MONOGRAPHS ON EXPERIMENTAL BIOLOGY 
LABYRINTH AND 
EQUILIBRIUM 
BY 
SAMUEL STEEN MAXWELL,' M.S., Ph.D. 
PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OF CALIFORNIA 
ILLUSTRATED 
PHILADELPHIA AND LONDON 
J. B. LIPPINCOTT COMPANY COPYRIGHT, 1923, BY J. B. LIPPINCOTT COMPANY 
PRINTED BY J. B. LIPPINCOTT COMPANY 
AT THE WASHINGTON SQUARE PRESS 
PHILADELPHIA, U. S. A. EDITORS’ ANNOUNCEMENT 
The rapid increase of specialization makes it im- 
possible for one author to cover satisfactorily the whole 
field of modern Biology. This situation, which exists in 
all the sciences, has induced English authors to issue 
series of monographs in Biochemistry, Physiology, and 
Physics. A number of American biologists have decided 
to provide the .same opportunity for the study of 
Experimental Biology. 
Biology, which not long ago was purely descriptive 
and speculative, has begun to adopt the methods of the 
exact sciences, recognizing that for permanent progress 
not only experiments are required but quantitative ex- 
periments. It will be the purpose of this series of mono- 
graphs to emphasize and further as much as possible this 
development of Biology. 
Experimental Biology and General Physiology are one 
and the same science, in method as well as content, since 
both aim at explaining life from the physico-chemical 
constitution of living matter. The series of monographs 
on Experimental Biology will therefore include the field 
of traditional General Physiology. 
Jacques Loeb, 
T. H. Morgan, 
W. J. V. OSTERHOUT. PREFACE 
It has been the aim in this little volume to present an 
objective study of the equilibrial reactions of vertebrate 
animals and the mechanism through which these reactions 
are produced. Discussions of the possible subjective 
sensations in connection with labyrinthine excitation, and 
of clinical applications of the facts are both outside the 
scope of the book. 
The ears of fishes have proved to be in many ways the 
most favorable objects for these investigations. My own 
experiments on the functions of the different portions of 
the labyrinth, especially of the otoliths, were possible only 
because of the large size and the accessibility of the struc- 
tures concerned. For these reasons the following pages 
are devoted largely to the description of the experiments 
on the ears of selachians and the statement of conclusions 
which may be reached from these experiments. No safe 
inferences can be drawn, however, without consideration 
of the results in all classes of vertebrates. It was the 
original intention to add a chapter on the effect of re- 
peated rotations, but the interesting work of Griffith indi- 
cates that such a discussion would be premature. For a 
similar reason the developmental studies of Streeter have 
not been included. 
The writer avails himself of this opportunity to ex- 
press his life-long obligation for both encouragement and 
inspiration to his teacher and friend, Professor Jacques 
7 8 
PREFACE 
Loeb. Thanks are also due to Professor T. C. Burnett, 
who has kindly read the manuscript, and to Professor 
E. P. Lewis, whose critical judgment was secured on the 
physical principles contained in Chapter VIII. Mr. A. M. 
Hillman gave valuable assistance in the reading of 
the proof. 
S. S. M. 
The Spreckles Physiological Laboratory of 
the University of California, Berkeley. 
January, 1923. CONTENTS 
CHAPTER PAGE 
I. Introduction 13 
II. Compensatory Motions and Compensatory Positions 17 
III. Forced Positions and Forced Movements 25 
IV. The Labyrinth as a Whole 32 
1. The Effects of Destruction of One Labyrinth 32 
2. The Effects of Destruction of Both Labyrinths 42 
V. Reactions of Non-Labyrinthine Origin 48 
1. Contact Reactions 49 
2. Reactions to Retinal Stimuli 57 
3. Reflexes from Muscles and Joints 61 
VI. Experiments on the Semicircular Canals 65 
1. Stimulation Experiments 66 
2. Extirpation of the Ampullae 73 
VII. Experiments on the Otoliths 82 
1. Extirpation of the Otoliths 84 
2. Stimulation Experiments on the Otolith-Organ 92 
VIII. The Mechanism of the Dynamic Functions of the Labyrinth 99 
1. The Dynamic Functions of the Ampullae 99 
2. The Dynamic Functions of the Otolith-Organ 116 
IX. The Mechanism of the Static Functions of the Labyrinth. . 121 
1. The Static Functions of the Otolith 122 
2. The Static Function of the Ampullae 124 
X. The Tonus Effects of the Cristae and of the Maculae 127 
XI. Nystagmus 136 
Literature 146 
9 ILLUSTRATIONS 
PAGE 
1. Diagrams of Compensatory Positions of Eyes of Dogfish 22 
2. Diagram of Dorsal View of Rhinobatus Productus 40 
3. Tracing of Eye Movement of Rhinobatus in Response to Contract 
Stimuli 42 
4. Generalized Diagram of Membranous Labyrinth of a Selachian.... 68 
5. Wheel Diagram 102 
6. Wheel Diagram 102 
7. Compensatory Position of Frogs Photographed While Rotating to 
Left 106 
8. Diagram to Illustrate Relation of Vestibular Structures to Ampulla 113 
9. Block Diagram 119 
10. Diagram to Illustrate the Principle of Caloric Stimulation 144 
11. Diagram to Explain Effect of Change of Position on the Head on the 
Result of Caloric Stimulation 145 
11 LABYRINTH AND 
EQUILIBRIUM 
CHAPTER I 
INTRODUCTION 
Most vertebrate and many invertebrate animals tend 
to maintain a definite orientation with reference to the 
lines of gravitational force, or, in everyday language, to 
keep right side up. If an animal is pushed out of its 
normal position, changes occur in the tension of the 
muscles of the limbs or other organs of locomotion in 
such a way that the original position is automatically 
regained. When a live fish is rotated around its longi- 
tudinal body axis so that the back is turned to the right 
and the belly to the left, the fins on the right side are at 
once moved ventrally and those on the left side dorsally. 
These reflex movements are exactly adapted to restore 
the body to its normal position of symmetry with refer- 
ence to the lines of the earth’s attraction. To these 
movements Breuer gave the name compensatory, and to 
the reaction as a whole Loeb very appropriately has 
applied the term geotropism. 
When the animal is rotated in a horizontal plane, that 
is, around a vertical axis, compensatory movements also 
occur, although in this case no new relation has been as- 
sumed with reference to the lines of gravitation and the 
13 14 
LABYRINTH AND EQUILIBRIUM 
reaction is not geotropic. For convenience we shall con- 
sider these, together with the geotropic reactions, as 
reactions of equilibrium. 
In vertebrate animals the excitations which bring 
about the reactions of equilibrium arise mainly in the 
end organs of the eighth nerve, for they may disappear 
or be profoundly modified when both of the eighth nerves 
are cut or when both labyrinths are completely de- 
stroyed. But very similar compensatory movements oc- 
cur in animals which do not naturally possess a labyrinth, 
and they also appear in vertebrates in which both laby- 
rinths have been extirpated. 
Compensatory movements can be called forth by mov- 
ing retinal images, and righting reactions can result from 
contact stimuli. Also two or more sets of influences may 
combine to produce the observed effect. Loeb has shown, 
for example, that in the horned lizard, Phrynosoma, com- 
pensatory movements of the head may be produced 
through excitations arising in the retina without the par- 
ticipation of the labyrinth, and also through excitations 
of the endings in the ears when the eyes are closed. When 
Phrynosoma is rotated with the eyes open, the retinal and 
labyrinthine stimuli reenforce each other during the rota- 
tion, but their after effects are in opposite directions. 
The righting reactions of vertebrates are often as- 
sumed to be dependent on the labyrinth. A dogfish in 
which both labyrinths have been destroyed swims with 
no definite orientation while near the surface, but rights 
itself promptly if it happens to touch the bottom; hence 
it will not do to assume that in the normal animal the 
righting reaction is always due to the internal ear. 3 INTRODUCTION 
15 
The facts just mentioned show that it is necessary to 
discriminate carefully between those compensatory move- 
ments which do and those which do not arise from excita- 
tions in the ear. It is important also to determine what 
part is played by each, where two or more act simul- 
taneously. Contact stimuli, in particular, play so large 
a role that it has seemed desirable to devote a separate 
chapter to the consideration of reactions of non-laby- 
rinthine origin. 
It will be convenient to distinguish, as did Mach and 
Breuer, between two kinds of equilibrial functions; the 
one, dynamic, in response to movements of rotation, and 
the other, static, by which is produced a definite orienta- 
tion with reference to the lines of gravitational force. 
We may further recognize the possibility of investigating 
these functions either through the study of their objective 
signs in the form of compensatory motions and compen- 
satory positions, or through their subjective manifesta- 
tions as sensations. 
It is self-evident that the subjective method can be 
used only in man, where operative procedures to deter- 
mine which functions are lost and which persist after the 
destruction of certain parts are, of course, out of the 
question. Moreover the subjective method introduces the 
difficulty, at times apparently insuperable, of distinguish- 
ing between feelings which may properly be termed sen- 
sations and the more complicated psychic processes of 
the nature of judgments. There is, too, the obvious dan- 
ger that a movement may be interpreted as the effect of 
a sensation, whereas the sensation may have been the 
result of the movement, or the two things, sensation and 16 
LABYRINTH AND EQUILIBRIUM 
movement, may have been simultaneous effects of a 
common cause. 
For the reasons just stated, the emphasis has been 
laid in these studies on the objective method. It has not 
seemed necessary or desirable to attempt to imagine the 
sensations of the experimental animals. To say, for 
example, that the animal feels dizzy, is to make an assump- 
tion than can neither be proved nor disproved; while to 
say that the eyes show a particular form of nystagmus, is 
to state something which any competent observer may 
definitely confirm or deny. CHAPTER II 
COMPENSATORY MOTIONS AND 
COMPENSATORY POSITIONS 
The compensatory movements which are excited by 
rotational changes of position differ in different animals, 
in ways dependent largely on the various modes of loco- 
motion and the relative motility of different members 
of the body. Two characteristics of the movements, how- 
ever, are remarkably constant; they tend (1) to retain 
the field of vision existing at the beginning of the rotation, 
and (2) to restore the body to its original orientation 
in space. 
When a fish is rotated, the reaction is seen in move- 
ments of the eyes and fins. If a frog is placed on a turn- 
table, the first response to rotation to be observed, is a 
turning of the head in a direction contrary to that of the 
movement of the table. As the rotation continues, 
changes of position of the limbs occur, and, finally, the 
animal begins to walk in a direction contrary to 
the motion. 
A pigeon responds to rotation at first by a very decided 
contrary movement of the head. This continues till a 
maximum angle has been reached, when a sudden, jerking 
motion brings the head back toward the median line, 
and then the compensatory movement begins over again. 
In this way a more or less uniformly rhythmical succes- 
sion of compensatory and return movements is kept up. 
These repeated movements are called nystagmus. The 
17 18 
LABYRINTH AND EQUILIBRIUM 
pigeon’s eyes also show a nystagmus of the same char- 
acter as that of the head. The eye movements become 
more pronounced if the compensatory movements of the 
head are prevented. 
The compensatory movements of reptiles, as described 
by Loeb145 in the horned lizard, Phrynosoma, and by 
Trendelenburg and Kuhn in snakes and turtles, are in the 
main very similar to those of birds. 
In mammals the compensatory motions are not differ- 
ent in essentials from those of other vertebrates. Mice, 
guineapigs, and rabbits on a turntable respond to rota- 
tion first by compensatory movements of the head and 
of the eyes, and on continued rotation, if the rate is not 
too great, by walking in a circle in a direction contrary to 
the motion of the table. The eye movements usually take 
the form of a nystagmus, which is more pronounced if 
the head is not allowed to turn on the neck. In man 
compensatory motions of the head are not likely to occur 
but the eye nystagmus is characteristic. In young in- 
fants, however, Bartels24 found that compensatory move- 
ments of the head occur regularly. Sleeping infants and 
infants prematurely born show compensatory movements 
of the eyes but no nystagmus. 
In the foregoing paragraphs reference has been made 
to the reaction winch occurs during rotation. When the 
rotary movement is arrested an after-reaction usually 
takes place in a direction opposite to that which occurs 
during the rotation. The after-reaction may consist 
merely in a return to the normal, resting position, or it 
may be even as pronounced as the original reaction, but 
in the opposite sense. Thus when a rabbit is rotated to 
the right, the head goes to the left, and at the same time COMPENSATORY MOTIONS AND POSITIONS 
19 
a nystagmus of the eyes occurs with the slow movement 
to the left. When the rotation is checked the head goes to 
the right, usually only far enough to return to the midline, 
and at the same time an eye nystagmus of some seconds 
duration sets in, with the slow component to the right. 
The statements just made refer to movements in the 
horizontal plane. All the reactions are, in the termin- 
ology of Mach, dynamic in character, that is, they are 
responses to movement; they disappear after the effect 
of the movement has subsided. Rotations in planes other 
than the horizontal also give rise to movements which 
are compensatory in the plane of the rotation, and, in so 
far, are dynamic; but if the rotary movement is stopped 
and the body is held in the abnormal position which has 
been reached, the compensatory position is retained. 
Thus if a dogfish or a rabbit is held with the body in the 
normal horizontal position, and is then rotated to the 
right around the horizontal axis of the body, so that the 
right side is inclined downward and the left side upward, 
a compensatory movement of the eyes occurs; the right 
eye is elevated and the left eye is depressed; but if the 
body continues to be held in the inclined position thus 
attained, the unsymmetricai position of the eyes is re- 
tained. In this, then, is seen both a dynamic reaction to 
the effect of the movement, and a static effect as the 
result of the sustained abnormal position. 
The static reactions, or compensatory positions, occur 
in all classes of vertebrates. In birds and fishes they 
have long been recognized. Their exact study and de- 
scription in mammals has been more recently contributed 
by Magnus and his co-workers. 20 
LABYRINTH AND EQUILIBRIUM 
For experiments on the equilibrial functions of the 
labyrinth, elasmobranch fishes present many advantages. 
On account of the cartilaginous structure of the skull, 
operations may be performed with relative ease, and 
without disturbance through bleeding. The different 
parts of the labyrinth are large and are so situated that 
each may be stimulated or extirpated without necessary 
injury to the others. The animals are easy to keep quiet 
during operation and survive the effects well. For these 
reasons a more complete account of the reactions of the 
dogfish will be given. The compensatory motions of the 
eyes and fins in the dogfish, as first described by Loeb,143 
are remarkably constant. Detailed studies of these move- 
ments have since been made by Lee,137 Kubo,130and others. 
So far as I am aware, the dogfish shows no well defined 
reactions to movement of translation, that is, to movement 
in a straight line. On the other hand change of direction 
in the horizontal plane, or change of position with refer- 
ence to the horizontal plane, calls forth prompt and char- 
acteristic responses. Such changes may be regarded as 
movements of rotation. When the fish which has been 
swimming in a straight line alters its course to some other 
in the horizontal plane, that is, to the right or left, the 
change involves a rotation around the dorsoventral axis 
of the body. If the animal sways to one side so that, for 
example, the belly turns to the right and the back to the 
left, the movement is a rotation around the longitudinal 
body axis. When the animal changes position so that the 
head goes downward and the tail upward, or the reverse, 
a rotation has occurred around the transverse axis. 
All changes of position, except movements of trans- 
lation, may then be regarded as rotations. All rotations COMPENSATORY MOTIONS AND POSITIONS 
21 
whatever can be referred to movements about one or more 
of a system of three body axes perpendicular to each 
other, the longitudinal, the transverse, or right to left, 
and the vertical, or dorsoventral. When the dogfish is 
rotated around any one of these axes the eyes move as if 
to retain their original position in space, or to preserve 
the original visual field, while the fins move so as to tend 
to swing the body back into its original orientation in 
space. We shall state the reactions to rotations around 
each of the primary axes separately. 
Rotation to the right around the longitudinal body 
axis, that is, right side inclined downward and left side 
upward, causes the right eye to move dorsalward and the 
left eye ventralward (Fig. 1, B.), so that more of the white 
appears below on the right eye and above on the left eye. 
Thus in spite of the rotation of the body the two eyes 
tend to remain in the same horizontal plane.v At the same 
time the right pectoral fin moves ventrally, its posterior 
margin more than its anterior, and the left pectoral moves 
dorsally, its posterior margin more than its anterior. 
The pelvic fins make a similar though less vigorous change 
of position. In this way the fins are given a screw-like 
set, so that if the body were propelled forward through 
the water the effect would be to cause a rotation to the 
left around the longitudinal axis. Thus the rotation calls 
out reflex movements of the fins exactly suited to effect a 
counter-rotation. Rotation to the left around the longi- 
tudinal axis causes eye (Fig. 1, A.) and fin movements 
which are exactly the reverse of those just described. 
When the fish is rotated around the transverse axis in 
such a way that the head goes upward and the tail down- 
ward the eyes make a rotational movement on their axes 22 
LABYRINTH AND EQUILIBRIUM 
in a direction contrary to that of the body (Fig. 1, C.), or, 
in other words, the anterior pole of each eye-ball goes 
downward and the posterior pole goes upward. The 
movement is such as would be made if the eyes were 
wheels on which the body was rolled forward, and hence 
Fiq. 1.—Diagrams of compensatory positions of eyes of dogfish; A, rotation to left and B, rota- 
tion to right around longitudinal body axis; C, rotation head upward and D, rotation head downward 
around transverse body axis; E, rotation to left and F, rotation to right around dorsoventral axis. 
for brevity I shall describe it hereafter by saying that the 
eyes roll forward on their axes. At the same time the 
pectoral fins move ventralward, their posterior margins 
more than their anterior. The pelvic fins also move 
slightly ventalward. If the body was moving forward in 
the water this set of the fins would bring it back from 
the inclined position to the horizontal. Rotation of the COMPENSATORY MOTIONS AND POSITIONS 
23 
body around the transverse axis toward the head down 
position causes the eyes to roll backward on their axes 
(Fig. 1, D.), and the paired fins to move dorsalward. 
The responses to rotations around the longitudinal 
and the transverse axes are both dynamic and static; 
that is to say, the compensatory positions are retained 
if the animal is held in the abnormal position arrived at 
as the result of the rotation. 
When the dogfish is rotated around a vertical axis, 
that is, in the horizontal plane, the two eyes make a con- 
jugate movement in the direction opposite to the rotation. 
If the head is turned to the right, both eyes go to the 
left (Fig. 1, F.); if the head is turned to the left, both eyes 
go to the right (Fig. 1, E.). Compensatory motions of 
the fins occur at the same time; when the fish is rotated to 
the right the dorsal fins move to the left and the caudal 
fin may also move to the same side. This arrangement 
of the fins is an effective steering apparatus to guide the 
course to the left, hence to counteract the effect of the 
rotation to the right. These reactions are dynamic only; 
the positions are not retained after the cessation of the 
rotation which provoked them, even if the animal is 
held in the new position which has been attained by 
the rotation. 
The effects of rotations in planes other than the prim- 
ary are readily resolved and are seen to be the resultant 
of simultaneous rotations around more than one of the 
primary axes. Thus the body may be rotated in a verti- 
cal plane around an axis which intersects the longitudinal 
axis so as to extend to the left anteriorly and to the right 
posteriorly. If the animal is rotated around this axis 
so that the head goes obliquely down and to the right, the 24 
LABYRINTH AND EQUILIBRIUM 
right eye goes up and the left eye goes down (the reaction 
to rotation around the longitudinal axis), while both eyes 
roll backward on their axes (reaction to rotation head 
downward around the transverse axis). Rotation head 
downward and to the left causes the left eye to go up, the 
right eye to go down, and both eyes to roll backward on 
their axes. 
Rotation head upward and to the right causes the right 
eye to go up, the left eye to go down, and both eyes to 
roll forward on their axes. Likewise, rotation head up- 
ward and to the left causes the left eye to go up, the 
right eye to go down, and both eyes to roll forward on 
their axes. 
The compensatory motions of the fins to rotations 
around oblique axes may also be resolved in the same way. CHAPTER III 
FORCED POSITIONS AND FORCED MOVEMENTS 
The facts described in the preceding chapter show 
that a mechanism exists through the action of which 
animals tend to maintain a definite position with reference 
to the lines of gravitational force. Any departure from 
that position calls forth changes in the tension of the 
muscles in such a way that the eyes and the locomotor 
organs are no longer held in a symmetrical position with 
reference to the body of the animat. , When a dogfish is 
held with its longitudinal axis horizontal, but with its 
right side inclined downward, the muscles which, by their 
contraction, lower the right eye, act less strongly than 
when the fish is in the normal position. The reverse state 
of things occurs in the muscles of the left eye; the muscles 
which elevate it act less strongly than when the fish is in 
the normal position. The result of these alterations of 
muscle balance is, that the eyes are compelled to take an 
unsymmetrical position with reference to the body. At 
the same time the paired fins also are placed in an unsym- 
metrical position through the unequal tension of the 
muscles on the two sides. 
These changes of muscle tension take place just as 
well in an animal in which the higher parts of the brain, 
the cerebral hemispheres, have been removed. They can- 
not therefore be attributed to volition, or to a conscious 
effort to avoid or to change a disagreeable sensation. 
They are determined with precision both as to amount 
25 26 
LABYRINTH AND EQUILIBRIUM 
and kind by the amount and kind of movement or change 
of position by which they have been called forth. 
Similar unsymmetrical distributions of muscle tonus 
can be caused by brain injuries of various kinds. They 
occur as the result of one sided injury to the medulla, 
the pons, the optic lobes, the corpora striata, and the cere- 
bral hemispheres. When these effects are due to brain 
injury, however, the inequality of muscular power is per- 
manent, and the resulting positions and movements are 
known as forced positions and forced movements. 
The experiments of Magendie, Flourens, Vulpian, 
Luciani, and others have made familiar the effects of one- 
sided injury to the cerebellum. Luciani’s147 description 
of a dog in which a part of the right side of the cerebellum 
has been extirpated shows that an unsymmetrical distri- 
bution of muscle tonus and strength is a marked symp- 
tom, especially in the first few days after the operation. 
The fore limbs are stretched out, the right more than the 
left, the vertebral column curves to the right, and when 
the animal is again able to walk it can not go in a straight 
line, but when it attempts to do so, curves off to the right, 
that is, makes circus movements. When the injury is 
more extensive, involving the middle peduncle, violent 
forced movements occur, the animal rolling around the 
long axis of the body. Forced positions and forced move- 
ments of the eye-balls, in the form of nystagmus 
also result. 
We are not concerned here with the old controversy as 
to whether these consequences of cerebellar injuries are 
to be regarded as the result of irritative processes or as 
true deficiency phenomena. Whatever the cause, it is 
evident that in its attempts at voluntary movement the FORCED POSITIONS AND MOVEMENTS 
27 
animal makes motions and assumes positions that were 
not intended, and that these differ in a definite way from 
the movements willed. It is evident, too, that one result 
of the destruction of a part of the cerebellum is a perma- 
nent weakness of certain muscle groups. 
Where circus motions occur, they must result from 
inequality of muscle force on the two sides of the body. 
When an animal curves to the right in walking, the devia- 
tion could be due to an increase of power in the muscles 
of the legs on the left side or to a decrease on the right 
side. There is a third possibility, namely, that an in- 
crease of power on the one side may be accompanied by 
a decrease of power on the other. When, however, the 
unsymmetrical action is caused by the loss of a portion of 
the brain, but one possibility exists: As has been pointed 
out by Loeb,146 “a permanent decrease but not a per- 
manent increase in the tension of the muscles can result 
from the destruction of one part of the brain.” 
The effects of cerebellar injury appear mainly on the 
side of the operation, because apparently, the fibres con- 
cerned do not cross to the opposite side. But a decussa- 
tion, or crossing over, of the fibres does take place from 
many parts of the brain so that destruction on the right 
side has its effect on the left side of the body and vice 
versa. Even the same part of the brain may have differ- 
ent connections in different animals. Thus Loeb141-126 
found that in the rabbit injury to one cerebral hemisphere 
causes circus motions toward the sound side, while a simi- 
lar operation in the dog causes circus movements to the 
injured side. 
Instead of a complete decussation there may be only 
a partial crossing of the fibres, so that the effects of the 28 
LABYRINTH AND EQUILIBRIUM 
lesion appear on both sides of the body. This condition 
is well shown by experiments on the dogfish. Loeb found 
that when the right side of the medulla is injured at the 
level of the entrance of the eighth nerve, there occur 
rolling movements to the right around the long axis of 
the body. When the animal comes to rest, the body is 
inclined to one side so that the right side is lower than 
the left. The eyes and fins are in forced positions, which 
can be described as a rotation around the long axis of 
the body. The right eye is depressed, that is, turned 
more ventrally, while the left eye is elevated or turned 
more dorsally. The forced position of the fins is just the 
reverse; the right pectoral fin is elevated and the left 
is depressed. 
It is evident that the unsymmetrical position of the 
eyes which follows section of the right side of the medulla 
can only occur if the muscles on both sides of the body 
are affected. The muscles which raise the right eye and 
the muscles which lower the left eye must act less strongly 
than their antagonists. The muscles of the fins of both 
sides also are affected by the unilateral injury. When 
the left side of the midbrain is destroyed analogous 
effects are produced. The body is inclined to the right 
and the animal, in swimming, makes circus motions to 
the right. 
The significance of the phenomena of forced move- 
ments for an understanding of the equilibrium reactions 
is shown by the two following results obtained by Loeb,144 
on the dogfish: (1) Section of the right eighth nerve 
causes forced positions and forced movements similar to 
those which are produced by injury to the left side of the 
midbrain and to the right side of the medulla, and (2) FORCED POSITIONS AND MOVEMENTS 
29 
the circus motions, the rolling, and the associated forced 
positions of the eyes and fins which are produced by in- 
jury to the left side of the midbrain and the right side of 
the medulla are completely abolished by section of the 
left eighth nerve. 
The brain injuries which have been referred to thus 
far are unsymmetrically placed as regards the plane of 
symmetry which divides the body into a right and a left 
half, and the forced movements which result can be 
thought of as rotations around one of two axes lying in 
that plane; they are either rolling movements around the 
longitudinal axis of the body or circus movements around 
the dorsoventral axis. Injuries which are symmetrical, 
that is, which involve equal structures on the right and 
left, may also give rise to forced positions and motions. 
These are of such nature that they can be regarded as 
rotations around the transverse axis of the body. 
Extirpation of the occipital lobes of the brain of the 
dog causes an elevation of the head and an abnormal 
extension of the forelegs. The animal is unable to go 
down stairs but can go up stairs. Corresponding opera- 
tions on the frontal lobes bring about a condition which 
is just the reverse. The head is held low and the animal 
shows a strong tendency to keep moving forward. 
Flourens81 described the effects of section of the pedun- 
cles of the cerebellum in the rabbit. When the posterior 
peduncles were cut, violent forced movements occurred; 
the animal sprang backwards or made somersaults back- 
wards. Section of the anterior peduncles caused the 
animal to hurl itself forwards. It is evident that these 
movements are analogous to those which are produced by 
one-sided injuries, only they are in another plane. 30 
LABYRINTH AND EQUILIBRIUM 
Flourens pointed out that cutting the posterior verti- 
cal pair of the semicircular canals had the same effect as 
section of the posterior peduncles of the cerebellum, while 
cutting the anterior vertical canals gave results similar 
to those obtained when he injured the anterior peduncles. 
Flourens ’ methods were not suited to give exact 
knowledge of the functions of the canals, and the infer- 
ences he drew as to the connections of the different parts 
of the labyrinth with the cerebellum have not been justi- 
fied by later work. Nevertheless his observations show 
in a striking way the similarity of the forced movements 
produced through the labyrinth and those which result 
from injury to the brain. The significance of this simi- 
larity is seen with very great clearness in connection 
with Loeb’s experiments described above on the brain 
and the eighth nerve of the dogfish. When one side of the 
medulla is injured, or when one eighth nerve is severed, 
the paired fins assume an unsymmetrical position which 
gives them the effect of the blades of a screw. If the 
animal now is propelled rapidly forward in the water, 
the screw effect of the fins causes the body to roll around 
its longitudinal axis. Tilting a normal dogfish to one side 
also causes an unsymmetrical position of the paired fins, 
which has the same screw effect as that produced by the 
operations mentioned. Propelling the body forward in 
the water must therefore produce the same forced rolling. 
But when the normal animal has rotated far enough to 
bring it back to its usual position of equilibrium the cause 
of the forced movement ceases to act and the fins return 
to their usual positions of symmetry with reference to 
the body. FORCED POSITIONS AND MOVEMENTS 
31 
The forced positions in the normal animal and in the 
operated animal are seen to be the same and their effects 
on the movements of the animals are the same. The 
essential difference lies in the fact already mentioned, 
that, in the normal animal, the position is automatically 
excited by a rotation and is automatically terminated by 
the counter-rotation which the first induces, while the 
forced position in the operated animal is more or less 
permanent. 
Forced positions of the fins can also be caused by 
retinal stimuli and by contact stimuli. The reactions to 
contact stimuli are very striking and I shall reserve the 
discussion of them for a later chapter. CHAPTER IV 
THE LABYRINTH AS A WHOLE 
1. The Effects of Destruction of One Labyrinth 
The effects of destruction of one or of both labyrinths, 
or of section of one or of both eighth nerves, have been 
described by many investigators and in a great variety of 
animals. In general, it may be said that the equilibrium 
disturbances arising from the loss of one labyrinth are 
very striking and very persistent. The symptoms usu- 
ally become less obvious after weeks or months, but never 
wholly disappear. 
The detailed studies of Ewald75 on the pigeon with 
one labyrinth removed are so well known that only a 
brief reference is needed here. Immediately after the 
operation, certain disturbances of position and movement 
begin to appear. Among these disturbances are seen a 
tendency to hold the head obliquely inclined to the oper- 
ated side. When the bird attempts to walk it may turn 
or fall, or in extreme cases, roll, to the operated side. 
The abnormalities of position, especially of the head, 
gradually become more marked. In the second and third 
weeks after the operation they are very intense. The 
head is not merely held in an oblique position but becomes 
twisted so that the beak points directly upward and the 
occipital region of the head is below. This extreme pos- 
ture is not maintained continuously but occurs when the 
bird atempts to make voluntary movements, and espe- 
cially when it is excited or frightened. After some 
months these disturbances almost wholly disappear. 
