Mechanism of reflex nervous action in normal respiration / by Austin Flint, jr. ; [phonographically reported by Geo. W. Wells].

  • Flint, Austin, 1836-1915.
Date:
1874
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Licence: Public Domain Mark

Credit: Mechanism of reflex nervous action in normal respiration / by Austin Flint, jr. ; [phonographically reported by Geo. W. Wells]. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    clusively, to the mucous membrane of the pulmonary struct- ure. These branches communicate with the sympathetic; but, according to Sappey, they do not go to the walls of the blood- vessels, being distributed to the mucous membrane lining the air-vesicles. So much for the distribution, in general terms, of those branches of the pneumogastrics which go to the lungs; and this distribution being so extensive, you can readily see that we can hardly discuss the reflex nervous action in respiration, without taking the action of these nerves into consideration. The pnemnogastric is originally an exclusively sensory nerve. Experiments are somewhat obscure upon this point, on ac- count of the difficulty in irritating the original roots of the pneumogastrics, without involving filaments of other nerves; still, the careful experiments of Longet showed that when the spinal cord of animals is opened, and the roots of the pneu- mogastrics are carefully isolated and stimulated, no movements follow their irritation. This shows that the original filaments of the pnemnogastric are not motor. But the pnemnogastric, as it emerges from the cranial cavity, receives numerous com- municating motor filaments, and thus, in its course, it is a mixed nerve. Following out the filaments that are distributed to the respiratory apparatus, we find that the filaments from the superior laryngeal going to the crico-thyroid muscle, are almost exclusively motor ; the motor filaments of the recur- rents go to the intrinsic muscles of the larynx, whereas the fine pulmonary branches are distributed to the mucous mem- brane. Therefore, excluding the movements of the larynx, the action of the pnemnogastric in the reflex phenomena of respiration, theoretically, would be that of a sensory nerve, conveying to the respiratory nervous centre an impression, or sensation, which gives rise to the movements of respiration. It both pneumogastrics, however, be divided, we find that the respiratory movements are very much diminished in fre- quency ; and I have in my mind an experiment in which they were reduced from twenty-four to four or six in a minute; vet, they still continue; and this simple experiment, so often performed as a class-demonstration, is a denial of the propo- rtion that the pnemnogastric nerves are the only nerves for