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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    the neighborhood of a box containing the animals, those which reacted at all always flew with great violence to the side of the vessel which was turned toward the light. In no case did they fly in the opposite direction. The experiment was unequivocal and could be interpreted in but one way. So far as the contact-irritability is concerned, the animals collected in the four concave vertical edges when kept in a cubical wooden box, which was covered on top with window glass. In this position they assumed an indifferent orienta¬ tion toward the source of light. To make perfectly sure of this fact, I employed the following method: I placed a plate of window glass so close to and parallel with the plane of the floor of the vessel containing the animals that they could just wedge themselves in between the floor and the window glass. The glass plate was entirely exposed to the light. Those animals which by chance came to the edge of the glass plate crept under it, and remained in this position exposed to the light, in contact, however, both above and below with solid bodies. On the next day all the animals were under the glass plate. The animals are therefore forced to bring their bodies in contact with other solid bodies, and it is this (and not the light) which causes them to creep under solid bodies. I placed a ball of paper in the vessel containing the animals ; a part of them crept under the paper and a part into its folds. In nature these butterflies remain in the clefts on the bark of trees or on the ground in mead¬ ows. Forficula auricularia are found in great numbers in verti¬ cal crevices (such, e. g., as the spaces between gate and gate¬ post, in the entrance to gardens). I obtained the animals for my experiments by hanging a cloth of cotton on the top of a small grape vine. The animals collected in the folds of the cloth. These animals in reality move away from the light; that is to say, they are negatively heliotropic; but it
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