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IOWA ACADEMY OF SCIENCE Vor. XXIX, 1922 
conditions. Hence each is considered typical for a given set of 
conditions. The muscle of each of the series 1 to 11, was stimu- 
lated before stretching in order to see that everything was in 
proper working order. The kymograph was then stopped, the 
electrical wires disconnected and the desired weight applied on 
the longer lever arm at an equal distance from the fulcrum as 
the end of the short lever arm. Thus the muscle was stretched 
without removing it from the chamber in which it was immersed. 
After the proper time interval for stretching had transpired 'the 
weight was removed, the kymograph started and the necessary 
electrical connections made, otherwise there were no adjustments 
except in special, cases which are subsequently explained. An 
eight volt tetanizing electrical current was used for stimulating. 
Figure 1. This is a series of curves of the intestine and body 
wall of the earthworm, stimulated in normal sodium chloride 
solution without stretching. Observe the gradual relaxation or 
loss of tonus. After the fortieth stimulus the progressive effects 
of .12 per cent amyl alcohol are shown. 
Figure 2. Typical normal curves are shown in the first few 
contractions followed by a stretch of ten grams for ten minutes 
during which time the kymograph was stopped. Observe the in- 
creased height after stretching. The amount of stimulus re- 
mains constant. 
Figure 3. Curves similar to figure 2 excepting the stretch 
was for twice the length of time. The onset of fatigue came much 
more abruptly. After the thirty-second stimulus, the stimuli were 
made every twenty-five seconds. Observe that the extent of con- 
traction is about one-half of the former. 
Figure 4. Similar to 2 and 3 only here the length of stretch 
is for thirty minutes. The onset and progressive effects of fatigue 
are observed in a slight degree. 
Figure 5. The stretching here continued for two hours but 
the initial contraction afterward is about the same as after the 
ten minute stretch. The onset and progressive effects of fatigue, 
however, are much more marked. 
Figure 6. This series was made as a check on series number 2. 
After the first few contractions a rest of ten minutes occurred 
with no weight applied. The resulting curves when compared 
with those of figure 2 show that the time interval alone is not 
responsible for the increased contractions but, that these were due 
to the stretching. 
Figures 7 and 8. Typical curves where muscles were stretched 
