Pamphlets on Protozoology (Kofoid Collection)


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Página 52 - ... to make clear to ourselves what the essential function is which it performs. As I have found no description or statement of that function which satisfied me, I have ventured, perhaps rashly, to draw up the following new description: The function of consciousness is to dislocate in time the reactions from sensations. In one sense this may be called a definition of consciousness, but inasmuch as it does not tell what consciousness is, but only what it does, we have not a true definition, but a...
Página 25 - The animal bends to one side ... It thus as a rule avoids the cloud of particles, unless the latter is very large. This simple method of reaction turns out to be more effective in getting rid of stimuli of all sorts than might be expected. If the first reaction is not successful, it is usually repeated one or more times...
Página 631 - Amceba in locomotion. The experiments may best be performed as follows : A piece of smooth cardboard, such as the Bristol board used for drawing, is placed in the bottom of a flat dish and on a certain spot on the cardboard is placed a drop of water. The whole is then covered with bone oil. This soaks into the cardboard, except where the latter is protected by the drop of water.
Página 53 - dislocate' reactions, in time — that is, to delay reactions to a given stimulus. To this, it has reasonably been objected that " unconscious mechanisms could be constructed, and indeed do exist in which there is a dislocation in 'time between the action of an outer agent — and the reaction of the machine*.
Página 42 - ... (1897, page 108) gives an example drawn from the behavior of one of the organisms at present under consideration. "When an organism has been stimulated by contact for some time, it at last becomes changed, so that it no longer responds as it did at first. Thus, Dr. WE Castle informs me that he has seen a colony of Stentors, in an aquarium, being constantly struck by Tubifex waving back and forth, yet the Stentors did not contract as they usually do when struck.
Página 196 - ... all or revolves only very slowly. In consequence of this it is easy to determine the relation of the direction of turning to the differentiations of the body. The reaction to heat and cold is in essentials identical with that of O. fallax, and this reaction is repeated till the animals are carried into a region where the temperature is not such as to cause the reaction. Those that are carried into such a region will of course be swimming away from the stimulating region ; hence, in a large number...
Página 336 - ... localized stimuli, acting on one side or one end of the animal, have the same effect as stimuli acting upon the entire surface of the body at once. The direction in which the Paramecium turns after a stimulus is determined by internal factors, and is expressible in terms of the animal's structure ; it has no relation to the position of the source of stimulus. The absolute direction in which the animal turns is a matter of chance ; if it does not carry the animal away from the obstruction the...
Página 49 - ... (5) Finally, if all these reactions remain ineffective, the animal not only gives up completely its usual activities, but puts in operation another set, having a much more radical effect in separating the animal from the stimulating agent. It abandons its tube, swims away, and forms another one in a situation where the stimulus does not act upon it. The behavior of Stentor under the conditions given is evidently a special form of the method of the selection of certain conditions through varied...
Página 46 - The impression made on the observer is very much as if the organism were at first trying to escape a danger, and later merely trying to avoid an annoyance.

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