. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 336 MOTION IN ANIMALS AND PLANTS. known excitatory responses—all electrical changes which are concomi- tants of action—may be compared Avith one of these types. (jfjf^gQ l^—Response to a continuous stimulation. A difference of potential comes into existence at the contacts at the time t^ and persists long enough to produce its full effect on the column. (Diagram 1.) Case 2.—Series of short continuous stimulations. The column moves in altern
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 336 MOTION IN ANIMALS AND PLANTS. known excitatory responses—all electrical changes which are concomi- tants of action—may be compared Avith one of these types. (jfjf^gQ l^—Response to a continuous stimulation. A difference of potential comes into existence at the contacts at the time t^ and persists long enough to produce its full effect on the column. (Diagram 1.) Case 2.—Series of short continuous stimulations. The column moves in alternately opposite directions. (Diagram 2.) Case 3.—Response to a single instantaneous stimulation. A differ- ence of potential comes into existence abruptly, and subsides abruptly at first, afterwards less rapidly. (P' in diagram 4.) Now, I have found that in the study of my experimental results it is of great advantage to proceed a priori. Let us assume that there are three types of stimulation, and that each has its form of response. We can best begin by inquiring to which of these three forms the. 24 26 observed variation belongs, and then determine in what respects it conforms with, or differs from, the type. In the diagrams, I have shown the types of photographic curves which correspond to the three forms of response to stimulation I have indicated. The faint lines represent photographic curves; the strong, variations of potential difference. In each diagram the strong and the faint lines have been drawn in their true mathematical relation to each other, i. e., so that the vertical distance apart of strong from faint is everywhere proportional to the gradient or slope of the photographic curve, the proportion being such that if the electro-motive force of the current acting on the electrometer varied according to the strong line, the movement of the head of the mercury column would be expressed by the faint line. We shall see as we proceed that one or other of the t
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