On the Causes Which Influence the Direction of the Growth of Roots. [Abstract] [abstract]

Thomas Andrew Knight
1800 Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London  
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more » ... out Early Journal Content at http://about.jstor.org/participate--jstor/individuals/early-journal--content. JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not--for--profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. 398 infusion was injected into the rectum of a dog whose head had been cut off, and whose respiration was kept up by artificial means, the heart continued to act in the same manner as in the experiments which Mr. Brodie lately communicated to the Society, without being sensibly affected by the infusion. The author's trials of the external application of poisons were confined to the essential oil of bitter almonds, the juice of aconite, and the South American poison called Woorara. They all produced the same effects as the two former had done when applied internally, for the heart was observed to contract, as before, long after other symptoms of life had ceased; so that the circulation could be kept up by means of artificial respiration. With respect to the medium through which poisons affect the brain when they are applied to external wounds, the author's experiments were confined to the woorara. And he endeavoured to determine whether the influence was conveyed by the nerves, or whether the poison itself entered the circulation, either by the absorbents, or through the divided veins. By dividing the nerves of a part, the efficacy of the woorara did not appear diminished, neither did tying up the thoracic duct in any degree interfere with its action. But when a ligature was applied round the leg of a rabbit, so as not to include the sciatic nerve, the rabbit was not in the least affected by the woorara. The author consequently infers that the woorara acts upon the brain by passing into its substance through the divided vessels of the part to which it is applied. Since the circulation of an animal could be kept up by an artificial respiration, after the brain had been even completely removed, Mr. Brodie conceived it possible that the functions of the brain might be 'found to recover from temporary suspension if the circulation were continued for a time by artificial respiration, and that thus the life of the animal might be preserved. After two experiments, which were not attended with complete success, a third was made upon a rabbit, by applying distilled oil of almonds to a wound in the side. In five minutes it ceased to breathe, and was apparently dead; but by means of artificial respiration continued for sixteen minutes, it was completely restored to life; and on the following day appeared not to have suffered from the experiment.
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