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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    were also found at tlie window side of the vessel. A second small collection occurred in the middle of the vessel, while the room side of the vessel was entirely vacated. The ani¬ mals usually did not become positively heliotropic until shortly before they became motionless. This explains why the conversion of the negatively lieliotropic into the posi¬ tively heliotropic animals through lack of oxygen cannot be obtained with the precision and elegance with which the change can be obtained by cooling. In the latter case the animals retain their full power of movement; in the former the transformation does not occur until the animals have suffered from lack of oxygen. But even then the phenome¬ non is so striking that it might be used as a demonstration experiment. I have repeated the experiment eight times with the same result. At first it seemed to me as if the negatively heliotropic Copepods died more rapidly in the absence of oxygen than those which were positively helio¬ tropic from the beginning. This finding, however, was not borne out in every case. When the experiment was interrupted early, at a time when the animals first began to become positively heliotropic, and air was then admitted, the Copepods which had become positively heliotropic again became negatively lieliotropic. The remarkable effects, which we have described here, of lack of oxygen on the sense of heliotropism, are, of course, not confined to Copepods. I made similar experiments upon the negatively lieliotropic marine Isopods, the majority of which also become positively lieliotropic in less than two hours when oxygen is withdrawn. These experiments will be continued. We see, therefore, that lack of oxygen has the same effect upon the sense of heliotropism as cooling or increas¬ ing the concentration of the sea-water. Araki has shown that by cooling the chemical effects of lack of oxygen can
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