On the physiological action of the poison of the hydrophidae. Part II, Action on the circulatory, respiratory, and nervous systems / by Leonard Rogers.

  • Leonard Rogers
Date:
[1903]
Catalogue details

Licence: Public Domain Mark

Credit: On the physiological action of the poison of the hydrophidae. Part II, Action on the circulatory, respiratory, and nervous systems / by Leonard Rogers. Source: Wellcome Collection.

    14/20 page 316
    per kilo. weight, with a precisely similar result, including the presence of the negative variation of the current of injury in each sciatic nerve. In two more experiments doses of 5 and 1 milligrammes per kilo. respectively wave pujected without previous ligaturing of a limb, and in both cases stim@lation of the nerves of each limb caused no muscle response, although th®y contracted when directly stimulated. In each case both nerves showed well-marked negative variation of the current of injury, proving that their conducting powers were intact, so that it is clear that the end-plates must have been paralysed. ; Action on the End-Plates of the Phrenic Nerves. The marked action on the motor end-plates of the poison of the Enhydrina once more brings it into line with that of Cobra venom, but on the other hand constitutes a marked difference from Pseudechis venom, which C. J. Martin showed had no such action. He also found that the stimulation of the phrenic nerves still produced normal con- traction of the diaphragm after total cessation of respiration due to the latter poison. In order to ascertain how far the paralysis of respiration produced by Enhydrina venom is due to paralysis of the respiratory centre, and how far, if at all, to poisoning of the motor end-plates of the pee nerves, the following experiments were performed. Cat, weight 33 igloes under chloroform. Tracheal cannula connected with a recorder inserted. Left phrenic nerve exposed in the neck, 34 milligrammes of Enhydrina poison injected into external jugular vein (1 milligramme per kilo.). Phrenic nerve stimulated by an interrupted induced current at intervals ef one minute. Occasional feeble inspirations produced by movement of the chest walls only, continued up to the 24th minute, when they finally ceased. At the 27th minute the final rapid fall of blood pressure to 50 mm. took place. The sciatic nerves were tested at this point, and the right when stimulated with the secondary coil at 30 mm. produced a good muscular response, as did the left with the secondary coil at 274 mm. It appears from this that the phrenic nerve was paralysed completely before any very marked loss of function of the sciatic nerves had taken place. The respirations, however, were very greatly reduced in both frequency and amplitude several minutes before any weakening of the phrenics had occurred, so that the first and most important action of the poison appears to be its effect on the respiratory centre, although the paralysis of the phrenics speedily ensues and is a very important feature of the action of the venom. If a very large dose is given, as in Experiment 5, then the end-plates of the muscles in general are also paralysed at the same time or very soon after the Pulore of the resp aees centre and the phrenics. °
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