STRETCH AND MUSCLE RESPONSE 
175 
kymograph was stopped and the electric current was shut oh 
in each case during the stretching, after which the weights were 
removed and the muscle was stimulated as before. In figure 2 
the contractions following the stretch with ten gram for ten 
minutes are practically twice as high as those preceding the stretch 
on the corresponding curves in figure 1 where there was no stretch. 
The increased height might be attributed to the recuperation dur- 
ing the time interval or rest, but in figure 6 where a ten minute 
rest occurred without any stretching the succeeding contractions 
were practically the same height as before, about the only change 
which is evident being a slight relaxation while the kymograph 
was stopped. It is interpreted that this increased sensitization 
is brought about by the stretching of the tissue. Little difference 
in the variation of tonus occurs, but the onset and progressive 
effects of fatigue are more definitely indicated than where there 
was no stretch. Figures 3, 4, and 5 also show this increase in 
sensitization due to the stretching. Figure 4 fits least well into 
the series, but taking all these series together the height of the 
contraction and the onset and progressive effects of fatigue are 
in proportion to the duration of the time of stretch. In the last 
of the series in figure 3, stimuli were introduced every twenty- 
five seconds which is equivalent to about twenty make and break 
shocks or about one-half the duration and strength of those just 
preceding. The corresponding contractions are proportional to 
the amount and duration of current used. Series 7 and 8 having 
twenty and thirty gram weights respectively, were stretched ten 
minutes each in order to attack this problem of stretch from 
another angle, and here again the initial sensitization and the 
onset and progress of fatigue are in proportion to the amount of 
stretch. Series 9, which was stretched for two hours with a ten 
gram weight in sodium chloride solution, was made to further 
analyze this increased sensitization property of stretched muscles. 
This series is directly comparable with series 5, the only variable 
being that instead of removing the ten gram weight after the two 
hours stretch it was allowed to remain and be lifted following the 
first three stimuli ; after which it was removed and the muscle 
stimulated as usual. The muscle contracted only about one- 
fourth the height of the corresponding contractions in series 5 
where the weight was removed. There is the immediate onset 
and progression of fatigue in the two cases which are practically 
the same. The height of the contractions following the removal 
of the weight are practically the same as the corresponding con- 
