BEHAVIOR: DANCE MOVEMENTS
The peculiarities of behavior of the dancing mouse are responsible alike
for the widespread interest which it has aroused, and for its name. In a
little book on fancy varieties of mice, in which there is much valuable
information concerning the care of the animals, one who styles himself "An
old fancier" writes thus of the behavior of the dancer: "I believe most
people have an idea that the waltzing is a stately dance executed on the
hind feet; this is not so. The performer simply goes round and round on
all fours, as fast as possible, the head pointing inwards. The giddy
whirl, after continuing for about a dozen turns, is then reversed in
direction, and each performance usually occupies from one to two minutes.
Whether it is voluntary or not, is difficult to determine, but I am
inclined to think the mouse can refrain if it wishes to do so, because I
never see them drop any food they may be eating, and begin to waltz in the
midst of their meal. The dance, if such it can be called, generally seizes
the mouse when it first emerges from its darkened sleeping place, and this
would lead one to suppose that the light conveys an impression of shock to
the brain, through the eyes, which disturbs the diseased centers and
starts the giddy gyrations. The mice can walk or run in a fairly straight
line when they wish to do so." Some of the old fancier's statements are
true, others are mere guesses. Those who have studied the mice carefully
will doubtless agree that he has not adequately described the various
forms of behavior of which they are capable. I have quoted his description
as an illustration of the weakness which is characteristic of most popular
accounts of animal behavior. It proves that it is not sufficient to watch
and then describe. The fact is that he who adequately describes the
behavior of any animal watches again and again under natural and
experimental conditions, and by prolonged and patient observation makes
himself so familiar with his subject that it comes to possess an
individuality as distinctive as that of his human companions. To the
casual observer the individuals of a strange race are almost
indistinguishable. Similarly, the behavior of all the animals of a
particular species seems the same to all except the observer who has
devoted himself whole-heartedly to the study of the subject and who has
thus become as familiar with their life of action as most of us are with
that of our fellow-men; for him each individual has its own unmistakable
characteristics.
I shall now describe the behavior of the dancing mouse in the light of the
results of the observation of scores of individuals for months at a time,
and of a large number of experiments. From time to time I shall refer to
points in the accounts of the subject previously given by Rawitz (25 p.
236), Cyon (9 p. 214), Alexander and Kreidl (1 p. 542), Zoth (31 p. 147),
and Kishi (21 p. 479).
The most striking features of the ordinary behavior of the dancer are
restlessness and movements in circles. The true dancer seldom runs in a
straight line for more than a few centimeters, although, contrary to the
statements of Rawitz and Cyon, it is able to do so on occasion for longer
distances. Even before it is old enough to escape from the nest it begins
to move in circles and to exhibit the quick, jerky head movements which
are characteristic of the race. At the age of three weeks it is able to
dance vigorously, and is incessantly active when not washing itself,
eating, or sleeping. According to Zoth (31 p. 149) the sense of sight and
especially the sense of smell of the dancer "seem to be keenly developed;
one can seldom remain for some time near the cage without one or another
of the animals growing lively, looking out of the nest, and beginning to
sniff around in the air (windet). They also seem to have strongly
developed cutaneous sensitiveness, and a considerable amount of curiosity,
if one may call it such, in common with their cousin, the white mouse." I
shall reserve what I have to say concerning the sense of sight for later
chapters. As for the sense of smell and the cutaneous sensitiveness, Zoth
is undoubtedly right in inferring from the behavior of the animal that it
is sensitive to certain odors and to changes in temperature. One of the
most noticeable and characteristic activities of the dancer is its
sniffing. Frequently in the midst of its dancing it stops suddenly, raises
its head so that the nose is pointed upward, as in the case of one of the
mice of the frontispiece, and remains in that position for a second or
two, as if sniffing the air.
The restlessness, the varied and almost incessant movements, and the
peculiar excitability of the dancer have repeatedly suggested to casual
observers the question, why does it move about in that aimless, useless
fashion? To this query Rawitz has replied that the lack of certain senses
compels the animal to strive through varied movements to use to the
greatest advantage those senses which it does possess. In Rawitz's opinion
the lack of hearing and orientation is compensated for by the continuous
use of sight and smell. The mouse runs about rapidly, moves its head from
side to side, and sniffs the air, in order that it may see and smell as
much as possible. In support of this interpretation of the restlessness of
the dancer, Rawitz states that he once observed similar behavior in an
albino dog which was deaf. This suggestion is not absurd, for it seems
quite probable that the dancer has to depend for the guidance of its
movements upon sense data which are relatively unimportant in the common
mouse, and that by its varied and restless movements it does in part make
up for its deficiency in sense equipment.
