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72 the spring and increase the number of shocks. The lever is at once pulled up as far as it will go; but it quivers with with shock, and the curve shows a number of little teeth along its summit (Fig. 36). Make the spring still shorter, and you find the quivering disappears, and the uniform curve of tetanus shows itself, a curve having a long flat summit presenting no teeth (Fig. 37).

The diagrams in Figs. 34 to 37 show curves taken on a slowly moving drum. This experiment demonstrates that tetanus is produced by a fusion or adding together of small contractions. One shock causes one contraction; two shocks, closely following, cause two contractions so far blending into each