PERISTALTIC PROPULSION

We consider an ''organism'' containing a long, deformable tube, filled with water. A region of striction moves along the tube with a prescri bed velocity V. In a lubrication approximation, we determine the resul ting flow and pressure field in the tube; ultimately, we find the driv ing force F exerted by the fluid on the tube wall. F and V are of oppo site sign, independently of the detailed form of the peristaltic wave (striction, or swelling, or a mixed deformation with no overall change in the tube volume). We then extend these ideas to certain forms of p ropulsion via a contractile gel.