurrent activity of the sensory organs of the skin. But a
sensation may be produced, whenever these visceral impulses become sufficiently
strong to overcome this inhibition, or when the central resistance to their
passage is in any way lessened. Once the path has been opened, the resistance
to potentially painful impulses is lowered, and a weaker visceral stimulus will
evoke a sensation. To this diminished resistance is probably due the pro-
duction of pain by otherwise inadequate stimuli in cases of long-continued
visceral irritation.

Since the internal organs are totally devoid of epicritic sensibiUty, a sen-
sation jDroduced within the visceral area will tend to show the same peculiari-
ties as one evoked from a part supplied with deep and protopatliic sensibility
only. If the stimulus consists of pressure or of the movement of muscles,
the patient will recognise to some extent its true locality, in proportion as the
part is supplied with end-organs from the deep afferent system. When,
however, the stimulus evokes pain the sensation will tend to be referred into
remote parts.

Now, just as one part of the affected area on H.'s hand seemed to be linked
with some other remote portion, so visceral sensory surfaces seem to be closely
associated with somatic segmental areas. When pain is evoked, it is not
localised in the organ stimulated, but is referred to some area on the surface
of the body.

Thus, the retention, on the primary level, of afferent impulses, which if
not inhibited, would lead to incorrect localisation, has a protective object.
To the normal organism they would be worse than useless, but in disease they
underlie widespread pain and uncontrollable muscular reflexes.

The sensory processes discussed in this chapter take place on the physio-
logical level. Psychological analysis fails entirely to disclose the struggle of
sensory impulses revealed by our experiment. Integration occurs as impulses
pass from the periphery towards the higher centres ; the change is a constant
one from a complex to a simpler and more specific grouping. Sensation, the
final end of the process, assumes forms simpler than any sensory impulses.

We believe that the essential elements exposed by our analysis owe their
origin to the developmental history of the nervous system. They reveal
the means by which an imj^erfect organism has struggled towards improved
functions and psychical unity.

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