32 THE LABYRINTH AS A WHOLE 
33 
The pigeon runs about in the aviary, eats and drinks in 
a manner not to be distinguished from the normal ani- 
mals. Even in flying, the operated and the uninjured 
birds can hardly be distinguished. 
Notwithstanding the apparently complete recovery, 
Ewald was able to show that after loss of one labyrinth 
certain permanent effects remain. When, for example, 
the bird is suspended by the feet, the wing on the operated 
side is not drawn up so neatly as that on the sound side. 
The loss of muscular tonus which this indicates, appears 
more obviously on the operated side, but Ewald’s experi- 
ments make it clear that muscle groups on both sides of 
the body are affected. Thus the flexor muscles of the 
wing on the operated side are weakened, hence the partial 
extension under the influence of the weight of the wing 
when the bird hangs head down; but it can be shown that 
the extensor muscles of the wing on the sound side are 
also weakened. On the basis of these and other similar 
differences, Ewald founded his well-known theory of 
the tonus functions of the labyrinth. The facts of the 
influence of the labyrinth on muscular tonus are thor- 
oughly established; it is not necessary here to discuss 
the specific theory of Ewald in detail. 
The destruction of one labyrinth or the section of 
one eighth nerve gives certain results which seem to be 
common to all classes of vertebrates. Prominent among 
these are characteristic forced positions of the eyes and 
head and of the organs of locomotion. The eyes tend to 
deviate to the operated side; at the same time the eye 
on the operated side goes slightly downward and the eye 
on the sound side goes slightly upward. Eye nystagmus 
is often present for some days, with the slow movement 34 
LABYRINTH AND EQUILIBRIUM 
to the operated side. The head is inclined so that the 
operated side is lower than the sound side. In animals 
like the fishes where the head is not movable on the neck, 
the body is also inclined to the operated side. In am- 
phibians, reptiles, and mammals there is a tendency to 
extension or adduction of the limbs on the sound side. 
This is not so readily seen in birds but Ewald has called 
attention to analogous phenomena in the pigeon. The 
characteristic forced positions of the fins of operated 
fishes we shall describe below. As examples of these 
forced positions and forced movements after loss of one 
labyrinth, we may refer to the description by Ewald for 
the frog, to Trendelenburg and Kiihn233 for reptiles, to 
Dreyfuss72 for the guineapig, to Prince200,201 for the cat, 
to Bechterew30 and to Wilson and Pike238 for the dog, to 
Beyer and Lewandowsky36 for the ape, and finally for 
very thorough-going studies of the rabbit, guineapig, cat, 
and dog to Magnus and deKleijn.161 
All investigators since Flourens have noted the re- 
markably violent rolling movements which take place in 
the rabbit when one labyrinth is destroyed. Magnus and 
deKleijn161 have been able, by the use of motion pictures, 
to analyze the rolling. They have shown that the rolling 
is really a running which is so interfered with by the 
extreme tonus differences on the two sides of the body 
that almost no forward progression can be made. Each 
revolution of the animal is the result of two leaps. 
Animals with only one labyrinth, exhibit the righting 
reaction, but in doing so they seem to turn in one direction 
only. Thus Fisher and Muller80 found that if a cat with 
one labyrinth destroyed is held up by the feet and 
dropped, it rights itself during the fall and comes down THE LABYRINTH AS A WHOLE 
35 
on its feet, but that in doing this it always turns toward 
the operated side. If the left labyrinth has been de- 
stroyed the animal turns to the left while falling, and it 
does this even if it is dropped from the position in which 
the right side is below. In falling from the latter position 
the righting could occur either by turning 90 degrees to 
the right or 270 degrees to the left, but in the absence of 
the left labyrinth the cat invariably turns through the 
longer distance, the 270 degrees, to the left and not 
through the more direct way to the right. An exactly 
comparable reaction is seen in the dogfish. 
The reactions to rotations around a vertical axis, that 
is, in the horizontal plane, are affected in all these ani- 
mals but not in exactly the same way, or at least not to the 
same extent. These differences will be discussed in 
another connection. 
We shall now examine, somewhat more in detail, the 
effects of this operation on the Selachian. 
In the dogfish, section of one eighth nerve or total 
destruction of one labyrinth give essentially the same 
results. The behavior of animals so operated was de- 
scribed by Loeb144 and later by Lee137, 138 and others. 
Their descriptions agree in the main with what one sees 
in a common dogfish of the Pacific coast, Mustelus 
calif or nicus. 
When the right labyrinth of the dogfish is destroyed, 
the eyes and fins assume forced positions which are more 
or less permanent. The right eye goes down, that is, it 
takes a position more ventral than normal, so that the 
white of the eye is exposed above the iris, while the left 
eye goes up, or dorsally, exposing more white below the 
iris. The right eye is also turned slightly posterior, or 36 
LABYRINTH AND EQUILIBRIUM 
tailward, and the left eye slightly anterior. The paired 
fins are forced into positions opposite to that of the 
eyes; the pectoral and pelvic fins are elevated on the right 
side and those on the left side are depressed. The dorsal 
fins are bent to the left. 
In consequence of the forced positions of the fins, 
attempts at locomotion may cause the animal to roll to 
the right, around its longitudinal body axis. Circus 
movements also occur, the animal usually turning to the 
right, but circus motions to the left may sometimes be 
seen. After some hours, the animal swims about very 
much like the other fish in the aquarium, turning some- 
times to the right and sometimes to the left. It is seen, 
however, that the body is inclined so that the median 
plane is tilted to the right, that is, the right side is in- 
clined somewhat downward and the left side upward. 
The deviation from the vertical may amount to about 
thirty degrees. 
If the animal is taken from the water and returned 
belly upward it rights itself at once, but invariably turns 
to the right in doing so. If one holds the fish in the water 
and attempts to turn it so that its left side will be down 
a strong resistance is made, but very little resistance is 
presented to turning it with the right side down. 
When a dogfish with the right labyrinth destroyed, is 
rotated to the left in the horizontal plane, the eyes and 
fins give the normal reaction described in Chapter II; the 
dorsal fins bend to the right and the two eyes make a 
conjugate movement to the right. When the animal is 
rotated to the right there is no reaction of the eyes or fins. 
In general, when the fish is rotated around the dorso- 
ventral axis to the sound side, the normal reaction occurs; THE LABYRINTH AS A WHOLE 
37 
when the rotation is to the operated side, the reaction is 
absent. Rotation around the longitudinal axis causes eye 
and fin movements corresponding to those which occur 
in the normal animal, but with this difference, that these 
compensatory movements are superposed on the already 
existing forced positions; the right eye is already de- 
pressed and the left eye elevated, hence rotation to the 
right around the longitudinal axis merely causes the eyes 
to be returned part way towards their normal position, 
while rotation to the left increases the existing asym- 
metry. Rotation around the transverse axis produces 
reactions which differ but little from those of the nor- 
mal animal. 
As has been pointed out by Loeb, 144>146 certain muscle 
groups in the dogfish act as a unit in the equilibrium 
reactions (and probably in many other movements). 
Thus we have seen that, in response to rotations around 
the longitudinal axis, when one eye or one of the paired 
fins goes up the corresponding member on the other side 
of the body goes down. When the animal is rotated 
around the dorsoventral axis the eye movements are con- 
jugated; both eyes look to the left, or both to the right. 
The asymmetrical positions assumed by the eyes and 
fins as the result of injury, either to one eighth nerve or 
to one side of the medulla, can only be the result of tonus 
changes in muscles on both sides of the body. It might 
be assumed that the nervous mechanism which controls 
the paired fins acts as a unit for the two sides and that the 
muscles of the two eyes likewise act as a unit, so that the 
one pectoral fin or the one eye can not move without a 
definitely related movement of its fellow; a tonus change 
which affects the position of one eye or one paired fin 38 
LABYRINTH AND EQUILIBRIUM 
must therefore produce a related change in position of the 
fin or eye on the other side. Such an assumption has 
been rather commonly made for the eye musculature, 
although it is well known that a, certain amount of inde- 
pendent movement of the two eyes is possible even in 
man. If a prism of small angle is placed before one eye, 
objects appear doubled because the images no longer fall 
on corresponding points of the two retinas. But by vol- 
untary effort one can bring the eyes into the position in 
which the images do fall on corresponding points and the 
objects appear single once more. Bartels26 and others 
have shown by kymograph tracings that the two eyes do 
not react exactly alike to rotation on the revolving table, 
especially after asymmetrical labyrinth operations. 
In the shovel nosed ray, Rhinobatus, the equilibrium 
reactions of the two eyes are beautifully coordinated, and 
the asymmetrical positions which result from labyrinth 
injuries are practically the same as those which we have 
described for the dogfish. The anatomical arrangements 
are, however, quite different. The eyes of the dogfish 
are on the sides of the head with their visual axes almost 
horizontal. The eyes of the ray are on the dorsal side of 
the broad flattened head, and can be elevated or retracted 
in a manner which closely resembles the movements of 
the eyes of the frog. In the frog, however, there is a 
definite muscle, the retractor bulbi, which is used to 
retract the eye-ball. The rays do not possess a retractor 
muscle; the eyes are pulled down by the contraction of 
some or all of the usual six eye-muscles. It will contrib- 
ute to the understanding of the nature of the symmetri- 
cal eye movements in the equilibrium reactions if we have THE LABYRINTH AS A WHOLE 
39 
a knowledge of the extent of independent motion possible 
to each eye singly.175 
When a Rhinobatus is placed on a shark-board and 
supplied with plenty of aerated sea water through a 
rubber tube, little or no tying is necessary to keep it in 
position. Under these conditions a contact stimulus ap- 
plied to the upper surface of the head or snout excites 
certain very definite coordinated movements of the fins 
and eyes, the particular combination of movements de- 
pending on the locus and strength of the stimulus. 
If the skin of a Rhinobatus is gently stroked with the 
finger or with a blunt instrument at any point along the 
midline of the head, for example, between 7 and 8 (Fig. 2), 
both eyes are retracted, the movements of the two being 
approximately equal. If a similar stimulus is applied 
near the outer margin of the upper surface of the head, 
as at 1 (Fig. 2), the eye on that side is retracted strongly, 
the other eye is moved very little or not at all. If trials 
are made at other places, e.g., at 2 or 3 (Fig. 2), it is seen 
that, as the point stimulated approaches the midline, the 
amount of movement of the two eyes becomes more and 
more nearly equal, or in other words, the relative amount 
of retraction of each eye varies inversely with its dis- 
tance from the point of application of the stimulus. 
It was relatively easy to record these movements 
graphically. An Engelmann pincette was attached to 
each eye by a fold of the integument just where the rudi- 
mentary lid passes over into the cornea. The pincettes 
were connected by threads to a pair of light heart levers 
in such a way that retraction of an eye gave an upward 
direction to the curve. In the tracing here reproduced, 
Fig. 3, the upper lever was connected with the left eye 40 
LABYRINTH AND EQUILIBRIUM 
and the lower with the right. 
The writing points were placed 
as nearly as possible in the 
same vertical line, but in order 
to make the relations more 
certain, simultaneous ordinates 
were marked throughout. The 
small rhythmical oscillations 
are respiratory, rather than 
eye movements. Spontaneous, 
“voluntary” movements occur 
occasionally, as between 6 and 
7, near the end of the tracing. 
In this experiment the stimulus 
employed was a gentle stroke 
with the finger. These strokes 
were made as nearly equal as 
possible, but the method could 
hardly be expected to give 
perfectly uniform results. The 
number at the bottom of the 
tracing show the points stimu- 
lated as charted on Fig. 2. 
Certain peculiarities should 
be mentioned. While the re- 
sponses could be obtained from 
contact stimuli on all parts of 
the upper surface of the head, 
some parts were noticeably 
more sensitive than others. 
Also some parts were less likely than others to produce 
the bilateral response. Thus the strength of stimulus 
Fio. 2.—Diagram of dorsal view of Rhino- 
batus Productus. THE LABYRINTH AS A WHOLE 
41 
used in securing the tracings reproduced, rarely gave 
rise to a retraction of both eyes when applied at 5 or 6, 
very near the inner margin of the eye. Stimuli applied 
to the lower surface of the snout, even near the lateral 
margin where the upper surface was very sensitive, 
were very slightly or not at all effective. 
The movements which I have just described are retrac- 
tion of the bulbs and partial closure of the rudimentary 
lids, and are not at all to be confused with the conjugate 
movements which result from excitation of the labyrinth. 
I have observed the same kind of independent move- 
ments of the eyes in all the skates and rays which I have 
had the opportunity to examine and have made graphic 
records of these movements in several different genera. 
It also is probable that the paired fins are capable of 
much independent movement, but it did not seem im- 
portant to examine this point because in the higher verte- 
brates this condition is characteristic. 
In the ordinary movements of the eyes as well as of the 
fins, Sherrington’s principle of reciprocal innervation is 
exhibited. When the left eye is turned to look to the 
right, the rectus internus of that eye contracts but at the 
same time the antagonistic muscle, the rectus externus, 
is not merely passively stretched but definitely relaxes. 
While this movement is made by the left eye, the right 
eye moves correspondingly and its movement involves 
contraction of its rectus externus and relaxation of its 
rectus internus. In every case in which a pair of body 
members makes associated movements like those which 
occur in the fish in response to rotations in the various 
planes, four muscles or groups of muscles must have 42 
LABYRINTH AND EQUILIBRIUM 
their innervation simultaneously affected. Magnus has 
shown that in the higher vertebrates also, each labyrinth 
influences muscle tonus on both sides of the body, and in 
such a way that the flexors on the one side and the exten- 
sors on the other are affected in the same sense; an 
increase of tonus of the extensors of a right limb is accom- 
panied by an increase in tonus of the flexors of the corre- 
sponding left limb. In view of the possibility of free 
and independent movement of each member separately, 
this orderly distribution of tonus effects from the laby- 
rinth is especially striking. 
2. The Effects of Destruction of Both Labyrinths 
After section of the two eighth nerves or destruction 
of the two labyrinths in the dogfish, no definite forced 
positions or forced movements are seen. The eyes and 
fins maintain their symmetrical position, and the animal 
is able to swim in a manner which can appear quite nor- 
mal. If, however, the fish is placed in the water with the 
belly up, it swims off in that position and may not right 
itself for some little time, or it may make irregular rolling 
movements. When held in the water in the normal posi- 
tion it offers none of the resistance to being passively 
turned back downward which is so characteristic of the 
fish possessing both labyrinths. In short, the geotropic 
reactions appear to be wholly abolished. 
Kreidl127 gives a similar description of dogfish in which 
only the otoliths have been destroyed; but he adds that the 
operated fish when at rest could be quietly turned over 
with a glass rod and would lie for a long period on their 
backs. When swimming about the aquarium they came 
to rest on their backs sometimes and remained in that Fig. 3.—Tracing of eve movement of Rhinobatus in response to contact stimuli Upper curve, movements of left eye; lower curve, right eye. The 
numbers correspond to points stimulated as indicated on riG. x. THE LABYRINTH AS A WHOLE 
43 
position. When a number of the operated fish were kept 
in the one aquarium they often came to rest lying upon 
one another, any side up, like a heap of dead fish. Lee137 
gives a somewhat similar account of the effect of section 
of both eighth nerves. He states, “The animal may be 
placed upon his belly, his back, or either side without 
manifesting objection, and, after swimming, he may come 
to rest in any one of these positions. In reclining he is 
perhaps most easy in his customary resting position 
with belly downward, yet he does not appear to be seri- 
ously inconvenienced by any other attitude, and, when 
supported by the side of the tank, has been seen to rest 
standing on his head.” 
My observations differ somewhat from those jtist 
quoted. Dogfish with both labyrinths completely de- 
stroyed will, ordinarily, swim about quietly in a manner 
hardly to be distinguished from normal animals. Only 
when greatly or suddenly excited do they show the dis- 
turbances of equilibrium described above. Vigorous 
specimens, in good condition, come to rest in the same 
position as unoperated fishes. Only when in a moribund 
state or excessively fatigued do they lie in the abnormal 
positions described by Kreidl. This matter will be dis- 
cussed in the next chapter. 
Labyrinthless dogfish usually give no reaction of eyes 
or fins when rotated around any one of the three body 
axes. In rare instances I have observed a slow com- 
pensatory movement of the eyes when the fish was ro- 
tated around its longitudinal axis. The movement is 
much slower than that which occurs when the labyrinth 
is functional; it occurs so seldom that I have not been able 44 
LABYRINTH AND EQUILIBRIUM 
to investigate it properly, but I believe it to be a retinal 
reflex. Lyon, however, has described occasional com- 
pensatory movements after section of both eighth nerves 
and both optic nerves as well. 
Destruction of the two labyrinths in the frog produces 
great disturbances of equilibrium. The animal makes 
violent, disorderly movements when laid on its back, and 
has great difficulty in righting itself. In the water it is 
badly disoriented, and rolls around irregularly making 
little forward progress; the swimming movements are 
not well executed; the two hind legs make irregular pad- 
dling, instead of the usual simultaneous strokes. On land 
the leaps show disturbances in the use of the voluntary 
muscles. No equilibrium reactions are seen on the turn- 
table, if retinal images are excluded. 
In another amphibian, Siredon, Laudenbach132 saw, 
after destruction of both labyrinths, disturbances of 
orientation and irregular rollings when the animal at- 
tempted to swim. When worn out with long continued 
swimming and rolling, the animal sank to the bottom and 
lay in any chance position until it was rested; then it 
oriented itself normally. 
In birds, the account by Ewald75 of the condition of 
the pigeon with extirpated labyrinths remains the classic. 
At first very serious disturbances in the use of the muscles 
occur. The animals must be given food and drink arti- 
ficially. At a later stage the birds deport themselves 
more normally. They run about on the ground, drink, 
and pick up their food much like the uninjured birds; 
but they do not fly. When the eyes are covered the head THE LABYRINTH AS A WHOLE 
45 
is held in an abnormal position. On the turntable eye- 
nystagmus occurs during rotation but no after-effect ap- 
pears. The eye-nystagmus, however, does not occur 
when moving retinal images are excluded by surrounding 
the bird with a gray paper cylinder which rotates with 
the turntable. Ewald laid great stress upon the fact, 
proved by many experiments, that in the pigeon, the vol- 
untary muscles are markedly weakened after loss of both 
labyrinths. This is indicated, among other things, by a 
seeming looseness of the muscles of the neck which allows 
the head to swing around freely on account of its own 
weight and inertia. 
Experimental work on the labyrinth of reptiles is not 
extensive. Trendelenburg and Kiihn233 have described 
the effects of destruction of both labyrinths in a lizard, 
a turtle and a water-snake. The resting position of the 
operated lizard does not differ from the normal. There 
is a certain amount of insecurity in rapid movement, so 
that the animal at times falls or turns over. Lack of 
skill is seen in climbing and in catching food. The right- 
ing reflex occurs promptly, but the muscular movements 
are not well coordinated and the animal may roll around 
for a time before getting securely on its feet again. In 
swimming, the lizard is wholly disoriented and rolls over 
in all sorts of ways. On the turntable during rotation, 
the compensatory position of the head is normal and eye- 
nystagmus occurs, but there is no after-effect either in the 
form of compensatory position of the head or nystagmus 
of the eyes. That the reactions during rotation are due 
to moving retinal images, is shown by the fact that, if the 46 
LABYRINTH AND EQUILIBRIUM 
eyes are closed, neither reaction during rotation nor after- 
effect on stopping can be detected in the operated animal. 
The water-snake, Tropidonotus natrix, after loss of 
both labyrinths seems to creep almost normally, but, on 
stopping, the head sways from side to side for a time. 
In the water the snake almost never rolls over, but occa- 
sionally may swim in a spiral or figure eight. The loose 
holding of the head is seen in swimming. The normal 
snake holds the head and first few vertebral segments 
straight in the line of progression, while the remainder 
of the body makes characteristic undulatory movements. 
The operated snake allows the neck and head also to par- 
ticipate in the side to side oscillations. In the mud turtle, 
Emys lutaria, destruction of both labyrinths produces 
still less disturbance. Nothing abnormal is seen in the 
resting position. Laid on its back the animal rights itself 
like a normal turtle. Orientation occurs both while swim- 
ming at the surface and when submerged. There is more 
swaying while swimming than in the normal animal, but 
there is no complete disorientation. Compensatory 
movements are nearly if not wholly absent. 
\ In mammals, as a rule, the disturbances following the 
destruction of both labyrinths are at first very severe, 
but they do not present the stormy character of those 
which follow the one-sided operation. There is no forced 
position; rolling movements are absent or only very 
transitory. Dogs and cats are for a time unable to stand. 
When the head is raised it swings from side to side, mak- 
ing it difficult or impossible for the animal to seize its 
food. Nystagmus of an irregular sort may persist for 
a few days. All these symptoms gradually disappear, THE LABYRINTH AS A WHOLE 
47 
until finally there is little in the ordinary behavior, to 
distinguish the operated from the normal animal. A 
labyrinthless dog, however, always shows some lack of 
skill in the use of the voluntary muscles; he is not accu- 
rate in catching with his mouth pieces of meat thrown 
to him, and he tends to slip when he runs on a smooth 
floor. Moreover, he is disoriented and helpless when his 
eyes are bandaged. Wilson and Pike238 found that the 
dog without labyrinths was likely to roll and tumble about 
when thrown into the water, but could sometimes orient 
itself promptly and swim in a fairly normal manner. CHAPTER V 
REACTIONS OF NON-LABYRINTHINE ORIGIN 
If we turn a planarian worm on its back (dorsal side) 
it immediately rights itself. The movement has the ap- 
pearance of a true geotropic reaction; but if the worm is 
placed with its dorsal side in contact with a vertical sur- 
face, e.g., the wall of an aquarium jar, the righting reac- 
tion takes place just as well. Even when the planarian, in 
swimming, comes to the top of the water, a righting reac- 
tion occurs in which the organism places itself with its 
ventral side up, and creeps on the under side of the sur- 
face film. It is evident that these reactions are not geo- 
tropic; they do not depend on the lines of force of the 
earth’s attraction, but are brought about through the 
effects of contact stimuli. The worm is so organized 
that the touch of a solid body against the dorsal surface 
causes the coordinated muscular movements necessary 
to turn the animal over and bring its ventral side into 
contact with the solid. 
When a dogfish is turned belly upward in the water 
it very promptly rights itself. The action takes place 
under conditions which show that the cause is essentially 
different from that which produces the righting move- 
ments of the planarian, for the fish is surrounded on all 
sides by a medium which presses equally in all directions 
and so presents uniform contacts to every part of the 
body surface. We have seen that under these conditions 
this reaction fails in a dogfish deprived of its two laby- 
rinths, but that, nevertheless, such a fish rights itself 
48 REACTIONS OF NON-LABYRINTHINE ORIGIN 
49 
promptly as soon as it comes in contact with the bottom 
of the aquarium. There are, then, at least two ways in 
which the righting reaction of the fish may be brought 
about, one of them geotropic and the other stereotropic. 
When a normal pigeon is rotated on the turntable a 
nystagmus is produced. If both ears are destroyed, ro- 
tation still causes nystagmus, or, if the ears are intact 
but the animal is blinded, a nystagmus still follows rota- 
tion. When, however, the bird is deprived of both eyes 
and both ears at the same time, rotation no longer excites 
a reaction. It follows from this that equilibrium reac- 
tions may be brought about through retinal stimuli also. 
Since reactions which are alike or which have very 
considerable resemblance may arise from the stimulation 
of different receptor organs it becomes necessary to study 
the retinal effects and the contact reactions in the animals 
which are used for experiments on the functions of 
the labyrinth. 
1. Contact Reactions 
During two summers of experiments on dogfish, the 
animals were kept in a concrete tank ten feet long and 
six feet wide with a depth of water which varied from 
one to two feet. The fish sometimes rested quietly on 
the bottom; at other times they swam round and round, 
keeping usually near the walls. When dogfish in which 
both labyrinths had been completely destroyed were 
placed with the others in the tank their behavior, except 
when greatly excited, could hardly be seen to differ from 
that of the normal animals. They swam quietly around 
or settled on the bottom in normal orientation. 50 
LABYRINTH AND EQUILIBRIUM 
The orientation of the labyrinthless dogfish might 
have been due to retinal stimuli; that it was not so was 
proved in the following way: A dogfish in which both 
labyrinths had been destroyed on the preceding day was 
observed to orient itself, in swimming, like a normal fish, 
and to come to rest right side up on the bottom of the 
aquarium. Over each eye of this animal I sewed a large 
patch of heavy, black, rubber cloth. This cloth extended 
on all sides some distance beyond the eye and was stitched 
directly to the skin of the fish. When the animal was 
returned to the water its behavior was almost, but not 
exactly, as before. It swam about with good orientation 
and never came to rest on the bottom in an abnormal 
position. Under these circumstances the organism is 
deprived of two of the three kinds of impulses on which 
its orientation in space depends. It is now without 
retinal and labyrinthine stimulation and must rely upon 
contact stimuli alone. 
When the normal dogfish were swimming around the 
aquarium keeping near to the walls, their bodies were 
almost always slightly tilted so that the side away from 
the wall was a little deeper in the water than the side 
next the wall; the belly was thus turned slightly toward 
the wall, and usually, too, the first dorsal fin, instead of 
being held in a position symmetrical to the body, was 
flexed to the side next the wall. Dogfish which had been 
blinded and deprived of both labyrinths exhibited this 
phenomenon, but in a more marked degree. Such ani- 
mals were frequently seen swimming along the side of 
the aquarium with their bellies turned directly to the wall 
exactly as if the wall had been the bottom the animals REACTIONS OF NON-LABYRINTHINE ORIGIN 
51 
in swimming were oriented to a, vertical instead of a 
horizontal surface. In this orientation they often swam 
the length of the tank. It is probable that if the available 
distance had been greater the weight of the fish would 
soon have brought it into contact with the bottom. 
The foregoing observations made it desirable to 
investigate in more detail the contact reactions of 
the dogfish.176 
A dogfish tied down on the shark board and supplied 
with a current of aerated sea water responded to stroking 
or scratching stimuli applied to the head or snout with 
decided movements or changes of position of the fins; 
but the results were often confusing or contradictory. 
A contact stimulus applied to the right upper surface of 
the snout would at one moment cause the dorsal fins to 
turn to the right, while at another moment a stimulation 
of the same region caused these fins to bend to the left. 
The paired fins and the tail participated in these re- 
sponses, and the direction of their movements had a de- 
finite relation to the movements of the dorsal fins. It 
became apparent that these fin movements were always 
consistent among themselves; they were more than simple 
reflexes, and showed a coordinated adjustment of the 
organism as a whole. In general they could be seen to 
exhibit such an arrangement as would be necessary to 
turn the animal either in the direction of the stimulating 
object or away from it. That is to say, the reactions were 
in each case stereotropic, but the sense of the stereo- 
tropism could be positive or negative. It became then 
a matter of interest to determine, if possible, the condi- 
tions of the reversal, and so to control these conditions as 52 
LABYRINTH AND EQUILIBRIUM 
to make the responses predictable. This proved to be 
indeed very simple. 
In making these experiments on the effects of contact 
stimuli it would have been desirable to keep the fish in its 
natural position in the water. This however was imprac- 
ticable because the mechanical effect of the stroke or push 
which constitutes the stimulus was sufficient to move the 
body of the fish under the unstable conditions of water 
support only. Moreover the stimulus excited movements 
of locomotion and the observer was unable to keep track 
of the positions and changes of position of the different 
fins. If the aquarium used was large the fish was soon 
out of reach; if small, new stimuli were offered by colli- 
sion with the walls. Another disturbing factor, if the 
animal is floating in the water and free to move, is the 
fact that each response to a tactile stimulus causes such 
a change of position as to excite the labyrinth and thus 
introduce other reflexes. It was necessary, therefore, 
to use the ordinary method of artificial respiration by 
means of a current of aerated sea water through a rubber 
tube in the animal’s mouth. 
When the dogfish is first placed on the shark board 
rather violent struggles occur, and tying is usually neces- 
sary until the animal becomes quiet. After a few min- 
utes of immobility the cords can be gently loosened and 
removed and the experiment can go on for some time 
without any need of artificial restraint. This is impor- 
tant because experiments on contact stimuli should not 
be complicated by possible inhibitions or reenforcements 
from the presence of the binding cords. It is true that 
the ventral surface of the body is still in contact with the 
board, but this is not an unnatural situation since the REACTIONS OF NON-LABYRINTHINE ORIGIN 
53 
animal when free, often rests for long periods on the 
bottom of the aquarium. In order better to observe the 
movements of the paired fins, the animal was usually 
placed above the board on a thick piece of wood no wider 
than the body, thus allowing the pectorals to project 
like wings. 
The reactions about to be described were obtained by 
stroking or scratching the outer margin of the head from 
near the snout to a point just below the eye. It was not 
necessary that the stroke be carried the whole distance; 
a short stroke or sometimes a mere touch anywhere 
within the region mentioned gave the same result. It is 
not to be inferred that analogous reactions are not elicited 
by contact stimuli applied to other regions. I have 
confined this account to reactions from the parts men- 
tioned for the sake of definiteness of description 
and interpretation. 
For most dogfish a stroke with a finger wet with sea 
water was sufficient to produce a definite response. As 
a more severe stimulus I used a scratch with the points 
of a small pair of forceps. The first of these usually 
corresponds to the designation “weak” the other 
“strong” stimulus. 
It soon became apparent that fairly constant responses 
could be obtained if the stimuli were of uniform intensity. 
In fact under favorable conditions the movements could 
be repeated over and over with machine-like regularity. 
The following portion of the record of an experiment is 
typical (Table I.). The pauses between the successive 
trials were merely the time necessary to set down 
the results. 54 
LABYRINTH AND EQUILIBRIUM 
TABLE I. 
REACTIONS OF A DOGFISH TO CONTACT STIMULI. 
Mustelus californicus, S3 Inches Long, May 20, 1921. 
Stimulus 
Reaction 
Kind 
Side 
D1 
D2 
Tail 
Right 
Pectoral 
Left 
Pectoral 
Weak (Finger) 
Left 
Left 
Left 
Left 
Down / 
Up/ 
Right 
Right 
Right 
0 
Up\ 
Down / 
Left 
Left 
Left 
Left 
Down / 
Up/ 
Right 
Right 
Right 
Right 
? 
