ABSTRACT
A cilium can be stopped by applying the tip of a glass microneedle during the effective stroke. The force required to stop the cilium has been measured by the author by the displacement of a flexible needle on the basis of its compliance. This force was expressed in terms of a torque, at the base of the cilium, which was 4× 10−7 dyne. cm. The second step would be to know the magnitude of the torque when the cilium is beating freely without constraint. Such a study would require a hydrodynamical treatment, as was given in the case of swimming spermatozoa (Taylor, 1951, 1952; Hancock, 1953; Gray & Hancock, 1955; Machin, 1958; Carlson, 1959).
The author is indebted to Mr Toshio Nakatsubo of The Olympus Optical Co. for the calibration.
This figure may become smaller (at the most by 30 %) if due corrections are made for bending of the cilium and for the current caused by small cilia (see Appendix).
