[The effect of cations on the contraction of myofibrils in the striated muscles of crabs].

Myofilaments have been prepared from crab legs according to a technique derived from that of F.J. Julian (1971). Tension variations have been recorded while the isolated fiber was submitted to the action of different saline solutions. As expected, it could be confirmed that the tension mainly depends on the content in Ca++ and Mg++ ions and in ATP. Our results have also shown that monovalent ions (Na+ and K+) when added separately, produce an important tension increase wheras their simultaneous addition or withdrawal modifies the tension only slightly.