The Dancing Mouse: A Study in Animal Behavior

by Robert Mearns Yerkes

Within a few months after the publication of Rawitz's first paper on the structure of the dancer's ear, another European investigator, Panse (23 and 24) published a short paper in which he claimed that previous to the appearance of Rawitz's paper he had sectioned and mounted ears of the common white mouse and the dancing mouse side by side, and, as the result of careful comparison, found such slight differences in structure that he considered them unworthy of mention. Panse, therefore, directly contradicts the statements made by Rawitz. In fact, he goes so far as to say that he found even greater differences between the ears of different white mice than between them and the ears of the dancer (23 p. 140).

In a somewhat later paper Panse (24 p. 498) expresses his belief that, since there are no peculiarities in the general form, sensory structures, or nerve supply of the ear of the dancer, which serve to explain the behavior of the animal, it is probable that there are unusual structural conditions in the brain, perhaps in the cerebellum, to which are due the dance movements and the deafness. The work of Panse is not very convincing, however, for his figures are poor and his descriptions meager; nevertheless, it casts a certain amount of doubt upon the reliability of the descriptions given by Rawitz.

[Illustration: FIGURE 8.—The membranous labyrinth of the dancer's ear. Type I. This figure, as well as 9 and 10, are reproduced from Rawitz's figures in the Archiv für Anatomie und Physiologie, Physiologische Abtheilung, 1899. C.s., anterior vertical canal; C.p., posterior vertical canal; C.e., horizontal canal; U., utriculus.]

The unfavorable light in which his report was placed by Panse's statements led Rawitz to examine additional preparations of the ear of the dancer. Again he used the reconstruction method. The mice whose ears he studied were sent to him by the physiologist Cyon.

As has been noted in Chapter IV, Cyon discovered certain differences in the structure and in the behavior of these dancers (11 p. 431), which led him to classify them in two groups. The individuals of one group climbed readily on the vertical walls of their cages and responded vigorously to sounds; those of the other group could not climb at all and gave no evidences of hearing. After he had completed his study of their behavior, Cyon killed the mice and sent their heads to Rawitz; but unfortunately those of the two groups became mixed, and Rawitz was unable to distinguish them. When he examined the structure of the ears of these mice, Rawitz did find, according to his accounts, two structural types between which very marked differences existed. Were it not for the carelessness which is indicated by the confusion of the materials, and the influence of Cyon's suggestion that there should be different structures to account for the differences in behavior, Rawitz's statements might be accepted. As matters stand there can be no doubt of individual differences in behavior, external appearance, and the structure of the ear; but until these have been correlated on the basis of thoroughgoing, careful observation, it is scarcely worth while to discuss their relations.

[Illustration: FIGURE 9.—The membranous labyrinth of the dancer's ear.
Type II.]

[Illustration: FIGURE 10.—The membranous labyrinth of the dancer's ear.
Type III.]

To his previous description of the conditions of the ear sacs, sense organs, and nerve elements of the dancer's ear, Rawitz adds nothing of importance in his second paper (26 p. 171). He merely reiterates his previous statements concerning the form of the canals, on the basis of his findings in the case of six additional dancers. Figures 8, 9, and 10 are reproduced from Rawitz to show the anatomical conditions which he claims that he found. As these figures indicate, the canals were found to be extremely variable, as well as unusual in form, and the sacs distorted. In the ears of some specimens there were only two canals, and in all cases they were more or less reduced in size, distorted, or grown together.

[Illustration: FIGURE 11.—Photograph of a wax model of the membranous labyrinth of the ear of the dancer. Reproduced from Baginsky's figure in the Centralblatt für Physiologie, Bd. 16.]

The work of Rawitz was unfavorably criticised by Alexander and Kreidl (2), Kishi (21), and Baginsky (4), as well as by Panse (23 and 24). To their criticisms Rawitz replied by insisting that the other investigators could not with right attack his statements because they had not used the reconstruction method. In order to test the value of this contention, and if possible settle the question of fact, Baginsky had a model of the ear of the dancer constructed by a skilled preparator (Herr Spitz) from sections which had been prepared by the best neurological methods. This model was made eighty times the size of the ear. It was then reduced in the process of photographic reproduction to sixteen times the natural size of the ear in the mouse. Figure 11 is a photograph of Baginsky's model. It shows beyond question the presence of three canals of the same general form and relations as those of the common mouse and of other mammals. Baginsky's paper is brief and to the point. His criticisms of the work of both Cyon and Rawitz are severe, but they are justified in all probability by the carelessness of these investigators in the fixation of their materials. Of the five skilled histologists who have examined the ear of the dancer, Rawitz alone found markedly abnormal canals. It is highly probable, therefore, that the canals in his preparations in some way became distorted before the ears were sectioned. He doubtless described accurately the conditions which he found, but the chances are that those conditions never existed in the living animals.