Volume 1

Studies in general physiology / by Jacques Loeb.

  • Jacques Loeb
Date:
1905
Catalogue details

Licence: Public Domain Mark

Credit: Studies in general physiology / by Jacques Loeb. Source: Wellcome Collection.

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    of contact-irritability, which, so far as I know, has not yet been recognized. Many insects are compelled to bring their bodies in contact icith the surfaces of solid bodies in a very definite icay. My attention was called to this phenomenon in my experiments on animal geotropism, in which I allowed the animals to move about on geometrically simple bodies bounded by plane surfaces. I noticed that the animals rarely remained on the plane surfaces, but collected about the edges, particularly the vertical ones. It is worthy of note that certain animals always seek the concavity of the angle between the sides of hollow cubes, while others just as con¬ stantly move on the convex side. The caterpillar of Por- thesia chrysorrhoea is an example of the latter type. The other form of this contact-irritability, which leads the ani¬ mals to the concavity of the angles, is very common. The following observations show how this form of irritability might easily be confused with the irritability toward light, and so lead to a misconception of the behavior of the animal toward light. I studied for several weeks a large number of moths of the species Amphipyra. The animals are remarkable in that they are more given to running than to flying. The rapidity of their running movements calls to mind the lively movements of cockroaches and ants. While formerly I had found that all butterflies are positively heliotropic, I observed that Amphipyrse when let loose, did not fly to the window, but to the nearest wall or to the floor, where they ran about nimbly and crept under the first suitable object, like cock¬ roaches. This looked as though the animals fled from the source of light. Yet it could be shown that the animals move toward a source of light, and that the inclination to creep into crevices depends upon the contact-irritability, which was mentioned before. The following experiments always succeeded: In the evening, when a lamp was brought into
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