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

  • Lamarck, Jean Baptiste Pierre Antoine de Monet de.
Date:
1914
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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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    the impression received, penetrates everywhere and passes through any medium, including even the densest bodies : it follows that every animal, belonging to a plan of organisation of which hearing is an essential part, always has some opportunity for the exercise of this organ wherever it may live. Hence among the vertebrates we do not find any that are destitute of the organ of hearing ; and after them, when this same organ has come to an end, it does not subsequently recur in any animal of the posterior classes. It is not so with the organ of sight; for this organ is found to disappear, re-appear and disappear again according to the use that the animal makes of it. In the acephahc molluscs, the great development of the mantle would make their eyes and even their head altogether useless. The permanent disuse of these organs has thus brought about their dis- appearance and extinction, although molluscs belong to a plan of organisation which should comprise them. Lastly, it was part of the plan of organisation of the reptiles, as of other vertebrates, to have four legs in dependence on their skeleton. Snakes ought consequently to have four legs, especially since they are by no means the last order of the reptiles and are farther from the fishes than are the batrachians (frogs, salamanders, etc.). Snakes, however, have adopted the habit of crawling on the ground and hiding in the grass ; so that their body, as a result of continually ■ repeated efforts at elongation for the purpose of passing through I narrow spaces, has acquired a considerable length, quite out of pro- ] portion to its size. Now, legs would have been quite useless to these {animals and consequently unused. Long legs would have interfered tthat the air should penetrate to all places to which the substance producing sound •actually does penetrate. See my memoir On the Substance of Sound, printed at the end of my Hydrogeologie pp. 225, m which I furnished the proofs of this mistake. Since the pubhcation of my memoir, which by the way is seldom cited, great efforts •if i!^^ ^^^^ *° ^^^^ known velocity of the propagation of sound in air taUy wwith the elasticity of the air, which would cause the propagation of its oscillations trto be too slow for the theory. Now, since the au- during oscillation necessarily under- !€oes alternate compressions and dilatations in its parts, recourse has been had to ttthe effects of the caloric squeezed out during the sudden compressions of the air and m the calonc absorbed during the rarefactions of that fluid. By means of these •fettects, quantitatively determined by convenient hypotheses, geometricians now account ttor the velocity with which sound is propagated through air. But this is no answer «o the iact that sound is also propagated through bodies which air can neither traverse Kaor set m motion. These physicists assume forsooth a vibration in the smallest particles of soUd J- O0<iies ; a vibration of very dubious existence, since it can only be propagated through < aomogeneous bodies of equal density, and cannot spread from a dense body to a I f * hypothesis offers no explanation of the well-known d propagated through heterogeneous bodies of very different densities