THE MECHANISM OF BEAT 



155 



Gray worked out the sequence of bending moments about 

 the Hne X- Y on the assumption that the fibrils were distributed 

 as shown in Fig. 41b, that they contracted in this order, and that 



a. 



b. 



• Phase of cycle 



X 



3 



o 



t9 



*J 



C 

 V 



E 

 o 



E 



c 



t-i 



Phase of cycle 



-101- 



FiG. 42. Graphs illustrating a suggested contraction cycle in 

 the model shown in Fig. 41. a. The contraction cycle assumed 

 to take place in each peripheral fibril of the model, b. The 

 sequence of resultant bending moments about the line X-Y 

 in one cycle of contraction of the model (constructed using data 



from a) (from Gray, 1955). 



the contraction cycle of each individual fibril followed a sine wave 

 (Fig. 42a). Each cycle was divided into six parts, so that each 

 fibril was J cycle out of phase with each of its neighbours 



