General physiology; an outline of the science of life . ic phenomena. 4. Thermotaxis Heat, like light, can be employed very easily for unilateralstimulation, since, whether transmitted by conduction or radiation,it always decreases with the distance from its source, and hence G g 2 452 GENERAL PHYSIOLOGY differences of temperature always exist at two different points inthe medium in the same direction from the source. The first observation of thermotactic properties was made byStahl (84) in plasmodia of Aethalium septicum. He placed twobeakers side by side, one of which was filled with water a
General physiology; an outline of the science of life . ic phenomena. 4. Thermotaxis Heat, like light, can be employed very easily for unilateralstimulation, since, whether transmitted by conduction or radiation,it always decreases with the distance from its source, and hence G g 2 452 GENERAL PHYSIOLOGY differences of temperature always exist at two different points inthe medium in the same direction from the source. The first observation of thermotactic properties was made byStahl (84) in plasmodia of Aethalium septicum. He placed twobeakers side by side, one of which was filled with water at atemperature of 7°, the other with water at 30°; he then laid overtheir edges a strip of filter-paper, upon which the plasmodium hadspread itself out, in such a manner that one end of the plasmodiumdipped into the colder, the other into the warmer water. The pro-toplasm of the plasmodial network at once began to stream out ofthe former toward the latter, although before the experiment theopposite direction had been followed. The whole protoplasmic. Fig. 226.—Negative thermotaxis of Amoeba. I, A drop of water containing many amcebae lies upona large cover-glass. The cover-glass lies upon a black ground, which has in the middle a sharp,square opening. By shoving the cover-glass an amoeba can be so placed that it creeps overthe edge of the hole, //, A. If concentrated sunlight is then let through the opening from themirror of the microscope, the amoeba creeps back immediately into the cool darkness, //, arrows indicate the direction of the movement. mass finally passed over to the warm water. This is a caseof positive thermotaxis. Negative thermotaxis can be observed in Amoeba,} when atemperature of at least 35°C. is allowed to act upon one part ofthe body while the rest of the protoplasm is at a lower can hardly be accomplished by means of conducted heat and the following arrangement should be em-ployed. A large drop of water, containi
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Keywords: ., bookcentury1800, bookdecade1890, bookidgen, booksubjectphysiology