The dancing, waltzing, or circus course movement, as it is variously
known, varies in form from moment to moment. Now an individual moves its
head rapidly from side to side, perhaps backing a little at the same time,
now it spins around like a top with such speed that head and tail are
almost indistinguishable, now it runs in circles of from 5 cm. to 30 cm.
in diameter. If there are any objects in the cage about or through which
it may run, they are sure to direct the expression of activity. A tunnel
or a hole in a box calls forth endless repetitions of the act of passing
through. When two individuals are in the same cage, they frequently dance
together, sometimes moving in the same direction, sometimes in opposite
directions. Often, as one spins rapidly about a vertical axis, the other
runs around the first in small circles; or again, both may run in a small
circle in the same direction, so that their bodies form a living ring,
which, because of the rapidity of their movements, appears perfectly
continuous. The three most clearly distinguishable forms of dance are (1)
movement in circles with all the feet close together under the body, (2)
movement in circles, which vary in diameter from 5 cm. to 30 cm., with the
feet spread widely, and (3) movement now to the right, now to the left, in
figure eights ([Symbol: figure eight]). For convenience of reference
these types of dance may be called whirling, circling, and the figure
eight dance. Zoth, in an excellent account of the behavior of the dancer
(31 p. 156), describes "manège movements," "solo dances," and "centre
dances." Of these the first is whirling, the second one form of circling,
and the third the dancing of two individuals together in the manner
described above.
Both the whirling and the circling occur to the right (clockwise) and to
the left (anticlockwise). As certain observers have stated that it is
chiefly to the left and others that it is as frequently to the right, I
have attempted to get definite information concerning the matter by
observing a number of individuals systematically and at stated intervals.
My study of this subject soon convinced me that a true conception of the
facts cannot be got simply by noting the direction of turning from time to
time. I therefore planned and carried out a series of experimental
observations with twenty dancers, ten of each sex. One at a time these
individuals were placed in a glass jar, 26 cm. in diameter, and the number
of circle movements executed to the right and to the left during a period
of five minutes was determined as accurately as possible. This was
repeated at six hours of the day: 9 and 11 o'clock A.M., and 2, 4, 6, and
8 o'clock P.M. In order that habituation to the conditions under which the
counts of turning were made might hot influence the results for the group,
with ten individuals the morning counts were made first, and with the
others the afternoon counts. No attempt was made in the counting to keep a
separate record of the whirling and circling, although had it been
practicable this would have been desirable, for, as soon became evident to
the observer, some individuals which whirl in only one direction, circle
in both.
In Table 2 the results of the counts for the males are recorded; in Table
3 those for the females. Each number in the column headed "right" and
"left" indicates the total number of circles executed by a certain dancer
in a period of five minutes at the hour of the day named at the head of
the column. I may point out briefly the curiously interesting and entirely
unexpected new facts which this method of observation revealed to me.
First, there are three kinds of dancers: those which whirl almost
uniformly toward the right, those which whirl just as uniformly toward the
left, and those which whirl about as frequently in one direction as in the
other. To illustrate, No. 2 of Table 2 may be characterized as a "right
whirler," for he turned to the right almost uniformly. In the case of the
6 P.M. count, for example, he turned 285 times to the right, not once to
the left. No. 152, on the contrary, should be characterized as a "left
whirler," since he almost always turned to the left. From both of these
individuals No. 210 is distinguished by the fact that he turned now to the
left, now to the right. For him the name "mixed whirler" seems
appropriate.
Second, the amount of activity, as indicated by the number of times an
individual turns in a circle within five minutes, increases regularly and
rapidly from 9 A.M. to 8 P.M. According to the general averages which
appear at the bottom of Table 2, the average number of circles executed by
the males at 9 A.M. was 89.8 as compared with 207.1 at 8 P.M. In other
words, the mice dance more in the evening than during the day.
Third, as it appears in a comparison of the general averages of Tables 2
and 3, the females dance more than the males, under the conditions of
observation. At 9 A.M. the males circled 89.8 times, the females 151.0
times; at 8 P.M. the males circled 207.1 times, the females, 279.0 times.
