Selective Action of Strychnin and Nicotin on a Single Cell

Abstract

(1) The animals show a tendency to collect in small groups soon after strychnin or nicotin is applied. (2) Strychnin acts specifically on the body of the animal, selecting and depressing especially the locomotor organs on the right and at the anterior end of the cell. The posterior cilia and the still active cilia on the left then turn the animal in the counter-clockwise direction, with the posterior in advance of the anterior end. Eventually, all the cilia are paralyzed. The animals remain on their ventral surfaces. (3) Nicotin also acts selectively on the body of the animal, depressing especially the posterior cilia and those on the left side of the cell. The only cilia on the right which are not depressed early are the long ones at the mouth of the oral groove. As long as an animal remains on its ventral surface, these cilia of the groove and the still active ones at the extreme anterior end turn the cell in the counter-clockwise direction with the anterior in advance of the posterior end. (4) Some time after nicotin is applied the animals cease turning in the counter-clockwise direction, respond irregularly for a short time, and eventually go forward turning over and over as they go. This turning of an animal on its long axis is due to the action of the cilia at the mouth of the groove which normally tend to cause the organism to rotate in this way, but which ordinarily fail to cause the rotation because other cilia (which are now depressed) overcome the effects of the groove cilia and keep the animal on its ventral surface. It is only after certain cilia, presumably those on the left side, are paralyzed that the cilia of the groove can turn the animal as they normally tend to do. The turning over and over as the poisoned animals go forward ceases finally, as the cilia of the groove become depressed, and then the great majority of the animals come to rest on their dorsal surfaces. After this the animals turn again in the spiral fashion in the counter-clockwise direction with respect to their dorsal surfaces. All the cilia are eventually paralyzed.