A text-book of human physiology / by Dr. Robert Tigerstedt ... tr. from the 3d German ed. and edited by John R. Murlin ... with an introduction to the English ed., by Professor Graham Lusk.

  • Robert Tigerstedt
Date:
1906
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of human physiology / by Dr. Robert Tigerstedt ... tr. from the 3d German ed. and edited by John R. Murlin ... with an introduction to the English ed., by Professor Graham Lusk. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    these may l)e regarded as to a certain extent chemotactic. Thus according to the thorough analysis of Bethe, a whole order of complicated habits of the ants might be explained as chemotactic reactions, and in the bees several habits are undoubtedly of this origin. Jennings has shown that there is nothing specifically directive about the chemotactic effects of chemical substances on Infusoria and Bacteria. If, for example, Bacillum volutans be placed in a preparation with a green alga< they are uniformly distributed at first throughout the preparation. When the alga be- gins to give off oxygen and the bacilli come by chance into this zone rich in O,, they swim through it to the opposite side, turn and swim again to the border, and so on incessantly, but they do not adhere to any definite orientation with respect to the middle point of the oxygen zone. [The behavior of an Infusorian under chemical stimulation may be illus- trated, according to Jennings, as follows: the usual motor response of a Paramce- cium to any kind of an obstruction is to reverse its cilia and swim backward, then turn toward the side containing the peristome and swim forward again (Fig. 32). When in its wanderings the Paramecium enters a drop of dilute acid, the chemical change of the medium does not cause the reaction, but whenever the organism attempts to leave the drop the chemical change experienced consti- tutes a stimulus which evokes the usual motor response, and the organism remains entrapped. Coming in contact with an alkali produces the same response and the organism turns so as to avoid the substance. The result is that the organ- isms collect in dilute acids, including carbon dioxide (positive chemotaxis), and refuse to do so in alkalies (negative chemotaxis). But the acid can scarcely be :$^- Fig. 32.—Motor re.spon.se in Paramaecium, after Jennings, a-j, succes.sive positions after meet- ing an obstruction, .4. said to attract the organisms in any proper sense of the term, nor the alkali to repel them. They remain in the acids doubtless because the.se substances are favorable' to their life processes and avoid the alkalies because the latter are harmful.—Ed.] ' Jennings recognizes this selection by random movements of conditions not interfering with the physiologieal processes as a fixed principle of behavior, not only in the Bacteria and Lifusoria but in higher animals as well.—Ed.
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