Page:Researches on Irritability of Plants.djvu/55

32 contractile effect in the more sluggish smooth muscles. Vegetal protoplasm also is commonly regarded as little capable of excitation by these shocks, behaving in this respect like the sluggish smooth muscles amongst animal tissues. Again, while the break-induction-shock of higher intensity and shorter duration is more effective in exciting the quickly reacting skeletal muscle, in the case of the sluggish smooth muscle it is the make-shock of low intensity and long duration that proves more efficacious. That

the inference commonly made about the reaction of vegetal protoplasm to single induction-shocks is not of universal application, is strikingly seen in the response of pulvinus of Mimosa. Here, so far at least as single induction-shocks are concerned, its reaction appears more analogous to that of skeletal than of smooth muscle; as a position of the secondary in relation to the primary can be found in which, while a single make-shock is ineffective, a single break-shock is quite efficient. In order to render the make-shock effective, the secondary has here to be pushed in nearer to the primary, thus increasing the intensity of the shock. A pair of records will be given in a later chapter