Fourth, according to the averages for the six counts made with each
individual, as they appear in Table 4, the males turn somewhat more
frequently to the left than to the right (the difference, however, is not
sufficient to be considered significant); whereas, the females turn much
more frequently to the right than to the left. I do not wish to emphasize
the importance of this difference, for it is not improbable that counts
made with a larger number of animals, or even with another group of
twenty, would yield different results.
TABLE 2
NUMBER or WHIRLS TO THE RIGHT AND TO THE LEFT DURING
FIVE-MINUTE INTERVALS AS DETERMINED BY COUNTS MADE AT
SIX DIFFERENT HOURS, FOR EACH OF TEN MALE DANCERS
NUMBER 9 A.M 11 A.M. 2 P.M.
OF
ANIMAL RIGHT LEFT RIGHT LEFT RIGHT LEFT
2 11 2 23 4 194 1
30 20 1 134 1 109 2
34 2 16 2 48 4 92
36 194 21 180 11 143 65
152 7 48 3 171 6 79
156 63 8 53 9 27 6
210 3 9 7 41 225 21
220 168 105 39 43 47 5
410 2 67 10 27 8 103
420 15 142 5 214 16 238
Averages 48.5 41.3 45.6 56.9 77.9 61.2
Gen. Av. 89.8 102.5 139.1
NUMBER 4 P.M 6 P.M. 8 P.M.
OF
ANIMAL RIGHT LEFT RIGHT LEFT RIGHT LEFT
2 70 3 285 0 237 10
30 154 0 107 6 134 5
34 7 158 5 118 6 147
36 173 14 170 11 325 19
152 0 91 16 210 9 223
156 85 2 72 26 139 26
210 159 18 31 82 47 201
220 45 38 78 17 69 33
410 9 155 9 394 24 94
420 18 243 16 291 3 320
Averages 72.0 72.2 78.9 115.5 99.3 107.8
Gen. Av. 144.2 194.4 207.1
TABLE 3
NUMBER OF WHIRLS TO THE RIGHT AND TO THE LEFT DURING
FIVE-MINUTE INTERVALS AS DETERMINED BY COUNTS MADE AT
SIX DIFFERENT HOURS, FOR EACH OF TEN FEMALE DANCERS
NUMBER 9 A.M. 11 A.M. 2 P.M.
OF
ANIMAL RIGHT LEFT RIGHT LEFT RIGHT LEFT
29 9 18 17 30 7 22
33 287 0 329 1 352 3
35 48 15 198 46 208 14
151 13 88 7 75 3 167
157 57 6 50 45 53 12
211 218 21 31 55 66 5
215 67 216 33 105 37 226
225 46 39 72 49 143 44
415 23 0 156 0 34 3
425 43 296 12 201 12 210
Averages 81.1 69.9 90.5 60.7 91.5 70.6
Gen. Av. 151.0 151.2 162.1
NUMBER 4 P.M. 6 P.M. 8 P.M.
OF
ANIMAL RIGHT LEFT RIGHT LEFT RIGHT LEFT
29 33 114 31 36 45 99
33 436 7 408 3 364 2
35 279 6 165 24 353 10
151 3 8 2 285 2 217
157 52 15 19 125 51 104
211 190 7 86 31 67 250
215 15 292 45 336 150 232
225 133 86 48 39 177 81
415 268 3 437 7 382 8
425 12 242 19 210 4 192
Averages 142.1 78.0 126.0 109.6 159.5 119.5
Gen. Av. 220.1 235.6 279.0
The most important results of this statistical study of turning are the
demonstration of the existence of individual tendencies to turn in a
particular direction, and of the fact that the whirling increases in
amount from morning to evening.
In order to discover whether the distribution of the dancers among the
three groups which have been designated as right, left, and mixed whirlers
agrees in general with that indicated by Table 4 (approximately the same
number in each group) I have observed the direction of turning in the case
of one hundred dancers, including those of the foregoing tables, and have
classified them in accordance with their behavior as is indicated below.
