468 Drs. G. F. Yeo and T. Cash. 



Table III. — Contrast between Free-weighted and After-weigbted 



Muscle. 



Decrease in Latency. 

 Free- weighted. After- weighted. 



0-25 of B.V.= L y .. 0-4-5 of D.Y.= T y 



0-05 „ .. 0-20 



0-05 „ .. 0-05 



0-10 „ .. o-o 



0-13 „ .. 0-05 



0-06 „ .. 0-05 



0-06 „ .. 0-05 



0-05 „ .. 0-20 



0-15 „ .. 0-05 



0- 10 „ .. 0-10 



1- 00 1-20 



The weigbt of tbe lever alone (abont 1 grm.) leaves many of tbe 

 fibres of tbe gastrocnemius not tensed, and this condition is closely 

 parallel to a mecbanical support of a beavier weight. If tbe weigbt 

 can be lifted without tbe co-operation of these fibres, tbe latency is 

 short, but sbould tbe addition of only 10 grms. require tbe tension of 

 many of them, tbe latency becomes markedly increased. Thus it is 

 tbat tbe greatest differences lie towards tbe commencement of tbe 

 scale of weigbt increment of a free-weighted muscle, and thus tbat tbe 

 after-weighted muscle sbows sucb greatly prolonged latencies at tbe 

 same period. 



We conclude tberefore — 



That the latency of a muscle witb supported weigbt is greater tban 

 with unsupported weigbt, and tbat tbe greatest variation between tbe 

 two occurs under tbe lighter weights. 



4. We bave referred at tbe commencement of tbis paper to the 

 influence of weigbt upon latency, and we bave shown subsequently 

 that tbe addition of 100 grms. causes a marked prolongation of tbis 

 period. As we desired as far as possible to avoid fatiguing the muscle, 

 we did not carry our weights, as a rule, beyond 100 grms., though a 

 few observations on fresh muscle weighted witb 200 grms. were made 

 in order to see in what manner the further weigbt acted. If we 

 examine tbe prolongation of tbe latency caused by increasing tbe 

 weigbt gradually from lever weigbt to 100 grms. we find tbat there is an 

 average increase of about "0063". 



In glancing over a number of observations and preparing tbeir aver- 

 ages, we found that the greatest influence exercised by any one weight- 

 difference (of a series of equal increments), was tbat resulting from 

 the suspension of the first 10 grms. from tbe lever ; this might cause an 



Weight increment. 



Lever 



to 



10 grms 



10 grins 





20 „ 



20 „ 



5 J 



30 „ 



30 „ 



J5 



40 „ 



40 „ 



? J 



50 „ 



50 „ 



5» 



60 „ 



60 „ 



JJ 



70 „ 



70 „ 



5) 



80 „ 



80 „ 



J5 



90 „ 



90 „ 



J5 



100 „ 



