Principles of human physiology / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1869
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Licence: Public Domain Mark

Credit: Principles of human physiology / by William B. Carpenter. 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.

    137/1110 (page 103)
    observations of MM. Vulpian* and Jolyet. From a careful examination of the actions of deglutition, and of the influence of various nerves upon them, Dr. Eeid drew the following conclusions :—The excitor impressions are conveyed to the Medulla Oblongata chiefly through the Glosso- pharyngeal, but also along the branches of the Fifth pair distributed upon the fauces, and probably along the superior laryngeal branches of the Pneumogastric distributed upon the pharynx. The motor influence passes chiefly along the pharyngeal branches of the Pneumogastric, which are probably originally derived from the Spinal Accessory; along the branches of the Hypoglossal, distributed to the muscles of the tongue, and to the sterno-hyoid, sterno-thyroid, and thyro-hyoid muscles ; along the motor filaments of the Eecurrent laryngeals ; through some of the branches of the Fifth, supplying the elevator muscles of the lower jaw; along the branches of the Facial, ramifying upon the digas- tric and stylo-hyoid muscles and upon those of the lower part of the face ; and probably along some of the branches of the Cervical plexus, which unite themselves to the descendens noni. It was further observed by Dr. Eeid, that the stylo-pharyngeus muscle is usually thrown into contraction, when the roots of the Glosso-pharyngeal nerve are irritated; and as this has been also noticed by Mayo, Volkmann, and others, we are probably to consider the Glosso-pharyngeal a motor nerve, in so far as that muscle is concerned.] 87. When the food has been propelled downwards by the Pharyngeal muscles, so far as their action extends, its further progress through the (Esophagus is effected by a kind of peristaltic contraction of the muscular coat of the tube itself. This movement is not, however, due only to the direct stimulus of the muscular fibre by the pressure of the food, as it seems to be in the lower part of the alimentary canal; for Dr. J. Eeid aas found, by repeated experiment, that the continuity of the oesophageal branches of the Pneumogastric with the Medulla Oblongata is necessary for the rapid propulsion of the food; so that it can scarcely be doubted, -hat an impression made upon the mucous surface of the oesophagus, con- veyed by the afferent fibres of these nerves to their ganglionic centre, and reflected downwards along the motor fibres, is the real cause of the muscular contraction. If the Pneumogastric be divided in the rabbit, 3n each side, above the oesophageal plexus, but below the pharyngeal branches, and the animal be then fed, it is found that the food is delayed n the oesophagus, from spasmodic contraction of the cardiac sphincter, which becomes greatly distended. Further, if the lower extremity of ;ne Pneumogastric be irritated, distinct contractions are seen in the Esophageal tube, proceeding from above downwards, and extending over ;he cardiac extremity of the stomach.—We have here, then, a distinct >ase of reflex action, without sensation, occurring as one of the regular issociated movements in the natural condition of the animal body; and it s very interesting to find this following upon a reflex action ivith sensa- tion (that of the pharynx), and preceding a movement which is but ihghtly connected with the Spinal Cord (that of the lower part of the * Revue de Cours Scientifiques, 1866, t. iii. p. 754. t Op. cit., pp. 258-260.—It seems not improbable that the discrepant results ob- •aineu by different experimenters on this point, are partly to be explained by differences n the distribution of the nerves in the several species of animals operated-on.