Fractional Activity in Mammalian Reflex Phenomena. 137 



and the muscle was cut across a little below the point where its nerve 

 reached it. A fine silk thread connected it to the recording lever. This 

 was a fine heart lever pivoted on agate cups. 



A fine silk thread was placed loosely round the intact branch of the 

 motor nerve. Electrodes were placed on the great sciatic nerve, as far as 

 possible peripheral to the point where the motor nerve left it for tenuissimus. 

 All the exposed surface was then covered, but tenuissimus itself was left free 

 and uncovered. 



The reflex stimulus — faradic shocks, 30 per second — was applied for one 

 second every minute. The mechanical responses were recorded upon the 

 slow drum, but sometimes every 10th response was recorded on a faster 

 drum. The intensity of stimulation was varied by changing the angle 

 between primary and secondary coils degree by degree ; sometimes also by 

 sliding up the secondary millimetre by millimetre. In some cases the 

 strength of stimulation was increased from a minimum, sometimes it was 

 decreased from a maximum. Between stimuli the muscle was carefully 

 covered up. 



V. Results. 



The observations here described rarely lasted for less than an hour — during 

 which time a reflex contraction was recorded every minute. In these 

 circumstances it was found that a certain deterioration of the preparation 

 occurred — so that a direct muscular contraction was smaller at the end of 

 the series than was one taken with the same strength of stimulation at the 

 commencement of the series. 



If a series of reflex contractions commenced with strong stimuli, and was 

 continued with ever weaker stimuli, it is probable that a grading due to 

 muscular " fatigue " might add itself to the true reflex grading. There 

 might appear a larger number of " steps " than were actually conditioned by 

 a grading in the efferent nerve. 



In these experiments, therefore, the reflex stimuli were varied in the 

 reverse order — that is, starting with subminimal stimuli, and gradually 

 increasing the strength. Before and after each series a direct muscle 

 contraction was registered, and, as in every case the contraction was 

 smaller after the series, the number of different degrees of reflex muscular 

 contraction registered was possibly less than the actual number. That this 

 was so was also shown by the fact that, at the commencement of each 

 experiment, there was a greater range of reflex contractions in a " quick " 

 series (that is, one in which the graded stimuli were of widely differing 

 intensity) than in the subsequent " slow " ascending series of reflex 



VOL. LXXXVII. — B L 



