On the Thrusting-Occurrence-Possibility by the Movement of the Scale Plates II

By the model experiment it was ascertained that it was possible to bring forth a thrusting-force through the movements of the scale-plates opening slowly and shutting quickly; but it seems that no examination has been done yet on the living fishes. This time, using carps, we made a few microscopic samples of sliced skins, to study the structure of scale-plates-cusps and to confirm the opening and shutting possibilities of the scale plates. Using 16mm camera, we filmed the surface of the fish-body (the series of scale plates) and visualized the flowing on its surface by the hydrogen-bubble method, and examined the thrusting-occurrence-possibility from the biological and physical points of view. In case of carps, the results obtained are as in the following： (1) Considering from the results obtained in the biological study it seemed that the scale-plates-cusps were not in independent and separated states, but were restricted by the tissues around the scale plates, therefore it was assumed that no wiggling of the fish-body caused the opening and shutting of the scale plates. (2) Considering from the results obtained in the physical study, it was ascertained that there was a series of slipping of scale plates along the fish-body-axis at the time when the fish was swimming. In case of the swimming fish with the body-length of 35cm, apart from the swimming speed, the value of the slipping of scale plates was noted to be constant (at the mean value 0.9mm) from the midship of the fish body to the back-end of the dorsalfin. By visualization, it was ascertained that the flowing on the fish-body-surface showed a sort of laminar flow but, owing to the visualization limit of the hydrogen-bubble method, it was almost impossible to confirm the flowing state upon the fish-body-surface under the high speed flowing. (3) In the experiment in which some amount of ink was dropped on the surface of the scale plates of the fish anesthetized on the dish, at the back-side of the scale-plate there was some attachment of blue-ink noted, both in the resting and in the wiggling states of the fish, which was in contradiction with the biologycal result described above. Therefore, it was assumed that concerning the possibility of thrusting-force-occurrence, further physical and biological studies of the epidermis would be necessary