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IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
begins immediately and is regular as in the case of normal fatigue. 
The relative effects of subjecting muscles to the three lower 
concentrations of ethyl alcohol, namely 17.2, 9.1 and 7.4 vol. per 
cent may best be seen by referring toi typical curves shown respec- 
tively in figures 9, 10 and 11. That an increase in sensitization 
is caused by a decrease in concentration is strikingly apparent here. 
The highest of these three concentrations brings about almost 
immediately the onset of secondary contracture, so that the upper 
margin of the curve drops regularly while the lower margin has 
an accompanying uniform rapid rise, the whole fatigue process 
taking only one and a half minutes to complete. Contrasted to 
this type of curve are those of lower concentrations, where the 
secondary contracture phase is gradually induced and maintained 
at a relatively higher and more uniformly regular level. In both 
of these the time necessary to fatigue is better than two and one- 
half minutes, and the increased responsiveness of the muscle is 
evidenced by the increased height of the recording lever. Once 
initiated, the decline in the secondary relaxation is rapid in all 
three cases which is in marked contrast to curves produced by 
practically all concentrations of propyl or butyl alcohols (see 
Figs. 13 to 19, inclusive) or in the case of strong methyl and ethyl 
alcohols (Figs. 1 and 7). This point, it would seem, is an im- 
portant one in the analysis, since it implies that once the stimu- 
lating effect has run its course, changes are brought about in the 
muscle which in turn now reverse the process and something akin 
to anaesthesia ensues so that the relaxation is induced as rapidly 
as contracture was at first effected. 
Propyl alcohol. — Propyl alcohol in all ranges of concentrations 
except one (3.7 vol. per cent. Fig. 17), gives striking and charac- 
teristic fatigue curves as may be seen by referring to figures 13 
to 17. On being immersed, the muscle immediately begins to 
shorten and this is accompanied by an increased sensitization in 
most of the concentrations tried. This tendency to immediate 
shortening is especially noticeable in strong and saturated solu- 
tions, but is more or less conspicuous in the lower concentrations. 
In strong propyl alcohol there is only a suggestion of the treppe, 
the noticeable phase being the uniform secondary contracture 
which is maintained at a relatively high level (Fig. 13). Satur- 
ated propyl forms a plateau with accompanying contracture (Fig. 
14) with maintained high contracture phase. In strengths 13.3 
and 5.9 vol. per cent the resulting curves are very similar to one 
another as shown in figures 15 and 16, respectively. In the low- 
