Forced Movements, Tropisms, and Animal Conduct

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J.B. Lippincott, 1918 - Science - 209 pages
Experimentelle Physiology.
 

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Page 161 - The butterfly lays its eggs upon a shrub. The larvae hatch late in the fall and hibernate in a nest on the shrub, as a rule not far from the ground. As soon as the temperature reaches a certain height, they leave the nest; under natural conditions, this happens in the spring when the first leaves have begun to form on the shrub. (The larvae can, however, be induced to leave the nest at any time in the winter, provided the temperature is raised sufficiently.) After leaving the nest they crawl directly...
Page 5 - This situation, which exists in all the sciences, has induced English authors to issue series of monographs in biochemistry, physiology and physics. A number of American biologists have decided to provide the same opportunity for the study of experimental biology. Biology, which not long ago was purely descriptive and speculative, has begun to adopt the methods of the exact sciences, recognizing that for permanent progress not only experiments are required but that the experiments should be of a...
Page 162 - Their positive heliotropism has disappeared and the animal after having eaten can creep in any direction. The restlessness which accompanies the condition of starvation makes the animal leave the top of the branches and creep downward — which is the only direction open to it — where it finds new young leaves on which it can feed. The wonderful hereditary instinct upon which the life of the animal depends is its positive heliotropism in the unfed condition and the loss of this heliotropism after...
Page 161 - As soon as the temperature reaches a certain height, they leave the nest; under natural conditions, this happens in the spring when the first leaves have begun to form on the shrub. (The larvae can, however, be induced to leave the nest at any time in the winter provided the temperature is raised sufficiently.) After leaving the nest, they crawl directly upward on the shrub where they find the leaves on which they feed. If the caterpillars should move down the shrub, they would starve, but this they...
Page 23 - It would, therefore, be a misconception to speak of tropism as of reflexes, since tropisms are reactions of the organism as a whole, while reflexes are reactions of isolated segments.
Page 90 - ... constant and one intermittent source of light and comparing the results with those obtained by two constant lights we can test the validity of the Bunsen-Roscoe law. The method of the experiments was as follows: abed (fig. 1) is a square dish of optical glass with blackened bottom and containing a layer of sea water. A and B are two lights, the intensity of which is determined by a Lummer-Brodhun contrast photometer. In front of each light is a screen with a round hole permitting a beam of light...
Page 92 - ... observed values are slightly smaller but practically identical \\ \ with the values obtained when the two lights are constant. The deviation is probably due to the fact that the photochemical efficiency of an intermittent light is a trifle less than that calculated on the basis of the Bunsen-Roscoe law.9 We carried out some experiments with a sector of 144°. When the efficiency of both lights was equal on the assumption of the validity of the Bunsen-Roscoe law a was found to be 44.9° (instead...
Page 161 - The caterpillars upon waking from their winter sleep are violently positively heliotropic, and it is this heliotropism which makes the animals move upward. At the top of the branch they come in contact with a growing bud and chemical and tactile influences set the mandibles of the young caterpillar into activity. If we put these caterpillars into closed test tubes which lie with their longitudinal axes at right angles to the window they will all migrate to the window end where they will stay and...
Page 22 - Physiologists have long been in the habit of studying not the reactions of the whole organism but the reactions of isolated segments (the so-called reflexes). While it may seem justifiable to construct the reactions of the organism as a whole from the individual reflexes, such an attempt is in reality doomed to failure, since reactions produced in an isolated element cannot be counted upon to occur when the same element is part of the whole, on account of the mutual inhibitions which the different...
Page 58 - ... impression of trying to climb up into the air. The wings are frequently somewhat spread and the animal may push itself up and back until poised vertically on the tips of the wings and abdomen. The tendency to fly is very pronounced in this condition and upon the slightest disturbance the fly soars upward and backward, striking the top of a confining glass dish or completing a circle by "looping the loop" backward. If it falls upon its back it rights itself by turning a backward somersault. Unequal...

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