Zur Steuerung aktiver Bewegungen des Femur-Tibia-Gelenkes der Stabheuschrecke Carausius morosus

The introduction (A) is followed by parts B and C in which active movements of the tibia are recorded from intact legs and legs with cut receptor tendons (tendon of the femoral chordotonal organ). For this purpose the femur is fixed and then either the movement of the freely moving tibia is filmed or the force produced by the fixed tibia is measured directly. Leg movements caused by touching the abdomen (active movements) are faster than movements which are caused by stretching and releasing the femoral chordotonal organ in inactive animals. After an active movement the return to the starting-point is similar to that following a passive displacement: the speed of the backward movement is very low in intact legs, but relatively high in legs with cut receptor tendons. In intact legs the speed of the return to the starting-point shows a correlation between active and passive movements. A preliminary discussion of these movements is given in (D). It is followed in Section E by a description of the movements of the femur-tibia-joint of intact legs and legs with cut receptor tendons in free-walking animals. Cutting the receptor-tendon does not enlarge the amplitude very significantly. In Section F the receptor tendon is sinusoidally moved during active movements. The result of such an experiment upon inactive animals is quite different. No reaction can be observed during active movements at that phase position for which the response occures in inactive animals. But there is an alternative reaction with the same frequency as the stimulus. In active animals the amplitude of the reaction is very irregular, but normally larger than in inactive animals. Sometimes one reaction is omitted or there is more than one reaction per stimulus-cycle. The phase-shift is significantly larger than in inactive animals. In Section D a hypothesis for the control of active movements is discussed. According to this hypothesis the control system of the “Kniesehnenreflex” is switched off during active movements. The set-point of the system (the starting-point) is not altered by an active movement. The beginning of flexion and/or extension of the femur-tibia-joint and the maximum speed of the movements are at least partially influenced by the femoral chordotonal organ. The amount of this influence is variable.