Down / 
Left 
Left 
Left 
Left 
Down / 
Up? 
Right 
Right 
Right 
? 
Up\ 
Down / 
Strong (Forceps) 
Left 
Right 
Right 
Right 
Down\ 
Up/ 
Right 
Left 
Left 
Left 
Up/ 
Down/ 
Left 
Right 
Right 
? 
Down/ 
Up/ 
Right 
Left 
Left 
Left 
Up/ 
Down/ 
Weak (Finger) 
Left 
Left 
Left 
Left 
Down / 
Up/ 
Right 
Right 
Right 
Left? 
Up\ 
Down / 
Left 
Left 
Left 
0 
Down / 
Up/ 
Right 
Right 
Right 
Right 
Up\ 
Down / 
Strong (Forceps) 
Left 
Right 
Right 
Right 
Down/ 
Up/ 
The first column indicates the strength of stimulus; the second, the 
side of the head to which it is applied; the third, fourth, and fifth, the 
direction of movement of the first and second dorsal and the tail fins, 
respectively. The last two columns give the direction of movement of the 
anterior border of the right and left pectoral fins; and, in these two 
columns, j at the end of the word indicates that the posterior end of the 
fin was higher than the anterior;\, that the posterior margin was lower 
than the anterior. 
Inspection of the results of the above experiment 
shows that when a weak stimulus is used the dorsal fins 
and the tail turn toward the stimulated side. The effect 
of these as a steering apparatus would be to change the REACTIONS OF NON-LABYRINTHINE ORIGIN 
55 
course toward the stimulated side; e.g., turning the dorsal 
fins or the tail to the left would cause the course to swerve 
to the left. But in addition to this another effect would 
result. When a dorsal fin turns to the left it assumes an 
oblique position; that is, it is its posterior border which 
goes to the left most strongly. Its resistance as the 
animal moves forward in the water would have a screw 
effect, tending to rotate the body around its longitudinal 
axis so that the ventral side would be turned in the direc- 
tion of the stimulating object. This rotation effect would 
be increased by the new position of the pectoral fins. 
The pectoral on the stimulated side is elevated but its 
posterior margin is raised less than its anterior or is 
even depressed; the pectoral of the other side makes a 
movement which is just the converse. These fins would 
then also have a screw effect tending to the same direction 
of rotation as the dorsals, namely, ventral side toward the 
stimulating object. The reaction is clearly tropic and in 
the positive sense. 
It will be seen that the total effect of a weak stimulus 
is to turn the ventral side of the animal, as well as to 
swerve the course, in the direction of the stimulating 
object. As stated above, normal dogfish are often seen 
going round and round, keeping near the walls, with the 
body tilted to one side so that the mouth and belly are 
turned somewhat toward the wall. This is just the posi- 
tion which would be produced by the above reactions, if, 
on making the turn at a corner, the edge of the snout 
came slightly in contact with the wall. Sometimes I have 
been able to see such contacts actually occurring, but the 
asymmetrical position was often assumed when the wall 56 
LABYRINTH AND EQUILIBRIUM 
was not touched. In this case it might be that the in- 
creased pressure or resistance of the water when the fish 
was moving near the wall could act as a stimulus. Indeed 
I found that a spurt of water from a pipette could be used 
instead of a finger stroke as a weak stimulus. 
For the benefit of anyone who still inclines to the 
anthropomorphic interpretation of the behavior of the 
lower animals it may be added that these reactions occur 
just as well in the dogfish in which all of the fore brain 
has been destroyed. Indeed beautiful contact responses 
were obtained from a blinded, labyrinthless fish in which 
the brain had been cut through at the level of the anterior 
margin of the optic lobes. 
These reactions are not confined to the lower verte- 
brates; they are seen also in mammals. Magnus156 has 
described righting reactions in the rabbit, which are in 
their fundamental feature essentially similar to those of 
the dogfish. The forebrain is removed from a rabbit in 
which both labyrinths had been previously extirpated. 
Such an animal is able to raise itself into the chacteristic 
sitting position. When laid down flat on its side it first 
raises its head; then the asymmetrical position of the 
neck causes unequal changes in the tonus of the muscles 
of the legs in such a way that the front part of the body 
is brought into the sitting posture, and finally the hind 
limbs come into position. The whole chain of movements 
necessary to complete this reaction is inaugurated by the 
movement of the head. The head movement in its turn 
is excited, as Magnus has shown, by the unsymmetrically 
distributed contact stimuli, namely, the pressure of the 
skin of one side of the body upon the floor. For if a 
weighted board is placed upon the upper side of the trunk, REACTIONS OF NON-LABYRINTHINE ORIGIN 
57 
so as to apply contact stimuli to the upper as well as to 
the lower side of the body, the head is not lifted. The 
raising of the head is not interfered with by the presence 
of the board, which rests on the trunk only, but the excita- 
tion does not occur so long as the contact stimuli are 
approximately symmetrical on the two sides of the body. 
2. Reactions to Retinal Stimuli 
When a pigeon is rotated on a turntable, nystagmic 
movements of the head and of the eyes occur. If the 
table is turned to the right, the head goes to the left a 
certain distance and then comes back toward the midline 
with a jerk. These movements are repeated rhythmi- 
cally. The eyes make similar compensatory movements 
to the left, i.e., opposite to the turning of the body, and 
are quickly jerked back. These movements are also re- 
peated rhythmically and constitute a ty pical eye-nystag- 
mus. If, now, the table is suddenly stopped, the head and 
the eyes show an after reaction in a direction the reverse 
of that which occurred during the rotation; the slow 
movement is to the right and the quick return to the left. 
Ewald75 found that in pigeons, after the destruction 
of both labyrinths, nystagmus occurs during rotation, but 
no after-nystagmus follows the stopping of the table. 
He found, furthermore, that if a cylinder of gray paper is 
placed over the operated pigeon, so that the field of 
vision rotates with the animal, no nystagmus occurs dur- 
ing the rotation. When the labyrinthless pigeon is ro- 
tated with eyes open in the ordinary way a succession 
of images of the surrounding objects must pass across 
the retina. The effect of these is to cause the eyes to 
follow them for a certain distance, then the eyes come 58 
LABYRINTH AND EQUILIBRIUM 
back with a jerk, and the process is repeated over and 
over. When the cylinder is placed around the bird there 
is no longer the moving succession of images and, in the 
absence of the labyrinth, no nystagmus occurs. 
If a normal pigeon is covered with the gray cylinder 
and rotated it exhibits no nystagmus or practically none, 
during the rotation, but differs from the labyrinthless 
bird in that a marked after-nystagmus occurs when the 
rotation stops. These experiments show not only that 
compensatory motions can be called forth by the move- 
ment of images on the retina, but also that the retinal 
stimulation can modify the effects of the excitations aris- 
ing in the labyrinth. Ewald explained the influence of 
the retinal images on the compensatory movements and 
nystagmus during rotation thus: ‘ ‘ When the bird looks 
at objects which do not move along with it the labyrinth 
effect is increased; when it looks only at objects which 
rotate with it the effect of the labyrinth is weakened. 
In both cases there is the effort to retain for the time a 
constant visual field.” This does not explain, however, 
the very intense after-effect which occurs when the visual 
field is rotated along with the bird. 
A much clearer instance of the influence of moving 
retinal images upon the compensatory motions which are 
excited from the labyrinth has been described by Loeb.145 
He noticed that a horned lizard, Phrynosoma blainvillii, 
when held with its eyes toward a window in a moving car 
made slow movements of the head in a direction opposite 
to that of the train. The head was bent to a maximum 
and then came forward with a jerk. This was repeated 
regularly in response to the motion of the images of the REACTIONS OF NON-LABYRINTHINE ORIGIN 
59 
telegraph posts and other outside objects. A typical 
nystagmus was thus produced, but when the animal was 
turned around so that the objects outside the car could not 
be seen the nystagmus stopped at once. On the same 
principle a beautiful example of compensatory move- 
ments and nystagmus was obtained by rotating around 
the animal, which was kept at rest, an endless strip of 
paper on which were painted heavy vertical lines. 
Phrynosoma gives beautiful and characteristic com- 
pensatory motions when rotated on the turntable. More- 
over, the eyes can be caused to close by merely touching 
them with the finger, and they remain closed without any 
additional restraint for a time sufficiently long to permit 
the performance of the experiments described below. In 
this way Loeb was able to discriminate between the effect 
of the moving retinal images and the equilibrium reac- 
tions excited through the labyrinth. 
When a Phrynosoma with eyes closed was rotated 
slowly on a turntable very little compensatory movement 
of the head occurred during rotation, but when the turn- 
table was stopped a marked compensatory motion was 
produced. When the animal was rotated with the eyes 
open vigorous compensatory movements were made dur- 
ing the rotation but the after-effect was very slight. 
These and other observations enabled Loeb146 to reach 
the following conclusions: 
“When the eyes of the animal are closed we are deal- 
ing only with the geotropic effect of passive rotation; 
when the eyes are open the orienting influence of the mov- 
ing retinal image is added algebraically to the orienting 
effect of centrifugal force upon the ear. These two influ- 60 
LABYRINTH AND EQUILIBRIUM 
ences act in the same sense during rotation and therefore 
are additive; while after the rotation they act in the 
opposite sense to each other.” 
Trendelenburg and Kiihn233 working with another 
lizard, Lacerta agilis, were able to show the effect of mov- 
ing retinal images in exciting compensatory movements 
and nystagmus during rotation, but failed to find any 
after-effects from the retina. They obtained the same 
result also in the mud turtle, Emys lutaria. When one 
of these animals, in which the right labyrinth had been 
destroyed, was placed on the turntable and rotated to the 
right, no compensatory movement occurred during the 
rotation if the eyes were closed; but when the turning was 
suddenly stopped a compensatory movement followed. 
If the animal was rotated to the left with eyes closed 
compensatory movements occurred during the rotation, 
but the after-effect was absent. When such an animal 
was rotated to the right with the eyes open, compensatory 
movements occurred during the rotation and a compen- 
satory after-effect also occurred; rotation to the left with 
the eyes open caused compensatory movemefrfs dur-n5g 
the rotation but the after-effect was absent. 
A comparison of these results would suggest the fol- 
lowing conclusions: (1) Each labyrinth functions only 
for rotational movements in one direction; the compen- 
satory movements to the left during rotation to the right 
are excited from the right labyrinth only, and the after- 
effects (compensation to the right), are caused by the 
left labyrinth. (2) Compensatory movements during ro- 
tation are excited both through the eye and the ear. 
(3) The labyrinth gives rise to an after-effect when the 
rotation stops, but the retina does not. REACTIONS OF NON-LABYRINTHINE ORIGIN 
61 
The last of the above conclusions is hard to reconcile 
with the very marked after-effect seen in Phrynosoma. 
It is possible, however, that Trendelenburg and Kuhn 
could easily have overlooked a retinal after-effect for the 
reason that the after-effect of retinal stimulation is in the 
same direction as the compensation during rotation, and 
would only be perceived as a prolongation of the com- 
pensatory position for a short time after the rota- 
tion ceased. 
Many other examples of equilibrium reactions from 
retinal stimulation might be given but the above will serve 
to indicate the need to discriminate between retinal and 
labyrinthine effects in research on the functions of the 
inner ear. 
3. Reflexes from Muscles and Joints 
Another sort of compensatory movement which can 
complicate the investigation of the equilibrium reactions, 
was described by Lyon.150 In his account he states: 
“It occurred to me that bending the body might have 
some effect upon compensatory motions. I therefore 
held the head [of a dogfish] (and consequently the semi- 
circular canals which are supposed to be dynamically 
stimulated), and bent the tail to one side. The eyes 
turned as promptly as compass needles. The same day 
Mr. Garrey pointed out to me that a normal dogfish lying 
bent and at rest on the bottom of the aquarium always 
held the two eyes differently. Upon the convex side of 
the animal the white was more visible in front; on the 
concave side behind.” 
When the tail is bent to the right, so that the body is 
concave to the right, the two eyes make a conjugate move- 62 
LABYRINTH AND EQUILIBRIUM 
ment to the left. This position is retained so long as 
the bending continues. The reaction takes place just the 
same after both optic and both auditory nerves have 
been cut. An analogous observation had been made by 
Ewald on the dog. The dog is tied on the table with the 
head left free. If one now bends the head strongly to 
the left and holds it there one feels the effort made by the 
dog to turn the head back to the normal position and one 
sees at the same time that the eyes are turned strongly 
to the right. As soon, however, as the dog ceases the at- 
tempt to overcome the forced position, the eyes come back 
to the primary position or at least are moved about freely. 
If this statement is wholly correct the reaction of the 
dog differs from that of the fish in that, in the latter, the 
forced position of the eyes is maintained during the whole 
time of the bending, while in the former it occurs only 
while voluntary efforts are made to bring the head back 
to the normal position. 
A reaction like that of the dogfish is also seen in the 
rabbit. This was discovered by Barany,14 who apparently 
did not know of Lyon’s observations. If the head of a 
rabbit is fixed in a holder so that no motion of the laby- 
rinth can occur to give rise to a reflex, turning the body to 
one side until the head and body make an angle of 90 
degrees with each other, causes a definite conjugate devi- 
ation of the eyes to the opposite side. When the body 
is bent to the right the eyes go to the left, i.e., the right 
eye turns forward toward the nose, the left eye backward 
toward the ear. During the bending the eyes move to a 
point of extreme deviation, then jerk back toward the 
primary position, again move to extreme deviation and REACTIONS OF NON-LABYRINTHINE ORIGIN 
63 
jerk back. This is repeated usually about two or three 
times in the turning of the body to an angle of 90 degrees. 
It thus constitutes a characteristic nystagmus with the 
slow movement in the direction opposite to the turning. 
If the body is held at an angle the eyes remain in a forced 
position. This reaction of the rabbit differs from that 
of the dogfish only in the occurrence of the nystagmic 
movements. Of course if the body is fixed and the head 
is moved to one side the same thing happens, but in that 
case the labyrinths are also affected by the change of 
position. This reaction can also be obtained in a rabbit 
in which both labyrinths have been extirpated. If the 
body is placed at an angle to the head in some other direc- 
tion than the horizontal, compensatory eye movements 
take place in a different plane. All of these compensa- 
tory movements are of such nature and direction that they 
would correspond to and reenforce the reflexes from the 
labyrinth in the normal activities of the organism. 
De Kleijn111 confirmed the existence of these reactions 
in rabbits with both labyrinths destroyed. When in such 
rabbits he sectioned the dorsal roots of the first and sec- 
ond cervical nerves the reaction could no longer be ob- 
tained. This proves that the eye movements in question 
are excited through afferent impulses from the neck re- 
gion, presumably through the effects of changes of pres- 
sure or tension upon the nerve endings. 
It must be remembered that the impulses arising in 
the neck region affect the tonus of the muscles of the 
limbs. When, for example, a normal rabbit is laid upon 
its side, the geotropic impulses from the labyrinth tend 
to cause the head to be brought up into a position of 64 
LABYRINTH AND EQUILIBRIUM 
symmetry with reference to the vertical. At the same time 
contact stimuli from the skin of the side on which the 
body rests, tend also to cause the head to be lifted. When 
the head then changes its position in relation to the trunk, 
tonus changes are produced in the muscles of the limbs 
and these cooperate to bring the whole animal into the 
normal relation to the vertical. We owe to Magnus and 
his co-workers a wealth of experimental detail in this field. CHAPTER VI 
EXPERIMENTS ON THE SEMICIRCULAR 
CANALS 
The separate functions of the ampullae and of the 
otolith-organs can be investigated only by methods which 
make it possible to throw either of the two sets of struc- 
tures out of activity without injury to the other. The 
hypothesis of Breuer which assigns all the dynamic func- 
tions to the semicircular canals and all the static functions 
to the otoliths can be put to the test of experiment only 
in this way. 
Extirpation experiments are conclusive if, on destruc- 
tion of a particular part, a particular function is definitely 
lost. If, on the other hand, the function continues after 
extirpation of the part, two possibilities remain; either 
the function was not performed by the part destroyed, or 
it was performed by more than one structure. We have 
already seen that the latter condition exists so far as the 
general functions of equilibrium are concerned; that, in 
fact, equilibrium reactions can occur through the influence 
of contact, retinal, and labyrinthine stimuli. It is neces- 
sary then to proceed by the method of exclusion in the 
use of the extirpation method and to confirm the findings 
by stimulation experiments. In the statement of the 
results of these investigations it will be more convenient 
to describe first the effects of stimulation. 
65 66 
LABYRINTH AND EQUILIBRIUM 
1. Stimulation Experiments on the Semicircular 
Canals 
The older experimenters speak of stimulation in so 
loose a manner that a few introductory remarks seem 
necessary. Everyone who is interested in the problems 
of the labyrinth knows that the sensory endings concerned 
are not distributed along the extent of the semicircular 
canals but are definitely localized in the cristae of the 
ampullae. When we speak of the stimulation of a canal 
or of an ampulla we must be understood to mean the 
stimulation of the sensory endings in the crista. It is 
not unusual for writers to speak of stimulation of a canal 
by rotation of the body (or of the head) in the plane of 
that canal, although it is not possible under the circum- 
stances, to say that no other part of the labyrinth has been 
stimulated as a result of the movement. 
Flourens81 described the effects of cutting the various 
canals and stated that injury to a canal caused movements 
in the plane of that canal. Cyon62 first set out to investi- 
gate the effect of stimulating each canal individually, but 
his statements show that he considered the cutting of a 
canal as the equivalent of the stimulation of its ampulla. 
He failed to discriminate between the results of stimula- 
tion and destruction. 
Breuer46 was the first to describe with approximate 
accuracy the effects of stimulation of the individual am- 
pullae in the pigeon. Electrical stimulation uniformly 
caused movement in the plane of the canal. The direction 
of the movement is not always stated with clearness. 
Mechanical stimulation of the ampullae gave more definite 
results. Pressure on the ampulla of a horiontal canal 
always caused the head to be turned to the opposite side. EXPERIMENTS ON SEMICIRCULAR CANALS 
67 
On the whole, Breuer’s stimulation experiments were a 
very important contribution to the investigation of the 
physiology of the labyrinth. 
Ewald75 by his very ingenious application of the pneu- 
matic hammer to the mechanical stimulation of the single 
canals confirmed the observation that stimulation of an 
ampulla causes movement determined by the plane of 
the canal, or more correctly, that each ampulla causes 
movement in one definite plane. The additional deduc- 
tions from his experiments, that endolymph currents in 
the canals are the cause of the excitation, and that move- 
ment of the endolymph in the one direction causes stimu- 
lation and in the opposite direction inhibition, are open 
to criticism. 
Before describing in detail the experimental work on 
the ears of selachians, which are the best animals for this 
purpose, it will be desirable to review briefly the anatomi- 
cal arrangements. The statement is generalized and 
omits the minuter details in which the different orders 
are more or less unlike in particulars which have no 
apparent physiological significance. 
The membranous labyrinth (Fig. 4) lies in, but by no 
means fills, a roomy cavity in the skull cartilage, and 
hence is surrounded by a relatively large quantity of 
perilymph. The largest portion is the sacculus, S; it 
rests upon the bottom of the vestibular space, and is 
larger in the posterior part. The sacculus has openings 
communicating with the utriculus, the recessus utriculi, 
and the posterior semicircular canal, respectively, while 
the lagena may be considered as a small recess from its 
posterior, ventral portion. The utriculus, U, is a some- 68 
LABYRINTH AND EQUILIBRIUM 
what cylindrical, rather wide tube which extends upward, 
backward, and a little inward from the place of entrance 
of the anterior vertical and the horizontal canals. It 
lies upon the recessus utriculi and the sacculus, opening 
into the former by a short, tubular connection, and into 
the latter by a long, narrow slit. The utriculus receives, 
at its anterior end, the mouth of the anterior vertical 
Fig. 4.—Generalized diagram of membranous labyrinth of a Selachian: A, anterior vertical canal; 
P, posterior vertical canal; H, horizontal canal; aa, pa, ha, the ampullae of the anterior vertical, 
posterior vertical and the horizontal canals respectively; U, utriculus; S, sacculus; R, recessns 
utriculi; MR, macula of the recessus; MS, macula of the sacculus; ML, macula of the lagena 
N, eighth nerve sending branches to the maculae and cristae. 
canal, and just external to this, the mouth of the hori- 
zontal canal. Its upper, posterior end corresponds to the 
sinus superior of other forms, and receives the posterior 
openings of the anterior vertical and the horizontal 
canals; it has no direct communication with the posterior 
vertical canal. The recessus utriculi, R, lies below the 
anterior end of the utriculus. Besides the tubular com- 
munication with the utriculus it also has an opening back- 
ward into the anterior end of the sacculus. EXPERIMENTS ON SEMICIRCULAR CANALS 
69 
The three semicircular canals stand approximately, 
but by no means exactly, at right angles with each other. 
The horizontal, or external, canal, H, is nearly hori- 
zontal in its middle part, but its anterior end bends some- 
what downward and its posterior part bends strongly 
upward. The ampulla, ha, of this canal is near its ante- 
rior end; it opens into the utriculus by a short and rela- 
tively narrow tube. The ampulla, aa, of the anterior 
vertical canal lies median to and very near the ampulla 
of the horizontal canal. The anterior vertical canal lies 
in nearly one plane, at an angle of 35 to 40 degrees with 
the median plane of the body. The posterior vertical 
canal, P, forms a ring which has no communication with 
the rest of the membranous labyrinth except a tubular 
connection with the saeculus. Its ampulla, pa, is in its 
lower, outer portion. 
The branches of the eighth nerve are distributed as 
follows: to each of the three ampullae, to the macula of 
the recessus utriculi, to the maculae of the saeculus and the 
lagena, and finally, to the macula neglecta in the wall of 
the connection between the posterior vertical canal and 
the saeculus. 
The macula, MR, of the recessus utriculi is in a 
rounded or somewhat oval depression containing the 
characteristic hair cells, on which rests the lenticular or 
saucer-shaped otolith of the recessus. The macula, MS, 
of the saeculus is much more extensive, and that of the 
lagena, ML, is practically continuous with it. The otolith 
of the saeculus and lagena is an elongated, flattened mass, 
very much larger than that of the recessus utriculi. The 
otoliths consist of calcareous material of a pasty con- 
sistency, and can be readily broken up to form a milky 70 
LABYRINTH AND EQUILIBRIUM 
suspension in the ear lymph. The macula neglecta (not 
shown in the figure) has no otolith. 
The cristae of the ampullae have hair cells which are not 
very different in appearance or arrangement from those 
of the maculae. Instead of an otolith, however, there 
rests on each crista a somewhat fibrous appearing gela- 
tinous mass, the cupula, into which the hair cells seem to 
extend for a short distance. The existence of the cupula 
seems to be ignored by many writers who speak as if the 
hair-cells wave freely in the endolymph. 
Stimulation experiments on the ampullae of the dogfish 
ear have been described by Lee,136* 137 Kubo,130 and the 
writer.169 Lee’s account is very closely in accordance 
with the facts. Kubo used a number of other selachians 
besides the dogfish. He failed to corroborate Lee in 
various particulars, but his own work is full of blunders 
and contradictions. 
The ampullae of the dogfish ear are extremely sensitive 
to mechanical stimulation. Clear results may also be 
obtained by electrical stimulation, but the presence of 
liquids of high conductivity introduces considerable tech- 
nical difficulty. If the cartilage is carefully sliced away 
until the ampulla is exposed, the application of light 
pressure by means of a bristle gives prompt and definite 
results. Mechanical stimulation may also be obtained by 
pressing upon the cartilage before the ampulla is quite 
exposed. If the exposed canal is seized with the forceps 
and very gently pulled upon the same result is obtained. 
Experience in these procedures impresses one with the 
great sensitivity of the ampulla to mechanical stimulation. 
Stimulation of the ampulla of a horizontal canal 
causes a prompt and definite movement of the eyes to the EXPERIMENTS ON SEMICIRCULAR CANALS 
71 
opposite side. If the right horizontal ampulla is stimu- 
lated, both eyes look to the left; or, since the two eyes 
cannot receive images of the same object at the same time, 
it would be more exact to say that the two eyes move in 
a horizontal plane, the right eye going forward toward 
the nose, the left eye backward toward the gill. The 
dorsal fins at the same time bend to the left. These it will 
be remembered are exactly the compensatory movements 
which are made when the dogfish is rotated to the right 
around the dorsoventral axis. They are also the eye 
and fin movements which occur when the fish in swimming 
turns to the left. Stimulation of the left horizontal am- 
pulla causes the eyes and dorsal fins to turn to the right, 
the compensatory motions which are produced by rota- 
tion to the left in the horizontal plane. 
When the ampulla of the right anterior vertical canal 
is stimulated the right eye is elevated, so that more white 
shows below the iris, the left eye is depressed, and both 
eyes roll backward on their axes; the right pectoral fin 
is depressed and the left pectoral is elevated. These are 
the movements which occur when the animal is turned 
head downward to the right in the plane of the anterior 
vertical canal. When the ampulla of the left anterior 
vertical canal is stimulated, the eye and fin movements 
are the same as those which occur when the head is turned 
downward and to the left, in the plane of the left anterior 
vertical canal. 
When the ampulla of the right posterior vertical canal 
is stimulated, the right eye goes up and the left eye goes 
down, as in the case of stimulation of the right anterior 
vertical ampulla, but both eyes roll forward on their axes. 
The right pectoral fin turns strongly downward and the 72 
LABYRINTH AND EQUILIBRIUM 
left pectoral slightly upward. These are the reactions 
which occur when the animal is rotated tail downward and 
to the right. If the left posterior vertical ampulla is 
stimulated the reaction may be described by reversing 
the use of the words “right” and “left” in the preceding 
part of this paragraph. 
It is seen from the foregoing that the statements of 
Flourens, von Cyon, and others among the older investi- 
gators that stimulation of an ampulla causes movements 
in the plane of its canal, were well founded. The state- 
ment, to be accurate, however, should be modified to say 
that stimulation of an ampulla causes the same move- 
ments which are produced by rotation of the animal in 
the plane of the canal. 
Since rotation in the plane of any one of the four verti- 
cal canals must be around an oblique axis, or, what is the 
same thing, simultaneous rotations around two of the 
axes of reference, it is of interest to note the effect of 
simultaneous stimulation of two vertical canals. Lee 138 
did this and found that the reaction is the resultant 
which could have been inferred from the effects of 
excitation of the two ampullae separately. Thus stimu- 
lation of both the right vertical ampullae at the same time 
causes elevation of the right eye and depression of the 
left eye; but stimulation of each of these ampullae sepa- 
rately causes this movement, and at the same time a roll- 
ing movement which, for each of the two ampullae, is in 
opposite directions. It might then be expected that when 
the two are stimulated simultaneously the rolling motion 
would be absent, and this is just what happens. The sim- 
ultaneous stimulation of the two right vertical ampullae 
gives the same reaction as that which is produced by EXPERIMENTS ON SEMICIRCULAR CANALS 
73 
rotation to the right around the longitudinal body axis. 
A comparison of the effects of stimulation of the indi- 
vidual ampullae and the results of rotations around the 
different body axes leads to the conclusion that the am- 
pullae contain mechanisms which can give rise to all the 
compensatory movements ; but we can not conclude from 
this that no other mechanism exists in the ear for the 
production of these movements. It is necessary first 
to know what happens in the absence of the ampullae. 
2. Extirpation of the Ampullae 
Many of the older investigators appear to have made 
the assumption that cutting a semicircular canal was the 
physiological equivalent of the destruction of the canal 
with its ampulla. It may be stated at once with certainty 
that this is not the case. In the higher vertebrates the 
destruction of the ampullae without injury to other parts 
of the labyrinth is so difficult while in the fish it is so com- 
paratively easy that we are justified in confining our 
attention to the results obtained through experiments 
on fishes. 
Lee137 destroyed the ampullae or sectioned the ampul- 
lar branches of the eighth nerve in the dogfish. As the 
outcome of his experiments he arrived at the conclusion 
that “the section of the nerves of all six canals causes, 
so far as has been observed, effects similar to those of 
section of both acoustics, viz., the eyes and fins are nor- 
mal in position; the fish swims on his belly, back or side, 
and comes to rest in any one of these positions; after 
settling on his back or side, he apparently tries to return 
to his normal position but finds it difficult or impossible 
to do so; compensation is wanting in all movements.” 74 
LABYRINTH AND EQUILIBRIUM 
Lyon149, 150 destroyed all the ampullae or cut their 
nerves in the dogfish and in flounders and saw, contrary to 
the results of Lee, the persistence of compensatory move- 
ments. According to Lyon, compensatory movements 
are retained for rotations in all planes after loss of all 
the ampullae. 
Lee and Lyon each speak of destruction of the am- 
pullae, but both seem to have relied mainly on section of 
the nerve branches. By section of the nerve branches, 
however, they arrived at exactly opposite and funda- 
mentally contradictory results. 
After considerable practice I have developed a special 
technique by which the ampullae of any or all of the canals 
may be removed with a minimum of injury and shock to 
the animal and with results which admit of no uncertainty. 
A flap of skin is loosened and turned back exposing the 
appropriate portion of the skull. A thin surface layer 
of the skull is sliced off with the attachment of some of 
the neck musculature, thus making visible the parts of the 
labyrinth through the transparent cranial cartilage. The 
membranous canal is exposed at a distance not too great 
from its ampullar enlargement. With a fine pointed pair 
of curved forceps the membranous canal is grasped as 
closely as possible to the ampulla and the canal with its 
ampulla is extracted by a sudden movement, a light quick 
jerk. Success in this operation depends mainly upon the 
choice of forceps with the proper curve which bite at the 
very point, and upon acquiring the knack of removal of 
the canal by a suitable movement. A too sudden pull 
will usually break off the canal external to the ampulla, 
and too slow a movement frequently drags and injures 
portions of the vestibular structures which it is desired EXPERIMENTS ON SEMICIRCULAR CANALS 
75 
to leave unharmed. When one has once acquired the 
knack of this operation the results become absolutely 
clear. The ampullas can be extracted one after another 
with certainty and exactness. In sectioning the nerves 
one may cut too much or too little; the fibre bundles are 
scattered, and certainty is impossible. The attempted 
destruction of the ampullae in situ cannot by any means 
have the exactness of their complete removal. In many 
of my earlier experiments I had the ampullae pasted on a 
blank leaf of my note book when I wrote down on the 
same page the results of their extirpation. Under these 
conditions there can be no doubt as to the correctness 
of the results. In the summer of 1919, I repeated and 
extended these experiments at the Marine Biological Lab- 
oratory, and on account of the contradictions of previous 
workers I took occasion to have the experiments wit- 
nessed by a number of physiologists and zoologists. 
