Forced movements, tropisms, and animal conduct by Loeb Jacques 1859-1924

Author:Loeb, Jacques, 1859-1924 [Loeb, Jacques, 1859-1924]
Language: eng
Format: mobi
Tags: Animal behavior, Tropisms
Publisher: Philadelphia and London, J.B. Lippincott Company

also in all probability of the suggestion that the apex of a positively geotropie root has "brain functions." It is chemical mass action and not "brain functions" which are needed to produce the changes in growth underlying geotropie curvature.

2. As long as animals are in such a position that their plane of symmetry goes through the center of the earth, the position of their eyes and limbs is symmetrical in regard to their plane of symmetry. If, however, we incline the animal we can bring about forced movements and forced changes of position of the same nature as those caused by injury of one side of certain parts of the brain. Thus we have seen that if we cut the left side of the medulla oblongata in a shark, its two eyes are no longer in a symmetrical position but the left eye looks down and the right eye up, when the shark is kept in a normal position. The same change can be brought about in a normal shark by the influence of gravitation. When the shark is kept in a position with its right side inclined downward, the right eye is turned upward, the left eye downward. This has nothing to do with light or vision, since it occurs in the dark just as well as in an illuminated room. The abnormal position of the eyes lasts as long as the animal is kept in this abnormal position. The experiment shows that if the plane of symmetry is no longer vertical, forced positions of the eyes can be produced of the same nature as those produced by one-sided injury of certain parts of the brain.

Just as in the case of one-sided injury to the medulla oblongata the changes in the position of the eyes are accompanied by changes in the position of the pectoral fins, so also when we put a normal shark with one side downward or half downward. 289 If the right side of such

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