RIGHT LEFT MIXED
WHIRLERS WHIRLERS WHIRLERS
Males 19 19 12
Females 12 23 15
Totals 31 42 27
The left whirlers occur in excess of both the right and the mixed
whirlers. This fact, together with the results which have already been
considered in connection with the counts of turning, suggests that a
tendency to whirl in a certain way may be inherited. I have examined my
data and conducted breeding experiments for the purpose of ascertaining
whether this is true. But as the results of this part of the investigation
more properly belong in a special chapter on the inheritance of behavior
(XVIII), the discussion of the subject may be closed for the present with
the statement that the preponderance of left whirlers indicated above is
due to a strong tendency to turn to the left which was exhibited by the
individuals of one line of descent.
TABLE 4
AVERAGE NUMBER OF WHIRLS TO THE RIGHT AND TO THE LEFT FOR
THE SIX INTERVALS OF TABLES 2 AND 3, WITH A CHARACTERIZATION
OF THE ANIMALS AS RIGHT WHIRLERS, LEFT WHIRLERS, OR
MIXED WHIRLERS.
AVERAGE NO. AVERAGE NO.
MALES AGE OF WHIRLS OF WHIRLS CHARACTERIZATION
2 12 mo. 136.7 3.3 Right whirler
30 2 mo. 109.7 2.5 Right whirler
34 2 mo. 4.3 96.5 Left whirler
36 2 mo. 197.5 23.5 Right whirler
152 6 mo. 6.8 137.0 Left whirler
156 1 mo. 73.2 12.8 Right whirler
210 3 mo. 78.7 62.0 Mixed whirler
220 4 mo. 74.3 40.2 Mixed whirler
410 3 mo. 10.3 139.0 Left whirler
420 3 mo. 12.2 241.3 Left whirler
Average 70.4 75.8 4 Right whirlers
4 Left whirlers
2 Mixed whirlers
FEMALES
29 2 mo. 23.7 53.2 Left whirler
33 2 mo. 362.7 2.7 Right whirler
35 2 mo. 208.5 19.2 Left whirler
151 6 mo. 5.0 140.0 Right whirler
157 1 mo. 47.0 51.2 Left whirler
211 3 mo. 109.7 61.5 Right whirler
215 3 mo. 57.8 234.5 Mixed whirler
225 4 mo. 103.2 56.3 Mixed whirler
415 3 mo. 216.7 3.5 Left whirler
425 3 mo. 17.0 225.2 Left whirler
Average 115.1 84.7 3 Right whirlers
4 Left whirlers
3 Mixed whirlers
The tendency of the dancer's activity to increase in amount toward
evening, which the results of Tables 2, 3, and 4 exhibit, demands further
consideration. Haacke (7 p. 337) and Kishi (21 p. 458) agree that the
dancing is most vigorous in the evening; but Alexander and Kreidl (i p.
544) assert, on the contrary, that the whirling of the individuals which
they observed bore no definite relation to the time of day and apparently
was not influenced in intensity thereby. Since the results of my own
observations contradict many of the statements made by the latter authors,
I suspect that they may not have watched their animals long enough to
discover the truth. The systematic records which I have kept indicate that
the mice remain quietly in their nests during the greater part of the day,
unless they are disturbed or come out to obtain food. Toward dusk they
emerge and dance with varying intensity for several hours. I have seldom
discovered one of them outside the nest between midnight and daylight. The
period of greatest activity is between 5 and 10 o'clock P.M.
Zoth states that he has observed the adult dancer whirl 79 times without
an instant's interruption, and I have counted as many as 110 whirls. It
seems rather absurd to say that an animal which can do this is weak.
Evidently the dancer is exceptionally strong in certain respects, although
it may be weak in others. Such general statements as are usually made fail
to do justice to the facts.
The supposition that light determines the periodicity of dancing is not
borne out by my observations, for I have found that the animals continue
to dance most vigorously toward evening, even when they are kept in a room
which is constantly illuminated. In all probability the periodicity of
activity is an expression of the habits of the mouse race rather than of
the immediate influence of any environmental condition. At some time in
the history of the dancer light probably did have an influence upon the
period of activity; but at present, as a result of the persistence of a
well-established racial tendency, the periodicity of dancing depends to a
greater extent upon internal than upon external conditions. During its
hours of quiescence it is possible to arouse the dancer and cause it to
whirl more or less vigorously by stimulating it strongly with intense
light, a weak electric current, or by placing two individuals which are
strangers to one another in the same cage; but the dancing thus induced is
seldom as rapid, varied, or as long-continued as that which is
characteristic of the evening hours.
