_Effect of continuous stimulation: Experiment 75._--The effect of continuous stimulation of increasing intensity will be seen in the record (Fig. 73), taken on a moving plate. On application of continuous stimulus of increasing intensity an increased flexure was produced in the curve, which denoted greater retardation in the rate of growth. When the intensity of stimulus was raised to 3 units, there was induced an actual contraction. CONTINUITY BETWEEN INCIPIENT AND ACTUAL CONTRACTION. It will thus be seen, that external stimulus of electric shock induces a reaction which is of opposite sign to the normal growth elongation or expansion. We may conveniently describe this effect as ‘incipient’ contraction; for under increasing intensity of stimulus, the contractile reaction, opposing growth elongation, becomes more and more pronounced; at an intermediate stage this results in an arrest of growth; at the further stage, it culminates in an actual shortening of the organ. There is no break of continuity in all these stages. I shall, therefore, use the term ‘contraction’ in a wider sense, including the ‘incipient’ which finds expression in a retardation of growth. In Table XVI is given the results of certain typical experiments on the effect of stimulus of increasing intensity and duration. TABLE XVI.--EFFECT OF INTENSITY AND DURATION OF ELECTRIC STIMULUS ON GROWTH. +--------------------------+------------+------------------+ | Duration of Application. | Intensity. | Rate of growth. | +--------------------------+------------+------------------+ | |Normal |0.35 µ per second.| |5 seconds |1 unit |0.22 µ " " | | " |2 units |0.07 µ " " | | " |4 " |Arrest of growth. | +--------------------------+------------+------------------+ | |Normal |0.30 µ per second.| |Continuous stimulation |0.5 unit |0.20 µ " " | | " " |1 " |0.09 µ " " | | " " |3 " |Contraction. | +--------------------------+------------+------------------+