I previously had found169 that removal of the ampullae 
of the four vertical canals had little or no effect on the 
compensatory eye movements resulting from the rotation 
around the longitudinal and transverse axes. In order, 
however, that there could remain no possible functioning 
of the semicircular canals I have, in a long series of ani- 
mals, removed all six ampullae with uniform results. 
A dogfish from which all six ampullae have been re- 
moved shows definitely the following reactions. (1) Com- 
pensatory movements of the eyes and fins occur on rota- 
tion around a longitudinal axis; e.g., on rotation to the 
right, the right eye goes up and the left eye goes down. 
This position of the eyes is retained as long as the abnor- 
mal body position is continued. (2) Compensatory 
movements of eyes and fins occur on rotation around the 76 
LABYRINTH AND EQUILIBRIUM 
transverse axis; e.g., when the animal is tilted head down- 
ward the eyes make the characteristic wheel-like backward 
rotation. (3) Compensation is absent on rotation 
around the dorsoventral axis. (4) The animal swims in 
a manner differing but little from the normal. (5) The 
righting reaction takes place promptly and vigorously; 
if the animal is placed belly up in water it turns over 
at once. 
As a sample experiment I quote verbatim the follow- 
ing from my notes. 
“July 14, 1919. Dogfish 5. 10:00 a.m. All six ampullae removed. 
Compensatory movements prompt on rotation around longitudinal and 
transverse axes; none on rotation in horizontal plane. Animal rights itself 
perfectly in water. Eyelids sewed together to exclude retinal stimuli, 
and animal put into deep tank; righting perfect. 
2:00 p.m. Animal rather weak but rights itself promptly when turned 
over in water; swims rather wobbly; turned completely over once when 
excited by other dogfish; I have seen a normal dogfish do this under 
similar circumstances. 
July 15, 9:00 a.m. Animal very weak; rests on bottom of tank in 
normal position. Rights itself but may swim one or two turns belly up 
before getting over. Opened stitches in eyelids. No compensatory move- 
ments of eyes. 
July 16, 9:30 A.M. Animal moribund. Killed for autopsy. Considerable 
blood clot in each vestibule.” 
The above experiment shows a possible source of the 
confusion in the reports of previous investigators. Had 
I assumed that on account of shock effects, observations 
made on the day of operation would be unreliable, and 
had I waited until the following day to make my observa- 
tions, it would have appeared that loss of the ampullae 
abolishes compensatory movements, which is manifestly 
not true. When immediately following the destruction 
of an organ a function is clearly retained, it is indisput- EXPERIMENTS ON SEMICIRCULAR CANALS 
77 
able proof that at least that organ is not the only one 
which can perform the function. Observation made on 
July 15, on Dogfish 5, might have favored the statement 
that destruction of the ampullae of the semicircular canals 
abolishes compensatory movements of the eyes, but the 
observations of July 14 clearly show such a conclusion 
to be wrong. 
In the attempts to determine the role of the various 
sense organs in the geotropic reactions of the dogfish, 
it has long been recognized that retinal stimuli play a 
part. Lyon149 excluded visual stimuli by section of the 
optic nerve. I accomplished the same result by the less 
radical operation of sewing the eyelids together, when 
equilibrium and the righting reactions were under con- 
sideration, and by placing a black, opaque disk on the 
cornea over the region of the pupil when eye movements 
were to be studied. Other methods of blinding were also 
used. I can affirm with complete assurance that the 
compensatory motions described in the case of animals 
from which all the ampullae have been removed occur also 
when activity of the retina has been excluded. 
It has been noted that the dogfish, like most animals 
which rest on the bottom and are not merely suspended 
in the water, manifests very strong contact reactions. 
A vigorous specimen which has been blinded and which 
has had as far as possible all the end organs of the eighth 
nerve destroyed will almost always be found belly down 
when at rest. Such a fish may swim indifferently back or 
belly up, but when it comes to rest the position is a fair 
index of the general state of the animal. When an inves- 
tigator affirms that his specimen came to rest indifferently 
in any position, he has given good incidental evidence as 78 
LABYRINTH AND EQUILIBRIUM 
to the animal’s physical condition. In stating that a 
dogfish deprived of its six ampulla? makes normal right- 
ing reactions I have not been unmindful of these facts, 
but have taken care to exclude the possibility of con- 
tact stimuli. 
Although it can be proved that after the loss of all 
the ampullae, with exclusion at the same time of retinal 
and contact stimuli, the dogfish makes normal compensa- 
tory movements of the eyes and fins to rotations in all 
vertical planes, it is necessary to note that there are some 
differences between this and a normal animal. 
The following seem to be fairly constant results: 
(1) The compensatory movements of the eyes, though 
prompt, are noticeably slower than in the uninjured ani- 
mal. Compensatory movements due to visual stimuli 
alone are so much slower, requiring several seconds or 
even minutes, that no difficulty is experienced in distin- 
guishing these from reflexes of labyrinthine origin. 
(2) If seized while in the water the animal strongly re- 
sists the attempt to turn it back downward. One feels, 
however, that the resistance is neither so prompt nor so 
strong as in a normal animal. (3) In swimming there is 
more or less evident a slight tendency to sway from side 
to side around the longitudinal axis, like a boat insuffi- 
ciently ballasted. 
These three conditions are less noticeable in vigorous 
specimens; they become very marked in weakened indi- 
viduals. They can perhaps all be accounted for by a 
general lowering of muscle tonus. It is important to note 
that, as I shall show later, precisely the same complex 
of conditions can be brought about through a totally dif- 
ferent operation. EXPERIMENTS ON SEMICIRCULAR CANALS 
79 
It may be added for the sake of completeness that the 
compensatory movements which remain after removal 
of all the ampullae are in the blinded animal completely 
abolished by destruction of the remaining parts of the 
labyrinth if contact stimuli are excluded. 
The foregoing statements apply to the results of the 
removal of all the ampullae; it is necessary also to note 
the effect of destruction of the three ampullae of one ear. 
It has been stated by Lee and others that the effect of this 
operation is practically the same as that of total destruc- 
tion of one labyrinth or section of one eighth nerve. The 
animal swims about making turns either to the right or 
to the left, and does not seem to be greatly inconvenienced. 
There is a very noticeable forced position of the body, 
a curving to the operated side, and also a forced position 
of the eyes and fins; the animal swims with the body in- 
clined to the operated side. If the ampullae have been 
removed from the right ear, the right eye is depressed 
and the left eye is elevated, while the right paired fins are 
elevated and the left are depressed. The animal makes 
good compensatory movements to rotations in both direc- 
tions around the longitudinal and transverse axes. When 
the fish is rotated around the dorsoventral axis to the 
sound side, the normal compensatory motion occurs, the 
two eyes go to the operated side; when, on the contrary, 
the rotation is to the operated side no compensatory 
movement follows. 
Since, as we have seen, the compensatory movements 
which are excited by rotation in the horizontal plane are 
the only ones lost after removal of all the ampullae, and 
since stimulation of the horizontal ampullae causes just 
these movements, it is of importance to note the effect 80 
LABYRINTH AND EQUILIBRIUM 
of destruction of the horizontal ampullae alone. When 
only one horizontal ampulla has been removed rotation 
to the operated side has no noticeable effect, but rotation 
to the sound side gives the normal compensatory move- 
ment. I have repeated this observation a very great 
number of times, because it has, as we shall see, an im- 
portant bearing on the question of the mechanism of 
normal excitation. 
It is possible that the effect of destruction of the hori- 
zontal ampulla is not the same in all vertebrates. Ewald 
found that after complete destruction of one labyrinth 
of the pigeon compensatory motions are still made to ro- 
tations in both directions. Dreyfuss72 states that the 
same is true of the guineapig, although he describes in 
the same paper the following interesting experiment: 
Three guineapigs, one of them normal, one with the right 
labyrinth destroyed, and one with both labyrinths de- 
stroyed, are placed in a cage on a turntable and supplied 
with food. If, while they are all quietly feeding, the 
table is rotated in either direction, the normal guineapig 
ceases feeding at once, but the one with both labyrinths 
extirpated continues eating and pays no attention to 
the rotation. The one with the right labyrinth removed 
continues to eat when rotated to the right but ceases at 
once when rotation to the left begins. 
In view of the clear results which one gets with the 
dogfish, it seems possible that the feeding experiment of 
Dreyfuss indicates the real labyrinthine effect, and that 
the nystagmus which he observed on rotation to the 
operated side was a retinal reaction. Trendelenburg and 
Kiihn233 found in the lizard, snake, and turtle, after de- 
struction of one labyrinth, normal compensatory move- EXPERIMENTS ON SEMICIRCULAR CANALS 
81 
ments on rotation to the sound side, but no reaction on 
rotation to the operated side if retinal effects were ex- 
cluded. Ewald’s and Dreyfuss’ experiments ought to 
be repeated. 
All the evidence seems to show that reaction to rota- 
tion in the horizontal plane is the exclusive function of 
the horizontal ampullae, and that, clearly in the dogfish, 
and apparently in many other forms, each ampulla func- 
tions only for rotations to its own side, i.e., the right hori- 
zontal ampulla responds only to a turning to the right 
and the left horizontal ampulla to a turning to the left. 
A comparison of the results of stimulation and extir- 
pation experiments on the ampullae of the semicircular 
canals in the dogfish leads to the following conclusions: 
(1) All the compensatory movements can be produced 
through the excitation of the ampullae. (2) All the com- 
pensatory movements except those in response to rota- 
tion in the horizontal plane can, in the absence of the 
ampullae, be brought about through the action of some 
other part of the labyrinth. CHAPTER VII 
EXPERIMENTS ON THE OTOLITHS 
The semicircular canals are found only in vertebrates 
and nothing closely analogous to them occurs in any of 
the invertebrates. The otolith-organ, on the contrary, 
is possessed by very many and widely separated orders 
of invertebrates. A typical otolith-organ consists of a 
cavity, the otocyst, some part of which is lined with hair- 
cells, corresponding to the macula of the vertebrate ear, 
and containing otoliths, or ear sand, resting upon the 
hair-cells. The otoliths in most animals are deposits or 
concretions of calcareous matter precipitated from the 
body fluids; but in certain Crustacea, the macruran deca- 
pods, the cavity is open to the exterior and the otoliths 
consists of grains of sand which the animal picks up with 
its forceps and places in the cavity. In many other in- 
vertebrates, of which the brachyuran decapods are ex- 
amples, well depeloped otocysts occur which contain no 
otolithic material. 
The experiments of Delage,71 Kreidl,127 Verworn,230 
and others have proved that the invertebrate otocyst pos- 
sesses, at least in many instances, distinct equilibrial 
functions. When we put a crab or a crayfish on its back 
it promptly rights itself. This could be, of course, purely 
a contact reaction, but the same thing happens if the 
animal is swimming out of reach of solids. If we destroy 
the otocysts in one of these animals it still rights itself 
but less accurately and promptly than before; and if, 
in addition, the eyes are covered with asphalt varnish so EXPERIMENTS ON SEMICIRCULAR CANALS 
83 
as to exclude retinal stimulation complete disorientation 
occurs in swimming. 
If the crab or crayfish is moved out of its normal 
relation to the vertical, e.g., if it is turned a few degrees 
around its longitudinal body axis, the eyestalks make a 
compensatory movement as if to retain their original or 
usual position in space. If the animal is held in the new 
position the compensatory position of the eyestalks is 
maintained.. This reaction occurs also in a specimen 
which has been blinded by painting the eyes with black 
varnish but it disappears when, in addition, the otocysts 
are removed. These experiments are often taken to 
support the hypothesis of Breuer that in the vertebrate 
ear the maculae with their otoliths are the organs for the 
static reactions of the labyrinth, while the dynamic func- 
tions are performed by the semicircular canals only. 
This reasoning is faulty, because the reaction of the in- 
vertebrate is both dynamic and static; a compensatory 
movement occurs during the rotation of the animal (dyna- 
mic function), and the new pose of the eyestalks is re- 
tained so long as the animal is kept in the forced position 
(static function). it is hard to conceive of an 
organ having static functions without having at the same 
time dynamic functions, although the reverse is quite 
possible. 
The analogy between the otocysts of the invertebrates 
and the otolith-organ of the vertebrate ear loses force 
also from the fact, brought out by the work of Clark61 
that the otocysts of Gelasimus and Platyonichus, which are 
without otoliths, seem to possess the same static functions 
as the otocysts of other macrurans do in which an otolith 
is present. It is plain that we cannot, by experiments 84 
LABYRINTH AND EQUILIBRIUM 
on the otocysts of invertebrates, arrive at definite con- 
clusions in regard to the functions of the otoliths of 
vertebrates. 
Experiments on the otoliths of the vertebrate ear 
are much more difficult than experiments on the ampullae. 
It is indeed a very simple matter to expose and stimulate 
or remove the ampullae with practically no harm to the 
otoliths; but even in fishes, removal of the otoliths without 
injury to the connections essential to the functions of 
the ampullae is far from easy, and in the higher verte- 
brates it was wholly impossible until Magnus and de Kleijn 
were able very recently to apply the centrifugalization 
method of Wittmaack which will be discussed later. 
1. Extirpation of the Otoliths 
Loeb,144 removed the otoliths from the ear of the 
dogfish both by scratching them out and by washing 
them out with a stream of water from a fine pipette. 
By the former method he obtained results comparable to 
those which follow section of the eighth nerve. When 
he used the latter method his experiments were a success, 
for compensatory motions were not lost. Kreidl92 re- 
peated these experiments. ' He stated that dogfish from 
which the otoliths of both ears had been removed often 
swam belly up; they came to rest indifferently in any 
position on the bottom of the aquarium and allowed them- 
selves to be turned into any orientation in the water. 
The effects of removal of the otoliths of the dogfish 
ear were also described by Lee.137 According to his 
description no forced position of eyes or fins resulted 
from the loss of all the otoliths. If the fish was turned 
upon its back, it remained quietly in that attitude, or EXPERIMENTS ON THE OTOLITHS 
85 
swam off, gradually turning over; it often swam upon its 
side; in coming to rest it often settled upon its back. 
The compensatory movements were weakened but not 
abolished; the compensatory position was not retained 
after the cessation of the movement. Removal of the 
otoliths from one ear caused all the abnormalities which 
follow section of one eighth nerve. 
Kubo130 described experiments on the single otoliths. 
He stated that after the removal of the saccular otolith 
on one side the rolling movement of the eyes became very 
indefinite for the position head upward but was unaffected 
in the position head downward. From this he inferred 
that, in the head upward position the saccular otolith slid- 
ing backward on account of its weight, gives the stimulus 
which causes the eyes to roll forward on their axes. 
When, however, he removed the utricular otolith on one 
side, the reactions to rotations around the transverse axis, 
that is, in both the head up and the head down position, 
were absent or very indefinite. The significance of this 
observation was altogether overlooked. All of Kubo’s 
results appear to have been colored by his anticipations. 
The inaccuracy of the whole performance is well in- 
stanced by his statement that after removal of both oto- 
liths on one side, no reaction occurred to rotation around 
the dorsoventral axis to the operated side, but a normal 
reaction took place when the turning was to the sound 
side. These reactions do not depend upon the otoliths 
at all but on the ampullae of the horizontal canals. 
It appears to the writer that the work of all previous 
experimenters on the otoliths has been vitiated by the 
failure to realize the importance of an avoidance of in- 
jury, not merely to the ampullae, but to the vestibular con- 86 
LABYRINTH AND EQUILIBRIUM 
nections of the ampullae. On the other hand the im- 
portance of experiments on the otoliths in animals in 
which all the ampullae have been extirpated, has not been 
appreciated. The need of these precautions was kept in 
mind in the performance of the experiments about to 
be described.171 
In the dogfish the otoliths are of soft, friable, calcare- 
ous material. In the sacculus there is a large otolith 
spread over the main macula acustica and a smaller mass 
on the lagena. These are so situated that their removal 
can be accomplished with little injury and the operation 
is relatively easy. For the otolith of the utriculus the 
case is very different. This otolith lies in the recessus 
utriculi so close to the openings of the ampullae of the 
anterior vertical and the horizontal canals that it requires 
some skill and much practice to remove it without injury 
to the ampullae. If, however, after opening the vestibule 
by removing a portion of the cartilaginous roof, the 
utricular wall is slit open with a very sharp microdissec- 
tion knife, the otolith material may be washed out by the 
careful use of a fine pointed pipette. In a similar way 
the saccule may be slit open and its otoliths removed. 
No operation was considered successful unless it was 
found at postmortem examination that no otolith material 
remained. For reasons to be stated in another chapter it 
was considered important not only to avoid injury of 
the ampullaB but also to reduce the injury of the utriculus 
to a minimum. 
After removal of all the otoliths from both ears in 
successful cases the following results are seen: (1) Com- 
pensatory movements of the eyes are made in the regular 
way to rotations about all three body axes, longitudinal, EXPERIMENTS ON THE OTOLITHS 
87 
transverse, and dorsoventral. If the animal is rotated 
around a longitudinal or transverse axis and held in the 
abnormal position the compensatory position of the eyes 
is retained, but when the rotation is around the dorso- 
ventral axis the eyes make the compensatory movement 
and then return to the primary position. These move- 
ments appear to differ from those in the normal animal 
only in being slightly slower. (2) The animal swims in 
normal orientation and maintains its equilibrium in the 
water, but its swimming, like that of the fish without 
ampullaB, is likely to be accompanied by a rocking move- 
ment ; this rocking or swaying is less apparent in vigorous 
specimens. (3) If turned belly up in the water, the fish 
rights itself promptly; in doing so, however, it sometimes 
overcompensates and turns almost or completely over. 
It will be seen that these results are strikingly similar 
to those produced by loss of the ampullae. It is especially 
noticeable that there is the same apparent slight slowing 
of the reactions and the same indication of lowering of 
muscle tonus in general. In one important respect, how- 
ever, the result of this operation differs from that of 
removal of the ampullae, namely, the compensatory move- 
ment to rotation about the dorsoventral axis still occurs. 
In these observations due care was taken to eliminate 
retinal and contact reactions. 
Parker191 removed the saccular otolith by way of an 
opening in the roof of the mouth. He found that the loss 
of this otolith alone produced no noticeable effect on the 
equilibrium or righting reactions of the dogfish, nor did 
there appear to be any loss of tonus. I have removed 
this otolith many times by the method described above. 
Its loss does not alter or weaken any of the compensatory 88 
LABYRINTH AND EQUILIBRIUM 
movements; it does not disturb the equilibrium or the 
righting reaction, nor is the muscle tonus affected in any 
noticeable degree. These results are in conformity with 
the findings of Laudenbaeh133 in his experiments on the 
frog and on Siredon pisciformes. Except for a transi- 
tory effect of the operation these animals show no disturb- 
ance of movement or position after destruction of the 
saccular otolith. 
If the utricular otoliths have been successfully re- 
moved and the condition described above has been 
attained, namely the retention of compensatory move- 
ments to rotations in all planes, the righting reaction, and 
the maintenance of equilibrium, the consequent removal 
of the six ampullae produces at once a profound alteration. 
The condition of a dogfish deprived of the utricular oto- 
liths and the six ampullae may be stated in the following 
way: (1) No compensatory movements are made on 
rotation around any axis whatever. This statement may 
be modified by saying that in some cases a slow and slight 
tendency to compensation, requiring many seconds or 
even minutes for its completion, may be seen. No one 
familiar with the reactions of the animal would ever con- 
fuse this with a labyrinthine reflex. (2) The animal 
shows no tendency to maintain bodily equilibrium; it 
swims indifferently back or belly upward. A weak speci- 
men may also come to rest on its side or back, but a vigor- 
ous specimen usually rights itself on the bottom of the 
tank. In other words the geotropic reactions of the ani- 
mal are definitely and completely lost; the stereotropic 
reaction is retained. 
The results of these experiments show that the assump- 
tion of a sharp differentiation of functions between the EXPERIMENTS ON THE OTOLITHS 
89 
otolith-bearing, vestibular portions of the labyrinth and 
the semicircular canals is not justified by the facts. Be- 
tween the effects of extirpation of the one and of the 
other set of structures there is more resemblance than 
contrast. They certainly reenforce each other, for the 
reactions produced by either one alone are always slower 
and less vigorous than when both sets of organs are intact. 
It would not, however, be safe to affirm that the functions 
are identical. In one respect a difference is apparent; 
namely, in the response to rotation in a horizontal plane. 
Another difference is seen in the effects of removal of 
all the otoliths or of all the ampullae from one ear. 
Removal of the otoliths of one ear causes very little 
abnormality of position or movement. It would not be 
safe to say that no abnormality is produced; but it always 
seemed that an asymmetry of eyes and fins was only 
decidedly noticeable in those operations which had not 
gone smoothly, and where considerable accessory damage 
had been done to the saccule and utricule. If we place 
in the same aquarium a dogfish which has had all the oto- 
liths removed from one ear and another which has had all 
the ampullae removed from one ear the difference in posi- 
tion will be very noticeable. The fish with ampullae ex- 
tirpated will have definite forced positions of body, eyes 
and fins; the one with otoliths removed will be almost 
normal in position and movement. 
Experiments on the otoliths in forms other than 
selachians are not very numerous. Lyon149 reported the 
removal of the otoliths from the ears of the flounder, 
Pseudopleurinectes, and found that the compensatory 
movements and the retained compensatory positions were 
still produced by rotational changes of position. In these 90 
LABYRINTH AND EQUILIBRIUM 
experiments, to exclude the effects of retinal stimulation, 
he took the precaution to cut both optic nerves. It ap- 
pears, however, from his statement that he removed only 
the large otoliths of the sacculi, which Parker and the 
writer had each found not to be concerned in equilibrium 
reactions of the dogfish, while he left untouched the really 
important, though much smaller, otoliths of the utriculi. 
Benjamins32 removed the otoliths from the labyrinth 
in two other bony fishes, namely the perch and the carp. 
He states that the removal of the saccular otolith causes 
a decrease in the rotation of the eyes on their visual axes, 
especially when the anterior pole moves ventrally, the 
reaction which occurs when the head is tilted upward; 
there is also an effect, but less in amount, on the reactions 
to rotation in the other planes. Removal of the utricular 
otoliths also caused a reduction in the rotation of the 
eyes on their visual axes, especially when their anterior 
poles move dorsally, but the reactions to rotations in 
other planes were almost or entirely lost. If destruction 
of the utricular otolith causes the loss of reaction to rota- 
tions around the transverse and the longitudinal body 
axes, as Benjamin’s experiments seem to show, the con- 
dition is the same as in the dogfish; but it is not then 
clear why removal of the saccular otoliths also had an 
effect on rotation around the transverse axis. Unfortu- 
nately Benjamins did not make clear what amount of 
incidental injury his method of removal of the saccular 
otolith may have done to the ampullae. 
The anatomical arrangements in the mammalian ear 
have, until recently, made experiments on the otoliths 
seem impossible. A very important contribution to this 
difficult subject has been made by deKleijn and Magnus.120 EXPERIMENTS ON THE OTOLITHS 
91 
Wittmaack245 had found that when guineapigs were sub- 
jected to centrifugalization at about the rate of two thou- 
sand revolutions per minute destructive changes took 
place in the otolith-bearing parts of the labyrinth, while 
the cristae of the ampullae remained normal in their histo- 
logical structure. DeKleijn and Magnus made use of the 
same method, rotating the animals under ether narcosis 
at a rate of from 960 to 1000 revolutions per minute for 
from iy2 to 2 minutes. The animals were afterwards 
carefully tested for their physiological reactions. They 
were later killed and the histological changes in the laby- 
rinth were studied and correlated with the physiological 
effect which had been observed. The results of these 
experiments lead to conclusions which differ in part from 
those which had been reached by the writer from experi- 
ments on the dogfish. 
Some of the centrifugalized guineapigs gave normal 
complementary movements in response to rotations in all 
planes, but the positions were not sustained after the 
rotation ceased; in other words, the dynamic functions 
remained normal but the static functions were lost. The 
histological examination in these cases showed that the 
otolith membrane had been thrown out of position, but 
that the cristae of the ampullae remained uninjured. These 
results of deKleijn and Magnus give strong support to 
the belief that the ampullae and the otolith-organs have 
separable functions; that the ampullae indeed respond 
only to movement, and that the otolith-organs on the other 
hand, are the source of the reflexes of position. It may be 
that a process of differentiation has taken place in the 
development of the mammal so that a greater difference 
exists in the functions of these parts of the labyrinth in 92 
LABYRINTH AND EQUILIBRIUM 
the mammals than in the lower vertebrates. The results 
of further investigation of this question will be a matter 
of great interest. 
2. Stimulation Experiments on the Otolith-organ 
Direct stimulation of the otolith-organs are not very 
easy to perform even in selachians, which, on account of 
the large size of the vestibule, are the most favorable ani- 
mals for the purpose. In these fishes, however, the fri- 
able nature of the otoliths makes it difficult to apply 
mechanical stimulation without immediate injury; a very 
little pressure causes them to break up and renders the 
results uncertain. Moreover the vestibular parts of the 
membranous labyrinth which overlie the otoliths are con- 
nected directly with the mouths of the semicircular canals 
very near to the ampullae. On account of the high sen- 
sitivity of the ampullae to mechanical stimulation, the 
attempt to reach and stimulate the otolith-organs without 
previous removal of the ampullae is almost certain to give 
confused and unreliable results. 
Lee137 reported the effects of stimulation of the maculae 
to be exceedingly variable. The stimulation brought 
forth in the same animal at different times, the same eye 
and fin movements as those which follow the stimulation 
of the three ampullae. Since Lee does not mention that 
in any of these experiments he had previously removed 
the ampullae, the presumption is strong that some at least 
of his results were really caused by the excitation of the 
cristae instead of the maculae. 
Kubo130 described experiments on the otoliths in a 
number of dogfish, skates, and rays with results which 
accorded very nicely with the hypothesis of Breuer that EXPERIMENTS ON THE OTOLITHS 
93 
the vestibule has three otoliths in three planes in space, 
directly comparable to the semicircular canals; the otolith 
of the utriculus being horizontal, and those of the sacculus 
and lagena vertical and perpendicular to each other. 
Moreover, according to Breuer, each of these has a groove 
in which it can slide more readily than in any other direc- 
tion. This idea of Breuer’s seems to have had a fascina- 
tion for many minds, for it has reappeared in a number of 
slightly different forms. It has led to some very beauti- 
ful anatomical work, but it has not had much support of 
the most essential kind, namely, from physiological ex- 
periment, and the results of stimulation of the utricular 
otolith have been found by the writer to be completely 
fatal to the hypothesis. 
A working hypothesis clearly formulated and properly 
used can be of very great service in scientific investiga- 
tion ; but it can also become a source of expectations which, 
where results are at best difficult to observe and record, 
may lead one to think he sees exactly those things which 
justify his expectations. This appears to have been 
the case with Kubo in his experiments on the ears 
of selachians. 
Kubo reported that in the opened vestibule he could 
see the otoliths slide on account of their weight, when the 
fish was tilted far enough to cause complementary eye 
movements. When the head was tilted downward he 
believed he saw the utricular otolith slide forward; when 
the head was elevated he thought the saccular otolith 
moved visibly backward. He also described eye move- 
ments resulting from stimulation of the maculae by the 
application of pressure to the different otoliths. Since 
Kubo’s account of the much simpler experiment of stimu- 94 
LABYRINTH AND EQUILIBRIUM 
lation of the ampullae is full of mistakes, one cannot feel 
that his observations on the otoliths are to be taken seri- 
ously. It is very evident that he did not remove the 
ampullae; indeed he expressly states that the experiment 
succeeded better when the vestibule was opened and the 
stimulation performed “without removing the gelatinous 
capsule. ’ ’ According to Kubo, pushing the otolith of the 
recessus utriculi forward caused the eyes to roll back- 
ward on their axes, i.e., into the compensatory position 
for the head downward posture of the fish; this we know 
is the effect of stimulation of the ampulla of the anterior 
vertical canal. Pushing the same otolith backward had 
no effect. Pushing the otolith of the sacculus backward 
caused the eyes to roll forward on their axes, i.e., the 
reaction for the head up position; pushing the saccular 
otolith forward had no effect. When he pushed the sac- 
cular otolith outward the eye on the stimulated side was 
elevated. Sometimes, however, he saw eye movements in 
the horizontal plane when he touched the middle of the 
saccular or the posterior part of the utricular otolith. 
Referring to these horizontal movements he says, “In 
this case one cannot exclude the possibility that the hori- 
zontal ampulla was indirectly affected,” for it stands in 
close relation to the utricular otolith. The resulting con- 
fusion emphasizes the necessity of complete removal of 
the ampullaB before attempting stimulation experiments 
on the otoliths. 
In my extirpation experiments I had found that after 
removal of all six ampullae, and after washing out the 
large otolithic masses of the sacculi (and lagenae), the 
dogfish and the ray still gave good compensatory move- 
ments in response to rotations around the longitudinal EXPERIMENTS ON THE OTOLITHS 
95 
and the transverse axes.172 These responses I proved to 
be dependent on the presence of the otolith of the recessus 
utriculi for they disappeared when it was removed. I 
also found it possible to stimulate mechanically the 
otolith-organ of the recessus and to get results just as 
clear and consistent as those obtained from stimulation 
of the ampullae. I quote the following record of an 
experiment.173 
“July 16, 1920. Large dogfish (Galeus). 
Opened both ears and removed all six ampullae. 
Using a stiff bristle tipped with wax and the wax covered by a thin 
layer of absorbent cotton, applied pressure to various parts. 
Eight ear. 
Pressed on right (lateral) side of otolith (of recessus utriculi) ; right 
eye depressed, left eye elevated. 
Pressed on left side of otolith; left eye depressed, right eye elevated. 
Repeated several times with uniform results. Otolith soon disin- 
tegrated: no more response. 
Left ear. 
Pressed on left side of otolith; left eye depressed, right eye elevated. 