One of the most interesting results of this study of the direction of
turning, from the observer's point of view, is the demonstration of the
fact that the truth concerning even so simple a matter as this can be
discovered only by long and careful observation. The casual observer of
the dancer gets an impression that it turns to the left more often than to
the right; he verifies his observation a few times and then asserts with
confidence that such is the truth about turning. That such a method of
getting knowledge of the behavior of the animal is worse than valueless is
clear in the light of the results of the systematic observations which
have just been reported. But, however important the progress which we may
have made by means of systematic observation of the phenomenon of turning,
it must not for one moment be supposed that the whole truth has been
discovered. Continued observation will undoubtedly reveal other important
facts concerning circling, whirling, and the periodicity of dancing, not
to mention the inheritance of peculiarities of dancing and the
significance of the various forms of activity.
CHAPTER IV
BEHAVIOR: EQUILIBRATION AND DIZZINESS
Quite as interesting and important as the general facts of behavior which
we have been considering are the results of experimental tests of the
dancer's ability to maintain its position under unusual spatial
conditions—to climb, cross narrow bridges, balance itself on high places.
Because of its tendency to circle and whirl, to dart hither and thither
rapidly and apparently without control of its movements, the study of the
mouse's ability to perform movements which demand accurate and delicate
muscular coördination, and to control its expressions of activity, are of
peculiar scientific interest.
That observers do not entirely agree as to the facts in this field is
apparent from the following comparison of the statements made by Cyon and
Zoth (31 p. 174).
Cyon states that the dancer
Cannot run in a straight line,
Cannot turn in a narrow space,
Cannot run backward,
Cannot run up an incline,
Cannot move about safely when above the ground, because of
fear and visual dizziness,
Can hear certain tones.
Zoth, on the contrary, maintains that the animal
Can run in a straight line for at least 20 cm.,
Can and repeatedly does turn in a narrow space,
Can run backward, for he has observed it do so,
Can run up an incline unless the surface is too smooth for it to
gain a foothold,
Can move about safely when above the ground, and gives no
signs of fear or dizziness,
Cannot hear, or at least gives no signs of sensitiveness to sounds.
Such contradictory statements (and unfortunately they are exceedingly
common) stimulated me to the repetition of many of the experiments which
have been made by other investigators to test the dancer's behavior in
unusual spatial relations. I shall state very briefly the general
conclusions to which these experiments have led me, with only sufficient
reference to methods and details of results to enable any one who wishes
to repeat the tests for himself to do so. For the sake of convenience of
presentation and clearness, the facts have been arranged under three
rubrics: equilibrational ability, dizziness, and behavior when blinded. To
our knowledge of each of these three groups of facts important
contributions have come from the experiments of Cyon (9 p. 220), Alexander
and Kreidl (1 p. 545), Zoth (31 p. 157), and Kishi (21 p. 482), although,
as has been stated, in many instances their results are so contradictory
as to demand reexamination. All in all, Zoth has given the most
satisfactory account of the behavior and motor capacity of the dancer.
If the surface upon which it is moving be sufficiently soft or rough to
furnish it a foothold, the dancer is able to run up or down inclines, even
though they be very steep, to cross narrow bridges, to balance itself at
heights of at least 30 cm. above the ground, and even to climb up and down
on rods, as is shown by certain of Zoth's photographs which are reproduced
in Figure 4. Zoth himself says, and in this I am able fully to agree with
him on the basis of my own observations, "that the power of equilibration
in the dancing mouse, is, in general, very complete. The seeming reduction
which appears under certain conditions should be attributed, not to visual
dizziness, but in part to excitability and restlessness, and in part to a
reduced muscular power" (31 p. 161). The dancer certainly has far less
grasping power than the common mouse, and is therefore at a disadvantage
in moving about on sloping surfaces. One evidence of this fact is the
character of the tracks made by the animal. Instead of raising its feet
from the substratum and placing them neatly, as does the common mouse
(Figure 5), it tends to shuffle along, dragging its toes and thus
producing on smoked paper such tracks as are seen in Figure 6. From my own
observations I am confident that these figures exaggerate the differences.
My dancers, unless they were greatly excited or moving under conditions of
stress, never dragged their toes as much as is indicated in Figure 6.
