The principles of physiology / by John Augustus Unzer ; and A dissertation on the functions of the nervous system by George Prochaska ; translated and edited by Thomas Laycock.

  • Johann August Unzer
Date:
1851
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Licence: Public Domain Mark

Credit: The principles of physiology / by John Augustus Unzer ; and A dissertation on the functions of the nervous system by George Prochaska ; translated and edited by Thomas Laycock. Source: Wellcome Collection.

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    der the nerves which arise from them independent of the will, and therefore that the heart and intestinal canal are not subject to volition, since they receive their nerves from the ganglia of the intercostal [great sympathetic] nerve. Tissot thinks, that the doubts advanced by Haller, and more fully entered into by Haase, are not at all unanswerable, and are indeed of that cha- racter, that they may be easily made to comport with the doc- trine of Johnston. Pfeffinger has also studiously investigated this theory as to the uses of the ganglia, and approved of it in an elegant dissertation, ‘De Structura Nervorum,’ published in 1782. It is not an improbable conjecture, therefore, that the ganglia found around the nerves act as a sort of gentle ligature or compress, so that the connection between the two extremities of a nerve is so far interrupted, as to prevent the impressions made on the one extremity of the nerve bemg communicated through the ganglion to the other extremity; yet the com- munication of all impressions is apparently not altogether interrupted; for if they be powerful, they appear to pass through the ganglia, and to be transmitted forward along the length of the nerves, but with broken and diminished force. From this it appears to be possible to understand, why the mind has no immediate control over the movements of the heart, stomach, and intestines, namely, because the impressions made by the will on the origins of the nerves do not appear to pass through the ganglia of the intercostal, or great sympathetic nerve, to the parts mentioned, which derive their nerves princi- pally from the intercostal. For this reason it also appears, that although, when the medulla spinalis is irritated, all the muscles are spasmodically contracted, yet the movements of the heart, stomach, and intestines, are scarcely, if at all, accelerated, since the impression of the stimulus applied to the medulla spinalis cannot be transmitted to the intercostal [great sympathetic] nerve through its ganglia. But eminent men testify, that they have seen the motion of the heart increased, and the heart when _at rest excited into action by irritation of the medulla spinalis, as also certainly that from too great emotion,—anger, for example, —the heart’s action is immediately accelerated ; whence it neces- sarily follows, that the impressions of a stimulus from the brain and spinal cerd may pass through the ganglia of the intercostal
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