Pressed on right side (median) of otolith; right eye down, left eye up. 
Repeated several times with same result.” 
Experiments made in this way gave fairly constant 
results, but it was not possible to repeat the observation 
many times without injury to the otolith-organ. A new 
and very simple method was later found which permitted 
repetition of the stimulation many times before serious 
damage was done to the otolith and which gave abso- 
lutely constant results. The experiment is performed 
as follows: 
A small mass of absorbent cotton is formed into a tiny 
cushion about the size of the otolith of the recessus and 96 
LABYRINTH AND EQUILIBRIUM 
is cautiously placed on top of that otolith. The cotton 
is then grasped with the points of a fine forceps and 
gently moved to the right or left, forward or backward 
at will. I quote again from my notes: 
“July 23, 1920. Large shovel-nosed ray (Rhinobatus). 
Removed ampullae from left ear. 
Exposed small otolith (of recessus utriculi) and placed on it the 
pellet of cotton. 
Movement of pellet to left caused depression of left eye and elevation 
of right eye. 
Movement of pellet to right caused depression of right eye and elevation 
of left eye. 
Movement of pellet forward caused both eyes to roll forward on their 
axes (anterior pole of each eye depressed and posterior pole elevated). 
Movement of pellet backward caused both eyes to roll backward on 
their axes. 
When pellet was moved to one side eyes moved in same sense. 
When pellet was held to any side, the eye position was retained. 
Removed the three ampullae of the right ear. 
Repeated the experiment on the right ear with exactly the same results. 
Repeated a score or more of times with no noticeable diminution of 
the response. 
Holding the pellet to any side held the eyes in the corresponding position.” 
I have repeated these experiments on dogfish, leopard 
sharks, and rays. The experiments on the ray (Rhino- 
batus) were particularly striking. This fish is broad and 
flat and usually remains at or near the bottom of the 
water. It is not, apparently, used to much turning over 
or tilting of the head up or down. Taken out of the water, 
or rotated in the water it does not show any of the com- 
pensatory movements in so marked a degree as does the 
dogfish. When, however, the stimulation was applied to 
the recessus as described above, the eye movements were EXPERIMENTS ON THE OTOLITHS 
97 
extraordinarily vigorous, much, more so than in response 
to rotation of the body of the uninjured animal. The 
eyes rolled right or left, forward or backward, as if on 
actual mechanical axes manipulated by cords. 
These results were at first very surprising. Follow- 
ing the a priori reasoning usually applied, I had expected 
that pressure on the right side of the otolith would have 
the same effect as inclining the head to the right, for the 
weight of the otolith ought to cause a pressure on the side 
to which the head was inclined, and I supposed that this 
pressure would be the adequate stimulus. I found, on 
the contrary, that pressure on the right side of the otolith 
of either ear produces the same eye movement which 
results as the compensatory motion to rotation of the 
body to the left around the longitudinal body axis; and 
that pressure on the anterior side of the otolith gives the 
same effect as tilting the head upward. In each case the 
response is precisely opposite to that which would be 
expected if the stimulation were produced by the pres- 
sure due to the weight of the otolith; for when the 
body is tilted to the right, the weight of the otolith 
must be shifted to the right, but the reaction to this 
rotation is elevation of the right eye and depression of 
the left eye. When pressure is applied directly to the 
right side of the otolith, as in the experiments above 
described, the opposite result is obtained; namely, depres- 
sion of the right eye and elevation of the left. It must 
be, then, that the stimulation does not result from the di- 
rect effect of the pressure but from the shifting of the 
otolith; a displacement to the left is brought about by 98 
LABYRINTH AND EQUILIBRIUM 
pressing on its right side under the conditions of the ex- 
periment, and a similar displacement to the left results 
from tilting the animal to the left. In other words, it is 
the displacement of the otolith, and not the pressure due 
to the weight of the otolith, which is the actual stimulus 
and it is the direction of the displacement which deter- 
mines the direction of the compensatory movement in 
response to the stimulus. CHAPTER VIII 
THE MECHANISM OF THE DYNAMIC FUNC- 
TIONS OF THE LABYRINTH 
We have seen that the ampullse alone, without the oto- 
liths, suffice for all the dynamic functions of equilibrium 
of the ear, and that the otolith-organs alone, without the 
ampullsB, also suffice for all the dynamic functions except 
that of response to rotation in a horizontal plane. It now 
remains to consider the mechanism through which these 
functions are called into play. 
1. The Dynamic Functions of the Ampulla 
Mach, Brown and Brener at first attached paramount 
importance to the space relations of the semicircular 
canals. It was assumed that rotation of the head in the 
plane of a canal caused, by the inertia of the endolymph, 
a current within the canal contrary to the direction of 
rotation. It was supposed that the hair-cells of the 
crista were deflected by the current and stimulation of 
the nerve endings resulted. Mach,161 however, very soon 
saw that, under the conditions existing in the labyrinth 
during normal physiological stimulation, such a current 
could not be produced, and Breuer48 later admitted that 
the hair-cells do not project into the endolymph but are 
covered by the gelatinous mass of the cupula. 
Mach’s later view was that an endolymph movement 
could not occur in the semicircular canals as the result of 
a rotational movement of the head, but that a tendency to 
move would be the result. A tendency to move, without 
the occurrence of actual motion, can be nothing else than 
99 100 
LABYRINTH AND EQUILIBRIUM 
a pressure. This raises the question whether a pressure 
of this order of magnitude could really act as a stimulus. 
That pressure alone is not the stimulus which gives rise 
to compensatory movements, can be shown in a variety 
of ways (Lyon,149 Maxwell170). 
When the horned lizard, Plirynosoma, is moved in a 
straight line with the long axis of its body perpendicular 
to the direction of the movement, beautiful compensatory 
motions are made, if the animal’s eyes are open. If the 
direction of movement is to the animal’s right the head 
and eyes turn slowly to the left and then suddenly jerk 
back to the primary position. This action is repeated 
rhythmically and constitutes a typical nystagmus with 
the slow component in the direction opposite to that in 
which the animal is moved. This nystagmus is excited 
by motion in a straight line, movement of translation, only 
while the eyes are open; not a trace of compensation 
occurs when retinal stimulation is excluded, even if the 
movement is so sudden and so rapid that the animal must 
be tied to prevent its being thrown off the board. When 
a dogfish is moved similarly in a straight line no compen- 
satory movement takes place even if the eyes are open. 
A lateral movement of translation must of necessity 
cause a pressure, through the inertia of the contents of 
the labyrinth, and yet no compensatory movement is 
excited. If, however, the movement of the animal devi- 
ates from the straight line so that an arc, even of very 
long radius, is described the compensatory movement 
is elicited. This observation alone would indicate that 
not merely pressure, but a movement of rotation, a 
torsion effect, is a necessary factor in bringing about 
the excitation. MECHANISM OF DYNAMIC FUNCTIONS 
101 
It has been argued that, in a movement of translation 
to the right or left, the pressure conditions in the right 
and in the left labyrinths are in the opposite sense; when 
the pressure in the right ear is to the median side, the 
pressure in the left ear is to the lateral side of 
the cavity. Under these conditions, it has been assumed, 
the excitations from the two ears would tend to have 
exactly opposite effects and hence would neutralize 
each other. But a dog-fish in which one labyrinth has 
been extirpated, and which still shows good compensatory 
movements when rotated to the sound side, gives no com- 
pensatory movement to pure movements of translation 
either to the right or left. 
It has also been argued that pressure changes could 
not be produced in the ampullae by any rectilinear move- 
ment, because the ampulla and canal form part of a closed 
ring which must therefore move as a unit. This would 
be true if the membranous labyrinth were a rigid and not 
a flexible system, or even if the membranous labyrinth 
were enclosed in a rigid capsule completely filled with in- 
compressible liquid; but this is not at all the case. In 
the selachians the perilymphatic space is in communica- 
tion with the exterior through the ductus endolymphati- 
cus, and also it is not rigidly separated from the cranial 
cavity. In many of the bony fishes, one or more of the 
semicircular canals lie free in the pial space of the cranial 
cavity (Parker,192 Benjamins32). De Kleijn and Mag- 
nus119 have pointed out that in the mammal, the labyrinth 
is separated from the tympanic cavity by a partition 
which is not wholly unyielding, and they have described 
a model which shows that rectilinear motion can produce 102 
LABYRINTH AND EQUILIBRIUM 
a movement or relative change of pressure in a structure 
arranged like the ampullae and canals. 
We are are not discussing here the question of the 
existence of sensations or reflexes excited by movements 
of translation and mediated through the labyrinth. The 
observations of Ach,1 and of deKleijn and Magnus119 
make it evident that such reflexes exist; but the responses 
are not such as could be mistaken for the compensatory 
movements with which we are at present concerned. 
Fig. 6. 
Fiq. 5. 
Since, then, the compensatory motions are elicited by 
rotational movements only, we must analyze more closely 
the forces which bring about the excitation. Imagine a 
wheel W (Fig. 5.) with another wheel X mounted upon it, 
so that the axis of X is coincident with the axis of W. If 
the bearing on which X is mounted could be absolutely 
frictionless then the rotation of W could have no effect on 
the orientation of X; the arrow upon X would continue to 
point in its original direction. If now the axis of X be 
connected to the wheel W by a wire which is rigidly at- 
tached to both wheels, the rotation of W will tend to be MECHANISM OF DYNAMIC FUNCTIONS 
103 
communicated to X, but the inertia of X will oppose this 
tendency, and the wire will be subjected to a certain 
amount or torsion before the angular velocity of X be- 
comes equal to that of W. We may call this part of the 
effect of the inertia of X its torsion effect. 
If we next move the wheel X to some eccentric posi- 
tion, as at P (Fig. 6.) and if the mounting of X is friction- 
less the rotation of W will not cause a change in the ori- 
entation of X; if the arrow was directed to the north at 
the beginning it will continue to point north during the 
rotation of W. But if we suppose once more the axis of 
X to be connected to the wheel W, then, as before, when 
W is rotated the inertia of X will exert a torsion effect 
upon the connecting wire. The amount of this torsion 
will be the same in the two cases. 
But in the eccentric position of X another inertia fac- 
tor will have to be considered, namely, the centrifugal 
force, which is the pressure exerted at P along the radius 
CP. For any given rate of rotation the amount of this 
pressure varies directly as the radius of the circle de- 
scribed by P around C, and for any given radius the pres- 
sure varies as the square of the angular velocity; or, 
stated in general terms, F=mrW,2 where F is the centri- 
fugal force, m the mass of the rotating body, and W the 
angular velocity. 
In the equilibrial reactions of the labyrinth we have to 
distinguish between the possible centrifugal effect and 
the torsion effect. This was investigated in the follow- 
ing way.170 
An animal was placed on a turntable and slowly 
rotated through an angle of 45 degrees. By a series 
of trials a rate of rotation—to be more exact, an accelera- 104 
LABYRINTH AND EQUILIBRIUM 
tion—was found which was just equal to the threshold 
of stimulation. The animal was then placed at some 
other distance from the axis of rotation and the threshold 
again determined. The radial force for any given par- 
ticle of a rotating body, at a given rate of rotation, varies 
as the distance of that particle from its centre of rotation. 
The torsion effect, on the other hand, depends on the 
angular velocity, but not at all on the radius. If it can 
be shown that a position on the turntable at a distance 
from the axis is more effective in evoking the compensa- 
tory movements than a position nearer to the centre, 
then there is evidence that pressure is an effective stimu- 
lus. If no such difference exists, the exciting cause must 
be the torsion effect alone. 
The animal used was the horned lizard, Phrynosoma, 
commonly known as the horned toad. This is especially 
convenient for such experiments as Loeb145 had pointed 
out, because of the fact that the eyes can be caused to 
close by merely touching the lids, and retinal reflexes are 
thus very simply excluded. To facilitate the observation 
of very weak reactions a light straw, as index, was at- 
tached to the animal’s head and projected 80 mm. beyond 
the snout. A graduated arc was marked on the turntable, 
and in this way very slight movements could be per- 
ceived. Table II. shows a specimen experiment. The 
turntable was rotated by hand through an arc of 45 de- 
grees in each case; the time occupied in that amount of 
turning was indicated by a stop watch and is set down in 
column 2. Several trials were made in the one position; 
then the animal was moved to the other position and a 
number of trials made. This was done to eliminate pos- MECHANISM OF DYNAMIC FUNCTIONS 
105 
sible changes in the excitability due to the effect of han- 
dling. The order of the trials is indicated by the trial 
number in column 1. The response is shown in column 3. 
TABLE II. 
EFFECT OF ROTATION THROUGH 45 DEGREES AROUND A VERTICAL AXIS. 
Head 25 mm. from centre of turntable 
Head 300 mm. from centre of turntable 
1 
2 
3 
1 
2 
3 
Trial No. 
Seconds 
Compensatory 
movement 
Trial No. 
Seconds 
Compensatory 
movement 
1 
7 
Slight 
6 
8 
Slight 
2 
7 
Slight 
7 
9 
None 
3 
12 
None 
8 
9 
Slight 
4 
10 
None 
9 
10 
None 
5 
8 
Slight 
10 
10 
None 
14 
8 
Slight 
11 
8 
Slight 
15 
8 
Slight 
12 
7 
Slight 
16 
8 
Slight 
13 
6 
Strong 
17 
6 
Strong 
22 
10 
None 
18 
5 
Strong 
23 
9 
None 
19 
10 
None 
24 
8 
None 
20 
9 
None 
25 
7 
Slight 
21 
7 
Slight 
26 
5 
Strong 
A second set of observations was made in which the 
animal was placed upon a board which could be rotated 
smoothly through 45 degrees about a horizontal axis. 
Inspection of Table II. shows that the threshold for 
horizontal rotation was reached with a speed of about 
8 seconds for 45 degrees and that there is practically no 
difference in the effect produced when the distance from 
the centre is altered. A similar result was obtained for 
rotation around the transverse axis of the body. Since 
increasing the centrifugal force twelve fold has no ap- 
preciable effect on the threshold of stimulation we are 106 
LABYRINTH AND EQUILIBRIUM 
justified in concluding that in rotational movements, with- 
in ordinary physiological limits, the influence of centri- 
fugal force is negligible, and that the excitation depends 
wholly upon the torsion effect. 
It is also significant that the direction of the torsion 
determines the sense of the compensation. This is shown 
by the following well-known fact: When an animal is 
placed in an eccentric position on the turntable and is 
rotated to the left (the observer’s left) the compensatory 
movement is to the animal’s right whether the head is 
directed toward the circumference or toward the centre. 
But when the head is directed to the circumference the 
compensatory movement is opposite to the movement of 
the animal as a whole; when the head is directed to the 
centre the compensatory movement is in the same direc- 
tion as the movement of the animal. This is illustrated 
by the accompanying photograph (Fig. 7). 
The semicircular canals have been commonly believed 
to be an essential part of the mechanism for the normal 
excitation of the ampullae. Nevertheless direct experi- 
ments show that the ampullae are not necessarily depen- 
dent on the canals for the performance of their functions. 
It was found by Loeb143 that in the dogfish the canals 
could be cut through and even large portions could be 
excised without affecting the compensatory movements 
or the functions of equilibration, and Ewald’s experi- 
ments indicated that, in the pigeon, after the canals had 
been ligatured, plugged, or cut, compensatory movements 
of the eyeballs and eye nystagmus were produced 
by rotation. Fig. 7.—Compensatory position of frogs photographed while rotating to left. The center of the 
dish containing the frogs was about 16 inches from the center of the turntable. The frog on the left 
faced the center, the one on the right the periphery. MECHANISM OF DYNAMIC FUNCTIONS 
107 
These experiments show that the canals are not neces- 
sary to the dynamic functions. Certain objections, how- 
ever, might be raised. Loeb does not state specifically 
that all the canals were cut. Since I have shown that all 
the dynamic functions except that of response to rotation 
in a horizontal plane may be performed by an ear from 
which all the ampullae have been removed, it would be 
necessary to know that the horizontal canals had been 
cut before the proof could be considered complete. Fur- 
thermore, in the dogfish each horizontal ampulla reacts 
to rotations in one direction only; this according to 
Ewald is not the case in the pigeon but his proof of 
this is also incomplete. 
Since, in the dogfish, the response to horizontal rota- 
tion is brought about by the horizontal ampulla only, 
it would be a crucial experiment artificially to change 
the plane of this canal with reference to the skull of the 
animal and see whether this change does or does not 
alter the response to rotation. I have succeeded in doing 
this by the following method.172 
The right horizontal canal was laid bare for nearly the 
whole distance from its ampulla to the point where its 
posterior end reenters the vestibule. It was then liga- 
tured and cut as far posterior as possible and the cut 
end was gently lifted into a vertical position, laid over 
against the skull, and supported there by a pledget of 
cotton. Its new plane was at right angles to its original 
plane and also at right angles to the long axis of the 
body. It is needless to say that in this operation ex- 
treme care must be taken not to exert the least traction 108 
LABYRINTH AND EQUILIBRIUM 
on the ampulla. It is clear that with the canal in the new 
position rotation of the animal in a horizontal plane, 
that is, around a dorsoventral axis, could not even the- 
oretically give rise to a current in the canal. On rotation 
to the right, however, the eyes turn to the left and on 
rotation to the left the eyes turn to the right; that is, 
the ampulla whose canal is now at right angles to its nor- 
mal position acts just like the other ampulla whose canal 
is still horizontal. On the other hand, rotation of the 
animal around its longitudinal axis (in the new plane of 
the canal) never produces a deviation of the eyes to the 
left as it might be supposed to do if the rotation causes 
a current in the canal and the current excites the ampulla. 
This experiment, then, shows conclusively that the excita- 
tion of the sensory structures in the ampulla is due to 
some other cause than the production of a current in 
the canal. 
The experiments just described show clearly that the 
function of the ampulla does not depend primarily on 
the canal, but that it can be performed under conditions 
in which it is impossible for a current to exist. It would 
therefore be of no consequence to consider whether Mach 
was right or wrong in his conclusion that on account of 
the small size of a semicircular canal, a movement of 
rotation could not produce a current but only a momen- 
tary impulse. It has been assumed, however, by many 
writers that proof of the occurrence, or even of the pos- 
sibility, of a current in the canal, is also proof that the 
current is the cause of the excitation. It will be of inter- 
est then to review briefly some experimental work on 
this question. MECHANISM OF DYNAMIC FUNCTIONS 
109 
Mach151 constructed a glass model of the form and 
size of a human semicircular canal.* When this was 
tilled with liquid and rotated on the centrifugal machine 
no movement of the liquid could be perceived. Rossi217 
made a collodion model and filled it with a liquid contain- 
ing suspended particles for the easier observation of 
movement. When this was rotated a counter movement 
of the particles was seen. Maier and Lion165 made sim- 
ilar experiments with capillary glass tubes of different 
diameters using for endolymph a suspension of blood cor- 
puscles in physiological salt solution. With a compound 
microscope, objective No. 3, they were able to see a rela- 
tive movement of liquid in the tube at the beginning and 
end of rotation. They distinguished the following stages: 
(1) At the beginning of the rotation the liquid appeared 
not to move at all. (2) On account of friction the liquid 
began to move, but more slowly than the tube. (3) The 
movement of rotation having become uniform, the liquid 
and the tube moved at the same rate; no relative move- 
ment to be seen. (4) When the rotation was stopped 
the liquid moved onward in the tube for a brief time. 
With a relatively large tube they found that stage 4, the 
after-movement, could last 2 to 6 seconds. When, how- 
ever, they used a tube 0.75 mm. in diameter, therefore 
* Most persons who have experimented with models of the semicircular 
canals have seemed to assume that it would be sufficient to use tubes 
of the calibre of the canals in the human ear. We must remember, however, 
that there are animals which seem to exhibit good labyrinth functions, 
but which possess canals of a very different diameter. According to Gray,03 
the canals of the squirrel’s ear have about one-fifth the diameter, and hence 
about one twenty-fifth the cross-section, of those in the human ear. These 
proportions must very greatly decrease the inertia effect of the contents 
of the canals and at the same time enormously increase the resistance 
to movement on account of friction. 110 
LABYRINTH AND EQUILIBRIUM 
of a lumen nearer to that of a semicircular canal, stage 4, 
though still perceptible, was too short to be measured. 
This remained true after a rotation of twenty seconds or 
longer. Stages 1 and 2 were also momentary. Similar 
observations were made on the actual canals of the pigeon 
and the codfish. 
Maier and Lion assume, on the basis of their experi- 
ments, that the inertia currents produced in the canals 
by the rotation of the head are the adequate stimuli for 
the ampullae. When a man is turned in a revolving chair, 
for the first instant, only a fraction of a second, the endo- 
lymph, on account of its inertia, remains at rest. The 
peripheral ends of “the sensory hairs of the cupula,” 
or the cupula itself, are struck against the motionless fluid 
and are strongly bent in a direction opposite to the revo- 
lution. This excites a lively nystagmus. On account of 
the friction the motion more and more approximates to 
that of the canal (stage 2). During this time the sense 
hairs are still bent and continue to send impulses to the 
central nervous system. This period is extraordinarily 
short. During the remainder of the rotation endolymph 
and canal move alike. When the rotation is stopped the 
endolymph continues to move on account of its inertia, 
and bends the hair-cells in the direction of the rotation 
(stage 4). 
Maier and Lion realize that the two periods (stages 1 
and 4) in which the liquid could be seen to move were each 
only momentary. The after-movement, stage 4, though 
perceptible to the eye was too brief for an estimation of 
duration to be made, yet the after-nystagmus which it 
is supposed to induce lasts 20 seconds or longer. These 
authors admit that neither this nor the long lasting ny- MECHANISM OF DYANMIC FUNCTIONS 
111 
stagmus at the beginning of the rotation, represents the 
actual time of movement of the endolymph. Indeed, 
according to their observations and conclusions, an after- 
nystagmus lasting 20 seconds is excited by an endolymph 
current lasting a small fraction of a second. For this 
reason they are led to argue that the sudden bending of 
the hair-cells gives rise to chemical changes the effect 
of which continues for some time after the bending has 
ceased. Such a change, however, can easily be accounted 
for without assuming an endolymph current in the canal 
at all. The observations of Maier and Lion do not, as 
they suppose, prove the endolymph current to be the cause 
of the excitation of the ampulla ; but, on the other hand, 
they show the absence of any direct relation between 
current and stimulus. 
No further consideration need be given to the possi- 
bility of currents in the semicircular canals as the cause 
of the excitation which, on rotation, gives rise to the 
reflex compensatory movements. We must therefore 
consider other possible causes. These might be: (1) ef- 
fects dependent on the inertia of the mass of liquid or 
other material in the vestibule, or (2) due to the inertia 
of the contents of the individual ampullae, or (3) to inertia 
effects within the sensory cells themselves. It would 
be impossible to decide between these a priori. 
In my earlier experiments I found that after destruc- 
tion of the structures in the vestibule I could never obtain 
compensatory movements on rotating the dogfish around 
its dorsoventral axis. For a long time I was inclined to 
think that the absence of the reflex was due to some sort 
of injury to the ampullae, although these appeared to be 
as sensitive as before to direct mechanical stimulation; 112 
LABYRINTH AND EQUILIBRIUM 
the slightest pressure caused decided eye movements. 
When, however, I was finally able to remove the otolith 
from the recessus utriculi by slitting open the utriculus 
lengthwise without tearing it across I found that the 
compensatory movements to rotation in the horizontal 
plane were not abolished. Since the destruction or the 
transection of the utriculus abolished the reflex with no 
apparent reduction in the direct sensitivity of the am- 
pulla it became clear that the utricular (and possibly the 
saccular) structures are essential parts of the mechanism. 
In attempting to analyze more closely the arrange- 
ments of the parts concerned, it is to be noticed that the 
movement of rotation which acts as a stimulus to any 
given ampulla carries foremost the side of the ampulla 
which bears the crista. Thus the cristae of the anterior 
canals are on the lower side of their ampullae and a rota- 
tion around a transverse axis in the direction head down- 
wards excites them; the cristae of the posterior canals are 
also on their lower sides and a rotation around a trans- 
verse axis in the direction head upwards (back part of the 
head downward) excites them. So also the crista of the 
right horizontal canal is on its right or outer side and the 
stimulus for it is rotation to the right. Of course a 
similar relation exists for the left ampullse. Examination 
of the extensive series of drawings by Retzius249 shows 
that the dogfish is not a special case but that the arrange- 
ment is general. 
A second fact which is significant is that the mouths of 
the ampullae are continuous with the utriculus, an elong- 
ated, thin walled sac, stretched across the cavity of the 
vestibule and occupying only a portion, in the dogfish a 
not relatively large portion, of the vestibular space. MECHANISM OF DYNAMIC FUNCTIONS 
113 
Furthermore the utriculus is so attached by means of 
the sinus superior and other structures that it is rela- 
tively free to move toward the dorsal but not toward the 
ventral side of the cavity. The relations as far as the 
ampulla of the anterior vertical canal is concerned are 
shown diagrammatically in Fig. 8. Rotation of the head 
Fio. 8.—Diagram to illustrate relation of vestibular structures to ampulla, v, vestibule; 
u, utricle; ss, sinus superior; ac, anterior vertical canal; c, crista; n, nerve. 
downwards, that is, in the direction of the outer arrow, 
would tend by inertia, to produce the same effect as if, 
with the head stationary, the perilymph was rotated in 
the opposite direction, as indicated by the small arrow 
within. This would put pressure and tension on the 
under side of the anterior end of the utriculus; this 
tension would be communicated to the ampulla and espe- 
cially to its lower side wThich bears the crista. Rotation 
in the opposite direction could not exert the same trac- 
tion on the ampulla. 114 
LABYRINTH AND EQUILIBRIUM 
In order to convince myself of the correctness or incor- 
rectness of the above reasoning, I constructed a model 
by carving cavities and channels corresponding to the re- 
lations shown in Fig. 8. In these I placed a thin rubber 
model of the two canals shown in the figure. The canals 
and utriculus as well as the perilymphatic space were filled 
with mercury. On rotating the apparatus it could be seen 
that movement in one direction gave a very perceptible 
pull on the ampulla; movement in the opposite direction 
was almost without effect. It is possible that the rotation 
which puts the ampulla under mechanical strain would 
also tend to produce an increased liquid pressure within 
it, but this was not investigated. 
Careful dissection shows that mechanical relations 
analogous to those just described hold also for the poste- 
rior ampulla and the horizontal ampulla. 
I wish to point out the advantage which the vestibular 
mechanism possesses on account of the mass of liquid. 
A relatively large free mass of liquid with a relatively 
small surface would show more inertia effect than a small 
mass with a relatively large surface area. 
This principle was nicely shown by a model made by 
W. H. Hoyt, a student of mine. The model consisted of 
a glass tube of approximately 1 mm. lumen, bent into a 
circle, and having at one place an enlargement of several 
millimetres diameter to represent an ampulla. The space 
was filled with a liquid containing minute flakes of alumi- 
num powder. When the model was rotated very rapidly 
and then suddenly stopped he could, indeed, see some 
movement for an instant in the canal, but the striking fact 
was that a marked rotational movement of considerable 
duration took place in the ampulla. The dimensional MECHANISM OF DYNAMIC FUNCTIONS 
115 
relations of the ampulla in Hoyt’s model would more 
appropriately represent the vestibule. Certainly the 
larger cavity allows greater opportunity for a longer 
lasting after-rotation. 
It has not been a part of our problem to find explana- 
tions for the existence of structures in the labyrinth, but, 
on the contrary, to find out where and how definite func- 
tions are performed. It may be suggested, however, that 
liquid may move through the canals, not as a stimulus 
to the nerve endings in the cristae, but as a means of 
equalization of pressure. Indeed, if the ampullaB were 
mere diverticula from the vestibule it is conceivable that 
pressure conditions could arise in them which might 
seriously affect the performance of their functions. If 
these injurious pressures were caused by rotation of the 
head, then the effective provision for relief would be a 
circular passage in the plane of the movement which 
caused the pressure. It is not unreasonable to suppose 
that the canals supply a means for the equalization of 
liquid pressure quite analogous to the use of the Eustach- 
ian tubes in equalizing air pressure. 
The fact that in man and many mammals a nystagmus 
can be caused by irrigating the auditory canal with hot 
or cold water and that the character of this nystagmus 
differs for different positions of the head can be explained 
perfectly without assuming the action of currents in the 
canals. If the temperature difference can cause convec- 
tion currents in the internal ear under the conditions 
existing in such an experiment, as the work of Maier and 
Lion seems to make probable, it is certainly reasonable 
to suppose that the effect would be far greater in the 
relatively large mass of liquid in the vestibule than in 116 
LABYRINTH AND EQUILIBRIUM 
the much smaller space in the canals. The difference of 
specific gravity which would be produced in the vestibule 
would cause changes in tension perfectly consistent in 
their effects with the tension changes produced by inertia, 
during a movement of rotation. These considerations 
would not in the least invalidate the diagnostic use which 
Barany has made of the phenomenon, but they do supply 
a reasonable explanation of its causation. 
2. The Dynamic Functions of the Otolith-organ 
We have seen that after removal of all the ampullae 
from both ears of the dogfish reactions occur to rotations 
in all planes except the horizontal, and this condition 
remains unchanged if, in addition, we then remove the 
sacculus otolith. In other words, compensatory move- 
ments to rotations around the longitudinal and transverse 
axes continue so long as the otolith of the recessus utriculi 
remains uninjured. 
The otolith of the recessus utriculi is, in the dogfish, 
an oval or nearly circular mass, 3 or 4 mm. in diameter, 
shaped like a planoconvex lens. Its convex surface rests 
upon the corresponding concave surface of the macula in 
the bottom of the recessus. I have described it as resting 
on the macula, but the relation of its edges to the mem- 
branous walls suggests the idea that it is in reality parti- 
ally suspended. To one who is actually performing these 
experiments it is a remarkably striking fact that all the 
functions performed by the ampullae of the vertical canals 
can also be performed by this one organ. In the case of 
the ampullae each one has a highly specialized function, MECHANISM OF DYNAMIC FUNCTIONS 
117 
responding to rotation in a single plane. The otolith- 
organ, on the contrary, responds to rotations in all planes 
except the horizontal. 