However, there can be no doubt that they possess less power of grasping
with their toes than do common mice. The animal is still further
incapacitated for movement on inclined surfaces or narrow places by its
tendency to move in circles and zigzags. The results of my own experiments
indicate that the timidity of the adult is greater than that of the
immature animal when it is placed on a bridge 1 or 2 cm. wide at a
distance of 20 cm. from the ground. Individuals three weeks old showed
less hesitation about trying to creep along such a narrow pathway than did
full-grown dancers three or four months old; and these, in turn, were not
so timid apparently as an individual one year old. But the younger animals
fell off more frequently than did the older ones.
[Illustration: FIGURE 4.—Zoth's photographs of dancers crossing bridges
and climbing rods. Reproduced from Pfluger's Archiv, Bd. 86.]
[Illustration: FIGURE 5—Tracks of common mouse Reproduced from Alexander
and Kreidl's figure in Pfluger's Archiv, Bd 82]
[Illustration: FIGURE 6—Tracks of dancing mouse Reproduced from Alexander
and Kreidl's figure in Pfluger's Archiv Bd 82]
Additional support for these statements concerning equilibrational ability
is furnished by the observations of Kishi (21 p. 482). He built a wooden
bridge 60 cm. long, 1 cm. wide at one end, and 1/2 cm. at the other, and
supported it at a height of 30 cm. above the ground by posts at the ends.
On this bridge ten dancers were tested. Some attempted to move sidewise,
others began to whirl and fell to the ground; only one of the ten
succeeded in getting all the way across the bridge on the first trial. The
second time he was tested this individual crossed the bridge and found the
post; and the third time he crossed the bridge and climbed down the post
directly. The others did not succeed in descending the post even after
having crossed the bridge safely, but, instead, finally fell to the floor
from awkwardness or exhaustion. On the basis of these and other similar
observations, Kishi says that the dancer possesses a fair degree of
ability to orient and balance itself.
Inasmuch as equilibration occurs similarly in darkness and in daylight,
Zoth thinks that there is neither visual dizziness nor fear of heights.
But it is doubtful whether he is right concerning fear. There is no doubt
in my mind, in view of the way the mice behave when placed on an elevated
surface, that they are timid; but this is due probably to the
uncomfortable and unusual position rather than to perception of their
distance from the ground. That they lack visual dizziness seems fairly
well established.
When rotated in a cyclostat[1] the dancer, unlike the common mouse, does
not exhibit symptoms of dizziness. The following vivid description of the
behavior of both kinds of mice when rotated is given by Alexander and
Kreidl (1 p. 548). I have not verified their observations.
[Footnote 1: An apparatus consisting of a glass cylinder with a mechanism
for turning it steadily and at different speeds about its vertical axis.]
The common mouse at first runs with increasing rapidity, as the speed of
rotation of the cyclostat cylinder is increased, in the direction opposite
to that of the cylinder itself. This continues until the speed of rotation
has increased to about 60 revolutions per minute. As the rotation becomes
still more rapid the mouse begins to crawl along the floor, its body
stretched out and clinging to the floor. At a speed of 250 revolutions per
minute it lies flat on the floor with its limbs extended obliquely to the
movement of rotation, and at times with its back bent against the axis of
the cylinder; in this position it makes but few and feeble efforts to
crawl forward. When the rotation is suddenly stopped, the animal pulls
itself together, remains for some seconds with extended limbs lying on the
floor, and then suddenly falls into convulsions and trembles violently.
After several attacks of this kind, cramps appear and, despite its
resistance, the animal is thrown about, even into the air at times, as if
by an external force. This picture of the position assumed during rapid
rotation, and of cramps after the cessation of rotation (the typical
picture of rotation dizziness), is repeated with great uniformity in the
case of the common mouse. Within fifteen minutes after being returned to
its cage the animal recovers from the effects of its experience. This
description of the symptoms of rotation dizziness in the common mouse
applies equally well to the blinded and the seeing animal.
In sharp contrast with the behavior of the common mouse in the cyclostat
is that of the dancer. As the cylinder begins to rotate the dancer runs
about as usual in circles, zigzags, and figure-eights. As the speed
becomes greater it naturally becomes increasingly difficult for the mouse
to do this, but it shows neither discomfort nor fear, as does the common
mouse. Finally the centrifugal force becomes so great that the animal is
thrown against the wall of the cylinder, where it remains quietly without
taking the oblique position. When the cyclostat is stopped suddenly, it
resumes its dance movements as if nothing unusual had occurred. It
exhibits no signs of dizziness, and apparently lacks the exhaustion which
is manifest in the case of other kinds of mice after several repetitions
of the experiment. The behavior of the blinded dancer is very similar.
