144 



Mr. Graham Brown. 



[Nov. 12, 



ihe flexor contraction, and a restitution of maintained tonus during flexor 

 relaxation, but there is no evident contraction in this phase. 



The movements occur in the two limbs. They are then related in such 

 a manner that flexion at one ankle occurs during relaxation of flexion at 

 the other ; and when the second limb exhibits flexion the first relaxes. 



It happens (although rarely) that sometimes the movements in the two 

 hind limbs are nearly synchronous, in the sense of being in the same direction 

 at the same time. 



Graphic records of the movements of the two ankles during this narcosis 

 progression demonstrate the relations of the movements in the two hind 

 limbs, and also the variations of their rates of rhythm. 



In a typical instance the curve traced by each foot is rhythmically 

 discontinuous (fig. 1). Each remains for intervals parallel with the abscissa — 

 corresponding with a posture of extension. Between these intervals each 

 curve describes a sharp rise and fall ( and — flexion). This movement may 

 be termed a " beat " ; and there is usually no pause at the top of a beat. The 

 movement of relaxation of flexion (or of extension) immediately succeeds 

 that of flexion contraction. Occasionally there is a slight pause at the top, 

 and the curve then remains parallel with the abscissa in a posture of 

 maintained flexion. The fall of a beat is usually a more rapid movement 

 than the rise. 



When the tracings of the two ankle movements are compared it is found 

 that the beat of one falls within the pause of the other The exact relation- 

 ship depends upon the rate of rhythm of the movements. 



Where the movements are slow the intervals may be of greater duration 

 than the beats. In such a case the top of a beat in one foot corresponds in 

 time to the mid-point of an interval in the other. The end of an interval 

 in one foot then overlaps the beginning of one in the other. Immediately 

 after each beat there is a short period during which both feet are in a state 

 of maintained extension. This is then terminated by the appearance of the 

 following beat at the other ankle. 



If the rate of rhythm is faster and the duration of the pauses exactly 

 equal to the duration of the beats then the termination of a beat at one 

 ankle is immediately followed by the commencement of a beat at the 

 other ; the termination of that by the commencement of a beat at the 

 first — and so on. 



With still faster rates the interval between beats at either ankle becomes 

 shortened. The apex of a beat at one ankle then falls mid-way in this 

 pause, but the commencement of the beat occurs at a point during the 

 relaxation phase of a beat at the other ankle. The relaxation phase of the 