It was natural to suppose that the pressure of the 
otolith is the normal stimulus for the macula. A rotation 
of the head would shift the weight of the otolith; change of 
pressure upon the macula would excite impulses in a 
different set of hair-cells or nerve endings, and these 
impulses would give rise to the compensatory movements. 
This idea does not differ from the original conception of 
Goltz of the mode of action of the ampullae and canals, 
except in the unessential detail that in the one case the 
pressure is due to the weight of a liquid and in the other to 
the weight of a solid. (This is apparently the same kind 
of difference which exists between the otolith-containing 
otocyst of the crayfish and the otolithless otocyst of 
the crab; structures which appear to have identical 
functions.) 
Notwithstanding the fact that we had been compelled 
to abandon the pressure theory of the function of the 
ampullae, the pressure theory of otolith stimulation still 
seemed the most reasonable, until the stimulation experi- 
ments described in a preceding chapter showed that this, 
too, is untenable. 
When we apply light pressure to one side of the otolith 
of the recessus we excite a reaction which is just the 
opposite to that which is produced by inclining the head 
to the same side; thus, when we press on the right 
side of the otolith the right eye is depressed and the left 
eye is elevated; but, when we turn the right side of 
the head downward, the right eye is elevated and the left 
eye is depressed. At first sight it would appear that in 118 
LABYRINTH AND EQUILIBRIUM 
the two cases the mechanical conditions are alike, that 
in each an increase of pressure has been applied to the 
right side of the macula, and that we should expect the 
reactions to be alike in both. That the mechanical con- 
ditions are not alike, however, will be seen from the 
following considerations: 
The lower surface of the otolith has a curvature which 
is approximately spherical and the macula on which it 
rests forms a corresponding spherical depression. This 
could be represented by a convex lens, C, (Fig. 9, A.) lying 
in a concavity of equal curvature in the block, V. If we 
rotate V to the right, so as to depress its right side and 
elevate its left side, then C will tend, both on account 
of its weight and on account of its inertia, to be displaced 
with reference to V in the direction Ir. The rotation will 
thus produce a displacement to the right, and on account 
of the weight of C, an increased pressure in the region g. 
If, on the other hand, we allow V to remain in the hori- 
zontal position and we press down on the left side of 
C in the direction of the arrow, 0, (Fig. 9, B.) then C will 
be again displaced in the direction Ir, but the increase of 
pressure will be in the region b. Thus pressure on the 
left side of the otolith causes the same displacement as 
rotation to the right, while it causes the opposite pres- 
sure effect on the macula. It follows that the reaction 
in the living animal must be caused by the displacement or 
the change of the tension, and not directly by the change 
of pressure. 
It has been stated above that rotation would tend 
to produce a displacement of the otolith in two ways, 
namely, by the direct gravitational effect, or weight of 
the otolith, and also by its inertia. On account of the high MECHANISM OF DYNAMIC FUNCTIONS 
119 
specific gravity of the otolith attention seems mostly to 
have been centred on its weight rather than on its inertia, 
and hence the tendency has been to lay emphasis on its 
fitness to be a static organ. But greater weight of course 
confers on it greater inertia, and for this reason, it would 
seem better fitted than the liquid contents of the vestibule 
to be a dynamic organ. So far as I have been able to 
observe, there is little difference between them; an animal 
with vertical ampullae functional, but without otoliths, 
and an animal without vertical ampullae, but with the 
Fig. 9. 120 
LABYRINTH AND EQUILIBRIUM 
otolith-organ intact, react about alike to rotations around 
the longitudinal and transverse axes; both react in the 
usual fashion of a normal animal, but both react less 
promptly. The advantage of the greater specific gravity 
of the otolith seems to be just about balanced by the ad- 
vantage of the larger amount of lymph in the vestibule. 
A comparison of the conditions of excitation in the 
ampullas and in the otolith-organ shows that both depend 
upon the same principle; both are affected by displace- 
ments which could produce changes of tension. It is not 
unreasonable to suppose that these tension changes can 
give rise to impulses in a manner which may be analogous 
to the excitation of the vagus endings in the lungs. There 
is nothing to prove or disprove the idea that the bending 
of the hair-cells is a necessary step in the process. It is 
hard to see just how that hypothesis could be put to the 
test of direct experiment. There is nothing, so far as the 
writer can discover, to justify the assumption of localized 
functional differences in the different parts of a single 
crista or macula ; such an assumption is not needed, and 
should not be accepted unless supported by observed facts. CHAPTER IX 
THE MECHANISM OF THE STATIC FUNCTIONS 
OF THE LABYRINTH 
The facts presented in the preceding chapter show 
that the mechanisms of the ampullae and of the otolith- 
organs act on the same general principle in the production 
of compensatory movements. In each case a rotational 
movement of the head gives rise, through inertia, to a 
displacement of some structure in the labyrinth, and this 
in turn causes a change of tension upon the nerve endings. 
If the rotation is stopped without a return of the body to 
the normal posture, the eyes and fins tend to remain in 
the new position at which they have arrived, and thus the 
compensatory movement is followed by a compensatory 
position. The production of the compensatory movement 
is the dynamic function and the maintenance of the com- 
pensatory position the static function. The experiments 
of the writer have shown that, in the dogfish at least, 
both these functions can be performed both by the am- 
pullae and by the otoliths. There seems to be no necessity 
for the terms “statolith” and “statocyst.” 
It is hardly possible to conceive of the static function 
as anything more than a continuation of the effects pro- 
duced through the activity of the dynamic function. We 
have seen that a displacement with its consequent change 
of relative tensions is the stimulus which causes the move- 
ment. If the displacement is maintained for any length 
121 122 
LABYRINTH AND EQUILIBRIUM 
of time one may suppose that the stimulation will also 
be maintained. A static organ would differ from one 
which is only dynamic in the possession of a mechanism 
which would maintain the displacement that gives rise to 
the compensatory movement. It will be simpler to dis- 
cuss this first in the case of the otolith-organ. 
1. The Static Function of the Otolith. 
Delage71 was the first to show by actual experiment 
the static functions of the otoliths in invertebrates, and 
the proof of this was made still more complete by the 
remarkable experiment of Kreidl.127a The otocyst of the 
decapod crustacean, Palaemon is situated in the basal 
joint of the small antenna and is open to the exterior. 
When the animal molts, the lining of the otocyst is lost 
and with it the otoliths, or ear sand. In these animals 
the ear sand consists of particles of extraneous matter, 
usually grains of sand, which the Palaemon picks up 
with its forceps and places in the cavity of the otocyst. 
Kreidl put the young crustaceans at molting time, in 
dishes containing magnetic sand. After particles of this 
material had been placed by them in the otocysts, the 
animals could be caused to assume forced positions 
by placing the magnet near them, and when the posi- 
tion of the magnet was changed the forced position 
changed accordingly. 
The idea of Delage and of Kreidl was that the pressure 
of the otoliths upon the hair-cells acts as a constant 
stimulus. When the body is inclined so that the weight 
is shifted to a new position or acts in a new direction, 
the resulting pressure causes a different stimulus, affect- MECHANISM OF THE STATIC FUNCTIONS 
123 
ing the comparative degree of contraction of certain 
muscle groups; or, to state it in other words, the relative 
tonus of the groups of muscles concerned in maintaining 
the habitual posture of the animal is altered when, by 
a change of position of the body, the pressure of the oto- 
lith is shifted to a different set of hair-cells, and this 
alteration of tonus is seen in the compensatory position. 
In Kreidl’s experiment the pressure of the magnetic par- 
ticles was changed from the vertical to a direction which 
was the resultant of the force of gravity and the attrac- 
tive force of the magnet. 
The above conception needs only to be modified, on 
account of the results described in the preceding chapter, 
so as to recognize that it is not the pressure or weight 
which acts directly as the stimulus, but the changed rela- 
tion which I have spoken of as tension; this could be a 
stretching or a compression of nerve endings or a bending 
of the hair-cells. 
If this view is correct, the weight of the otolith comes 
into play as the means of retaining the displaced position 
which has been reached, and in this way the tension is 
maintained. When, for example, the head has been in- 
clined to one side and held so, the tension caused by the 
displacement which the otolith suffers on account of its 
weight, acts as a stimulus, and the otolith, on account 
of its weight likewise, remains in the new position. It 
is not merely a play on words to say that the weight or 
pressure of the otolith is not the stimulus, but only the 
means to continue the displacement which is the real 
stimulus. This is clear if one considers the effect of 
pressure applied to the edge of the otolith of the recessus, 124 
LABYRINTH AND EQUILIBRIUM 
where the increase of pressure is on one side of the otolith, 
but the displacement is to the opposite side, and where 
the compensatory movement is in the direction which 
corresponds to the displacement and not to the increase 
of pressure. 
2. The Static Function of the Ampulla 
The absence of otoliths in connection with the cristas 
has led to the a priori conception of the ampullae as only 
dynamic in function. The structural difference between 
the ampullae and the maculae, however, is closely paral-' 
leled by the difference between the otocysts of the crab, 
which possess no otoliths, and the otolith-containing 
otocysts of the crayfish and lobster. All of these appar-j 
ently possess both dynamic and static functions. It mayl 
be, however, that the vertebrate maculas, with their heavy! 
otoliths, and the otolith-organs of the crayfish are morel 
effective static organs than the vertebrate cristae and the I 
otocysts of the crab. No quantitative comparison of thej 
sort, so far as I know, has ever been reported. 
While an animal is undergoing rotation around a body! 
axis there is brought about, through inertia, a displace- 
ment of the contents of the vestibule, and this displace- 
ment and the consequent change of tension acts as a 
stimulus. If on cessation of the movement of rotation the 
contents of the vestibule returned at once to their orig- 
inal position, the stimulus would cease and the eyes would 
return to the primary position. If, however, the new 
position of the vestibular structures continued to exist 
after cessation of the movement the tension differences 
would also continue and the resulting stimuli would give! MECHANISM OF THE STATIC FUNCTIONS 
125 
rise to sustained forced position of the eyes; i.e., to the 
static effect. The latter condition could exist in case the 
specific gravity of the utricular tissues is greater than 
that of the lymph. This I have found to be the case. 
In most selachians the lymph of the vestibule is in free 
communication with the exterior sea water through the 
ductus endolymphaticus. It is reasonable therefore to 
expect that the density of the lymph would be practically 
equal to that of sea water. On this assumption I deter- 
mined the relative weights of the membranous labyrinth 
and sea water by dropping small bits of utricle, ampulla', 
and semicircular canals into a tall jar of sea water and 
saw that they all sank to the bottom. In order to be 
more certain, however, I succeeded in getting a sufficient 
amount of lymph from the ears of several fish killed at 
one time and dropped bits of the membranous labyrinth 
into it, with the result that they sank just as in sea water. 
Since the membranous labyrinth and the lymph differ 
in specific gravity it is evident that when the membrane 
is displaced to a relatively lower position, its weight will 
have the tendency to prevent its return to the original 
position in the cavity as long as the new body position is 
retained. I believe that this difference in weight, then, 
is the cause of the continued forced position in the absence 
of the otolith. 
It has been frequently stated that the stimulation of 
an ampulla gives rise only to a momentary movement, 
not to a sustained forced position, and that therefore its 
function can be only dynamic and not static. I have 
found the contrary to be very definitely true. Sustained 
mechanical stimulation of an ampulla, even the ampulla 
of a horizontal canal, causes a sustained forced position 126 
LABYRINTH AND EQUILIBRIUM 
of the two eyes; namely, a conjugate deviation to the side 
opposite to the stimulated ampulla. It is self-evident 
that in the ordinary functioning of the horizontal am- 
pulla, when the rotation to which it responds is in a hori- 
zontal plane, no changed relation to gravity can occur 
and hence the reaction to rotation cannot continue after 
the rotation has ceased. That the horizontal ampulla 
reacts to its normal stimulus by a response then is due 
only to its space relations, and not to a different kind 
of physiological function. Of course my experiments 
have demonstrated the ability of the other ampullae to 
produce sustained static effects. CHAPTER X 
THE TONUS EFFECTS OF THE AND 
OF THE MACULAE 
As the result of numerous investigations on the 
physiology of the labyrinth, Ewald arrived at his cele- 
brated tonus theory. He laid emphasis upon the dis- 
crimination of two parts, the auditory labyrinth and the 
tonus labyrinth, with distinct and very different func- 
tions. By many beautiful experiments he established, 
beyond question, the fact of an influence of the labyrinth 
upon the tonus of the many body muscles. His theoret- 
ical deductions were less happy. He assumed the pres- 
ence of continuous ciliary activity on the part of the hair- 
cells and this ciliary movement was in some way associ- 
ated with muscle tonus. His attention was almost wholly 
centred on the canals and ampullae; the otoliths were dis- 
missed with some a priori considerations. 
The equilibrium reactions were subordinate to the 
tonus effects. The ciliary activity of the hair-cells was 
augmented by an increased flow of endolymph in one di- 
rection -with a consequent increase of their tonic influence 
and hence a contraction of certain muscle groups, while 
an opposite flow of the current caused a checking of the 
movement of the hair-cells and an inhibition of tonus. 
We do not yet know what tonus really is nor how it is 
excited through the labyrinth. It is better to be content 
with the facts than to assume an unnecessary hypothesis. 
Ewald’s original conception of the tonus labyrinth ap- 
plied only to the canals and ampullae. Later his pupil, 
127 128 
LABYRINTH AND EQUILIBRIUM 
Ach,1 spoke also of an otolith tonus, but for its existence 
he gave no clear evidence. Through a series of pains- 
taking investigations carried on for more than a decade, 
Magnus and de Kleijn have drawn attention to a most 
instructive array of details concerning the tonus of the 
various muscle groups and the dependence of their tonus 
on various factors, chief among which is the influence 
of the labyrinth. They have shown, for example, that 
in the rabbit, when the disturbing and inhibitory effects 
of the cerebral hemispheres are excluded, definite tonus 
changes of the muscles of the neck, trunk, limbs and 
eyes take place with each change of position of the body. 
These tonus changes can be excited through different 
stimuli which normally cooperate and reenforce each 
other. Thus when the rabbit is placed upon its side, 
the labyrinth gives rise to excitations which cause an un- 
symmetrical distribution of tonus in the neck muscles so 
that the head is brought into a position of symmetry with 
reference to the lines of gravitational force. The altered 
position of the head is now asymmetrical with reference 
to the trunk; and the changed pressures and tensions in 
the joints or muscles of the neck act reflexly to bring 
about tonus changes in the muscles of the trunk and of 
the limbs in such a way as to raise the body into the nor- 
mal posture. In addition to these sources of afferent 
impulses contact stimuli arising from the side on which 
the body lies, tend also to cause the lifting of the head 
and, indirectly, the raising of the body into a position 
of symmetry. 
De Kleijn and Magnus have, on the basis of their 
observations, drawn a sharp distinction between reflexes 
which they consider to be excited by movement and those TONUS EFFECTS OF CRISTdE AND MACULAE 
129 
which are excited by position. This is essentially the 
old distinction of dynamic and static reactions. These 
authors have assumed that the dynamic reactions, excited 
by angular accelerations, have their origin in the cristae 
of the canals, and that the posture reflexes, on the other 
hand, depend upon the state of excitation of the maculae. 
According to this conception the tonus effects, assigned by 
Ewald to the ampullae, are chiefly dependent on the maculae 
with their otoliths. 
I have pointed out in a preceding chapter that the 
excitation which brings about a posture reflex must be 
dynamic as well as static; the muscles must cause a move- 
ment in order that there shall be a new position to sustain, 
and hence the difference between dynamic and static is 
only a difference of the presence or absence of a mech- 
anism for the continuance of the excitation and so of the 
state of muscular tonus. If this conception is correct we 
should expect to find that both cristae and maculae 
are capable of maintaining tonus. In case there is a real 
physiological difference in the kind of excitation aroused 
in the cristae and in the maculae, then, according to the 
conception of the latter as to the source of posture re- 
flexes, we should expect to find tonus effects only from 
the maculae. The certainty with which either ampullae 
or otoliths can be removed in the dogfish makes this ani- 
mal especially useful for the investigation of the question. 
When one labyrinth of the dogfish is completely de- 
stroyed, a difference of tonus on the two sides of the body 
is evidenced by the unsymmetrical position of the body, 
eyes and fins. Loeb143 saw that when the otoliths were 
removed from one ear, the position resembles that of an 
animal with the eighth nerve cut. Lee137 stated that 130 
LABYRINTH AND EQUILIBRIUM 
when the ampullar branches of the eighth nerve were sec- 
tioned on one side, an unsymmetrical position resulted; 
the body was inclined to the operated side, the eye on 
the operated side was depressed, and the eye on the 
other side elevated. He also saw in animals in which he 
had washed out the otoliths from one ear a similar asym- 
metrical position. If we may judge from these observa- 
tions, tonus effects which are not merely momentary but 
sustained, can originate in both the cristae and the 
maculae. I have investigated this matter, using the 
more exact extirpation methods described in chapters 
VI and VII. 
(1) When all three ampullae are removed from 
the right ear of a dogfish, the asymmetrical posi- 
tions of body, eyes, and fins are very similar to those 
assumed when the whole labyrinth has been destroyed; 
namely, the body is inclined to the right, the right eye 
is depressed and the left elevated, the dorsal fins are 
turned to the left, and the paired fins on the right are 
elevated while those on the left are depressed. In this 
condition, the animal’s activities seem little affected; it 
goes deeper or to the surface, turns to the right or to the 
left like a normal specimen, although the asymmetry 
is permanent. If now we remove the three ampullae from 
the left ear, the asymmetry disappears, and the condition 
is established which we have previously described. The 
animal maintains its equilibrium, rights itself when 
turned over in the water, and shows normal, but some- 
what weakened compensatory movements to rotations in 
all planes except the horizontal. These reactions show 
that the otolith-organs were not injured by the operation. TONUS EFFECTS OF CRISTS AND MACULAE 
131 
So long as the ampullae were present in one ear and miss- 
ing from the other, the asymmetrical placings of the eyes 
and fins gave evidence of a continuous tonic influence 
from the ampullae of the sound ear. 
(2) All the ampullae were removed from both ears of 
the dogfish and after making sure that no asymmetrical 
injury had been done to the labyrinths, as shown by the 
normal posture of the animal, the otoliths were removed 
from the right ear. The animal continued to maintain 
fairly well its equilibrium in water, righted itself when 
turned over, and showed hardly any noticeable asym- 
metry of position. This makes it probable, in fact almost 
certain, that the asymmetry seen by previous observers 
on washing out the otoliths from one ear was, in reality, 
due to the incidental injury to or destruction of the con- 
nections of the ampullae with the vestibular structures, 
and was due mainly or wholly to a lack of balance of 
ampullar, not of otolith, tonus effects. 
(3) We remove the ampullae from the right ear and 
observe the degree of asymmetry which follows the op- 
eration ; if we now complete the destruction of the right 
labyrinth by washing out the otoliths, the asymmetry is 
not noticeably, or but very slightly, increased. Unfor- 
tunately, no reliable method of determining quantita- 
tively the degree of asymmetry could be hit upon. 
(4) When the otoliths are removed from one ear with 
a minimum of injury to other structures the results are 
as described in 2, above. An asymmetrical position 
rarely occurs; but when it does it is probably in a speci- 
men whose utriculus and sacculus have been injured in 
the operation. 132 
LABYRINTH AND EQUILIBRIUM 
A comparison of the four classes of experiments just 
described makes it evident that the ampullse are the seat 
of continuous tonic influences. When the ampullse of 
one ear are lacking, a tonus difference appears on both 
sides of the body. It would be incorrect to assume, as 
has been done by many writers, that the cristse of each 
labyrinth have a predominating influence on one side of 
the body. As we have pointed out with reference to one- 
sided destruction of the whole labyrinth, the asymmetry 
is due to an influence on muscles on both sides of the body 
in such a way that the tonus of muscles of one side is 
decreased while that of the antagonists of the correspond- 
ing muscles on the other side of the body is also de- 
creased. When, for example, the ampullse are removed 
from the right ear, the muscles which lower the right pec- 
toral fin and the muscles which raise the left pectoral act 
more weakly than normal with the result that the fin on 
the right side is elevated and its fellow on the left 
is depressed. 
The question of the tonic effect of the otoliths is not 
so easy. At first sight it might seem that the almost 
complete absence of asymmetry after destruction of the 
otoliths in one ear shows a lack of tonic influence of the 
macula. It must be remembered, however, that displace- 
ments of the otolith of the one ear can cause compensa- 
tory movements in both directions; and that these move- 
ments, in the rays, and apparently also in the dogfish, 
are brought about alike by displacement of the otolith in 
either the right or the left ear. From this it would ap- 
pear that symmetrical tonus effects may be produced by 
the macula of the one ear. In this case an asymmetrical 
operation would not give rise to differences of tonus in TONUS EFFECTS OF CRISTA: AND MACULAE 
133 
the homologous muscle groups on the two sides of the 
body, and hence we could not by this method arrive at 
conclusions of otolith tonus in general. 
The above described experiments then give us positive 
evidence of the tonic influence of the ampullae but are not 
capable of solving the problem of otolith tonus. De 
Kleijn and Magnus121 have attempted to find the solution 
in an interesting manner. As a basis for their work a 
careful determination was made by de Burlet and 
Koster54 of the form and orientation of the otoliths of 
the ear of the rabbit. From the data thus obtained a 
model was constructed which could be used to show the 
position of each otolith and macula, or otolith membrane, 
for every position of the head. Assuming that the laby- 
rinth posture reflexes originated in the macula©, they stud- 
ied the tonus of various muscle groups for the different 
positions of the head and sought to correlate these with 
the orientation of the otoliths in each position. The fol- 
lowing will serve as an illustration of the method: 
In a decerebrated rabbit the extensor muscles of the 
limbs are in an especial state of tonus, decerebrate rigid- 
ity. This tonus depends upon, or is strongly influenced 
by, the labyrinth. It is found by rotating the body around 
the transverse axis that there is one and only one posi- 
tion of the animal at which the tonus of the limbs is 
maximal, namely, when the animal is in the position back 
downward with the line of the mouth-opening horizontal 
or elevated not more than 45 degrees. There is also an- 
other position in which the tonus is at a minimum, and 
this always differs from that of maximum tonus by 180 
degrees. Comparing these positions with the planes of 
the different otoliths no definite relations are found for 134 
LABYRINTH AND EQUILIBRIUM 
those of the sacculus. The otoliths of the utriculi, on 
the other hand, lie nearly in one plane, and are so situated 
that when the extensor tonus is at its minimum the oto- 
liths are horizontal and resting upon the maculae, when 
the tonus is at its maximum the otoliths are horizontal but 
hanging from the maculae. Assuming that the tonus 
changes are actually excited from the maculae, de Kleijn 
and Magnus conclude that it is not the pressure of the 
otolith which acts as the stimulus, but on the contrary the 
pull or tension which it exerts. This conclusion, reached 
by an indirect method, is in close accord with what has 
been proved by the writer through direct experiment 
upon the labyrinths of fishes. 
Applying a similar method of analysis through the 
study of maximal and minimal tonus for various muscle 
groups, eyes, limbs, neck, trunk, etc., these authors have 
assigned specific tonus functions to the otolith of the 
utriculus, to the larger portion of the saccular otolith, 
and to a smaller, angular portion of the same otolith, 
lying in a different plane. For all the positions of all 
the otoliths the conclusion was reached that the maximal 
excitation occurs when the macula is horizontal and the 
otolith hangs below it. 
When we compare the conclusions arrived at by de 
Kleijn and Magnus on the functions of the different oto- 
liths with the results obtained by the writer, a marked 
contrast appears in the role of the otoliths of sacculus 
and utriculus in the rabbit and in the fish; for in the fish 
all the position reflexes can be obtained from the otolith 
of the utriculus alone. The same may be true in the 
rabbit since the method of study through maximal and 
minimal tonus depends upon a priori considerations, and TONUS EFFECTS OF CRISTiE AND MACULdE 
135 
a priori reasoning has led to a multitude of misconcep- 
tions before in the study of labyrinth function. De Kleijn 
and Magnus have wisely remarked that their conclusions 
can be applied at present only to the rabbit. The rela- 
tions in other mammals remain to be worked out; while 
in animals with three otoliths in each ear, the individual 
functions must be different. We may agree with the last 
statement, only we should say “may be,” not “must 
be” different. CHAPTER XI 
NYSTAGMUS 
Some confusion exists in the use of terms descriptive 
of nystagmus. In nystagmus excited through the ear it 
is usually easy to determine that one phase of the oscilla- 
tion is identical with the compensatory motion which 
would result from the stimulation of the labyrinth. The 
other phase consists of a quick return to or toward the 
primary position. The former of these was called by 
Ewald the reaction phase and the latter the nystagmus 
phase. The compensatory phase is generally slower than 
the return, and for this reason the two movements are 
often spoken of as the slow component and the quick 
component respectively. Following Ewald’s use of the 
expression “nystagmus-phase,” it is common for writers 
to speak of the direction of the return movement as the 
direction of the nystagmus; thus, when a man is turned 
to the right in a revolving chair his eyes, during the rota- 
tion, make slow movements to the left and quick returns 
to the right; such a nystagmus is commonly, but not uni- 
formly, described as nystagmus to the right. The writer 
has no desire to urge the use of a different terminology, 
but believes that in this chapter confusion will be avoided 
by referring to the two constituent phases as the compen- 
satory and the return movements or phases. 
Since the direction of a compensatory movement de- 
pends upon the plane of rotation which calls it forth, the 
nystagmic movements must also depend upon the plane of 
136 NYSTAGMUS 
137 
the rotation, and hence may be horizontal, vertical, or 
rotary, or a resultant of any two of these. We must 
also distinguish between the nystagmus which occurs dur- 
ing a rotation and the after effect, the after-nystagmus, 
which occurs on cessation of the rotation. 
When a dogfish is rotated very slowly in the horizontal 
plane, a typical nystagmus may be seen; the eyes for a 
moment make the characteristic compensatory movement 
in the direction contrary to the rotation and then suddenly 
come back toward the primary position. If the rotation 
is made more rapid, only the compensatory movement 
occurs, the return movements do not appear. The same 
phenomena may also be seen in the pigeon and other ani- 
mals, only the rotation has to be more rapid in order 
to cause the omission of the return movement. From this 
it would appear that the two phases are not only physic- 
ally opposite but mutually inhibitory. When the laby- 
rinthine excitation is sufficiently powerful it overcomes 
the inhibitory effect of the impulse for the return move- 
ment and vice versa. 
The nystagmus of the eyes and the nystagmus of the 
head excited by rotation must be considered together. 
Fundamentally the two present the same phenomena. 
When we rotate a pigeon or a rabbit on the turntable, a 
marked compensatory position of the head, or a head- 
nystagmus, occurs. If the head is forcibly retained in 
the median position so that its movement is prevented, 
the eye-nystagmus becomes more rapid and intense. 
Bartels24 found that this is also true of very young infants. 
The compensatory phase is very evidently the kind of 
reaction which is excited through the labyrinth. The 
origin of the return movement is not so clear. It has 138 
LABYRINTH AND EQUILIBRIUM 
been supposed to be of cerebral origin but for reasons 
which are not very convincing. In a certain depth of 
narcosis the return movements are abolished while the 
compensatory phase continues to be exhibited. The same 
phenomenon is also seen in sleeping infants and in infants 
prematurely born. None of this, however, is proof. We 
do not know with precision the gradation of the effects 
of narcotics on the cerebral cortex, basal ganglia, brain 
stem and other parts of the nervous system; nor do we 
know any better the actual level of the brain which forms 
the line of physical demarcation between consciousness 
and unconsciousness; but we do know that sleep does not 
depend upon the cerebral hemispheres. On the other 
hand, Ewald75 had found that in the pigeon the nystagmus 
is not affected by the loss of the cerebral hemispheres, and 
Bauer and Leidler28 and Magnus156 found the same to be 
true in the mammal. It is, therefore, incorrect to speak 
of the return movement as a cortical reflex. 
Since the time of Flourens, who called attention to 
the general resemblance of the symptoms which follow 
injuries to the cerebellum and to the labyrinth, it has been 
rather common to assume that the effects of the laby- 
rinth are produced through the cerebellum. This view 
has been expressed in one form or another by Bechterew,31 
Luciani,147a Barany,18 and many others. This has been 
shown very definitely to be erroneous. Lange135 found 
that, in pigeons, the head nystagmus occurs in a perfectly 
characteristic way after destruction of the cerebellum. 
Moreover, the effects of labyrinth destruction and of 
cerebellar injuries have only a superficial resemblance; 
they differ in very essential details. Beyer and Lewand- NYSTAGMUS 
139 
owsky36 found that, in mammals, after extirpation of the 
cerebellum, the destruction of one labyrinth still produced 
the typical asymmetrical disturbances. Labyrinth ef- 
fects were neither produced nor prevented by loss of the 
cerebellum, nor did destruction of the labyrinths prevent 
the typical results of subsequent cerebellar injuries. 
Finally de Kleijn and Magnus117 have shown that the 
labyrinthine reflexes, including the nystagmus produced 
by rotation, occur normally in the absence of the 
cerebellum. 
In both the compensatory and the return phase the 
eye muscles conform to the principle of reciprocal inner- 
vation. While, for example, the rectus externus is ac- 
tively contracting, the rectus internus is not just pas- 
sively stretched, but it undergoes a relaxation which is 
as definite a physiological process as the contraction. 
This is well shown in the experiments of Bartels25 on the 
eye muscles of the rabbit. He arranged a small kymo- 
graph on the turntable so as to secure a graphic record 
both of the rotation-nystagmus and of the after-nystag- 
mus. The rectus externus and the rectus internus were 
dissected loose from their attachments to the eyeball 
and were connected by means of threads to two light 
levers. In this way the state of contraction or relaxation 
of each muscle was recorded independently of the other; 
the contraction of the one could not passively stretch 
the other. 
The curves obtained by Bartels show that during the 
compensatory phase the one muscle makes a relatively 
slow contraction while its antagonist relaxes at a cor- 
responding rate. When the contractions of the rectus 140 
LABYRINTH AND EQUILIBRIUM 
interims and externus of the left eye were recorded dur- 
ing rotation to the right, the externus slowly contracted 
and the internus relaxed during the compensatory phase. 