If these statements are true, there is no reason to believe that the
dancer is capable of turning or rotation dizziness. If it were, its daily
life would be rendered very uncomfortable thereby, for its whirling would
constantly bring about the condition of dizziness. Apparently, then, the
dancer differs radically from most mammals in that it lacks visual and
rotational dizziness. In the next chapter we shall have to seek for the
structural causes for these facts.
The behavior of the blinded animal is so important in its bearings upon
the facts of orientation and equilibration that it must be considered in
connection with them. Cyon insists that the sense of vision is of great
importance to the dancer in orienting and equilibrating itself. When the
eyes are covered with cotton wads fastened by collodion, this writer
states (9 p. 223) that the mice behave as do pigeons and frogs whose
semicircular canals have been destroyed. They perform violent forced
movements, turn somersaults forward and backward, run up inclines and fall
over the edges, and roll over and over. In a word, they show precisely the
kind of disturbances of behavior which are characteristic of animals whose
semicircular canals are not functioning normally. Cyon, however, observed
that in certain dancers these peculiarities of behavior did not appear
when they were blinded, but that, instead, the animals gave no other
indication of being inconvenienced by the lack of sight than do common
white mice. This matter of individual differences we shall have to
consider more fully later.
No other observer agrees with Cyon in his conclusions concerning vision,
or, for that matter, in his statements concerning the behavior of the
blind dancer. Alexander and Kreidl (1 p. 550) contrast in the following
respects the behavior of the white mouse and that of the dancer when they
are blinded. The white mouse runs less securely and avoids obstacles less
certainly when deprived of vision. The dancer is much disturbed at first
by the shock caused by the removal of its eyes, or in case they are
covered, by the presence of the unusual obstruction. It soon recovers
sufficiently to become active, but it staggers, swerves often from side to
side, and frequently falls over. It moves clumsily and more slowly than
usual. Later these early indications of blindness may wholly disappear,
and only a slightly impaired ability to avoid obstacles remains.
It was noted by Kishi (21 p. 484), that the dancer when first blinded
trembles violently, jumps about wildly, and rolls over repeatedly, as Cyon
has stated; but Kishi believes that these disturbances of behavior are
temporary effects of the strong stimulation of certain reflex centers in
the nervous system. After having been blinded for only a few minutes the
dancers observed by him became fairly normal in their behavior. They moved
about somewhat more slowly than usually, especially when in a position
which required accurately coordinated movements. He therefore fully agrees
with Alexander and Kreidl in their conclusion that vision is not so
important for the guidance of the movements of the dancer as Cyon
believes.
In summing up the results of his investigation of this subject Zoth well
says (31 p. 168), "the orientation of the positions of the body with
respect to the horizontal and vertical planes seems to take place without
the assistance of the sense of sight." And, as I have already stated, this
excellent observer insists that the ability of the dancer to place its
body in a particular position (orientation), and its ability to maintain
its normal relations to its surroundings (equilibration) are excellent in
darkness and in daylight, provided only the substratum be not too smooth
for it to gain a foothold.
It must be admitted that the contradictions which exist in the several
accounts of the behavior of the dancer are too numerous and too serious to
be explained on the basis of careless observation. Only the assumption of
striking individual differences among dancers or of the existence of two
or more varieties of the animal suffices to account for the discrepancies.
That there are individual or variety differences is rendered practically
certain by the fact that Cyon himself worked with two groups of dancers
whose peculiarities he has described in detail, both as to structure and
behavior.
In the case of the first group, which consisted of three individuals, the
snout was more rounded than in the four individuals of the second group,
and there were present on the head three large tufts of bristly black hair
which gave the mice a very comical appearance. The animals of the second
group resembled more closely in appearance the common albino mouse. They
possessed the same pointed snout and long body, and only the presence of
black spots on the head and hips rendered them visibly different from the
albino mouse.
