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