184 
IOWA ACADEMY OF SCIENCE Voi,. XXVIII, 1921 
respect it differs decidedly from that of the muscles of the frog 
esophagus. If care is taken to select the proper interval between 
stimuli, say about three minutes, the optimum height of the res- 
ponse is obtained between the fifth and the eighth strokes. Be- 
yond this optimum height there is a steady decline, but this seems 
not be accompanied by marked changes in toxicity as is usually 
the case in voluntary muscles. Figures 24 and 25 are typical re- 
cords of this sort. According to the methods used the variation 
in the amount and duration of the current is assumed to be negli- 
gible. When the fatigue process had run its course, solutions of 
ethyl alcohol of 0.5 volume and 0.25 volume per cent, respectively, 
were added before final stimulation. In each, unmistakable evi- 
dence of a resulting sensitization was apparent which in height 
practically equalled that of optimal activity just referred to. The 
total time necessary to completely fatigue a muscle under these 
conditions was found to vary greatly. In some cases as short a 
time as thirty minutes was sufficient, in others upwards of an hour 
was necessary, and in one exceptional case where the stimulation 
was timed automatically, the tissue retained its responsiveness to 
an incredible degree for several hours. 
The fact that ethyl alcohol administered in certain concentrations 
at the end of the fatigue process altered markedly the responsive- 
ness of the muscle, and other considerations led us to explore the 
qualitative aspect of the effects of this and other alcohols on nor- 
mal responses when they were varied ir\ concentration. Two 
alcohols have so far been tried, but the results obtained are very 
suggestive and compare favorably with certain results obtained 
in the case of the voluntary frog muscle. 
ETHYE ALCOHOL ON FROG MUSCLE 
Several series of experiments were made to test the effect of 
various concentrations of ethyl alcohol on the normal responses 
of the muscles of the frog esophagus, and because of the uniform- 
ity of results in all cases we are convinced that the records cited 
here are typical. The range in concentration in this exploration 
varied from 40 vol. per cent, the highest, to 1.56 vol. per cent, but 
we have selected as illustrative of the modifying influence, strengths 
which range from 12.5 vol. per cent to 1.56 vol. per cent as shown 
in figures 13 to 17, of plate VI, inclusive. About twenty minutes 
after proper mounting in salt solution as described elsewhere, the 
tissue was stimulated to obtain a so-called normal response. After 
