MACHINERY OF INSECT FLIGHT 



139 



fibrillar muscle of a moth was subjected to the rapid changes in length. 

 At the completion of lengthening the tension was above the initial tension 

 at this length, while in the bee muscle it was bejow. Fibrillar and micro- 

 fibrillar muscle differ in their response to changes in length. 



T 

 L 



I ■! 1 1- 



r 



< — • — I — I — • — • — I — I — t-j 



Fig. 11. The effect of rapid transient changes in length. T is muscle tension and 

 L is muscle length. All marks on the length record show the instant of stimulation 

 at 60 per sec. A, isometric myogram of bumble-bee muscle, stimulation at 8 per sec. 

 to show summation of contraction ; B, response of unstimulated bee muscle stretched 

 to give about 40 gms passive tension ; C, same muscle stimulated to give active tension 

 of about 40 gm. ; D, flight muscle of a moth showing behavior of nonfibrillar muscle ; 

 E, bumble bee, successive records showing effect of decreasing interval between 

 release and stretch; F, wasp, Sphecius; G, bumble bee, Bombus. 



In E is a series of records in which the lengthening of the muscle is 

 delayed a variable time after the imposed shortening. At the completion of 

 .shortening, the tension falls slightly for about 10 msec and then rises, if it 

 is not relengthened, to a tension characteristic of the new shorter length. 

 This rise in tension after quick release is typical of muscle and even of the 

 glycerinated muscle model. Relengthening the muscle during the 10 msec. 

 before the tension starts to rise results in a somewhat greater active tension 