In behavior the individuals of these two groups differed strikingly. Those
of the first group danced frequently, violently, and in a variety of ways;
they seldom climbed on a vertical surface and when forced to move on an
incline they usually descended by sliding down backwards or sidewise
instead of turning around and coming down head first; they gave no signs
whatever of hearing sounds. Those of the second group, on the contrary,
danced very moderately and in few ways; they climbed the vertical walls of
their cage readily and willingly, and when descending from a height they
usually turned around and came down head first; two of the four evidently
heard certain sounds very well. No wonder that Cyon suggests the
possibility of a different origin! It seems not improbable that the
individuals of the second group were of mixed blood, possibly the result
of crosses with common mice.
As I shall hope to make clear in a subsequent discussion of the dancer's
peculiarities of behavior, in a chapter on individual differences, there
is no sufficient reason for doubting the general truth of Cyon's
description, although there is abundant evidence of his inaccuracy in
details. If, for the present, we accept without further evidence the
statement that there is more than one variety of dancer, we shall be able
to account for many of the apparent inaccuracies of description which are
to be found in the literature on the animal.
As a result of the examination of the facts which this chapter presents we
have discovered at least six important peculiarities of behavior of the
dancer which demand an explanation in terms of structure. These are: (1)
the dance movements—whirling, circling, figure-eights, zigzags; (2)
restlessness and the quick, jerky movements of the head; (3) lack of
responsiveness to sounds; (4) more or less pronounced deficiency in
orientational and equilibrational power; (5) lack of visual dizziness; (6)
lack of rotational dizziness.
Naturally enough, biologists from the first appearance of the dancing
mouse in Europe have been deeply interested in what we usually speak of as
the causes of these peculiarities of behavior. As a result, the structure
of those portions of the body which are supposed to have to do with the
control of movement, with the phenomena of dizziness, and with the ability
to respond to sounds, have been studied thoroughly. In the next chapter we
shall examine such facts of structure as have been discovered and attempt
to correlate them with the facts of behavior.
When the aim was to distill elementary phosphorus out of an organic
material, it did not matter whether this was fresh or putrified. For
obtaining lecithin out of egg yolk and similar materials, it was
essential to use it in fresh condition. Otherwise, enzymes would have
decomposed it. Through more recent work, four enzymes have been
separated, which act specifically in decomposing lecithin. Enzyme A
removes one fatty acid and leaves a complex residue, called
lysolecithin, intact. Enzyme B attacks this residue and splits off the
remaining fatty acid group from it, enzyme C liberates only the choline
from lecithin, and enzyme D opens lecithin at the ester bond between
glycerol and phosphoric acid. This is shown in the following diagram.
The generally similar behavior of these phosphate-and fat-containing
substances was emphasized by Ludwig Thudichum (1829-1901). He coined the
name phosphatides for this group of substances from seeds and
nerves.[29] His work on the phosphates in brain substance aroused
particular interest. When William Crookes drew his highly imaginative
picture of an “evolution” of the chemical elements, he put into it
“phosphorus for the brain, salt for the sea, clay for the solid
earth....”[30] But
phosphatides occur in many places of organisms, in
bacteria, in leaves and roots of plants, in fat and tissues of animals.
And where phosphatides are found, there are also enzymes that
specifically act on them. They are called phosphatases to imply that
they split the phosphatides. In addition, enzymes are present, which
transfer phosphate groups from one compound to another. They are more
abundant in seeds of high fat content than in the more starch-containing
seeds, but even potatoes and orange juice have phosphatases.[31]
Creatine Phosphate
Arginine phosphate
From these findings, together with what Oswald Schmiedeberg (1838-1921)
had established concerning the presence of four phosphate groups in the
molecule (1899), Robert Feulgen (1884-1955) constructed the following
scheme of a nucleic acid. Feulgen’s formula of 1918 is:
The exact position of phosphoric acid was established after long work
and verified by synthesis.[33]
This change of ATP was considered to be the main source of energy in
muscle contraction by Otto Meyerhof.[35] The corresponding derivatives
of guanine, cytosine, and uracil were also found, and they are active in
the temporary transfer of phosphoric acid groups in biological
processes.
[Pg 196]
[Pg 197]
The study of this function is the newest phase in the history of
phosphorus and represents the culmination of the previous efforts. This
newest phase developed out of an accidental discovery concerning one of
the oldest organic-chemical industries, the production of alcohol by the
fermentative action of yeast on sugar. A transition of carbohydrates
through phosphate compounds to the end products of the fermentation
process was found, and it gradually proved to be a kind of model for a
host of biological processes.
