EDWAKD (;. BOETTIGER 



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Stimulated to maximal tetanus, the passive curve (BC') for the unstimulated 

 muscle. In the insect the muscle is held at the length at which maximum ten- 

 sion is obtained. Due to mechanical limitations in the articulation, the maxi- 

 mum shortening possible in the insect is only about 0.2 millimeter, though 

 greater shortening is shown by the preparations. The maximum shortening of 

 unrestricted muscle, however, is only about 12 per cent of the muscle length, 

 a value much smaller than that usually found in striated muscle but comparing 

 well with the behavior of the tymbal muscle (12). 



Fig. 2. Tension-length relations of fibrillar muscle. OA, the isometric tension of active 

 muscle as a function of length; BC, elastic behavior of the passive muscle. Length scale in 

 millimetersabove minimum muscle length. Loops (including bb', the steady state tension length 

 relation of vibrating muscle) are not actual records but show the general behavior of the 

 muscle. Large daslied loop is the i)ossible tension-length relation of the muscle in the intact 

 insect. 



In all these experiments there was no evidence of oscillatory behavior and 

 the muscle appeared to have no unique properties. However, for a self-excited 

 vibration one would not expect oscillation unless the system had an appreciable 

 period of vibration. The addition of a weight provided the necessary inertia 

 and the muscle, on stimulation, was then set into vibration. The oscillations 

 were recorded as dynamic tension-length diagrams by a slight change in the 

 setup. The mounting board was attached to a short piece of metal hinged at 

 one end to a fixed point. The metal strip provided the load. Additional weight 

 could be added to it as needed. By changing the friction in the hinge, an in- 

 crease in damping could be achieved. The tension in a small spring attached 