This was followed by the return movement which con- 
sisted of a quick contraction of the internus and a corre- 
spondingly quick relaxation of the externus. When the 
rotation was stopped the after-nystagmus showed, as 
might be expected, exactly the reverse relations. Bartel’s 
curves show that contraction of a muscle and relaxation 
of its antagonist keep pace very closely; a slow con- 
traction of the one is accompanied by a slow relaxation of 
the other, while a quick contraction is accompanied by 
a quick relaxation. 
We have seen that changes of tension or pressure on 
the nerve endings in the muscles or joints of the neck 
can excite movements of the eyes. This may give a hint 
as to the nature of the origin of the return movement. 
We cannot, however, ascribe the return movement to 
the direct effect of the stimulus in the neck; for the neck 
itself can give rise to an eye-nystagmus which like the 
nystagmus of labyrinthine origin is made up of a com- 
pensatory and a return phase and we have still to find 
the seat of the excitation for the return phase of this. 
It is not impossible that the excitations for the return 
phases in both are to be found in the muscles and tendons 
concerned in the movement. When we bend the head of a 
rabbit to the left the eyes make compensatory movements 
to the right. If the head is held in the forced position 
the eyes retain a compensatory position, although the 
amount of deviation is less than the extremes attained NYSTAGMUS 
141 
during the bending of the neck. Ewald75 described a 
similar phenomenon in the dog but with this striking 
difference, that the compensatory position of the eyes 
continues so long as the dog makes the effort to return the 
head to the line of the body. As soon as he gives up 
the effort the eyes come back to the primary position. 
One can feel with the fingers the moment of the relaxation 
and see that it coincides with the change in the position 
of the eyes. These facts seem to indicate that the stimuli 
are peripheral and arise from tension in the muscles and 
tendons rather than from pressure in the joints. 
Bartels25 is inclined to find the stimulus for the return 
movement of the eye-nystagmus in the eye muscles them- 
selves. Section of the branches of the trigeminal nerve 
through which afferent impulses from the orbit and bulb 
could come does not interfere with the course of the nys- 
tagmus. The nerves which supply the muscles of the 
eyeball have been supposed to be purely motor; but Tozer 
and Sherrington232 found that these nerves carry sen- 
sory fibres also to the eye muscles. Bartels believes that 
through these fibres pass the impulses which produce 
the return movement. 
There remains another possibility as to the origin 
of the return movement. Some portion of the central 
nervous system may be capable of exerting a tonic influ- 
ence the effect of which is to tend to keep the eyes in the 
primary position and to bring them back to this position 
when, through any stimulus, they are moved away from it. 
De Kleijn113 has presented the following evidence in sup- 
port of this view. The rectus externus muscle of the left 142 
LABYRINTH AND EQUILIBRIUM 
eye of a rabbit was detached from the eyeball and con- 
nected with a lever so that a graphic record could be 
obtained. The cerebral hemispheres of the animal were 
removed and the brain stem cut through just in front 
of the anterior corpora quadrigemina. The third and 
fourth cranial nerves of both sides and the sixth nerve 
of the right side were then sectioned. The application 
of caloric stimulation to the ear still caused the character- 
istic contractions of the rectus muscle, including the quick 
contractions which normally cause the return movement. 
The conditions of the experiment still left one pathway 
for the coming in of peripheral impulses; the sixth nerve 
of the left side which, of course, had to be spared to con- 
duct the motor impulses. De Kleijn sought to put the 
efferent fibres of this out of action by the injection of 
a one per cent, solution of novocain, which ordinarily 
paralyzes the sensory nerves at a time while the motor 
nerves are still functional. In this experiment, however, 
the two sets of impulses, compensatory and the return, 
disappeared at the same time. This result is indeed very 
suggestive, but it does not appear to the writer to fur- 
nish positive proof of the central origin of both sets 
of impulses. 
Though we may assume that movements of rotation 
are the physiological stimuli for the labyrinth, other stim- 
uli also can act upon it. Thus when a current of water 
some degrees warmer or colder than body temperature 
is caused to flow into and out of the external ear, so that 
the temperature of the tympanic region is made to be 
different from that of the neighboring parts, the so-called 
caloric reaction is produced; a conjugate deviation of the 
eyes or a nystagmus occurs, the direction of which de- NYSTAGMUS 
143 
pends upon the temperature of the water. When water 
is used which is warmer than the body, the compensatory 
phase is in the direction away from the stimulated side; 
when the water is colder than the body, the compensatory 
phase is toward the stimulated side. 
An attempt has been made to account for the caloric 
nystagmus on the basis of the tonic influences of the 
labyrinth, and the effects of heat and cold on the excita- 
bility of the sensory elements. If the sensitivity, and the 
tonic activity, of the labyrinth is increased by a rise of 
temperature, then the douching of the right ear with 
water should cause the influence of the right ear to exceed 
that of the left and produce a conjugate deviation of the 
eyes to the left; douching the right ear with cold water 
should reduce the sensitivity of the right ear below that 
of the left with the result that the effect of the left laby- 
rinth would predominate and a deviation to the right 
would occur. It only needs that the reflex apparatus 
which causes the return movement be active in order 
that a nystagmus should occur in accordance with the 
observed facts. 
The above explanation without further modification 
fails, however, to account for another very striking 
part of the phenomenon, namely, that while the caloric 
nystagmus is in progress a change in the position of the 
head causes a change in the direction of the nystagmus. 
Thus when the head of the human subject is tilted back- 
ward 60 degrees, bringing the horizontal canals into an 
approximately vertical plane, syringing the right ear with 
cold water causes a nystagmus in the plane of those 
canals, with the compensatory phase to the right. If now 
the head is inclined forward 120 degrees, the horizontal 144 
LABYRINTH AND EQUILIBRIUM 
canals are again in a vertical plane, but the compensatory 
stroke of the nystagmus is to the left. Barany15 and 
Briinings52 have attempted to account for the phenomena 
of caloric stimulation on the assumption that the applica- 
tion of heat and cold produces a change of density in the 
outer portions of the 
semicircular canals, 
and that this change of 
density causes, 
through the action of 
gravitation, currents 
in the canals which 
stimulate by deflection 
of the hair-cells. The 
change in the position 
of the head changes 
the direction of the 
current and hence the 
nature of the stimulus. 
Maier and Lion165 have shown that in a glass model of 
the size of the human canals, a perceptible and long last- 
ing current can be produced by temperature differences 
comparable to those used in douching the ear, and they 
believe that by this they have proved that similar cur- 
rents are the cause of the caloric stimulation. We have 
seen, however, that the normal excitation of the ampulla 
can occur when no current is possible in the canal. More- 
over, a difference in temperature sufficient to cause a 
current in a canal must produce still greater disturbance 
of equilibrium in the larger mass of liquid in the vestibule 
with consequent tension effects upon the membrane laby- 
rinth. The liquid in the vestibule is not wholly free, but 
Fig. 10.—Diagram to illustrate the principle of caloric 
stimulation. NYSTAGMUS 
145 
is partly enclosed in the ntricnlns and sacculus in snch a 
way that the heavier or lighter fluid must be held in one 
portion of the vestibule and by the difference of weight 
exert tension on the membranes. In this way a mechan- 
ical stimulus takes place exactly comparable to that which, 
as we have previously 
seen, is produced by 
rotation. By referring 
to Fig. 10, it can be 
seen that the appli- 
cation of heat to the 
parts represented by 
the right hand side of 
the figure would cause 
a decrease in density 
of the liquid in region 
U and this would give 
rise to changes in ten- 
sion acting in the di- 
rections indicated by the arrows. If cold instead of 
warmth were applied, the density would be increased in 
region U and the tension effects would be the reverse. 
Changing the position of the head must also change 
the direction of the pressure due to differences of density 
of the liquid in the vestibule. If, for example, the right 
hand side of the structures has been warmed, and the 
density and tension changes indicated in Fig. 10 have 
been produced, changing the position by 180 degrees 
(Fig. 11) must, through the influence of gravity, exactly 
reverse the relative tensions, with a consequent change 
in the application of the mechanical stimuli and in the 
nature of the resulting nystagmus. 
Fia. 11.—Diagram to explain effect of change of position 
01 the head on the result of caloric stimulation. LITERATURE* 
*Ach, N.: Ueber die Otolithenfunktion und den Labvrinthtonus. Arch, 
gea. Physiol., 1901, lxxxvi, 122. 
1 Alexander, G.: Ueber das Gehororgan einer unvolkommen albinotischen 
weissen Katze. Centr. f. Physiol., 1899, xiii, 477. 
1 Alexander, G.: Anatomisch-physiologische Untersuchungen an Tieren 
mit angeborenen Labyrinthanomalien. Wien. klin. Wochenschr. 
1902, 1375. 
‘Alexander, G.: Zur Frage der phylogenetischen vikarienenden Ausbil- 
dung der Sinnesorgane. Z. Pschol. u. Physiol. Sinnesorg., 1905, 
xxxviii, 24. 
6 Alexander, G., and Kreidl, A.: Zur Physiologie der Tanzmaus. Arch, 
ges. Physiol., 1900, lxxxii, 541. 
"Alexander, G., and Kreidl, A.: Die Labyrinthanomalien japanischer 
Tanzmause. Zentr. f. Physiol., 1902, xvi, 45. 
I Alexander, G., and Kreidl, A.: Ueber die Beziehungen der galvanischen 
Reaktion zu der angeborenen und erworbenen Taubstummheit. Arch, 
ges. Physiol., 1902, lxxxix, 475. 
8 Alexander, G., and Kreidl, A.: Anatomisch-physiologische Studien liber 
das Orhlabyrinth der Tanzmaus. Arch. ges. Physiol., 1902, lxxxviii, 509. 
0 Alexander, G., and Kreidl, A.: Zur Physiologie der neugeborenen Tanz- 
maus. Arch. ges. Physiol., 1902, lxxxviii, 564. 
10 Alexander, G., and Tandler, J.: Untersuchungen an kongenital tauben 
Hunden, Katzen und an jungen kongenital tauben Katzen. Arch. f. 
Ohrenheilk., 1905, lxvi, 161. 
II Babinski, M. J.: De l’influence des lesions de l’appareil auditif sur le 
vertige voltaique. Compt. rend. Soc. Biol., 1901, 77. 
13 Bach, L.: Ueber kiinstlich erzeugten Nystagmus bei normalen Individuen 
und bei Taubstummen. Arch. f. Augenheilk., 1894, xxx, 10. 
15 Baginsky, B.: Zur Frage iiber die zahl der Bogengiinge bei japanischen 
Tanzmausen. Centr. f. Physiol., 1902, xvi, 2. 
* With the exception of certain papers containing the fundamental 
observations, this list includes only literature which has appeared since 
Ewald’s monograph. Articles based wholly on clinical or psychological 
data have mostly been omitted. 
A complete bibliography of the labyrinth has been compiled by 
Dr. C. R. Griffith; it is hoped that this will soon be made available through 
its publication. 
146 LITERATURE 
147 
13 BArAny, R.: Untersuchungen iiber den vom Vestibularapparat des Ohres 
reflektorisch ausgelosten rhythmischen Nystagmus und seine Begleiter- 
scheinungen. Monatschr. f. Ohrenheillcunde, 1906, xl, 193. 
14 BArAny, R.: Augenwebegungen dureh Thoraxbewegungen ausgelost. 
Zentr. f. Physiol., 1906, xx, 298. 
15 BArAny, R.: Physiologie und Pathologie des Bogengangsapparates beim 
Menschen. Leipzig und Wien., 1907. 
18 BArAny, R.: Ueber einige Augen- und Halsmuskelreflexe bei Neuge- 
borenen. Acta- Oto- Laryngol., 1918, i, 97. 
17 BArAny, R., Reich, Z., and Rotiifeld, J.: Experimentelle Untersuch- 
ungen liber die vestibularen Reactionsbewegungen an Tieren, insbe- 
sondere im Zustande decerebrate Rigidity. Neurol. Zentr., 1912, 
xxxi, 1139. 
18 BArAny, R., and Wittmaack, K.: Funktionelle Priifung des Vestibu- 
larapparates. Verhandl. d. Deutsch. Otol. Ges., 1911, xx, 32. 
19 Bard, L.: Du role des centres nerveux dans la production du nystagmus 
thermique. J. Physiol, et Path, giner., 1918, xvii, 788. 
20 Bard, L.: Du mecanisme et de la signification du nystagmus voltaique. 
Ann. de med., 1918, v, 239. 
21 de Barenne, J. G. Dusser : Nachweiss das die Magnus-deKleinschen 
Reflexe bei den erwachsenen Katzen mit intaktem Zentral-nervensystem 
bei passiven und aktiven Kopf-resp. Halsbewegungen. Folia neuro-biol., 
1914, viii, 413. 
22 de Barenne, J. G. Dusser: Ueber eine neue Form von vestibularen 
reflexen beim Frosch. Psychiat. Neurol. Festb. C. Winkler, Amster- 
dam, 1918, 258. 
23 de Barenne, J. G. Dusser, and Magnus, R.: Die Stellreflexe bei der 
grosshirnlossen Katze und dem grosshirnlossen Hunde. Arch. ges. 
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24 Bartels, M.: Ueber Regulierung der Augenstellung durch den Ohrap- 
parat. Arch. f. Ophthalmol., 1910, lxxvi, 1. 
16 Bartels, M.: Ueber Regulierung der Augenstellung durch den Ohrap- 
parat. Mitt. iii. Kurven des Spannungszustandes einzelnes Augen- 
muskeln durch Ohrreflexe. Arch. f. Ophthalmol., 1911, lxxviii, 129. 
18 Bartels, M.: Ueber Regulierung der Augenstellung durch den Ohrap- 
parat. Mitt. iv. Die starkere Wirkung eines Ohrapparates auf das 
benachbarte Auge. Arch. f. Ophthalmol., 1911, lxxx, 209. 
17 Bartels, M.: Aufgaben der vergleichenden Physiologie der Augenbewe- 
gungen. Arch. f. Ophthalmol., 1920, ci, 299. 
28 Bauer, J., and Leidler, R.: Ueber den Einfluss der Ausschaltung ver- 
schiedener Hirnteile auf die vestibularen Augenreflexe. Arb. Neurol. 
Inst. Wien, 1911, xix, 155. 148 
LABYRINTH AND EQUILIBRIUM 
39 Baurmann, M.: Ueber reflektorisch ausgeloste Augenmuskelnbewegungen 
der Frosehlarven. Klin. Monatsbl. f. Augenheillc., 1921, lxvi, 393. 
30 Bechtebew, W.: Ergebnisse der Durchschneidung des N. Acusticus nebst 
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gleichgewichts. Arch. ges. Physiol., 1883, xxx, 312. 
31 Bechterew, W.: Ueber die Empfindungen, welche vermittelst der sog. 
Gleichgewichtsorgane wahrgenommen werden, und iiber die Bedeutung 
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stellungen. Arch. f. Physiol., 1896, 104. 
32Benjamins, C. E.: Otolitlien-verwijdering bij visschen. .Ned. Tijdschr. 
v. Geneesk., 1918, i, 1036. 
33 Benjamins, C. E.: Contribution a la connaissance des reflexes toniques 
des muscles de l’oeil. Arch. neer. Physiol., 1918, ii, 536. 
34 Betiie, A.: Ueber die Erlialtung des Gleichgewiclits. Biol. Centr., 1894, 
xiv, 563. 
36 Betiie, A.: Die Lokomotion der Haifische und ihre Bezieliungen zu den 
einzelnen Geliirnteilen und zum Labyrinth. Arch. ges. Physiol., 1899, 
lxxvi, 470. 
30 Beyer, H., and Lewandowsky, M.: Experimentelle Untersuchungen am 
Vestibularapparat von Siiugetieren. Arch. f. Physiol., 1906, 451. 
37 Bickee, A.: Ueber den Einfluss sensibler Nerven und der Labyrinthe auf 
die Bewegungen der Thiere. Arch. ges. Physiol., 1897, lxvii, 299. 
38 Biehl, K.: Ueber die intrakranielle Durchtrennung des Nervus vestibuli 
und deren Folge. Sitzungsb. Kaiserl. Akad. Wiss. Wien., 1900, cix, 
Abt. 3, 324. 
30 Biehl, K.: Beitrag zu der Lehre von der Beziehung zwischen Labyrinth 
und Auge. Arb. Wien. Neurol. Inst., 1907, xv, 71. 
40 Blau, A.: Experimentelle Untersuchungen liber den galvanisclien Nystag- 
mus. Zeitschr. f. Ohrenheilk., 1919, lxxviii, 40. 
41 Bonnier, P.: Sur les fonctions otolithiques. Compt. rend. Soc. Biol., 
1893, v, 187. 
42 Bonnier, P.: Rapports entre l’appareil ampullaire de l’oreille interne et 
les centres oculomoteurs. Compt. rend. Soc. Biol., 1895, x, 11. 
43 Bobbies, G. V. Til.: Experimental studies on the rotary and the caloric 
test in pigeons. Acta oto-laryngol., 1921, ii, 398. 
“Brabant, V. G.: Nouvelle recherches sur le nystagmus et le sens de 
r§quilibre. Arch. med. beiges., 1921, Ixxiv, 257. 
46 Breuer, J.: Ueber die Funktion der Bogengiinge des Ohrlabyrinths. 
Med. Jahrb., 1875. 
“Breuer, J.: Neue Versuche an den Ohrbogengangen. Arch. ges. Physiol., 
1S89, xliv, 135. LITERATURE 
149 
47 Breuer, J.: Ueber die Funktion der Otolithenapparate. Arch. ges. 
Physiol., 1891, xlviii, 195. 
48 Breuer, J.: Ueber die Bogengangsampullen. Zentr. f. Physiol., 1899/ 
1900, xiii, 750. 
40 Breuer, J.: Studien liber den Vestibularapparat. Sitzungsb. Wien. Kais. 
Akad. Math.-naturwiss. Kl., 1903, cxii, Abt. 3. 
60 Breuer, J. and Kreidl, A.: Ueber die scheinbare Drehung des Gesichts- 
feldes wahrend der Einwirkung einer Centrifugalkraft. Arch. ges. 
Physiol., 1898, lxx, 494. 
61 Broca, A.: Quelquea reflexions mecaniques snr l’organe de l’equilibration 
de l’oreille interne. Sens des forces et sens des couples. J. Physiol, 
et. Pathol, gener., 1920, xviii, 885. 
62 Brunings : Beitriige zur Theorie, Methodik und Klinik kalorimetrischen 
Funktionspriifung des Bogengangsapparates. Zeitschr. f. OhrenheilJc., 
1911, Ixiii, 20. 
83 Brunner, H.: Bemerkungen zum zentralen Mechanismus des vestibularen 
Nystagmus. Monatschr. f. Ohrenheilk., 1919, liii, 1. 
54 de Burlet, H. M., and Koster, J. J.: Zur Bestimmung des Stands der 
Bogengiinge und der Maculae acusticse in Kaninchenschadel. Arch. f. 
Anat., 1916, 59. 
65 Buys, E.: Beitrag zum Studium des Drehnystagmus. Monatschr. f. 
Ohrenheilk., 1913, xlvii, 675. 
58 Buys, E.: Contribution a l’etude du nystagmus de la rotation: duree et 
intensite due nystagmus uniforme. Compt. rend. Soc. Biol., 1920, 
lxxxiii, 1236. 
67 Buys, E.: La methode graphique et le nystagmus des univestibulaires. 
Scalpel, 1920, lxxiii, 629. 
68 Buys, E., and Coppez, H.: Traces graphiques du nystagmus. Arch. 
d’Ophth., 1909, xxix, 737. 
60 Camis, M.: L’ergogramme de la grenouille privee du labyrinthe. Arch, 
ital. de Biol., 1911, lv, 172. 
60 Camis, M.: Un methode operatoire pour la destruction des canaux demi- 
circulaires du chien. Arch. ital. Biol., 1911, lv, 180. 
61 Clark, G. P.: On the relation of the otocysts to equilibrium phenomena 
in Gelasimus pugilator and Platyonichus ocellatus. Jour. Physiol., 
1896, xix, 327. 
82 Cyon, E.: Les rapports physiologiques entre le nerf acoustique et 
l’appareil moteur de l’oeil. Compt. rend. Acad. Sci., 1876, lxxxii, 856. 
63 Cyon, E. Ueber Bogengiinge und Raumsinn. Arch. f. Physiol., 1897, 29. 
64 Cyon, E.: Die Funktionen des Ohrlabyrinthes. Arch. ges. Physiol., 
1898, lxxi, 72. 150 
LABYRINTH AND EQUILIBRIUM 
85 Cyon, E.: Ohrlabyrinth, Raumsinn und Orientirung. Arch. ges. Physiol., 
1900, lxxix, 211. 
68 Cyon, E.: Le sens de l’espace. Compt. rend. Acad. Bci., 1900. 
67 Cyon, E.: Neue Beobachtungen an den japanischen Tanzmausen. Arch. 
ges. Physiol., 1902, Ixxxix, 427. 
68 Cyon, E.: Beitrage zur Physiologie des Raumsinnes. Zwieter teil. 
Tauschungen in der Wahrnehmung der Richtung durch das Ohrlaby- 
rinth. Arch. ges. Physiol., 1902, xc, 585. 
69 Cyon, E.: Beitrage znr Physiologie des Raumsinnes. Dritter Teil. 
Arch. ges. Physiol., 1903, xciv, 139. 
70 Cyon, E.: Das Ohrlabyrinth als Organ der mathematischen Sinne fur 
Raum und Zeit. Berlin, 1908. 
71 Delage, Y.: Sur une fonction nouvelle des otocystes comme organes 
d’orientation locomotrice. Arch. Zodl. exper. et. gener., 1887, (2) v, 1. 
71a Deetjen, H.: Akustiche Stromungen der Perilymphe. Zeitschr. f. Biol., 
1900, xxxix, N. F. xxi, 159. 
73 Dreyfuss, R.: Experimenteller Beitrag zu der Lehre von den nicht 
akustischen Funktionen des Ohrlabyrinthes. Arch. ges. Physiol., 1900, 
lxxxi, 604. 
73 Dunlap, Knight: The nystagmus test and practice. J. Am. Med. Assn., 
1919, lxxiii, 54. 
74 Emanuel, G.: Ueber die Wirkung der Labyrinthe und des Thalamus 
opticus auf die Zugkurve des Frosches. Arch. ges. Physiol., 1903, 
xcix, 363. 
75 Ewald, J. R.: Physiologische Untersuchungen liber das Endorgan des 
Nervus octavus. Wiesbaden, 1892. 
78 Ewald, J. R.: Ueber die Beziehungen zwischen der excitablen Zone des 
Grosshirns und dem Ohrlabyrinth. Berl. klin. Wochenschrift., 1896, 
xxxiii, 929. 
77 Ewald, J. R.: Die Beziehungen des Tonuslabyrinthes zur Totenstarre 
und liber die Nystensche Reihe. Arch. ges. Physiol., 1896, lxiii, 521. 
78 Ewald, W. F.: Die Fortnahme des Ihiutigen Labyrinthes und ihre Folgen 
beim Flussaal Anguilla vulgaris. Arch. ges. Physiol., 1907, cxvi, 186. 
70 Fisher, L., and Babcock, H. L.: The reliability of the nystagmus test. 
J. Am. Med. Assn., 1919, lxxii, 779. 
80 Fisher, Homer G., and Muller, Henry R.: Unilateral destruction of 
the semicircular canals in cats. Am. J. Physiol., 1916, xli, 267. 
81 Flourens, P.: Recherches experimentales sur les proprietes et les fonc- 
tions du systfeme nerveux dans les animaux vertebres. Paris, 1842. 
83 Frohlicii, A.: Ueber den Einfluss der Zerstorung des Labyrinthes beim 
Seepferdchen, nebst einigen Bemerkungen liber das Schwimmen der 
Tiere. Arch. ges. Physiol., 1904, cvi, 84. LITERATURE 
151 
83 Gaglio, G.: Experiences sur l’anesthesie des canaux semicirculaires 
de l’oreille. Arch. ital. Biol., 1899, xxxi, 377. 
84 Gaglio, G.: Experiences sur l’anesthesie du labyrinthe de l’oreille chez 
les chiens de mer (Scyllium catulus). Arch. ital. Biol., 1903, 
xxxviii, 383. 
85 Garten, S.: Die Bedeutung unserer Sinne fiir die Orientiring im Luf- 
traum. Leipzig, 1917. 
88 Garten, S.: Ueber die Grundlagen unserer Orientierung im Kaume. 
Leipzig, 1920. 
87 Gemelli, A., Tessier, G., and Galli, A.: La percezione della posizione 
del nostro corpo e dei suoi spostamenti. Arch. ital. Psicol., 1920, i, 107. 
88 Gertz, H.: Ueber die kompensatorische Gegenwendung der Augen bei 
spontan bewegtem Kopfe. Zeitsclir. f. Sinnesphysiol., 1912-13, xlvii, 
420, and 1913-14, xlviii, 1. 
88 Gertz, H.: Zur Kentniss der Labyrinthfunktion. Nord. Med. Arkiv., 
1918, 1, 240. 
80 Gertz, H.: Sur le mecanisme central des mouveinents des yeux. Acta 
Med. Bcand., 1920, liii, 445. 
81 Gradinego, G.: Sur le fonctions du labyrinthe. Arch. ital. Biol., 1918, 
Ixviii, 205. 
83 Gray, Albert A.: The labyrinths of animals, including mammals, birds, 
reptiles, and amphibians. London, vol. i, 1907, vol. ii, 1908. 
83 Griffith, C. R.: The organic effects of repeated bodily rotation. Am. 
J. Exp. Psychol., 1920, iii, 15. 
84 Griffith, C. R.: Concerning the effect of repeated rotation upon nystag- 
mus. Laryngoscope, 1920, xxx, 22. 
85 Griffith, C. R.: The decrease of after nystagmus during repeated 
rotation. Laryngoscope, 1920, xxx, 129. 
88Gruenberg, B. C.: Compensatory motions and the semicircular canals. 
J. Exp. Zool., 1907, iv, 447. 
87 Henri, Victor : Effets de la destruction du labyrinth chez le serpent. 
Gompt. rend. Soc. Biol., 1898. 
88Hensen, V.: Wie steht es mit der Statocystenhypothese ? Arch. ges. 
Physiol., 1899, lxxiv, 43. 
89 Herter, K.: Untersuchungen ueber die nicht-akustichen Labyrinthfunk- 
tionen bei Anurenlarven. Zeitschr. allg. Physiol., 1921, xix, 335. 
wo jjyde, Ida H.: Zur Physiologie des Labyrinthes. iv. Mitt. Die Bezie- 
hungen des Grosshirns zum Tonuslabyrinth. Arch. ges. Physiol., 1895, 
lx, 492. 
ioi Hitzig, E.: Der Schwindel. In Nothnagels Handbuch. Berlin, 1898. 
183 van der Hoeve, J., and de Kleijn, A.: Tonische Labyrinthereflexe auf 
die Augen. Arch. ges. Physiol., 1917, clxix, 241. 152 
LABYRINTH AND EQUILIBRIUM 
i°3 jVY) A. C.: A comparative study of the relation of the cerebral cortex 
to labyrinthine nystagmus. Am. J. Physiol., 1919, xlix, 141. 
104 Ivy, A. C.: Experimental studies on the brain stem. II. A comparative 
study of the relation of the cerebral cortex to vestibular nystagmus. 
J. Comp. Neurol., 1919, xxi, 1. 
100 Holt, E. B.: On ocular nystagmus and the localization of sensory data 
during dizziness. Psychol. Rev., 1909, xvi, 377. 
100 Jensen, Paul: Ueber die galvanischen Schwindel. Arch. yes. Physiol., 
1896, lxiv, 182. 
107 Jones, Isaac H.: Equilibrium and Vertigo. Philadelphia, 1918. 
108 Kishi, K.: Das Gehororgan der sogenannten Tanzmaus. Zeitschr. wiss. 
Zool., 1902, lxxi, 457. 
1011 de Kleijn, A.: Zur Teclmik der Labyrinthextirpation und Labyrinth- 
aussclialtung bei Katzen. Arch. ges. Physiol., 1912, cxlv, 549. 
110 de Kleijn, A.: Zur Analyse der Folgezustande einseitiger Labyrinth- 
extirpation beim Frosch. Arch. ges. Physiol., 1914, clix, 218. 
111 de Kleijn, A.: Actions reflexes du labyrinthe et du cou sur les muscles 
de l’oeil. Arch. neer. Physiol., 1918, ii, 644. 
112 de Kleijn, A.: Tonische Labyrinth- und Halsreflexe auf die Augen. 
Arch. ges. Physiol., 1921, clxxxvi, 82. 
113 de Kleijn, A.: Experimente iiber die schnelle Phase des vestibuliiren 
Nystagmus beim Kaninchen. Versl. Afdeelung Naturlc. Konigl. AJcad. 
Wiss. Amsterdam, 1921, xxix, 1230. 
114 de Kleijn, A., and v. Leeuwen, W. Storm : Ueber vestibuliire Augen - 
reflexe. Arch. f. Ophthalmol., 1917, xciv, 316. 
115 de Kleijn, A., and Magnus, R.: Sympathicusliihmung durch Abkiihlung 
des Mittelohres beim Ausspritzen des Gehorganges der Katze mit 
kaltem Wasser. Arch. f. Ophthalmol., 1918, xcvi, 368. 
116 de Kleijn, A., and Magnus, R.: Tonische Labyrintliereflexe auf die 
Augenmuskeln. Arch. ges. Physiol., 1920, clxxviii, 179. 
117 de Kleijn, A., and Magnus, R.: Ueber die Unabhiingigkeit der Laby- 
rinthreflexe vom Kleinhirn und iiber die Lage der Zentren fiir die 
Labyrintlireflexe im Hirnstamm. Arch. ges. Physiol., 1920, clxxviii, 124. 
118 de Kleijn, A., and Magnus, R.: Beitriige zum Problem der Korper- 
stellung. iv. Mitt. Optische Stellreflexe bei Hund und Katze. Arch, 
ges. Physiol., 1920, clxxx, 291. 
119 de Kleijn, A., and Magnus, R.: Labyrintlireflexe auf Progressiv- 
bewegungen. Arch. ges. Physiol., 1921, clxxxvi, 39. 
