Zoological philosophy / by J.B. Lamarck ; translated, with an introduction by Hugh Elliot.

  • Lamarck, Jean Baptiste Pierre Antoine de Monet de.
Date:
1914
Catalogue details

Licence: In copyright

Credit: Zoological philosophy / by J.B. Lamarck ; translated, with an introduction by Hugh Elliot. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    imperceptibly affected by these influences and are preserved and propagated by reproduction. These truths, which are merely effects of the two natural laws stated above, receive in every instance striking confirmation from facts ; for the facts afford a clear indication of nature's procedure in the diversity of her productions. But instead of being contented with generalities which might be considered hypothetical, let us investigate the facts directly, and consider the effects in animals of the use or disuse of their organs on these same organs, in accordance with the habits that each race has been forced to contract. Now I am going to prove that the permanent disuse of any organ first decreases its functional capacity, and then gradually reduces the organ and causes it to disappear or even become extinct, if this disuse lasts for a very long period throughout successive generations of animals of the same race. I shall then show that the habit of using any organ, on the con- trary, in any animal which has not reached the Hmit of the decHne • of its functions, not only perfects and increases the functions of that ( organ, but causes it in addition to take on a size and development ' which imperceptibly alter it; so that in course of time it becomes I very different from the same organ in some other animal which uses iit far less. The permanent disuse of an organ, arising from a change of habits, (causes a gradual shrinkage and ultimately the disappearance and even t extinction of that organ. Since such a proposition could only be accepted on proof, and not con mere authority, let us endeavour to make it clear by citing the chief i known facts which substantiate it. The vertebrates, whose plan of organisation is almost the same tthroughout, though with much variety in their parts, have their jaws aarmed with teeth; some of them, however, whose environment has iimduced the habit of swallowing the objects they feed on without any pprehminary mastication, are so affected that their teeth do not develop IThe teeth then remain hidden in the bony framework of the jaws •^without bemg able to appear outside ; or indeed they actually become 6;extmct down to their last rudiments. In the right-whale, which was supposed to be completely destitute )ot teeth, M. Geoffroy has nevertheless discovered teeth concealed m the ]aws of the foetus of this animal. The professor has moreover discovered m birds the groove in which the teeth should be placed tthough they are no longer to be found there.