120 de Kleijn, A., and Magnus, R.: Ueber die Funktion der Otolithen. 
ii. Mitt. Isolierte Otolithenaussclialtung bei Meerschweinchen. Arch, 
ges. Physiol., 1921, clxxxvi, 61. LITERATURE 
153 
131 de Kleijn, A., and Magnus, R.: Ueber die Funktion der Otolithen. 
i. Mitt. Otolithen bei den tonisehen Labyrinthreflexen. Arch. ges. 
Physiol., 1921, clxxxvi, 6. 
122 de Kleijn, A., and Vebsteegh, C. R. J.: Ueber den Einfhiss der Reizung 
der Nasenschleimhaut auf den vestibuliiren Nystagmus beim Kaninchen. 
Arch. f. Laryngol. und Rhinol., 1920, xxxiii, 437. 
133 de Kleijn, A., and Vebsteegh, C.: Ueber die Unabhiingigkeit des Dunkel- 
nystagmus der Hunde vom Labyrinth. Arch. f. Ophthalmol., 1920, 
ci, 228. 
134 Koenig, Ch. J.: Etude experimental des canaux semicirculaires. 
Paris, 1897. 
125 Koenig, Ch. J.: Ueber Kokainization der Bogengange. Zentr. f. Physiol., 
1898, xii, 694. 
120 Koranyi, A., and Loeb, Jacques: Ueber Storungen der kompensa- 
torischen und spontanen Bewegungen nach Verletzung des Grosshirns. 
Arch. ges. Physiol., 1891, xlviii, 423. 
12TKreidl, A.: Weitere Beitrage zur Physiologie des Ohrlabyrinthes. Sit- 
zungsb. k. k. Akad. TFtss. Math. nat. Kl., 1892, 3, Abt., ci., 469; 
1893, cii, 149. 
13SKreidl, A.: Die Funktion des Vestibularapparates. Ergebn. d. Physiol., 
1906, 11 Abt., v, 572. 
129 Kubo, Ino : Ueber die vom N. acusticus ausgelosten Augenbewegungen 
(besonders bei thermischen Reizungen). Arch. ges. Physiol., 1906, 
cxiv, 143. 
130 Kubo, Ino : Ueber die vom N. acusticus ausgelosten Augenbewegungen. 
II. Versuche an Fischen. Arch. ges. Physiol., 1906, cxv, 457. 
131 Kuffleb, O.: Ueber elektrische Reizung des Nervus octavus und seiner 
Endorgane beim Frosch. Arch. ges. Physiol., lxxxiii, 1901, 212. 
132 Laudenbach, J.: Zur Otolithenfrage. Arch. ges. Physiol., 1899, lxxvii, 311. 
133 Laudenbach, J. P.: De la relation entre le development des canaux 
semicirculaires et la coordination des mouvements chez les oisseaux. 
J. de Physiol, et. Pathol., 1899, i, 946. 
134 Laudenbach, J.: Zur Frage nach der physiologischen Bedeutung der 
Otolithen. Physiologiste Russe, 1905, iv, 64. 
135 Lange, B.: In wieweit sind die Symptome, welche nach Zerstorung des 
Kleinhirns beobachtet werden, auf Verletzungen des Acusticus zuriick- 
flihren? Arch. ges. Physiol., 1891, 1, 615. 
130 Lee, F. S.: Ueber den Gleichgewichtssinn. Gentr. f. Physiol., 1892, 
vi, 508. 
137 Lee, Fbedebic S.: A study of the sense of equilibrium in fishes. I. 
J. Physiol., 1894, xv, 311. 154 
LABYRINTH AND EQUILIBRIUM 
138 Lee, Frederic S.: A study of the sense of equilibrium in fishes. II. 
J. Physiol., 1894-5, xvii, 192. 
139 Lee, F. S.: The functions of the ear and the lateral line in fishes. Am. 
J. Physiol., 1898, i, 128. 
140 Levy, Lewis: Vestibular reactions in five hundred and forty-one aviators. 
J. Am. Med. Assn., 1919, lxxii, 716. 
141 Loeb, J.: Beitriige zur Physiologie des Grosshirns. Arch. ges. Physiol., 
1886, xxxix, 265. 
142 Loeb, J.: Die Orientirung der Tiere gegen der Scliwerkraft der Erde 
(Tierischen Geotropismus). Sitzungsb. Wurzb. Phys.- med. Ges., 1888. 
143 Loeb, J.: Ueber Geotropismus bei Tieren. Arch. ges. Physiol., 1891, 
xlix, 175. 
144 Loeb, J.: Ueber den Anteil des Hornerven an den nach Gehirnveletzung 
auftretenden Zwangsbewegungen, Zwangslagen, und assoziierten Stel- 
lungsanderungen der Bulbi und Extremitaten. Arch. ges. Physiol., 
1891, 1, 66. 
146 Loeb, J.: Ueber die Summation heliotropischer und geotropischer Wir- 
kungen bei den auf der Drehscheibe ausgelosten compensatorischen 
Kopfbewegungen. Arch. ges. Physiol., 1907, cxvi, 368. 
140 Loeb, J.: Forced movements, tropisms, and animal conduct. Philadelphia 
and London, 1918. 
147Luciani, L.: Das Kleinhirn. Leipzig, 1893. 
147a Luciani, L. Das Kleinhirn. Ergeb. Physiol., 1904, iii, 318. 
148 Lyon, E. P.: The functions of the otocyst. J. Comp. Neurol, and Psychol., 
1898, viii, 525. 
140 Lyon, E. P.: A contribution to the comparative physiology of compen- 
satory motions. Am. J. Physiol., 1899, iii, 86. 
150 Lyon, E. P.: Compensatory motions in fishes. Am. J. Physiol., 1900, 
iv, 77. 
151 Mach, E.: Physikalische Versuche fiber den Gleichgewichtssinn des 
Menschen. Sitzungsb. Alcad. Wiss. Wien., 1874, lxviii, 3 Abt., 124. 
162 Mach, E.: Versuche fiber den Gleichwewichtssinn. Sitzungsb. Alcad. 
Wiss. Wien. Math.- nat. Kl., 1874, lxix, 2 Abt., 121. 
153 Mach, E.: Grundlinien der Lehre von den Bewegungsempfindungen. 
Leipzig, 1875. 
104 Macii, E.: Beitriige zur Analyse der Empfindungen. Jena, 1886. 
155 Magnus, R.: Welclie Teile des Zentralnervensystems miissen ffir das 
Zustandekommen der tonischen Hals- und Labyrinthreflexe auf die 
Korpermuskulatur vorhanden sein? Arch. ges. Physiol., 1914, clix, 224. 
158 Magnus, R.: Beitrage zum Problem der Korperstellung. I. Mitt. Stell- 
reflexe beim Zwischenhirn- und Mittelhirnkaninchen. Arch. ges. 
Physiol., 1916, clxiii, 405. LITERATURE 
155 
157 Magnus, R.: Beitrage zum Problem der Korperstellung. II. Mitt. 
Stellreflexe beim Kaninclien nach einseitiger Labyrinthextirpation. 
Arch. ges. Physiol., 1919, clxxiv, 134. 
157a Magnus, R.: Tonische Hals- und Labyrinthreflexe auf die Korpermuskeln 
beim dezerebrierten Affen. Arch. neer. Physiol., 1918, ii, 484. 
158 Magnus, R., and de Kleijn, A.: Die Abhiingigkeit des Tonus der 
Extremitatsmuskeln von der Kopfstellung. Arch. ges. Physiol., 1912, 
cxlv, 455. 
150 Magnus, R., and de Kleijn, A.: Die Abhiingigkeit des Tonus der Nacken- 
muskeln von der Kopfstellung. Arch. ges. Physiol., 1912, cxlvii, 403. 
180 Magnus, R., and de Kleijn, A.: Die Abhangigkeit der Korperstellung 
vom Kopfstande beim normalen Kaninchen. Arch. ges. Physiol., 1913, 
cliv, 163. 
181 Magnus, R., and de Kleijn, A.: Analyse der Folgezustiinde einseitiger 
Labyrinthextirpation mit besonderer Berucksichtigung der rolle der 
tonischen Halsrellexe. Arch. ges. Physiol., 1913, cliv, 178. 
182 Magnus, R., and de Kleijn, A.: Weitere Beobachtungen liber Hals und 
Labyrinthreflexe auf die Gliedermuskeln des Menschen. Arch. ges. 
Physiol., 1915, clx, 429. 
183 Magnus, R., and Wolf, C. G. L.: Weitere Mitteilungen liber den Einfluss 
der Korperstellung auf den Gliedertonus. Arch. ges. Physiol., 1913, 
cxlix, 447. 
181 Magnus, R., and van Leuwen, W. S.: Die akuten und die dauerenden 
Folgen des Ausfalls der tonischen Hals- und Labyrinthreflexe. Arch, 
ges. Physiol., 1914, clix, 157. 
188 Maiek, Marcus, and Lion, Hans : Experimenteller Nachweis der Endo- 
lymphbewegung im Bogengangsapparat des Ohrlabyrinths bei adequater 
und kalorischer Reizung. Arch. ges. Physiol., 1921, clxxxvii, 47. 
18e Majewski, K.: Eine neue Methode der klinischen Nystagmographie. 
Arch. f. Ophthalmol., 1918, xcvi, 140. 
187 Mann, L.: Ueber die galvanische Vestibularreaktion. Neurol. Zentralb., 
1913, xxxi, 1356. 
188 v. Marikowsky, G. V.: Ueber den Zusammenhang zwischen der Musku- 
latur und dem Labyrinth. Arch. ges. Physiol., 1903, xcviii, 284. 
168 Maxwell, S. S.: Experiments on the functions of the internal ear. 
TJniv. Cal. Publ. Physiol., 1910, iv, 1. 
170 Maxwell, S. S.: On the exciting cause of compensatory movements. 
Am. J. Physiol., 1912, xxix, 367. 
171 Maxwell, S. S.: Labyrinth and equilibrium. I. A comparison of the 
effect of removal of the otolith organs and of the semicircular canals. 
J. Gen. Physiol., 1919, ii, 123. 156 
LABYRINTH AND EQUILIBRIUM 
172 Maxwell, S. S.: Labyrinth and equilibrium. II. The Mechanism of 
the dynamic functions of the labyrinth. J. Gen. Physiol., 1920, ii, 349. 
173 Maxwell, S. S.: Labyrinth and equilibrium. III. The mechanism of 
the static functions of the labyrinth. J. Gen. Physiol., 1920, iii, 157. 
174 Maxwell, S. S.: The equilibrium functions of the internal ear. Science, 
121, N. S., liii, 423. 
176 Maxwell, S. S.: Stereotropic reactions of the shovel-nosed ray, Rhino- 
batus productus. J. Gen. Physiol., 1921, iv, 11. 
170 Maxwell, S. S.: The stereotropism of the dogfish (Mustelus cali- 
fornicus) and its reversal through change of intensity of the stimulus. 
J. Gen. Physiol., 1921, iv, 19. 
177 Maxwell, S. S., Bukke, Una Lucille, and Reston, Constance: The 
effect of repeated rotation on the duration of after-nystagmus in the 
rabbit. Am. J. Physiol., 1922, lviii, 432. 
178 Merzbacher, L.: Ueber die Beziehungen der Sinnesorgane zu den Reflex- 
bewegungen des Frosches. Arch. ges. Physiol., 1900, lxxxi, 222. 
179 Mulder, W.: Quantitative betrekking tuschen prikkel in effect by het 
statisch organ. Utrecht, 1908. 
iso Mulder, W.: Analysis of the rotation reflex in the frog. Quart. J. Exp. 
Physiol., 1911, iv, 231. 
181 Muller, H. R., and Weed, L. H.: Notes on the falling reflex of cats. 
Am. J. Physiol., 1916, xl, 373. 
1SI Nagel, W. A.: Ueber kompensatorische Raddrehungen der Augen. 
Zeitschrf. Physiol, und Psychol, d. Sinnesorg., 1896, xii, 331. 
183 Nicolle, C., and Comte, C.: Du sens l’orientation chez un espfece de 
chauves souris (Vespertilia kuhli). Compt. rend. Soc. Biol.. 1906, 
lviii, 738. 
194 Ohm, J.: Ueber die Beziehungen der Augenmuskeln zu den Bogengangen 
beim Menschen und Kaninchen. Klin. Monatsbl. f. Augenheilk., 1921, 
lxii, 289. 
1,5 Oort, H.: Ueber ein Modell zur Demonstration der Maculae acusticae im 
Kaninchenschiidel. Arch. ges. Physiol., 1921, clxxxvi, 1. 
wPanse, R.: Zur vergleichenden Anatomie und Physiologie des Gleich- 
gewichtsorganes. Haugs Klin. Vortrag. a.d. Geb. d. Otol. u. Pharyng.- 
Rhinol., Jena, 1899, 183. 
188Panse, R.: Das Gleichgewichts und Gehororgan der japanischen Tanz- 
mause. Munch, med. Wochenschr., 1901, xlviii, 498. 
189 Parker, G. II.: Hearing and allied senses in fishes. U. S. Fish Com. 
Bull., 1902, 45. 
190 Parker, G. H.: The skin, lateral line organs and ear as organs of 
equilibration. Science, N. S., 1905, xxi, 265. LITERATURE 
157 
101 Parker, G. H.: Influence of the eyes, ears, and other allied sense organs 
on the movements of the dogfish (Mustelus cams, Mitchill). Bull. 
Bureau of Fisheries, 1909, xxix, 43. 
192 Pakkeb, G. H.: Structure and function of the ear of the squeteague. 
Bull. Bureau of Fisheries, 1910, xxviii, 1209. 
193 pIKE, p. g . effects of some lesions of the nervous system. Proc. 
Soc. Exp. Biol., 1916, xiii, 124. 
104 Pike, F. H.: The effect of decerebration upon the quick component of 
labyrinthine nystagmus. Proc. Soc. Exp. Biol., 1917, xiv, 75. 
195 Piper, H.: Aktionsstrome vom Labyrinth der Fische bei Schallreizung 
Arch. f. Physiol., 1910, Suppl., 1. 
loo poelak, J.: Ueber den “ galvanischen Schwindel ” bei Taubstummen 
und seine Beziehungen zur Funktion des Ohrlabyrinthes. Arch. ges. 
Physiol., 1893, liv, 188. 
lor Popp, H.: Die Wirkung von Warrne und Kiilte auf die einzelnen 
Ampullen des Ohrlabyrinths der Taube, festgestellt mit hilfe neuer 
Methoden. Zeitsch. f. Sinnesphysiol., 1912-13, xlvii, 352. 
198 Prince, A. L.: The position of the head after experimental removal of 
the otic labyrinth. Proc. Soc. Exp. Biol., 1916, xiii, 156. 
199 Prince, A. L.: On the compensation of the ocular and equilibrium dis- 
turbances which follow unilateral removal of the otic labyrinth. Proc. 
Soc. Exp. Biol., 1917, xiv, 133. 
200 Prince, A. L.: The effect of rotation and of unilateral removal of the 
otic labyrinth on the equilibrium and ocular reactions in kittens. 
Am. J. Physiol., 1917, xiii, 308. 
201 Prince, A. L.: On the compensation of ocular and equilibrium dis- 
turbances which follow unilateral removal of the otic labyrinth. Am. 
J. Physiol., 1919, xlix, 130. 
202 Prince, A. L.: Observations on the physiology of the otic labyrinth. 
Proc. Soc. Exp. Biol., 1920, xvii, 202. 
203 Quix, F. H.: Experimenten over de Functie van het Labyrinth bij 
Haaien. Tijdschr. nederl. dierk. Vereen., 1903, (2) 35. 
204 Quix, F. H.: Angeborene Labyrinthanomalien bei Tieren. Centr. f. 
Ohrenheilk, 1907, 291. 
205 Quix, F. H.: Labyrinthanomalien und Erscheinungen bei Tanzmliuse. 
Centr. f. Ohrenheilk., 1907, v, 327. 
200 Quix, F. H.: La R61e des otolithes dans les mouvements spontanes des 
animaux pendant le saut et la chute. Compt. rend. Acad. Sci., 1921, 
clxxiii, 864. 
207 Rawitz, B.: GehOrorgane und Gehirn eines weissen Hundes mit blauen 
Augen. Schwalbes Morph. Arb., 1896, vi, 545. 158 
LABYRINTH AND*; EQUILIBRIUM 
208 Rawitz, B.: Das gehororgan der japanisehen Tanzmause. Arch. f. 
Physiol., 1899, 236. 
209 Rawitz, B.: Neue Beobachtungen iiber das Gehororgan der japanisehen 
Tanzmause. Arch. f. Physiol., Suppl., 1901, 171. 
210 Rawitz, B.: Noch einmal die Bogengangsfrage bei japanisehen Tanz- 
mause. Centr. f. Physiol., 1902, xvi, 42. 
211 Rawitz, B.: Ueber den Bogengangsapparat der Purzeltauben. Arch. f. 
Physiol., 1903, 105. 
212 Rejto, A.: On the origin of the quick phase of the vestibular nystagmus. 
J. Laryngol., Rhinol. and Otol., 1920, xxxv, 103. 
213 Rejto, A.: On Ewald’s theory relating to the ampullofugal and ampul- 
lopetal endolympli currents. J. Laryngol., Rhinol. and Otol., 1920, 
xxxv, 176. 
214 Richard, D.: Untersuchungen iiber die Frage, ob Scliallreize adequate 
Reize fur den Vorhofbogengangsapparat sind. Zeitschr. f. Biol., 1916, 
lxvi, 479. 
215 Rogers, F. T.: Relations of the optic thalamus of the pigeon to the body 
temperature, nystagmus and spinal reflexes. Am. J. Physiol., 1918, 
xlv, 553. 
218 Roncato, A.: Influence du labyrinthe non-acoustique sur le developpment 
de l’ecorce cerebelleuse. Arch. ital. Biol., 1914, lxi, 93. 
217 Rossi, G.: Di un modello per studiare gli spostamenti della endolinfa 
nei eanali semicircolari. Arch, di Fisiol., 1914, xii, 349. 
213 Rossi, G.: Sulla viscosita della endolinfa e della perilinfa. Arch. di. 
Fisiol., 1914, xii, 415. 
219 Rothfeld, J.: Beitrag zur Kentniss der Abhangigkeit des Tonus der 
Extremitatenmuskeln von der Kopfstellung. Versuche mit Narkose. 
Arch. ges. Physiol., 1912, cxlviii, 564. 
220 Rothfeld, 5.: Ueber die Beeinflussung der vestibularen Reaktionsbewe- 
gungen durch experimentelle Verletzungen der Medulla oblongata. 
Bull. Acad. Sci., Krakau, 1914, 74. 
221 Schaefer, K. L.: Funktion und Funktionsentwickelung der Bogengange. 
Zeitschr. f. Psychol, u. Physiol, d. Sinnesorg., 1894, vii, 1. 
222 Shin- Izi- Ziba : Ueber die Beziehungen des dorsalen Langsbiindels zur 
labyrintaren Ophthalmostatik. Arch. f. Ohrenheillc., 1911, lxxxvi, 190. 
223 V. Stein, S.: Die Lehre von den Funktionen der einzelnen Teile des 
Ohrlabyrinths. Jena, 1894. 
224 Steinmann, P.: Ueber die Bedeutung des Labyrinthes und der Seiten- 
organe fur die Rheotaxis und die Beibehaltung der Bewegungsrichtung 
bei Fischen und Amphibien. Verhandl. d. naturforscli. Ges. Basel., 
1914, xxv. LITERATURE 
159 
225 Stern, L. W.: Die Literatur liber die nicht akustische Funktion des 
inneren Ohres. Arch. f. Ohrenheillc., 1895, xxxix, 248. 
226 Streeter, George L.: Some experiments on the developing ear vesicle 
of the tadpole with relation to equilibration. J. Exp. Zool., 1906, 
iii, 543. 
227 Streeter, George L.: Some factors in the development of the amphibian 
ear vesicle and further experiments on equilibration. J. Exp. Zool., 
1907, iv, 431. 
228 Streeter, George L.: Experimental evidence concerning the determi- 
nation of posture of the membranous labyrinth in amphibian embryos. 
J. Exp. Zool., 1914, xvi, 149. 
229 Strehl, H.: Beitrage zur Physiologie des inneren Ohres. Arch. ges. 
Physiol., 1895, lxi, 205. 
230 Thomas, A.: Du r6le du nerf la huitifeme paire dans le maintien de 
l’equilibre pendant les mouvements passifs. Compt. rend. Soc. Biol., 
1898, 1, 594. 
231 Thomas, A.: Sur la rapports anatomiques et fonctionels entre le laby- 
rinth et le cervelet.. Lompt. rend. Soc. Biol., 1898, 1, 725. 
232 Tozer, F. M., and Sherrington, C. S.: Receptors and afferents of the 
third, fourth and sixth cranial nerves. Proc. Roy. Soc., London, 1901, 
lxxxii, 450. 
233 Trendelenburg, W., and Kuiin, A.: Vergleichende Untersuchungen zur 
Physiologie des Ohrlabyrinthes der Reptilien. Arch. f. Physiol., 
1908, 160. 
234 Trifiletti, A.: Esperienze sui canali semicircolari dell’ orecchio nei 
colombi quale contributo alia fisio-patolog. detti canali. Gazet. di Osp. 
Milano, 1898, xix. 
238 Tullio, P.: Sulla Funzione dei canali semicircolari. III. La forma dell’ 
orecchio e le correnti acustiche endolabirintiche. Arch, di Fisiol., 
1917, xv, 245. 
238 Verworn, M.: Gleichgewicht und Otolithenorgan. Experimentelle Unter- 
suchungen. Arch. ges. Physiol., 1891, 1, 423. 
237 Wilson, J. Gordon, and Pike, F. H.: A note on the relation of the 
semicircular canals of the ear to the motor system. Proc. Soc. Exp. 
Biol., 1911, ix, 9. 
238 Wilson, J. Gordon, and Pike, F. H.: The effects of stimulation and 
extirpation of the labyrinth of the ear, and their relation to the motor 
system. Phil. Trans. Roy. Soc., London, 1912, cciii, 127. 
230 Wilson, J. Gordon, and Pike, F. H.: The effects of stimulation of the ear 
in the living animal. Proc. Soc. Exp. Biol., 1913, x, 81. 
240 Wilson, J. Gordon, and Pike, F. H.: Some considerations on the 
physiology of the otic labyrinth. Arch. Intern Med., 1914, xiv, 911. 160 
LABYRINTH AND EQUILIBRIUM 
241 Wilson, J. Gordon, and Pike, F. H.: The mechanism of labyrinthine 
nystagmus and its modification by lesions in the cerebellum and pons. 
Arch. Int. Med., 1915, xv, 31. 
242 Wilson, J. Gordon, and Pike, F. H.: The effects of some lesions of the 
nervous system. Proc. Soc. Exp. Biol., 1916, xiii, 124. 
243 Wallenberg, A.: Zentral Endstatten des Nervus octavus. Anat. Anzeig., 
1900, xvii, 102. 
244 Weil and, Waltjier: Hals- und Labyrinthreflexe beim Kaninchen; ihr 
Einfluss auf den Muskeltonus und die Stellung der Extremitiiten. 
Arch. ges. Physiol., 1912, cxlvii, 1. 
246 Wittmaack, K.: Ueber Veriinderungen im inneren Ohre nach Rotationen. 
Verhandl. Deutsch. Otol. Ges., 1909, xviii, 150. 
246 Yerkes, R. M.: The functions of the ear of the dancing mouse. Am. J. 
Physiol., 1907, xviii, XVIII. 
247 Zarnik, B.: Zur Kentniss der statischen Organe. Sitzungsb. pliys.-med. 
Ges., Wurzburg, 1915, 42. 
248 Zoth, 0.: Ein Beitrag zu den Beobachtungen und Versuchen an japan- 
ischen Tanzmausen. Arch. ges. Physiol., 1901, Ixxxvi, 147. 
249 Retzius, G.: Das Gehororgan der Wirbelthiere. Stockholm, 1882. INDEX 
Ach, 102, 128 
After-effects, 59 
After-nystagmus, 111, 137 
After-reactions, 18 
Ampullae, 69 
anatomical connections of, 112 
dynamic functions of, 99 
electrical stimulation of, 66 
extirpation of, 73 
mechanical stimulation of, 66, 70 
reactions after loss of, 75, 79 
stimulation of singly, 71 
Angular velocity and excitation, 105 
Bar&ny, 62, 138, 144 
Bartels, 18, 137, 139 
Bauer, 138 
Bechterew, 34 
Benjamins, 90, 101 
Beyer, 34, 138 
Breuer, 66, 93, 99 
Brown, 99 
Briinings, 144 
de Bur let, 133 
Caloric stimulation, ] 15, 142 
Centrifugal force, 102 ff. 
Cerebellum, 26, 29 
and nystagmus, 138 
Cerebrum and nystagmus, 138 
Circus motions, 27 
Clark, 83 
Compensatory motions, 13, 17 ff. 
caused only by rotation, 102 
dependent on direction of torsion, 
106 
Compensatory positions, 17 ff., 61 
Conjugate eye movements, 37 
Contact reactions, 39, 49 ft', 
of dogfisli, 53 
of mammals, 56 
of rhinobatus, 39 
reversibility of, 53 
Contact stimuli and muscle 
tonus, 128 
Cristse, 70, 112 
tonus influence of, 127, 130 
Cupula, 70, 99, 110 
v Cyon, 66 
Decerebrate rigidity, 133 
Decussation, 27 
Delage, 82, 122 
Destruction of both labyrinths, 42 ff. 
in Amphibians, 44 
in birds, 44 
in fishes, 42 
in mammals, 46 
in reptiles, 45 
Destruction of one labyrinth, 32 ff. 
Displacement of otolith, 97 
Dogfish, compensatory movement 
of, 21 ff. 
Dreyfuss, 34, 80 
Dynamic functions, 19, 83 
of ampullae, 99 
of otolith-organ, 116 
Ear sand, 122 
Emys, 46, 60 
Endolymph movements, 99, 108, 
109 ff. 
Equilibrium reactions, 14 
Ewald, 32, 44, 57, 67, 80, 127, 138, 
141 
Eye-movements, 39, 71 
161 162 
INDEX 
Flourens, 29, 66, 138 
Forced movements, 25 ff. 
from brain injuries, 29 
from postural reflexes, 28 
Forced positions, 25 ff. 
of eyes and fins, 35 
Geotropism, 13 
Goltz, 117 
Gray, 109 
Guinea pig, 80, 91 
Hair-cells, 70, 127 
Horizontal ampulla, 69 
destruction of, 80 
stimulation of, 71 
unique function of, 107 
Hoyt, 114 
Independent eye-movement, 38 ff. 
Inertia of endolymph, 114 
de Kleign, 34, 63, 90, 102, 128, 133, 
141 
Roster, 133 
Kreidl, 44, 82, 84, 122 
Kobo, 20, 70, 85, 92 
Kuhn, 18, 34, 45, 60 
Labyrinth anatomy, 67 ff. 
Lacerta, 60 
Lagena, 67 
Lange, 138 
Lee, 20, 43, 70, 72, 84, 92, 129 
Laudenbach, 44 
I.eidler, 138 
Leopard shark, 96 
Lewandowsky, 34, 138 
Lion, 109, 115, 144 
Literature, 146 
Loeb, 13, 18, 20, 27, 37, 58, 84, 106, 
129 
Luciani, 26, 138 
Lyon, 61, 74, 77, 100 
Mach, 99, 109 
Maculae, 69 
tonus influence of 127, 129, 131, 
132 
Mangus, 19, 34, 56, 90, 102, 128, 133, 
156 
Maier, 109, 115, 144 
Mechanism of dynamic functions, 
99 
of static functions, 121 
Models of canals, 109 
Muscle tonus, 33, 127 
from contact stimuli, 128 
from labyrinth, 127, 128 
in decerebrate rigidity, 133 
Nystagmus, 17, 26, 136 ff. 
after-nystagmus, 137 
compensatory phase, 136 
direction of, 136 
from retinal stimuli, 58, 60 
from bending of neck or body, 63 
horizontal, vertical and rotary, 
137 
of head, 100, 137 
Oblique axes, 72 
Orientation by contact stimuli, 77 
Otolith of recessus utriculi, 69 
displacement of 118 ff. 
method of stimulation, 95 
reactions from, 95 
Otoliths, 69, 86 
experiments on, 82 ff. 
planes of in rabbit, 133 
results of total extirpation, 84 
of extirpation of single 
otoliths, 85 
Otolith-organ 
stimulation in dogfish, 92 
in Rhinobatus, 96 
Otocysts, 82, 117 INDEX 
163 
Palcemon, 122 
Parker, 87, 101 
Phrynosoma, 14, 18, 100, 104 
Pike, 34, 47 
Pressure, 97, 100, 117 
Prince, 34 
Pays, otolith experiments on, 92, 
96 ff. 
Recessus utriculi, 67 
Reciprocal innervation, 41 
of eye muscles, 139 
Reflexes from joints and muscles, 61 
in dog fish, 61 
in rabbit, 62 
Retinal stimuli, 57 
in pigeon, 57 
in Phrynosoma, 58 
Return phase of nystagmus, 140 
Retractor bulbi, 38 
Retzius, 112 
Rhinobatus, 38, 96 
Righting reactions, 13, 14, 34, 48 
after loss of one labyrinth, 34 
Rolling movements, 29, 34 
Rossi, 109 
Rotations, 20 ff. 
Saccular otolith, 85, 87 
Sacculus, 67 
Selachian labyrinth, 67 
Semicircular canals, 65 
anatomy of, 66 
effect of cutting, 106 
experiments on, 65 
in bony fishes, 101 
stimulation of, 66 
Sherrington, 41, 141 
Skates, otolith experiments in, 92 
Static functions, 19, 83, 121, 122 
Statolith, 121 
Stereotropism of dogfish, 50 ff. 
Subjective method, 15 
Tension effects, 120, 134 
by rotation, 113 
in caloric stimulation, 116, 144 
Tonus, 25, 26, 33, 127, 128, 133 
Torsion and excitation, 102 ff. 
Tozer, 141 
Translatory movements, 100 
Treudelenburg, 18, 34, 45, 60 
Tropidonotus, 46 
Utricular otolith, 85 ff. 
Utriculus, 67 
Verworm, 82 
Wilson, 34, 47 
Wittmaack, 91